We have a new paper that has appeared. It is
Jamiyansharav, K., D. Ojima, R.A. Pielke Sr., W. Parton, J. Morgan, A. Beltrán-Przekurat, D. LeCain, and D. Smith, 2011: Seasonal and interannual variability in surface energy partitioning and vegetation cover with grazing at shortgrass steppe. J. Arid Environments, 75, 360-370, doi:10.1016/j.jaridenv.2010.11.008.
The abstract reads
“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 above ground 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 above ground 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.”
The conclusion reads
“We clearly observed a pattern of higher latent heat flux with higher biomass during wet periods. This suggests a potential
impact of grazing on energy budgets if grazing treatments had led to a measurable difference on green biomass. We recommend further testing of the assumption that grazing treatments should have an impact on the surface energy budget when green biomass is significantly impacted. Similar studies could be performed in long-term heavily grazed sites to better assess differences on the measured variables.
Measurements of albedo are necessary to investigate the amount of absorbed incoming radiation for different grazing treatments. In addition, it would be useful to have separate estimates of water loss via evaporation and transpiration to be able to distinguish water loss from the soil surface versus the vegetation. Metrics of leaf area index, vegetation greenness, and albedo using remote sensing technology would help in the study of surface energy budgets because of more continuous data availability.
Our results can help to further thorough investigation of compound effects of grazing and precipitation to better understand the semi-arid zones’ land-atmosphere interactions under current climate change conditions. Grasslands, including semi-arid and arid SGS exist in every continent, covering almost half of the earth’s terrestrial surface (Suttie et al., 2005). The sensitivity of global change is expected to be high at these arid lands. Therefore our study will also help to gain understanding through modeling how grazing management and precipitation would impact the energy budget partitioning on these semi-arid and arid lands in the context of global climate change.”