Study On Plant-soil Feedback Of Dominant Shrub In Karst Area Of Guizhou

Plant-soil feedback can affect plant growth performance and plant community dynamics,which is important for understanding plant community succession and ecosystem diversity.As a common vegetation type in karst areas,shrubs play an important role in community succession and regional ecological environment protection.However,there is little research on the plant-soil feedback during vegetation restoration process in karst rocky desertification areas.In this study,typical dominant plants and soils in three stages of herbaceous,shrub and tree in karst area of Guizhou were taken as the research objects,and the effects of plant-soil feedback on plant characteristics,soil nutrients,soil enzyme activities and stoichiometric characteristics were studied by combining field and pot simulation experiments.To explore the relationship between soil environmental factors and soil enzyme activities and their stoichiometric characteristics in shrub communities,plant characteristics in different succession stages and soil environmental factors in dominant shrub communities,and to explore the main factors affecting soil enzyme activities in shrub communities and the main factors affecting the change of plant characteristics combined with RDA analysis.Based on this study,the plants that can improve the soil quality of the dominant shrub communities in karst areas are selected,which is of great significance for the control of rocky desertification in karst areas.The main results are as follows:(1)Plant feedback had significant effects on soil nutrients and the ratio of carbon,nitrogen and phosphorus of Pyracantha fortuneana and Zanthoxylum simulans communities.The contents of organic carbon and total nitrogen in rhizosphere soil under HG treatment were significantly higher than those under HB,HY and HP treatments,and those under YG treatment were significantly higher than those under YB,YW,YY and YP treatments.There were significant differences in soil stoichiometric ratios among the three types of plants at succession stage.C:P(63.56)and N:P(4.30)of herbaces were significantly lower than C:P(83.28)and N:P(5.62)of shrubs,and C:N(17.37)of trees were significantly lower than C:N(14.78)of shrubs.In general,the N and P availability of Imperata cylindrica and Miscanthus floridulus were high in the shrub community soil,while the mineralization rates of Betula luminifera and Pinus massoniana were low in the shrub community soil.(2)Plant feedback had significant effects on soil enzyme activities and enzyme activities C:N:P in Pyracantha fortuneana and Zanthoxylum simulans communities.The growth of Miscanthus floridulus and Betula luminifera significantly increased soil enzyme activity of shrub community by2%-4% and 0.3%-1.6% in several different succession stages.In the plant-soil feedback process,the changes of soil extracellular enzyme activity and its stoichiometric characteristics are similar to soil carbon,nitrogen and phosphorus nutrients,and are regulated by soil available nutrients.The stoichiometric characteristics of soil carbon,nitrogen and phosphorus and enzyme activity showed that the soil in the study area was limited by N and P,and the mean value of enzyme C:N was 0.40,significantly lower than the global level of 1.41,while the mean value of enzyme C:P and enzyme N:P were 0.71 and 1.780,respectively,significantly higher than the global level of 0.62 and 0.44.In the plant-soil feedback process,the changes of dominant plant biomass,non-structural carbon and carbon,nitrogen and phosphorus contents in different succession stages were mainly affected by soil N:P and p H.(3)Soil feedback significantly affected the non-structural carbon content,biomass and nutrient content of Imperata cylindrica,Miscanthus floridulus,Pyracantha fortuneana,Zanthoxylum simulans,Betula luminifera and Pinus massoniana.Compared with the native soil,the biomass of Imperata cylindrica,Miscanthus floridulus,Zanthoxylum simulans and Pinus massoniana were significantly decreased,the aboveground and total biomass of Pyracantha fortuneana in Zanthoxylum simulans community soil were significantly increased,and the biomass of Betula luminifera in Pyracantha fortuneana community soil was significantly increased.The root-shoot ratio of Miscanthus floridulus,Pyracantha fortuneana and Zanthoxylum simulans was significantly decreased,while that of Pinus massoniana was significantly increased.The non-structural carbon content in the above-ground parts of Imperata cylindrica,Miscanthus floridulus and Pyracantha fortuneana significantly decreased,the non-structural carbon content in the underground parts of Imperata cylindrica,Zanthoxylum simulans and Pinus massoniana significantly increased,and the non-structural carbon content in the underground parts of Pyracantha fortuneana and Pinus massoniana.significantly decreased.(4)In the plant-soil feedback process,there was a complex coupling effect between plants,soil and enzymes.There were significant differences in nutrient cycling and nutrient utilization in the soil of Pyracantha fortuneana and Zanthoxylum simulans communities with different plant growth.Plant roots played an important role in the above-ground and subsurface nutrient cycling function,and nonstructural carbon was more important for the nutrient cycling function in plants.The plant-soil feedback effect had significant effects on above-ground,underground and total feedback coefficients as well as competition coefficients of dominant plants such as Imperata cylindrica,Miscanthus floridulus,Pyracantha fortuneana,Zanthoxylum simulans,Betula luminifera and Pinus massoniana.And the variation characteristics of above-ground,underground and total feedback coefficients and competition coefficients were not consistent.The above results showed that the typical dominant plant-soil feedback in the three stages of herbaceous,shrub and tree in Guizhou karst area had significant effects on plant characteristics,soil nutrients and soil enzyme activities,but the effects of plant feedback on soil nutrients and soil enzyme activities were significantly different with different plant species and soil conditions.The effects of soil feedback on plant biomass and non-structural carbon content were significantly different with different plant species and soil conditions.In general,among the three typical advantages of herbaceous,shrub and tree stages,Miscanthus floridulus and Betula luminifera were beneficial to improve the soil barren status of Pyracantha fortuneana and Zanthoxylum simulans communities.These findings may provide a theoretical basis for clarifying the characteristics of soil quality changes during the vegetation restoration of karst rocky desertification areas.