Impact of Harvest Intensity on Long-Term Base Cation Budgets in Swedish Forest Soils |
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Authors: | Cecilia Akselsson Olle Westling Harald Sverdrup Johan Holmqvist Gunnar Thelin Eva Uggla Gunnar Malm |
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Institution: | 1. IVL Swedish Environmental Research Institute, P. O. Box 5302, 400 14, Gothenburg, Sweden 2. Department of Chemical Engineering, Lund Institute of Technology, Lund, Sweden 3. SWECO International AB, Malm?, Sweden 4. Kalmar University, Kalmar, Sweden
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Abstract: | The effects of harvesting on the long-term mass balances of calcium (Ca), magnesium (Mg) and potassium (K) were evaluated
on a regional level in Sweden. A new high-resolution weathering database was used together with estimates of total deposition,
losses through harvest and leaching. Estimates were made for pine and spruce separately and for two harvesting intensity scenarios:
stem harvesting and whole-tree harvesting. The mass balance calculations showed net losses of Ca and Mg in almost the whole
country for both scenarios. The losses were smaller for pine than for spruce. The K balances were mainly positive for pine
but negative for spruce. Leaching was a main factor in the mass balances, especially for Ca and Mg. Whole-tree harvesting
in spruce forests led to substantially higher net losses of K and Ca than stem harvesting, according to the calculations.
In the whole-tree harvesting scenario in spruce forests the estimated yearly net losses of Ca, Mg and K corresponded to at
least 5%, 8% and 3% of the pools of exchangeable base cations, respectively, at 25% of the analysed sites. If losses of this
magnitude continue the depletion of the pools of Ca, Mg and K may lead to very low base saturation of the soils, possibly
accompanied by negative effects on soil fertility, runoff water quality, tree vitality and tree growth within a forest rotation
in parts of Sweden. Avoiding whole-tree harvesting can improve the situation substantially for K, but the losses of Ca and
Mg will still be significant. |
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Keywords: | base cations calcium forest soils forestry magnesium pine potassium spruce Sweden harvesting |
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