Response Of Soil Ciliates Community To Ecological Restoration After The Implementation Of Returning Grazing To Grasslands Project, Maqu County Of Gannan Tibetan Autonmous Prefecture

The correlations between soil ciliates community structure and the project of returning grazing to grasslands in the basin of Maqu county of Gannan Tibetan Autonmous Prefecture were studied during the period of May 2015 to May 2016.Four sampling sites were set up according to the different restoration years.Eighty soil samples were collected in all sampling sites.Observation in vivo were used to analyse the ciliates community.Sample habitat,soil physical and chemical parameters were tested of all sampling sites,the results showed that:(1)In all sampling sites 73 plants were identified,belonging to 2 classes,17 orders,23 families and 56 genera.Advantage groups are Elymus,Potentilla,Seriphidium,Thalictrum and Ranunculus.The vegetation coverage,diversity index and evenness index of restored sampling sites were significantly higher than(P<0.05)unrestored sampling sites,and increasing with recovery years.(2)The results of soil physical and chemical parameters test showed that: soil water content and porosity were significantly increased and soil pH value were significantly decreased by implementing the project of returning grazing to grasslands,there was no statistical significance between each sampling sites of soil electric conductivity.The trend of soil organic matter and total nitrogen content is consistent.The site of A2(20 years restoring)was highest,A1 site(15 years restoring)and A3 site(10 years restoring)were second,and B site(unrestoring)was lowest.The trend of soil total phosphorus and total potassium content is consistent,that is,A2>A1>A3>B,there is no statistical significance between A3 and B sites.The trend of soil available nitrogen,available phosphorus,available potassium content is consistent,the trend is A2>A1>A3>B.(3)The results of soil ciliates community analyze showed that: a total of 95 soil ciliates were identified in all sampling sites,belonging to 9 classes.15 orders,21 families and 28 genera.Cluster analysis classified three restored A sites into the same cluster,classified unrestored B site into the other cluster,that means these two clusters at different soil environmental conditions.The species of soil ciliate increased by implementing the project of returning grazing to grasslands,dominant species gradually changed from Colpodida to Sporadotrichina,that's showed ciliates community tend to be more complex,and soil ecological environment was improved.Soil ciliates density was significantly increased by implementing the project of returning grazing to grasslands,the trend is A2>A1>A3>B,and structural parameters of soil ciliates changed.Soil ciliates diversity index,richness index,evenness index had improved in different degrees with the increasing recovery years.(4)The correlation analysis between soil ciliates community structure and soil physical and chemical parameters were tested,the results showed that soil total nitrogen,total phosphorus,total potassium,soil organic matter,soil water content and porosity were the key factors which affect soil ciliates community structure changes.Soil ciliates density was significant correlation(P<0.05)with all soil physical and chemical parameters,diversity index,richness index and evenness index were significant correlation(P<0.05)with soil total nitrogen,total phosphorus,total potassium,soil organic matter,soil water content and porosity.(5)The results of redundancy analysis suggested that the variation of ciliates communities were significantly correlated with the project of returning grazing to grasslands,soil total nitrogen,total phosphorus,total potassium,soil organic matter,soil water content and porosity were the key factors which affect soil ciliates community structure changes.The project is very positive to improve ecological environment in the region of Maqu county.