Resin-core and buried-bag estimates of nitrogen transformations in Costa Rican lowland rainforests |
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Authors: | Xiaoming Zou David W Valentine Robert L Sanford Jr Dan Binkley |
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Institution: | (1) Department of Forest Sciences, Colorado State University, 80523 Fort Collins, CO, USA;(2) Natural resource Ecology Laboratory, Colorado State University, 80523 Fort Collins, CO, USA |
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Abstract: | We compared the resin-core and buried-bag incubation methods for estimating nitrogen (N) transformation rates using the 15N pool dilution technique in alluvial soils of an early successional forest (ESF) and an old-growth forest (OGF) at the La Selva Biological Station in Costa Rica. Soil cores (38×100-mm) from both forests were incubated in situ for 7 days. The two methods gave generally similar estimates of net N mineralization rates for the two forests. Estimates of ammonium production by the resin-core method were higher than those by the buried-bag method in ESF, but did not differ significantly in OGF (p<0.05). Estimates of nitrate production by the two methods did not differ significantly. Nitrate averaged 74% and 81% of the total inorganic N production in ESF and OGF, respectively. Net N mineralization in ESF (6.6 mmol m-2d-1) did not differ significantly from that in OGF (5.0 mmol m-2d-1). Fluxes of ammonium and nitrate were high for both forests, but the OGF tended to have higher gross mineralization and nitrification rates than ESF. Approximately 60% of the gross nitrate production and less than 30% of the ammonium were immobilized by microorganisms. |
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Keywords: | early-successional forest gross N mineralization moist tropics N immobilization 15N nutrification nutrient cycling old-growth forest |
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