ORCID Profile
0000-0001-6950-1821
Current Organisations
Aston University
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Northwest A and F University
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Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 04-2006
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 05-2008
Publisher: Wiley
Date: 05-03-2020
DOI: 10.1002/LDR.3577
Abstract: The cover‐management factor (C‐factor) is used in the revised universal soil loss equation to represent the effect of vegetation cover and its management practices on hillslope erosion. Remote sensing has been widely used to estimate vegetation cover and the C‐factor, but most previous studies only used the photosynthetic vegetation (PV) or green vegetation indices (VI, e.g., normalized difference VI) for estimating the C‐factor and the important non‐PV (NPV) component was often ignored. In this study, we developed a new technique to estimate monthly time‐series C‐factor using the fractional vegetation cover (FVC) including both PV and NPV, and weighted by monthly rainfall erosivity ratio. The monthly FVC was derived from the moderate resolution imaging spectroradiometer and LANDSAT data with field validation. We conducted the case‐study over China's Loess Plateau and analysed the spatiotemporal variations of FVC and the C‐factor and their impacts on erosion over the Plateau. Our study reveals a significant increase in total vegetation cover (TC) from 56 to 76.8%, with a mean of 71.2%, resulting in about 20% decrease in the C‐factor and erosion risk during the 17‐year period. Our method has an advantage in estimating the C‐factor from TC at a monthly scale providing a basis for continuously and consistently monitoring of vegetation cover, erosion risk and climate impacts.
Publisher: MDPI AG
Date: 16-11-2021
DOI: 10.3390/APP112210821
Abstract: Solar-induced chlorophyll fluorescence (SIF) observations from space have shown close relationships with terrestrial photosynthesis rates. SIF originates from the light reactions of photosynthesis, whereas carbon fixation takes place during the dark reactions of photosynthesis. Questions remain regarding whether SIF is able to track changes in the efficiency of the dark reactions in photosynthesis. Using concurrent measurements of leaf-scale gas exchange, pulse litude-modulated (PAM) fluorescence, and fluorescence spectral radiances, we found that both far-red fluorescence radiances and PAM fluorescence yields responded rapidly to changes in photosynthetic carbon assimilation due to changes in environmental factors or induced stomatal closure under constant light conditions. Uncertainties in outgoing and incoming irradiance mismatch for SIF measurements may very likely obscure the contributions of the dark reactions, thereby causing the inconsistent findings previously reported, which were no change in far-red SIF and PAM fluorescence yields after clear reductions in the photosynthetic carbon assimilation efficiency of dark reactions. Our results confirm that high-quality SIF measurements have the potential to provide insights into the dark reactions of photosynthesis. This study is particularly relevant for better interpreting satellite SIF observations that are obtained under roughly constant overpass times and relatively stable light intensities.
Publisher: Wiley
Date: 27-12-2019
DOI: 10.1002/LDR.3451
Publisher: Wiley
Date: 02-09-2020
DOI: 10.1002/JOC.6266
Publisher: Society of Agricultural Meteorology of Japan
Date: 2018
Publisher: Informa UK Limited
Date: 05-2007
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/BT12051
Abstract: The radial growth and recruitment patterns of trees in subalpine areas are subject to the influence of changing environmental conditions associated with changes in elevation. To investigate responses of fir radial growth and recruitment to climate factors at different elevations, tree-ring width chronologies and age structures of Abies faxoniana were developed from five s ling sites at ~2800–3300 m elevation on the north-western and south-eastern aspects in the Wanglang Natural Reserve on the eastern edge of Tibetan Plateau. Statistical characteristics of the chronologies indicated that expressed population signal and signal-to-noise ratio increased with increasing elevation in the north-western aspect the reverse was observed on the south-eastern aspect. Correlation analysis between chronologies and climate variables showed that fir radial growth was negatively correlated with previous growing season mean temperatures and was positively correlated with January precipitation in all plots. The amount of precipitation in the growing season (June and July) greatly influenced radial growth in the two lower sites of both the aspects. The three plots on the north-western aspect were characterised by significant rates of tree recruitment in the past five decades. There were multi-decadal periods of heightened recruitment over the past three centuries in the two south-eastern plots. Widespread disturbances after 1920s were not observed in any plots and the infrequent small-scale disturbances that occurred were not the main factors influencing recent recruitment in any plots. Correlation analysis between recruitment residuals and climate variables showed that fir seedling recruitment in the north-western aspect plots was mainly controlled by spring–summer temperatures. But recruitment was greatly restricted by competition with dense bamboos and other tree species in the south-eastern aspect. Overall, previous August mean temperature and January precipitation were the dominant factors determining fir radial growth in all plots, and recruitment was sensitive to spring–summer temperatures in the plots with sparse bamboo cover.
Publisher: Wiley
Date: 11-02-2021
DOI: 10.1111/AOS.14782
Abstract: To explore the presence of microvascular endothelial dysfunction as a measure for early cardiovascular disease in in iduals diagnosed with dry eye disease (DED) as compared to age‐matched normal controls. Systemic blood pressure, Body Mass Index, intraocular pressure, blood levels of glucose (GLUC), triglycerides, cholesterol (CHOL), high‐density lipoprotein cholesterol (HDL‐C), and low‐density lipoprotein cholesterol (LDL‐C)] as well as retinal and peripheral microvascular function were assessed in twenty‐five 35–50 year olds with diagnosed with DEDa (using the TFOS DEWS II criteria) and 25 age and sex‐matched controls. After controlling all the influential covariates, in iduals diagnosed with DED exhibited significant lower retinal artery baseline (p = 0.027), artery maximum diameter (p = 0.027), minimum constriction (p = 0.039) and dilation litude (p = 0.029) than controls. In addition, the time to reach the vein maximum diameter was significantly longer in the DED patients than in normal controls (p = 0.0052). Only in in iduals diagnosed with DED, artery maximum constriction correlated statistically significantly and positively with HDL‐C blood levels (p = 0.006). Similarly, artery slope AD correlated positively with T‐CHOL and LDL‐C (p = 0.006 & 0.011 respectively). Additionally, artery baseline diameter and maximum constriction were significantly and negatively correlated to T‐CHOL/HDL‐C ratio (p = 0.032 and p = 0.013 respectively) in DED in iduals only. In iduals with positive diagnosis of DED exhibit abnormal retinal microvascular function and possible higher risk for CVD.
Publisher: Elsevier BV
Date: 04-0005
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 06-2017
Publisher: Elsevier BV
Date: 04-2006
Publisher: Wiley
Date: 28-02-2009
DOI: 10.1002/HYP.7166
Publisher: Springer Science and Business Media LLC
Date: 20-01-2016
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 30-03-2021
Publisher: Wiley
Date: 28-02-2013
DOI: 10.1002/ECO.1258
Publisher: Elsevier BV
Date: 03-2006
Publisher: MDPI AG
Date: 12-08-2020
DOI: 10.3390/W12082268
Abstract: The magnitude and spatiotemporal distribution of precipitation are the main drivers of hydrologic and agricultural processes in soil moisture, runoff generation, soil erosion, vegetation growth and agriculture activities on the Loess Plateau (LP). This study detects the spatiotemporal variations of in idual rainfall events during a rainy season (RS) from May to September based on the hourly precipitation data measured at 87 stations on the LP from 1983 to 2012. The incidence and contribution rates were calculated for all classes of rainfall duration and intensity to identify the dominant contribution to the rainfall amount and frequency variations. The trend rates of regional mean annual total rainfall amount (ATR) and annual mean rainfall intensity (ARI) were 0.43 mm/year and 0.002 mm/h/year in the RS for 1983–2012, respectively. However, the regional mean annual total rainfall frequency (ARF) and rainfall events (ATE) were −0.27 h/year and −0.11 times/year, respectively. In terms of spatial patterns, an increase in ATR appeared in most areas except for the southwest, while the ARI increased throughout the study region, with particularly higher values in the northwest and southeast. Areas of decreasing ARF occurred mainly in the northwest and central south of the LP, while ATE was found in most areas except for the northeast. Short-duration (≤6 h) and light rainfall events occurred mostly on the LP, accounting for 69.89% and 72.48% of total rainfall events, respectively. Long-duration (≥7 h) and moderate rainfall events contributed to the total rainfall amount by 70.64% and 66.73% of the total rainfall amount, respectively. Rainfall frequency contributed the most to the variations of rainfall amount for light and moderate rainfall events, while rainfall intensity played an important role in heavy rainfall and rainstorms. The variation in rainfall frequency for moderate rainfall, heavy rainfall, and rainstorms is mainly affected by rainfall duration, while rainfall event was identified as a critical factor for light rainfall. The characteristics in rainfall variations on the Loess Plateau revealed in this study can provide useful information for sustainable water resources management and plans.
Publisher: Springer Science and Business Media LLC
Date: 08-03-2017
DOI: 10.1038/SREP44046
Abstract: Terrestrial gross primary production (GPP) plays a vital role in offsetting anthropogenic CO 2 emission and regulating global carbon cycle. Various remote sensing approaches for estimating GPP have attracted considerable scientific attentions, yet their robustness and uncertainties remain unclear. Here we evaluate the performance of the “temperature and greenness” (TG) model, a representative remote sensing model in estimating GPP, using the global FLUXNET GPP based on parameter sensitive analysis and optimization strategies. The results show that the minimum (x n ) and optimum (x o ) temperatures for photosynthesis are sensitive parameters but maximum temperature (x m ) not. Optimized x n and x o differ largely from their defaults for more than half of 12 plant functional types (PFTs). Parameter optimization significantly improves the TG’s performance in forest ecosystems where temperature or solar radiation has significant contribution to GPP. For water-limited ecosystems where GPP are strongly dependent of EVI and EVI are sensitive to precipitation, parameter optimization has limited effects. These results imply that the TG model, and most likely for other kind of GPP models using same methodology, can’t be significantly improved for all PFTs through parameter optimization only, and other key climatic variables should be incorporated into the model for better predicting terrestrial ecosystem GPP.
