ORCID Profile
0000-0003-4010-6814
Current Organisations
Canada Centre for Remote Sensing
,
Beijing Normal University
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Publisher: Copernicus GmbH
Date: 07-09-2022
DOI: 10.5194/ESSD-14-4077-2022
Abstract: Abstract. The maximum rate of Rubisco carboxylation (Vcmax) determines leaf photosynthetic capacity and is a key parameter for estimating the terrestrial carbon cycle, but its spatial information is lacking, hindering global ecological research. Here, we convert leaf chlorophyll content (LCC) retrieved from satellite data to Vcmax, based on plants' optimal distribution of nitrogen between light harvesting and carboxylation pathways. We also derive Vcmax from satellite (GOME-2) observations of sun-induced chlorophyll fluorescence (SIF) as a proxy of leaf photosynthesis using a data assimilation technique. These two independent global Vcmax products agree well (r2=0.79,RMSE=15.46µmol m−2 s−1, P .001) and compare well with 3672 ground-based measurements (r2=0.69,RMSE=13.8µmol m−2 s−1 and P .001 for SIF r2=0.55,RMSE=18.28µmol m−2 s−1 and P .001 for LCC). The LCC-derived Vcmax product is also used to constrain the retrieval of Vcmax from TROPical Ozone Mission (TROPOMI) SIF data to produce an optimized Vcmax product using both SIF and LCC information. The global distributions of these products are compatible with Vcmax computed from an ecological optimality theory using meteorological variables, but importantly reveal additional information on the influence of land cover, irrigation, soil pH, and leaf nitrogen on leaf photosynthetic capacity. These satellite-based approaches and spatial Vcmax products are primed to play a major role in global ecosystem research. The three remote sensing Vcmax products based on SIF, LCC, and SIF+LCC are available at 0.5281/zenodo.6466968 (Chen et al., 2022), and the code for implementing the ecological optimality theory is available at github.com/SmithEcophysLab/optimal_vcmax_R and 0.5281/zenodo.5899564 (last access: 31 August 2022) (Smith et al., 2022).
Publisher: MDPI AG
Date: 05-01-2023
DOI: 10.3390/RS15020313
Abstract: Fugitive dust arising from mining operations in the Arctic can be a concern to surrounding communities. The Mary River Mine operation on northwest Baffin Island in the Qikiqtani region, Nunavut, is one ex le. Yet, the short and long-term impacts of fugitive dust remain poorly understood. Dust lowers snow albedo which can contribute to early snowmelt. This influences the spring snowmelt freshet period, significant to the land-atmosphere interactions, hydrology, ecology, and socioeconomic activities in the Arctic. Here, we map dust extents indicated by snow discoloration and examine for areas of early snowmelt using a 21-year MODIS time series snow cover product in 2000–2020. We found an episode of dust plume extended far beyond the reference dust s ler sites from where Nil dustfall is detected. A snow albedo decrease of 0.014 was seen more than 60 km away from the mine site. Incidents of early snowmelt existed extensively and progressively prior to the Mary River Mine operations however, localized and even earlier snowmelt also appear around Mine’s operations we estimated that the snow-off date was advanced by one week and three weeks for the background, and areas around the Mine facilities, respectively, during the 21-year period. Furthermore, the area increase in early snowmelt around the Mine facilities correlates to ore production growth. This study demonstrates rapid changes in early snowmelt beyond observed regional trends when additional drivers are introduced.
Publisher: Elsevier BV
Date: 2020
Publisher: Natural Resources Canada/CMSS/Information Management
Date: 2020
DOI: 10.4095/326159
Publisher: Elsevier BV
Date: 12-2021
No related grants have been discovered for Liming He.