Berger Torsten W, Berger Pétra
Department of Forest- and Soil Sciences, Institute of Forest Ecology, University of Natural Resources and Live Sciences (BOKU), Peter Jordan-Straße 82, 1190 Vienna, Austria.
Plant Soil. 2012;358(1-2):349-369. doi: 10.1007/s11104-012-1165-z. Epub 2012 Mar 7.
Replacement of beech by spruce is associated with changes in soil acidity, soil structure and humus form, which are commonly ascribed to the recalcitrance of spruce needles. It is of practical relevance to know how much beech must be admixed to pure spruce stands in order to increase litter decomposition and associated nutrient cycling. We addressed the impact of tree species mixture within forest stands and within litter on mass loss and nutritional release from litter.
Litter decomposition was measured in three adjacent stands of pure spruce (), mixed beech-spruce and pure beech () on three nutrient-rich sites and three nutrient-poor sites over a three-year period using the litterbag method (single species and mixed species bags).
Mass loss of beech litter was not higher than mass loss of spruce litter. Mass loss and nutrient release were not affected by litter mixing. Litter decay indicated non-additive patterns, since similar remaining masses under pure beech (47%) and mixed beech-spruce (48%) were significantly lower than under pure spruce stands (67%). Release of the main components of the organic substance (C, N, P, S, lignin) and associated K were related to mass loss, while release of other nutrients was not related to mass loss.
In contradiction to the widely held assumption of slow decomposition of spruce needles, we conclude that accumulation of litter in spruce stands is not caused by recalcitrance of spruce needles to decay; rather adverse environmental conditions in spruce stands retard decomposition. Mixed beech-spruce stands appear to be as effective as pure beech stands in counteracting these adverse conditions.
山毛榉被云杉取代与土壤酸度、土壤结构和腐殖质形态的变化有关，这些变化通常归因于云杉针叶的难分解性。了解在纯云杉林中必须混入多少山毛榉才能增加凋落物分解及相关养分循环具有实际意义。我们研究了林分和凋落物中树种混合对凋落物质量损失和养分释放的影响。
在三个营养丰富的地点和三个营养贫瘠的地点，使用凋落物袋法（单物种和混合物种袋），在三年时间内对三个相邻的纯云杉林分（）、山毛榉 - 云杉混交林和纯山毛榉林分（）进行凋落物分解测量。
山毛榉凋落物的质量损失不高于云杉凋落物的质量损失。质量损失和养分释放不受凋落物混合的影响。凋落物分解呈现非加性模式，因为纯山毛榉林下（47%）和山毛榉 - 云杉混交林下（48%）的相似剩余质量显著低于纯云杉林分下（67%）。有机物质（碳、氮、磷、硫、木质素）的主要成分及相关钾的释放与质量损失有关，而其他养分的释放与质量损失无关。
与普遍认为云杉针叶分解缓慢的假设相反，我们得出结论，云杉林中凋落物的积累不是由云杉针叶难分解导致的；而是云杉林中不利的环境条件阻碍了分解。山毛榉 - 云杉混交林在抵消这些不利条件方面似乎与纯山毛榉林一样有效。