Publisher: Elsevier BV
Date: 12-2019
Publisher: Elsevier BV
Date: 11-2011
Publisher: Springer Science and Business Media LLC
Date: 15-03-2007
Publisher: Springer Science and Business Media LLC
Date: 30-04-2020
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 04-2016
Publisher: Institute of Experimental Botany
Date: 10-03-2020
DOI: 10.32615/PS.2019.134
Publisher: Elsevier BV
Date: 11-2014
Publisher: American Geophysical Union (AGU)
Date: 04-12-2020
DOI: 10.1029/2020JD033380
Abstract: Changing evapotranspiration (ET) will impact freshwater availability, knowledge of which is a critical prerequisite for policy development related to water resources management in an evolving climate, especially for water‐limited regions. However, the socio‐economic effects are not considered due to the lack of detailed information about this. Here we used a well‐validated remote sensing model and multiple socio‐economic factors to investigate the driving factors of ET changes over the Loess Plateau during 1982–2012. Results showed that the modeled annual ET significantly increased by ~2 mm yr −2 during this period ( p 0.001), caused by increased transpiration (2.16 mm yr −2 ) and interception (0.27 mm yr −2 ), which was partly offset by decreased soil evaporation (−0.47 mm yr −2 ). Meanwhile, although the average ET of the forest was larger (480.4 ± 14.8 mm yr −1 ), it was found that the change in total ET of the region was dominated by that in grassland and cropland (1.1 km 3 yr −2 , 90% altogether). Factorial simulations indicated that the intensifying ET over 79.4% and 9.1% of the study area can be explained by vegetation greening and climate change, respectively. Further analysis suggested that the vegetation greening and the increased ET were primarily associated with the rapid urbanization and agricultural intensification. Our findings highlight the potential unfavorable effects of socio‐economic activities on water resources management on this coupled natural‐human system that is already facing water scarcity issues.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 08-2014
Publisher: Elsevier BV
Date: 09-2020
Publisher: Springer Science and Business Media LLC
Date: 02-10-2018
Publisher: Wiley
Date: 23-09-2019
DOI: 10.1002/JOC.5861
Publisher: Springer Science and Business Media LLC
Date: 05-12-2019
Publisher: Springer Science and Business Media LLC
Date: 27-01-2018
Publisher: Wiley
Date: 27-02-2020
DOI: 10.1002/AGJ2.20088
Publisher: Copernicus GmbH
Date: 17-06-2010
Abstract: Abstract. Precipitation variability and complex topography often create a mosaic of vegetation communities in mountainous headwater catchments, creating a challenge for measuring and interpreting energy and mass fluxes. Understanding the role of these communities in modulating energy, water and carbon fluxes is critical to quantifying the variability in energy, carbon, and water balances across landscapes. The focus of this paper was: (1) to demonstrate the utility of eddy covariance (EC) systems in estimating the evapotranspiration component of the water balance of complex headwater mountain catchments and (2) to compare and contrast the seasonal surface energy and carbon fluxes across a headwater catchment characterized by large variability in precipitation and vegetation cover. Eddy covariance systems were used to measure surface fluxes over sagebrush (Artemesia arbuscula and Artemesia tridentada vaseyana), aspen (Populus tremuloides) and the understory of grasses and forbs beneath the aspen canopy. Peak leaf area index of the sagebrush, aspen, and aspen understory was 0.77, 1.35, and 1.20, respectively. The sagebrush and aspen canopies were subject to similar meteorological forces, while the understory of the aspen was sheltered from the wind. Missing periods of measured data were common and made it necessary to extrapolate measured fluxes to the missing periods using a combination of measured and simulated data. Estimated cumulative evapotranspiratation from the sagebrush, aspen trees, and aspen understory were 384 mm, 314 mm and 185 mm. A water balance of the catchment indicated that of the 699 mm of areal average precipitation, 421 mm was lost to evapotranspiration, and 254 mm of streamflow was measured from the catchment water balance closure for the catchment was within 22 mm. Fluxes of latent heat and carbon for all sites were minimal through the winter. Growing season fluxes of latent heat and carbon were consistently higher above the aspen canopy than from the other sites. While growing season carbon fluxes were very similar for the sagebrush and aspen understory, latent heat fluxes for the sagebrush were consistently higher, likely because it is more exposed to the wind. Sensible heat flux from the aspen tended to be slightly less than the sagebrush site during the growing season when the leaves were actively transpiring, but exceeded that from the sagebrush in May, September and October when the net radiation was not offset by evaporative cooling in the aspen. Results from this study demonstrate the utility of EC systems in closing the water balance of headwater mountain catchments and illustrate the influence of vegetation on the spatial variability of surface fluxes across mountainous rangeland landscapes.
Publisher: Wiley
Date: 05-03-2014
DOI: 10.1002/ECO.1478
Publisher: Informa UK Limited
Date: 06-2010
Publisher: Elsevier BV
Date: 02-2018
Publisher: MDPI AG
Date: 24-06-2022
DOI: 10.3390/SU14137719
Abstract: Spatial and temporal variations in the potential yields of highland barley is important for making policies on adaptation of agriculture to climate change in the Three Rivers Region (TRR), one of the main highland barley growing areas on the Tibetan Plateau. This research tries to explore a suitable strategy for simulating potential yields of highland barley by the WOFOST (WOrld FOod STudies) crop growth model, and further to identify variations in climate conditions and potential yields in TRR from 1961 to 2020 for making policies on adaptation of agricultural production to the climate change impacts on the Tibetan Plateau. Validation results indicated that WOFOST could accurately simulate the potential yields of highland barley with the global radiation estimated by the calibrated Angstrom model. The global radiation during the growth periods decreased at a rate of 0.047 MJ/m2a, while the temperature during the growth periods increased at rates ranging from 0.019 to 0.087 °C/a, which was greater than the average warming rate of the globe. The simulated potential yields ranged from 10,300 to 14,185 kg/ha in TRR, with an average decreasing rate of 28 kg/ha/a. The decrease in the potential yields was mainly attributed to the shortened critical period caused by warming effects, so cultivation of new varieties of highland barley with longer growth periods is suggested as an achievable strategy for the adaptation of highland barley to climate change in TRR.
Publisher: Inter-Research Science Center
Date: 13-03-2008
DOI: 10.3354/CR00729
Publisher: Wiley
Date: 15-01-2018
DOI: 10.1111/GCB.14034
Abstract: Climate change threatens global wheat production and food security, including the wheat industry in Australia. Many studies have examined the impacts of changes in local climate on wheat yield per hectare, but there has been no assessment of changes in land area available for production due to changing climate. It is also unclear how total wheat production would change under future climate when autonomous adaptation options are adopted. We applied species distribution models to investigate future changes in areas climatically suitable for growing wheat in Australia. A crop model was used to assess wheat yield per hectare in these areas. Our results show that there is an overall tendency for a decrease in the areas suitable for growing wheat and a decline in the yield of the northeast Australian wheat belt. This results in reduced national wheat production although future climate change may benefit South Australia and Victoria. These projected outcomes infer that similar wheat-growing regions of the globe might also experience decreases in wheat production. Some cropping adaptation measures increase wheat yield per hectare and provide significant mitigation of the negative effects of climate change on national wheat production by 2041-2060. However, any positive effects will be insufficient to prevent a likely decline in production under a high CO
Publisher: Wiley
Date: 08-05-2018
DOI: 10.1111/GCB.14274
Abstract: Given the important contributions of semiarid region to global land carbon cycle, accurate modeling of the interannual variability (IAV) of terrestrial gross primary productivity (GPP) is important but remains challenging. By decomposing GPP into leaf area index (LAI) and photosynthesis per leaf area (i.e., GPP_leaf), we investigated the IAV of GPP and the mechanisms responsible in a temperate grassland of northwestern China. We further assessed six ecosystem models for their capabilities in reproducing the observed IAV of GPP in a temperate grassland from 2004 to 2011 in China. We observed that the responses to LAI and GPP_leaf to soil water significantly contributed to IAV of GPP at the grassland ecosystem. Two of six models with prescribed LAI simulated of the observed IAV of GPP quite well, but still underestimated the variance of GPP_leaf, therefore the variance of GPP. In comparison, simulated pattern by the other four models with prognostic LAI differed significantly from the observed IAV of GPP. Only some models with prognostic LAI can capture the observed sharp decline of GPP in drought years. Further analysis indicated that accurately representing the responses of GPP_leaf and leaf stomatal conductance to soil moisture are critical for the models to reproduce the observed IAV of GPP_leaf. Our framework also identified that the contributions of LAI and GPP_leaf to the observed IAV of GPP were relatively independent. We conclude that our framework of decomposing GPP into LAI and GPP_leaf has a significant potential for facilitating future model intercomparison, benchmarking and optimization should be adopted for future data-model comparisons.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 11-2012
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 09-2006
Publisher: Elsevier BV
Date: 05-2022
Publisher: Wiley
Date: 11-2008
DOI: 10.2134/JEQ2007.0601
Abstract: Excessive N and water use in agriculture causes environmental degradation and can potentially jeopardize the sustainability of the system. A field study was conducted from 2000 to 2002 to study the effects of four N treatments (0, 100, 200, and 300 kg N ha(-1) per crop) on a wheat (Triticum aestivum L.) and maize (Zea mays L.) double cropping system under 70 +/- 15% field capacity in the North China Plain (NCP). The root zone water quality model (RZWQM), with the crop estimation through resource and environment synthesis (CERES) plant growth modules incorporated, was evaluated for its simulation of crop production, soil water, and N leaching in the double cropping system. Soil water content, biomass, and grain yield were better simulated with normalized root mean square errors (NRMSE, RMSE ided by mean observed value) from 0.11 to 0.15 than soil NO(3)-N and plant N uptake that had NRMSE from 0.19 to 0.43 across these treatments. The long-term simulation with historical weather data showed that, at 200 kg N ha(-1) per crop application rate, auto-irrigation triggered at 50% of the field capacity and recharged to 60% field capacity in the 0- to 50-cm soil profile were adequate for obtaining acceptable yield levels in this intensified double cropping system. Results also showed potential savings of more than 30% of the current N application rates per crop from 300 to 200 kg N ha(-1), which could reduce about 60% of the N leaching without compromising crop yields.
Publisher: Elsevier BV
Date: 12-2013
Publisher: Copernicus GmbH
Date: 11-03-2021
Abstract: Abstract. Root water uptake by plants is a vital process that influences terrestrial energy, water, and carbon exchanges. At the soil, vegetation, and atmosphere interfaces, root water uptake and solar radiation predominantly regulate the dynamics and health of vegetation growth, which can be remotely monitored by satellites, using the soil–plant relationship proxy – solar-induced chlorophyll fluorescence. However, most current canopy photosynthesis and fluorescence models do not account for root water uptake, which compromises their applications under water-stressed conditions. To address this limitation, this study integrated photosynthesis, fluorescence emission, and transfer of energy, mass, and momentum in the soil–plant–atmosphere continuum system, via a simplified 1D root growth model and a resistance scheme linking soil, roots, leaves, and the atmosphere. The coupled model was evaluated with field measurements of maize and grass canopies. The results indicated that the simulation of land surface fluxes was significantly improved by the coupled model, especially when the canopy experienced moderate water stress. This finding highlights the importance of enhanced soil heat and moisture transfer, as well as dynamic root growth, on simulating ecosystem functioning.
