Effects Of Understory Plant Functional Groups Loss On Soil Ecosystem Multifunctionality In Eucalyptus Plantations

Ecosystem multifunctionality(EMF)is a critical sign for function and healthy of ecosystem,as well an essential foundation for sustainable development of forests and human society.The integrative research of biodiversity and ecosystem multifunctionality(BEMF)is considered as deepening of biodiversity and ecosystem function relationship(BEF)and an effective way for comprehensive understanding and accurate evaluating ecosystem structure,function and sustainability.Eucalyptus plantations are important short-rotation timber forests in South China,which now has the second largest areas of Eucalyptus plantations in the world with more than 4.5 million ha of Eucalyptus plantations.However,investigations about the effects of above-and below-ground biodiversity on soil EMF are still relative scarce at present.The influence of understory plant functional groups loss on below-ground biodiversity and the combining of above-and below-ground biodiversity on soil EMF are still unclear and further study was urgently needed.In the present studies,we examined how understory plant functional groups loss and the changing of soil microbial community structure and function influenced soil ecosystem function and processes,such as soil property,N transformation,C,N,P stocks and litter decomposition in a Eucalyptus plantations in South China.We also discussed the relationship between biodiversity(above-and below-ground)and soil EMF.And then we investigated the regulation pathway and relative contribution of biotic and abiotic factors on soil EMF by structural equation model.Our major results are as follows:(1)The relationship between different understory plant functional groups and soil nutrient cycling function was different.Woody plant functional group removal significantly decreased,while herbaceous and ferns functional groups removal markedly increased the availability of soil nutrient.Understory comprised multi-functional groups could facilitate litter decomposing due to higher diversity.(2)The response of soil N transformation rate to different plant functional group removal was different.Woody plant functional group removal significantly decreased,while herbaceous and graminoids functional groups markedly increased the soil ammonification,nitrification and mineralization rate.This could be contributed to the decreasing nutrient availability caused by woody plant functional group loss and increasing of nutrient availability by herbaceous functional group loss.(3)Woody plant and herbaceous plant functional group removal resulted in entirely different soil ecological effects.Woody plant functional group removal significantly decreased,while herbaceous functional groups markedly increased the soil microbial biomass C(MBC)and N(MBN),PLFAs mass and soil enzyme activity.This could be related to the significantly lower nutrient availability due to woody plant functional group loss.(4)There was a positive correlation relationship between above-and below-ground diversity.The relationship between above-and below-ground community diversity indexes were significant linear positive correlation.The relationship between above-ground diversity indexes were significant or extreme significant positive correlated with soil microbial community PLFAs mass.The impact of woody plant functional group removal on soil microbial community PLFAs diversity was the greatest,while the impact of herbaceous functional groups removal was limited.The underlying mechanism should be that the high plant diversity loss rate(40%-75%)after woody plant functional group removal and relative lower plant diversity loss rate(8%-25%)after herbaceous plant functional group removal.This result revealed that woody plant functional group was the main driver for changes in soil microbial diversity.(5)The relationship between soil microbial community diversity and soil ecosystem function was consistent with the relationship between plant diversity and soil ecosystem function.The increasing plant diversity facilitated the development of soil microbial community and maintenance of soil EMF.(6)The abilities to provide and maintain soil EMF varied in different plant function groups.Woody plant function group was superior to herbaceous plant functional groups in shaping EMF.Woody plant function group could provide diverse litter and root exudate,afford more substrate and habitat for soil microbial community,and consequently increase soil EMF,such as soil nutrient cycling,nutrient stocks,N transformation and enzyme activities functions.(7)In short-term successive rotation Eucalyptus plantations,the intensive management always leads to woody plant function group loss.Our result underscore the fact that woody plant function group loss decreases of nutrient availability,soil microbial community diversity and soil enzyme activities.This could reduce the ability to maintain EMF,and result in ecosystem degradation.Consequently,woody plant function group should not be removed in understory vegetation management.It should be retain to increase soil nutrient availability,soil microbial biomass and soil enzyme activities and maintain soil EMF.