Detecting forest response to droughts with global observations of vegetation water content

Global Change Biology, Journal Year: 2021, Volume and Issue: 27(23), P. 6005 - 6024

Published: Sept. 3, 2021

Droughts in a warming climate have become more common and extreme, making understanding forest responses to water stress increasingly pressing. Analysis of trees has long focused on potential xylem leaves, which influences stomatal closure flow through the soil-plant-atmosphere continuum. At same time, changes vegetation content (VWC) are linked range tree responses, including fluxes carbon, mortality, flammability, more. Unlike potential, requires demanding situ measurements, VWC can be retrieved from remote sensing particularly at microwave frequencies using radar radiometry. Here, we highlight key frontiers significantly increase our stress. To validate observations landscape scale better relate them data assimilation model parameters, introduce an ecosystem-scale analog pressure-volume curve, non-linear relationship between average leaf or branch commonly used plant hydraulics. The sources variability these curves their response discussed. We further show what extent diel, seasonal, decadal dynamics reflect variations different processes relating also for inferring belowground conditions-which difficult impossible observe directly. Lastly, discuss how dedicated geostationary spaceborne observational system VWC, when combined with existing datasets, capture diel seasonal advance science applications global vulnerability future droughts.

Language: Английский

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Increasing and widespread vulnerability of intact tropical rainforests to repeated droughts

Proceedings of the National Academy of Sciences, Journal Year: 2022, Volume and Issue: 119(37)

Published: Sept. 6, 2022

Intact tropical rainforests have been exposed to severe droughts in recent decades, which may threaten their integrity, ability sequester carbon, and capacity provide shelter for biodiversity. However, response remains uncertain due limited high-quality, long-term observations covering extensive areas. Here, we examined how the upper canopy of intact has responded drought events globally during past 3 decades. By developing a long pantropical time series (1992 2018) monthly radar satellite observations, show that repeated caused sustained decline signal 93%, 84%, 88% Americas, Africa, Asia, respectively. Sudden decreases were detected around 1997–1998, 2005, 2010, 2015 Americas; 1999–2000, 2004–2005, 2010–2011, Africa; 2006, Asia. Rainforests showed similar low resistance (the maintain predrought condition when occurs) across continents, but American consistently lowest resilience return after event). Moreover, while is decreasing, albeit weakly Africa forest not increased significantly. Our results therefore suggest withstand future limited. This negative implications climate change mitigation through forest-based solutions associated pledges made by countries under Paris Agreement.

Language: Английский

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Leaf angle as a leaf and canopy trait: Rejuvenating its role in ecology with new technology

Ecology Letters, Journal Year: 2023, Volume and Issue: 26(6), P. 1005 - 1020

Published: April 20, 2023

Abstract Life on Earth depends the conversion of solar energy to chemical by plants through photosynthesis. A fundamental challenge in optimizing photosynthesis is adjust leaf angles efficiently use intercepted sunlight under constraints heat stress, water loss and competition. Despite importance angle, until recently, we have lacked data frameworks describe predict angle dynamics their impacts leaves globe. We review role studies ecophysiology, ecosystem ecology earth system science, highlight essential yet understudied as an ecological strategy regulate plant carbon–water–energy nexus bridge leaf, canopy processes. Using two models, show that variations significant not only canopy‐scale photosynthesis, balance efficiency but also light competition within forest canopy. New techniques measure are emerging, opening opportunities understand rarely‐measured intraspecific, interspecific, seasonal interannual implications biology science. conclude proposing three directions for future research.

Language: Английский

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Investigating Diurnal and Seasonal Cycles of Vegetation Optical Depth Retrieved From GNSS Signals in a Broadleaf Forest

Geophysical Research Letters, Journal Year: 2024, Volume and Issue: 51(6)

Published: March 19, 2024

Abstract Vegetation Optical Depth (VOD) has emerged as a valuable metric to quantify water stress on vegetation's carbon uptake from remote sensing perspective. However, existing spaceborne microwave platforms face limitations in capturing the diurnal VOD variations and global products lack site‐level validation against plant physiology. To address these challenges, we leveraged Global Navigation Satellite System (GNSS) L‐band signal, measuring its attenuation by canopy of temperate broadleaf forest using pair GNSS receivers. This approach allowed us collect continuous observations at sub‐hourly scale. We found significant seasonal‐scale correlation between leaf potential. The amplitude is affected soil moisture, transpiration surface water. Additionally, can help independently estimate transpiration. Our findings pave way for deeper understanding response vegetation finer temporal scales.

