Open AccessVegetation productivity responds to sub‐annual climate conditions across semiarid biomes
Author(s) -
Barnes Mallory L.,
Moran M. Susan,
Scott Russell L.,
Kolb Thomas E.,
PonceCampos Guillermo E.,
Moore David J. P.,
Ross Morgan A.,
Mitra Bhaskar,
Dore Sabina
Publication year - 2016
Publication title -
ecosphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.255
H-Index - 57
ISSN - 2150-8925
DOI - 10.1002/ecs2.1339
Subject(s) - biome , shrubland , environmental science , precipitation , enhanced vegetation index , primary production , evapotranspiration , vegetation (pathology) , climate change , ecosystem , moderate resolution imaging spectroradiometer , growing season , productivity , grassland , climatology , atmospheric sciences , ecology , normalized difference vegetation index , geography , satellite , vegetation index , biology , medicine , macroeconomics , pathology , aerospace engineering , geology , meteorology , engineering , economics
Abstract In the southwest United States, the current prolonged warm drought is similar to the predicted future climate change scenarios for the region. This study aimed to determine patterns in vegetation response to the early 21st century drought across multiple biomes. We hypothesized that different biomes (forests, shrublands, and grasslands) would have different relative sensitivities to both climate drivers (precipitation and temperature) and legacy effects (previous‐year's productivity). We tested this hypothesis at eight Ameriflux sites in various Southwest biomes using NASA Moderate‐resolution Imaging Spectroradiometer Enhanced Vegetation Index ( EVI ) from 2001 to 2013. All sites experienced prolonged dry conditions during the study period. The impact of combined precipitation and temperature on Southwest ecosystems at both annual and sub‐annual timescales was tested using Standardized Precipitation Evapotranspiration Index ( SPEI ). All biomes studied had critical sub‐annual climate periods during which precipitation and temperature influenced production. In forests, annual peak greenness ( EVI max ) was best predicted by 9‐month SPEI calculated in July (i.e., January–July). In shrublands and grasslands, EVI max was best predicted by SPEI in July through September, with little effect of the previous year's EVI max . Daily gross ecosystem production ( GEP ) derived from flux tower data yielded further insights into the complex interplay between precipitation and temperature. In forests, GEP was driven by cool‐season precipitation and constrained by warm‐season maximum temperature. GEP in both shrublands and grasslands was driven by summer precipitation and constrained by high daily summer maximum temperatures. In grasslands, there was a negative relationship between temperature and GEP in July, but no relationship in August and September. Consideration of sub‐annual climate conditions and the inclusion of the effect of temperature on the water balance allowed us to generalize the functional responses of vegetation to predicted future climate conditions. We conclude that across biomes, drought conditions during critical sub‐annual climate periods could have a strong negative impact on vegetation production in the southwestern United States.