ORCID Profile
0000-0002-3503-4783
Current Organisation
University of Oxford
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Publisher: Springer Science and Business Media LLC
Date: 04-2021
DOI: 10.1038/S41559-021-01418-Y
Abstract: The forests of Amazonia are among the most bio erse plant communities on Earth. Given the immediate threats posed by climate and land-use change, an improved understanding of how this extraordinary bio ersity is spatially organized is urgently required to develop effective conservation strategies. Most Amazonian tree species are extremely rare but a few are common across the region. Indeed, just 227 'hyperdominant' species account for >50% of all in iduals >10 cm diameter at 1.3 m in height. Yet, the degree to which the phenomenon of hyperdominance is sensitive to tree size, the extent to which the composition of dominant species changes with size class and how evolutionary history constrains tree hyperdominance, all remain unknown. Here, we use a large floristic dataset to show that, while hyperdominance is a universal phenomenon across forest strata, different species dominate the forest understory, midstory and canopy. We further find that, although species belonging to a range of phylogenetically dispersed lineages have become hyperdominant in small size classes, hyperdominants in large size classes are restricted to a few lineages. Our results demonstrate that it is essential to consider all forest strata to understand regional patterns of dominance and composition in Amazonia. More generally, through the lens of 654 hyperdominant species, we outline a tractable pathway for understanding the functioning of half of Amazonian forests across vertical strata and geographical locations.
Publisher: Wiley
Date: 28-11-2021
DOI: 10.1111/GCB.15982
Abstract: A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long‐term climate averages (mean climate) drive spatial variations in species’ baseline growth rates, whereas deviations from these averages over time (anomalies) can create growth variation around the local baseline. However, the rarity of long‐term tree census data spanning climatic gradients has so far limited our understanding of their respective role, especially in tropical systems. Furthermore, tree growth sensitivity to climate is likely to vary widely among species, and the ecological strategies underlying these differences remain poorly understood. Here, we utilize an exceptional dataset of 49 years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how multiannual tree growth responds to both climate means and anomalies, and how species’ functional traits mediate these growth responses to climate. We show that anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast‐growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both climate means and anomalies. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests and that species traits can provide insights into understanding these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.
Publisher: Cold Spring Harbor Laboratory
Date: 06-03-2020
DOI: 10.1101/2020.03.05.978858
Abstract: Many global environmental agendas, including halting bio ersity loss, reversing land degradation, and limiting climate change, depend upon retaining forests with high ecological integrity, yet the scale and degree of forest modification remains poorly quantified and mapped. By integrating data on observed and inferred human pressures and an index of lost connectivity, we generate the first globally-consistent, continuous index of forest condition as determined by degree of anthropogenic modification. Globally, only 17.4 million km 2 of forest (40.5%) have high landscape level integrity (mostly found in Canada, Russia, the Amazon, Central Africa and New Guinea) and only 27% of this area is found in nationally-designated protected areas. Of the forest in protected areas, only 56% has high landscape level integrity. Ambitious policies that prioritize the retention of forest integrity, especially in the most intact areas, are now urgently needed alongside current efforts aimed at halting deforestation and restoring the integrity of forests globally.
Publisher: Springer Science and Business Media LLC
Date: 16-05-2022
DOI: 10.1038/S41559-022-01747-6
Abstract: Tropical forests are some of the most bio erse ecosystems in the world, yet their functioning is threatened by anthropogenic disturbances and climate change. Global actions to conserve tropical forests could be enhanced by having local knowledge on the forests' functional ersity and functional redundancy as proxies for their capacity to respond to global environmental change. Here we create estimates of plant functional ersity and redundancy across the tropics by combining a dataset of 16 morphological, chemical and photosynthetic plant traits s led from 2,461 in idual trees from 74 sites distributed across four continents together with local climate data for the past half century. Our findings suggest a strong link between climate and functional ersity and redundancy with the three trait groups responding similarly across the tropics and climate gradient. We show that drier tropical forests are overall less functionally erse than wetter forests and that functional redundancy declines with increasing soil water and vapour pressure deficits. Areas with high functional ersity and high functional redundancy tend to better maintain ecosystem functioning, such as aboveground biomass, after extreme weather events. Our predictions suggest that the lower functional ersity and lower functional redundancy of drier tropical forests, in comparison with wetter forests, may leave them more at risk of shifting towards alternative states in face of further declines in water availability across tropical regions.
