DISSERTATION RESEARCH: Seedling Dynamics and Forest Diversity in Amazonian Ecuador

论文研究：厄瓜多尔亚马逊流域的幼苗动态和森林多样性

• 批准号: 0407956
• 负责人: Wayne Sousa
• 金额: $ 1.5万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0407956&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Seedling; Dynamics; Forest

The rainforest of Yasuni National Park, Ecuador, is among the most diverse on earth. Various mechanisms have been hypothesized to explain the local coexistence of such a large number of canopy tree species. Many of these proposed mechanisms invoke particular patterns of seedling recruitment, growth, and mortality that reduce the likelihood that dying canopy trees will be replaced by only one or a few dominant species. This dissertation research evaluates these hypotheses using a two-pronged approach. First, natural rates of recruitment, growth, and mortality of seedlings are being quantified in permanent census plots distributed throughout the study forest. These plots, established in 2002, are monitored annually. Second, based on these censuses, focal sets of common and rare species will be selected for use in field experiments. The spatial distributions and densities of seeds and seedlings of these species will be manipulated to directly test the hypotheses that diversity is maintained by 1) the restriction of different species' seedlings to particular soil types or microhabitats, 2) spatially limited dispersal of seeds; particularly by competitively dominant species, or 3) frequency-dependent or density-dependent mortality that prevents a dominant competitor from excluding relatively rare species. These experiments will determine whether species of differing abundances (i.e., relatively rare vs. relatively common) exhibit responses to experimental manipulation consistent each proposed mechanism of diversification. The study forest is more species-rich than sites of previous studies of rainforest diversity. Thus, the research will test the generality of conclusions drawn from other tropical forests. An added benefit of the project is that it involves active collaboration between Ecuadorian and North American scientists.

厄瓜多尔亚苏尼国家公园的雨林是地球上最多样化的雨林之一。为了解释如此大量的冠层树种在当地的共存，人们提出了各种各样的假说。这些提出的机制中有许多援引了幼苗招募、生长和死亡的特定模式，这些模式降低了垂死的冠层树木被一个或几个优势物种所取代的可能性。本论文研究采用双管齐下的方法评估这些假设。首先，在整个研究森林分布的永久普查样地，对幼苗的自然增收率、生长率和死亡率进行了量化。这些地块于2002年建立，每年进行监测。其次，在这些普查的基础上，将选择常见和稀有物种的焦点组用于野外实验。这些物种的种子和幼苗的空间分布和密度将被操纵，以直接验证以下假设：1)不同物种的幼苗被限制在特定的土壤类型或微生境中；2)空间上限制种子的传播；特别是竞争优势物种，或3)频率依赖或密度依赖的死亡率，以防止优势竞争对手排除相对稀有的物种。这些实验将确定不同丰度的物种（即相对罕见与相对常见）对实验操作的反应是否与每种提出的多样化机制一致。研究森林的物种比以前研究雨林多样性的地点更丰富。因此，这项研究将检验从其他热带森林得出的结论的普遍性。该项目的另一个好处是它涉及厄瓜多尔和北美科学家之间的积极合作。