Publisher: Wiley
Date: 08-01-2008
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 12-2020
Publisher: Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria (INIA)
Date: 26-07-2019
DOI: 10.5424/SJAR/2019172-14699
Abstract: Grain yield of spring wheat (Triticum aestivum L.) fluctuates greatly in Western Loess Plateau of China due to limited and highly variable precipitation. Farmers in this area need a simple tool to predict spring wheat grain yield and assess yield loss risk efficiently. The objectives of this study were to establish relations between water use and grain yield of spring wheat for predicting actual yield and attainable yield (water limited yield) under conventional management practice and mulching practices. Reference data during 1993-2013 and field experiment conducted from 1987 to 2011 were used to determine water use-yield production function and boundary function for spring wheat. Probability of achieving a given spring wheat grain yield threshold is determined based on available soil water content at sowing plus expected precipitation during growing season. Single linear equation was obtained with slope of 14.6 kg ha-1 mm-1 and x intercept at 126.3 mm for spring wheat water use-yield production function with different wheat varieties under varying climatic patterns. The slopes of the boundary function were 16.2 kg ha-1 mm-1 and 19.1 kg ha-1 mm-1 under conventional management practice and mulching practices, respectively. With increase of available soil water content at sowing, the probability of achieving at least 2000 and 4000 kg ha-1 of spring wheat for actual and attainable yield increased under different agricultural management practices.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 11-2015
Publisher: MDPI AG
Date: 07-2017
DOI: 10.3390/EN10070892
Publisher: Elsevier BV
Date: 03-2015
Publisher: Wiley
Date: 02-01-2020
DOI: 10.1111/TGIS.12607
Publisher: Elsevier BV
Date: 04-2020
Publisher: Wiley
Date: 06-04-2018
DOI: 10.1002/ECO.1974
Publisher: MDPI AG
Date: 18-09-2018
DOI: 10.3390/W10091273
Abstract: The Gongshui River basin exhibits one of the most serious soil erosion areas in southern China, and has always been the key control area of national soil and water conservation programs. This study used daily precipitation, streamflow, and sediment concentration data collected from 1957 to 2015 from the main hydrological stations of the Gongshui River to investigate streamflow and sediment discharge variations and their responses to precipitation and human activities. The Mann-Kendall and Pettitt’s test were used for trend and change-point detection. The double mass curve (DMC) method was employed to quantify the effects of precipitation change and human activities on hydrological regime shifts. The results showed insignificant trends of both annual precipitation and streamflow for all stations, while the sediment discharge of most stations exhibited significant decreasing trends. Change-point analyses revealed that all hydrologic stations except Mazhou had transition years. The estimation via DMC indicated that after the change point years, there was a rapid reduction in sediment discharge at Hanlinqiao, Fengkeng, Julongtan, Xiashan, and Chawu stations, but not at Mazhou, Ruijin, and Yangxinjian stations. Human activity provided a significantly greater contribution to sediment discharge than precipitation. The evidence clearly indicates that the degree and extension of conservation or destruction measures and the construction of large- and medium-sized reservoirs were the major factors significantly decreasing or increasing annual sediment discharge of the Gongshui River. This work could serve as the basis for decision making regarding river basin water resources management to estimate the effects of anthropogenic impacts on water and sediment discharge variations during the last few decades, thereby guiding adaptation and protection of the water resources of the Gongshui River flowing into the Poyang Lake.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 09-2008
Publisher: Elsevier BV
Date: 02-2021
Publisher: Wiley
Date: 08-03-2015
DOI: 10.1111/GCBB.12145
Publisher: Springer Science and Business Media LLC
Date: 22-07-2021
Publisher: Elsevier BV
Date: 04-2020
Publisher: Engineering Sciences Press
Date: 2017
Publisher: Wiley
Date: 05-2006
Publisher: Elsevier BV
Date: 2020
Publisher: Copernicus GmbH
Date: 03-06-2016
Abstract: Abstract. The savanna ecosystem is one of the most dominant and complex terrestrial biomes, deriving from a distinct vegetative surface comprised of co-dominant tree and grass populations. While these two vegetation types co-exist functionally, demographically they are not static but are dynamically changing in response to environmental forces such as annual fire events and rainfall variability. Modelling savanna environments with the current generation of terrestrial biosphere models (TBMs) has presented many problems, particularly describing fire frequency and intensity, phenology, leaf biochemistry of C3 and C4 photosynthesis vegetation, and root-water uptake. In order to better understand why TBMs perform so poorly in savannas, we conducted a model inter-comparison of six TBMs and assessed their performance at simulating latent energy (LE) and gross primary productivity (GPP) for five savanna sites along a rainfall gradient in northern Australia. Performance in predicting LE and GPP was measured using an empirical benchmarking system, which ranks models by their ability to utilise meteorological driving information to predict the fluxes. On average, the TBMs performed as well as a multi-linear regression of the fluxes against solar radiation, temperature and vapour pressure deficit but were outperformed by a more complicated nonlinear response model that also included the leaf area index (LAI). This identified that the TBMs are not fully utilising their input information effectively in determining savanna LE and GPP and highlights that savanna dynamics cannot be calibrated into models and that there are problems in underlying model processes. We identified key weaknesses in a model's ability to simulate savanna fluxes and their seasonal variation, related to the representation of vegetation by the models and root-water uptake. We underline these weaknesses in terms of three critical areas for development. First, prescribed tree-rooting depths must be deep enough, enabling the extraction of deep soil-water stores to maintain photosynthesis and transpiration during the dry season. Second, models must treat grasses as a co-dominant interface for water and carbon exchange rather than a secondary one to trees. Third, models need a dynamic representation of LAI that encompasses the dynamic phenology of savanna vegetation and its response to rainfall interannual variability. We believe that this study is the first to assess how well TBMs simulate savanna ecosystems and that these results will be used to improve the representation of savannas ecosystems in future global climate model studies.
Publisher: Elsevier BV
Date: 09-2020
Publisher: IOP Publishing
Date: 08-2020
Abstract: Probabilistic seasonal rainfall forecasting is of great importance for stakeholders such as farmers and policymakers to assist in developing risk management strategies and to inform decisions. In practice, there are two kinds of commonly used tools, dynamical models and statistical models, to provide probabilistic seasonal rainfall forecasts. Dynamical models are based on physical processes but are usually expensive to operate and implement, and rely overly on initial conditions. Statistical models are easy to implement but are usually based on simple or linear relationships between observed variables. Recently, machine learning techniques have been widely used in climate projection and perform well in reproducing historical climate. For these reasons, we conducted a case study in Australia by developing a machine learning-based probabilistic seasonal rainfall forecasting model using multiple large-scale climate indices from the Pacific, Indian and Southern Oceans. Rainfall probabilities of exceeding the climatological median for upcoming seasons from 2011 to 2018 were successively forecasted using multiple climate indices of precedent six months. The performance of the model was evaluated by comparing it with an officially used forecasting model, the SOI (Southern Oscillation Index) phase model (SP) operated by Queensland government in Australia. Results indicated that the random forest (RF) model outperformed the SP model in terms of both distinct forecasts and forecasting accuracy. The RF model increased the percentages of distinct forecasts to 64.9% for spring, to 71.5% for summer, to 65.8% for autumn, and to 63.9% for winter, 1.4 ∼ 3.2 times of the values from the SP model. Forecasting accuracy was also greatly increased by 28%, 167%, 219%, and 76% for four seasons respectively, compared to the SP model. The proposed rainfall forecasting model is based on readily available data, and we believe it can be easily extended to other regions to provide seasonal rainfall outlooks.
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.SCITOTENV.2018.06.028
Abstract: The Loess Plateau, the largest arid and semi-arid zone in China, has been confronted with more severe water resource pressure and a growing demand for food production under global changes. For developing sustainable agriculture in this region, it is critical to learn spatiotemporal variations in water use efficiency (WUE) of main crops (e.g. winter wheat in this region) under various water management practices. In this study, we classified irrigated and rainfed wheat areas based on MODIS data, and calculated the winter wheat yield by using an improved light use efficiency model. The actual evapotranspiration (ETa) of winter wheat and the evapotranspiration drought index (EDI) were also investigated. Then we mainly examined the synergistic relationship between crop yield, ETa, and WUE, and analyzed the variations in WUE of irrigated and rainfed wheat under water stress during the 2010-2011 growing season. The results suggested that winter wheat in the Loess Plateau was primarily dominated by rainfed wheat. The average yield of irrigated wheat was 3928.4 kg/ha, 22.2% more than that of rainfed wheat. High spatial heterogeneities of harvest index (HI) and maximum light use efficiency (ε
Publisher: Informa UK Limited
Date: 12-2009
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 10-2021
Publisher: Elsevier BV
Date: 12-2008
Publisher: American Geophysical Union (AGU)
Date: 11-10-2012
DOI: 10.1029/2012JG002038
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-04-2007
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 03-2022
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/MF13082
Abstract: Plant-community structure and groundwater attributes were investigated in Ejina Delta in north-western China to understand spatial variability of groundwater depth and composition and their impacts on vegetation succession. Geostatistical methods and ordination analysis were performed to analyse the data. In addition, we tried to obtain vegetation successional series by using an approach of spatial sequences instead of temporal sequences. The findings of the present study were as follows: (1) the coefficient of variation for groundwater depth (GWD), salinity (SAL), total dissolved solids (TDS), electrical conductivity (EC), pH, Ca2+, Mg2+, K+, Na+, SO42–, HCO3–, NO3–, Cl– and F– ranged from 0.04 to 1.53 (2) GWD, Mg2+, TDS, EC, Ca2+, HCO3–, NO3– and pH showed strong spatial autocorrelation, whereas K+ and SAL showed moderate spatial autocorrelation (3) canonical correspondence analysis revealed that groundwater heterogeneity, especially GWD, followed by pH, SAL, TDS, EC and HCO3–, had an important impact on vegetation succession, and thus showed a prevalence of groundwater attributes-based niche differentiation among plant communities and (4) there were two vegetation successional processes (drought and salinisation) in the lower Heihe River Basin, and salinisation processes increased with drought processes. Our results indicated that high spatial variability of groundwater attributes contributes to promoting maintenance of species and landscape ersity in the lower Heihe River Basin.
