title: Grazing effects on surface energy fluxes in a desert steppe on the Mongolian Plateau.
abstract: Quantifying the surface energy fluxes of grazed and ungrazed steppes is essential to understand the roles of grasslands in local and global climate and in land use change. We used paired eddy-covariance towers to investigate the effects of grazing on energy balance (EB) components: net radiation (Rn), latent heat (LE), sensible heat (H), and soil heat (G) fluxes on adjacent grazed and ungrazed areas in a desert steppe of the Mongolian Plateau for a two-year period (2010-2012). Near 95% of Rnwas partitioned as LE and H, whereas the contributions of G and other components of the EB were 5% at an annual scale. H dominated the energy partitioning and shared ~50% of Rn. When comparing the grazed and the ungrazed desert steppe, there was remarkably lower Rnand a lower H, but higher G at the grazed site than at the ungrazed site. Both reduced available energy (Rn- G) and H indicated a "cooling effect" feedback onto the local climate through grazing. Grazing reduced the dry year LE but enhanced the wet year LE. Energy partitioning of LE/Rnwas positively correlated with the canopy conductivity, leaf area index, and soil moisture. H/Rnwas positively correlated with the vapor pressure deficit but negatively correlated with the soil moisture. Boosted regression tree results showed that LE/Rnwas dominated by soil moisture in both years and at both sites, while grazing shifted the H/Rndomination from temperature to soil moisture in the wet year. Grazing not only caused an LE shift between the dry and the wet year, but also triggered a decrease in the H/Rnbecause of changes in vegetation and soil properties, indicating that the ungrazed area had a greater resistance while the grazed area had a greater sensitivity of EB components to the changing climate.
authors.affiliation: Center for Global Change & Earth Observations, Michigan State University, East Lansing, Michigan, 48823, USA.
authors.forename: Changliang
authors.initials: C
authors.lastname: Shao
authors.affiliation: Center for Global Change & Earth Observations, Michigan State University, East Lansing, Michigan, 48823, USA.
authors.forename: Jiquan
authors.initials: J
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, Beijing, 100093, China.
authors.forename: Linghao
authors.initials: L
authors.lastname: Li
authors.affiliation: School of Life Science, Shanxi University, Taiyuan, 030006, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, Beijing, 100093, China.
authors.forename: Juanjuan
authors.initials: J
authors.lastname: Han
authors.affiliation: Center for Global Change & Earth Observations, Michigan State University, East Lansing, Michigan, 48823, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Abraha
authors.affiliation: Center for Global Change & Earth Observations, Michigan State University, East Lansing, Michigan, 48823, USA.
authors.forename: Ranjeet
authors.initials: R
authors.lastname: John
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002681:China; D003889:Desert Climate; D017753:Ecosystem; D005247:Feeding Behavior; D065948:Grassland; D011891:Rain; D012621:Seasons; D012756:Sheep / Q000502:physiology; D013997:Time Factors
keywords: available energy; cooling effect; ecosystem function; ecosystem stability; eddy-covariance; energy balance; energy partitioning; land use change; latent heat; net radiation; sensible heat; soil heat