Study On Plant-soil Feedback Of Typical Herbaceous Plants During Secondary Succession Of Abandoned Old-Fields In Loess Hilly Region, China

Plant-soil feedback has been widely used to explain the mechanism of plant communities succession.However,the studies of plant-soil feedback during secondary succession of abandoned old-fields in the Loess Hilly Region have rarely been reported.In this paper,the typical herbaceous plants of Setaria viridis(pioneer species),Artemisia sacrorum(middle succession stage),and Bothriochloa ischcemum(late successional stage),which at different restoration stages in the loess hilly region were chosen as study objects.A combination method of field and pot experiments were used to systematically analyze the effects of plant-soil feedback at different succession stages on plant characteristics,soil fertility and microbial community characteristics.The main influence factors that affecting the change of plant characteristics were discussed.Our aims were to provide a scientific basis for the restoration and reconstruction of regional ecosystems.The research results indicated that:(1)The effects of soil feedback on the photosynthetic characteristics,non-structural carbohydrate concentration,mineral nutrients concentration,biomasses and their allocation of S.viridis,A.sacrorum,and B.ischaemum all were significant.The plant–soil feedbacks and relative interaction intensity indexes were all significantly affected by soil feedback.The plant–soil feedbacks index can reflect the growth status of plants under different soil conditions,which was inhibited or promoted.The relative interaction intensity index can explain the interactions between species at different succession stages: the competition was mainly interspecific competition when the pioneer species growth in its mid-successional or late successional species;the competition was mainly intraspecific competition when the mid-successional or late successional species growth in its pioneer species;the interspecific and intraspecific competition have reached a balance when the mid-successional species growth in its late successional species;and the competition was dominated by intraspecific competition when the late successional species growth in its mid-successional species.(2)The effect of plant feedback on the soil fertility,microbial biomass and enzymatic activity were remarkable,but the influences varied with plant species and soil conditions.The relationship between the soil fertility and enzyme activity and plant biomass and non-structural carbohydrate concentration were closely related.The soil total nitrogen,water-soluble organic carbon,?-1,4-xylosidase and alanine aminopeptidase were the main influence factors that affecting the change of plant characteristics,and soil total nitrogen and ?-1,4-xylosidase were potential factors affecting species succession.(3)Plant feedback had an appreciable effect on diversity and structure of soil bacterial and fungal communities,and these impacts were significantly different due to different plant species and soil conditions.For soil bacterial and fungal communities of all the treatments,Proteobacteria and Ascomycota were the main dominant group at the level of phylum;Alphaproteobacteria and Sordariomycetes were the main dominant group at the level of class;at the level of order,Rhizobiales and Gemmatimonadales were the main dominant group in the soil bacterial communities,Agaricales and Sordariales were the main dominant group in the soil fungal communities.The soil bacterial community mainly affected plant biomass and non-structural carbohydrate.The soil fungal community mainly affected plant biomass,and had a certain impact on the non-structural carbohydrate and nutrient concentrations of plant species.The Chao1 index,Xanthomonadalesand and Acidimicrobiales of soil bacterial community,and Sordariales of soil fungal community were main influence factors that affecting the change of plant characteristics,and Chao1 index of soil bacterial community was potential factor affecting species succession.(4)Plant-soil feedback significantly affected the plants,microorganisms and soil stoichiometry,and the change characteristics were significantly different due to the difference of plant species and soil conditions.The stoichiometry of plant aboveground parts had a good correlations with soil,microbial biomass and enzymatic activity stoichiometry.The soil stoichiometry also had good correlations with microbial biomass and enzymatic activity stoichiometry.The plant stoichiometry were mainly affected by the soil available and water-soluble ratios of nitrogen to phosphorus in the process of vegetation restoration and succession.The above results indicated that plant-soil feedback at different succession stages of abandoned land had significant effects on plant characteristics,soil fertility and microbial properties,and the response characteristics of plant characteristics,soil fertility and microbial characteristics,however,varied due to different plant species and soil conditions.In the process of plant-soil feedback,soil total nitrogen,water-soluble organic carbon,?-1,4-xylosidase,alanine aminopeptidase,Chao1 index,Xanthomonadales and Acidimicrobiales of soil bacterial community,and Sordariales of soil fungal community were main influence factors that affecting the change of plant characteristics.Soil total nitrogen,?-1,4-xylosidase and Chao1 index of soil bacterial community was potential factor affecting species succession.