Response Of Soil Ciliate Community To Different Patterns Of Returning Farmland To Forest In Maiji District, Tianshui City

Since the implementation of the ecological restoration project of returning farmland to forest to in 1999,the scientific evaluation of the improvement of the local ecological environment after the project implemented is an important part of perfecting the project.Soil ciliates are the highest forms of single-cell organisms and have many typical features,morphological diversity,widely distributed and heterokaryotic that can be used as a good indicator organism in response to environmental changes.Therefore,in this study,we selected the returning farmland to forest region in Tianshui City,Gansu Province as an experimental sample area.By studying the characteristics of soil ciliates community,this study aims to reveal the effect of returning the cultivated land to forest region in the project area.In June 2016,three ecologically restored sampling sites were selected from Maiji Area of Tianshui City: Robinia pseudoacacia(A),Malus pumila(B),Juglans regia × Zanthoxylum bungeanum mixed forest(C)and one cultivated land(CK)sampling site as a control.After that,soil samples were collected in four seasons.Identification and quantification of ciliates were carried out by employing "observation in vivo","protargol impregantion techniques" and "directing-culture counting method",to study the difference of soil ciliate community composition between three ecologically restored sampling sites and one control sampling site.Meanwhile,the investigation of the vegetation condition in the ecological restoration areas were conducted,physical-chemical parameters of the soil were also measured for each sampling site including soil water content,soil temperature,porosity,p H,conductivity,organic matter,total potassium,total phosphorus and total nitrogen.The results showed that:(1)A total of 68 vegetation species were identified in the ecological restoration areas,belonging to two class,18 orders,26 families and 59 genera,of 36 species in ecological forest site(A),and 23 species and 32 species of two different economic forest sites(B)and(C).Comparison of vegetation community characteristics parameters was as follows: ecological forest site> economic forest sites.(2)The return engineering has obvious influence on the following physical-chemical parameters: the soil water content,organic matter and total nitrogen content in the ecologically restored sampling sites were significantly higher than CK(P< 0.05),and the ecological forest(A)was higher than economic forest(B,C);and the p H value of the ecologically restored sampling sites tends to be neutral when compared with CK sampling site;then the soil porosity is improved,and the ecological forest is superior to the economic forest.(3)In this study,a total of 139 ciliate species were identified,belonging to nine classes,20 orders,39 families and 55 genera.Sporadotrichida was the dominant group,Haptorida and Colpodida were the subdominant groups.The differences among the sampling sites showed that the species number and density of the ecologically restored sampling sites were significantly higher than those of the CK sampling site(P< 0.05),i.e.,A(93 species;127.73 ind/g)> C(85 species;120.06 ind/g)> B(80 species;84.75 ind/g)> CK(52 species;38.06 ind/g);and the ciliates community parameters also showed that the ecologically restored sampling sites were significantly higher than the CK sampling site(P< 0.05),that is,with the improvement of soil habitat,ciliates community composition tends to be complicated.Cluster analysis,MDS analysis and Jaccard community similarity analysis showed that there were significant differences in species distribution and community composition between the ecologically restored sampling sites and the CK sampling site.Among the three restored sampling sites,A and C were the most similar.(4)Correlation analysis between the ciliate community characteristics parameters and the vegetation communities characteristics parameters,and the soil physical-chemical parameters,respectively,showed that the characteristics of the ciliates community were closely related to the aboveground vegetation,and the water content,organic matter,total nitrogen and p H were the dominant physical-chemical parameters affecting the ciliate community composition.In conclusion,by comparing the difference of ciliates community between the ecologically restored sampling sites and the CK sampling site,which was indicated that the ecological restoration project of returning farmland to forest has achieved good results,and the return effect ecological forest is the best,followed by mixed economic forest,pure economic forest is weak.