Three Kinds Of Herb Community Response To Exogenous Nitrogen Of Soil Nitrogen Mineralization And Microbial Structure In Al Forest-steppe Area

Forest steppe is the border area of forest and grassland, and the habitat diversity and species diversity are higher than adjacent forest and grassland, and the response to global change is very sensitive. Nitrogen deposition is one of the important phenomena of the global change, and the continuous nitrogen deposition increases the nitrogen content of the terrestrial ecosystem, which influences the process of soil nitrogen biogeochemical cycle. In order to master the effect of exogenous nitrogen on soil nitrogen mineralization in forest steppe zone, clear soil microbial diversity and structure in this study is located in the warm temperate deciduous broad-leaved forest and temperate grassland intersection of Shenyang Agricultural Uinversity teaching and research base of the town of Al (referred to as Al forest grassland township) as a platform to steppe community representative Agropyron desertorum, Calamagrostis epigeios, Artemisia frigida as the object, by adding artificial nitrogen (0,10, 25,40 kg N·hm-2·a-1)and indoor culture research response law of soil nitrogen mineralization to nitrogen combination method and microorganism diversity and population structure of 3 communities were determined by high-throughput sequencing method. The results are as follows:1. Al Xiang forest steppe zone of ice grass, Agropyron desertorum, Calamagrostis epigejos, Artemisia frigida three community soil nitrogen mineralization rate was 5.2-31.3 mg·kg-1·d-1,6.0-31.9 mg·kg-1·d-1,5.2-28.1 mg·kg-1·d-1, which nitrification rate respectively 6.1-22.3 mg·kg-1·d-1,7.2-20.1 mg·kg-1·d-1,5.8-16.6 mg·kg-1·d-1, accounting for mineralization of 60.2%,66.7% and 64.3%, mineralization process mainly to nitrification. Nitrogen addition significantly increased soil nitrogen mineralization rate and in Agropyron desertorum community in 10,25, and 40 kg N·hm-2 a-1 treatment were increased 50.1%,72.2%,83.3%, fAgropyron desertorum, Calamagrostis epigejos community for 37.5%,77.3%,82.1%,50.1%, 62.5% and 81.2% for Artemisia frigida community.2. The contribution of exogenous nitrogen to soil nitrogen mineralization was not enhanced with the increase of the amount of nitrogen, while the Artemisia frigida community was decreased by 40 kg N·hm-2·a-1 treatment. The contribution of exogenous nitrogen ammonification nitrification rate is higher than the. In Agropyron desertorum community, exogenous nitrogen significantly increased the organic nitrogen ammonification, and the addition of nitrogen concentration is higher, its contribution rate is high, and 40 kg N·hm-2·a-1 processing contribution of ammonification rate reached the maximum value of 26.3%, was significantly higher than that of 10,25 kg N·hm-2·a-1, which means for soil organic nitrogen ammonification process, exogenous nitrogen to the obvious role in stimulating and nitrogen addition is particularly evident early. In false reed Calamagrostis epigejos community,40 kg N·hm-2·a-1 processing contribution of ammonification rate is less than 20%, which is significantly higher than that of 10,25 kg N·hm-2 a-1. In the Artemisia frigida communities and 25 kg N hm-2 a-1 contribution rate of more than 40 kg N·hm-2·a-1. Too many exogenous nitrogen did not stimulate the enhancement of ammonification.3. By high throughput sequencing technology of soil microbia 16S rDNA, the diversity index of soil bacterial diversity of 3 communities in the forest steppe region of the.3 community Simpson index were Artemisia frigida (0.96)>Agropyron desertorum(0.94)> Calamagrostis epigeios (0.89). Shannon index for Agropyron desertorum(6.01)>Artemisia frigida(5.98)>Calamagrostis epigeios (4.72), Richness index for Artemisia frigida(275)> Agropyron desertorum(265)>Calamagrostis epigeios(252).4. Agropyron desertorum, Calamagrostis epigeios, Artemisia frigida community soil at the species level classification has eight the same advantage bacterial taxa (abundance>0.7% is the dominant group), they were parainfluenzae, hormaechei, longum, berve, fragilis, elsdenii, dispar and prausnitzii. They accounted for 40.72% Agropyron desertorum, Calamagrostis epigeios and Artemisia frigida community community soil bacteria of the total, 72.41% and 64.75%. In addition, the soil of the ice grass community contains one own species of lenta (abundance<0.6%), which can be used as an indicator of the Agropyron desertorum community. Artemisia frigida and Calamagrostis epigeios community has not detected the own species.