LCZO -- Vegetation, Soil Gas, Soil Moisture -- Canopy Trimming Experiment -- Quebrada Prieta, El Verde -- (2003-2016)

General description of Experiment and Projects: Hurricanes are important drivers of periodic disturbances on tropical forests of the Luquillo Mountauns. The immediate impact of this disturbance is on the canopy biomass which is redistributed from the canopy compartments to the detrital pool of the forest floor hence creating a wide opened canopy. The Canopy Trimming Experiment (CTE) is a long-term experiment designed for two purposes: 1) to decouple the effect of canopy disturbance (e.g., increasing light levels, temperature, moisture, etc.) from those of increased detrital inputs on rates of germination, growth, survival, detritus processing, nutrient cycling, soil conditions, and trophic structure, and 2) to increase the frequency of simulated hurricane effects above background levels to once every six to ten years. Climate change models predict increased frequency and intensity of Caribbean hurricanes (Emmanuel 1987, Goldenberg et al. 2001), and the goal is to evaluate predictions regarding the effects of an increased rate of hurricane disturbance on tabonuco forest (Sanford et al. 1991). The interaction of biotic and abiotic processes, all modified by the disturbance, are key in determining ecosystem responses because they regulate critical ecosystem fluxes and storage associated with detritus decomposition. These processes define detrital dynamics and play a central role in the recovery of forest structure and function after disturbance. Therefore, a third component of this experiment was to implement a series of short-term biotic manipulations nested within the large-scale CTE design, consisting on faunal manipulations to measure the strength of interactions between autotrophic and detrital food webs in the context of hurricane-associated disturbance, which allowed to asses the important components of the foodwebs. The overall hypothesis is as follow: Short-term dynamics of key response variables after disturbance will be a function of the interaction between microclimate and detrital inputs, whereas long-term dynamics (particularly of SOM and NPP) will be a function of detrital inputs.

实验与项目总体概述：飓风是卢奎略山脉（Luquillo Mountains）热带森林周期性扰动的重要驱动因素。此类扰动的直接影响作用于冠层生物量，冠层生物量会从冠层组分重新分配至林地表层的碎屑库，进而形成大面积开阔的林冠空隙。冠层修剪实验（Canopy Trimming Experiment, CTE）是一项长期实验，旨在实现两大目标：其一，将冠层扰动（如光照水平、温度、湿度等升高）的效应，与碎屑输入增加对种子萌发、植株生长、个体存活、碎屑分解、养分循环、土壤状况以及营养结构的影响解耦；其二，将模拟飓风扰动的频率从背景水平提升至每6至10年一次。气候变化模型预测加勒比海飓风的发生频率与强度均会上升（Emmanuel 1987；Goldenberg et al. 2001），本研究旨在评估飓风扰动频率增加对塔博努科森林（tabonuco forest）的影响相关预测（Sanford et al. 1991）。所有受扰动调控的生物与非生物过程之间的相互作用，是决定生态系统响应的关键，因为这些过程调控着与碎屑分解相关的关键生态系统通量与储存量。这些过程决定了碎屑动态，并在扰动后森林结构与功能的恢复中发挥核心作用。因此，本实验增设第三项研究内容：在大规模CTE实验设计中嵌套开展一系列短期生物调控实验，通过动物类群调控实验，量化飓风扰动背景下自养食物网与碎屑食物网之间的相互作用强度，以此解析食物网的关键组成部分。本研究的总体假说如下：扰动后关键响应变量的短期动态，将是微气候与碎屑输入相互作用的函数；而长期动态（尤其是土壤有机质（Soil Organic Matter, SOM）与净初级生产力（Net Primary Productivity, NPP）的动态）则仅由碎屑输入决定。