温带针阔混交林叶片性状随树冠垂直高度的变化规律

自然界中,森林植物叶片的生长随树冠高度呈现明显的垂直分布现象;然而,有关叶片性状随着树冠垂直高度增加的变化规律仍不清楚。为了更好地揭示植物叶片对光环境变化的适应策略以及对资源的利用能力,有必要深入探讨叶片性状与冠层高度的定量关系及其内在调控机制。以中国广泛分布的温带针阔混交林为对象,选取8种主要树种为研究对象(白桦、蒙古栎、水曲柳、大青杨、色木槭、千金榆、核桃楸和红松),通过测定这些物种9个冠层高度的叶片比叶面积(SLA)、叶片干物质含量(LDMC)、叶片氮含量(N)、叶片磷含量(P)、氮磷比(N∶P)和叶绿素含量(Chl)等属性,探讨了针阔混交林叶片性状的差异以及各性状之间的相关关系,进而揭示叶片性状随树冠垂直高度的变化规律。实验结果表明:1)温带针阔混交林内优势树种的部分叶片性状在不同冠层高度之间差异显著。2)随着树冠垂直高度的增加,SLA、LDMC、N、P、N∶P和Chl呈现不同的变化趋势。其中,阔叶树种SLA随着树冠垂直高度的增加而减小;所有树种的LDMC随着树冠垂直高度的增加而增加;不同树种的N、P、N∶P和Chl随着树冠垂直高度的变化规律存在差异。3)对于温带针阔混交林冠层中,SLA与N、P、N∶P均存在显著的正相关关系,高SLA伴随着高的N、P、N∶P,表明植物通过SLA与N、P等性状的协同来提高叶片的光合作用(或对光热资源的利用效率)。本研究通过定量分析探讨温带针阔混交林叶片性状随冠层高度的变化规律,一定程度地揭示了树木对光、热和水资源竞争的适应机制,以及植物叶片的资源利用和分配策略,不仅拓展了传统性状研究的范畴,其相关研究结论也有助于树木生长模型的构建和优化。

Vertical variation of leaf functional traits in temperate forest canopies in China

Vertical distribution of leaf functional traits is common in natural forest communities. However, how leaf functional traits vary with the vertical canopy height is still unclear. Here, we selected eight common tree species (Pinus koraiensis Sieb. et Zucc, Fraxinus mandschurica Rupr, Juglans mandshurica Maxim, Acer mono Maxim, Quercus mongolica Fisch.ex Ledeb, Carpinus cordata Bl, Betula platyphylla Suk, and Carpinus cordata Bl) from temperate needle and broadleaf mixed forests in Northeast China, and measured six conventional leaf functional traits (specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (N), leaf phosphorus content (P), N:P ratio (N:P), and chlorophyll content (Chl)) under nine different canopy heights, to explore the variation of leaf traits with vertical canopy height of the canopy and its underlying mechanisms. Our results showed that:1) leaf functional traits of the tree species were significantly different among the different canopy heights; 2) SLA, LDMC, N, P, N:P, and Chl showed different trends with increasing vertical canopy height. SLA of broad-leaved species decreased, whereas LDMC of all tree species increased as the vertical canopy height increased. Moreover, N, P, N:P, and Chl of different tree species varied with increasing vertical canopy height; 3) there were significant positive correlations between SLA and N, P, N:P, suggesting that higher SLA with higher N, P, and N:P could optimize leaf photosynthesis in the canopy. This study explored the vertical variation of leaf functional traits along canopy height in natural forests and expanded the scope of research on traditional traits. Furthermore, our findings could optimize ecological modeling in the future, to detect canopy height more effectively through the use of remote sensing or radar.