Publisher: Wiley
Date: 21-10-2023
Publisher: Hindawi Limited
Date: 12-2019
DOI: 10.1155/2019/1347208
Abstract: During the menopausal period, women have a higher tendency to develop obesity and any other metabolic syndromes. Dysregulation of leptin and kisspeptin signaling as anorexigenic agents is believed to be the connection between metabolic disorders and altered reproductive function. Therefore, this study aimed at investigating the association between leptin, soluble leptin receptor (sOBR), free leptin index, kisspeptin concentrations, and body mass index (BMI) in postmenopausal women. A cross-sectional study was carried out among 171 postmenopausal women aged 40–75 years from 2017 to 2018. Subjects were assigned into 2 groups according to their BMIs: obese group (84 subjects) and nonobese group (87 subjects). In addition to anthropometric measurement, blood s le was collected from each subject for leptin, sOBR, free leptin index (FLI), and kisspeptin evaluation. Bivariate and correlation analysis discovered that leptin and FLI were positively correlated with BMI, while sOBR and kisspeptin were negatively correlated with BMI. Among those variables, multivariate analysis found that leptin, sOBR, and kisspeptin were independently associated with obesity. Therefore, it can be concluded that higher serum leptin concentration and FLI, as well as lower serum sOBR and kisspeptin concentrations, are significantly associated with obesity in postmenopausal women.
Publisher: Springer Science and Business Media LLC
Date: 26-04-2023
DOI: 10.1038/S41586-023-05971-3
Abstract: Tropical forests face increasing climate risk 1,2 , yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for ex le, $$\\varPsi $$ Ψ 50 ) and hydraulic safety margins (for ex le, HSM 50 ) are important predictors of drought-induced mortality risk 3–5 , little is known about how these vary across Earth’s largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters $$\\varPsi $$ Ψ 50 and HSM 50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both $$\\varPsi $$ Ψ 50 and HSM 50 influence the biogeographical distribution of Amazon tree species. However, HSM 50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM 50 are gaining more biomass than are low HSM 50 forests. We propose that this may be associated with a growth–mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM 50 in the Amazon 6,7 , with strong implications for the Amazon carbon sink.
Publisher: Wiley
Date: 23-11-2021
Abstract: Allometric equations for calculation of tree above‐ground biomass ( AGB ) form the basis for estimates of forest carbon storage and exchange with the atmosphere. While standard models exist to calculate forest biomass across the tropics, we lack a standardized tool for computing AGB across boreal and temperate regions that comprise the global extratropics. Here we present an integrated R package, allodb , containing systematically selected published allometric equations and proposed functions to compute AGB . The data component of the package is based on 701 woody species identified at 24 large Forest Global Earth Observatory (ForestGEO) forest dynamics plots representing a wide ersity of extratropical forests. A total of 570 parsed allometric equations to estimate in idual tree biomass were retrieved, checked and combined using a weighting function designed to ensure optimal equation selection over the full tree size range with smooth transitions across equations. The equation dataset can be customized with built‐in functions that subset the original dataset and add new equations. Although equations were curated based on a limited set of forest communities and number of species, this resource is appropriate for large portions of the global extratropics and can easily be expanded to cover novel forest types.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-10-2019
Abstract: More complete accounting reveals how intact tropical forest loss plays a larger-than-realized role in exacerbating climate change.
Publisher: Wiley
Date: 03-2022
DOI: 10.1111/BTP.13069
Abstract: Rock‐derived nutrients such as calcium (Ca), magnesium (Mg), phosphorus (P), and potassium (K) are essential plant resources, yet depleted in highly weathered tropical soils, leading to nutrient limitation of productivity or other ecosystem processes. Despite this, substantial amounts of rock‐derived nutrients occur within wood, which raises questions about the role that wood nutrients play in the ecology of tropical forests. Using data from forests across the tropics, we quantify wood nutrient stocks at in idual tree and ecosystem levels. At the ecosystem level, we show that tropical wood can store substantial amounts of rock‐derived nutrients. Furthermore, on a tree level, tree species vary widely in woody nutrient concentrations. These observations raise important questions as to the biogeochemical or ecological drivers that lead to this variability, as well as the role that woody tissue plays in the buffering and cycling of nutrients. We offer some potential explanations and direction for future research to explore this under‐appreciated but sizable store of inorganic nutrients in tropical biomass.
Publisher: Springer Science and Business Media LLC
Date: 09-11-2020
DOI: 10.1038/S41467-020-18996-3
Abstract: The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality.
Publisher: Springer Science and Business Media LLC
Date: 10-10-2019
DOI: 10.1038/S41597-019-0196-1
Abstract: Forest biomass is an essential indicator for monitoring the Earth’s ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world’s forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities.
Publisher: The Royal Society
Date: 08-10-2018
Abstract: To understand the impacts of extreme climate events, it is first necessary to understand the spatio-temporal characteristics of the event. Gridded climate products are frequently used to describe climate patterns but have been shown to perform poorly over data-sparse regions such as tropical forests. Often, they are uncritically employed in a wide range of studies linking tropical forest processes to large-scale climate variability. Here, we conduct an inter-comparison and assessment of near-surface air temperature fields supplied by four state-of-the-art reanalysis products, along with precipitation estimates supplied by four merged satellite-gauge rainfall products. Firstly, spatio-temporal patterns of temperature and precipitation anomalies during the 2015–2016 El Niño are shown for each product to characterize the impact of the El Niño on the tropical forest biomes of Equatorial Africa, Southeast Asia and South America. Using meteorological station data, a two-stage assessment is then conducted to determine which products most reliably model tropical climates during the 2015–2016 El Niño, and which perform best over the longer-term satellite observation period (1980–2016). Results suggest that eastern Amazonia, parts of the Congo Basin and mainland Southeast Asia all experienced significant monthly mean temperature anomalies during the El Niño, while northeastern Amazonia, eastern Borneo and southern New Guinea experienced significant precipitation deficits. Our results suggest ERA-Interim and MERRA2 are the most reliable air temperature datasets, while TRMM 3B42 V7 and CHIRPS v2.0 are the best-performing rainfall datasets. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.
