| The degradation of alpine wetlands was a serious threat to the ecological environment and sustainable development of animal husbandry in the Three-River source Region of the Tibetan Plateau.Under the severe environmental impact,only natural restoration is difficult and the efficiency results was slow.Human assistances were needed to accelerate the restoration and reconstruction of degraded wetlands.In this study,space-for-time substitution method was used.Based on water gradients and vegetation types,5 different stages of degraded wetlands were selected as experimental objects.To explore the characteristics of vegetation community structure and soil carbon,nitrogen,and phosphorus as wetland degradation under natural conditions,and we analyzed the effects of human disturbance on communities structure and soil nutrients.Results will provide basic data for the stability of the alpine wetland ecosystem on the Qinghai-Tibet Plateau,and also provide effective interference measures for the ecological restoration of the Qinghai-Tibet Plateau wetland.The main results and conclusions are as follows:1 Along with the degradation gradient,the vegetation height,coverage and biomass decreased gradually,and the community structure is complicated first and then simplified,compared with the non-degraded wetland,the extremely degraded wetland of river wetland decreased in height by 70.22%,decreased in coverage by 77.27%,decreased in aboveground biomass by 84.55%,and decreased in underground biomass by 86.75%.The extreme degradation of lake wetlands in coverage decreased by 50% compared with undegraded wetlands,in aboveground biomass decreased by 22.26%,in underground biomass decreased by 74.68%.Compared with the non-degraded wetland,the extremely degraded wetland of the floodplain wetland was reduced by 73.06% in height,71.59% in coverage,and 72.34% in aboveground biomass.2 Soil water miosture in river wetlands and lake wetlands decreased with increased degradation,The conductivity of river wetlands and floodplain wetlands decreased with the degree of degradation.Conductivity of lake wetland increased with increasing degradation.There was no significant change in soil pH,and the soil was alkaline.There was no obvious change rule of total nitrogen content in each soil layer with the degree of degradation The soil total phosphorus content of the extremely degraded wetlands in all soil layers of the river wetlands was significantly higher than other degraded wetlands,but no significant change in total phosphorus in lake wetlands and floodplain wetlands.Changes in total carbon,all soil layers in river wetlands and floodplain wetlands had a downward trend with the deterioration.The content of available phosphorus and alkaline nitrogen decreased significantly with the deepening of soil layer,and available phosphorus changed significantly with the deepening of degradation.Surface content of alkaline nitrogen in lake wetlands and floodplain wetlands decreases with increasing degradation.3 The impact of non-woven fabrics on the community height,coverage and biomass in the three types of degraded wetlands caused by human disturbance was the most significant.the community height of the extremely degraded and severely degraded wetland of the river wetland increased by 71.58% and 55.17%,the coverage increased by 55.56% and 56.25%,and the aboveground biomass increased by 35.14% and 23.65%,and the belowgroud biomass increased by84.55% and 80.91%.The total phosphorus content in the soils of lake wetlands and floodplain wetlands was significantly increased,and deeper degradation of the river wetland,too.After fertilization in river wetlands and lake wetlands,the total carbon content of the soil decreased significantly.The content of available phosphorus in the soils of river wetlands,lake wetlands at various stages of degradation and the floodplain wetlands with less degradation was significantly increased,significantly increased phosphorus content in mixed floodplain wetlands with high degradation. |
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