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Atmospheric deposition and net retention of ions by the canopy in a tropical montane forest, Monteverde, Costa Rica

Published online by Cambridge University Press:  01 January 1998

KENNETH L. CLARK
Affiliation:
School of Forest Resources and Conservation, University of Florida, Gainesville, FL 32605
NALINI M. NADKARNI
Affiliation:
The Evergreen State College, Olympia, WA 98505
DOUGLAS SCHAEFER
Affiliation:
University of Puerto Rico, San Juan, PR 00936
HENRY L. GHOLZ
Affiliation:
School of Forest Resources and Conservation, University of Florida, Gainesville, FL 32605
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Abstract

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Meteorological variables, bulk cloud water and precipitation (BCWP), and bulk precipitation (BP) were measured above the canopy, and throughfall (TF; n = 20) was collected beneath an epiphyte-laden canopy of a tropical montane forest (TMF) for 1 y at Monteverde, Costa Rica. Total deposition (cloud + wet + dry) of inorganic ions to the canopy was estimated using a sodium (Na+) mass balance technique. Annual BCWP and BP depths were 2678 mm and 1792 for events where mean windspeeds (u) ≥ 2 m s&supminus1;, and 4077 mm and 3191 mm for all events, respectively. Volume-weighted mean pH and concentrations of nitrate-N (NO3-N) and ammonium-N (NH4+-N) were 4.88, 0.09 and 0.09 mg l&supminus1; in BCWP, and 5.00, 0.05 and 0.05 mg l&supminus1; in BP, respectively. Cloud water and mist deposition to the canopy was estimated to be 356 mm. Estimated deposition of free acidity (H+), NO3-N, and NH4+-N to the canopy was 0.49, 3.4 and 3.4 kg ha&supminus1; y&supminus1;, respectively. Mean TF depth was 1054 ± 83 mm (mean ± S.E.) for events where u ≥ 2 m s&supminus1;, and 2068 ± 132 mm for all events. Volume-weighted mean pH and concentrations of NO3-N and NH4+-N in TF were 5.72, 0.04 mg l&supminus1;, and 0.07 mg l&supminus1;, respectively. Mean fluxes of H+, NO3-N, and NH4+-N in TF were 0.04 ± 0.01, 0.6 ± 0.2 and 1.3 ± 0.2 kg ha&supminus1; y&supminus1;, and percent net retention of these ions by the canopy was 92 ± 2, 80 ±6, and 61 ± 6%, respectively. Phosphate, potassium, calcium and magnesium were leached from the canopy. Seasonal data suggest that biomass burning increased concentrations of NO3 and NH4+ in cloud water and precipitation at the end of the dry season. Regardless, a large majority of the inorganic N in atmospheric deposition was retained by the canopy at this site.

Type
Research Article
Copyright
© 1998 Cambridge University Press