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Effects of different representations of stomatal conductance response to humidity across the African continent under warmer CO 2 ‐enriched climate conditions
Author(s) -
Sato Hisashi,
Kumagai Tomo'omi,
Takahashi Atsuhiro,
Katul Gabriel G.
Publication year - 2015
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2014jg002838
Subject(s) - stomatal conductance , humidity , environmental science , conductance , atmospheric sciences , relative humidity , climate change , climatology , skin conductance , meteorology , geography , geology , oceanography , botany , biology , mathematics , photosynthesis , medicine , combinatorics , biomedical engineering
Abstract General circulation models (GCMs) forecast higher global vapor pressure deficit (VPD) but unchanged global relative humidity (RH) in future climates. A literature survey revealed that 50% of Earth system models and land surface models embedded within GCMs employ RH as an atmospheric aridity index when describing stomatal conductance ( gs ), whereas the remaining 50% employ VPD. The consequences of using RH or VPD in gs models for water cycling and vegetation productivity in future climates on large spatial and temporal scales remain to be explored. Process‐based global dynamic vegetation model runs, changes in the hydrological cycle, and concomitant vegetation productivity for the 21st century projected climate were conducted by altering only gs responses to VPD or RH and not changing any other formulations. In the simulations of the African continent under a 21st century warming trend, both stomatal functions of VPD and RH resulted in similar geographic patterns in gross primary production (GPP). However, continental total GPP was larger for the VPD response than that for the RH response. Transpiration rates were lower, resulting in a 13% increase in water‐use efficiency for the VPD response compared with its RH counterpart.