LTER Cross-site: Collaborative Research: DIRT: A Cross-continental, Experimental Study of Forest Soil Organic Matter and Nitrogen Dynamics

[00:87081]许多关于分解的研究都集中在有机物分解的短期、瞬时效应上。这些研究对凋落物养分含量和碳质量在控制养分通过凋落物层向土壤有机质（SOM）循环中的作用有了更多的了解。然而，人们对植物凋落物的命运及其在几十年到几个世纪的时间尺度上决定SOM含量和养分循环的作用知之甚少。为了解决这一差距，在三个美国LTER和一个国际LTER站点的森林站点独立建立了控制土壤有机质形成或DIRT（碎屑输入和去除处理）的长期实验研究。土块处理包括长期的地上和地下凋落物加倍和清除。虽然这些装置的基本实验设计是相似的，但很少有共同的测量方法，每个站点的仪器都非常不同。这个LTER跨站点研究项目的目的是使这四个站点具有一般的实验和测量一致性，并测试在该网络上各个站点进行的模型和假设。LTER项目是新兴的跨站点DIRT网络的理想宿主，因为它是许多研究人员的焦点，而且它的重点是长期研究。DIRT项目的中心目标是评估植物凋落物输入的速率和来源如何在十年时间尺度上控制森林土壤中有机质和养分的积累和动态。这种跨场地比较将解决三个具体目标：(1)研究森林地表生物量、有机质输入、来源和化学对淋滤液中净氮保留和无机氮与有机氮损失率的影响；(2)研究森林地表化学对总氮矿化、固定和硝化速率的影响；(3)评价土壤呼吸碳源模型的通用性。

0087081LajthaNumerous studies of decomposition have focused on short-term, transient effects of organic matter breakdown. Much has been learned from these studies about the roles of litter nutrient content and carbon quality in controlling the cycling of nutrients through the litter layer to soil organic matter (SOM). However, far less is known about the fate of plant litter and its role in determining SOM content and nutrient cycling over time scales ranging from decades to centuries. To address this gap, long-term experimental studies of controls on soil organic matter formation, or DIRT (Detritus Input and Removal Treatments), have been established independently at forested sites in three US LTERs and one international LTER site. DIRT plot treatments consist of long-term above- and below ground litter doubling and removal. While the fundamental experimental design of these installations is similar, there are few measurements in common and each site is instrumented quite differently. The purpose of this LTER cross-site research project is to bring these four sites into a general experimental and measurement uniformity, and to test models and hypotheses made at individual sites over this network. The LTER program serves as an ideal host for the emerging cross-site DIRT network both because it serves as a focal point for many investigators and because of its focus on long-term studies. The central goal of the DIRT project is to assess how rates and sources of plant litter inputs control accumulation and dynamics of organic matter and nutrients in forest soils over decadal time scales. This cross-site comparison will address three specific goals: (1) to examine effects of forest floor biomass, organic matter inputs, sources, and chemistry on net N retention and the ratio of inorganic to organic N losses in leachate; (2) to examine the effects of forest floor chemistry on gross N mineralization, immobilization, and nitrification rates; and (3) to evaluate the generality of models of sources of C to soil respiration.