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Budgets of fixed nitrogen in the Orinoco Savannah Region: Role of pyrodenitrification
Author(s) -
Sanhueza Eugenio,
Crutzen Paul J.
Publication year - 1998
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/98gb02314
Subject(s) - amazon rainforest , environmental science , biomass (ecology) , vegetation (pathology) , ecosystem , dry season , nutrient cycle , wet season , terrestrial ecosystem , tropics , rainforest , nutrient , cycling , ecology , agroforestry , geography , forestry , biology , medicine , pathology
Human activities have strongly altered the amount of fixed nitrogen that cycles in many regions of the industrialized world, with serious environmental consequences. Past studies conducted at the Orinoco savannahs of Venezuela offer a unique possibility for reviewing the cycling of nitrogen species in a tropical environment. The available information for the Orinoco savannahs is critically reviewed, and, despite many uncertainties, we present a budget analysis of both the fixed N in the soil‐vegetation system and atmospheric NO y . Analysis of the data indicates that nitrogen fixation, especially by legumes, and ammonia emission from vegetation and animal wastes needs considerable attention in future research efforts. In contrast with many regions of the world, in the studied region, nonindustrial sources, foremost biomass burning, dominate the soil‐vegetation and atmospheric budgets of fixed N. In general, N cycling is mainly driven by biomass burning. The resulting pyrodenitrification in the soil‐vegetation system is the largest single process that, during the following wet season, may promote biological fixation to compensate for the N losses from fires during the burning season. However, a gradual impoverishment of the N status of the savannah ecosystems cannot be excluded. During the dry season, biomass burning is also the main source of atmospheric NO y , which is largely exported, mainly in the direction of the Amazon forest. Together with other nutrients, a “fertilization” of the Amazon forest due to biomass burning in the savannah may be the result. These issues require further scientific analysis.