Response Mechanism Of Rodent Metacommunity In Desert Area To Disturbance And Climate Change

The water and heat conditions of the desert ecosystem are extremely unbalance.Once the ecosystem is damaged,it will degrade rapidly and even collapse.In recent years,due to the continuation of climate changing and increasing human disturbance,the desert ecosystem of Alxa has reached an extremely fragile state.Rodents are an important component of desert ecosystem and an important indicator of environmental changing.They are also a good research object on the impact of climate change on small animals.In order to explore the response mechanism of rodent communities on the local communities(rodent on one habitat patches)and meta-communities(collection of local communities in the study area)to continuous climate changing and human disturbances.Data collection was conducted on the field study area of the Desert Ecological Positioning Research Base of Inner Mongolia Agricultural University in the southern part of Alxa left Banner in 2014 to 2020.The study area was established in2001.At the study area,we established an experimental area using a randomized block design with 3 blocks and 4 treatments(Reclamation area,Grazing exclusion plots,Rotational area,Overgrazed area).The live traped method is used to investigate the rodent community in this area,and the climate(temperature,rainfall,thickness of snow),soil and plant data are simultaneously investigated.We analyzed the seasonal pattern and interannual fluctuation of the total number?diversity and?diversity of the rodent community.And then we use the structural equation modeling to analyze the effects of climate changing on the meta-communities and different local community.The influence mechanism of the local community on the meta-community were analyzed too.The specific results are as follows:(1)There is an obvious succession phenomenon in the rodent metacommunity.From 2014 to 2019,the main dominant species of the metacommunity is midday gerbil,and the secondary dominant species are northern three-toed jerboa and five-toed jerboa.In 2020,the number of northern three-toed jerboa is the highest,becoming the main dominant species of the community.(2)Among the four patch habitats,the gerbils are always the dominant specie in the reclaimed.the dominant species of rodent communities in the other habitats have obvious succession phenomena.The dominant species in the local rodent communities in the grazing exclusion and rotation grazing habitats are the three-toed jerboa or the midday gerbil,and the two rodents have substitution phenomenon between the years.In the local communities of overgrazing habitats,the dominant position of the five-toed jerboa and midday gerbils alternated irregularly between the years.(3)The?diversity local of rodent communities and metacommunities shows obvious convergence in seasonal patterns,and the overall influence of human disturbance is greater than the interannual effect.(4)On the habitat gradient,the Jaccard diversity index of the local community gradually decreases as the difference in the degree of interference increases.At the metacommunity scale,the phenomena of spatial species conversion(?_SIM)and species nesting(?_SNE)have always existed at the same time,and the highest in autumn;except for 2016,spatial species conversion has always been dominant in the rest of the year.(5)Rainfall has an indirect impact on the characteristics of local communities by affecting vegetation canopy closure and above-ground productivity of grassland;mean temperature directly affects the characteristics of local communities,and at the same time,it can affect rodent communities by affecting vegetation above-ground productivity indirectly.(6)Rainfall and temperature have significant direct effects on the total number of individuals,?diversity,and?diversity of the rodent metacommunity.At the same time,it can affect the total number of captured individuals and?diversity of the metacommunity through vegetation aboveground productivity indirectly.while temperature has a greater direct impact on the metacommunity,rainfall is more inclined to indirectly affection on the metacommunity through vegetation above-ground biomass.(7)The?diversity of the local community has a very significant negative effect on the?diversity of the metacommunity,while the total number of individuals has a very significant positive effect;the?diversity of local community in the grazing exclusion area has a significant negative effect on the?diversity of the metacommunity;both the?and?diversity of the local communities in the rotation grazing area have a very significant positive effect on the?diversity of the metacommunity;the characteristics of the local communities in the reclamation area all have a significant positive effect on the total number of the metacommunity;?Diversity and total number of individuals have a significant negative impact on the alpha diversity of the metacommunity.In conclusion,the influence mechanisms of climate changing on the rodent local communities and meta-communities are quite complex.As the mechanism of effection of hydrothermal conditions is different,the path of influence is also different.Among them,rainfall mainly affects the rodent community indirectly by affecting the characteristics of habitat vegetation,while temperature has a more direct effect on the rodent community,but also has an indirect effect.The meta-community is the coupling product of the habitat community through species migration and habitat filtration,resulting in a complex relationship between the local community and the regional process,which is reflected by the total number of individuals in the community,diversity and other indicators.