Chronic Nitrogen Additions to Forest Ecosystems: Effects of Nitrogen Cycling, Canopy Chemistry, and Trace Gas Emissions

这项研究项目将集中于继续在阔叶林和红松林中增加氮素，并测量基本的氮素循环参数，如矿化、硝化和植物吸收，包括绿叶含量。该项目还将估计N在垃圾落下和垃圾腐烂中返回系统的情况。此外，还将测量痕量气体通量(二氧化碳、N2O、CH4)。假设微量气体通量在很大程度上受土壤微生物对碳和氮的短期可获得性的控制，而这些可获得性又受到土壤可获得性和植物需求之间的反馈的制约。研究了氮素添加对土壤总氮和净氮固定和矿化的影响，对凋落物和土壤有机质腐烂过程中有效碳的生产和消耗的影响，以及对穿透雨中有效碳和无机氮含量的影响。

This research project will concentrate on continuing the Nitrogen additions in both the hardwood and red pine stands, and measuring basic N cycling parameters such as mineralization, nitrification, and plant uptake, including green foliar content. The project will also estimate N return to the system in litter fall and litter decay. As well, trace gas fluxes (CO2, N2O, CH4) will be measured. It is hypothesized that trace gas fluxes are controlled to a significant degree by short-term availability of carbon and nitrogen to soil microbes, and that these availabilities are, in turn, constrained by feedbacks between soil availability and plant demand. The effects of N additions on gross and net N immobilization and mineralization, on the production and consumption of available carbon during litter and soil organic matter decay, and on the available carbon and inorganic nitrogen content of throughfall will be investigated.