ABSTRACT Nitrogen fertilization can increase above- and belowground forest growth and carbon storage in low nitrogen (N) environments. However, it may also induce changes in other parts of the ecosystem, such as altered composition and diversity of the ground vegetation. These changes may occur, for example, because of increased availability of nitrogen and light depletion due to a denser tree canopy. We studied vegetation changes at 11 experimental sites in Pinus sylvestris stands with low N-deposition, along a south–north gradient in Sweden. We estimated the relative cover of individual species and the data were analysed with a linear model, using total amount of fertilizer-N added, years since last fertilization, site and site index as independent variables. The relative cover of the dominant dwarf shrubs (Vaccinium myrtillus and Vaccinium vitis-idaea) increased following fertilization. In the bottom layer, N significantly increased the total cover of two of the three dominant species (Pleurozium schreberi and Dicranum spp.). For the third species (Hylocomium splendens) no detectable effect was found. For lichens as a group, the cover decreased following N fertilization. No effect of N fertilization on species diversity was detected at any of the sites, and the forest vegetation types remained unchanged.

中文翻译：

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施氮后北方苏格兰松林下林下植被的长期响应

摘要 在低氮 (N) 环境中，施氮肥可以增加地上和地下森林的生长和碳储存。然而，它也可能引起生态系统其他部分的变化，例如改变地面植被的组成和多样性。例如，这些变化可能会发生，因为氮的可用性增加和由于树冠更密导致的光耗竭。我们研究了瑞典南-北梯度低氮沉积的樟子松林 11 个试验点的植被变化。我们估计了单个物种的相对覆盖率，​​并使用线性模型对数据进行了分析，以施氮总量、自上次施肥以来的年数、立地和立地指数作为自变量。受精后优势矮灌木（Vaccinium myrtillus 和 Vaccinium v​​itis-idaea）的相对覆盖率增加。在底层，氮显着增加了三个优势物种中两个（Pleurozium schreberi 和 Dicranum spp.）的总覆盖度。对于第三种（Hylocomium splendens），没有发现可检测到的影响。对于地衣作为一个整体，施氮后覆盖层减少。在任何地点都未检测到施氮对物种多样性的影响，森林植被类型保持不变。施氮后覆盖率下降。在任何地点都未检测到施氮对物种多样性的影响，森林植被类型保持不变。施氮后覆盖率下降。在任何地点都未检测到施氮对物种多样性的影响，森林植被类型保持不变。