Long-term, Intersite Experiments of Leaf and Fine Root Decomposition

分解可以被认为是一个连续的过程，从新鲜的植物凋落物开始，导致形成越来越难降解的有机物质。这种耐火材料反过来又影响生态系统中营养物质的可用性、生产和碳固存。目前，仅对分解过程的早期阶段进行了深入研究。现有的少数长期数据表明，分解过程开始于不稳定凋落物成分最初的迅速损失，随着更顽固的化合物在剩余物质中所占比例越来越大，分解过程逐渐变慢。这个连续体可分为两个阶段：第一个阶段的特点是质量损失相对较快，营养物质固定，总体分解率迅速下降；第二阶段的特点是均匀缓慢的分解速率，并伴有养分矿化。当木质纤维素指数达到0.5时，这两个阶段之间发生转变。一组科学家，LIDET（长期站点间分解实验小组），已经开始了一组实验来测试这些一般关系是否在大范围的宏观气候和基质质量中是一致的。这些长期试验涉及17个LTER和4个其他合作站点，共31种凋落物。实验旨在跟踪质量，碳组分，总氮和磷的变化长达10年。这项研究的新资助部分支持增加7个新地点，以代表尚未涵盖的条件。它还支持凋落物分解过程中变化的化学特征，并测试四种分解模型（CENTURY、GEM、GENDEC和VEGIE），以预测整个28个地点的长期动态。分析和建模工作将评估模型预测凋落物分解第二阶段中碳、氮和磷的数量的能力，以及从恒定质量损失的初始阶段到非常缓慢质量损失的最终阶段之间的过渡时间。由28名科学家组成的LIDET小组通过LTER下建立的电子邮件网络进行协调，以促进场址间的通信。这个优秀的研究团队是由dr。哈蒙，梅利洛，穆尔黑德，帕顿，拉斯泰特和艾伯。

Decomposition can be thought of as a continuous process beginning with fresh plant litter and leading to formation of increasingly refractory organic matter. This refractory material in turn influences nutrient availability, production, and carbon sequestration in ecosystems. At present, only early stages of the decomposition process have been intensively researched. The few long-term data available indicate the decomposition process begins with an initial rapid loss of labile litter constituents and becomes progressively slower as more recalcitrant compounds compose an increasingly large fraction of the remaining material. This continuum can be divided into two phases: the first phase is characterized by a relatively rapid loss of mass, immobilization of nutrients, and a rapidly declining overall decomposition rate; the second phase is characterized by uniformly slow decomposition rates and is accompanied by nutrient mineralization. Transition between these two phases appears to occur when the lignocellulose index reaches 0.5. A team of scientists, LIDET (Long-term Intersite Decomposition Experiment Team), has started a set of experiments to test whether these general relationships are consistent across a wide range of macroclimates and substrate qualities. These long-term experiments involve 17 LTER and 4 other cooperating sites, and a total of 31 types of litter. Experiments are designed to follow changes in mass, carbon fractions, and total nitrogen and phosphorus for up to 10 years. This newly funded component of the study supports the addition of 7 new sites to represent conditions that are not yet covered. It also supports the chemical characterization of changes in litter as it decomposes and testing of four decomposition models (CENTURY, GEM, GENDEC, and VEGIE) to predict long term dynamics across the full suite of 28 sites. The analysis and modeling exercise will assess the ability of models to predict the amount of carbon, nitrogen, and phosphorus during the second phase of litter decomposition, as well as the timing of transition between the initial phase of constant mass loss and the final phase of very slow mass loss. The LIDET team of twenty-eight scientists is coordinated through the electronic mail network established under LTER to foster intersite communication. This outstanding research team is coordinated by Drs.Harmon, Melillo, Moorhead, Parton, Rastetter and Aber.