The Effect Of Simulated Precipitation On The Plant Diversity Of Different Stocking Rates In Desert Steppe

In order to research the effects of precipitation and grazing on plant community characteristics and diversity,the field control experiment was conducted in the Stipa breviflora desert steppe in Siziwang banner,Inner Mongolia.The experiment was combined different precipitation gradients and different stocking rates,the experiment of different stocking rates was carried out by randomized complete block design.There were 3 replicates,and each replicate had 4 different stocking rates.The stocking rate was 0,0.91,1.82,and 2.71 SE·hm-2·half year-1,respectively,and each block were randomly designed.While the simulated precipitation experiment was attached to the grazing platform at each stocking rate.There are four precipitation gradients in each stocking rate plot,which were 50%reduced precipitation(PI),natural precipitation(P2),50%increased precipitation(P3),and 100%increased precipitation(P4).The height,coverage,density,biomass of the plant community and the soil water content were measured during the experiment period.The results shown that:1.During two experimental years,the soil water content was higher in 2016 than it in 2017.The soil water content in LG and MG treatments was significantly higher than that in HG and CK treatments.The soil water content ranked from large to small under four precipitation treatments was:P4 treatment>P3 treatment>P2 treatment>P1 treatment(P<0.05),the stocking rate and precipitation have significant effects on soil water content,and the interaction between stocking rate and precipitation had no significant effect on soil water content.2.The height,coverage,density and biomass of plant communities in 2016 were higher than that in 2017.The results showed that the stocking rates,precipitation,and years have significant effects on coverage,density,and biomass,and there are no significant interaction effects of stocking rates,precipitation,and years on all of community's factors above mentioned.In the year of abundant precipitation(2016),the height,density and biomass of plant communities in P3 treatment of CK were higher than that of P3 and P4 in MG and HG,while the water content in 2017 was relatively lower.The height,coverage,density and biomass of P4 in LG were higher than that of P4 in MG and HG.This indicated that light stocking rate was beneficial to plant community growth in both dry and humid years relatively,while high stocking rate had a negative effect on plant communities.In the humid year,excessive water addition has an adverse effect to the plant growth with the precipitation increased,while the plan community grew vigorously with the precipitation increasing in drought year.3.Under the same stocking rate,the treatment of reduced precipitation decreased the Shannon Weiner index,the richness and the evenness index.There was no difference between P3 and P4 treatment of the Shannon Wiener index,richness and evenness index;excessive or insufficient of precipitation both have negative effect on the species diversity of desert steppe ecosystem,Under the same precipitation treatment,moderate grazing was beneficial to increasing plant diversity.