Satellite-based assessment of water use and leaf area efficiencies of dryland conifer forests along an aridity gradient

Moshe Dubinin; Yagil Osem; Dan Yakir; Tarin Paz-Kagan

doi:10.1016/j.scitotenv.2023.165977

Satellite-based assessment of water use and leaf area efficiencies of dryland conifer forests along an aridity gradient

Sci Total Environ. 2023 Dec 1:902:165977. doi: 10.1016/j.scitotenv.2023.165977. Epub 2023 Aug 2.

Authors

Moshe Dubinin¹, Yagil Osem², Dan Yakir³, Tarin Paz-Kagan⁴

Affiliations

¹ Earth and Planetary Sciences Department, Weizmann Institute, Rehovot, Israel; Department of Natural Resources, Institute of Plant Sciences, Agricultural Research Organization, Volcani Center, Israel; French Associates Institute for Agriculture and Biotechnology of Dryland, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 8499000, Israel.
² Department of Natural Resources, Institute of Plant Sciences, Agricultural Research Organization, Volcani Center, Israel.
³ Earth and Planetary Sciences Department, Weizmann Institute, Rehovot, Israel.
⁴ French Associates Institute for Agriculture and Biotechnology of Dryland, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 8499000, Israel. Electronic address: tarin@bgu.ac.il.

PMID: 37541509
DOI: 10.1016/j.scitotenv.2023.165977

Abstract

Dryland forests worldwide are increasingly threatened by drought stress due to climate change. Understanding the relationships between forest structure and function is essential for managing dryland forests to adapt to these changes. We investigated the structure-function relationships in four dryland conifer forests distributed along a semiarid to subhumid climatic aridity gradient. Forest structure was represented by leaf area index (LAI) and function by gross primary productivity (GPP), evapotranspiration (ET), and the derived efficiencies of water use (WUE = GPP/ET) and leaf area (LAE = GPP/LAI). Estimates of GPP and ET were based on the observed relationships between high-resolution vegetation indices from VENμS and Sentinel-2A satellites and flux data from three eddy covariance towers in the study regions between November 2015 to October 2018. The red-edge-based MERIS Terrestrial Chlorophyll Index (MTCI) from VENμS and Sentinel-2A showed strong correlations to flux tower GPP and ET measurements for the three sites (R²_cal > 0.91, R²_val > 0.84). Using our approach, we showed that as LAI decreased with decreasing aridity index (AI) (i.e., dryer conditions), estimated GPP and ET decreased (R² > 0.8 to LAI), while WUE (R² = 0.68 to LAI) and LAE increased. The observed global-scale patterns are associated with a variety of forest vegetation characteristics, at the local scale, such as tree species composition and density. However, our results point towards a canopy-level mechanism, where the ecosystem-LAI and resultant proportion of sun-exposed vs. shaded leaves are primary determinants of WUE and LAE along the studied climatic aridity gradient. This work demonstrates the importance of high-resolution (spatially and spectrally) remote sensing data conjugated with flux tower data for monitoring dryland forests and understanding the intricate structure-function interactions in their response to drying conditions.

Keywords: Eddy covariance; Evapotranspiration (ET); Gross primary productivity (GPP); MODIS; Sentinel-2A; VENμS.

MeSH terms

Ecosystem*
Forests
Photosynthesis
Plant Leaves / physiology
Seasons
Tracheophyta*
Water

Substances

Water