Free University of Bozen-Bolzano, Faculty of Agricultural, Environmental and Food Sciences, Bolzano, Italy; University of Göttingen, Department of Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences and Forest Ecology, Göttingen, Germany.
University of Göttingen, Department of Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences and Forest Ecology, Göttingen, Germany.
J Environ Manage. 2023 Oct 1;343:118199. doi: 10.1016/j.jenvman.2023.118199. Epub 2023 May 25.
The understorey vegetation of temperate forests harbours a major proportion of terrestrial biodiversity and fulfills an important role in ecosystem functioning. Over the past decades, temperate forest understoreys were found to change in species diversity and composition due to several anthropogenic and natural drivers. Currently, the conversion and restoration of even-aged coniferous monocultures into more diverse and mixed broad-leaved forests are major objectives of sustainable forest management in Central Europe. This forest conversion alters understorey communities and abiotic site conditions but the underlying patterns and processes are not yet fully understood. Therefore, we investigated changes in the Bavarian Spessart mountains in southwest Germany, where we re-sampled 108 semi-permanent plots from four different coniferous stand types (i.e., Norway spruce, Scots pine, Douglas fir, European larch) about 30 years after the initial assessment. On these plots, we recorded understorey vegetation and forest structure, and derived abiotic site conditions based on ecological indicator values of understorey vegetation, followed by multivariate analysis. We found changes in plant communities that point towards a decrease of soil acidity and a "thermophilization" of forest understoreys. Understorey species richness remained constant, while understorey's Shannon and Simpson diversity increased. The observed changes in forest structure explained the temporal shifts in understorey species composition. The understorey species composition did not experience a significant floristic homogenization since the 1990s. However, plant communities exhibited a reduction in species characteristic of coniferous forests and a simultaneous increase in species associated with broad-leaved forests. The increase of specialist species (closed forests and open sites) may have compensated for the detected decrease in generalist species. We conclude that the forest conversion towards mixed broad-leaved forest in the Spessart mountains of the past decades might have masked homogenization trends that are increasingly reported from Central European forest understoreys.
温带森林的林下植被拥有很大一部分陆地生物多样性，并在生态系统功能中发挥着重要作用。在过去的几十年中，由于多种人为和自然驱动因素，温带森林林下植被在物种多样性和组成方面发生了变化。目前，将同龄针叶林单一栽培转变为更加多样化和混合的阔叶林，是中欧可持续森林管理的主要目标。这种森林转换改变了林下群落和非生物生境条件，但其中的模式和过程尚未完全了解。因此，我们研究了德国巴伐利亚施佩萨尔特山区的变化情况，大约 30 年前，我们在四个不同的针叶林林分类型（挪威云杉、欧洲赤松、花旗松、欧洲落叶松）中重新采样了 108 个半永久性样地，这些样地最初进行了评估。在这些样地上，我们记录了林下植被和森林结构，并根据林下植被的生态指标值，得出了非生物生境条件，随后进行了多元分析。我们发现，植物群落发生了变化，表明土壤酸度降低，森林林下“喜暖化”。林下物种丰富度保持不变，而林下 Shannon 和 Simpson 多样性增加。观察到的森林结构变化解释了林下物种组成的时间变化。自 20 世纪 90 年代以来，森林下物种组成并没有经历明显的趋同变化。然而，植物群落表现出针叶林特征种的减少和阔叶林特征种的同时增加。专化种（封闭林分和开阔地）的增加可能弥补了已检测到的广布种的减少。我们得出结论，过去几十年中施佩萨尔特山区向混合阔叶林的森林转换可能掩盖了中欧森林林下日益报道的趋同趋势。