Publisher: MDPI AG
Date: 07-2023
DOI: 10.3390/RS15133374
Abstract: In intelligent traffic control systems, the features extracted by loop detectors are insufficient to accurately impute missing data. Most of the existing imputation methods use only these extracted features, which leads to the construction of data models that cannot fulfill the required accuracy. This deficiency is the main motivation to propose an enrichment imputation method for loop detectors namely EIM-LD, in which the imputation accuracy is increased for different missing patterns and ratios by introducing a data enrichment technique using statistical multi-class labeling. It first enriches the clean data by adding a statistical multi-class label, including C1…Cn classes. Then, the class of s les in the missed-volume data is labeled using the best data model constructed from the labeled clean data by five different classifiers. Experts of the traffic control department in Isfahan city determined classes of the statistical multi-class label for n = 5 (class labels), and we also developed subclass labels (n = 20) since the number of s les in the subclass labels was sufficient. Next, the enriched data are ided into n datasets, each of them is imputed independently using various imputation methods, and their results are finally merged. To evaluate the impact of using the proposed method, the original data, including missing volumes, are first imputed without our enrichment method. Then, the proposed method’s accuracy is evaluated by considering two class labels and subclass labels. The experimental and statistical results prove that the proposed EIM-LD method can enrich the real data collected by loop detectors, by which the comparative imputation methods construct a more accurate data model. In addition, using subclass labels further enhances the imputation method’s accuracy.
Publisher: Springer Science and Business Media LLC
Date: 04-01-2021
DOI: 10.1038/S41467-020-20537-X
Abstract: A Correction to this paper has been published: 0.1038/s41467-020-20537-x
Publisher: Wiley
Date: 31-08-2020
DOI: 10.1111/NPH.16830
Abstract: Leaf venation networks evolved along several functional axes, including resource transport, damage resistance, mechanical strength, and construction cost. Because functions may depend on architectural features at different scales, network architecture may vary across spatial scales to satisfy functional tradeoffs. We develop a framework for quantifying network architecture with multiscale statistics describing elongation ratios, circularity ratios, vein density, and minimum spanning tree ratios. We quantify vein networks for leaves of 260 southeast Asian tree species in s les of up to 2 cm 2 , pairing multiscale statistics with traits representing axes of resource transport, damage resistance, mechanical strength, and cost. We show that these multiscale statistics clearly differentiate species’ architecture and delineate a phenotype space that shifts at larger scales functional linkages vary with scale and are weak, with vein density, minimum spanning tree ratio, and circularity ratio linked to mechanical strength (measured by force to punch) and elongation ratio and circularity ratio linked to damage resistance (measured by tannins) and phylogenetic conservatism of network architecture is low but scale‐dependent. This work provides tools to quantify the function and evolution of venation networks. Future studies including primary and secondary veins may uncover additional insights.
Publisher: Cold Spring Harbor Laboratory
Date: 09-06-2021
DOI: 10.1101/2021.06.08.447571
Abstract: A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long-term climate averages (mean climate) and short-term deviations from these averages (anomalies) both influence tree growth, but the rarity of long-term data integrating climatic gradients with tree censuses has so far limited our understanding of their respective role, especially in tropical systems. Here, we combined 49 years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how tree growth responds to both climate means and anomalies, and how species functional traits mediate these tree growth responses to climate. We showed that short-term, anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast-growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both long-term and short-term climate variations. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests, and that species traits can be leveraged to understand these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.
Publisher: Wiley
Date: 20-09-2018
DOI: 10.1111/NPH.15444
Abstract: Plant functional traits regulate ecosystem functions but little is known about how co-occurring gradients of land use and edaphic conditions influence their expression. We test how gradients of logging disturbance and soil properties relate to community-weighted mean traits in logged and old-growth tropical forests in Borneo. We studied 32 physical, chemical and physiological traits from 284 tree species in eight 1 ha plots and measured long-term soil nutrient supplies and plant-available nutrients. Logged plots had greater values for traits that drive carbon capture and growth, whilst old-growth forests had greater values for structural and persistence traits. Although disturbance was the primary driver of trait expression, soil nutrients explained a statistically independent axis of variation linked to leaf size and nutrient concentration. Soil characteristics influenced trait expression via nutrient availability, nutrient pools, and pH. Our finding, that traits have dissimilar responses to land use and soil resource availability, provides robust evidence for the need to consider the abiotic context of logging when predicting plant functional ersity across human-modified tropical forests. The detection of two independent axes was facilitated by the measurement of many more functional traits than have been examined in previous studies.
