Carbon,nitrogen,and Phosphorus Stoichiometry And Non-structural Carbohydrate In Different Stand Ages In Wild Taxus Wallichiana Var.mairei

Taxus wallichiana var.mairei,a national grade I rare and endangered species,is an evergreen coniferous tree in the family of Redbudaceae,with ornamental,medicinal and edible values.It is named for its bright red and brilliantly colored fruits,which are quite like red beans.Taxus wallichiana var.mairei is dioecious,wind-pollinated,and suitable for warm and humid climates and well-drained fertile soils.The species has strict habitat requirements in the wild,and the natural renewal capacity of the population is slow,with almost no seedlings in the understory and slow growth,and the population is on the decline.Taxus wallichiana var.mairei contains important biological compounds such as paclitaxel,which has better effects in the treatment of ovarian cancer,breast cancer,lung cancer and many other diseases.The wild Taxus wallichiana var.mairei has been seriously damaged and cut down.Therefore,the germplasm resources of Taxus wallichiana var.mairei need urgent protection and sustainable management.Ecostoichiometric characteristics reflect the balance between elements such as C,N,and P required by organisms and ecosystem energy,while non-structural carbohydrates reflect the balance between carbon sources and sinks in plants.At present,there are relatively few studies on the ecological chemometric characteristics of carbon,nitrogen and phosphorus and non-structural carbohydrates in Taxus wallichiana var.mairei.Using ecological chemometrics to understand the intrinsic nutrient regulators of Taxus wallichiana var.mairei plant-soil is beneficial to reveal the interaction and constraints among carbon,nitrogen,and phosphorus elements,and to elucidate the storage of nonstructural carbohydrates and their deployment in Taxus wallichiana var.mairei at different stand ages.In this paper,the Taxus wallichiana var.mairei of three forest ages were taked as the research object stand age of I(4 cm≤DBH< 12 cm),stand age of II(12 cm≤DBH<20 cm),and stand age of III(20 cm≤DBH<28 cm).The differences in soil total carbon,total nitrogen and total phosphorus contents and stoichiometric ratios of leaves,branches,and soils of Taxus wallichiana var.mairei were compared and analyzed.And the effects of forest age on the storage and distribution of non-structural carbohydrates in leaves and branches were elucidated.It can provide a scientific basis for the protection and ecological managementof Taxus wallichiana var.mairei germplasm resources.The results of the study were as follows:(1)The age of forest significantly affected soil C,N,and P content.As the forest age increased,soil C,N,and P content gradually increased.Soil C:N was less than 25,and soil C: P was less than 200,indicating that the decomposition of soil organic matter was not limited by soil N,and soil P was net mineralized.And the decomposition rate of organic matter decreased with the increase of forest age.(2)Age of stand significantly affected Taxus wallichiana var.mairei N and P content,as well as C:N and C:P.As the forest age increased,leaf C content first decreased and then increased,leaf N content gradually decreased,and leaf P content gradually increased.Branch C content first increased and then decreased,while branch N and P content significantly decreased.The N:P values of both leaf and branch were less than 14,indicating that the growth of leaf and branch were limited by soil N.As the forest age increased,the N limitation on leavf gradually decreased,while the N limitation on branches gradually increased.(3)Age of stand and organs had no significant effect on Taxus wallichiana var.mairei NSC content.Leaf soluble sugar content and soluble sugar to starch ratio decreased with increasing forest age,while leaf starch and NSC content in gradually increased.Branch soluble sugar,starch,NSC content,and soluble sugar to starch ratio gradually decreased.(4)The C,N,and P content and C:N,C:P,and N: P in leaf,branch,and soil were closely related.The N content of leaf and branch were significantly positively correlated,and both were highly correlated with soil C and N content.The C:N content of leaf and branch were highly significantly positively correlated,and both were highly significantly positively correlated with soil C,N,and P content.Branch P content was significantly negatively correlated with soil C,N,and P content.(5)There was no significant correlation between NSC content in leaf and branch.Branch NSC content was highly significantly positively correlated with leaf N content,and significantly correlated with leaf C:N,N:P,as well as branch N,P content,C:N,C:P,N:P,and significantly negatively correlated with soil P content.The physical and chemical properties such as soil moisture content and soil p H had little effect on leaf and branch NSC content and its components.