| As an important measure to control soil and water loss on the surface,vegetation restoration plays a mediating and leading role in the material cycle,energy flow and information transfer of the ecosystem.At the same time,it promotes soil development,improves soil characteristics and soil fertility,and significantly improves soil quality.Due to the special geographical structure and chemical properties of karst areas,the soil formation speed in karst areas is slow,the soil layer is shallow and the water holding capacity is weak,the biodiversity is gradually reduced,the soil and water loss is gradually intensified,the vegetation productivity is gradually decreased,and the self-restoration of ecosystem balance is difficult.Which has become a major ecological problem restricting the regional economic and social development of karst areas in southwest China.This study is based on Guizhou Caohai Nature Reserve(2171.7 m above sea level).The content of soil nutrients and the diversity and distribution characteristics of microorganisms in different landforms(non-karst landforms,karst landforms and landforms after vegetation restoration)were studied by spatio-temporal substitution method.(1)The differences and influencing factors of soil nutrients under different geomorphological environments;(2)The main factors affecting the spatial difference distribution of soil particle size in karst area;(3)The synergistic effect of soil-plant and its microbial effect in the process of vegetation restoration in karst area.The main conclusions are as follows :(1)There are obvious differences in soil organic carbon among different landforms,the SOC of surface soil in karst area is significantly lower than that in non-karst area,the ROC/SOC,DOC/SOC in surface soil is higher than that in non-karst area,and the soil quality and stability are low.Vegetation restoration changed the soil active organic carbon pool,and the soil carbon sequestration capacity was enhanced,but due to the influence of soil stability and dominant plant communities in the early stage of vegetation restoration,soil SOC was unstable and soil SOC content did not show an upward trend.However,d ue to the influence of topography,spatial location and plant richness,ROC/SOC and DOC/SOC in surface soil were larger than those in karst area.The basic soil physical and chemical indexes such as soil activity,plant coverage and soil bulk density are improved compared with those before restoration,which can prove that vegetation restoration can obviously improve the soil quality in karst area.(2)There are obvious differences in the distribution of soil total nitrogen in different landforms.Soil tota l nitrogen in karst area is significantly lower than that in non-karst area,and decreases with the increase of depth,and the content of ammonium nitrogen is lower than that in non-karst area.However,soil nitrate nitrogen is higher than that in non-karst areas.Different geomorphological environment and spatial location have great influence on soil nitrogen.In the early stage of vegetation restoration,soil nitrogen was fixed by plants,so that the content of soil total nitrogen and ammonium nitrogen wa s lower than that of non-vegetation restoration,but vegetation restoration improved the availability of soil nitrogen and plants were not completely restricted by nitrogen.so that the vegetation succession in this area can continue.(3)There is a significant difference in soil phosphorus content between non-karst landform and karst landform.Under different geomorphological vegetation communities,the soil phosphorus content of non-karst soil is the highest at 0-20 cm depth and decreases with the increase of soil depth,while the soil TP content of karst landform has little difference with the increase of soil depth.At the same time,the structure of non-karst soil aggregate is relatively better than that of karst landform.The change of phosphorus in karst landform is affected by the physical and chemical properties of vegetation,such as root system,microorganism,bulk density and so on;Vegetation restoration changed the structure of soil aggregates,and the soil phosphorus fixation capacity was gradua lly enhanced,but due to the influence of soil stability and dominant plant communities in the early stage of vegetation restoration,the changes of TP and AP contents in different communities were unstable,but in the surface soil affected by plant richne ss and the number of species,the phosphorus content in different vegetation communities was higher than that in karst areas.This can prove that vegetation restoration can obviously improve the soil quality in karst area;There is a positive correlation b etween species diversity,species composition and the contents of aggregates,TP and AP,indicating that with the restoration of vegetation and the improvement of community species diversity,soil aggregates and phosphorus in karst areas after vegetation restoration can continue to increase,further enhance soil stability and stabilize the effect of soil and water conservation.(4)According to the analysis of soil micro-biological community structure and α-diversity under the three dominant species,it was found that the main bacterial groups were Proteus,actinomycetes,actinomycetes,actinomycetes and some unknown taxa.At the same time,there were significant differences in soil physical and chemical properties under different geomorpholog ical environments,and the species and number of soil bacterial communities in the three geomorphological environments were significantly larger than those of fungi.There were significant differences in soil bacterial community diversity between karst lan dform and vegetation restoration at both phylum level and class level,in which the abundance of ascomycetes and actinomycetes was significantly higher than that of karst landforms.However,there was no significant difference between Proteobacteria and Alphaproteobacteria in the two landforms;The change of vegetation restoration significantly affects the abundance and αdiversity of soil bacteria,but does not affect the relative abundance of dominant bacteria.The difference of soil microbial community s tructure between the two geomorphological types may be reflected in their unique microbial communities.In the process of vegetation restoration,with the restoration and succession of vegetation communities,the richness and diversity of soil bacteria and fungi increased,and the structure of fine and fungal communities varied greatly.Soil p H,ROC,TP and soil water content were important factors affecting soil bacterial community. |
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