Stoichiometric Characteristics Of Different Aged Pinus Sylvestris Var. Mongolica Plantations

C,N,and P stoichiometric characteristics have become an important measure to study biogeochemical cycling and the balance of matter and energy in ecosystem.Pinus sylvestris var.mongolica is one of main conifer species of preventing wind and fixing sand,however,a serious growth decline has occurred.In order to understand the nutrient balance characteristics and restrictive factor of P.sylvestris var.mongolica forest ecosystem,we measured the contents of carbon,nitrogen and phosphorus in different organs,litter and soil of different aged(13a,23 a,32a,45 a,53a and 60a)P.sylvestris var.mongolica plantations.The main results were as follows:(1)With the increase of P.sylvestris var.mongolica age,C contents in needles and branches firstly increased and then decreased,while those in roots firstly decreased and then increased.N and P contents in needles increased,while those in branches and roots decreased.C:N in needles firstly increased and then decreased,while that in roots increased.C:P in needles and branches firstly decreased and then increased,while that in roots firstly increased and then decreased.The growth of Pinus sylvestris var.mongolica plantations was restricted by N element at 13 a,23a and32 a,whereas restricted by N and P at 45 a,53a and 60 a.(2)With the increase of P.sylvestris var.mongolica age,C content increased and N content firstly increased and then decreased in litter,while P content firstly increased and then decreased and the largest value occurred at 23 a and 32 a.Litter C:N firstly increased and then decreased,while C:P and N:P firstly decreased and then increased.The N reabsorption rate of needles gradually increased,and the P reabsorption of needles was fluctuated.The reabsorption rate was significantly higher than that of P of P.sylvestris var.mongolica at all forest ages.(3)With the increase of P.sylvestris var.mongolica age,soil organic C content firstly decreased and then increased,while total N firstly increased and then decreased and total P firstly decreased and then increased.Alkali hydrolyzed N and available P firstly decreased and then increased.Soil C:N and C:P firstly decreased and then increased,while N:P firstly increased and then decreased.