Environmental Heterogeneity and Woody Species Diversity in Low-elevation Tropical Secondary Forests

低海拔热带次生林环境异质性与木本物种多样性

• 批准号: 9208031
• 负责人: Donald Stone
• 金额: $ 81.24万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-07-15 至 1997-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9208031&HistoricalAwards=false
• 关键词: Environmental; Heterogeneity; Woody; Species; Diversity

This study addresses basic ecological processes that influence the nature and diversity of tree regeneration during secondary forest succession in low-elevation tropical forest. It is hypothesized that seedling recruitment during succession is strongly dependent on both resource availability and heterogeneity. Specifically, it is suggested that changes in canopy and gap structure, as successional forests age, increase both light availability and light heterogeneity at ground level. It is expected that species richness of the regeneration pool is enhanced by both overall light availability and the diversity of light environments represented in older, structurally heterogeneous stands. Seedling recruitment is further enhanced by availability of patches of disturbed soil associated with gaps or animal activity. This interdisciplinary approach integrates ecosystem-level studies of the patterns of tropical forest succession with detailed analyses of within-stand processes producing those patterns and studies of physiological and growth responses of representative species. Changes in forest composition and structure with be documented in the species richness of seedlings, and in within-stand environmental heterogeneity in a chronosequence of secondary and old-growth premontane rain forests of northeastern Costa Rica. Detailed measurements of the spatial variation of light availability, soil disturbance, and litter cover in selected forests will be performed along this chronosequence. The influence of distance to seed sources on propagule diversity will be assessed in these stands by sampling soil seed stocks in the study sites and by comparing the diversity of seedlings and saplings as a function of distance from seed sources. Investigators will experimentally examine the effects of resource availability and heterogeneity on seedling establishment and growth by manipulating light availability and soil disturbance in a series of 15-25 year old stands. Light will be manipulated by creating large and small canopy gaps and removing understory shrubs in a replicated single-factor (4 treatments) design in which we will assess the effects on natural seedling recruitment and species richness. Additional manipulative studies in gaps and closed-canopy sites will examine the interactive effects of light and soil disturbance on natural seedling recruitment and the germination and survival of seeds of selected species. Experimental and observational field data will be used to model the effects of stand structure and light availability of seedling abundance and diversity using a spatial, mechanistic, simulation model of forest dynamics. To evaluate the role of species-specific differences in canopy light transmission within secondary forest, a comparative study of canopy structure and light transmission will be conducted for five abundant canopy tree species in the stands. The model will also simulate the effect of spatial heterogeneity on the diversity of seedling regeneration, based on measured ecophysiological and growth responses of selected species. Model inputs will be based on field data from representative stands within the chronosequence. This modelling effort will integrate measured organismal responses in the context of stand-level changes in resource availability in tropical forests. Project results will contribute to basic ecological research on the maintenance of biological diversity in moist tropical forests, with direct applicability to studies of tropical forest restoration, secondary forest management, and sustainable tropical forestry.

这项研究涉及影响生态系统的基本生态过程， 次生林更新的性质和多样性 低海拔热带森林的演替。 据推测 在演替过程中，幼苗的补充强烈依赖于 资源可用性和异构性。 具体来说就是 表明，冠层和林窗结构的变化，作为演替 森林年龄，增加光的可用性和光 地平面的不均匀性。 预计物种丰富度 整个再生池的亮度 可用性和光环境的多样性， 年龄较大，结构不均匀的林分。 苗木招聘是 通过扰动土壤斑块的可用性进一步增强 与间隙或动物活动有关。 这个跨学科 方法整合了生态系统层面的研究模式， 热带森林演替与林分内详细分析 产生这些模式的过程以及对生理和 代表性物种的生长反应。 森林组成和结构的变化， 幼苗的物种丰富度，以及林内环境 次生和古老生长年代序列的不均一性 哥斯达黎加东北部的山地雨林。 详细 测量光的可用性的空间变化，土壤 干扰，并在选定的森林凋落物覆盖将进行 沿着这个时间顺序。 距离种子的影响 繁殖体多样性的来源将在这些看台上进行评估， 对研究地点的土壤种子库进行取样， 幼苗和树苗的多样性作为距离的函数， 种子来源 研究人员将通过实验来检验 资源的可利用性和异质性对幼苗建立的影响 通过控制光照和土壤扰动来促进植物生长 在一系列15-25岁的看台上。 光将被操纵， 创造出大大小小的树冠间隙， 在重复的单因素（4个处理）设计中，我们将 评估对自然幼苗补充和物种的影响 富有 林隙和郁闭林冠中的附加操纵研究 这些地点将研究光线和土壤的相互影响， 干扰自然幼苗补充和萌发， 选择物种的种子。 实验和观测现场数据将用于模拟 林分结构和苗木光能利用率效应 丰富度和多样性， 森林动态模型 为了评估物种特异性的作用， 次生林树冠透光率的差异， 冠层结构和透光率的比较研究， 对林分中5种丰富的林冠树种进行了调查。 的 模型还将模拟空间异质性对 幼苗更新的多样性，根据测量 选择物种的生理生态和生长反应。 模型 输入将基于来自代表性林分的现场数据， 时间序列 这一建模工作将结合衡量 在林分水平变化的背景下， 热带森林资源的可利用性。 项目成果将 促进关于维持生态系统的基本生态研究， 潮湿热带森林的生物多样性， 对热带森林恢复研究的适用性，次级 森林管理和可持续热带林业。