Language: Английский

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Monitoring and Modeling the Soil‐Plant System Toward Understanding Soil Health

Reviews of Geophysics, Journal Year: 2025, Volume and Issue: 63(1)

Published: Jan. 25, 2025

Abstract The soil health assessment has evolved from focusing primarily on agricultural productivity to an integrated evaluation of biota and biotic processes that impact properties. Consequently, shifted a predominantly physicochemical approach incorporating ecological, biological molecular microbiology indicators. This shift enables comprehensive exploration microbial community properties their responses environmental changes arising climate change anthropogenic disturbances. Despite the increasing availability indicators (physical, chemical, biological) data, holistic mechanistic linkage not yet been fully established between functions across multiple spatiotemporal scales. article reviews state‐of‐the‐art monitoring, understanding how soil‐microbiome‐plant contribute feedback mechanisms causes in properties, as well these have functions. Furthermore, we survey opportunities afforded by soil‐plant digital twin approach, integrative framework amalgamates process‐based models, Earth Observation data assimilation, physics‐informed machine learning, achieve nuanced comprehension health. review delineates prospective trajectory for monitoring embracing systematically observe model system. We further identify gaps opportunities, provide perspectives future research enhanced intricate interplay hydrological processes, hydraulics, microbiome, landscape genomics.

Language: Английский

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The influence of surface canopy water on the relationship between L-band backscatter and biophysical variables in agricultural monitoring

Remote Sensing of Environment, Journal Year: 2021, Volume and Issue: 268, P. 112789 - 112789

Published: Nov. 10, 2021

The presence of surface water on the canopy affects radar backscatter. However, its influence relationship between backscatter and crop biophysical parameters has not been investigated. aim this study was to quantify (SCW) L-band variables interest in agricultural monitoring. In study, we investigated effect SCW co- cross-polarized backscatter, cross ratios (VH/VV HV/HH), vegetation index (RVI) dry biomass, content (VWC), plant height leaf area (LAI). addition, estimated optical depth (VOD) with internal VWC analysis based data collected during a field experiment Florida, USA 2018. A corn scanned truck-mounted, fully polarimetric, along continuous monitoring (dew, interception) soil moisture every 15 min for 58 days. pre-dawn destructive sampling conducted measure biomass. Results showed that can increase up 2 dB lower (CRs) RVI. Spearman's rank correlations observables were, average, 0.2 higher compared wet vegetation. VOD from generally than those vegetation, which led different fitting parameter (so-called b) values linear fit VWC. results presented here underscore importance considering retrieval particular, they highlight overpass time, impact daily patterns dew interception have interest.

Language: Английский

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Reliability of using vegetation optical depth for estimating decadal and interannual carbon dynamics

Remote Sensing of Environment, Journal Year: 2022, Volume and Issue: 285, P. 113390 - 113390

Published: Nov. 30, 2022

Vegetation optical depth (VOD) from satellite passive microwave sensors has enabled monitoring of aboveground biomass carbon dynamics by building a relationship with static maps over space and then applying this to VOD time series. However, uncertainty in arises changes water stress, as is mainly determined vegetation content, which varies at diurnal interannual scales, depends on both relative moisture content. Here, we studied the reliability using various frequencies temporal aggregation methods for estimating decadal global scale. We used variations represent magnitude content buffering caused climatic constant amount dry carbon. This was evaluate likelihood reflecting changes. found that SMOS-IC L-VOD LPDR X-VOD can be reliably estimate 76.7% 69.9% vegetated land surface, respectively, yet cautious use warranted some areas such eastern Amazon rainforest. Moreover, annual aggregated 95% percentile nighttime retrievals proved most suitable parameter among methods. Finally, validated comparing between adjacent years against eddy covariance estimations gross primary production flux sites several cover classes across globe. Despite large difference spatial scales them, positive correlation obtained supports capability quantifying dynamics.

