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

本研究项目将集中研究硬木和红松林分氮的持续添加，并测量基本的氮循环参数，如矿化、硝化和植物吸收，包括绿叶含量。该项目还将估算凋落物和凋落物腐烂过程中N的回归。同时，痕量气体通量（CO2, N2O, CH4）也将被测量。据推测，微量气体通量在很大程度上受土壤微生物的碳和氮的短期有效性控制，而这些有效性反过来又受到土壤有效性和植物需求之间反馈的限制。研究了施氮量对总氮和净氮的固定和矿化、凋落物和土壤有机质腐烂过程中速效碳的产生和消耗、穿透物速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.