Effects Of Grassland Management And Precipitation Changes On Aboveground Net Primary Productivity Of Typical Steppe In Inner Mongolia

The aboveground net primary productivity of grassland is an important performance of grassland ecosystem function and it determines the basic functions of the grassland ecosystem.It is the basic link that controls nutrient cycle,energy flow and carbon cycle process.Productivity is also the energy and material basis for human and animal use in ecosystem.However,in the current situation of rapidly global climate change and increasingly serious grassland degradation,we should pay more attention to the changes of aboveground net primary productivity.The typical grassland in Inner Mongolia is located in arid and semi-arid areas,and precipitation is the main limiting factor of aboveground net primary productivity on grassland.Grazing,fencing and clipping are common ways of grassland utilization in Inner Mongolia.The experiment was carried out in a typical grassland in Xilinhot,Inner Mongolia.Relying on the grassland management platform established in 2012,a precipitation change control platform was established in different grassland management plots in 2016.This experiment was designed with the split-plot.And the three grassland management methods of grazing,fencing,and clipping are set as the plot treatment.The three precipitation gradients of precipitation-50%,precipitation unchanged and precipitation+50%are set as the sub-plot treatment.In 2017-2018,we studied the effects of grassland management and precipitation changes on aboveground net primary productivity of typical steppe in Inner Mongolia,and analyzed the changes of aboveground net primary productivity from the perspectives of different plant functional groups and dominant species,common species and rare species.The main results are as followed:1.Precipitation changes had significant effects on aboveground net primary productivity.At the two-year average,the treatment of 50%reduction in precipitation resulted in a 72.87%reduction in aboveground net primary productivity of the plant community.With 50%increase in precipitation,plant community had the highest aboveground net primary productivity,reaching 114.52g m^-2,which is an increase of 36.56%compared the plots with unchanged precipitation.However,compared to precipitation,grassland management has less impact on aboveground net primary productivity.Only under the condition of unchanged precipitation in 2017,grazing treatment has higher aboveground net primary productivity than mowing treatment.There is no significant interaction between grassland management and precipitation changes.2.The change of precipitation has a significant impact on the aboveground net primary productivity of perennial grass group.The aboveground net primary productivity of perennial grasses increased by 43.26%when precipitation increased by 50%.Compared to precipitation,grassland management has a less impact on perennial grasses.Grassland management and precipitation changes have no significant impact on perennial forbs and annual species.Annual species are sensitive to interannual changes of precipitation.3.Precipitation changes had significant effects on aboveground net primary productivity of dominant species.When the precipitation increased by 50%,the aboveground net primary productivity of the dominant species increased significantly by 30.47%.At the two-year average,grassland management had no significant effect on aboveground net primary productivity of dominant species.The grassland management and precipitation changes have less effect on common species and rare species.4.The main reason for the increase on aboveground net primary productivity of the community is that precipitation significantly promotes the growth of perennial grasses and dominant species.There is no obvious compensatory effect between different functional groups and between dominant species,common species,and rare species.