Preliminary Study On The Soil Fungi In The Zoige Plateau Wetland

86 soil samples of 74 plots,located by GPS(Global Position System),were collected from the Zoige plateau wetland.Quantities of fungi were determined with the dilution plate technique.The soil fungi were identified and the correlations between fungi quantities and soil ecological factors which included soil fertility,soil humidity,land-use type and pH were analyzed by using the software of SPSS.According to the quantities,communities and their distribution,the fungi diversity was also studied.Potential which could antagonize to pathogen and decompose cellulose was also analyzed.Fungi quantity ranged from 10.8 to 1.41×10⁴(cfu·g^-1 dry soil).At the same plot,there were more fungi in upper(0～20cm) than in deeper soil layers(20～40cm).In different regions,fungi quantities from high to low were as follows:Nengwa(1865.263 cfu.g^-1 dry soil)＞Tangke(1543.246 cfu.g^-1 dry soil)＞Banyou(823.010 cfu.g^-1 dry soil)＞Xiaman (285.098 cfu.g^-1 dry soil)＞A'xi(134.751 cfu.g^-1 dry soil).In different land patterns,swamp land(3.80×10³ cfu·g^-1 dry soil)＞turf land(2.72×10³ cfu·g^-1 dry soil dry soil)＞meadow land (1.08×10³ cfu·g^-1 dry soil)＞sand land(0.27×10³ cfu·g^-1 dry soil).The spatial distribution of soil fungi mainly exhibited as strip zonal and circularity patterns.And the content of soil fungi increased gradually from outside toward center.The regions with low content(＜250 cfu·g^-1 dry soil) were mainly distributed in the north of A'xi and Heihe.The regions with high content(＞2500 cfu·g^-1 dry soil) were mainly located in the northeast of Nengwa and Tangke and Qi-Daoban of Banyou.A total of 771 fungi isolates were collected from the soil in the Zoige plateau wetland. 25 fungal genera were identified.Among these genera,Penicillium spp.,Trichoderma spp., Fusarium spp.,Pythium spp.,yeast,Aspergillus spp.and Mucor spp.were isolated more frequently at 98.68%,63.51%,31.08%,21.63%,33.78%,25.68%and 29.73%in these samples,respectively.Their proportions of quantity were 21.79%,12.71%,4.41%,3.89%, 4.67%,3.50%and 3.63%,respectively.Soil fungi quantities were closely correlated with soil ecological factors.At some degree,fungi quantity was correlated with total potassium,organic matter and water contents positively,but with pH,total phosphorus,rapidly available potassium,rapidly available nitrogen,rapidly available phosphorus,slowly available potassium and total nitrogen negatively.The fungi quantity had a significantly negative correlation with soil available potassium and rapidly available nitrogen.In addition,the relationship was noticed between soil fungi quantities and community diversity.The quantity of fungi had a low negative correlation with the abundance(S) and Shannon-wiener's diversity(H′).The abundance(S),Shannon-wiener's diversity(H′),Pielou's evenness(E) and dominance index(D) were 6.8649±3.0805,0.7650±0.2498,0.9697±0.0627 and 0.2418±0.1353, respectively.Fungi quantity in Nengwa was the most,but in Xiaman the abundance(S) and Shannon-wiener's diversity(H′) were the most.They were 8.400 and 0.8759,respectively.98 Trichoderma isolates were isolated from the Zoige plateau wetland.There were 19 isolates of T.harzianum,29 isolates of T.aureoviride,10 isolates of T.atrooviride,12 isolates of T.koningii,13 isolates of T.viride,7 isolates of T.longibrachiatum,6 isolates of T.asperellum,2 isolates of T.cerinum,respectively.The test of hyphal growth rate showed that most of Trichoderma strains grew rapidly, and were the stronger competitor for space and nutrition resource.The result of the dual culture showed the inhibition rates of hypaal growth of Trichoderma against Rhizoctonia solani were 33.43%～77.99%,T1,T2 and T5 showed higher inhibition rates than 75.00%. The non-volatile substances of the isolates tested had obvious inhibition to hyphal growth of R.solani,among them T23,T27,T25,T28 and T32 showed higher inhibition rates.From the primary screen by Hechisum medium,there were 29 Trichoderma strains having the ability of decomposing cellulose,which were screened from all 98 Trichoderma. There were 7 Trichoderma having higher ability of decomposting cellulose from the re-election holding on cellulose-congo red medium.