Estimates of ion sources in deciduous and coniferous throughfall |
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| Institution: | 1. Department of Forest Engineering, Resources, and Management, Oregon State University, Corvallis, OR 97331, USA;2. Plum Creek Timber Company, Toledo, OR 97391, USA;1. Graduate Program in Environmental Science, Thompson Rivers University, Kamloops, British Columbia, Canada;2. Departments of Geography and Plant and Soil Sciences, University of Delaware, Newark, DE 19716, USA;3. Department of Geography & Environmental Studies, Thompson Rivers University, Kamloops, British Columbia, Canada;4. Department of Geography, University of Delaware, Newark, DE 19716, USA;5. Department of Physical Sciences, Thompson Rivers University, Kamloops, British Columbia, Canada;1. Takayama Field Station, River Basin Research Center, Gifu University, 919-47 Iwaimachi, Takayama, Gifu 506-0815, Japan;2. School of Humanities and Culture, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan;3. Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga, Shizuoka, Shizuoka 422-8017, Japan;4. Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsucho, Shinjuku-ku, Tokyo 162-8480, Japan |
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| Abstract: | Estimates of external and internal sources of ions in net througfall deposition were derived for a deciduous and coniferous canopy by use of multiple regression. The external source component appears to be dominated by dry deposition of Ca2+, SO2 and NO3? during dormant and growing seasons for the two canopy types. Increases in the leaching rates of K+ and Mg2+ during the growing season reflect the presence of leaves in the deciduous canopy and increased physiological activity in both canopies. Internal leaching rates for SO42? doubled during the growing season presumably caused by increased physiological activity and uptake of SO2 through stomates. Net deposition of SO42? in throughfall during the growing season appears highly dependent on stomatal uptake of SO2. Estimates of SO2 deposition velocities were 0.06 cm s?1 and 0.13 cm s?1 for the deciduous and coniferous canopies, respectively, during the dormant seasons, and 0.30 cm s?1 and 0.43 cm s?1 for the deciduous and coniferous canopies, respectively, during the growing season. For the ions of major interest with respect to ecosystem effects, namely H+, NO3? and SO42?, precipitation inputs generally outweighed estimates of dry deposition input. However, net throughfall deposition of NO3? and SO42? accounted for 20–47 and 34–50 per cent, respectively, of total deposition of those ions. Error estimates of ion sources were at least 50–100 per cent and the method is subject to several assumptions and limitations. |
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