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Inner Mongolia Agricultural University (2019)

Response of Soil Moisture to Rainfall in Arid and Semi-arid Grassland and Relationship between Plant Community and Meteorological Factors

徐冉;

Titre : Response of Soil Moisture to Rainfall in Arid and Semi-arid Grassland and Relationship between Plant Community and Meteorological Factors

Auteur : 徐冉;

Grade : Master’s Theses 2019

Université : Inner Mongolia Agricultural University

Résumé
The stability of grassland ecosystem has been threatened by human factors and climate change.Grassland desertification has become more and more serious.The characteristics of grassland hydrological changes and plant community response under human influence have become the key and research hotspots for maintaining grassland ecological stability.Arid and semi-arid grassland is the main component of grassland ecosystem in China.Soil water is the link between atmospheric water,surface water and groundwater,and it also significantly affects the growth and development of grassland vegetation.This paper takes the typical arid and semi-arid grassland in Inner Mongolia as the research object,combined with continuous monitoring,periodic sampling and laboratory experiments,based on meteorological data,soil moisture data,vegetation data and soil characteristics data to describe the impact of grazing on grassland soil moisture and soil water content response to rainfall ;using correlation analysis,aggregation classification,analysis of variance and other methods to explore the distribution of plant communities(composition,comprehensive status)and its relationship with meteorological factors ;analysis of rainfall,relative humidity,temperature,solar radiation the direct or indirect effects of aboveground biomass,underground biomass,root-shoot ratio change ;in order to summarize the conversion law of rainfall and soil moisture and the characteristics of meteorological conditions on grassland vegetation community change,to understand the local grassland hydrological process,predict or improve grassland productivity provides basic data and theoretical basis for developing reasonable grazing policies,protecting grassland species diversity,and combating grassland desertification.The main findings are as follows :(1)Grazing will lead to a decrease in biomass on the grassland,an increase in soil evaporation,and a decrease in rainfall conversion rate ;grazing will affect the roots of 0~15 cm vegetation,resulting in weaker water absorption capacity of the roots,and faster migration of upper soil moisture,so the water content of the 0~15cm layer is smaller than the forbidden pastoral area,but the 30cm layer is larger than the forbidden pastoral area ;the soil moisture of the 5cm,10cm and 15cm layers response to the rainfall is similar in the forbidden pastoral area and the grazing area.When the single or cumulative rainfall greater than 10mm,there is a significant increase on soil water content,but it will change due to the interval of drought interval(the number of days without rain between two rainfall events).The water content in the forbidden pastoral area is more sensitive to rainfall,and the increase is larger ;there is obvious hysteresis in the response of soil moisture to rainfall at 30cm layer.When the single rainfall in the grazing area is greater than 30mm or the cumulative rainfall is greater than 20mm and the drought interval is<3d,the soil moisture increases significantly.The 30cm layer in the grazing area is only continuous in the short interval(≤2d)big rainfall(>35mm),there is obvious fluctuation ;the increase of soil moisture in the 0~30cm layer of the grazing area is extremely significant with rainfall and rainfall intensity.Grazing 0~15cm layer associated with significant rainfall,0~10cm layer and the rainfall intensity significantly correlated.(2)After 5 years of grazing prohibition,the soil vertical heterogeneity is enhanced.During the rainfall process,the soil moisture content of each soil layer is significantly different,while the grazing area is opposite.The lag time of soil moisture response to rainfall in the two regions increases with the depth of the soil layer.Compared with the grazing-free area,the shallow soil(5cm,10cm)in the grazing area has weaker water holding capacity and shorter infiltration time ;the rainfall below 5mm has no obvious replenishment effect on the soil moisture in the grazing grazing and grazing areas ;And the strength is not more than 5 mm/h is most favorable for infiltration,the infiltration depth of the grazing area reaches 15cm and 30cm layer respectively requires 7.9mm and more than 25mm of rainfall,while the grazing area greater than 5mm of rainfall can infiltrate into the 30cm soil layer ;The independent rainfall with intensity of 5~6mm/h can only infiltrate into the topsoil(5cm).The rainfall with intensity greater than 15mm/h can penetrate into the 30cm and deeper soil through the macropores in the forbidden pastoral area,and the surface layer in the grazing area.

Mots clés : Arid and semi-arid grassland; Soil water content; Rainfall pattern; Community structure; Biomass; Meteorological factor;

Présentation (CNKI)

Page publiée le 20 mars 2020