Dissertation Research: Functional trait diversity and community assembly of trees and seedlings during tropical forest succession

在砍伐木材或农业之后，森林通常会自然再生。 当它们重新生长时，通常会有一系列不同的物种随着时间的推移而大量上升和下降，有时会以一个由砍伐前森林中相同物种的树木主导的森林结束。 然而，一些热带森林似乎没有以这种方式恢复：即使经过多年的自然再生，它们也没有恢复到成熟森林中的物种组成。 这个项目将测试什么可能阻止热带森林在砍伐后的恢复。 研究将集中在两个可能的因素，一些物种无法将种子传播到再生区域，以及具有某些特征的幼苗无法在清除后的条件下存活和成熟。 该项目将测量再生林（称为次生林）和成熟林中主要物种的主要特征，然后利用对哥斯达黎加六个次生林和两个成熟林13年来进行的树木年度普查，观察不同类型森林中的不同特征。 田间试验将直接比较牧草、次生林和成熟林中幼苗的存活和生长情况。除了帮助回答关于物种的功能如何决定森林在干扰后的恢复能力的基本科学问题外，该项目旨在改善热带地区的森林恢复。 这项研究将显示再生森林中缺少哪些类型的物种，并测试种植这些物种是否可以加速再生。 研究结果将广泛传播，有关物种特征的数据将纳入全球数据库。 此外，该项目将雇用和培训当地哥斯达黎加助理和来自美国的本科生，并与辅导计划合作。

After cutting for timber or agriculture, forests often regrow naturally. As they regrow, there is typically a succession of different species that rise and fall in abundance over time, sometimes ending with a forest dominated by the same species of trees that were in the forest before cutting. However, some tropical forests seem not to recover this way: even after many years of natural regeneration, they fail to return to the same composition of species that would be found in a mature forest. This project will test what may prevent the recovery of tropical forests after clearing. Research will focus on two possible factors, the inability of some species to spread their seeds into the regrowing areas, and the inability of seedlings with certain traits to survive and mature under the conditions left after clearing. The project will measure the key traits of the dominant species in regrowing forests, termed secondary forests, and mature forests, and then observe how different traits may be favored in the different types of forest using annual censuses of trees made over 13 years in six secondary and two mature forests in Costa Rica. A field experiment will directly compare the survival and growth of seedlings with contrasting traits in pasture, secondary forest, and mature forest. Besides helping to answer basic scientific questions about how the functional capabilities of species determine the ability of forests to recover after disturbance, this project is designed to improve forest restoration in the tropics. The research will show what types of species are missing from regenerating forests and test if planting these species can speed regeneration. Results will be widely communicated, and data on species traits will be incorporated into global databases. In addition, the project will employ and train both local Costa Rican assistants and undergraduate students from the U.S., and work with mentoring programs.