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

Luquillo实验森林LTER计划(LUQ)专注于热带森林生态系统的长期动态，其特点是大规模、罕见的干扰、对有机物质的快速处理以及高度的栖息地和物种多样性。LUQ的研究促使人们重新认识到热带森林生态系统中大规模扰动的重要性，以及生物群在影响对这些事件的反应方面的关键作用。在LTER计划开始一年和十年后发生的飓风使科学家能够利用受到密切关注的景观规模的自然实验。这些自然实验中最重要的发现之一是，碎屑动态通过影响碳和养分的储存和流动，在森林恢复中发挥核心作用。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。碎屑的脉冲改变了食物链内的能量流动，改变了营养的可获得性和分布，并反馈了动植物群落的组成和生产力。对碎屑的快速处理使LUQ有别于其他森林覆盖的LTER地点，后者的分解时间是后者的2-20倍。采用长期测量、野外实验、模拟模拟和现场比较相结合的方法来解决五个问题：(1)气候因素、凋落物质量和有害物种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)干扰频率对营养循环、植物群落组成、土壤有机质的积累？(4)从流域输出的碳和养分在多大程度上是受碎屑动态影响的土壤特性的结果？(5)与海拔相关的气候变化如何影响植物和有害的土壤群落，以及这些影响如何反馈到凋落物输入和分解的数量和质量？这项研究将在两个空间背景下进行。在中等海拔的Tabonuco森林，Luq将继续对飓风、山体滑坡和人为干扰的生态系统反应进行长期测量。将启动一项实验，以模拟飓风频率的增加，以调查增加的碎屑输入对养分循环、群落组成和有机质积累的影响。操纵无脊椎动物的关键群体，以更好地了解水生和陆地食物网在碎屑处理方面的相似之处。将建立新的地块，以检查气候、植物群落和分解者的海拔变化对碎屑加工的影响。操纵性实验将比较非生物和生物控制在陆地和水生生境中分解的相对重要性。对流域水文和营养通量的长期测量将使土壤特性与河流养分和有机质损失联系起来，并提供信息以衡量未来干扰的影响。关键的种群、群落、生物地球化学和景观过程的模拟模型提供了零模型预测，从而为这些新的观察和实验提供了信息。

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.