Data to: Enjoying tranquility - Development of ground vegetation after cessation of management in forests on loamy soils in Flanders (Belgium)

Questions: Managed forests often show a more homogeneous age structure compared to untouched forests, but also a higher share and frequency of sun-exposed conditions due to harvest operations. Frequent, small-scaled forestry operations may therefore lead to elevated species richness, compared to undisturbed forests. When non-intervention is introduced in formerly managed forests, Is there a significant decrease in species richness of vascular plant species? What species are particularly affected? Are there nonrandom shifts in species composition? Are also typical shadetolerant forest species jeopardized due to prolonged deep shade ? Location: Four recently installed strict reserves in Atlantic to Sub-Atlantic lowland oak and beech forests on fertile loess soils east and south-west of Brussels (Belgium). Methods: We compared vegetation relevés in permanent plots (183 plots of 16x16m) with a 10 year interval. Total species richness per site was derived from rarefaction curves; significance of differences in species richness and composition at plot level were tested using paired t-tests and Wilcoxon signed rank tests. NMDS was used to visualize non-random shifts in species composition. Results: We registered significant declines in species richness both at reserve and plot level. This decline was not random, but strongly depending on ecological traits and strategies, with strong declines in light-demanding gap phase-associated species like Lonicera periclymenum and Deschampsia cespitosa, and species requiring disturbed or bare soils for their recruitment, such as Juncus effusus and Carex sylvatica. Shade-tolerant mesic species like Anemone nemorosa and Allium ursinum clearly increased in frequency and cover, despite strong declines in previous decades. Conclusion: The combined effect of continued closed canopy and slow soil recovery from euthrophication apparently support the development of a less species rich vegetation, but with higher dominance of characteristic species of mesic lowland oak and beech forests.

研究问题：与未受干扰的原始森林相比，人工经营林通常呈现更为均一的年龄结构，同时因采伐作业导致光照暴露条件的占比与发生频率更高。因此，频繁的小规模林业作业可能相较未受干扰森林提升物种丰富度。若对既往经营的森林停止人工干预，维管植物（vascular plant）物种的丰富度是否会出现显著下降？哪些物种受影响最为显著？物种组成是否存在非随机的变化？典型的耐阴森林物种是否会因长期重度遮阴而受到威胁？

研究区域：本研究选取比利时布鲁塞尔东部与西南部的四块新近设立的严格保护地，其生境为位于肥沃黄土母质土壤上的大西洋至亚大西洋低地栎林与山毛榉林。

研究方法：本研究对比了间隔10年的永久样地植被调查数据：共设置183个16m×16m的永久样地。样地总物种丰富度通过稀疏化曲线计算得出；采用配对t检验与Wilcoxon符号秩检验，分析样地水平物种丰富度与组成差异的显著性；利用非度量多维标度法（Non-metric Multidimensional Scaling, NMDS）可视化物种组成的非随机变化。

研究结果：本研究观测到保护地与样地水平的物种丰富度均出现显著下降。该下降并非随机发生，而是显著依赖于物种的生态性状与生存策略：喜光性林隙伴生物种（如鬼吹箫*Lonicera periclymenum*、发草*Deschampsia cespitosa*）以及需以干扰或裸地完成定居的物种（如灯心草*Juncus effusus*、林苔草*Carex sylvatica*）的丰富度均出现大幅下降。尽管近数十年间种群规模曾大幅下降，但耐阴中生物种（如银莲花*Anemone nemorosa*、熊韭*Allium ursinum*）的频度与盖度均显著提升。

研究结论：持续闭合的林冠层与土壤富营养化后恢复缓慢的共同作用，显然促使植被群落向物种丰富度更低的方向发展，但中生低地栎林与山毛榉林的特征物种的优势度却有所提升。