Soil moisture patterns and fluxes responding to grazing intensity in semiarid inner mongolia grassland

authored by

Ying Zhao, Stephan Peth, Rainer Horn

Abstract

Overgrazing has been regarded as a main cause for land degradation in Inner Mongolia grassland because of the increase in population and shift in the socio-economic system in recent years. However, given the vital importance for the production of livestock and the environmental changes, fundamental understanding on topsoil sensitivity to grazing is lacking. Based on MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate) project, intensive observations, analyses, and modeling of environmental changes responding to grazing in Inner Mongolia grassland were conducted. In this chapter, we concentrated on the spatio-temporal variation of soil properties (e.g., soil moisture) in general and modeling the effects of grazing manage-ment (i.e., five grazing plots including, ungrazed since 1979=UG79, ungrazed since 1999=UG99, moderately grazed=MG, continuously grazed=CG, and heavily grazed= HG) on water flux in particular. Results showed that grazing treatment reduced the topsoil moisture contents (0-6 cm) and homogenized soil moisture spatial patterns which were controlled by soil and plant properties, especially soil physical properties. Multivariate geostatistics further revealed scale-dependent correlation for these controlling parameters depending on treatment. The soil and plant properties strongly controlled the variation of soil moisture for UG99 at short-scale (45 m), and for CG and HG at long-scale (90 m), however, weakly controlled the variation of soil moisture for UG79 and MG. Therefore, we suggest that pasture management strongly modified soil moisture patterns, which should be considered in the hydrological models at multiple spatial scales. Based on soil pit scaled monitoring data, we further found seasonal change of the soil moisture was most significant in the topsoil (0-10 cm) and was less pronounced in the deeper soil. Soil water storage decreased with increasing grazing intensity, which is linked to the grazing-induced soil structure change. Moreover, we use HYDRUS-1D model to parameterize this grazing-induced shifts of soil pore function. The model was well verified with the measured soil moisture values. The modeling results showed no significant difference on water budget components between the two ungrazed sites and moderate grazing, while heavy grazing significantly decreased interception from 17 to 7 mm and transpiration from 121 to 74 mm, and increased evaporation from 88 to 128 mm. We conclude that intensive grazing in our studied area deteriorated soil functions and reduced plant available water, and consequently reduced grassland productivity and enhanced the risks for wind and water erosion.

External Organisation(s)

Northwest Agriculture and Forestry University
Kiel University

Type

Contribution to book/anthology

Pages

97-130

No. of pages

34

Publication date

08.2012

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Agricultural and Biological Sciences(all)

Sustainable Development Goals

SDG 15 - Life on Land