Publisher: Elsevier BV
Date: 2014
Publisher: Wiley
Date: 18-09-2021
DOI: 10.1002/ECO.2252
Publisher: Elsevier BV
Date: 06-2019
Publisher: MDPI AG
Date: 22-06-2022
DOI: 10.3390/RS14132985
Abstract: Accurate characterization of spatial patterns and temporal variations in dryland vegetation is of great importance for improving our understanding of terrestrial ecosystem functioning under changing climates. Here, we explored the spatiotemporal variability of dryland vegetation phenology using satellite-observed Solar-Induced chlorophyll Fluorescence (SIF) and the Enhanced Vegetation Index (EVI) along the North Australian Tropical Transect (NATT). Substantial impacts of extreme drought and intense wetness on the phenology and productivity of dryland vegetation are observed by both SIF and EVI, especially in the arid/semiarid interior of Australia without detectable seasonality in the dry year of 2018–2019. The greenness-based vegetation index (EVI) can more accurately capture the seasonal and interannual variation in vegetation production than SIF (EVI r2: 0.47~0.86, SIF r2: 0.47~0.78). However, during the brown-down periods, the rate of decline in EVI is evidently slower than that in SIF and in situ measurement of gross primary productivity (GPP), due partially to the advanced seasonality of absorbed photosynthetically active radiation. Over 70% of the variability of EVI (except for Hummock grasslands) and 40% of the variability of SIF (except for shrublands) can be explained by the water-related drivers (rainfall and soil moisture). By contrast, air temperature contributed to 25~40% of the variability of the effective fluorescence yield (SIFyield) across all biomes. In spite of high retrieval noises and variable accuracy in phenological metrics (MAE: 8~60 days), spaceborne SIF observations, offsetting the drawbacks of greenness-based phenology products with a potentially lagged end of the season, have the promising capability of mapping and characterizing the spatiotemporal dynamics of dryland vegetation phenology.
Publisher: Springer Science and Business Media LLC
Date: 26-03-2019
Publisher: Wiley
Date: 04-11-2021
DOI: 10.1002/ECO.2257
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/BT11181
Abstract: Groundwater-dependent vegetation (GDV) is useful as an indicator of watertable depth and water availability in north-western China. Nitrogen (N) is an essential limiting resource for growth of GDV. To elucidate how leaf N allocation and partitioning influence photosynthesis and photosynthetic N-use efficiency (PNUE), three typical GDV species were selected, and their photosynthesis, leaf N allocation and partitioning were investigated in the Taklamakan Desert. The results showed that Karelinia caspica (Pall.) Less. and Peganum harmala L. had lower leaf N content, and allocated a lower fraction of leaf N to photosynthesis. However, they were more efficient in photosynthetic N partitioning among photosynthetic components. They partitioned a higher fraction of the photosynthetic N to carboxylation and showed higher PNUE, whereas Alhagi sparsifolia Shap. partitioned a higher fraction of the photosynthetic N to light-harvesting components. For K. caspica and P. harmala, the higher fraction of leaf N was allocated to carboxylation and bioenergetics, which led to a higher maximum net photosynthetic rate, and therefore to a higher PNUE, water-use efficiency (WUE), respiration efficiency (RE) and so on. In the desert, N and water are limiting resources K. caspica and P. harmala can benefit from the increased PNUE and WUE. These physiological advantages and their higher leaf-area ratio (LAR) may contribute to their higher resource-capture ability.
Publisher: Elsevier BV
Date: 2022
Publisher: Wiley
Date: 06-08-2004
DOI: 10.1002/HYP.5528
Publisher: Wiley
Date: 10-2007
Publisher: Public Library of Science (PLoS)
Date: 20-02-2014
Publisher: Elsevier BV
Date: 07-2021
Publisher: Elsevier BV
Date: 03-2022
Publisher: Elsevier BV
Date: 08-2010
Publisher: MDPI AG
Date: 27-05-2020
DOI: 10.3390/RS12111722
Abstract: The Tibetan Plateau has been undergoing accelerated warming over recent decades, and is considered an indicator for broader global warming phenomena. However, our understanding of warming rates with elevation in complex mountain regions is incomplete. The most serious concern is the lack of high-quality near-surface air temperature (Tair) datasets in these areas. To address this knowledge gap, we developed an automated mapping framework for the estimation of seamless daily minimum and maximum Land Surface Temperatures (LSTs) for the Tibetan Plateau from the existing MODIS LST products for a long period of time (i.e., 2002–present). Specific machine learning methods were developed and linked with target-oriented validation and then applied to convert LST to Tair. Spatial variables in retrieving Tair, such as solar radiation and vegetation indices, were used in estimation of Tair, whereas MODIS LST products were mainly focused on temporal variation in surface air temperature. We validated our process using independent Tair products, revealing more reliable estimates on Tair the R2 and RMSE at monthly scales generally fell in the range of 0.9–0.95 and 1–2 °C. Using these continuous and consistent Tair datasets, we found temperature increases in the elevation range between 2000–3000 m and 4000–5000 m, whereas the elevation interval at 6000–7000 m exhibits a cooling trend. The developed datasets, findings and methodology contribute to global studies on accelerated warming.
Publisher: IOP Publishing
Date: 07-2021
Abstract: Global crop production and population distributions have undergone great changes under climate change and socioeconomic development, and have drawn considerable public attention. How to explain the similarity of the migration patterns of crop yield and population density for different countries/regions is still uncertain and worth studying. Here, we estimated the similarity between migrations of main crop caloric yield (i.e. maize, rice, wheat, and soybean) and population density using Fréchet distance, and investigated the regression relationship between Fréchet distance and related climatic and socioeconomic variables for countries/regions with different economic development stages. The results indicated that different countries/regions showed different Fréchet distances during 2000–2015, with a maximum value of 24.44 for Russia and a minimum value of 0.11 for Georgia. For countries/regions with different economic development stages, the built regression models can explain 39%–93% of the variability in the Fréchet distance. Log(land area), log(GDP), and log(land area under cereal production) were always included in regression models and had higher importance in explaining the variability of Fréchet distance. For the model for all countries/regions, both the log(land area) and log(GDP per capita) may positively link to the Fréchet distance. Possible reasons for these results are that countries/regions with high GDP (or GDP per capita) may ease the conflict of land resources between humans and crops to achieve agricultural industrialization, which causes the far connection of the migrations for crop caloric yield and population density. The complicated interactions of crop production, population dynamic, and socioeconomic development should be given greater attention in the future.
Publisher: Wiley
Date: 07-2014
Publisher: IOP Publishing
Date: 02-2020
Abstract: Climate change, with increased temperatures and varied rainfall, poses a great challenge to food security around the world. Appropriately assessing the impacts of climate change on crop productivity and understanding the adaptation potential of agriculture to climate change are urgently needed to help develop effective strategies for future agriculture and to maintain food security. In this study, we studied future maize yield changes under 1.5 °C (2018–2037) and 2 °C (2044–2063) warming scenarios and investigated the adaptation potential across China’s Maize Belt by optimizing the sowing date and cultivar using the APSIM-Maize model. In comparison to the baseline scenario, under the 1.5 °C and 2 °C warming scenarios, we found that without adaptation, maize yields would increase in the relatively cool regions with a single-cropping system but decrease in other regions. However, in comparison with the baseline scenario, under the 1.5 °C and 2 °C warming scenarios with adaptation, maize yields would increase by 11.1%–53.9% across the study area. Across the maize belt, compared with the baseline scenario, under warming of 1.5 °C, the potential sowing window would increase by 2–17 d, and under warming of 2 °C, this sowing window would increase by 4–26 d. The optimal sowing window would also be significantly extended in the regions with single-cropping systems by an average of 10 d under the 1.5 °C warming scenario and 12 d under the 2 °C warming scenario. Late-maturing cultivar achieved higher yield than early-middle maturing cultivars in all regions except the north part of Northeast China. Adjusting the sowing date by increasing growth-period precipitation contributed more (44.5%–96.7%) to yield improvements than shifting cultivars (0%–50.8%) and climate change (−53.1% to 23.0%) across all maize planting regions except in the wet southwestern parts of the maize belt. The differences among the maize planting regions in terms of high adaptation potential provide invaluable information for policymakers and stakeholders of maize production to set out optimized agricultural strategies to safeguard the supply of maize.
Publisher: Wiley
Date: 05-2010
Publisher: Springer Science and Business Media LLC
Date: 11-03-2018
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 2022
Publisher: Elsevier BV
Date: 11-2017
Publisher: American Meteorological Society
Date: 10-2013
Abstract: Accurate prediction of evapotranspiration E depends upon representative characterization of meteorological conditions in the boundary layer. Drag and bulk transfer coefficient schemes for estimating aerodynamic resistance to vapor transfer were compared over a semiarid natural woodland ecosystem in central Australia. Aerodynamic resistance was overestimated from the drag coefficient, resulting in limited E at intermediate values of vapor pressure deficit. Large vertical humidity gradients were present during the summer, causing ergence between momentum and vapor transport within and above the canopy surface. Because of intermittency in growth of the summer-active, rain-dependent understory and physiological responses of the canopy, leaf resistance varied from less than 50 s m−1 to greater than 106 s m−1, in which the particularly large values were obtained from inversion of drag coefficient resistance. Soil moisture limitations further contributed to ergence between actual and reference E. Unsurprisingly, inclusion of site-specific meteorological (e.g., vertical humidity gradients) and hydrological (e.g., soil moisture content) information improved the accuracy of predicting E when applying Penman–Monteith analysis. These results apply regardless of canopy layering (i.e., even when the understory was not present) wherever atmospheric humidity gradients develop and are thus not restricted to two-layer canopies in semiarid regions.
Publisher: Elsevier BV
Date: 04-2007
Publisher: Elsevier BV
Date: 03-2022
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 12-2021
Publisher: Wiley
Date: 09-2021
DOI: 10.1002/LDR.3730
Abstract: Although it is generally believed the Grain for Green programme (GFG) implemented in China has attenuated soil erosion, the extent to which it is effective still needs verification. Taking Yan'an in the Loess Plateau as the study area, we analysed both total effect and efficiency differences during GFG implementation. Results showed that, while soil erosion on average decreased from 4,884.49 to 4,087.57 t km −2 yr −1 , counties with higher GFG implementation intensity achieved a lower soil conservation effect. For ex le, Wuqi ranks third in the GFG implementation intensity among all counties in Yan'an, but its actual soil erosion reduction is the lowest, only 54.1% of Yan'an's average level. To analyse the reason for the efficiency difference, the concept of soil conservation potential was proposed. It is concluded that the soil conservation effect is controlled by the soil conservation potential. Ideally, regions with high soil conservation potential should get priority in the GFG application, yet there is a significant spatial mismatch between the GFG implementation intensity and the soil conservation potential because the correlation coefficient is only −0.05, which weakened the soil control effect. A dynamic implementation mechanism was put forward for the formulation and optimization of ecological programmes and projects in future: first, using the soil conservation potential to determine the implementation intensity in each region second, adjusting the intensity to the changes of the soil conservation potential in the following implementation third, repeating above steps to ensure high efficiency of soil erosion control, and achieving the sustainability and effectiveness of the ecological projects.
Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 08-2006
Publisher: Springer Science and Business Media LLC
Date: 21-07-2022
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 06-2021
Publisher: Springer Science and Business Media LLC
Date: 02-11-2020
Publisher: Elsevier BV
Date: 09-2015
Publisher: Elsevier BV
Date: 05-2022
Publisher: Elsevier BV
Date: 05-2020
Publisher: Springer Science and Business Media LLC
Date: 23-01-2021
Publisher: Springer Science and Business Media LLC
Date: 22-08-2013
Abstract: Abies faxoniana is the dominant plant species of the forest ecosystem on the eastern edge of Qinghai-Tibet Plateau, where the treeline is strongly defined by climate. The tree-ring chronologies and age structure of Abies faxoniana were developed in the treeline ecotones on the northwestern and southeastern aspects of the Min Mountains in the Wanglang Nature Reserve to examine the treeline dynamics of recent decades in response to climate change. On the northwestern aspect, correlation analysis showed that the radial growth was significantly and positively correlated with precipitation in current January and monthly mean temperature in current April, but significantly and negatively correlated with monthly mean temperature in previous August. On the southeastern aspect, the radial growth was significantly negatively correlated with monthly mean temperature in previous July and August. The different responses of radial growth to climatic variability on both the aspects might be mainly due to the micro-environmental conditions. The recruitment benefited from the warm temperature in current April, July and September on the northwestern aspect. The responses of radial growth and recruitment to climatic variability were similar on the northwestern slope. Recruitment was greatly restricted by competition with dense bamboos on the southeastern aspect.
Publisher: Elsevier BV
Date: 02-2010
Publisher: American Society of Agricultural and Biological Engineers (ASABE)
Date: 2017
DOI: 10.13031/TRANS.12363
Abstract: Deficit irrigation has been shown to increase crop water use efficiency (WUE) under certain conditions, even though the yield is slightly reduced. In this study, the Root Zone Water Quality Model (RZWQM) was first calibrated with measured data from a large weighing lysimeter from 1998 to 2003 at the Yucheng Experimental Station in the North China Plain for daily evapotranspiration (ET), soil water storage (0-120 cm), leaf area index (LAI), aboveground biomass, and grain yield. The calibrated model was then used to explore crop responses to ET-based irrigation management using weather data from 1958 to 2015 and identify the most suitable ET-based irrigation schedules for the area. Irrigation amount was determined by constraining irrigation to a percentage of potential crop ET (40%, 60%, 80%, and 100% ET c ) at the various growth stages of wheat [planting to before winter dormancy (P-D), green up to booting (G-B), booting to flowering (B-F), and flowering to maturity (F-M)] and of maize [planting to silking (P-S) and silking to maturity (S-M)], subject to seasonal water availability limits of 100/50, 200/100, 300/150, and 400/200 mm and no water limit for wheat/maize seasons, respectively. In general, wheat was more responsive to irrigation than maize, while greater influence of weather variation was simulated on maize than on wheat. For wheat with seasonal water limits, the highest average WUE was simulated with the highest targeted ET c levels at both the G-B and B-F stages and lower targeted ET c levels at the P-D and F-M stages. However, the highest average grain yield was simulated with the highest targeted ET c levels at all four growth stages for no water limit and the 400 mm water limit, or at both the G-B and B-F stages for the 300 and 200 mm water limits. For maize, lower targeted ET c levels after silking did not significantly affect maize production due to the high season rainfall, but irrigation of 60% ET c before silking was recommended. These results could be used as guidelines for precision irrigation along with real-time weather information. Keywords: Deficit irrigation, Evapotranspiration, Growth stage, RZWQM, Water use efficiency, Wheat and maize.
Publisher: IOP Publishing
Date: 10-2021
Publisher: MDPI AG
Date: 12-2016
DOI: 10.3390/W8120564
Publisher: IOP Publishing
Date: 10-2014
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.SCITOTENV.2019.135638
Abstract: Crop phenology is determined by both climatic factors and agronomic management practices such as sowing date and cultivar characteristics. Exploring the interactive effects of climate change and crop management practices on crop phenology can be used to devise adaptation strategies to mitigate climate change. The objectives of this study were to: 1) examined trends in soybean (Glycine max L.) phenological development in China from 1981 to 2010 2) isolate and quantify impacts of climate change and crop management on changes in soybean phenology 3) determine the relative contribution of climate change and crop management to observed changes in soybean phenology and 4) determine the relative contribution of temperature, precipitation, and sunshine hours to changes in soybean phenology. Changes in soybean phenology were observed across the major soybean producing area of eastern China during 1981-2010. Observed dates of sowing, emergence, anthesis, and maturity were delayed by an average of 1.78, 0.83, 0.19, and 0.62 days decade
Publisher: Elsevier BV
Date: 08-2010
Publisher: Wiley
Date: 30-09-2008
Publisher: Elsevier BV
Date: 2018
Publisher: MDPI AG
Date: 03-2020
DOI: 10.3390/RS12050786
Abstract: Understanding spatio-temporal changes in winter wheat (Triticum aestivum L) phenology and its response to temperature will be vital for adapting to climate change in the coming years. For this purpose, the heading date (HD), maturity date (MD), and length of the reproductive growth period (LRGP) were detected from the remotely sensed leaf area index (LAI) data by a threshold-based method during the harvest year 2003 to 2018 across the North China Plain. The results show that there was high spatial heterogeneity of winter wheat phenology in pixel scale across the whole area, which could not be detected in previous site-based studies. The results also verified that climate warming could explain part of the change in the HD. However, for the LRGP, the potential impact of non-climate effects should be further investigated. This study presents the spatio-temporal changes both in winter wheat phenology and corresponding mean temperature and then analyzes their relationships in pixel scale. Additionally, this study further discusses the potential impact of non-climate effects on the LRGP.
Publisher: Wiley
Date: 2008
DOI: 10.1002/JOC.1520
Publisher: Copernicus GmbH
Date: 11-05-2016
DOI: 10.5194/BG-2016-190
Abstract: Abstract. The savanna complex is a highly erse global biome that occurs within the seasonally dry tropical to sub-tropical equatorial latitudes. Savannas are open-canopy environments that encompass a broad demographic continuum, often characterised by a dynamically changing dominance between C3-tree and C4-grass vegetation, where frequent environmental disturbances such as fire modulates the balance between ephemeral and perennial life forms. Climate change is projected to result in significant changes to the savanna floristic structure, with increases to woody biomass expected through CO2 fertilisation in mesic savannas and increased tree mortality expected through increased rainfall interannual variability in xeric savannas. The complex interaction between vegetation and climate that occurs in savannas has traditionally challenged current-generation terrestrial biosphere models (TBMs), which aim to simulate the interaction between the atmosphere and the land-surface to predict responses of vegetation to changing in environmental forcing. In this review, we examine whether TBMs are able to adequately represent savanna dynamics and what implications potential deficiencies may have for climate change projection scenarios that rely on these models. We start by highlighting the defining characteristic traits and behaviours of savanna, how these differ across continents, and how this information is (or is not) represented in the structural framework of many TBMs. We highlight three dynamic processes that we believe directly affect the water-use and productivity of the savanna system, namely: phenology root-water access and fire dynamics. Following this, we discuss how these processes are represented in many current generation TBMs and whether they are suitable for simulating savanna dynamics. Finally, we give an overview of how eddy-covariance observations in combination with other data sources, can be used in model benchmarking and inter-comparison frameworks to diagnose the performance of TBMs in this environment and formulate roadmaps for future development. Our investigation reveals that many TBMs systematically misrepresent phenology, effects of fire and root-water access (if they are considered at all) and that these should be critical areas for future development. Furthermore, such processes must not be static (i.e. prescribed behaviour), but be capable of responding to the changing environmental conditions in order to emulate the dynamic behaviour of savannas. Without such developments, however, TBMs will have limited predictive capability in making the critical projections needed to understand how savannas will respond to future global change.
Publisher: Wiley
Date: 29-06-2020
DOI: 10.1002/AGJ2.20112
Abstract: Although crop phenology is responsive and adaptable to cultural and climatic conditions, many phenology models are too sensitive to variable climatic conditions. We developed a plastic temperature response function by assuming that development rate was linearly related to temperature and that the linearity was linearly responsive to day of year (DOY v ) of the starting date of the vegetative growth period (VGP). Phenology observations and weather data were acquired for winter wheat ( Triticum aestivum L.), rice ( Oryza sativa L.), maize ( Zea mays L.), and soybean [ Glycine max (L.) Merr.] at 12 locations over 15–26 yr. Additional data were observed for maize grown in an interval planting experiment. For 78.6% of the sites, the crop development rate during the VGP was positively affected by DOY v . Partial correlation analysis (controlling for temperature) indicated that DOY v was independent of temperature. When averaged over all crops and sites, the RMSE for a plastic phenology model based on both response and adaptation mechanisms was lower (RMSE = 2.81 d) than models (RMSE = 3.39) based only on response mechanism ( p .01). Furthermore, simulations produced by the plastic model showed less bias to DOY v , temperature, and year. The plastic function provided a simple and effective method for achieving better phenology simulation accuracy. According to the plastic function, growing season under warming conditions will not be reduced by as much as simulated by models based only on response mechanism, so yield loss due to warming is likely to be overestimated.
Publisher: Elsevier BV
Date: 11-2014
Publisher: Springer Science and Business Media LLC
Date: 15-04-2011
Publisher: Elsevier BV
Date: 09-2013
Publisher: Springer Science and Business Media LLC
Date: 15-09-2017
DOI: 10.1038/S41598-017-11063-W
Abstract: Non-forest ecosystems (predominant in semi-arid and arid regions) contribute significantly to the increasing trend and interannual variation of land carbon uptake over the last three decades, yet the mechanisms are poorly understood. By analysing the flux measurements from 23 ecosystems in Australia, we found the the correlation between gross primary production (GPP) and ecosystem respiration (R e ) was significant for non-forest ecosystems, but was not for forests. In non-forest ecosystems, both GPP and R e increased with rainfall, and, consequently net ecosystem production (NEP) increased with rainfall. In forest ecosystems, GPP and R e were insensitive to rainfall. Furthermore sensitivity of GPP to rainfall was dominated by the rainfall-driven variation of LAI rather GPP per unit LAI in non-forest ecosystems, which was not correctly reproduced by current land models, indicating that the mechanisms underlying the response of LAI to rainfall should be targeted for future model development.