Publisher: F1000 Research Ltd
Date: 23-01-2019
DOI: 10.12688/F1000RESEARCH.17058.1
Abstract: Background: Endometriosis is one of the most common conditions causing infertility and an indication to undergo in vitro fertilization (IVF). High apoptosis rate and oxidative stress in patients with endometriosis are believed to negatively affect the IVF success rate. However, there have been conflicting results on the effect of endometriosis on IVF success, and there have been limited studies that directly assess endometriosis and its effect on oocyte quality. This study was performed to explore the correlation between mRNA BAX/BCL-2 expression and oocyte quality in endometriosis compared to non-endometriosis subjects. Methods: This was a cross-sectional study. 15 endometriosis and 15 non-endometriosis subjects were recruited through convenience s ling at Cipto Mangunkusumo Hospital, Jakarta. All subjects underwent follicle stimulation with recombinant follicle-stimulating hormone (FSH). Granulosa cells were collected and tested for BAX and BCL-2 expression and the results were compared to the oocyte quality and fertilization rate of the patients. Results: The total dose of recombinant FSH received by the endometriosis group was significantly higher compared with that of the non-endometriosis group (p = 0.005). There was a difference in BAX level (p = 0.029) and BCL-2 level (p .001) between groups. However, the BAX/BCL-2 ratio did not differ significantly (p = 0.787) between groups. No significant correlation was found between the BAX/BCL-2 ratio and any of the oocyte quality parameters measured. Conclusion: We found that there is a significantly higher dose in total dose recombinant FSH received by the endometriosis group compared with the non-endometriosis group. We also found that there was no significant difference in BAX/BCL-2 ratio between the endometriosis and non-endometriosis groups.
Publisher: Springer Science and Business Media LLC
Date: 09-2023
Publisher: Cold Spring Harbor Laboratory
Date: 11-12-2022
DOI: 10.1101/2022.12.07.518693
Abstract: Above Ground Biomass (AGB) is an important metric used to quantify the mass of carbon stored in terrestrial ecosystems. For forests, this is routinely estimated at the plot scale (typically ≥1 ha) using inventory measurements and allometry. In recent years, Terrestrial Laser Scanning (TLS) has appeared as a disruptive technology that can generate a more accurate assessment of tree and plot scale AGB however, operationalising TLS methods has had to overcome a number of challenges. One such challenge is the segmentation of in idual trees from plot level point clouds that are required to estimate woody volume, this is often done manually (e.g. with interactive point cloud editing software) and can be very time consuming. Here we present TLS2trees , an automated processing pipeline and set of Python command line tools that aims to redress this processing bottleneck. TLS2trees consists of existing and new methods and is specifically designed to be horizontally scalable. The processing pipeline is demonstrated across 10 plots of 7 forest types from open savanna to dense tropical rainforest, where a total of 10,557 trees are segmented. TLS2trees segmented trees are compared to 1,281 manually segmented trees. Results indicate that TLS2trees performs well, particularly for larger trees (i.e. the cohort of largest trees that comprise 50% of total plot volume), where plot-wise tree volume bias is ±0.4 m 3 and %RMSE is ~ 60%. To facilitate improvements to the presented methods as well as modification for other laser scanning modes (e.g. mobile and UAV laser scanning), TLS2trees is a free and open-source software (FOSS).
Publisher: Wiley
Date: 05-12-2021
Abstract: Tropical forests are the most productive terrestrial ecosystems, fixing over 40 Pg of carbon from the atmosphere each year. A substantial portion of this carbon is allocated below‐ground to roots and root‐associated micro‐organisms. However, there have been very few empirical studies on the dynamics of this below ground transfer, especially in tropical forests where carbon allocation processes are influenced by high plant species ersity. We used a whole‐stand girdling experiment to halt the below‐ground transfer of recent photosynthates in a lowland tropical forest in Borneo. By girdling 209 large trees in a 0.48 ha plot, we determined: (a) the contribution of recent photosynthate to root‐rhizosphere respiration and (b) the relationships among the disruption of this below‐ground carbon supply, tree species composition and mortality. Mortality of the 209 trees was 62% after 370 days, with large variation among species and particularly high mortality within the Dipterocarpaceae (99%) and Fagaceae (100%) families. We also observed a higher risk of mortality following girdling for species with lower wood density. Soil CO 2 emissions declined markedly (36 ± 5%) over ~50 days following girdling in three of six monitored subplots. In the other three subplots there was either a marginal decline or no response of soil CO 2 emissions to girdling. The decrease in soil CO 2 efflux was larger in subplots with dominance of Dipterocarpaceae. Synthesis . Our results indicate high spatial variation in the coupling of below‐ground carbon allocation and root‐rhizosphere respiration in this tropical forest, with a closer coupling in forest dominated by Dipterocarpaceae. Our findings highlight the implications of tree species composition of tropical forests in affecting the dynamics of below‐ground carbon transfer and its release to the atmosphere.
