Carbon,Nitrogen And Phosphorus Stoichiometry In Leaf-Litter-Soil Of Pinus Sylvestris Var.mongolica In Sandy Land

Carbon(C),nitrogen(N)and phosphorus(P)are essential nutrient elements in plant and play an important role in forest succession,production and sustainable management of forest ecosystems.Pinus sylvestris var.mongolica is one of the main afforestation trees for wind and sand fixation in the northern desertified China,and plays an important role in ecological environment construction.We selected three different stand ages(middle-aged,near-mature and mature)P.sylvestris in the Hulunbuir,Horqin and Mu Us sandy land as objects.According to the principle of ecological stoichiometry,using the method of combination field survey sampling with lab experiment,analyzed the concentrations of C,N,P and ratios of C:N,C:P,N:P in leaf,litter and soil.The aim was to investigate the effects of area and stand age on the C,N,P stoichiometric characteristics of leaf,litter and soil in P.sylvestris in order to clarify the distribution rules and correlations of C,N and P in leaf-litter-soil system and provide a theoretical basis for the management of P.sylvestris plantations.The main research results are as follows:(1)The P.sylvestris plantations showed a high C and low N and P nutrient distribution pattern in this study.With the increase of stand age,the C concentrations in leaf,litter and soil increased first and then decreased(near-mature forest>middle-aged forest>mature forest),while N and P concentrations increased gradually(mature forest>near-mature forest>middle-aged forest).The C:N and C:P ratios in leaf,litter and soil were the lowest in mature forest,the leaf N:P ratio was highest in mature forest,the litter N:P ratio was the highest in middle forest,but there is no consistent rule of soil N:P ratio.(2)The C,N,P concentrations and C:N,C:P,N:P ratios were significantly different among leaf,litter and soil,but they all in the order of leaf>litter>soil.The study area had significant influence on C,N and P stoichiometric characteristics;stand age had no significant effect on leaf C concentration and N:P ratios in leaf,litter and soil;the interaction between area and stand age had less effect on C,N and P stoichiometric characteristics in leaf and litter,but the interaction had significant effect on soil stoichiometric characteristics,expect N:P ratio.(3)There was a coupling relationship between C,N and P in leaf of P.sylvestris plantation.The C,N,P concentrations and C:N,C:P,N:P ratios are closely correlated among leaf,litter and soil,indicating that C,N and P elements are transported and transferred between leaf-litter-soil of P.sylvestris plantation in sandy land,and the three components affect and restrict each other.(4)The leaf N:P ratio in Hulunbuir and Horqin sandy land ranged from 14.53 to 15.57,which indicated that the growth of P.sylvestris in these two areas might be co-restricted by N and P.The leaf N:P ratio in Mu Us sandy land ranged from 18.56 to 19.71,indicating that P limitation,and the effect of stand age on N and P nutrient limitation was not significant.In order to improve the productivity of P.sylvestris plantation in sandy land,it is suggested that N or P fertilizers should be added appropriately according to the local actual situation in tending and management of P.sylvestris plantation.