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Atmosphere‐Soil Interactions Govern Ecosystem Flux Sensitivity to Environmental Conditions in Semiarid Woody Ecosystems Over Varying Timescales
Author(s) -
SamuelsCrow Kimberly E.,
Ogle Kiona,
Litvak Marcy E.
Publication year - 2020
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2019jg005554
Subject(s) - environmental science , ecosystem , evapotranspiration , vapour pressure deficit , carbon sink , woodland , sink (geography) , juniper , soil water , atmospheric sciences , hydrology (agriculture) , ecology , transpiration , soil science , geography , geology , chemistry , biochemistry , photosynthesis , cartography , geotechnical engineering , biology
Water and CO 2 flux responses (e.g., evapotranspiration [ET] and net ecosystem exchange [NEE]) to environmental conditions can provide insights into how climate change will affect the terrestrial water and carbon budgets, especially in sensitive semiarid ecosystems. Here, we evaluated sensitivity of daily ET and NEE to current and antecedent (past) environment conditions, including atmospheric (vapor pressure deficit [VPD] and air temperature [T air ]) and moisture (precipitation and soil water) drivers. We focused on two common southwestern U.S. (“Southwest”) biomes: pinyon‐juniper woodland ( Pinus edulis , Juniperus monosperma ) and ponderosa pine forest ( Pinus ponderosa ). Due to differences in aridity, rooting patterns, and plant physiological strategies (stomatal and hydraulic traits), we expected ET and NEE in these ecosystems to respond differently to atmospheric and moisture drivers, with longer response timescales in the drier pinyon‐juniper woodland. Net sensitivity to drivers varied temporally in both ecosystems, reflecting the integrated influence of interacting drivers and antecedent precipitation patterns. NEE sensitivity to VPD and soil moisture (and ET sensitivity to deep soil moisture [S deep ]) was higher in the ponderosa forest. ET and NEE in both ecosystems responded almost instantaneously to T air , VPD, and shallow soil moisture (S shall ), and increases in any of these drivers weakened the carbon sink and enhanced water loss. Conversely, S deep and precipitation influenced ET and NEE over longer timescales (days to months, respectively), and higher S deep enhanced the carbon sink. As climate changes, these results suggest hotter and drier conditions will weaken the carbon sink and exacerbate water loss from Southwest pinyon‐juniper and ponderosa ecosystems.