Publisher: Cold Spring Harbor Laboratory
Date: 18-12-2022
DOI: 10.1101/2022.12.15.520573
Abstract: Tropical forests are threatened by degradation and deforestation but the consequences for these ecosystems are poorly understood, particularly at the landscape scale. We present the most extensive ecosystem analysis to date of the impacts of logging and conversion of tropical forest to oil palm from a large-scale study in Borneo, synthesizing responses from 79 variables categorized into four hierarchical ecological ‘levels’: 1) structure and environment, 2) species traits, 3) bio ersity and 4) ecosystem functions. Variables at the lowest levels that were directly impacted by the physical processes of timber extraction, such as soil characteristics, were sensitive to even moderate amounts of logging, whereas bio ersity and ecosystem functions proved remarkably resilient to logging in many cases, but were more affected by conversion to oil palm plantation. Logging tropical forest mostly impacts structure while bio ersity and functions are more vulnerable to habitat conversion
Publisher: Springer Science and Business Media LLC
Date: 23-09-2020
Publisher: Wiley
Date: 31-05-2021
DOI: 10.1111/GCB.15677
Abstract: Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also h ered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old‐growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi‐deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia ( n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stronger when we considered the fractional allocation of total NPP to fine roots, demonstrating that understanding allocation adds explanatory power to understanding fine root productivity and total NPP. Fine root residence time was a function of multiple factors: soil sand content, soil pH, and maximum water deficit, with longest residence times in acidic, sandy, and water‐stressed soils. In tropical montane forests, on the other hand, a different set of relationships prevailed, highlighting the very different nature of montane and lowland forest biomes. Root productivity was a strong positive linear function of mean annual temperature, root residence time was a strong positive function of soil nitrogen content in montane forests, and lastly decreasing soil P content increased allocation of productivity to fine roots. In contrast to the lowlands, environmental conditions were a better predictor for fine root productivity than for fractional allocation of total NPP to fine roots, suggesting that root productivity is a particularly strong driver of NPP allocation in tropical mountain regions.
Publisher: Springer Science and Business Media LLC
Date: 25-05-2021
DOI: 10.1038/S41467-021-23236-3
Abstract: Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta- ersity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta- ersity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta- ersity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta- ersity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta- ersity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest bio ersity.
Publisher: Springer Science and Business Media LLC
Date: 08-12-2020
DOI: 10.1038/S41467-020-19493-3
Abstract: Many global environmental agendas, including halting bio ersity loss, reversing land degradation, and limiting climate change, depend upon retaining forests with high ecological integrity, yet the scale and degree of forest modification remain poorly quantified and mapped. By integrating data on observed and inferred human pressures and an index of lost connectivity, we generate a globally consistent, continuous index of forest condition as determined by the degree of anthropogenic modification. Globally, only 17.4 million km 2 of forest (40.5%) has high landscape-level integrity (mostly found in Canada, Russia, the Amazon, Central Africa, and New Guinea) and only 27% of this area is found in nationally designated protected areas. Of the forest inside protected areas, only 56% has high landscape-level integrity. Ambitious policies that prioritize the retention of forest integrity, especially in the most intact areas, are now urgently needed alongside current efforts aimed at halting deforestation and restoring the integrity of forests globally.
Publisher: American Geophysical Union (AGU)
Date: 03-2017
DOI: 10.1002/2016JG003615
Publisher: Wiley
Date: 16-11-2022
DOI: 10.1111/GCB.16501
Abstract: “Least‐cost theory” posits that C 3 plants should balance rates of photosynthetic water loss and carboxylation in relation to the relative acquisition and maintenance costs of resources required for these activities. Here we investigated the dependency of photosynthetic traits on climate and soil properties using a new Australia‐wide trait dataset spanning 528 species from 67 sites. We tested the hypotheses that plants on relatively cold or dry sites, or on relatively more fertile sites, would typically operate at greater CO 2 drawdown (lower ratio of leaf internal to ambient CO 2 , C i : C a ) during light‐saturated photosynthesis, and at higher leaf N per area (N area ) and higher carboxylation capacity ( V cmax 25 ) for a given rate of stomatal conductance to water vapour, g sw . These results would be indicative of plants having relatively higher water costs than nutrient costs. In general, our hypotheses were supported. Soil total phosphorus (P) concentration and (more weakly) soil pH exerted positive effects on the N area – g sw and V cmax 25 – g sw slopes, and negative effects on C i : C a . The P effect strengthened when the effect of climate was removed via partial regression. We observed similar trends with increasing soil cation exchange capacity and clay content, which affect soil nutrient availability, and found that soil properties explained similar amounts of variation in the focal traits as climate did. Although climate typically explained more trait variation than soil did, together they explained up to 52% of variation in the slope relationships and soil properties explained up to 30% of the variation in in idual traits. Soils influenced photosynthetic traits as well as their coordination. In particular, the influence of soil P likely reflects the Australia's geologically ancient low‐relief landscapes with highly leached soils. Least‐cost theory provides a valuable framework for understanding trade‐offs between resource costs and use in plants, including limiting soil nutrients.
