Effects Of Different Management Patterns On Soil Water-carbon Relationships And Plant Communities In Grasslands

With the dry warming of the climate and unreasonable human grazing,various types of grasslands in Inner Mongolia are degraded to different degrees.As grassland water resources are relatively scarce,soil moisture has become a major limiting factor in vegetation survival and ecological recovery,while the impact of grassland vegetation communities on soil water and carbon has a trade-off relationship.Therefore,in this study,we carried out sentinel monitoring in three different types of grasslands and analysed the plant species composition,above-ground biomass,soil water content,total vegetation carbon and soil organic carbon at 18 grassland sites to study their response to grassland management patterns,with the aim of providing a basis for grassland use,soil and water conservation,and grassland restoration in Inner Mongolia:1.The variability of soil moisture and other soil properties in grassland under different management modes is significant.In the typical grassland of White Banner,for example,the difference between surface soil moisture in May between closed and grazed areas was 18.3%;in the middle layer of soil,since the rainfall on 22 June,soil moisture in closed areas was significantly higher than in grazed areas,with an average of 15.35%higher;in the deep layer of soil from May to August,soil moisture in grazed areas was significantly higher than in closed areas,with an average of 19.68% higher.Comparing the three types of grassland,it was found that typical grassland surface soil moisture was the most sensitive to rainfall response.The correlation analysis showed that soil moisture in the surface layer of typical grassland and desert grassland was significantly positively correlated with relative air humidity(P<0.01);soil temperature in meadow grassland was significantly positively correlated with soil moisture in July(P<0.01),while the other two types of grassland were negatively correlated.2.There were significant differences in the composition of grassland vegetation and its diversity under different management patterns.The average number of species recorded in the three grasslands under short-term grazing exclusion was 10.25,slightly greater than the average number of species recorded in the grazed area of 10.08,while the number of species recorded in the grazed area of the typical grassland site under long-term grazing exclusion was 16.7% greater than that of the grazed area.Grazing significantly increased the Shannon-Wiener diversity and species evenness of the meadow grassland plant community and reduced the dominance index;grazing reduced the species richness of the desert grassland,while the Shannon-Wiener diversity,species evenness and dominance index increased slightly relative to grazing.The mantel-test analysis showed that above-ground biomass and rainfall were significantly positively correlated in typical grasslands,but above-ground biomass was significantly positively and negatively correlated with relative air humidity in meadow and desert grasslands,respectively.3.The mean values of soil organic carbon in 0～10cm and 30～50cm in grazing areas were significantly higher than those in grazing areas,and the soil organic carbon in each soil layer in the typical grassland site with long-term grazing ban was significantly lower than that in the short-term grazing grassland site;the soil organic carbon content in0～10cm in meadow grassland was 62.87% and 28.37% higher than that in desert grassland and typical grassland respectively.The carbon stocks of above-ground vegetation and below-ground roots were much higher than those of grazing areas,60.02%and 45.52% higher respectively;while the carbon stocks of vegetation at sites with long-term grazing ban were significantly lower than those at sites with short-term grazing ban;the structural model showed that the negative direct effects of long-term grazing ban on soil moisture and total biomass on soil organic carbon stocks were greater than those at sites with short-term grazing ban.Based on the results of the study,it is clear that climatic factors,especially rainfall,are particularly important for vegetation communities and carbon stocks in desert grasslands,and that long-term grazing closures do not maintain plant diversity and are not conducive to carbon accumulation in grassland ecosystems.