Effects Of N And P Additions On Ecological Stoichiometric Characteristics Of Soils And Fine Roots In A Subtropical Evergreen Broad-leaved Forest,Tiantong

Ecological stoichiometry is a discipline that studies ecological processes and effects based on element ratios,which provides new ideas to address the interaction of soil-plant with the cycle of carbon(C),nitrogen(N)and phosphorus(P).C,N and P are the most studied elements in ecological stoichiometry.N and P are the limiting nutrients for plant growth,which are closely related with the structural material C.The atmospheric N deposition is increasing,which will affect the N cycle of terrestrial ecosystem.Therefore,the P limitation may be more serious in P-limited subtropical ecosystems.The C:N:P stability of ecosystem is vital to the material cycling and nutrient balance.However,the response of ecological system to complex climate change can not be predicted scientifically and evaluate accurately,due to the lack of ecological explanation on C,N and P stoichiometry in forest ecosystem under the interaction effects of N and P additions.This study was conducted in subtropical evergreen broad-leaved forest(Schima superba)with P-limitation,Tiantong,Zhejiang Province.N and P additions with four treatments(CK:0 kg N/hm2/yr;+N:100 kg N/hm2/yr,+P:50 kg P hm2/yr and +NP:100 kg N/hm2/yr+50 kg P/hm2/yr)were conducted in twelve 20×20 m plots.Soils and fine roots were collected in four seasons.Effects of N and P additions on C,N,and P stoichiometry of soil,fine roots and fine root-soil system were analyzed.The main results are as follows:(1)N and P additions had no significant effect on soil organic carbon(SOC)and soil total N(TN).Soil total P(TP)was not affected in +N treatment,but significantly increased in +P and +NP treatments.In treatments of N and P additions,changes of soil C:N and C:P were significantly correlated with soil TN and TP respectively,and the change of soil N:P were significantly correlated with soil TN and TP,but stronger correlated with soil total P.(2)N and P additions significantly increased fine root C,but had no significant effect on fine root TN.Fine root TP did not affect in +N treatment,but was significantly increased in +P and +NP treatments.With N and P additions,the change of fine root C:N was mainly regulated by fine root TN,while the change of fine root C:P was regulated by fine root C and TP,but stronger correlated with fine root total P.And the change of fine root N:P was regulated by fine root N and P.(3)In treatments N and P additions,the fine root TP was significantly correlated with soil TP.Microbial C and N showed significant correlationship with SOC and soil TN,respectively.No significant relationship between ecological stoichiometric characteristics of fine roots and those of microbes were found.In conclusion,soils and fine roots were more responsive to +P addition than + N addition in this P-limited forest.In N and P additions,there was significant relationship between ecological stoichiometric characteristics of microbes and those of soils in N and P additions.These results provided a theoretical basis for the further study of the ecological stoichiometry of terrestrial ecosystems with climate changes.