Publisher: F1000 Research Ltd
Date: 04-01-2019
DOI: 10.12688/F1000RESEARCH.17036.1
Abstract: Background: This study was performed to evaluate the role of luteinizing hormone (LH) and granulosa cell LH receptor (LH-R) in poor responder patients who underwent controlled ovarian stimulation. Expression levels of LH-R mRNA in granulosa cells was investigated and compared with oocyte morphology, oocyte maturity and fertilization rate. Methods: Granulosa cells were obtained from 30 patients who underwent in vitro fertilization (IVF) at Dr. Cipto Mangunkusumo Hospital, Jakarta. The patients were ided into two groups: group I (n=10) poor responders and group II (n=20) non-poor responders. After the extraction of total RNA from granulosa cells, semi-quantitative RT-PCR was performed and the amount of LH-R mRNA was quantified. The relative values were calculated as the ratio of LH-R mRNA and actin beta mRNA. Statistical analysis was performed using Mann-Whitney test and Spearman correlation. Results: The relative value of LH-R mRNA was higher in group I compared with group II (27.37[0.00-28939.37] vs 0.00[0.00-7196.12]). Oocyte maturity (r=0.267) and morphology (r=0.267) in group I consistently showed a positive correlation with LH-R mRNA in group II a negative correlation with LH-R mRNA was shown for oocyte maturity (r= -0.552) and morphology (r= -0.164). Group I had a positive correlation between LH-R expression with fertilization rate (r=0.430), and group II showed a negative correlation (r=-0.340). Conclusions: The expression of LH-R mRNA has a positive correlation with oocyte quality in poor responder patients and a negative correlation in non-poor responders. Our study suggests an optimal expression of LH- R mRNA in granulosa cells during controlled ovarian stimulation to obtain good quality oocytes.
Publisher: Wiley
Date: 06-2021
Abstract: Forest degradation through logging is pervasive throughout the world's tropical forests, leading to changes in the three‐dimensional canopy structure that have profound consequences for wildlife, microclimate and ecosystem functioning. Quantifying these structural changes is fundamental to understanding the impact of degradation, but is challenging in dense, structurally complex forest canopies. We exploited discrete‐return airborne LiDAR surveys across a gradient of logging intensity in Sabah, Malaysian Borneo, and assessed how selective logging had affected canopy structure (Plant Area Index, PAI, and its vertical distribution within the canopy). LiDAR products compared well to independent, analogue models of canopy structure produced from detailed ground‐based inventories undertaken in forest plots, demonstrating the potential for airborne LiDAR to quantify the structural impacts of forest degradation at landscape scale, even in some of the world's tallest and most structurally complex tropical forests. Plant Area Index estimates across the plot network exhibited a strong linear relationship with stem basal area ( R 2 = 0.95). After at least 11–14 years of recovery, PAI was ~28% lower in moderately logged plots and ~52% lower in heavily logged plots than that in old‐growth forest plots. These reductions in PAI were associated with near‐complete lack of trees ‐m tall, which had not been fully compensated for by increasing plant area lower in the canopy. This structural change drives a marked reduction in the ersity of canopy environments, with the deep, dark understorey conditions characteristic of old‐growth forests far less prevalent in logged sites. Full canopy recovery is likely to take decades. Synthesis and applications . Effective management and restoration of tropical forests requires detailed monitoring of the forest and its environment. We demonstrate that airborne LiDAR can effectively map the canopy architecture of the complex tropical forests of Borneo, capturing the three‐dimensional impact of degradation on canopy structure at landscape scales, therefore facilitating efforts to restore and conserve these ecosystems.
Publisher: Wiley
Date: 30-06-2023
DOI: 10.1111/GCB.16821
Abstract: For more than three decades, major efforts in s ling and analyzing tree ersity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species ersity in the wetter western and northern Amazon forests. By contrast, little attention has been paid to patterns and drivers of ersity in the largest canopy and emergent trees, which is surprising given these have dominant ecological functions. Here, we use a machine learning approach to quantify the importance of environmental factors and apply it to generate spatial predictions of the species ersity of all trees (dbh ≥ 10 cm) and for very large trees (dbh ≥ 70 cm) using data from 243 forest plots (108,450 trees and 2832 species) distributed across different forest types and biogeographic regions of the Brazilian Amazon. The ersity of large trees and of all trees was significantly associated with three environmental factors, but in contrasting ways across regions and forest types. Environmental variables associated with disturbances, for ex le, the lightning flash rate and wind speed, as well as the fraction of photosynthetically active radiation, tend to govern the ersity of large trees. Upland rainforests in the Guiana Shield and Roraima regions had a high ersity of large trees. By contrast, variables associated with resources tend to govern tree ersity in general. Places such as the province of Imeri and the northern portion of the province of Madeira stand out for their high ersity of species in general. Climatic and topographic stability and functional adaptation mechanisms promote ideal conditions for species ersity. Finally, we mapped general patterns of tree species ersity in the Brazilian Amazon, which differ substantially depending on size class.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-05-2020
