吉林蛟河针阔混交林功能性状分布格局及其对地形因素的响应

森林群落的构建过程及其内在机制是生态学研究的热点问题。植物功能性状是指能够代表植物的生活史策略，反映植物对环境变化响应的一系列植物属性。通过植物功能性状的分布格局及其对环境因素的响应有助于推测群落的构建过程及其内在作用机制。以吉林蛟河21.12hm²温带针阔混交林样地为研究对象，采集并测量了样地内34种木本植物的6种不同的功能性状。以20m×20m的样方为研究单元，通过计算平均成对性状距离指数（mean pairwise trait distance；PW）和平均最近邻体性状距离指数（mean nearest neighbor trait distance；NN）来探讨群落中单个性状和综合性状的分布格局。同时结合地形因子采用回归分析探讨功能性状的分布格局对局域生境变化的响应。基于PW的结果显示：单个性状中除叶面积外，其余性状的分布格局均为聚集分布多于离散分布；基于NN的结果显示：除叶面积和最大树高外，其余性状的分布格局为聚集分布多于离散分布。此外，由6种单个性状组成的综合性状的分布格局同样为聚集分布多于离散分布。基于回归分析的结果显示：森林群落中功能性状的分布格局受到海拔、坡度和坡向等因素的显著影响，而凹凸度的影响则不显著。研究结果表明包括环境过滤和生物相互作用的非随机过程能够影响温带针阔混交林的群落构建过程，中性过程对该区域群落构建过程的影响不显著。

Distribution pattern of functional traits and its response to topographic factors in a conifer and broad-leaved mixed forest in Jiaohe, Jilin province

Understanding the mechanism and process of community assembly is a key issue in ecological research. Functional traits, which represent plant physiological, morphological, and phenological attributes, have decisive effects on plant growth, survival, reproduction and dispersal. Examining the spatial distribution pattern of plant functional traits and its response to local environmental variation is helpful to speculate the underlying processes and mechanisms that regulate community assembly. In this study, we explored the underlying mechanisms of community assembly using the dataset from a 21.12hm² temperate conifer and broad-leaved mixed forest plot in Jiaohe, Northeast China. Four topographic attributes, including elevation, convexity, slope, and aspect, were measured as local environmental factors. Six functional traits, namely leaf area, specific leaf area, leaf carbon content, leaf nitrogen content, leaf carbon to nitrogen ratio, and maximum tree height, were collected and measured for all 34 woody species that present in this temperate forest plot. Two functional structure indices, including the mean pair-wise trait distance (PW) and the mean nearest neighbor trait distance (NN), were used to explore the spatial distribution pattern of plant traits. Furthermore, regression analyses were used to investigate the response of trait patterns to environmental variation. Based on the results of PW, we found that, except for the leaf area traits, the remaining traits mainly showed the clumped spatial patterns. The results based on NN showed that, except for the leaf area and maximum tree height, the remaining traits presented the clumped spatial patterns. The results of regression analyses showed that the distribution patterns of functional traits were significantly affected by elevation, slope, and aspect. In contrast, convexity had no significant effect on trait distribution in this temperate forest community. Our results indicate that the non-random processes including environmental filtering and biological interactions played important roles in regulating forest community assembly, while the role of neutral process was not significant in this temperate conifer and broad-leaved mixed forest.