| Recent findings on global warming and human-induced disturbances depicted that the area of alpine wetlands has successively declined to meadows.Moreover,further alteration of meadows affected the overall pasture production,reduction in the conservation of soil and water resources and intensified the degree of desertification.Amidst all,the dilemma of ‘black soil beach' in severely degraded meadow is particularly prominent.However,the artificial grassland system is often used to overcome this hitch.Given the importance,the study intended to analyze whether the alteration and relationship of soil microorganisms and organic compounds could explain the status of degraded alpine wetlands,degraded alpine meadows and restored alpine meadows.To address this issue,five kinds of sampling sites such as alpine wetlands,alpine swamp meadows,alpine meadows,alpine degraded meadows,and artificial grasslands were determined.Various types of soil and vegetation samples were collected from the field to determine the characteristics of soil and vegetation.The functional diversity of soil microbial carbon metabolism and microbial community structure were determined by BIOLOG ECO microplate and high-throughput sequencing.The species and content of soil organic compounds were determined by liquid chromatography-mass spectrometry.Based upon results,the following conclusions were drawn.1.The vegetation characteristic during the succession of alpine wetlands to alpine meadows didn't change significantly.The reduction in content of soil water,total organic carbon,coverage and biomass of the degraded meadow was in relation to the intensity of degradation.While the soil pH and bulk density increased gradually.Compared to degraded meadows,the artificial grassland vegetation characteristic significantly increased.During the process of desiccating wetlands,the total organic carbon content of the swamp meadows remained the highest.2.The microbial utilization rate of carbon in swamp meadows was the highest during the process of wetland desiccation.Moreover,the utilization of carbon sources by degraded meadow soils was gradually reduced.Though,insignificant increase in the utilization rate of carbon sources was observed in artificial grassland system.Despite this,the artificial grassland establishment with time didn't affect the overall utilization rate of soil microbial carbon sources.The principal component analysis showed that there were differences in the utilization of carbon sources between different soil microorganisms.RDA analysis portrayed that the soil water content,bulk density,soil nutrient(TOC,TN,TP,C/N,N/P)and vegetation coverage have a significant impact on the functional diversity of soil microbial carbon metabolism.3.The alteration in predominant microbial communities of soil microorganisms were in relation to the process of degradation and restoration of wetlands and meadows.Furthermore,the relative abundance of dominant microorganisms in artificial grassland with a period of time changed with ‘V' type.The relative abundance of soil microorganisms and Chao1 value of soil microorganisms was significantly correlated with soil physical and chemical properties.A negative correlation was seen among the Chao1 value of the bacteria and actinomycetes and the vegetation coverage while Chao1 value of the fungi had a positive correlation with the vegetation height and biomass.4.During the drying process of wetlands,there was no significant change in the soil organic content.In relation,as the meadow degradation extended,the content of amides,sterols,ketones and fatty acids changed significantly.And the content in the sandy grassland increased significantly.There were significant differences among different dominating toxic weeds of black beach.Similarly,a significant increase in compounds like(Malonic acid,trehalose,PGA3,D(+)-melezitose)within the artificial grassland was observed after 2 years of establishment.5.The structural equation model made for this experiment elucidated the interactions among vegetation characteristic,physical and chemical properties of soil,soil microbes as well as soil organic compounds.Soil moisture was considered as an intermediate factor in this model.The study inferred that the soil microbes and organic compounds were significantly different in alpine wetlands,meadow degradation and restoration processes whereas they were significantly correlated with environmental variables.Therefore,the indexes have probably appropriate depictions regarding wetlands,meadow degradation,recovery stages and conditions. |
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