Publisher: Springer Science and Business Media LLC
Date: 10-09-2012
DOI: 10.1007/S00484-011-0488-4
Abstract: Climate change presents perhaps the greatest economic and environmental challenge we have ever faced. Climate change and its associated impacts, adaptation and vulnerability have become the focus of current policy, business and research. This paper provides invaluable information for those interested in climate change and its impacts. This paper comprehensively reviews the advances made in the development of regional climate change scenarios and their application in agricultural impact, adaptation and vulnerability assessment. Construction of regional climate change scenarios evolved from the application of arbitrary scenarios to the application of scenarios based on general circulation models (GCMs). GCM-based climate change scenarios progressed from equilibrium climate change scenarios to transient climate change scenarios from the use of direct GCM outputs to the use of downscaled GCM outputs from the use of single scenarios to the use of probabilistic climate change scenarios and from the application of mean climate change scenarios to the application of integrated climate change scenarios considering changes in both mean climate and climate variability.
Publisher: Elsevier BV
Date: 2017
Publisher: Inter-Research Science Center
Date: 07-07-2015
DOI: 10.3354/CR01307
Publisher: Elsevier BV
Date: 07-2019
Publisher: American Meteorological Society
Date: 20-03-2018
Abstract: Water and carbon fluxes simulated by 12 Earth system models (ESMs) that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5) over several recent decades were evaluated using three functional constraints that are derived from both model simulations, or four global datasets, and 736 site-year measurements. Three functional constraints are ecosystem water-use efficiency (WUE), light-use efficiency (LUE), and the partitioning of precipitation P into evapotranspiration (ET) and runoff based on the Budyko framework. Although values of these three constraints varied significantly with time scale and should be quite conservative if being averaged over multiple decades, the results showed that both WUE and LUE simulated by the ensemble mean of 12 ESMs were generally lower than the site measurements. Simulations by the ESMs were generally consistent with the broad pattern of energy-controlled ET under wet conditions and soil water-controlled ET under dry conditions, as described by the Budyko framework. However, the value of the parameter in the Budyko framework ω, obtained from fitting the Budyko curve to the ensemble model simulation (1.74), was larger than the best-fit value of ω to the observed data (1.28). Globally, the ensemble mean of multiple models, although performing better than any in idual model simulations, still underestimated the observed WUE and LUE, and overestimated the ratio of ET to P, as a result of overestimation in ET and underestimation in gross primary production (GPP). The results suggest that future model development should focus on improving the algorithms of the partitioning of precipitation into ecosystem ET and runoff, and the coupling of water and carbon cycles for different land-use types.
Publisher: Wiley
Date: 30-11-2008
DOI: 10.1002/JOC.1677
Publisher: Elsevier BV
Date: 08-0002
Publisher: Wiley
Date: 09-2013
Abstract: Better water and nitrogen (N) management requires better understanding of soil water and N balances and their effects on crop yield under various climate and soil conditions. In this study, the calibrated Root Zone Water Quality Model (RZWQM2) was used to assess crop yield and N leaching under current and alternative management practices in a double-cropped wheat ( L.) and maize ( L.) system under long-term weather conditions (1970-2009) for dominant soil types at 15 locations in the North China Plain. The results provided quantitative long-term variation of deep seepage and N leaching at these locations, which strengthened the existing qualitative knowledge for site-specific management of water and N. In general, the current management practices showed high residual soil N and N leaching in the region, with the amounts varying between crops and from location to location and from year to year. Seasonal rainfall explained 39 to 84% of the variability in N leaching (1970-2009) in maize across locations, while for wheat, its relationship with N leaching was significant ( < 0.01) only at five locations. When N and/or irrigation inputs were reduced to 40 to 80% of their current levels, N leaching generally responded more to N rate than to irrigation, while the reverse was true for crop yield at most locations. Matching N input with crop requirements under limited water conditions helped achieve lower N leaching without considerable soil N accumulation. Based on the long-term simulation results and water resources availability in the region, it is recommended to irrigate at 60 to 80% of the current water levels and fertilize only at 40 to 60% of the current N rate to minimizing N leaching without compromising crop yield.
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.JENVMAN.2019.109717
Abstract: In the present study, the impact of different soil surface mulching, fertilization on phosphorus mineralization and bio-availability of spring maize at various growth stages and soil layers (0-20 and 20-40 cm soil layer) were evaluated. The results indicated that the contents of total P and Olsen-Phosphorus (Olsen-P) in the soils of 0-20 cm soil layer were significantly higher than those in the 20-40 cm soil layer at different stages. The addition of organic fertilizer significantly increased the soil total P and Olsen-P content in the 0-20 cm soil layer. The different surface mulching, no mulching (NM), gravel mulching (GM) and film mulching (FM) were significantly affected by the content of Olsen-P in both soil layers during the critical growth period of spring maize. The Ca
Publisher: Elsevier BV
Date: 2020
Publisher: Elsevier BV
Date: 2004
Publisher: MDPI AG
Date: 03-03-2016
DOI: 10.3390/RS8030207
Publisher: Research Square Platform LLC
Date: 14-09-2021
DOI: 10.21203/RS.3.RS-877804/V1
Abstract: Adaption based on social resilience is proposed as effective measures to mitigate hunger and avoid disaster caused by climate change. But these have not been investigated comprehensively in climate-sensitive regions especially necessary-quantitative paths. North Korea (NK, undeveloped) and its neighbors (SK, South Korea, developed China, developing) represent three economic levels that provide us with ex les of how to examine climatic risk and quantify the contribution of social resilience to rice production. Our data-driven estimates show that climatic factors determined rice biomass changes in NK, while non-climatic factors dominated biomass changes in NK’s neighbors. If no action is taken, NK will face a higher climatic risk (with continuous high temperature heatwaves and precipitation extremes) by the 2080s with high emission scenario when rice biomass and production are expected to decrease by 20.2% and 14.4%, respectively, thereby potentially increasing hunger in NK. The contribution of social resilience to food production in the undeveloped region (15.2%) was far below the contribution observed in the developed and developing regions (83.0% and 86.1%, respectively). These findings highlight the importance of social resilience to mitigate the negative effects of climate change on food security and human hunger, and provide necessary-quantitative information.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 06-2020
Publisher: Springer Science and Business Media LLC
Date: 06-2005
DOI: 10.1360/03YD0183
Publisher: Elsevier BV
Date: 03-2004
Publisher: Elsevier BV
Date: 07-2020
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 12-2013
Publisher: Springer Science and Business Media LLC
Date: 09-2002
DOI: 10.1007/S00484-002-0141-3
Abstract: The biomass (X) of a biological population, described by growth models, depends only on time (t), i.e., X = f(t). Some parameters in these models are frequently taken as constants, but they may vary with growth processes under different ecological conditions. An extended logistic model including changes in the influence of meteorological factors is developed to simulate biomass accumulation processes of rice sown on different dates. The model may be generally described as X = f (p, t), in which p stands for meteorological factors. The model can be used to generalize population growth processes in experiments carried out under different environments. It is shown that the model may account for 96.6% of the variance of rice biomass on the basis of sowing dates, developmental stage, solar radiation and temperature in the Yangtze River valley in China.
Publisher: Institute of Experimental Botany
Date: 09-2012
Publisher: Elsevier BV
Date: 02-2020
Publisher: American Geophysical Union (AGU)
Date: 07-2013
DOI: 10.1002/JGRG.20101
Publisher: Springer Science and Business Media LLC
Date: 10-10-2010
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 06-2007
Publisher: Springer Science and Business Media LLC
Date: 27-06-2016
Publisher: Springer Science and Business Media LLC
Date: 05-10-2014
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.WATRES.2019.01.015
Abstract: Global aquatic ecosystems are essential to human existence and have deteriorated seriously in recent years. Understanding the influence mechanism of habitat variation on the structure of the food-web allows the effective recovery of the health of degraded ecosystems. Whereas most previous studies focused on the selection of driving habitat factors, the impact of habitat variation on the food-web structure was rarely studied, resulting in the low success rate of ecosystem restoration projects globally. This paper presents a framework for exploring the effects of spatial variations in water quality and hydrological habitat factors on the food-web structure in city waters. Indices for the evaluation of the food-web structure are first determined by integrating model-parameter extraction via literature refinement. The key water quality and hydrological factors are then determined by coupling canonical correspondence analysis with partial least squares regression. Their spatial variation is investigated using spatial autocorrelation. Finally, fuzzy clustering is applied to analyze the influence of the spatial variations in water quality and hydrological factors on the food-web structure. The results obtained in Ji'nan, the pilot city of water ecological civilization in China, show that the Shannon ersity index, connectance index, omnivory index, and the ratio of total primary production to the total respiration are important indicators of food-web structural change. They show that the driving factors affecting the aquatic food-web structure in Ji'nan are hydrological factors (e.g., river width, water depth, and stream flow), physical aspects of water quality (e.g., air temperature, water temperature, electrical conductivity, and transparency), and chemical aspects (e.g., potassium, dissolved oxygen, calcium, and total hardness). They also show that the stability of the food-web is more prone to spatial variations in water quality than in hydrological factors. Higher electrical conductivity, potassium, total hardness, and air temperature lead to deteriorated food-web structures, whereas better transparency improves structure and stability. We found that water and air temperature are the most important factors in the spatial variation of the food-web structure in the study area, followed by total hardness. Transparency is the least important factor. Large disparities and varied spatial distributions exist in the driving effects of water quality and hydrological factors across regions attributable to differences in geographical environments, water salinity (fresh vs. sea water), and environmental factors (e.g., water pollution). The above methods and results serve as a theoretical and scientific basis for a high success rate of aquatic ecosystem restoration projects in the study area and other cities worldwide.
