Functional Traits Of Ectomycorrhizal Roots In Abies Fargesii Var.faxoniana And Variations With Environments

Abies fargesii var.faxoniana(Rehder & E.H.Wilson)Tang S.Liu is an ancient fir plant,a typical ectomycorrhizal tree species,which has survived and evolved in global climate changes after several centuries and become a unique species in China.A.faxoniana mainly distributed in western Sichuan province of China where the important habitat of giant pandas.This research explored the effects of ectomycorrhizal(ECM)strategies on A.faxoniana under different environmental conditions.By using spatiotemporal substitution method,this study surveyed the tree species with different altitudinal gradients and geographic locations.The objectives of the study are determine and elucidate(1)the ECM strategy in foraging nutrients of A.faxoniana at different environmental conditions;(2)the reseponse of the ECM strategy of A.faxoniana to the environmental change,including climate factors and soil factors.By addressing the above mentioned issues,this study aims to elucidate the response of the nutrient uptake strategy of ectomycorrhizae in A.faxoniana to environmental change.Major findings are as follows:1.ECM funtional traits in A.faxoniana was significantly different across the altitudes in Wolong Nature Reserve.Our research suggested that the foraging strategy of ECM roots was extensive strategy at lower altitudes(2850 m,3000 m,3194 m asl),with high fine root proliferation and morphological differentiation.While intensive foraging strategy of ECM roots in A.faxoniana at higher altitudes(3413 m,3593 m asl.)was reflected,with high ECM root tips per unit root biomass and the formation of contact exploration type.2.Soil temperature was the most important soil factor in influencing ECM in A.faxoniana,followed by soil p H.The formation of ECM root tips were enhanced under the low soil nutrient availablity.As the totally different responses of soil exploration types to soil enzymes,contact and medium-distance exploration types were negatively related with soil enzymes,while short-distance exploration type positively related with that.This research concluded that ECM taxa with the short-distance exploration type was the major taxa for enzymatic serection.3.Compared to soil factors,climate factors more employed in affecting the proliferation and morphology differentiation of ECM roots.This research showed that fine root biomass,short-distance exploration type and morphology diversity of ECM roots increased with the increasing air temperature and/or decreasing precipitation,suggesting that proliferation and morphology differentiation of ECM roots in A.faxoniana were facilitated under warming and/or drying.While the ECM traits including ECM root tips per unit biomass,contact exploration type,colonization ratio and superficial area of ECM root tips,being declined with the increasing air temperature and/or decreasing precipitation,suggesting that absorptation ability of ECM root tips in A.faxoniana declined under warming and/or drying.4.Plant N and P nutrients in A.faxoniana were positively related with functional traits in ECM root tips,including colonization ratio,the ratio of living to dead root tips,ECM root tips per unit biomass and superfical area of ECM root tips;whilst negatively related with ECM root proliferation and morphological differentiation.Accordingly,it suggested that there is a trade-off between the formation and nutrient foraging function in ECM symbionts.In addtion,the ECM symbionts preferentially facilitated P uptake in A.faxoniana under both N and P limitations,and affect the N and P stoichiometry by drving P element alteration in plant tissues.This research indicated that ECM functional traits with high plasticity could assist A.faxoniana to responding climate change to some degree and maintaining its survive and the current distribution;given that the trade-offs between the formation and differentiation of ECM symbionts and nutrient uptake of root and leaf in A.faxoniana,the symbiosis should be focused to make sure the responding ability of A.faxoniana under worsening environments and climate changes.