EMISSIONS OF N2O AND CO2 FROM TERRA FIRME FORESTS IN RONDÔNIA, BRAZIL

Abstract

Nitrous oxide (N2O) functions as a greenhouse gas in the lower atmosphere and as a destroyer of the ozone layer in the upper atmosphere. Tropical forest soils are considered the largest natural N2O source, but the spatial pattern of the emissions is poorly understood because of the relatively small number of ground measurements and the lack of a good way to scale them. In this paper, we present a new approach for estimating the magnitude and spatial pattern of N2O emissions from tropical forest soils of the Amazon Basin. First, we develop an empirical relationship between N2O and CO2 emissions from tropical soils based on seven years of field measurements made in forests of Rondônia, Brazil. Second, we combine this empirical relationship with monthly estimates of forest soil respiration across the basin from a process‐based biogeochemistry model, the terrestrial ecosystem model, to estimate annual N2O fluxes and the spatial pattern of these fluxes from the region's undisturbed forests for the period 1980–1995. For this time interval, we estimate the average flux from the forest soils of the Amazon Basin was 7.9 × 1011 g N2O‐N/yr, with the highest subregional fluxes coming from the most productive forests in the northwestern part of the basin.