Understanding the key mechanisms of tropical forest responses to canopy loss and biomass deposition from experimental hurricane effects
Understanding the key mechanisms of tropical forest responses to canopy loss and biomass deposition from experimental hurricane effects
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DOI：
10.1016/j.foreco.2014.04.024
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发表时间：
2014-11
影响因子：
3.7
通讯作者：
A. Shiels;G. González
中科院分区：
文献类型：
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作者：
A. Shiels;G. González
迄今为止，尚不清楚哪些因素对飓风后热带森林的恢复影响最大。树冠开放度的增加和碎屑（碎片）沉积的增加是两个最可能的因素，但由于它们在飓风期间同时发生，因此如果不进行操作实验就无法区分它们的相对影响。因此，在波多黎各的卢科伊洛实验森林 (LEF)，卢科伊洛长期生态研究计划 (LTER) 在复制的 30 × 30 m 样地中进行了实验操作，以模拟飓风扰动的主要影响——树冠开放度增加和森林地面碎片增加。使用析因实验能够调查树冠开放和碎片对这片潮湿的热带森林的单独和综合影响；实验结果可能有助于指导类似的易受干扰环境中的森林管理决策。在本特刊的第一篇文章中，我们 (1) 提供了该操作性实验（树冠修剪实验，CTE）的设计和方法的详细信息，(2) 报告了对治疗的一些主要非生物反应，以及 (3) 介绍了本特刊中另外 12 篇 CTE 手稿的主题领域。树冠和林下处理造成的物理条件以及添加到 CTE 地块的碎片量与 1989 年飓风雨果（4 级风暴）后 LEF 的条件相似；尽管 CTE 中存在更多木材和 37%（1.5 厘米）深的枯枝落叶层。我们选择性地砍伐和清除 3 m 以上的森林树冠，其中包括修剪 234 棵棕榈树和 342 棵非棕榈树，在 18 个月的时间里增加了光照水平并降低了凋落物湿度，极大地改变了林下微环境；修剪地块的降雨量和土壤湿度在 3 个月内有所升高。在修剪树冠并将碎片（6 kg m−2）添加到森林地面的地块中，树冠碎片在森林地面上持续了至少 4 年；在具有完整檐篷的地块中，碎片分解得更快。本期特刊中的各种论文集提供了对热带森林生物群（微生物、植物、动物）和过程（分解、食草、养分循环、初级生产）对类似于大型（⩾ 3 类）飓风的树冠和林下扰动的响应模式的机械理解。尽管该实验的测量正在进行中，以进一步确定飓风造成的长期森林变化的机制，但我们此时纳入了处理后头七年的发现。
To date, it is not clear which are the factors that most influence tropical forest recovery from hurricanes. Increased canopy openness and increased detritus (debris) deposition are two of the most likely factors, but due to their simultaneous occurrence during a hurricane, their relative effects cannot be separated without a manipulative experiment. Hence, in the Luquillo Experimental Forest (LEF) of Puerto Rico, the Luquillo Long-Term Ecological Research Program (LTER) has undertaken experimental manipulations in replicated 30 × 30 m plots to simulate the major effects of hurricane disturbance–increased canopy openness and debris addition to the forest floor. Using a factorial experiment enabled investigation of the separate and combined effects of canopy opening and debris on this wet tropical forest; the experimental outcomes may help direct forest management decisions in similar disturbance-prone environments. In this first article of the special issue, we (1) provide details of the design and methodology for this manipulative experiment (the Canopy Trimming Experiment, CTE), (2) report some principal abiotic responses to treatments, and (3) introduce the subject areas of the 12 additional CTE manuscripts in this special issue. The physical conditions created by canopy and understory treatment and the amounts of debris added to CTE plots were similar to the LEF’s conditions following Hurricane Hugo (a category 4 storm) in 1989; although more wood and a 37% (1.5 cm) deeper litter layer was present in the CTE. Our selective cutting and removal of the forest canopy above 3 m, which included trimming 234 palm trees and 342 non-palm trees, greatly altered the understory micro-environment by increasing light levels and decreasing litter moisture for 18 months; throughfall and soil moisture were elevated in trim plots for 3 months. In plots where the canopy was trimmed and the debris (6 kg m−2) was added to the forest floor, the canopy debris persisted on the forest floor for at least 4 years; debris decomposed more quickly in plots with intact canopies. The diverse collection of papers in this special issue provide mechanistic understandings of response patterns of tropical forest biota (microbes, plants, animals) and processes (decomposition, herbivory, nutrient cycling, primary production) to canopy and understory disturbance that resembles a major (⩾category 3) hurricane. Although measurements for this experiment are on-going to further identify the mechanisms of long-term forest change resulting from hurricanes, we include findings up to the first seven years post-treatment at this time.