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 2022
Publisher: Springer Science and Business Media LLC
Date: 17-08-2018
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 04-2023
Publisher: Elsevier BV
Date: 04-2020
Publisher: Elsevier BV
Date: 05-2022
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.CHEMOSPHERE.2019.125167
Abstract: This research developed a method of tracing major water chemical parameters (WCP) and soil heavy metals (HM) to identify the processes of mining pollution in topographically complex landscapes. Ninety-nine spatially distributed water s les were collected to characterise the hydrochemical characteristics of an alpine river in north-west China. Sixty river WCP and fifty-six soil HM s les from areas near mining sites were then used to analyse the mining pollution process. Geographical and mining activity characteristics were derived from topographic and mine site information. The occurrence of sulphates (SO
Publisher: Institute of Experimental Botany
Date: 04-09-2020
DOI: 10.32615/PS.2020.038
Publisher: Elsevier BV
Date: 08-2010
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 03-2022
Publisher: Springer Science and Business Media LLC
Date: 06-2006
Publisher: Elsevier BV
Date: 02-2021
Publisher: Springer Science and Business Media LLC
Date: 12-11-2016
Publisher: American Geophysical Union (AGU)
Date: 16-01-2010
DOI: 10.1029/2009JG001163
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 02-2008
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 08-2010
Publisher: Elsevier BV
Date: 08-2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2016
Publisher: Elsevier BV
Date: 06-2018
Publisher: Wiley
Date: 07-08-2012
DOI: 10.1002/ECO.249
Publisher: Springer Science and Business Media LLC
Date: 09-10-2023
Publisher: Elsevier BV
Date: 11-2020
Publisher: Springer Science and Business Media LLC
Date: 15-03-2016
DOI: 10.1038/SREP23113
Abstract: The global carbon cycle is highly sensitive to climate-driven fluctuations of precipitation, especially in the Southern Hemisphere. This was clearly manifested by a 20% increase of the global terrestrial C sink in 2011 during the strongest sustained La Niña since 1917. However, inconsistencies exist between El Niño/La Niña (ENSO) cycles and precipitation in the historical record for ex le, significant ENSO–precipitation correlations were present in only 31% of the last 100 years, and often absent in wet years. To resolve these inconsistencies, we used an advanced temporal scaling method for identifying interactions amongst three key climate modes (El Niño, the Indian Ocean dipole, and the southern annular mode). When these climate modes synchronised (1999–2012), drought and extreme precipitation were observed across Australia. The interaction amongst these climate modes, more than the effect of any single mode, was associated with large fluctuations in precipitation and productivity. The long-term exposure of vegetation to this arid environment has favoured a resilient flora capable of large fluctuations in photosynthetic productivity and explains why Australia was a major contributor not only to the 2011 global C sink anomaly but also to global reductions in photosynthetic C uptake during the previous decade of drought.
Publisher: MDPI AG
Date: 21-07-2021
Abstract: We used the APSIM-Maize model to simulate maize potential yield (Yp) and rain-fed yield (Yw) when adaptation options of sowing date and planting density were adopted under Representative Concentration Pathway (RCP) 4.5 and 8.5 in the Guanzhong Plain of China. The results showed that Yp would decrease by 10.6–14.9% and 15.0–31.4% under RCP4.5 and RCP8.5 for summer maize, and 13.9–19.7% and 18.5–36.3% for spring maize, respectively. The Yw would decrease by 17.1–19.0% and 23.6–41.1% under RCP4.5 and RCP8.5 for summer maize, and 20.9–24.5% and 27.8–45.5% for spring maize, respectively. The loss of Yp and Yw could be reduced by 2.6–9.7% and 0–9.9%, respectively, under future climate for summer maize through countermeasures. For spring maize, the loss of Yp was mitigated by 14.0–25.0% and 2.0–21.8% for Yw. The contribution of changing sowing date and plant density on spring maize yield was more than summer maize, and the optimal adaptation options were more effective for spring maize. Additionally, the influences of changing sowing date and planting density on yields become weak as climate changes become more severe. Therefore, it is important to investigate the potential of other adaptation measures to cope with climate change in the Guanzhong Plain of China.
Publisher: American Geophysical Union (AGU)
Date: 07-12-2021
DOI: 10.1029/2021JD035589
Abstract: Wildfire is the most prevalent natural disturbance in the North American boreal forest (NABF) and can cause postfire land surface temperature change (Δ T fire ) through biophysical processes. Fire regimes, such as fire severity, fire intensity, and percentage of burned area (PBA), may influence Δ T fire through their impacts on postfire vegetation damage and, if so, there may be important feedbacks between fire regime and climate warming through biophysical effects. Here, we employ satellite observations to investigate postfire diurnal Δ T fire across NABF. We further use a stepwise multiple linear regression model to examine the driving factors for Δ T fire by incorporating latitude, fire regime variables, and their interactions. Our results demonstrate a pronounced asymmetry in diurnal Δ T fire , characterized by daytime warming in contrast to nighttime cooling. Clear latitudinal patterns are found in Δ T fire , with stronger effects in lower latitudes. Such latitudinal patterns of Δ T fire , especially the daytime one, are driven by both latitudinal patterns in fire regimes and an increased sensitivity of Δ T fire to fire regime as the latitude decreases. The multiple linear regression model explains 37% of the variance in daytime Δ T fire , whereas for the nighttime Δ T fire the explanatory power is rather low (5%). For daytime Δ T fire , fire severity accounted for most (43.65%) of the model explanatory power, followed by PBA (24.60%) and fire intensity (13.10%). Our results highlight important fire regime impacts on daytime Δ T fire and, further, on the annual Δ T fire , suggesting that fire might lify future boreal climate change through positive feedbacks between fire regime and postfire surface warming.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 03-2013
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 07-2019
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.SCITOTENV.2018.12.418
Abstract: Ecosystems in arid and semi-arid regions are vulnerable to climatic and anthropogenic disturbances. However, our understanding of vegetation stability (including resistance and resilience, which are the abilities of ecosystems to resist perturbations and return to pre-disturbance structure or function, respectively) in response to environmental changes in dryland ecosystems remains insufficient, particularly in the absence of large-scale observations of water availability. Here we introduced GRACE monthly total water storage anomaly (TWSA) data into an autoregressive model with remote sensed EVI, air temperature and precipitation to investigate the short-term vegetation stability and its influencing factors in Central Asia (CA) during 2003-2015. The results showed that the grid-level vegetation resilience in CA increased logarithmically as mean annual precipitation (R
Publisher: Elsevier BV
Date: 10-2019
Publisher: Springer Science and Business Media LLC
Date: 11-2006
Publisher: Elsevier BV
Date: 08-2010
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 06-2020
Publisher: Wiley
Date: 24-07-2020
DOI: 10.1002/AGJ2.20320
Abstract: Agronomy journals form a core part of the process of scholarly communication and scientific research in the agronomic field. Determining the key features of high‐impact agronomic journals will be a central component for identifying the disciplinary development in the field of agronomy. In this study, we conducted a bibliometric study to fill this knowledge gap based on 64,703 articles published in 18 main agronomy journals since 1948 derived from the Scopus database. Our main findings were that (a) over 20% of publications in Advances in Agronomy and Agricultural and Forest Meteorology received more than 50 citations (b) authors from the United States, China, the United Kingdom, Germany, and Australia published the most articles in these journals, comprising 22.4, 11.5, 10.7, 8.7, and 8.0% of the total number of publications, respectively and (c) journals published in a given country had a greater number of papers published by authors of that country than by authors of other countries. Furthermore, three clusters for these 18 journals were identified that included the topics of agronomy, interactions between agronomy and soil sciences, and interactions between agronomy and plant sciences. The results of this study provide valuable insights regarding the current state of and future development trends in agronomic journals.
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.SCITOTENV.2016.05.142
Abstract: The Earth's Critical Zone, where physical, chemical and biological systems interact, extends from the top of the canopy to the underlying bedrock. In this study, we investigated soil moisture controls on phenology and productivity of an Acacia woodland in semi-arid central Australia. Situated on an extensive sand plain with negligible runoff and drainage, the carry-over of soil moisture content (θ) in the rhizosphere enabled the delay of phenology and productivity across seasons, until conditions were favourable for transpiration of that water to prevent overheating in the canopy. Storage of soil moisture near the surface (in the top few metres) was promoted by a siliceous hardpan. Pulsed recharge of θ above the hardpan was rapid and depended upon precipitation amount: 150mm storm(-1) resulted in saturation of θ above the hardpan (i.e., formation of a temporary, discontinuous perched aquifer above the hardpan in unconsolidated soil) and immediate carbon uptake by the vegetation. During dry and inter-storm periods, we inferred the presence of hydraulic lift from soil storage above the hardpan to the surface due to (i) regular daily drawdown of θ in the reservoir that accumulates above the hardpan in the absence of drainage and evapotranspiration (ii) the dimorphic root distribution wherein most roots were found in dry soil near the surface, but with significant root just above the hardpan and (iii) synchronisation of phenology amongst trees and grasses in the dry season. We propose that hydraulic redistribution provides a small amount of moisture that maintains functioning of the shallow roots during long periods when the surface soil layer was dry, thereby enabling Mulga to maintain physiological activity without diminishing phenological and physiological responses to precipitation when conditions were favourable to promote canopy cooling.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 08-2009
Publisher: Elsevier BV
Date: 04-2022
DOI: 10.1016/J.CLAE.2020.12.065
Abstract: To determine how Meibomian gland (MG) morphology affects MG function by means of gland expression with the effect of treatment. Fifteen patients (aged 31.6 ± 13.1 years) from a dry eye clinic diagnosed with MG dysfunction had their 365 lower lid MGs visualised with a slit-l biomicroscopy. Using infrared meibography (Oculus K5m), MG length, width and tortuosity were objectively measured. Each MG was expressed and the meibum graded (0=clear fluid, 1=cloudy fluid, 2= particulate fluid, 3=inspissated, or 4 = no expression) to determine its functionality. Participants had functionality repeated each time following a sequence of a warm compress, debridement, and forcible expression after 5 min. Just over 10 % of complete length MGs gave clear expression, while about 5% did not express at all, with most expressed meibum being particulate in nature. In contrast, the majority of partial length glands gave inspissated expression (38 %), with 32 % not expressing at all. No MG of <10 % length expressed. MG gland length was correlated with gland expression (r=-0.507, p < 0.001) and MG tortuosity (r=-0.129, p < 0.001), but not MG width (r=-0.090, p = 0.167). Regardless of MG length, warm compress increased the quality of expression (p < 0.002). Debridement further improved expression in partial MGs (p = 0.003), but not forcible expression (p = 0.529). Length is the key functional morphology metric of lower lid MGs. Warm compress and massage increase the quality of expression in all, but the shortest glands and patients with partial length glands also benefit from debridement.
