Effects of Grazing Intensity on Soil Water Regime and Flux in Inner Mongolia Grassland,China  

作　　者：GAN Lei PENG Xin-Hua S.PETH R.HORN 

机构地区：[1]State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences,Nanjing,210008(China) [2]Institute of Plant Nutrition and Soil Science,Christian-Albrechts-University zu Kiel,Olshausenstrasse 40,24118 Kiel(Germany)

出　　处：《Pedosphere》2012年第2期165-177,共13页土壤圈（英文版）

基　　金：Supported by the German Research Foundation(DFG)(No.Forschergruppe 536);the Hundred Talents Program of the Chinese Academy of Sciences

摘　　要：In the past few decades, the increase in grazing intensity has led to soil degradation and desertification in Inner Mongolia grassland, China, due to population growth and shift in the socio-economic system. Two sites with different grazing intensities, continuous grazing site （CG） with 1.2 sheep ha-1 year-1 and heavy grazing site （HG） with 2.0 sheep ha-1 year-1, were investigated at the Inner Mongolia Grassland Ecosystem Research Station （43° 37′ 50″ N, 116° 42′ 18″ E） situated in the northern China to i） characterize the temporal distribution of soil water content along soil profile; and ii） quantify the water fluxes as affected by grazing intensity. Soil water content was monitored by time domain refiectometry （TDR） probes. Soil water retention curves were determined by pressure membrane extractor, furthermore processed by RETC （RETention Curve） software. Soil matric potential, plant available water and water flux were calculated using these data. Both sites showed an identical seasonal soil water dynamics within four defined hydraulic periods： i） wetting transition coincided with a dramatic water increase due to snow and frozen soil thawing from March to April; 2） wet summer, rainfall in accordance with plant growth from May to September; 3） drying transition, a decrease of soil water from October to November due to rainfall limit; and 4） dry winter, freezing from December to next February. Heavy grazing largely reduced soil water content by 43%-48% and plant available water by 46%-61% as compared to the CG site. During growing season net water flux was nearly similar between HG （242 mm） and CG （223 mm） sites between 5 and 20 cm depths. However, between 20 and 40 cm depths, the upward flux was more pronounced at HG site than at CG site, indicating that water was depleted by root uptake at HG site but stored at CG site. In semi-arid grassland ecosystem, grazing intensity can affect soil water regime and flux, particularly in the growing season.In the past few decades,the increase in grazing intensity has led to soil degradation and desertification in Inner Mongolia grassland,China,due to population growth and shift in the socio-economic system.Two sites with different grazing intensities,continuous grazing site(CG) with 1.2 sheep ha 1 year 1 and heavy grazing site(HG) with 2.0 sheep ha 1 year 1,were investigated at the Inner Mongolia Grassland Ecosystem Research Station(43 37 50 N,116 42 18 E) situated in the northern China to i) characterize the temporal distribution of soil water content along soil profile;and ii) quantify the water fluxes as affected by grazing intensity.Soil water content was monitored by time domain reflectometry(TDR) probes.Soil water retention curves were determined by pressure membrane extractor,furthermore processed by RETC(RETention Curve) software.Soil matric potential,plant available water and water flux were calculated using these data.Both sites showed an identical seasonal soil water dynamics within four defined hydraulic periods:1) wetting transition coincided with a dramatic water increase due to snow and frozen soil thawing from March to April;2) wet summer,rainfall in accordance with plant growth from May to September;3) drying transition,a decrease of soil water from October to November due to rainfall limit;and 4) dry winter,freezing from December to next February.Heavy grazing largely reduced soil water content by 43%-48% and plant available water by 46%-61% as compared to the CG site.During growing season net water flux was nearly similar between HG(242 mm) and CG(223 mm) sites between 5 and 20 cm depths.However,between 20 and 40 cm depths,the upward flux was more pronounced at HG site than at CG site,indicating that water was depleted by root uptake at HG site but stored at CG site.In semi-arid grassland ecosystem,grazing intensity can affect soil water regime and flux,particularly in the growing season.

关 键 词：heavy grazing plant available water semi-arid grassland soil matric potential soil water content 

分 类 号：S812[农业科学—草业科学] S812.8[农业科学—畜牧学]