Stoichiometry Characteristics And Plant Community Of Two Types Vegetation-covered Lands In A Gold Mining Area In Gannan

Mining is an important and basic industry for the development of national economy;mineral resources are the necessary material foundation for human social civilization.With the progress and development of human society,it`s demand for mineral resources is increasing accordingly.However,due to immature mining technology and people`s poor awareness of ecological protection,the mining activities often cause the destruction of landscape and surface vegetation,pollution of atmospheric,water and soil in the mining area,and have long-term negative impact on ecosystem health and the development of agriculture and animal health around the mining area.This study takes a gold mining area in Gannan,northeastern edge of the QinghaiTibet Plateau,as object,investigated the plant community of three types of vegetation cover types in the mining area: natural grassland,natural restoration grassland,and grassland recovery by Elymus nutans.Simultaneously,the total carbon(C),nitrogen(N),and phosphorus(P)contents in soil,plants and soil microorganisms and it`s ratios were determined.The research target is provides new ideas and theoretical guidance for vegetation restoration in mining area from the perspective of analyzing the changes in plant community structure and the ecological stoichiometry of soil,plants,and soil microorganisms.The main results are as follows:(1)After 5 years,both the land recovery by Elymus nutans and natural recovery,which plant species richness and plant species diversity were significantly lower than natural grassland(P <0.05).Compared with natural recovery,the species richness and biodiversity of grassland recovery by Elymus nutans was significantly lower after 5 years under the soil and climatic conditions are similar.The plant P content on the restored land is higher than the average level of natural grassland and Qinghai-Tibet Plateau,and the plant tissue N?P is between 3.8 to 5.2,indicated that the plants on the restored land were limited by nitrogen.(2)After mined,the soil pH and bulk density increased,while the soil C and N content significant decreased(P <0.05),but C?N was still consistent with natural grassland.The soil P content of the restored land was significantly increased(the soil C?P,N?P decrease)(P <0.05).The growth of plants and microorganisms on the restored land be restricted by C and N in the future,and it will be restricted by N on a longer time scale.There is no significant difference in soil bulk density,pH,C,N,and P content in the 0-30 cm soil profile of the restored land,it`s indicates the soil development in restored land is still in the primary stage.(3)In the restored lands,the soil microbial biomass C(MBC),and P(MBP)contents not showed significant change,while soil microbial biomass N(MBN)content significantly decreased(leaded MBC?MBN decreased significantly).The soil MBC?MBN?MBP on the surface of the natural restored land and recovery by Elymus nutans was 43.91?1.05?1 and 56.47?1.02?1,respectively,which MBN content are far lower than the average levels of alpine meadows in the Qinghai-Tibet Plateau and global grasslands.This ration indicates the land restoration will be restricted by N supply.