天山森林植物功能性状与碳库沿海拔梯度的变化

The variations in plant functional traits and forest carbon content with altitudinal gradients in the Tianshan Mountains

植物功能性状是能够将植物个体特征、群落结构和生态系统功能结合起来的良好载体,但关于在环境梯度上如何通过植物功能性状的连续变化来构建群落、以及植物功能性状如何反映生态系统功能等问题尚有较多疑问。为探讨天山森林植物功能性状与其碳库在海拔梯度上的联系,分析了14个群落尺度上的植物功能性状指标和各组分碳密度沿海拔的变化规律及二者之间的关系。结果表明:(1)受海拔梯度上环境因子的影响,群落尺度上植物功能性状和碳密度的垂直分布并不一致:随海拔升高,叶片碳氮比(C/N)逐渐上升,叶片碳含量(C_(leaf))、比根长(SRL)和植株高度(H)升高后降低,叶绿素含量(Chl)、细根磷含量(P_(root))、叶片氮磷比(N/P)逐渐下降,细根碳含量(C_(root))先升高后趋于平缓,细根氮含量(N_(root))先下降后又有所回升,叶片氮含量(N_(leaf))、木质素含量(LLC)、叶干物质含量(LDMC)、细根干物质含量(RDMC)在各海拔段间无显著差异;(2)比根长(SRL)和植株高度(H)通过影响资源的获取和利用,C与P通过对养分的限制和在器官中的分配,从而影响植被光合作用,与天山森林碳密度显著相关;高木质素含量(LLC)导致植物残体分解速率变慢而与土壤碳密度(SCD)和群落总碳密度(TCD)呈显著负相关关系。随海拔升高,植被碳密度(VCD)先升后降,土壤碳密度(SCD)和总碳密度(TCD)逐渐升高。植物功能性状与环境因子和森林的结构功能相互作用、相互影响,三者之间的关系还需在大尺度上进一步验证。

Plant functional traits are important characteristics for understanding the relationship between individual, community, and ecosystem functions. In the present study, we established 43 sample sets to examine 12 types of plant functional traits and corresponding carbon density information at the community scale. The objective of this work was to determine the internal relationship between the adaptive variation in functional traits and the carbon density of forest communities along an elevation gradient. The results show that at a higher altitude, the carbon to nitrogen ratio （C/N） in leaves increased linearly, whereas carbon content （Cleaf）, specific root length （SRL）, and height （H） initially increased and then decreased. Chlorophyll content （Chl） and fine root phosphorus content （Proot） decreased with elevation and fine root carbon content （Croot） initially increased and then flattened out with altitude. Fine root nitrogen content （Nroot） initially decreased and then increased, whereas leaf nitrogen content （Nleaf）, lignin content （LLC）, and fine root dry matter content （RDMC） showed no significant difference with altitude. SRL, H, the content of C, P in leaf and root showed significant correlations with vegetation carbon density （VCD） and soil carbon density （SCD） in the Tianshan forest, as they have influential effects on the photosynthesis of vegetation, in which SRL and H could affect plants resource acquisition and utilization, whereas C and P would limit nutrient availability. There was a negative correlation between LLC and SCD in the Tianshan forest, as LLC would limit the decomposition rate of plant residue. VCD initially increased and then decreased, whereas SCD and total carbon density （TCD） increased gradually with altitude. Plant functional traits interact with environmental factors and forest structure functions at multi-ecological levels, and the relationship between the three components needs to be validated on a large scale.