Carbon,Nitrogen And Phosphorus Stoichiometry Of Main Protective Forests In Horqin Sandy Land

Carbon(C),nitrogen(N),phosphorus(P)stoichiometry studies the balance of energy and multiple chemical elements in ecological process,providing a new way to solve the problem of ecosystem nutrient cycling.In order to provide theoretical basis for protective forests construction in Horqin sandy land,five protective forests(Pinus sylvestris var.mongolica,Pinus densiflora,Pinus tabulaeformis,Ulmus pumila and Populus simonii)were seclected,C,N and P contents in plant organs,withered leaves and soil were analyzed,the seasonal dynamics of C,N and P stoichiometry characteristics and distribution rules and nutrient balance characteristics of different tree species forests were compared.The results showed that compared with the national average,the C content was higher,while N and P contents were lower in leaves of five protective forests in Horqin sandy land.C content in leaves of P.sylvestris var.mongolica,P.densiflora and P.tabulaeformis was higher than those of U.pumila and P.simonii.C/N in leaves and branches followed the order of P.simonii > P.tabulaeformis > P.sylvestris var.mongolica and P.densiflora > U.pumila,and C/P followed the order of P.tabulaeformis > P.sylvestris var.mongolica > P.densiflora and U.pumila > P.simonii.Judged from N/P in leaves,N was the main limited element for growth of P.sylvestris var.mongolica,P.densiflora and P.simonii,the growth of P.tabulaeformis was restricted by N and P elements,and P was the main limited element for growth of U.pumila.N content in withered leaves of P.sylvestris var.mongolica and P.tabulaeformis was higher than that of P.densiflora and P.simonii,and P content in withered leaves followed the order of P.densiflora > P.sylvestris var.mongolica and P.tabulaeformis > U.pumila.The N reabsorption rate followed the order of P.densiflora and U.pumila > P.sylvestris var.mongolica and P.tabulaeformis > P.simonii,and P reabsorption rate of U.pumila and P.simonii was higher than that of P.sylvestris var.mongolica,P.densiflora and P.tabulaeformis.The soil C,N and P contents in 0~60 cm layers of five protective forests were lower than the national level.The soil organic C,total N,available N contents,C/P and total N/P of U.pumila were higher than those of other species;while soil organic C,total N,available N contents and C/P of P.tabulaeformis were lower than those of other species,and soil available P content and C/N were higher than those of other species.Conclusively,among five protective forests,P.sylvestris var.mongolica improved the utilization efficiency of N and Pelements to alleviate N limitation.The soil C/N decreased to accelerate N mineralization and improve soil N availability of P.densiflora.P.tabulaeformis coordinated the distribution of N and P between organs,and promoted the release of N elements from withered leaves.U.pumila increased utilization and reabsorption rate of P element to alleviate P limitation.P.simonii transferred N elements in different organs of leaves,branches and roots to improve N utilization.N fertilizer should be applied to P.sylvestris var.mongolica,P.densiflora and P.tabulaeformis in the early growth stage.P fertilizer should be applied to P.tabulaeformis and U.pumila,meanwhile,N fertilizer should be applied to P.simonii in the later growth stage.