Effects Of Drought And Clipping Interaction On The Clonal Growth Of Agropyron Cristatum In Different Soil Substrates Under Warming Background

Global climate change and over-utilization have exacerbated grassland degradation,desertification and salinization.Soil drought has weakened the water retention capacity of land,inhibited plant growth,and reduced grassland productivity,which intensified the process of grassland degradation.The grasslands in Northwest Liaoning Province are located in the agricultural and pastoral staggered zone at the southern end of the Horqin Sandy Land in China and in the north,and the desertification of grasslands is becoming more and more serious due to the increase of temperature and the unreasonable use of human beings,which make the soil sandy and the vegetation sparse in the area.Agropyron cristatum is an advantageous population of sandy grasslands in Northwest Liaoning Province,which has excellent grass characteristics of drought resistance,barrenness and high nutritional value.In this study,Agropyron cristatum was used as the research object to analyze the effects of drought,soil nutrient substrates and human activity interference（clipping）on the growth of Agropyron cristatum cloning under the background of rising temperature,and provided experimental evidence and theoretical basis for the optimal management of sandy grassland and the regeneration of grassland vegetation and sustainable use.The results show that:（1）In sandy soil,temperature is the main factor limiting the growth of Agropyron cristatum,and the increase in temperature significantly reduces the accumulation of biomass above-ground biomass and below-ground biomass the Agropyron cristatum（normal temperature average above-ground biomass is 7.463 g/pot,average below-ground biomass is8.769 g/pot;increasing temperature average above-ground biomass is 1.712 g/pot,average below-ground biomass is 1.472 g/pot）.The temperature and water interaction determines the productivity of Agropyron cristatum population in sandy grasslands,and clipping can regulate the effect of water on the tillers and root biomass of Agropyron cristatum.（2）In different soil substrates,increasing temperature is beneficial to the accumulation of above-ground biomass of Agropyron cristatum（normal temperature average above-ground biomass is 8.805 g/pot;increasing temperature average above-ground biomass is 9.508 g/pot）.At normal temperature,clipping reduces the growth of the above-ground portion（biomass）of the plant（no clipping:9.508 g/pot,Moderate clipping:8.398 g/pot,high clipping:4.958g/pot）.High clipping can significantly inhibit the growth of Agropyron cristatum,but moderate clipping promotes the accumulation below-ground biomass of Agropyron cristatum（no clipping:10.731 g/pot,moderate clipping:11.883 g/pot）.Low-nutrition substituty soil inhibits Agropyron cristatum photosynthesis(low nutrition:1.158μmolm^-2s^-1,moderate nutrition:2.437μmolm^-2s^-1,high nutrition:4.199μmolm^-2s^-1),but the inhibition of low-nutrition substate on Agropyron cristatum photochresist is reduced after increasing and clipping treatment is applied(normal temperature low nutrition:1.158μmolm^-2s^-1,increasing temperature low nutrition:3.049μmolm^-2s^-1).（3）In different soil substrates,increasing temperature had no significant effect on the accumulation of total biomass of Agropyron cristatum population,but it changed the distribution mode of above-ground and below-ground biomass.