油松人工林新生枝叶碳氮磷含量及化学计量比对氮添加的响应

Responses of C,N and P Contents and Their Stoichiometric Ratios of New Branches and Leaves in Pinus tabulaeformis Plantations to N addition

为探究氮(N)添加对油松(Pinus tabuliformis)人工林养分利用策略的影响及其随林龄的变化,以4个林龄油松人工林为对象,研究5个梯度(0、5、10、15和20 g/m^(2))N添加量对新生枝叶碳(C)、氮(N)和磷(P)含量及其化学计量比的影响,揭示油松人工林N利用策略及其对N添加的响应。结果显示,油松人工林新生枝叶的TC、TN和TP含量均随N添加量的增加呈先增加后减少的趋势,均在10或15 g/m^(2)添加量下最高;枝叶的TC、TN和TP含量在不同林龄间均存在差异,枝的变幅分别为7.53%、13.37%和18.67%,叶的变幅分别为7.74%、13.67%和29.61%。新生枝叶的C/N、C/P和N/P均随N添加量的变化小幅变化,平均变幅为3.99%~9.91%;随N添加量增加,枝叶的C/N和C/P均呈先降低后升高的趋势,N/P持续升高;随林龄增加,枝叶的C/N和C/P均呈先升高后降低的趋势,均在37年生时最大,枝的N/P持续升高,叶的N/P先升高后降低。油松人工林生长受N限制严重;随N添加量和林龄增加,N限制有所缓解。

In order to explore effect of nitrogen(N)addition on nutrient utilization strategy of Pinus tabulaeformis plantation and its change with stand age,effects of five gradients of N addition amount(0,5,10,15 and 20 g/m^(2))on carbon(C),N and phosphorus(P)contents and their stoichiometric ratios of new branches and leaves were studied in four P.tabulaeformis plantations at different ages,which could reveal N utilization strategy and response to N addition of P.tabulaeformis plantation.Results showed that with increase of N addition amount,contents of TC,TN and TP of new branches and leaves in P.tabulaeformis plantations showed trends of increase firstly and then decrease,and were the highest in amount of 10 or 15 g/m^(2).There were differences in TC,TN and TP contents of new branches and leaves among different stand ages.Variation ranges of branches were7.53%,13.37%and 18.67%,and those of leaves were 7.74%,13.67%and 29.61%,respectively.C/N,C/P and N/P of new branches and leaves in P.tabulaeformis plantations changed little with change of N addition amount,with average variation ranges of 3.99%-9.91%.With increase of N addition amount,C/N and C/P of branches and leaves decreased firstly and then increased,and N/P increased continuously.With increase of stand age,C/P and N/P increased firstly and then decreased,reaching the maximum in 37-year-old,N/P of branches increased,and N/P of leaves increased firstly and then decreased.Effect of N limitation on growth of P.tabulaeformis plantation was serious.With increase of N addition amount and stand age,N limitation was alleviated.