LTER: Long-Term Ecological Research in the Luquillo Experimental Forest 3

Luquillo实验森林LTER项目（LUQ）专注于热带森林生态系统的长期动态，其特征是大规模、不频繁的干扰、有机物质的快速加工、高栖息地和物种多样性。LUQ的研究激发了对热带森林生态系统大规模扰动的重要性和生物群在形成对这些事件的响应中的关键作用的新认识。飓风发生在LTER项目开始后的1年和10年，这使得科学家们能够利用景观规模的自然实验，这些实验被密切关注。这些自然实验中最重要的发现之一是，碎屑动力学通过影响碳和养分的储存和流动，在森林恢复中起着核心作用。提出的中心主题是干扰，通过其对碎屑动力学的影响，是LUQ的主要生态系统驱动因素。碎屑的脉动改变了食物网内的能量流动，改变了营养物质的可用性和分布，并反馈了动植物群落的组成和生产力。快速处理的碎屑使LUQ与其他有森林的LTER站点区别开来，后者分解需要2-20倍的时间。通过长期测量、野外实验、模拟建模和跨站点比较，提出了以下五个问题：(1)气候因子、凋落物质量和碎屑生物多样性如何调节碎屑脉冲的分解？(2)陆地和水生食物网对碎屑脉冲的响应有何不同？(3)干扰频率对养分循环、植物群落组成和土壤有机质积累有何影响？(4)流域碳和养分的输出在多大程度上是受碎屑动力学影响的土壤特性的结果？(5)海拔相关的气候变化如何影响植物和腐殖生物群落，以及这些变化如何反馈凋落物输入和分解的数量和质量？本研究将在两个空间背景下进行。在中海拔tabonuco森林中，LUQ将继续对生态系统对飓风、滑坡和人为干扰的反应进行长期测量。将启动一项模拟飓风频率增加的实验，以调查增加的碎屑输入对营养循环、群落组成和有机质积累的影响。操纵关键的无脊椎动物群体，以更好地了解水生和陆地食物网之间碎屑处理的相似性。将建立新的样地来研究海拔相关的气候、植物群落和分解者对碎屑处理的影响。操作实验将比较非生物和生物控制对陆地和水生生境分解的相对重要性。对流域水文和养分通量的长期测量将把土壤特征与河流养分和有机物损失联系起来，并提供信息以衡量未来扰动的影响。关键种群、群落、生物地球化学和景观过程的模拟模型为这些新的观测和实验提供了零模型预测。

The Luquillo Experimental Forest LTER program (LUQ) focuses on the long-term dynamics of tropical forest ecosystems characterized by large-scale, infrequent disturbance, rapid processing of organic material, and high habitat and species diversity. Research by LUQ has stimulated a new appreciation of the significance of large-scale disturbances in tropical forested ecosystems and the key role of the biota in shaping the response to these events. Hurricanes occurring one and 10 years after the LTER program began permitted scientists to capitalize upon landscape-scale natural experiments which are followed closely. Among the most important findings from these natural experiments is that detrital dynamics plays a central role in forest recovery by influencing carbon and nutrient storage and flow. The central theme proposed is that disturbance, through its effects on detrital dynamics, is a dominant ecosystem driver at LUQ. Pulses of detritus shift the flow of energy within the food web, modify the availability and distribution of nutrients, and feed back on the composition and productivity of plant and animal communities. Rapid processing of detritus distinguishes LUQ from other forested LTER sites, where decomposition takes 2-20 times as long. A combination of long-term measurements, field experiments, simulation modeling, and cross-site comparisons are proposed to address five questions: (1) How do climatic factors, litter quality, and detritivore diversity regulate decomposition of detrital pulses? (2) How do terrestrial and aquatic food webs differ in response to detrital pulses? (3) What is the effect of disturbance frequency on nutrient cycling, plant community composition, and the accumulation of soil organic matter? (4) To what degree is the export of carbon and nutrients from watersheds a result of soil characteristics that are affected by detrital dynamics? (5) How do elevationally related changes in climate impact plant and detritivore communities, and how do these feed back on the quantity and quality of litter inputs and decomposition? The research will be conducted in two spatial contexts. In mid-elevation tabonuco forest, LUQ will continue long-term measurements of ecosystem response to hurricanes, landslides, and anthropogenic disturbance. An experiment will be initiated to mimic increased frequency of hurricanes to investigate the effect of increased detrital inputs on nutrient cycling, community composition, and organic matter accumulation, along with. Manipulations of key groups of invertebrates to gain a better understanding of similarities in detrital processing between aquatic and terrestrial food webs. New plots will be established to examine the effect of elevationally related changes in climate, plant communities, and decomposers on detrital processing. Manipulative experiments will compare the relative importance of abiotic and biotic controls on decomposition in terrestrial and aquatic habitats. Long-term measurements of hydrological and nutrient fluxes in watersheds will relate soil characteristics to stream nutrient and organic matter losses and provide information to gauge the effects of future disturbances. Simulation models of key population, community, biogeochemical, and landscape processes provide null-model predictions to inform these new observations and experiments.