华北落叶松不同器官碳氮磷化学计量特征

Ecological C,N and P stoichiometry of the needles,twigs and fine roots in pure and mixed stands of Larix principis-rupprechtii

为探究华北落叶松叶、枝、根各器官碳(C)、氮(N)、磷(P)含量及化学计量特征在不同林分类型中的变化规律,以塞罕坝地区华北落叶松一代林(17a和37a)、二代林(14a)、和落桦混交林(36a)为研究对象,采用方差和相关方法分析华北落叶松不同器官的C、N、P含量及化学计量特征。结果如下:(1)华北落叶松不同器官C含量变化范围为447.13~532.06g/kg,表现为细枝>针叶>细根;N含量变化范围为3.82~22.06g/kg,P含量为0.35~1.53g/kg,均表现为针叶>细根>细枝。(2)一般来讲,除了针叶C含量在不同林分类型间变化不显著外,细枝和细根C含量均在落桦混交林(36a)中最高;不同器官N含量在一代林(17a)中最低,而在一代林(37a)中最高;与细枝P含量变化相反,针叶P含量在一代林(37a)中最低。(3)同一代际中,一代林(37a)的不同器官C/N均低于一代林(17a);与不同器官的N/P变化相似,针叶和细根C/P在一代林(37a)中较高,而细枝C/P则在落桦混交林(36a)中最高。(4)C、N含量和各计量比(C/N、C/P和N/P)在不同器官间均极显著正相关(P<0.01),而P含量在不同器官间相关不明显(P>0.05)。不同林龄代际林和器官间C、N、P含量和化学计量比变化存在差异,通过华北落叶松针叶中化学计量特征的变化,阐明了研究区落桦混交林(36a)和一代林(37a)生长主要受P限制,而一代林(17a)生长主要受N限制。

In order to explore the variation of carbon(C),nitrogen(N)and phosphorus(P)and their stoichiometric ratios in leaves,twigs and fine roots of different Larix principis-rupprechtii stands.Four L.principis-rupprechtii stands:17 years aged first generation(Y1 R),37 years aged first generation(M1 R),14 years aged second generation(Y2 R),and 36 years aged larch-birch mixed forests(LBM)in Saihanba area were selected.Variance and correlation analysis were adopted to analyze the differences in C,N,P and stoichiometric characteristics of different organs among four L.principis-rupprechtii plantations.The results are as follows:(1)Nutrient contents in different organs ranged from 447.13 to 532.06 g/kg for C,3.82 to 22.06 g/kg for N,and 0.35~1.53 g/kg for P,respectively.The C content followed the order of twigs>leaves>fine roots,whereas the N and P contents followed the pattern of leaves>fine roots>twigs.(2)Generally,the largest C contents of twigs and fine roots were both found in LBM,while leaf′s C content showed no significant differences among stands.The maximal N contents in all organs were found in M1 R,and the smallest were found in Y1 R.In contrast to changes of P in twigs among stand types,the smallest P content in leaves was found in M1 R.(3)In the same generation,the C/N of different organs of the first generation forest(37 a)was lower than that of the first generation forest(17 a).Similar to changes of N/P in all organs among stand types,C/P ratios of leaves and fine roots were higher in M1 R,whereas C/P ratios of twigs was the highest in LBM.(4)There were very significant correlations of C,N contents and all ratios(C/N,C/P和N/P)among different organs(P<0.01).The C,N and P contents and their stoichiometry varied among larch generation stands with different ages and among organs.Based on the changes of C,N and P contents and their stoichiometry in leaves,our study suggests P limitation for 36-aged larch-birch mixed and 37 years aged first generation stands,whereas N limitation for 17-aged first generation stands.