N20 and N0 Flux from Tropical Pastures and Forests, Atmospheric Inputs, Seasonality, and Controlling Mechanisms

自然排放的氮氧化物是地球化学的 在当地氮收支方面的意义和对 大气化学 两种最重要的氮氧化物 在上下文中是一氧化二氮（N2 O）和一氧化氮（NO）。 目前的证据表明热带土壤可能是原生的 以及从一氧化二氮转化而来牧场 热带森林可能是N2 O的特别活跃的来源。 因为新热带森林正在转变为牧场， 如此大的规模，很明显，新热带森林- 向牧场过渡是最重要的生态系统类型， 应进行哪种N2 O通量测量。 对NO通量的了解比对N2 O的了解少得多， 现有的数据表明，NO可能是更重要的， 热带土壤中自然排放的氮氧化物比N2 O多。 数据强烈表明，NO通量应测量沿着 如果热带土壤被评估为NOx， 来源于大气层。 这项研究需要现场测量N2 O和NO通量 从代表原生林、次生林、 森林和牧场上相对肥沃的冲积土， 加勒比海低地相对贫瘠的残留土壤， 哥斯达黎加。 这些测量与并行 测量土壤性质，如H2O含量和NH 4 + 浓度不仅提供了年通量的估计值， 从土壤到大气，但将提供一个统计数据， 筛选潜在因果关系的方法。 等 多变量分析将涉及现场和实验室 实验来确定驱动这些通量的因果因素。 这项研究的整体重要性来自两个方面 主要来源。 首先，研究中的氮氧化物是 感觉到大气层阵列的主要组成部分 “温室”气体是导致全球气候变化的主要原因。 作为 这项研究将提供重要的基本信息， 关于热带地区土地利用变化的系统效应 环境. 在这方面，它应该产生重大的影响。 广泛实用的结果。

Naturally emitted nitrogen oxides are of biogeochemical significance in terms of local nitrogen budgets and influences on atmospheric chemistry. Two of the most important nitrogen oxides in the context are nitrous oxide (N2O) and nitric oxide (NO). Present evidence suggests that tropical soils may be primary source of N2O on a global basis and that pastures converted from tropical forests may be especially active sources of N2O. Because neotropical forests are being converted to pastures on such a large scale, it is evident that the neotropical forest- to-pasture transition is the most important kind of ecosystem in which N2O flux measurements should be made. Much less is known about NO flux than about N2O, but available data suggest that NO may be more important as a naturally emitted nitrogen oxide from tropical soils than is N2O. Data strongly indicate that NO fluxes should be measured along with N2O fluxes if tropical soils are to be evaluated as an NOx source to the atmosphere. This research entails field measurements of N2O and NO flux from replicated plots representing primary forest, secondary forest, and pastures on relatively fertile alluvial soils and relatively infertile residual soils in the Caribbean Lowlands of Costa Rica. These measurements together with concurrent measurements of soil properties such as H2O content and NH4+ concentration will not only provide an estimate of annual fluxes from soils to the atmosphere, but will provide a statistical means to screen for potential causal relations. Such multivariate analyses will be related to field and laboratory experiments to define causal factors driving these fluxes. The overall importance of this research derives from two primary sources. First, the oxides of nitrogen under study are felt to the major components of the array of atmospheric "greenhouse" gases that contribute to global climate changes. As well, the study will yield important fundamental information regarding the system effects of land use changes in tropical environments. In this context it should produce significant results of wide utility.