Abstract: A key uncertainty in climate change models is the thermal sensitivity of tropical forests and how this value might influence carbon fluxes. Sullivan et al. measured carbon stocks and fluxes in permanent forest plots distributed globally. This synthesis of plot networks across climatic and biogeographic gradients shows that forest thermal sensitivity is dominated by high daytime temperatures. This extreme condition depresses growth rates and shortens the time that carbon resides in the ecosystem by killing trees under hot, dry conditions. The effect of temperature is worse above 32°C, and a greater magnitude of climate change thus risks greater loss of tropical forest carbon stocks. Nevertheless, forest carbon stocks are likely to remain higher under moderate climate change if they are protected from direct impacts such as clearance, logging, or fires. Science , this issue p. 869
Publisher: Springer Science and Business Media LLC
Date: 23-08-2023
Publisher: IOP Publishing
Date: 30-09-2019
Abstract: The El Niño Southern Oscillation (ENSO) is a major driver of seasonal and interannual climatic variability across the tropics. The 2015/16 El Niño event was one of the strongest El Niño events of the past century. Here we characterize the meteorological impacts of the 2015/16 El Niño event upon the terrestrial tropics, and place the severity of this event into context of previous strong events in 1982/83 and 1997/98. Strong drought-inducing meteorological anomalies (≥2 s.d.) occurred across vast regions (20%) of the terrestrial tropics, where the wet tropics (≥1200 mm yr −1 ) were more severely affected (33%) than the drier tropics (6%). Central and eastern Amazonia experienced the most sustained and spatially extensive drought inducing anomalies, while parts of the Congo basin and Insular Southeast Asia also experienced severe drought. Surprisingly, some regions of the tropics (e.g. the Guiana Shield) with well known ENSO teleconnections were only briefly affected by the 2015/16 El Niño event. 2015/16 El Niño soil water drought impacts affected 29% of the terrestrial tropics, compared to 16% and 18% in 1982/83 and 1997/98, respectively. Maximum temperatures were particularly exacerbated compared to previous strong El Niños because they were lified by the warming trend due to anthropogenic climate change. This also intensified positive anomalies of atmospheric vapor pressure deficit (the atmospheric demand for moisture), which had strongly negative consequences for vegetation productivity in the tropics. Even if El Niño events do not increase in intensity over coming decades, the pervasive long-term warming trend means that the atmospheric drought impact of each strong El Niño is becoming more severe, and many parts of the tropics will experience novel climate (temperature and VPD) conditions with each new strong El Niño event.
Publisher: F1000 Research Ltd
Date: 08-04-2019
DOI: 10.12688/F1000RESEARCH.17894.1
Abstract: Background: Good reproductive health is important for in iduals and also for the development of children. Knowledge plays an important role in women’s reproduction health. Our study examined women’s perspectives and knowledge of reproductive health after using the free Jakarta Reproduction Sehat (Jakpros) application (app) on a daily basis for two weeks. Methods: Our study used a cross-sectional, qualitative design. The s le consisted of 12 participants from two sub-district general hospitals in Jakarta. Participants were chosen using purposive s ling and consisted of women of reproductive age who had completed previous questionnaires on their use of Jakpros. We used descriptive analytics and a qualitative method. Data were collected by direct observation in small focus group discussions. Results: Participants said that after they used the Jakpros app, they were more aware of their reproductive health. Their knowledge increased after counselling combined with Jakpros usage. They also said that the features in the app made it easier to contact their doctor and to access their nearest hospital. Conclusion: Jakpros is a convenient way to access reliable reproductive health information.
Publisher: Springer Science and Business Media LLC
Date: 18-05-2022
DOI: 10.1038/S41586-022-04737-7
Abstract: Evidence exists that tree mortality is accelerating in some regions of the tropics
Publisher: Springer Science and Business Media LLC
Date: 11-11-2019
DOI: 10.1038/S41559-019-1007-Y
Abstract: Higher levels of taxonomic and evolutionary ersity are expected to maximize ecosystem function, yet their relative importance in driving variation in ecosystem function at large scales in erse forests is unknown. Using 90 inventory plots across intact, lowland, terra firme, Amazonian forests and a new phylogeny including 526 angiosperm genera, we investigated the association between taxonomic and evolutionary metrics of ersity and two key measures of ecosystem function: aboveground wood productivity and biomass storage. While taxonomic and phylogenetic ersity were not important predictors of variation in biomass, both emerged as independent predictors of wood productivity. Amazon forests that contain greater evolutionary ersity and a higher proportion of rare species have higher productivity. While climatic and edaphic variables are together the strongest predictors of productivity, our results show that the evolutionary ersity of tree species in erse forest stands also influences productivity. As our models accounted for wood density and tree size, they also suggest that additional, unstudied, evolutionarily correlated traits have significant effects on ecosystem function in tropical forests. Overall, our pan-Amazonian analysis shows that greater phylogenetic ersity translates into higher levels of ecosystem function: tropical forest communities with more distantly related taxa have greater wood productivity.
Publisher: Springer Science and Business Media LLC
Date: 20-01-2021
DOI: 10.1038/S41467-021-20999-7
Abstract: A Correction to this paper has been published: 0.1038/s41467-021-20999-7.
