A5039316404- Climate change and permafrost
- Atmospheric and Environmental Gas Dynamics
- Climate variability and models
- Cryospheric studies and observations
- Plant Water Relations and Carbon Dynamics
- Remote Sensing in Agriculture
- Species Distribution and Climate Change
- Wildlife Ecology and Conservation
- Fire effects on ecosystems
- Plant responses to elevated CO2
- Soil Moisture and Remote Sensing
- Low-power high-performance VLSI design
- Global Energy and Sustainability Research
- Ecology and Vegetation Dynamics Studies
- Wildlife-Road Interactions and Conservation
- Climate change impacts on agriculture
- Marine and coastal ecosystems
- Hydrology and Drought Analysis
- Biomedical Text Mining and Ontologies
- Impact of Light on Environment and Health
- Soil and Unsaturated Flow
- Remote Sensing and LiDAR Applications
- Environmental and Agricultural Sciences
- Solar Radiation and Photovoltaics
- Analog and Mixed-Signal Circuit Design
University of California, Los Angeles
2024-2025
Jet Propulsion Laboratory
2019-2024
Scripps Institution of Oceanography
2024
Space Information Laboratories (United States)
2023
University of Montana
2014-2018
Beltsville Agricultural Research Center
2016
Agricultural Research Service
2016
University of Tehran
2005-2015
Science Systems and Applications (United States)
2015
Universiti Putra Malaysia
2010-2012
Arctic-boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance terms carbon feedbacks to climate, yet the sign (sink or source) magnitude budget within recent years remains highly uncertain. Here, we provide new estimates (2003-2015) vegetation gross primary productivity (GPP), respiration (Reco ), net CO2 exchange (NEE; Reco - GPP), terrestrial methane (CH4 ) emissions for zone using...
Abstract Plant traits are both responsive to local climate and strong predictors of primary productivity. We hypothesized that future change might promote a shift in global plant resulting changes Gross Primary Productivity (GPP). characterized the relationship between key traits, namely Specific Leaf Area (SLA), height, seed mass, found by 2070, tropical arid ecosystems will be more suitable for plants with relatively lower canopy SLA while far northern latitudes favor woody taller than at...
One of the available tools for mapping geographical distribution and potential suitable habitats is species models. These techniques are very helpful finding poorly known distributions in sampled areas, such as tropics. Maximum Entropy (MaxEnt) a recently developed modeling method that can be successfully calibrated using relatively small number records. In this research, MaxEnt model was applied to describe identify key factors shaping vulnerable Malayan Sun Bear (Helarctos malayanus) one...
Abstract Satellite remote sensing observations show an increased greenness trend over land in recent decades. While can indicate productivity, estimation of total annual productivity is highly dependent on vegetation response to climate and environmental conditions. Models have been struggling determine how much carbon taken up by plants as a result atmospheric CO 2 fertilization. Current light use efficiency (LUE) models contain considerable uncertainty due the lack spatial temporal...
The National Aeronautics and Space Administration's Soil Moisture Active Passive (SMAP) mission Level 4 Carbon (L4C) product provides model estimates of the Net Ecosystem CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> exchange (NEE) incorporating SMAP soil moisture information. L4C includes NEE, computed as total ecosystem respiration less gross photosynthesis, at a daily time step posted to 9-km global grid by plant functional type....
Abstract Soil respiration (i.e. from soils and roots) provides one of the largest global fluxes carbon dioxide (CO 2 ) to atmosphere is likely increase with warming, yet magnitude soil rapidly thawing Arctic-boreal regions not well understood. To address this knowledge gap, we first compiled a new CO flux database for permafrost-affected tundra boreal ecosystems in Alaska Northwest Canada. We then used database, multi-sensor satellite imagery, random forest models assess regional...
A common assumption of remote sensing-based light use efficiency (LUE) models for estimating vegetation gross primary productivity (GPP) is that plants in a biome matrix operate at their photosynthetic capacity under optimal climatic conditions. prescribed constant maximum parameter (LUEmax) defines the carbon conversion rate these conditions and large source model uncertainty. Here we used tower eddy covariance measurement-based (CO2) fluxes spatial estimation LUE (LUEopt) across North...
Ecosystem productivity models rely on regional climatic information to estimate temperature and moisture constraints influencing plant growth. However, the response these environmental factors is uncertain at global scale has largely been defined using limited observations from sparse monitoring sites, including carbon flux towers. Recent studies have shown that satellite of Solar-Induced chlorophyll Fluorescence (SIF) are highly correlated with ecosystem Gross Primary Productivity (GPP)....
