[论文解读] Tropical rainforest bird community structure in relation to altitude, tree species composition, and null models in the Western Ghats, India

T. R. Shankar Raman, N. V. Joshi+1 more|ArXiv.org|Oct 17, 2005

Ecology and Vegetation Dynamics Studies参考文献 37被引用 10

一句话总结

本研究调查了印度西高止山脉热带雨林中海拔梯度（500–1400 米）上鸟类群落结构，利用零模型和植被数据评估物种丰富度、群落组成及分布的决定因素。出乎意料的是，鸟类物种丰富度随海拔保持稳定，而群落组成则发生显著变化；海拔范围大小呈现倒 U 型模式，群落装配受与海拔和树种组成相关的确定性因素驱动。

ABSTRACT

Studies of species distributions on elevational gradients are essential to understand principles of community organisation as well as to conserve species in montane regions. This study examined the patterns of species richness, abundance, composition, range sizes, and distribution of rainforest birds at 14 sites along an elevational gradient (500-1400 m) in the Kalakad-Mundanthurai Tiger Reserve (KMTR) of the Western Ghats, India. In contrast to theoretical expectation, resident bird species richness did not change significantly with elevation although the species composition changed substantially (<10% similarity) between the lowest and highest elevation sites. Constancy in species richness was possibly due to relative constancy in productivity and lack of elevational trends in vegetation structure. Elevational range size of birds, expected to increase with elevation according to Rapoport's rule, was found to show a contrasting inverse U-shaped pattern because species with narrow elevational distributions, including endemics, occurred at both ends of the gradient (below 800 m and above 1,200 m). Bird species composition also did not vary randomly along the gradient as assessed using a hierarchy of null models of community assembly, from completely unconstrained models to ones with species richness and range-size distribution restrictions. Instead, bird community composition was significantly correlated with elevation and tree species composition of sites, indicating the influence of deterministic factors on bird community structure. Conservation of low- and high-elevation areas and maintenance of tree species composition against habitat alteration are important for bird conservation in the southern Western Ghats rainforests.

研究动机与目标

• 了解鸟类群落结构在热带雨林海拔梯度上的变化规律。
• 检验物种丰富度和分布模式是否符合理论预期，如拉波波特法则。
• 评估确定性因素（海拔、树种组成）与随机过程在群落装配中的作用。
• 评估群落结构对西高止山脉低海拔和高海拔栖息地保护意义的影响。
• 应用分层零模型，以确定观测到的鸟类群落模式是否偏离随机期望。

提出的方法

• 在卡拉卡德-芒达努拉老虎保护区的14个站点（海拔500–1400 米）开展野外调查。
• 在所有站点使用点样法记录鸟类物种的出现与多度。
• 在每个站点收集树种组成和植被结构数据，以评估栖息地相关因素。
• 应用一系列分层零模型——从无约束到限制丰富度和范围大小的模型——以检验群落装配是否非随机。
• 使用多重变量分析，将鸟类群落组成与海拔和树种组成相关联。
• 分析海拔范围大小分布，以检验拉波波特法则的预测。

实验结果

研究问题

• RQ1 在西高止山脉的海拔梯度上，鸟类物种丰富度是否随海拔显著变化？
• RQ2 鸟类群落组成如何沿海拔梯度变化，且这种变化在多大程度上是非随机的？
• RQ3 鸟类物种的海拔范围大小是否遵循随海拔升高而增大的预测模式（即拉波波特法则）？
• RQ4 鸟类群落结构在多大程度上由确定性因素（如海拔和树种组成）决定？
• RQ5 观测到的鸟类群落组成模式是否显著偏离随机装配的零模型预期？

主要发现

• 在500–1400 米的海拔梯度上，鸟类物种丰富度保持相对稳定，未观察到显著趋势。
• 最低海拔（500 米）和最高海拔（1400 米）站点之间的鸟类群落组成相似度极低（<10%），表明存在强烈的物种种间更替。
• 鸟类物种的海拔范围大小呈现倒 U 型模式，范围狭窄的物种主要集中在低海拔（低于800 米）和高海拔（高于1200 米）区域。
• 零模型分析显示，观测到的鸟类群落组成显著非随机，且与海拔和树种组成强相关。
• 研究未支持随机装配；相反，确定性过程，特别是与栖息地结构和海拔相关的因素，塑造了鸟类群落。
• 保护低海拔和高海拔区域至关重要，尤其是为维持具有狭窄海拔范围的特有种。