Modulation Of Soil Microbial On The Physiological Characteristics Of Sapindus Saponaria Under Soil Acidification

With the effects of global change and human activities,soil acidification has been a ubiquitous environmental issue in southern China.Plant-soil feedback（PSF）plays an important role in the response of individual plants and the populations to soil environmental changes,and then is the hot research field for forestry ecology.Sapindus saponaria is an important economic tree species in subtropical area.It has high dependence on mycorrhiza and can grow well in weakly acidic soil.However,the research about underlying mechanism of soil microbial on the growth of S.saponaria under soil acidification is still unknown.In this research,we focused on the S.saponaria saplings,quantified the responses of morphology,growth,leaf photosynthetic capability,osmolyte accumulation,soil enzyme activities and soil fungal community composition of S.saponaria to soil acidification by using a two-phase method of PSF.This research not only enrich the mechanism for the growth of S.saponaria,but also provide guidance for the culture and management of this species grown in areas exposed to soil acidification.The main results are as follows:（1）Soil acidification significantly decreased alkaline phosphatase activity（ALP）,leaf area（LA）,root length,surface area of root,average dimeter of root,root volume,total dry weight,root:shoot ratio,chlorophyll a concentration（Chla）,chlorophyll b concentration（Chlb）,carotenoid concentration（Car）,net photosynthetic rate（P_n）,stomatal conductance（g_s）,intercellular CO₂ concentration（C_i）,transpiration rate（T_r）,maximum photochemical efficiency of PSII（F_v/F_m）,effective quantum yield of PSII(Y_ield),photochemical quenching（q _P）,proline concentration（Pro）,soluble sugar concentration（SS）and soil acid phosphatase activity of S.saponaria.The live soil filtrate and AM fungi soil filtrate significantly increased mycorrhizal colonization,succinate dehydrogenase activity（SDH）,ALP,specific leaf area（SLA）,chlorophyll a/b（Chla/b）,F_v/F_m and decreased Chlb of S.saponaria in comparison with sterile soil filtrate.Interaction between soil acidification and different soil filtrates posed significantly effects on mycorrhizal colonization,SDH,ALP,LA,SLA,root length,root:shoot ratio,Chla,Chlb,Chla/b,g_s,T_r,F_v/F_m,Pro,SS,soluble protein concentration and soil urease activity.（2）With the intensification of soil acidification,the PSF effect value varied with the inoculation of different soil filtrates.The negative PSF values aggravated with the live soil filtrate,while soil filtrate with AM fungi induced the negative PSF values to tend to be positive.（3）Correlation analysis showed that PSF was significantly positively correlated with surface area of root,average dimeter of root,root volume,Chla,Chlb,P_n,F_v/F_m,Y_ield,q _P,SS,soil acid phosphatase activity and significantly negatively correlated with Shannon index and relative abundance of pathotroph of soil fungal community.In conclusion,soil acidification inhibited the root functional traits,biomass accumulation,leaf photosynthetic capability,osmolyte accumulation and soil acid phosphatase activity,whereas inoculation with live soil filtrate and AM fungi soil filtrate promoted the mycorrhizal colonization,mycelial enzyme activity and leaf photosynthetic capability.With the intensification of soil acidification,inoculation with live soil filtrate inhibited the growth of S.saponaria,whereas soil filtrate with AM fungi could,to some extent,promote the growth of host plants,which could be related with the stress-gradient dependence of mycorrhizal efficiencies.Furthermore,root functional traits,leaf photosynthetic capability,soluble sugar and soil acid phosphatase activity may be positive driving factors for PSF,whereas fungal diversity and the relative abundance of pathotroph could be the negative ones for PSF variance.