The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change. Issue 4 (3rd December 2013)

• Record Type: Journal Article
• Authors: Wilcke, Wolfgang; Leimer, Sophia; Peters, Thorsten; Emck, Paul; Rollenbeck, Rütger; Trachte, Katja; Valarezo, Carlos; Bendix, Jörg
• Is Part Of: Global biogeochemical cycles. Volume 27:Issue 4(2013)
• Page Start: 1194
• Page End: 1204
• Publication Date: 2013-12-03
• Subjects: Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/2012GB004471
• Languages: English
• ISSNs: 0886-6236

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>[1] Water‐bound nitrogen (N) cycling in temperate terrestrial ecosystems of the Northern Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to the environment. In little‐industrialized and remote areas, in contrast, a larger part of N cycling occurs as dissolved organic N (DON). In a north Andean tropical montane forest in Ecuador, the N cycle changed markedly during 1998–2010 along with increasing N deposition and reduced soil moisture. The DON concentrations and the fractional contribution of DON to total N significantly decreased in rainfall, throughfall, and soil solutions. This inorganic turn of the N cycle was most pronounced in rainfall and became weaker along the flow path of water through the system until it disappeared in stream water. Decreasing organic contributions to N cycling were caused not only by increasing inorganic N input but also by reduced DON production and/or enhanced DON decomposition. Accelerated DON decomposition might be attributable to less waterlogging and higher nutrient availability. Significantly increasing NO<sub>3</sub>‐N concentrations and NO<sub>3</sub>‐N/NH<sub>4</sub>‐N concentration ratios in throughfall and litter leachate below the thick organic layers indicated increasing nitrification. In mineral soil solutions, in contrast, NH<sub>4</sub>‐N concentrations increased and NO<sub>3</sub>‐N/NH<sub>4</sub>‐N concentration ratios decreased significantly, suggesting increasing net ammonification. Our results demonstrate that the remote tropical montane forests on the rim of the Amazon basin experienced a pronounced change of the N cycle in only one decade. This change likely parallels a similar change which followed industrialization in the temperate zone of the Northern Hemisphere more than a century ago.</p> </abstract>