Satellite detection of soil moisture related water stress impacts on ecosystem productivity using the MODIS-based photochemical reflectance index

Mingzhu He, John S. Kimball, Steven Running, Ashley Ballantyne, Kaiyu Guan, Fred Huemmrich
2016 Remote Sensing of Environment  
23 Satellite remote sensing provides continuous observations of vegetation properties that can be used to 24 estimate global terrestrial ecosystem gross primary production (GPP). The Photochemical Reflectance 25 Index (PRI) has been shown to be sensitive to vegetation photosynthetic light use efficiency (LUE), GPP 26 and canopy water-stress. Here, we use the NASA EOS MODIS (Moderate Resolution Imaging 27 Spectroradiometer) based PRI with eddy covariance CO 2 flux measurements and meteorological
more » ... 28 observations from 20 tower sites representing major plant functional type (PFT) classes within the 29 continental USA (CONUS) to assess GPP sensitivity to soil moisture related water stress. The sPRI (scaled 30 PRI) metric derived using MODIS band 13 as a reference channel (sPRI 13 ) shows generally higher 31 correspondence with tower GPP observations than other potential MODIS reference bands. The sPRI 13 32 observations were used as a proxy for soil moisture related water supply constraints to LUE within a 33 satellite data driven terrestrial carbon flux model to estimate GPP (GPP PRI ). The GPP PRI calculations show 34 generally favorable correspondence with tower GPP observations (0.457 ≤ R 2 ≤ 0.818), except for lower 35 GPP PRI performance over evergreen needleleaf forest (ENF) sites. A regional model sensitivity analysis 36 using the sPRI 13 as a water supply proxy indicated that water restrictions limit GPP over more than 21% 37 of the CONUS domain, particularly in drier climate areas where atmospheric moisture (VPD) deficits 38 alone are insufficient to represent both atmosphere demand and water supply controls affecting 39 productivity. Our results indicate strong potential of the MODIS sPRI 13 to represent soil moisture related 40 water supply controls influencing photosynthesis, with enhanced (1-km resolution) delineation of these 41 processes closer to the scale of in situ tower observations. These observations may provide an effective 42 tool for characterizing sub-grid spatial heterogeneity in soil moisture related controls that inform 43 coarser scale observations and estimates determined from other satellite observations and global 44 carbon, and climate models. 45
doi:10.1016/j.rse.2016.08.019 fatcat:gtdrdrbmpzgj7fmojymaarotgq