群落系统发育结构和植物功能多样性对云南常绿阔叶林叶凋落物分解的影响

The relationship between biodiversity and ecosystem functioning has emerged as a central issue in contemporary community ecology research. However, most studies focus on the relationship between biodiversity and ecosystem productivity, and the influence of biodiversity on leaf litter decomposition has not been well addressed. By selecting 49 dominant tree species from the canopy and sub-canopy of evergreen broad-leaved forests in the Ailao Mountains of Yunnan Province, we will measure the mass loss and nutrient release rate of the leaf litter, both for single tree species and their mixtures. By doing so, we will further explore the dynamic pattern of leaf litter decomposition in evergreen broad-leaved forests in Yunnan Province, examine the variations in leaf litter decomposition in four types of evergreen broad-leaved forests, and compare the decomposition differences during the rainy season and dry season. We will study the prevalence of non-additive mixture effects, and the explanatory power of green leaves' functional traits on leaf litter's decomposition rate. Moreover, we will detect the phylogenetic signal of the functional traits related to leaf litter decomposition on the basis of the construction of phylogenetic trees. Several fundamental hypotheses of biodiversity and ecosystem functioning research will be tested by applying a quantitative assessment of the influence of plant functional diversity, community weighted mean trait values and phylogenetic diversity on the decomposition process of litter mixtures. This research can improve understanding of the consequence of biodiversity loss in the background of global change, and provide necessary information for the protection of evergreen broad-leaved forests in Yunnan Province.

生物多样性与生态系统功能是当前国际生态学研究的热点议题，但大多集中在生物多样性与生态系统生产力的关系上，生物多样性对植物叶凋落物分解的影响尚未得到足够的关注。本研究以云南哀牢山常绿阔叶林49个林冠层和亚冠层的优势树种为研究对象，通过测定单一树种及混合叶凋落物的质量损失及养分释放速率，探索云南常绿阔叶林叶凋落物分解的动态格局，比较四种常绿阔叶林以及雨季和旱季叶凋落物分解速率的差异，检验非加和效应的普遍性以及绿色叶片的功能性状对叶凋落物分解速率的预测能力。在建立系统发育树的基础上，本研究还将检测与叶凋落物分解速率相关的功能性状（包括叶凋落物分解速率本身）的系统发育信号。定量评估功能多样性、群落加权的功能性状值、系统发育多样性对混合叶凋落物分解过程的影响大小，验证生物多样性与生态系统功能研究中的相关假说。本研究能为全球变化背景下的生物多样性丧失带来的影响以及云南常绿阔叶林的保育提供参考依据。

自然生态系统中地表凋落物通常以混合物的形式分解，凋落物的功能属性多样性会影响质量损失和养分释放的速率。本研究以哀牢山自然分布的常绿阔叶林为研究对象，测定单一树种和混合叶凋落物在雨季和旱季的分解速率和养分释放动态；测定树种的绿色叶片功能性状和叶凋落物初始状态下的功能属性；采用 DNA条形码技术，对目标树种的叶绿体基因片段和核基因片段进行测序，构建哀牢山常绿阔叶林群落和中山湿性常绿阔叶的系统发育树；从而探讨混合叶凋落物的质量损失和养分释放的多样性效应。结果表明，混合叶凋落物的质量损失大于单种叶凋落物的质量损失，但仅呈现出边际显著水平。混合叶凋落物的质量损失与功能离散度指数及氮平均值呈显著正相关，与木质素、纤维素平均值分别呈显著和极显著负相关。混合叶凋落物氮释放与功能丰富度、二次熵、分散度指数、氮平均值、磷平均值、钾平均值呈显著或极显著正相关，与木质素和纤维素平均值呈极显著负相关。混合叶凋落物磷释放与功能分散度、二次熵指数、氮平均值、磷平均值、钾平均值呈显著或极显著正相关，与木质素和纤维素平均值呈极显著负相关。我们的研究表明在中山湿性常绿阔叶林中，生态位互补假说和质量比假说对解释混合叶凋落物的质量损失和养分释放的多样性效应都具有重要的影响。本研究能为全球变化背景下的常绿阔叶林生物多样性与叶凋落物分解研究提供依据。