Publisher: Wiley
Date: 26-07-2018
DOI: 10.1111/NPH.15338
Abstract: Insect herbivores cause substantial changes in the leaves they attack, but their effects on the ecophysiology of neighbouring, nondamaged leaves have never been quantified in natural canopies. We studied how winter moth (Operophtera brumata), a common herbivore in temperate forests, affects the photosynthetic and isoprene emission rates of its host plant, the pedunculate oak (Quercus robur). Through a manipulative experiment, we measured leaves on shoots damaged by caterpillars or mechanically by cutting, or left completely intact. To quantify the effects at the canopy scale, we surveyed the extent and patterns of leaf area loss in the canopy. Herbivory reduced photosynthesis both in damaged leaves and in their intact neighbours. Isoprene emission rates significantly increased after mechanical leaf damage. When scaled up to canopy-level, herbivory reduced photosynthesis by 48 ± 10%. The indirect effects of herbivory on photosynthesis in undamaged leaves (40%) were much more important than the direct effects of leaf area loss (6%). If widespread across other plant-herbivore systems, these findings suggest that insect herbivory has major and previously underappreciated influences in modifying ecosystem carbon cycling, with potential effects on atmospheric chemistry.
Publisher: Wiley
Date: 21-10-2020
DOI: 10.1111/NPH.16866
Abstract: Atmospheric carbon dioxide concentration ([CO 2 ]) is increasing, which increases leaf‐scale photosynthesis and intrinsic water‐use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO 2 ] increase and thus climate change. However, ecosystem CO 2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO 2 ]‐driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO 2 ] (iCO 2 ) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre‐industrial times. Established theory, supported by experiments, indicates that iCO 2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO 2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO 2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO 2 , albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change.
Publisher: Springer Science and Business Media LLC
Date: 25-08-2021
DOI: 10.1038/S41586-021-03728-4
Abstract: Tropical forests store 40-50 per cent of terrestrial vegetation carbon
Publisher: Wiley
Date: 22-12-2020
DOI: 10.1111/BTP.12901
Abstract: Do tropical trees close to death have a distinct change to their leaf spectral signature? Tree mortality rates have been increasing in tropical forests, reducing the global carbon sink. Upcoming hyperspectral satellites could be used to predict regions close to experiencing extensive tree mortality during periods of stress, such as drought. Here we show, for a tropical rainforest in Borneo, how imminent tropical tree mortality impacts leaf physiological traits and reflectance. We measured leaf reflectance (400–2500 nm), light‐saturated photosynthesis (A sat ), leaf dark respiration (R dark ), leaf mass area (LMA), and % leaf water across five c aigns in a six‐month period during which there were two causes of tree mortality: a major natural drought and a co‐incident tree stem girdling treatment. We find that prior to mortality, there were significant ( p 0.05) leaf spectral changes in the red (650–700 nm), the NIR (1,000–1,400 nm), and SWIR bands (2,000–2,400 nm) and significant reductions in the potential carbon balance of the leaves (increased R dark and reduced A sat ). We show that the partial least squares regression technique can predict mortality in tropical trees across different species and functional groups with medium precision but low accuracy ( r 2 of .65 and RMSE/mean of 0.58). However, most tree death in our study was due to girdling, which is not a natural form of death. More research is needed to determine if this spectroscopy technique can be applied to tropical forests in general.
Publisher: The Royal Society
Date: 08-10-2018
Abstract: Meteorological extreme events such as El Niño events are expected to affect tropical forest net primary production (NPP) and woody growth, but there has been no large-scale empirical validation of this expectation. We collected a large high–temporal resolution dataset (for 1–13 years depending upon location) of more than 172 000 stem growth measurements using dendrometer bands from across 14 regions spanning Amazonia, Africa and Borneo in order to test how much month-to-month variation in stand-level woody growth of adult tree stems (NPP stem ) can be explained by seasonal variation and interannual meteorological anomalies. A key finding is that woody growth responds differently to meteorological variation between tropical forests with a dry season (where monthly rainfall is less than 100 mm), and aseasonal wet forests lacking a consistent dry season. In seasonal tropical forests, a high degree of variation in woody growth can be predicted from seasonal variation in temperature, vapour pressure deficit, in addition to anomalies of soil water deficit and shortwave radiation. The variation of aseasonal wet forest woody growth is best predicted by the anomalies of vapour pressure deficit, water deficit and shortwave radiation. In total, we predict the total live woody production of the global tropical forest biome to be 2.16 Pg C yr −1 , with an interannual range 1.96–2.26 Pg C yr −1 between 1996–2016, and with the sharpest declines during the strong El Niño events of 1997/8 and 2015/6. There is high geographical variation in hotspots of El Niño–associated impacts, with weak impacts in Africa, and strongly negative impacts in parts of Southeast Asia and extensive regions across central and eastern Amazonia. Overall, there is high correlation ( r = −0.75) between the annual anomaly of tropical forest woody growth and the annual mean of the El Niño 3.4 index, driven mainly by strong correlations with anomalies of soil water deficit, vapour pressure deficit and shortwave radiation. This article is part of the discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Yadvinder Malhi.