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，导致形成越来越难处理的有机物质。这种耐火材料反过来影响生态系统中养分的可获得性、产量和碳固存。目前，只对分解过程的早期阶段进行了深入的研究。为数不多的长期数据表明，分解过程开始于不稳定的垃圾成分的最初快速损失，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。这一连续体可分为两个阶段：第一阶段以质量损失较快、养分固定、总分解速率迅速下降为特征；第二阶段以均匀缓慢的分解速率为特征，并伴随着养分矿化。当木质纤维素指数达到0.5时，似乎发生了这两个阶段之间的转变。科学家团队LIDET(长期站点间分解实验团队)已经开始了一系列实验，以测试这些一般关系是否在大范围的大气候和基质质量中保持一致。这些长期实验涉及17个LTER和4个其他合作地点，以及总共31种类型的垃圾。实验旨在长达10年的时间里跟踪质量、碳组分以及总氮和磷的变化。这项研究的这一新资助部分支持增加7个新的地点，以代表尚未涵盖的情况。它还支持对凋落物分解时的变化进行化学表征，并测试四种分解模型(CENTERY、GEM、GENDEC和VEGIE)，以预测全套28个站点的长期动态。分析和建模练习将评估模型在凋落物分解的第二阶段预测碳、氮和磷的能力，以及从恒定质量损失的初始阶段到非常缓慢的质量损失的最后阶段之间的过渡时间。LIDET小组由28名科学家组成，通过在LTER下建立的电子邮件网络进行协调，以促进站点间通信。这个杰出的研究团队由Harmon、Melillo、Moorhead、Parton、Rastetter和Aber博士协调。

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.