Abstract The strong El Niño Southern Oscillation ( ENSO ) event that occurred in 2015–2016 caused extreme drought the northern Brazilian Amazon, especially state of Roraima, increasing fire occurrence. Here we map extent precipitation and anomalies quantify effects climatic anthropogenic drivers on occurrence during dry season (from December 2015 to March 2016) Roraima. To achieve these objectives first estimated spatial pattern anomalies, based long‐term data from TRMM (Tropical Rainfall...
Arctic and boreal ecosystems play an important role in the global carbon (C) budget, whether they act as a future net C sink or source depends on climate environmental change. Here, we used complementary situ measurements, model simulations, satellite observations to investigate dioxide (CO2 ) seasonal cycle its climatic controls across Alaska northwestern Canada during anomalously warm winter spring conditions of 2015 2016 (relative 2010-2014). In spring, found that photosynthesis was...
Warming of northern high latitude regions (NHL, > 50 °N) has increased both photosynthesis and respiration which results in considerable uncertainty regarding the net carbon dioxide (CO2) balance NHL ecosystems. Using estimates constrained from atmospheric observations 1980 to 2017, we find that increasing trends CO2 uptake early-growing season are similar magnitude across tree cover gradient NHL. However, trend respiratory loss during late-growing increases significantly with cover,...
Abstract In the light use efficiency (LUE) approach of estimating gross primary productivity (GPP), plant is linearly related to absorbed photosynthetically active radiation assuming that plants absorb and convert solar energy into biomass within a maximum LUE (LUE max ) rate, which assumed vary conservatively given biome type. However, it has been shown photosynthetic can biomes. this study, we used 149 global CO 2 flux towers derive optimum opt under prevailing climate conditions for each...
Earth observation-based estimates of global gross primary production (GPP) are essential for understanding the response terrestrial biosphere to climatic change and other anthropogenic forcing. In this study, we attempt an ecosystem-level physiological approach estimating GPP using asymptotic light function (LRF) between incoming photosynthetically active radiation (PAR) that better represents observed at high spatiotemporal resolutions than conventional use efficiency approach. Modelled is...
Foliar traits such as specific leaf area (SLA), nitrogen (N), and phosphorus (P) concentrations play important roles in plant economic strategies ecosystem functioning.Various global maps of these foliar have been generated using statistical upscaling approaches based on in-situ trait observations.Here, we intercompare upscaled at 0.5 • spatial resolution (six for SLA, five N, three P), categorize the used to generate them, evaluate with estimates from a database vegetation plots...
Abstract Remote sensing and site-level observations have shown unprecedented changes in Arctic ecosystems owing to climate warming. These include greening browning trends vegetation as well species composition both the tundra boreal forests. Here, we leveraged solar induced chlorophyll fluorescence (SIF) study ecosystem phenology across pan-Arctic domain from 2000 2020. Ecoregions, a proxy for plants’ functional traits, were single most important variable explain spatial phenological...
Abstract Droughts are complex phenomena that typically evolve slowly over time. They originate through interactions between the atmosphere and land surface, but show delayed evolution as they cascade soil moisture, groundwater supplies, sometimes resulting in prolonged insidious impacts on regional hydrological systems. While previous studies have observed this phenomenon at select situ locations, temporal characteristics of drought cascades never been quantitatively estimated large scales...
Abstract The increase in wildfire occurrence and severity seen over the past decades boreal Arctic biomes is expected to continue future response rapid climate change this region. Recent studies documented positive trends gross primary productivity (GPP) for driven by warming, but it unclear how GPP are affected wildfires. Here, we used satellite vegetation observations environmental data with a diagnostic model analyze recovery from large fires Alaska period 2000–2019. We confirmed earlier...
Flash droughts can develop suddenly, often within just a few weeks, and are marked by rapidly depleting soil moisture intense heat stress. These conditions have devastating effects on crop growth disrupt entire ecosystems. What makes flash especially challenging is their tendency to occur during the peak growing season, leaving little time for agricultural ecological sectors prepare or mitigate losses. While lack of precipitation primary trigger, other factors like high evaporative demand,...
Foliar traits such as specific leaf area (SLA), nitrogen (N) and phosphorus (P) concentrations play an important role in plant economic strategies ecosystem functioning. Various global maps of these foliar have been generated using statistical upscaling approaches based on in-situ trait observations.Here, we intercompare upscaled at 0.5° spatial resolution (six for SLA, five N, three P), categorize the used to generate them, evaluate with estimates from a database vegetation plots...
Abstract Terrestrial ecosystem gross primary productivity (GPP) is the largest land-atmosphere carbon flux and mechanism of photosynthetic fixation atmospheric CO 2 into plant biomass. Anomalous rainfall events have been shown to a great impact on global cycle. However, less known about these GPP, especially in Africa, where situ observations are sparse. Here, we use suite satellite other geospatial data examine responses major ecosystems Africa anomalous from 2003 2017. Our results reveal...