Duchesne Louis, Houle Daniel
Direction de la Recherche Forestière, Forêt Québec, Ministère des Ressources Naturelles et de la Faune du Quobec, 2700 Einstein, Sainte-Foy, Québec GIP3W8, Canada.
Ecol Appl. 2008 Oct;18(7):1642-51. doi: 10.1890/07-1035.1.
The cycling of base cations (K, Ca, Mg, and Na) was investigated in a boreal balsam fir forest (the Lake Laflamme Watershed) between 1999 and 2005. Base cation budgets were calculated for the soil rooting zone that included atmospheric deposition and soil leaching losses, two scenarios of tree uptake (whole-tree and stem-only harvesting), and three scenarios of mineral weathering, leading to six different scenarios. In every scenario there was a net accumulation of Mg within the soil exchangeable reservoir, while Ca accumulated in four scenarios. Potassium was lost in five of the six scenarios. Contrary to Ca and Mg, immobilization of K within tree biomass (69 mol x ha(-1) x yr(-1)) was the main pathway of K losses from the soil exchangeable reservoir, being five times higher than losses via soil leaching (14 mol x ha(-1) x yr(-1)). The amounts of K contained within the aboveground biomass and the exchangeable soil reservoir were 3.3 kmol/ha and 4.2 kmol/ha, respectively. Whole-tree harvesting may thus remove 44% of the K that is readily available for cycling in the short term, making this forest sensitive to commercial forestry operations. Similar values of annual K uptake as well as a similar distribution of K between tree biomass and soil exchangeable reservoirs at 14 other coniferous sites, distributed throughout the boreal forest of Quebec, suggest that the Lake Laflamme Watershed results can be extrapolated to a much larger area. Stem-only harvesting, which would reduce K exports due to biomass removal by 60%, should be used for these types of forest.
1999年至2005年期间，在北方香脂冷杉林（拉弗拉姆湖流域）对碱金属阳离子（钾、钙、镁和钠）的循环进行了研究。计算了土壤根区的碱金属阳离子收支，其中包括大气沉降和土壤淋溶损失、两种树木吸收情况（全树采伐和仅树干采伐）以及三种矿物风化情况，从而得出六种不同情况。在每种情况下，土壤交换性储库中镁都有净积累，而钙在四种情况下有积累。六种情况中有五种钾出现流失。与钙和镁不同，钾在树木生物量中的固定（69摩尔·公顷⁻¹·年⁻¹）是土壤交换性储库中钾流失的主要途径，比通过土壤淋溶的流失量（14摩尔·公顷⁻¹·年⁻¹）高五倍。地上生物量和土壤交换性储库中所含钾的量分别为3.3千摩尔/公顷和4.2千摩尔/公顷。因此，全树采伐可能会在短期内去除44%易于循环的钾，使这片森林对商业林业经营敏感。魁北克北方森林中分布的其他14个针叶林站点的年钾吸收量以及钾在树木生物量和土壤交换性储库之间的分布情况与之相似，这表明拉弗拉姆湖流域的结果可以外推到更大的区域。对于这类森林，应采用仅树干采伐，这样可将因生物量移除导致的钾输出减少60%。
