资源环境科技发展态势分析平台

Denitrification and hydrologic leaching are the two major pathways by which nitrogen (N) is lost from the terrestrial biosphere. Humid tropical forests are thought to dominate denitrification losses from unmanaged lands globally, but there is large uncertainty about the range and key drivers of total N gas emissions across the biome. We combined pantropical measures of small watershed stream chemistry with ecosystem modeling to determine total N gas losses and associated uncertainty across humid tropical forests. Our calculations reveal that denitrification in soils and along hydrologic flow paths contributes on average >45% of total watershed N losses. However, when denitrification occurs exclusively in shallow soils, simulations indicate that gas emissions would exceed N inputs and render plants severely N limited, which contradicts observations of widespread N sufficiency in tropical forests. Our analyses suggest an upper bound on soil denitrification of similar to 80% of total external N losses beyond which tropical plant growth would be compromised.