Language: Английский

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Seasonal variations in vegetation water content retrieved from microwave remote sensing over Amazon intact forests

Remote Sensing of Environment, Journal Year: 2022, Volume and Issue: 285, P. 113409 - 113409

Published: Dec. 14, 2022

Language: Английский

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Continuous ground monitoring of vegetation optical depth and water content with GPS signals

Biogeosciences, Journal Year: 2023, Volume and Issue: 20(9), P. 1789 - 1811

Published: May 16, 2023

Abstract. Satellite microwave remote sensing techniques can be used to monitor vegetation optical depth (VOD), a metric which is directly linked biomass and water content. However, these large-scale measurements are still difficult reference against either rare or not comparable field observations. So far, in situ estimates of canopy status often rely on infrequent time-consuming destructive samples, necessarily representative the scale. Here, we present simple technique based Global Navigation Systems (GNSS) with potential bridge this persisting scale gap. Because GNSS signals attenuated scattered by liquid water, placing sensor under vegetated measuring changes signal strength over time provide continuous information about VOD thus We test at forested site southern California for period 8 months. show that variations signal-to-noise ratios reflect overall distribution density monitored continuously. For first time, resolve diurnal content hourly sub-hourly steps. Using model transmissivity assess signals, find temperature effects dielectric constant, VOD, may non-negligible during extreme events like heat waves. Sensitivity rainfall dew deposition also suggests interception approach. The presented here has two important knowledge gaps, namely lack ground truth observations satellite-based need reliable proxy extrapolate isolated labor-intensive biomass, content, leaf potential. recommendations deploying such off-the-shelf easy-to-use systems existing ecohydrological monitoring networks as FluxNet SapfluxNet.

Language: Английский

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Vegetation moisture estimation in the Western United States using radiometer-radar-lidar synergy

Remote Sensing of Environment, Journal Year: 2024, Volume and Issue: 303, P. 113993 - 113993

Published: Jan. 16, 2024

Monitoring vegetation moisture conditions is paramount to better understand and assess drought impacts on vegetation, enhance crop yield predictions, improve ecosystem models. Passive microwave remote sensing allows retrievals of the optical depth (VOD; [unitless]), which directly proportional water content (VWC; in units mass per unit area [kg/m2]). However, VWC largely dependent dry biomass structure imprints VOD signal. Previously, statistical models have been used isolate component from components. Physically-based approaches not yet proposed for this goal. In study, we present a multi-sensor semi-physical approach retrieve express it as Live Fuel Moisture Content (LFMC [%]; percentage unit). The study performed western United States period April 2015 – December 2018. There, situ LFMC samples are available assessment. We rely model based height data GEDI/Sentinel-2 radar backscatter Sentinel-1, account Vegetation retrieved at L-, X- Ku-bands by minimizing difference between modeled estimates SMAP (L-band) AMSR-2 (X- Ku-band) satellites. Results show that independent canopy height, land cover, backscatter, demonstrating capability algorithm separate dynamics biomass/structure VOD. reproduce well expected spatio-temporal LFMC. good agreement with regional scale, Pearson's correlations (r) 0.64 (Ku-band), 0.60 (X-band) 0.47 (L-band). Similar results obtained independently shrub forest sites Ku-bands. most comparisons estimated LFMC, biases below 10% dynamic range Performance L-band limited fact frequency senses full vertical extent canopy, while taken only top leaves much more sensitive. More insight will be needed grasslands (r = 0.44 X-band) using time-dynamic data. Furthermore, pixel-scale assessment conducted, showing > 0.6). method can tailored exploit synergies past (e.g., AMSR-E), current AMSR-2) future satellite sensors such CIMR ROSE-L global mapping different layers.

Language: Английский

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