Spatial Pattern And Effects Of Stipa Community In Desert Steppe

The restoration of desert steppe vegetation plays an important role in maintaining the ecological barrier in northern China.The harsh natural environment and historically excessive human factors have caused serious degradation of grassland in desert grasslands.Closure and grazing prevention is the most important restoration measure.Over the years,the grassland vegetation coverage that has been degraded has been significantly restored.In the face of harsh natural conditions in the desert grassland area,the establishment of vegetation types that are compatible with the environment is still a problem of unresolved.The Stipa community,as the original vegetation type of the desert steppe,has formed a highly adaptive mechanism for the natural environment of the region during the long-term evolution process.In particular,the spatial distribution pattern of specific population density,size,etc.formed by its population driven by habitat water factors.Soil moisture is a key driver of various ecological processes in the desert grassland area.Therefore,the Stipa community is used as a reference system for the restoration of desert steppe vegetation.Based on the spatial distribution pattern of Stipa community in the habitat,it can break the structural information of natural ecosystems and provide scientific basis for the establishment of environmentally sustainable restoration of vegetation.In this study,the Stipa community in the desert steppe of Ningxia was studied.In 2017,three enclosed grasslands were selected,and a large 64 m2 plot was selected from the each grassland for vegetation investigation.11 pairs of 1 m2 quadrats were sampled for spicules and 0-10cm,10-20cm and 20-40cm soil samples for determination of soil moisture,pH and CaCO3 content.At the same time,one large,medium and small Stipa plexus was selected from each plot,and soil samples were collected from the center of Stipa outward and every 5 cm from the surface down,and measuring soil moisture,pH,organic carbon,total nitrogen,total phosphorus,available phosphorus and nitrogen content.The species-area relationship curves,plant diversity indices,diffusion coefficient methods were used to systematically analyze the diversity of Stipa community,individual spatial distribution patterns,and response mechanisms to the soil factors in the habitat.The main results and conclusions are as follows:(1)After the grazing and grazing prohibition,the coverage of the Stipa community in the desert steppe is 40%-70%.The dominant species in the community is the Stipa brevifLora?Botrytis communis and Cleistogenes squarrosa,.The species-area curve of the community conformed to the power function characteristics:S = 6.40A0 30(P ?0.01),R2 = 0.99,the species-area curve Z = 0.30,belonging to islands or isolated plaques.(2)In the desert steppe area,Stipa breviflora,Botrytis communis,and Cleistogenes squarrosa were distributed or clustered in clusters on the scale of 0.25m2 and lm2,and clustered on the 4m2.9m2and 16m2 scales,forming a fragmented landscape.The cluster strength gradually increases with the increase of the scale,reaching the maximum at the 4m2 scale and becoming flat at the 9m2 scale.Cluster strength increases with scale,which is the result of the plant's own characteristics and the lack of resources.(3)From the individual micro-scales of the plants within the community,compared with soil micro-habitats,the 0-10cm soil of Stipa californca individual microbial habitat had higher soil water content and lower pH(P<0.05).From the entire population structure of Stipa breviflora,The CaCO3 content was lower in the habitats dominated by older individuals,but the young Stipa community could not reduce the CaCO3 content.(4)The spatial distribution pattern of Stipa commity results in the heterogeneity of soil resources.The soil organic carbon,total nitrogen,available nitrogen,and available phosphorus all show the "fat island" effect of aquilaria and the "table aggregation" effect of soil nutrients.However,total phosphorus does not have a "fat island" effect.Moreover,different conch stipa have different effects on soil nutrients,and the larger the constellation,the more significant the difference.