PS 42-19
Grazing effects on energy fluxes in a desert steppe on the Mongolian Plateau

Wednesday, August 12, 2015
Exhibit Hall, Baltimore Convention Center
Changliang Shao, Center for Global Change and Earth Observations (CGCEO), Michigan State University, East Lansing, MI
Jiquan Chen, Center for Global Change and Earth Observations (CGCEO), Michigan State University, East Lansing, MI
Linghao Li, State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences
Gang Dong, School of Life Science, Shanxi University
Juanjuan Han, State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences
Michael Abraha, Center for Global Change and Earth Observations (CGCEO), Michigan State University, East Lansing, MI
Ranjeet John, Center for Global Change and Earth Observations (CGCEO), Michigan State University, East Lansing, MI
Background/Question/Methods

This study investigated the effects of grazing on the energy balance (EB) components: net radiation (Rn), sensible heat (H), latent heat (LE), and soil heat (G) flux in the vulnerable desert steppe of the Mongolian Plateau. Paired eddy-covariance towers were used to directly measure these energy fluxes on adjacent grazed and ungrazed areas from 2010 to 2012.

Results/Conclusions

Near 90% of Rn was partitioned as H and LE, whereas the contributions of G and other components of the EB were 10% at annual scale. H dominated the energy partitioning and shared ~50% of Rn in this dry area. Grazing reduced H consistently both in dry and wet years, with 8% less than that in ungrazed area over the two growing seasons. Grazing reduced the growing season latent heat flux by 11% in the dry year of 2011, but increased it by 13% in the wet year of 2010. Grazing reduced Rn by 5%-10% but increased G by 13% more in ungrazed area, resulting in the available energy (Rn-G) to be was marked lower in grazed area than that in ungrazed area by 10%. There was remarkably 20% higher G/Rn during the day but 60% lower at night in grazed area than that in ungrazed area in a daily scale, but less obvious in yearly scale. There were positive relationships between LE/Rn and canopy conductivity, leaf area index, and soil moisture, between H/Rn and vapor pressure deficit, while negative relationship between H/Rn and soil moisture. Multiple linear stepwise regression analysis showed that H/Rn was controlled by soil moisture in the wet year whereas it was controlled by water vapor pressure deficit in the dry year. Both LE/Rn and H/Rn were changed dramatically in grazed area more than in ungrazed area as the soil moisture changes, indicating that the ungrazed area has a greater resistance to the changing climate.