Publicaciones
Se encontró/encontraron 2 Publicaciones(s).
Wilcke, W.; Leimer, S.; Peters, T.; Emck, P.; Rollenbeck, R.; Trachte, K.; Valarezo, C. & Bendix, J. (2013): The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change. Global Biogeochemical Cycles 27(4), 1194-1204.
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DOI: 10.1002/2012GB004471
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Resumen:
Resumen:
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 NO3-N concentrations and NO3-N/NH4-N
concentration ratios in throughfall and litter leachate below the thick organic layers indicated
increasing nitrification. In mineral soil solutions, in contrast, NH4-N concentrations increased and NO3-N/NH4-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.
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Keywords: |
climate change |
nitrification |
N deposition |
terrestrial N cycling |
dissolved organic N |
Schwarz, M.T.; Oelmann, Y. & Wilcke, W. (2011): Stable N isotope composition of nitrate reflects N transformations during the passage of water through a montane rain forest in Ecuador. Biogeochemístry 102, 195-208.
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DOI: 10.1007/s10533-010-9434-5
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Resumen:
Resumen:
Knowledge of the fate of deposited N in the possibly N-limited, highly biodiverse north Andean forests is important because of the possible effects of N inputs on plant performance and species composition. We analyzed concentrations and fluxes
of NO3?N, NH4?N and dissolved organic N (DON) in rainfall, throughfall, litter leachate, mineral soil solutions (0.15?0.30 m depths) and stream water in a montane forest in Ecuador during four consecutive quarters and used the natural 15N abundance in NO3 during the passage of rain water through the
ecosystem and bulk d15N values in soil to detect N transformations. Depletion of 15N in NO3 and increased NO3
fluxes during the passage through the canopy and the organic layer indicated nitrification in these compartments. During leaching from the organic layer to mineral soil and stream, NO3
concentrations progressively decreased and were enriched in 15N but did not reach the d15N values of solid phase organic matter (d15N = 5.6?6.7%). This suggested a combination of nitrification and denitrification in mineral soil. In the wettest quarter, the d15N value of NO3 in litter leachate was smaller
(d15N = -1.58%) than in the other quarters (d15N = -9.38 ± SE 0.46%) probably because of reduced mineralization and associated fractionation against 15N. Nitrogen isotope fractionation of NO3 between litter leachate and stream water was smaller in the wettest period than in the other periods
probably because of a higher rate of denitrification and continuous dilution by isotopically lighter NO3-N from throughfall and nitrification in the organic layer during the wettest period. The stable N isotope composition of NO3
gave valuable indications of N transformations during the passage of water through the forest ecosystem from rainfall to the stream.
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Keywords: |
nitrate |
tropical montane forest |
denitrification |
nitrification |
15N natural abundance |
terrestrial N cycling |