| In order to clarify the spatial distribution characteristics of vegetation and soil in different communities of desert steppe ecosystem in Ningxia and to evaluate the health of the grassland ecosystem,eight plant communities(glycyrrhiza uralensis community,Lespedeza potaninii community,Sophora alopecuroides community,Stipa breviflora community,Leymus secalinus community,Pennisetum flaccidum community,Nitraria tangutorum community and Artemisia frigidal community)in the desert steppe region of Yanchi County,were selected to divide the vegetation and soil.The species composition of different communities,ecological stoichiometric characteristics of plant and soil,spatial heterogeneity of plant-soil nutrients and health status of grassland ecosystem were discussed.The main conclusions are as follows:(1)Significant differences were found in diversity index of eight species in the study area:S.alopecuroides community had the highest Shannon-Wiener index,which was significantly different from those of L.potaninii community,S.breviflora community,L.secalinus community,Pflaccidum,N.tangutorum community and A.frigidal community(P<0.05);and the Pielou index of S.alopecuroides community was the highest,and that of L.secalinus community was the lowest,which was significantly different from that of g.uralensis community and S.alopecuroides community(P<0.05).S.breviflora community had the highest Simpson index,and there were significant differences with L.potaninii community,S.alopecuroides community and P.flaccidum community(P<0.05).S.alopecuroides community had the highest Patrick index,and had significant differences with the other seven communities(P<0.05).Different community types showed different Whittake index and Cody index.The ?ws index between L.potaninii community,P.flaccidum community,L secalinus community and A.frigidal community was larger,while the ?ws index between S.alopecuroides community,S.breviflora community,g.uralensis community,L.secalinu community and A.frigida community was smaller.The CJ and Cs index between N.tangutorum community and other seven plant communities were higher,and there were fewer common species.(2)Compared with the average content of carbon,nitrogen and phosphorus in grassland ecosystem in China,plant nutrients in the study area showed a pattern of high-carbon and low nitrogen and phosphorus elements.The contents of C,N and P in the soil of 8 communities in the study area were 10.35 g/kg,0.59 g/kg and 0.25 g/kg,respectively,which were lower than those of 11.12 g/kg,1.06 g/kg and 0.65 g/kg in the whole country.It was concluded that the C,N and P elements in the soil of the study area were relatively poor.The ranges of C:N in 0?5 cm,5?15 cm and 15?40 cm soil layers of different plant communities in the study area were 23.57?41.44,24.13?47.92 and 27.06?68.13,respectively,which were within the normal range.(3)The spatial heterogeneity of plant C,N,P contents in different plant communities and soil nutrients in different soil layers in Ningxia desert steppe was analyzed by classical statistics and geostatistics combined with GIS.The results showed that the total N and total P contents in different plant communities had strong spatial correlation,and the total C contents of plants had moderate correlation.The spatial heterogeneity of soil nutrients in different communities showed different change rules.(4)The areas with better health status were mainly concentrated in the northwest of Yanchi County.The health status of grassland in the southwest was less than that in the northwest.Most of the areas were in sub-health status.Only a few areas were in health status,and the area of grassland in alert and unhealthy status is less.In the same plant community,there are different health levels and spatial heterogeneity in different sample surfaces.The health status of grassland ecosystem is closely related to soil nutrients and vegetation diversity. |
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