| Grasslands have been degraded to varying degrees under the influence of climate change and human activities,exposing grasslands and their surrounding areas to a high risk of desertification.In this study,we conducted experiments based on rainfall and grazing conditions on typical grasslands in Inner Mongolia,and explored the characteristics of surface radiation balance changes under different rainfall and grazing conditions using meteorological data,radiation data,and soil data.In addition,we estimate the above-ground biomass and determine the grazing intensity based on remote sensing technology to provide a management basis for investigating the energy balance characteristics of grassland under the influence of both climate change and human activities in the future.The following conclusions were ultimately obtained from the above research findings:1.The characteristics of changes in radiation budget at the site revealed that after the grazing prohibition,the grassland was not grazed and trampled by livestock,the vegetation improved,and the short-wave radiation,long-wave radiation and albedo decreased by 4.9%,3.6% and 5.0%,respectively,while the net radiation increased by 20.3%.Increased rainfall areas in grazing and grazing grasslands with an overall decrease in short-wave radiation,long-wave radiation and albedo,and an increase in net radiation,with the opposite reduction in rainfall.At the same time,vegetation growth was vigorous from July to August,and the daily surface short-wave radiation and albedo of the grazing prohibited grassland decreased the most,reaching 10.41% and 10.42%.The net radiation increased after rainfall increase and decreased after rainfall reduction in the grazing prohibited grassland,and the net radiation was also promoted by grazing rainfall increase,while the net radiation was weakly inhibited by rainfall reduction.2.Soil characteristics of grasslands under different grazing pressure and rainfall conditions varied widely,with grazing prohibition leading to a decrease in soil temperature,with the largest difference of 0.64°C.Compared to the grazing area with increased or decreased rainfall,the soil temperature decreased more significantly after increased rainfall in the grazing prohibition area,especially during the rainy season from June to August,1.57°C,1.44°C,and 1.27°C,respectively,while decreased rainfall increased the temperature,with larger increases in June and September,0.69°C and 0.73°C,respectively.Meanwhile,the soil water content of grassland increased after grazing prohibition,and the difference was obvious in spring and autumn.Moreover,the increased rainfall in the grazing prohibited grassland all led to an increase in soil water content,while the overall decrease in soil water content in the rainfall reduction area.Grassland surface albedo was negatively correlated with soil temperature,water content,air temperature and saturated water vapor pressure difference,while it was positively correlated with net radiation.The analysis shows that soil temperature has the highest relative importance for surface albedo and soil water content has the highest relative importance for net radiation.3.The accuracy was found to be good by comparing the measured data with the estimated surface parameters.Meanwhile,the regression model of AGB and NDVI was constructed,and the AGB frequency histogram and density distribution were used to quantify the AGB threshold of grazing intensity under different grazing intensities.The results showed that the above-ground biomass of Eritu grazing land showed a spatial distribution trend of low in the east and high in the west,and most of it was in moderate grazing intensities.In addition,the positive correlation between vegetation index and net radiation was high,while it was negatively correlated with albedo.Moreover,there is also a significant negative correlation between grazing intensity and vegetation index,and overgrazing will lead to vegetation reduction,land degradation,and suppression of surface energy uptake.4.The NDVI,LAI,net radiation and above-ground biomass of Xilingol league showed a spatial distribution trend of high in the east and low in the west,while the albedo was opposite to them.In the past 5 years,NDVI,LAI,net radiation and aboveground biomass showed an increasing trend,but the annual variation was small,mainly concentrated in Abaga Banner and Duolun County,etc.Most of the grasslands in the league are moderately grazed,and the grazing intensity has increased in recent years.Also,the albedo response to vegetation factor changes is large,while the net radiation response is small. |
