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Leaf surface water, not plant water stress, drives diurnal variation in tropical forest canopy water content
Author(s) -
Xu Xiangtao,
Konings Alexandra G.,
Longo Marcos,
Feldman Andrew,
Xu Liang,
Saatchi Sassan,
Wu Donghai,
Wu Jin,
Moorcroft Paul
Publication year - 2021
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.17254
Subject(s) - environmental science , interception , dew , canopy , water content , diurnal temperature variation , atmospheric sciences , transpiration , seasonality , vegetation (pathology) , hydrology (agriculture) , ecology , geography , biology , botany , meteorology , photosynthesis , geology , medicine , geotechnical engineering , pathology , condensation
Summary Variation in canopy water content (CWC) that can be detected from microwave remote sensing of vegetation optical depth (VOD) has been proposed as an important measure of vegetation water stress. However, the contribution of leaf surface water (LW s ), arising from dew formation and rainfall interception, to CWC is largely unknown, particularly in tropical forests and other high‐humidity ecosystems. We compared VOD data from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) and CWC predicted by a plant hydrodynamics model at four tropical sites in Brazil spanning a rainfall gradient. We assessed how LW s influenced the relationship between VOD and CWC. The analysis indicates that while CWC is strongly correlated with VOD ( R 2 = 0.62 across all sites), LW s accounts for 61–76% of the diurnal variation in CWC despite being < 10% of CWC. Ignoring LW s weakens the near‐linear relationship between CWC and VOD and reduces the consistency in diurnal variation. The contribution of LW s to CWC variation, however, decreases at longer, seasonal to inter‐annual, time scales. Our results demonstrate that diurnal patterns of dew formation and rainfall interception can be an important driver of diurnal variation in CWC and VOD over tropical ecosystems and therefore should be accounted for when inferring plant diurnal water stress from VOD measurements.