Phosphorus Regulation of Decomposition, Microbial Dynamics, and Foliar Chemistry in Moist Tropical Forests

尽管人们普遍认为，低磷(P)有效性是许多热带森林生态系统动态的强烈制约因素，但对这一观点的直接测试很少，而且对热带森林生物地球化学的了解仍然相对较差。为了验证这一假设，将在哥斯达黎加西南部极其古老的土壤上的低地潮湿热带雨林中进行磷肥试验。初步工作表明，在这些系统中，磷的有效性很差，低磷的有效性似乎限制了土壤微生物的活动。这项研究将通过使用长期磷肥施肥区来跟踪这些初步数据，这些施磷区跨越土壤年龄的梯度，包括这些森林中至少3种不同的优势树冠树。每个单独的地块将在其中心包含一棵成熟的树冠树，这些树将包含永久的攀缘绳索，以提供通往活的树冠树叶的通道。除了施肥对树冠化学的影响外，这项研究还将监测土壤和森林地面上的过程，包括土壤呼吸、凋落物分解、微生物功能和组成的分析，以及一套土壤生物地球化学分析。这项工作将促进对磷有效性如何调节低地热带森林生态系统过程的理解，重点放在了解较少的微生物群落上。此外，研究人员寻求长期维护这些受精区，并促进其他有兴趣使用它们的科学家的合作。

Despite a widespread belief that low phosphorus (P) availability is a strong constraint on ecosystem dynamics in many tropical forests, direct tests of this belief are rare, and understanding of tropical forest biogeochemistry remains relatively poor. To test this assumption, a phosphorus fertilization experiment will be conducted in lowland moist tropical rainforests located on extremely old soils in southwest Costa Rica. Preliminary work has shown that P availability is poor in these systems, and that low P availability appears to limit the activity of soil microorganisms. This research will follow up on these preliminary data through the use of long-term P fertilization plots which span gradients in soil age and which include at least 3 different dominant canopy trees in these forests. Each individual plot will contain a mature canopy tree at its center, and the trees will contain permanent climbing ropes to provide access to live canopy leaves. In addition to the effects of fertilization on canopy chemistry, the research will monitor processes within the soil and on the forest floor, including soil respiration, litter decomposition, analyses of microbial function and composition, and a suite of soil biogeochemical analyses. This work will advance understanding of how P availability regulates ecosystem processes in lowland tropical forests, with an emphasis on the poorly understood microbial communities. In addition, the investigators seek to maintain these fertilization plots for the long term, and to facilitate collaboration from other scientists interested in using them.