Relationships of dominant species root activity,plant community characteristics and soil micro-environment in artificial grassland over different cultivation periods

Three river source regions were contrasted with heavily degraded grassland(black soil patch) by studying,the root activity of Elymus nutans(the dominant species),plant community quantity characteristics,soil physicochemical properties and activities of six soil enzymes over six and ten years of artificial grassland.The relationship of root activity of the dominant species,community quantity structure and soil micro-environment of artificial grassland were analysed.The biomass of grass became the largest part of the plant community and legumes began to invade in six year old artificial grassland.The biomass of grass in ten year old artificial grassland was lower than that of the six year artificial grassland,in which the biomass of forbs became the largest component of the plant community.There was an immense invasion of legumes,and sedges also began to emerge.Soil physicochemical properties had marked changes in artificial grassland.Soil moisture,organic matter,total nitrogen,available nitrogen,total phosphorus and available phosphorus increased while soil bulk density,temperature and pH value decreased.The activities of invertase,alkali phosphatase,protease and urease of six year and of ten year artificial grassland increased but the polyphenol oxidase activity was reduced.The catalase activity was not obviously changed.Plant community characteristics were positively related to soil moisture,organic matter,available nitrogen,total phosphorus and hydrolysis enzymes whereas plant community characteristics were negatively related to soil bulk density,pH value and polyphenol oxidase.The root activity of E.nutans was negatively related to soil compaction,soil moisture,pH value,protease,alkali phosphatase,polyphenol oxidase.Analysis showed that the variation trend of root activity of E.nutans in 6 year artificial grassland was more than that in 10 year artificial grassland.The changes in soil micro-environment led to increasing plant competition for soil resource utilization.The root activity of plants changed with the different species composition and biomass distribution of the plant community.