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Title: Controls on gross production in an aspen-sagebrush vegetation mosaic

item Fellows, Aaron
item Flerchinger, Gerald
item Seyfried, Mark
item LOHSE, KATHLEEN - Idaho State University
item PATTON, NICHOLAS - Idaho State University

Submitted to: Ecohydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2018
Publication Date: 1/2/2019
Citation: Fellows, A.W., Flerchinger, G.N., Seyfried, M.S., Lohse, K.A., Patton, N.R. 2019. Controls on gross production in an aspen-sagebrush vegetation mosaic. Ecohydrology. 12(1):e2046.

Interpretive Summary: Problem: Changes in climate over the coming century are anticipated to impact plant production and vegetation health in the northern semiarid Great Basin. Precipitation forecasts are highly uncertain, and include possible increases and decreases in annual precipitation. Warming is expected to drive earlier snowmelt. The ecological impact of these changes are uncertain, and require a better understanding of the controls on plant production in the semiarid Great Basin. Accomplishment: We investigated the impact of snowmelt timing and precipitation on ecosystem-level carbon uptake in an aspen forest and a sagebrush shrubland located in the northern Great Basin. Impact: We found carbon uptake was insensitive to annual precipitation amount and snowmelt timing at the aspen and sagebrush for the conditions we observed. This work describes key ecological mechanisms that may make aspen-sagebrush vegetation mosaics robust to certain types of climatic change, but also indicates key vulnerabilities to vegetation health and production.

Technical Abstract: The Critical Zone (CZ) mediates the impact of precipitation amount and timing on water availability in arid and semiarid ecosystems. In the cold-semiarid northern Great Basin, soil and subsurface structure is poorly mapped and multi-year records of ecosystem-level Gross Ecosystem CO2 Exchange (GEE) are limited, leading to considerable uncertainty in the links between precipitation, water availability, and carbon exchange in this region. We therefore determined GEE and examined the sensitivity of GEE to precipitation in a sagebrush shrubland and an aspen forest located in the northern Great Basin. The aspen and sagebrush were within 500-m of each other and had a similar climatic mean annual precipitation and temperature, but marked differences in CZ structure. Cumulative growing season GEE was ~2 times greater at the aspen than at the sagebrush, underscoring the importance of CZ properties, independent of climate, in structuring spatial “hotspots” for carbon cycling in Western US rangelands. Temporal variability in cumulative growing season GEE within each site was not driven by annual precipitation. Weak temporal variability in cumulative growing season GEE with annual precipitation was attributed to the site’s limited ability to store water and an associated loss of precipitation to streamflow. Sagebrush GEE, however, varied with spring and summer rain and aspen GEE responded to spring snowpack conditions. These results emphasized how mapping and understanding CZ structure and function will help predict the spatial and temporal sensitivity of cumulative growing season GEE to precipitation in the Great Basin.