Publisher: Wiley
Date: 26-02-2013
DOI: 10.1111/GCB.12145
Abstract: Quantifying soil organic carbon (SOC) dynamics at a high spatial and temporal resolution in response to different agricultural management practices and environmental conditions can help identify practices that both sequester carbon in the soil and sustain agricultural productivity. Using an agricultural systems model (the Agricultural Production Systems sIMulator), we conducted a high spatial resolution and long-term (122 years) simulation study to identify the key management practices and environmental variables influencing SOC dynamics in a continuous wheat cropping system in Australia's 96 million ha cereal-growing regions. Agricultural practices included five nitrogen application rates (0-200 kg N ha(-1) in 50 kg N ha(-1) increments), five residue removal rates (0-100% in 25% increments), and five residue incorporation rates (0-100% in 25% increments). We found that the change in SOC during the 122-year simulation was influenced by the management practices of residue removal (linearly negative) and fertilization (nonlinearly positive) - and the environmental variables of initial SOC content (linearly negative) and temperature (nonlinearly negative). The effects of fertilization were strongest at rates up to 50 kg N ha(-1) , and the effects of temperature were strongest where mean annual temperatures exceeded 19 °C. Reducing residue removal and increasing fertilization increased SOC in most areas except Queensland where high rates of SOC decomposition caused by high temperature and soil moisture negated these benefits. Management practices were particularly effective in increasing SOC in south-west Western Australia - an area with low initial SOC. The results can help target agricultural management practices for increasing SOC in the context of local environmental conditions, enabling farmers to contribute to climate change mitigation and sustaining agricultural production.
Publisher: Copernicus GmbH
Date: 10-12-2014
DOI: 10.5194/ACP-14-13097-2014
Abstract: Abstract. In the absence of high-resolution estimates of the components of surface energy balance for China, we developed an algorithm based on the surface energy balance system (SEBS) to generate a data set of land-surface energy and water fluxes on a monthly timescale from 2001 to 2010 at a 0.1 × 0.1° spatial resolution by using multi-satellite and meteorological forcing data. A remote-sensing-based method was developed to estimate canopy height, which was used to calculate roughness length and flux dynamics. The land-surface flux data set was validated against "ground-truth" observations from 11 flux tower stations in China. The estimated fluxes correlate well with the stations' measurements for different vegetation types and climatic conditions (average bias = 11.2 Wm−2, RMSE = 22.7 Wm−2). The quality of the data product was also assessed against the GLDAS data set. The results show that our method is efficient for producing a high-resolution data set of surface energy flux for the Chinese landmass from satellite data. The validation results demonstrate that more accurate downward long-wave radiation data sets are needed to be able to estimate turbulent fluxes and evapotranspiration accurately when using the surface energy balance model. Trend analysis of land-surface radiation and energy exchange fluxes revealed that the Tibetan Plateau has undergone relatively stronger climatic change than other parts of China during the last 10 years. The capability of the data set to provide spatial and temporal information on water-cycle and land–atmosphere interactions for the Chinese landmass is examined. The product is free to download for studies of the water cycle and environmental change in China.
Publisher: Frontiers Media SA
Date: 24-04-2020
Publisher: Elsevier BV
Date: 04-2022
DOI: 10.1016/J.SCITOTENV.2021.152878
Abstract: Localized fertilization of phosphorus has potential benefits in achieving higher crop productivity and nutrient use efficiency, but the underlying biological mechanisms of interactions between soil microorganisms and related metabolic cycle remain largely to be recognized. Here, we combined microbiology with non-target metabolomics to explore how P fertilizer levels and fertilization patterns affect wheat soil microbial communities and metabolic functions based on high-throughput sequencing and UPLC-MS/MS platforms. The results showed P fertilizer decreased the ersity of bacterial 16S rRNA genes and fungal ITS genes, and it did significantly change both soil bacterial and fungal overall community structures and compositions. The P levels and patterns also interfered with complexity of soil bacterial and fungal symbiosis networks. Moreover, metabolomics analysis showed that P fertilizer significantly changed soil metabolite spectrum, and the differential metabolites were significantly enriched to 7 main metabolic pathways, such as arginine and proline metabolism, biosynthesis of plant hormones, amino acids, plant secondary metabolites, and alkaloids derived from ornithine. Additionally, microbes also were closely related to the accumulation of metabolites through correlation analysis. Our results indicated that localized appropriate phosphorus fertilizer plays an important role in regulating soil microbial metabolism, and their interactions in soil providing valuable information for understanding how the changed phosphorus management practices affect the complex biological processes and the adaption capacity of plants to environments.
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.CLAE.2018.06.003
Abstract: To evaluate the patient-administered Optrex Eighty-seven participants aged 38 ± 17 years, (44 female) were screened for DED using the Tear Film and Ocular Surface Society Dry Eye Workshop II (TFOS DEWS II) diagnostic criteria. In addition to symptoms screening with the Ocular Surface Disease Index questionnaire (≥13 cut-off score for DED), these criteria required a sign of loss of homeostasis of the tear film in the form of a non-invasive tear breakup time (NIBUT) 8 (Tearlab), or ocular surface staining (>5 fluorescein corneal spots, >9 lissamine green spots or lid wiper staining [≥2 mm length & ≥25% width]) to confirm a diagnosis of DED. The self-administered Blink Test, which requires the participant to observe an image on a computer screen and report the length of time (in seconds) that they can refrain from blinking without discomfort, was repeated three times. Using a cut-off time of 10 s, the Blink Test demonstrated sensitivity of 66%, specificity of 88%, and an area under the curve of 0.77 (p < 0.001), in predicting a diagnosis of DED according to the TFOS DEWS II criteria. The correlation between the Blink Test and NIBUT was r = 0.47 (p < 0.001). When combined with the screening questionnaire, the sensitivity and specificity of the Blink Test increased to 71% and 90%, respectively. The Blink Test offers health professionals without advanced instrumentation, as well as patients, themselves, a rapid method of identifying possible DED.
Publisher: Copernicus GmbH
Date: 24-10-2017
Abstract: Abstract. The savanna complex is a highly erse global biome that occurs within the seasonally dry tropical to sub-tropical equatorial latitudes and are structurally and functionally distinct from grasslands and forests. Savannas are open-canopy environments that encompass a broad demographic continuum, often characterised by a changing dominance between C3-tree and C4-grass vegetation, where frequent environmental disturbances such as fire modulates the balance between ephemeral and perennial life forms. Climate change is projected to result in significant changes to the savanna floristic structure, with increases to woody biomass expected through CO2 fertilisation in mesic savannas and increased tree mortality expected through increased rainfall interannual variability in xeric savannas. The complex interaction between vegetation and climate that occurs in savannas has traditionally challenged terrestrial biosphere models (TBMs), which aim to simulate the interaction between the atmosphere and the land surface to predict responses of vegetation to changing in environmental forcing. In this review, we examine whether TBMs are able to adequately represent savanna fluxes and what implications potential deficiencies may have for climate change projection scenarios that rely on these models. We start by highlighting the defining characteristic traits and behaviours of savannas, how these differ across continents and how this information is (or is not) represented in the structural framework of many TBMs. We highlight three dynamic processes that we believe directly affect the water use and productivity of the savanna system: phenology, root-water access and fire dynamics. Following this, we discuss how these processes are represented in many current-generation TBMs and whether they are suitable for simulating savanna fluxes.Finally, we give an overview of how eddy-covariance observations in combination with other data sources can be used in model benchmarking and intercomparison frameworks to diagnose the performance of TBMs in this environment and formulate road maps for future development. Our investigation reveals that many TBMs systematically misrepresent phenology, the effects of fire and root-water access (if they are considered at all) and that these should be critical areas for future development. Furthermore, such processes must not be static (i.e. prescribed behaviour) but be capable of responding to the changing environmental conditions in order to emulate the dynamic behaviour of savannas. Without such developments, however, TBMs will have limited predictive capability in making the critical projections needed to understand how savannas will respond to future global change.
Publisher: Elsevier BV
Date: 10-2008
Publisher: Elsevier BV
Date: 03-2022
Publisher: Inter-Research Science Center
Date: 03-05-2017
DOI: 10.3354/CR01458
Publisher: Wiley
Date: 12-11-2019
DOI: 10.1002/LDR.3146
Publisher: Elsevier BV
Date: 07-2020
Publisher: Elsevier BV
Date: 11-2014
Publisher: Wiley
Date: 27-07-2018
DOI: 10.1002/JOC.5705
Publisher: Springer Science and Business Media LLC
Date: 22-11-2020
Publisher: MDPI AG
Date: 10-05-2019
Abstract: An important but rarely studied aspect of crop modeling is the uncertainty associated with model calibration and its effect on model prediction. Biomass and grain yield data from a four-year maize experiment (2008–2011) with six irrigation treatments were ided into subsets by either treatments (Calibration-by-Treatment) or years (Calibration-by-Year). These subsets were then used to calibrate crop cultivar parameters in CERES (Crop Environment Resource Synthesis)-Maize implemented within RZWQM2 (Root Zone Water Quality Model 2) using the automatic Parameter ESTimation (PEST) algorithm to explore model calibration uncertainties. After calibration for each subset, PEST also generated 300 cultivar parameter sets by assuming a normal distribution of each parameter within their reported values in the literature, using the Latin hypercube s ling (LHS) method. The parameter sets that produced similar goodness of fit (11–164 depending on subset used for calibration) were then used to predict all the treatments and years of the entire dataset. Our results showed that the selection of calibration datasets greatly affected the calibrated crop parameters and their uncertainty, as well as prediction uncertainty of grain yield and biomass. The high variability in model prediction of grain yield and biomass among the six (Calibration-by-Treatment) or the four (Calibration-by-Year) scenarios indicated that parameter uncertainty should be considered in calibrating CERES-Maize with grain yield and biomass data from different irrigation treatments, and model predictions should be provided with confidence intervals.
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.SCITOTENV.2022.153343
Abstract: Many models were established to estimate gross primary production (GPP) of terrestrial ecosystems based on vegetation light use efficiency (LUE). Analysing the spatial-temporal variations of global terrestrial GPP became capable with the increasing length of satellite data. Previous studies mainly focused on evaluating the model performance or investigating the mean, the temporal trend or the interannual variability (IAV) of global terrestrial GPP based on one single or multiple models, which is difficult to identify common merits of a same cluster of GPP models. This study compared eight satellite-based LEU-type GPP models in capturing the mean, temporal trend and IAV of global GPP concurrently. Our results showed that current common-used models based on LUE methodology estimated global mean GPP ranging from 128.5 to 158.3 Pg C year
Location: Spain
Location: United Kingdom of Great Britain and Northern Ireland
Location: China
Location: China
Location: China
Location: United States of America
Start Date: 2019
End Date: 2023
Funder: National Natural Science Foundation of China
View Funded Activity