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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

Abstract

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

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