Theory and application of medium-term successional dynamics in secondary tropical forest

人们越来越需要将热带地区大面积退化的生境恢复为森林，以保护生物多样性，减轻气候变化的影响(通过固碳)，减少表层土壤的侵蚀和流失，并提供人类生计，然而，人们对热带森林恢复战略在建立后的头几年有多好知之甚少。这项长期实验旨在解决有关热带森林恢复的两个关键问题。首先，这项研究将天然林恢复与两种不同的森林恢复方法(低强度和高强度方法)进行比较，以评估人类干预的程度如何影响热带森林恢复的速度。其次，这项研究评估了修复地点靠近残存林地的重要性，残存林地可以作为动植物殖民的来源。这项研究的结果将为土地管理人员和政策制定者提供关键的指导，指导他们如何最有效地投入有限的资源，以改善全球正在进行的数百万公顷热带森林恢复的成果。这项研究将为研究生和本科生提供培训，新的探究性学习计划将积极吸引高中生参与研究。十多年前，在哥斯达黎加南部100平方公里的面积上建立了13个试验点，每个试验点周围都有一系列森林覆盖。每个地点有三个实验处理：1.不植树和自然恢复；2.种植三种大小的树岛(低强度)；3.整个地块种植树木(高强度)。研究人员将收集有关指标的数据，以评估下一阶段的森林演替，包括测量土壤养分、当地小气候、种子传播、树木生长以及森林幼苗的建立和存活。此外，合作科学家将使用这些地块来研究森林恢复的其他方面，如昆虫群落动态，以及鸟类和蝙蝠的行为。这些数据将用于解决有关中期森林恢复以及恢复模式如何随时间变化的若干问题，其中包括：恢复干预措施对地点内和跨地点生物多样性的影响；对初始条件的处理在多大程度上导致与参照林的演替轨迹趋同或背离；以及地方和地貌尺度进程对森林恢复的相对重要性。

There is a growing need to restore extensive areas of degraded habitat in tropical areas to forest in order to conserve biodiversity, mitigate the impacts of climate change (through carbon sequestration), reduce erosion and loss of topsoil, and provide for human livelihoods, yet little is known about how well tropical forest restoration strategies work beyond the first few years of establishment. This long-term experiment aims to address two key questions about tropical forest recovery. First, the research compares natural forest recovery to two different forest restoration approaches (a low and high intensity approach) to assess how the degree of human intervention affects the rate of tropical forest recovery. Second, the study evaluates the importance of the proximity of restored sites to remnant forest patches, which can serve as a source for colonizing plants and animals. Results of this study will provide critical guidance to land managers and policy makers on how to most effectively invest limited resources to improve the outcomes of the millions of hectares of tropical forest restoration being undertaken globally. The study will provide training for graduate and undergraduate students, and new inquiry-based learning program will actively engage high school students in the research. Over a decade ago, 13 experimental sites were established over a 100 square kilometer area in southern Costa Rica, each site with a range of surrounding forest cover. Each site has three experimental treatments: 1. no tree planting and natural recovery; 2. planting tree islands of three sizes (low intensity); and 3. planting the entire plot with trees (high intensity). Researchers will collect data on metrics to assess the next phase of forest succession, including measuring soil nutrients, local microclimate, seed dispersal, tree growth, and the establishment and survival of forest seedlings. In addition, plots will be used by collaborating scientists to study other facets of forest recovery such as insect community dynamics, and bird and bat behavior. The data will be used to address several questions about mid-stage forest recovery and how the pattern of recovery can change over time including: the effect of restoration interventions on within- and across-site biodiversity; the degree to which manipulations of initial conditions result in convergent or divergent successional trajectories from reference forest; and the relative importance of local- versus landscape-scale processes on forest recovery.