Effects Of Dominant Species Identity And Community Type On Soil Extracellular Hydrolase Activity In The Songnen Grassland

Dominant plant species is a classical concept in ecology,whose knowedge is mainly based on studies of the characteristics of the aboveground parts of the community.However,with the development of ecology,more attention has been paid to belowground ecological processes and functions,the applicability of the traditional concept of dominant species has been challenged to some extent.Dominant species significantly affect the community species composition,diversity,and productivity,which further regulate the belowground community and biogeochemical processes.Soil extracellular enzymes,mainly produced by plants and soil microorganisms,control soil organic matter degradation,regulate soil nutrient cycling rate and thus are the indicators of soil biogeochemical processes and functions.Therefore,soil extracellular enzyme activities may respond sensitively to the changes of plant community type,community species composition,and dominant species identity.However,the effects of dominant species identity and community type on soil extracellular enzyme activities and the effects of dominant species on soil extracellular enzyme activities of its community in semiarid grassland ecosystems are still poorly understood.Given this,we selected three plant communities(including Leymus chinensis,Calamagrostis rigidula,and Lespedeza daurica)in the Songnen grassland for field in-situ investigation.We established the comparison of the effects of three dominant species(called as“dominant species level” below)and their communities(called as “community level” below)on soil extracellular hydrolase activities(EHAs)and soil physiochemical properties,determined the contribution of each dominant species to community level soil EHAs,and examined key factors affecting these relationships in the Songnen grassland.We aim to answer:(1)How soil EHAs respond to dominant species identity and community type;(2)Whether the soil factors affecting soil EHAs of dominant species level and community level are different;(3)The role of dominant species on soil EHAs of its community.The main conclusions are as follows:(1)Soil EHAs at the dominant species level were significantly different,but the difference at community level was only observed between L.chinensis and L.daurica communities.Meanwhile,the species composition between L.chinensis and L.daurica communities were obviously different.These suggested that dominant plant identities had significant effects on their rhizosphere soil EHAs,and the difference of soil EHAs at the community level mainly depended on vegetation composition(including dominant species identities).(2)Soil EHAs at dominant species level were significantly correlated with soil p H and electrical conductivity.Also,soil EHAs at the community level was significantly associated with soil moisture and total soil carbon.This meant that different soil factors drove soil EHAs at the dominant species level and community level.(3)There was a high similarity of soil EHAs between each dominant species rhizosphere and its corresponding community,indicating that dominant species largely determined soil EHAs of its community.In conclusion,our study highlighted the effects of dominant species on soil EHAs of its community,providing a new insight into exploring the substantial impacts of dominant species on belowground community functions in the Songnen grassland and expanding our understanding of the functions of dominant species on belowground biogeochemical in semiarid grassland ecosystems.We thought that we should pay more attention to the role of dominant species on belowground functions,which would help to reveal the relationship between the dominant species and other species in the community and further understand the mechanism of ecosystem community construction and system function.