| Under the influence of climate change and human activities,typical grasslands have undergone different degrees of degradation,seriously affecting the stability of grassland ecosystems and exposing typical grassland meadows and their surrounding areas to a high risk of desertification or land degradation.To address the desertification and land degradation of grasslands and the impact of precipitation on ecosystem structure,pattern and function,the In this thesis,a two-factor experiment on altered rainfall and grazing ban was conducted through a representative area of a typical grassland in Xilinguole League Zhengxiangbai Banner,Inner Mongolia,where vegetation and soil in the experimental area were observed for four consecutive years from 2018 to 2021 to quantify the effects of six different treatments(grazing ban rainfall increasing JP+,grazing ban rainfall decreasing JP-,grazing ban control JCK,grazing rainfall increasing FP+,grazing rainfall decreasing FPand grazing FCK)on soil and vegetation dynamics.The main findings of the study are as follows: The changes in the structure,pattern and function of a typical grassland ecosystem in Inner Mongolia were explored in terms of rainfall and grazing exclusion,with the aim of providing a basis for grassland use,soil and water conservation,and grassland restoration in the region.1.comparing the soil data before and after 4 years of experimental treatments,it was found that at the beginning of the experiment,the physical and chemical indicators of the soil in the no-grazing area were extremely similar to those in the grazing area,and 4 years after the experiment was conducted,the soil bulk density of the 0-15 cm soil layer decreased significantly and the total porosity increased.Soil moisture,organic matter,and soil temperature in the no-grazing zone were higher than in the no-grazing control zone.Soil moisture,organic carbon and total nitrogen all tended to decrease with increasing grazing time,and the smaller the rainfall,the greater the change.The different precipitation treatments resulted in significant differences in soil moisture,with each layer showing strong fluctuations in soil moisture during the rainy season.The grazing ban was helpful for the recovery of soil moisture in the surface layer,where the volumetric soil moisture content was higher than under the equivalent treatment in the grazing area,while the trampling of livestock under the grazing area treatment destroyed the surface structure of the soil,making the soil composition disproportionate and less stable,and more susceptible to soil erosion.In contrast,increased rainfall has an elevating effect on soil water in the deeper layers(60-100 cm),while the water content in the deeper layers is lower under the reduced rainfall treatment.2.Four typical rainfall events(light rainfall with a total of 4.3 mm and a total of 3.1mm;moderate rainfall with a total of 13.1 mm;and heavy rainfall of 33.9 mm)were screened at 10 min intervals to analyse and explore the response of soil water to rainfall.The results showed that small rainfall events with high rainfall and long duration had a positive effect on soil moisture and favoured soil moisture recovery both during the growing season and throughout the year.The increase in deep soil moisture was greater during heavy precipitation events,favouring deep soil moisture recovery.The rate of change in soil moisture recharge(ΔSM)increased with the amount and intensity of precipitation,with 4.3mm rainfall events having a greater effect on soil moisture than 3.1 mm rainfall events.Plant apoplast can reduce ΔSM by trapping precipitation,and ΔSM was higher in the no-grazing reduced rainfall JP-grassland community under all rainfall events than in the other treatments;among the different treatment types,the lowest vegetation cover grassland had the smallest rainfall threshold to affect soil moisture,and its recharge was the largest and most reduced.3.The vegetation characteristics of grasslands under different grazing pressure and rainfall conditions differed significantly,with grazing exclusion leading to a significant increase in total biomass,including above-and below-ground biomass,with 54.5%,78.5%and 61.5% increases in total biomass in grazing exclusion control,rainfall increase and rainfall decrease areas compared to grazing areas,and vegetation cover,height,density,root to crown ratio and abundance of graminoids The vertical distribution showed that belowground biomass decreased more sharply with grazing time in 0-5 cm depth soils than in 15-30 cm soils,and was significantly positively correlated(P<0.05)with 0-5 cm soil moisture content,compactness,organic carbon,total N and fast-acting N.Under JCK and JP+ treatments,belowground biomass was significantly lower than in 15-30 cm soils.Species diversity was significantly correlated with total soil nitrogen(P<0.05),while only under the FP+ treatment in the grazed area was species diversity significantly correlated with total soil nitrogen(P<0.01).In addition,soil p H was strongly influenced by soil moisture,and as soil moisture increased,p H decreased,affecting plant growth and function to some extent.The biased redundancy analysis showed that soil moisture significantly influenced vegetation diversity variation,explaining 4.2% to 47% of the variation in vegetation diversity,and that soil carbon,nitrogen and capacitance significantly influenced vegetation diversity variation(p<0.01),contributing 3.3% to 33.1%,3.2% to 29.6% and 3.7% to 20.7%of the variation in vegetation diversity.Therefore,appropriate and effective grazing is an available method to counteract local grassland degradation and promote sustainable rangeland development. |
PDF Full Text Request