ARS | Publication request: Simulating energy, water and carbon fluxes at the shortgrass steppe long term ecological site

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 5, 2006
Publication Date: September 20, 2006
Citation: Beltran-Przekurat, A., Pielke, Sr., R.A., Morgan, J.A., Burke, I.C. 2006. Simulating energy, water and carbon fluxes at the shortgrass steppe long term ecological site. Meeting Abstract. CDROM.

Technical Abstract: Coupled atmospheric-biospheric models are a particularly valuable tool for studying the potential effects of land-use and land-cover changes on the near-surface atmosphere. GEMRAMS is a coupled atmospheric-biospheric model composed of an atmospheric model, RAMS, and an ecophysiological process-based model, GEMTM. Our objectives were first, to evaluate the effect of cropping on a native shortgrass steppe ecosystem, and second, to assess the influence of landscape heterogeneity on simulated energy fluxes. We used the soil-vegetation-atmosphere-transfer scheme, LEAF2, from RAMS, coupled with GEMTM, to simulate energy, water and carbon dioxide fluxes over different cropping systems (winter wheat and irrigated corn) and over a mixed C3/C4 shortgrass prairie located at the USDA-ARS Central Plains Experimental Range near Nunn, Colorado, the Shortgrass Steppe (SGS) Long Term Ecological Research site. We compared simulated energy and CO2 fluxes to observations collected using Bowen ratio flux towers during two growing seasons. Both simulations and field observations indicated that irrigated corn systems substantially altered carbon dioxide and energy fluxes from the native shortgrass state. Seasonality also varied strongly among landuse types, with fluxes reflecting different plant developmental stages; the simulations agreed well with the observed patterns. In the second part of this study, we simulated energy fluxes for two clear days in early-summer and fall with GEMRAMS over a model domain centered at the SGS site. We evaluated the sensitivity to initial soil moisture conditions and spatial heterogeneity of vegetation distribution. Changes in landscape heterogeneity in the shortgrass steppe due to cropping incursions increased the spatial heterogeneity of the simulated energy fluxes compared to the native prairie.