Collaborative Research: Causes and Consequences of Tree Colonization Patterns in Wet Tropical Forests

在世界上许多热带地区，森林在放弃农业或伐木后正在重新生长，但人们对这一过程知之甚少。这项为期三年的研究将考察树冠树木在哥斯达黎加大西洋低地最初为农业用途而被砍伐的潮湿热带森林中重新定居的过程。为了确定为什么某些物种在森林恢复过程中的不同时间到达和建立，调查人员将比较：“年轻”地点，最近形成了一个封闭的森林冠层（放弃后5-10年）；“中间”地点，具有良好的森林结构（废弃后19-32年）；而“成熟”的遗址则完好无损。将种植12种冠层树种的种子，以研究不同因素如何影响森林发展不同阶段的幼苗存活。这些因素包括获取以种子为食的动物，与现有幼苗的竞争，以及森林地面附近可用的光照量。此外，调查人员将在三种森林类型中建立和监测样地，然后每年对所有冠层树木进行普查和绘制。在数百个绘制的小地块中，所有树冠树种的幼苗都将被计数和标记。幼苗相对于同一树种成熟树位置的分散将在表现出不同再定殖模式的树种之间进行比较。为了评估光在森林恢复过程中的作用，研究人员将评估被监测幼苗的光照水平，并确定光照和与成虫的接近程度在解释幼苗分散模式中的相对重要性。在整个研究过程中，将在10个1公顷的地块上监测冠层物种的新到达、死亡、生长和大小分布。这项研究将有助于指导热带地区的森林恢复工作，并提供森林测绘、监测和数据分析方法方面的培训。

In many tropical regions world-wide, forests are regrowing after abandoned agriculture or logging, but this process is poorly understood. This three-year study will examine the process by which canopy trees recolonize abandoned sites in wet, tropical forests that were initially cleared for agricultural use in the Atlantic lowlands of Costa Rica. To determine why certain species arrive and establish at different times during the forest recovery process, the investigators will compare: "young" sites, which have recently developed a closed forest canopy (5-10 years after abandonment); "intermediate" sites, which have a well-developed forest structure (19-32 yrs after abandonment); and "mature" sites, which have remained intact. Seeds of 12 canopy tree species will be planted to examine how different factors affect seedling survival across different stages of forest development. These factors include access to seed-eating animals, competition with existing seedlings, and the amount of light available near the forest floor. In addition, the investigators will establish and monitor plots in the three forest types and then census and map all canopy trees each year. In hundreds of mapped smaller plots, all seedlings of canopy tree species will be counted and tagged. The dispersion of seedlings relative to the locations of mature trees of the same species will be compared among tree species that exhibit different patterns of recolonization. To evaluate the role of light in the forest recovery process, the investigators will assess light levels for monitored seedlings and determine the relative importance of light and proximity to fruiting adults in explaining seedling dispersion patterns. Throughout the study, new arrivals, deaths, growth, and size distributions of canopy species will be monitored in ten one-ha plots. This research will help to guide forest recovery efforts in tropical regions, and provide training in the methods of forest mapping, monitoring, and data analysis.