Jagodziński A M, Horodecki P, Rawlik K, Dyderski M K
Institute of Dendrology, Polish Academy of Sciences, Kórnik, Poland.
Faculty of Forestry, Department of Game Management and Forest Protection, Poznań University of Life Sciences, Poznań, Poland.
Plant Biol (Stuttg). 2017 Jul;19(4):571-583. doi: 10.1111/plb.12569. Epub 2017 Apr 27.
One of the most important threats to peatland ecosystems is drainage, resulting in encroachment of woody species. Our main aim was to check which features - overstorey or understorey vegetation - are more important for shaping the seedling bank of pioneer trees colonising peatlands (Pinus sylvestris and Betula pubescens). We hypothesised that tree stand parameters will be more important predictors of natural regeneration density than understorey vegetation parameters, and the former will be negatively correlated with species diversity and richness and also with functional richness and functional dispersion, which indicate a high level of habitat filtering. The study was conducted in the 'Zielone Bagna' nature reserve (NW Poland). We assessed the structure of tree stands and natural regeneration (of B. pubescens and P. sylvestris) and vegetation species composition. Random forest and DCA were applied to assess relationships between variables studied. Understorey vegetation traits affected tree seedling density (up to 0.5-m height) more than tree stand traits. Density of older seedlings depended more on tree stand traits. We did not find statistically significant relationships between natural regeneration densities and functional diversity components, except for functional richness, which was positively correlated with density of the youngest tree seedlings. Seedling densities were higher in plots with lower functional dispersion and functional divergence, which indicated that habitat filtering is more important than competition. Presence of an abundant seedling bank is crucial for the process of woody species encroachment on drained peatlands, thus its dynamics should be monitored in protected areas.
泥炭地生态系统面临的最重要威胁之一是排水，这导致木本物种的侵入。我们的主要目的是检验哪些特征——上层植被或下层植被——对于塑造在泥炭地定居的先锋树种（欧洲赤松和毛桦）的幼苗库更为重要。我们假设林分参数将比下层植被参数更能预测自然更新密度，并且前者将与物种多样性和丰富度以及功能丰富度和功能离散度呈负相关，这表明存在高水平的生境过滤。该研究在“Zielone Bagna”自然保护区（波兰西北部）进行。我们评估了林分结构以及毛桦和欧洲赤松的自然更新情况以及植被物种组成。应用随机森林和去趋势对应分析来评估所研究变量之间的关系。下层植被特征对树幼苗密度（高达0.5米高）的影响大于林分特征。较老幼苗的密度更多地取决于林分特征。除了功能丰富度与最幼树幼苗的密度呈正相关外，我们没有发现自然更新密度与功能多样性组成部分之间存在统计学上的显著关系。在功能离散度和功能差异较低的样地中，幼苗密度较高，这表明生境过滤比竞争更重要。丰富的幼苗库的存在对于木本物种侵入排水后的泥炭地的过程至关重要，因此应在保护区监测其动态。
