Effects Of Different Carbon And Phosphorus Compounds And Litters Addition On The Carbon And Phosphorus Stoichiometric Ratios Of Soil In Subtropical Forest

Carbon(C)is the core element for plant growth and development.Phosphorus(P)is the main limiting factor affecting forest productivity in subtropical regions.The coupling effect of C and P is widely present in the biogeochemical cycle of forest ecosystems,affecting the ecological stoichiometry of soil microorganisms and plants,which is critical to microorganisms and plant growth and development.Carbon and phosphorus compounds have simple structures and are easily absorbed and utilized by plants and soil microorganisms.Litters are an important source of energy and nutrients in subtropical forest soils,and have a significant impact on the cycling process of soil nutrients such as C and P.Therefore,exploring the dynamic changes of soil carbon and phosphorus nutrients,microbial biomass and enzyme activities and corresponding stoichiometric ratios under different inputs of carbon and phosphorus compounds and different inputs of litter are of profound significance to reveal the intrinsic mechanism of nutrient cycling in forest ecosystem.This study relied on the Fujian Normal University's Forest Ecosystem and Global Change Research Station in Sanming city,Fujian province-common garden study,and carried out two indoor experiments successively.The soil under Elaeocarpus decipiens Hemsl(EH)forest was used as the test soil,and 4 treatments including control(CT),carbon addition(C₆H₁₂O₆),phosphorus addition(KH₂PO₄)and simultaneous addition of carbon and phosphorus were set to carry out experiment 1.The litters of Pinus massoniana(PM),Lindera communis Hemsl(LCH)and Liriodendron Chinese(LC)were used as additives with significant differences in C:P and the forest soils of PM and LC with significant differences in soil C:P were used as substrates.There were 6 kinds of treatments:PM×PM,PM×LCH,PM×LC,LC×PM,LC×LCH,LC×LC in experiment 2.The main conclusions were as follows:(1)At the initial stage of cultivation,C+P treatment significantly increased the content of microbial biomass carbon(MBC).At the end of cultivation,P input would reduce MBC content.During the cultivation process,C in C+P treatment would inhibit the fixation of P by microorganisms.The C+P treatment could significantly improve the activity of?-1,4-glucosidase(?G)and inhibit the activity of acid phosphomonoesterase(ACP).In the middle and late stages of cultivation,the addition of C and P compounds had no significant effect on cellobiohydrolase(CBH).P addition inhibited the activity of ACP.C+P treatment promoted soil carbon mineralization more than C treatment,and there was a certain coupling relationship between C and P.(2)The input of litters increased the soil carbon source,increased the content of soil dissolved organic carbon(DOC)and MBC,promoted the turnover of the organic carbon pool,and reduced the secretion of?G and CBH.At the same time,it would aggravate the restriction of P in the microorganisms,increase the assimilation of P in the soil,lead to a decrease in the content of available phosphorus(AP),increase the coupling effect of C and P in the soil,and the coupling presented a dynamic change.Litters input promoted the soil mineralization of C and P in the early stage,and weakened the promotion in the middle and late stages.(3)In this study,the soil carbon and phosphorus nutrient cycles interacted and affected each other.ACP,microbial biomass phosphorus(MBP)and phosphodiesterase(PD)could account for 36.5%of the change in CO₂emission rate in experiment 2.The P demand of plants and microorganisms may,to a certain extent,drive microbial mineralization of soil organic carbon,affecting the carbon cycle.There were significant or extremely significant positive correlations between different forms of carbon,phosphorus nutrient.(4)During the cultivation,the addition of C increased MBC:MBP and had no significant effect on?G:ACP,while the treatments of P and C+P reduced MBC:MBP and significantly increased?G:ACP.The addition of litters of different C:P would increase the DOC:AP of soil,and the addition of litters to the soil of the same tree species had more significant effect on the increase of MBC:MBP and?G:ACP.