Response Of The Soil Ciliate Community In Alpine Meadow To Various Concentration Gradient Of Nitrogen Fertilizer

The community of soil ciliate was studied using vivo observation and “three level ten-fold dilution method” in Alpine Meadow soil with various nitrogen fertilizer levels in Gannan, Gansu Province from April2011to December2012, as well as the physico-chemical factors of soil were determined. The sampling sites were chosen as followed: three fertilized sites with different nitrogen fertilizer levels (N1=5g/m~2、 N2=10g/m~2、 N3=20g/m~2) and a control site (N0=0g/m~2).1. The examination of soil physico-chemical factors indicated that soil water content was increased as the increasing of the nitrogen fertilizer levels, while the pH value falled. The soil available nitrogen was highest in the soil with the nitrogen fertilizer levels of20g/m~2. The correlation analysis indicated that available nitrogen was obviously positively correlated with the fertilizing amount (p <0.05), while the soil pH value was significantly negatively correlated with fertilizing amount (p <0.01). There was none obvious correlation between water content and temperature of soil and fertilizing amount (p>0.05).2. The research results on the response of soil ciliate community to the different nitrogen fertilizer levels in Alpine Meadow soil were as followed:A total of121species were identified, belonging to9classes,16orders,28families and47genera in this study. The distribution of soil ciliate was significantly different among the various sampling sites. As the increase of fertilizing amount, the similarity of soil ciliate community between sampling sites was decreased. Meanwhile, the amount of family, genus and species of ciliate was decreased and the community compositionof soil ciliate tended to be homogenisation with the increase of fertilizing amount.The dominant groups and species of soil ciliate were changed after fertilization. Sporadotrichida was the dominant group in the control site N0and the lower fertilizing amount site N1, Sporadotrichida and Colpoda were the dominant group in the middle fertilizing amount site N2, Colpoda was the dominant group in highest fertilizing amount site N3. Colpoda steini, Maupasi, Homalogastra setosa, Leptopharynx eurostoma, Euplotes muscicola, Oxytricha minor, Notohymena selvatica, Colpoda cucullus, Spathidium muscicola Gonostomum strenuum and Halteria grandinella were the dominant ciliate in the sampling sites N0. In the sampling site N1, Gonostomum strenuum, Drepanomonas obtuse, Colpoda edaphoni, Colpoda inflata,Colpoda reniformis and Halteria gannanensis were dominant, and Oxytricha granulifer, Drepanomonas obtuse, Colpoda cucullus and Colpoda aspera in the site N2. The dominant species in the sampling site N3were including Colpoda cucullus, yclidium muscicola, Drepanomonas obtusa, Colpoda aspera and Colpoda edaphoni.The species richness of soil ciliate decreased gradually with the addition of fertilizing amount. The abundance of soil ciliate increased significantly at lower of fertilizing (N1、N2), while then decreased in site N3. The species diversity index had the similar pattern with that of the species number. Meanwhile, the community C/P index increased gradually.The cluster analysis based on the environmental factors, species distribution and the parameters of ciliate community indicated that the more fertilizing amount resulted in a lower similarity with the control site.3. The correlation analysis indicated the species of soil ciliate was mostly influenced by pH value and available nitrogen, it had an obvious positive correlation with pH value (p <0.01), while the obvious negative correlation with available nitrogen (p <0.05) was detected. The abundance of soil ciliate was mostly influenced by water content, it had an obvious positive correlation with water content (p<0.05). The species diversity index had significant positive correlation with pH value, too (p <0.01).4. The seasonal dynamics of species richness of soil ciliate was shown as followed: winter (90species)> summer (73species)> autumn (68species)> spring (59species) while the seasonal dynamics of the abundance of soil ciliate was shown as followed: winter (285ind./g)> autumn (228ind./g)> summer (163ind./g)> spring (141ind./g). the statistical analysis indicated that the seasonal dynamics of soil ciliate was significantly influenced by water content.