ARS | Publication request: Seasonal and interannual variability in surface energy partitioning and vegetation cover with grazing at shortgrass steppe

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 28, 2010
Publication Date: December 22, 2010
Citation: Jamiyansharav, K., Ojima, D., Pielke, R.A., Parton, W., Morgan, J.A., Beltran-Przekurat, A., Lecain, D.R., Smith, D.P. 2010. Seasonal and interannual variability in surface energy partitioning and vegetation cover with grazing at shortgrass steppe. Journal of Arid Environments. 75:360-370.

Interpretive Summary: Understanding how grazing management and climate affect the hydrologic cycle of terrestrial ecosystems is key to understanding how climate change may interact with management to affect their long-term sustainability. In this research we used micrometeorological instrumentation to monitor evapotranspiration of a shortgrass prairie in eastern Colorado. Although we suspected that grazing by domestic livestock would have important impacts on hydrology, we found that this was true only under moist conditions. Year-to-year differences in precipitation had a much greater impact on standing above-ground biomass than did grazing intensity. The results suggest that grazing practices in such semi-arid grasslands have only modest effects on biophysical properties controlling their hydrology.

Technical Abstract: We evaluated shortgrass steppe energy budgets based on the Bowen Ratio Energy Balance method for three different grazing intensity treatments at the Central Plains Experimental Range Long-Term Ecological Research (CPER-LTER) site. We tested the correlations between aboveground biomass and surface energy fluxes for three different precipitation years based on continuously measured 20 min interval data. Grazing has a potential impact on energy partitioning under conditions of higher water availability, but not during dry conditions. Our study confirms that precipitation, not grazing treatment, explains the majority of variation in aboveground biomass at the CPER-LTER site. In addition, we are suggesting effective temperature, not air temperature, as a superior metric to evaluate surface heat change. Effective temperature takes into account humidity as well as air temperature.