Study On Spatial Distribution And Seasonal Variation Of Microbial Community Structure In The Wetland Of Nanjishan (Poyang Lake)

Poyang Lake, China's largest freshwater lake has important wetland resources. However, in recent years, the influence of human activities on Poyang Lake wetland has gradually aggravated, causing the attention of scholars and government. In order to research the change characteristics of soil microbial communities of different vegetation types as the seasons and depths in Nanjishan, the samples were periodically selected from fixed sample points in the Wetland Reserve of Nanjishan of Poyang Lake. Then the soil nutrient content and physicochemical parameters, bacterial and fungal community structure and soil enzyme activity and their correlation of the different depths'soils (0～15cm,15～30cm,30～45cm) were analyzed with the seasons change (Jun2009, Oct2009, Jan2010, Oct2010, Jan2011) in three vegetation types sites:Carex cinerascens (CC), Triarrhera lutarioriparia (TL) and Cynodon dactylon (CD).The results showed that:(1) In Nanjishan, the contents of total Organic Carbon (TOC), total nitrogen (TN), soil moisture (SM) and ash free dry mass (AFDM) of the soils in the sites of Carex cinerascens and Triarrhera lutarioriparia were higher than those in the site of Cynodon dactylon. Also, the differences of TOC, TN, SM and AFDM were not significant between the former two sites, also the difference of C/N, TP, and pH of the three sites were not remarkable; The TOC, TP and TN in the sites of Carex cinerascens and Triarrhera lutarioriparia changed obviously along with the seasons, especially, those of the surface soils were remarkable. Meanwhile, the TOC and TN in the site of Cynodon dactylon changed slightly along with the seasons, expect TP, which showed a trend of N; the vertical distribution of TOC, TN, TP of the three sites in different seasons was consistent on the whole, were gradually reduced from top to bottom; pH increased gradually; and the C/N, SM and AFDM had no difference.(2) Bacterial community structures of the surface soils in the sites of Carex cinerascens and Triarrhera lutarioriparia of different seasons had high similarity, were different from that in the site of Cynodon dactylon. The bacterial community structures of the surface layer soils in the sites of Carex cinerascens and Triarrhera lutarioriparia changed significantly with the seasons, the samples in the same season had high similarity, but that in the site of Cynodon dactylon changed slightly with seasons, the samples in different seasons also had high similarity. The bacterial community structures of the middle layer soils were similar with the surface soils', but the biodiversity decreased significantly, the bacterial community structures of the under layer soils changed slightly, and there were no significant difference between the sites, and the biodiversity was extremely low. The change of the soil fungal community structure were different from the bacteria's, Overall, the sites of Carex cinerascens, Triarrhera lutarioriparia and Cynodon dactylon respectively formed a type, and were different among the sites of the three vegetation types; CCA analysis showed that the soil microbial community structures changes were mainly linked with TOC,TN and SM closely in Nanjishan wetland of Poyang Lake.(3) Soil enzyme activities in the three sites varied, overall laccase (ABTS) and phosphotase (PHOS) activities showed that CC>TL>CD, and changed obviously with the seasons; beta-glucosidase (BG) showed that the activities were different in the three sites every season and changed irregularly; overall, the xylanase (BX) activities showed that CD>CC>TL, and seasonal variation was also very obvious; the nagase (NAG) activities in the overall showed that TL>CD>CC, and seasonal variations was also very obvious; The soil enzyme activities of different layer soils were different; On the whole, with the increase of soil depth, soil enzyme activities decreased gradually; the results of correlation analysis showed that, the soil enzyme activities and environmental factors contacted closely, also TOC and TN significantly correlated, and was significant negative correlation with pH.