| Achnatherum inebrians widely distributed in rangelands in northern China.The infection rate of endophytic fungi-Epichlo?gansuensis in A.inebrians is nearly 100%in the natural grassland,so it is also called A.inebrians-E.gansuensis symbiont.The research for master thesis of the author had studied on refuge effect of a toxic grass,A.inebrians-E.gansuensis symbiont on plant composition and its diversity in continously overgrazing alpine grasslands in Xiahe county in Gansu province,alpine meadows in Guinan county in Qinghai province and desert grasslands in Alxa left banner in Inner Mongolia three types rangelands.Following that study,it was still regarded as the main material in this research to study:(1)its effects on neighboring forage plant composition in four continously overgrazing alpine meadows dominated with Kobresia spp.in Guinan,Haiyan,Huangyuan and Tianjun four counties in Qinghai province;(2)its effects on soil physical and chemical properties and soil microorganisms in its habitat in alpine grasslands in Xiahe county in Gansu province,alpine meadows in Guinan county in Qinghai province and desert grasslands in Alxa left banner in Inner Mongolia three types continously overgrazing rangelands.The main results are as follows:1.In this study,investigation was conducted in continuously grazed alpine meadows in above four sites of four different counties on the eastern Qinghai-Tibetan Plateau of Qinghai province,China.Each study site included a plot colonized by the unpalatable grass,A.inebrians-E.gansuensis symbiont(AI)and another plot in a neighboring meadows without A.inebrians-E.gansuensis symbiont(AO).The results showed:(1)palatable graminoids species were significantly different in the two plots:the AO plots were dominated by Kobresia spp.(sedges),importance values of Kobresia spp.in the AO plots of Guinan,Haiyan,Huangyuan and Tianjun were 0.86,0.66,0.80 and 0.73,respectively.Whereas the AI plots were dominated by Poa pratensis and Elymus nutans(grasses).In Guinan,Haiyan,Huangyuan and Tianjun AI plots,the importance values of P.pratensis and E.nutans were 0.45 and 0.18,0.31 and 0.34,0.22 and 0.47,0.16 and 0.66,respectively.(2)Graminoids diversity was significantly higher in the AI plots than that in the AO plots(P<0.05).The graminoids diversity in the AI plots was 4.08,1.24,1.79 and1.24 times that of AO plots in Guinan,Haiyan,Huangyuan and Tianjun,respectively.(3)Grasses had significantly more inflorescences in the AI than in the AO plots(P<0.05).In Guinan,Haiyan,Huangyuan and Tianjun AI plots,the number of inflorescences of P.pratensis and E.nutans per 1m~2 were 136.94 and 9.06,51.44 and 18.25,28.19 and 27.56,28.06 and 48.19.However,in the AO plots,there was only 0.25 inflorescences of E.nutans per 1 m~2 in Haiyan,and P.pratensis had no inflorescences.The dry weight of inflorescences of P.pratensis and E.nutans per 1 m~2 in Guinan,Haiyan,Huangyuan and Tianjun AI plots were 0.530 g and 0.237 g,0.240 g and 0.868 g,0.108 g and 1.210 g,0.260 g and 2.930 g,respectively.However,in the AO plots,there were only 0.003 g inflorescences of E.nutans per 1 m~2 in Haiyan,and P.pratensis had no inflorescences.Therefore,it was suggested that A.inebrians-E.gansuensis symbiont facilitated change of plant composition in degraded alpine meadows dominated by Kobresia spp.and increased grasses'proportion.2.The soil parameters and aboveground plant parameters of the plots with(AI)and without(AO)A.inebrians-E.gansuensis symbiont in three types of natural rangelands in Xiahe in Gansu,Guinan in Qinghai and Alxa in Inner Mongolia of north China were investigated.The results showed that:(1)the aboveground biomass of the three sites was significantly higher in the AI plots than that of the AO plots(P<0.05).The dry weight of aboveground biomass per 1 m~2 in Xiahe,Guinan and Alxa in AI plots was 2.25,2.96 and 4.12 times of that in AO plots,respectively.(2)Soil bulk density was significantly lower in the AI plots than that of the AO plots(P<0.05).The soil bulk density of the AI plots in Xiahe,Guinan and Alxa was 15.47%,1.97%and 16.16%lower than that in AO plots,respectively.(3)The total phosphorus content in the soil was significantly higher in the AI plots than that of the AO plots(P<0.05).The total soil P content of the AI plots in Xiahe,Guinan and Alxa was 47.06%,14.52%and 26.92%higher than that in AO plots,respectively.Therefore,it was suggested that A.inebrians-E.gansuensis symbiont facilitated to increase aboveground biomass and soil total P content,but reduce soil bulk density.3.Soil fungal parameters were investigated in the AI plots and the AO plots in three types of natural rangelands in Xiahe in Gansu,Guinan in Qinghai and Alxa in Inner Mongolia of north China.Our results showed that:(1)the plots dominated by the A.inebrians-E.gansuensis symbiont had a higher fungal diversity(P<0.05)and higher abundance of plant pathogens in soil(P<0.05)than plots that did not contain it.The soil fungal diversity of genera level of the AI plots in Xiahe,Guinan and Alxa was 20.15%,16.91%and 17.39%higher than that in AO plots,respectively.The richness of plant pathogens in the soil of the AI plots in Xiahe,Guinan and Alxa was 137.80%,32.22%and 19.25%higher than that in AO plots,respectively.(2)The soil fungal community had a positive correlation with plant community(r=0.688,P<0.05)and aboveground plant biomass(r=0.217,P<0.05)across the three study sites.(3)Structural equation model analysis indicated that:fungal diversity and microbial biomass were positively driven by higher plant biomass(P<0.05).(4)Abundance of plant pathogens in soil had a positive correlation with coverage of A.inebrians-E.gansuensis symbiont(P<0.05).(5)After analyzed with PERMANOVA,it was shown that the presence of A.inebrians-E.gansuensis symbiont significantly affected the soil fungal community(F=1.920,P=0.040).The results indicated that refuge effects of A.inebrians-E.gansuensis symbiont that drove the change of plant community composition and increased plant biomass,which then drove higher fungal diversity and microbial biomass in the soil.However,there was no significant difference in bacterial diversity between in the AI and the AO plots.There was no significant correlation between the aboveground plant communities and soil bacterial communities at species level in the three sites.But the aboveground plant communities had significant correlation with the soil bacterial community at genus and phylum level.It indicated that aboveground plant community and soil bacterial community are related to each other. |
PDF Full Text Request