Effects of natural forest dynamics on vascular plant, bryophyte, and lichen diversity in primeval Fagus sylvatica forests and comparison with production forests

1. Stand structure, mean tree age, deadwood amount and microclimate all change markedly in the course of natural forest dynamics. The last remaining primeval forests of the temperate forest biome are valuable study objects to investigate the effects of forest dynamics and management on forest structure and function as well as phytodiversity, which is not sufficiently understood. 2. Three pairs of Fagus sylvatica primeval and production forests in eastern Slovakia were selected for studying the effects of natural forest development stages on vascular plant, bryophyte, and lichen species richness and composition. We further compared the diversity patterns in the initial, optimal and terminal stages of forest development with those of nearby production forests. 3. The plot-level species richness of epiphytic bryophytes and lichens increased from the initial to the terminal stage, but only lichens exhibited a significantly higher cumulative species richness (γ diversity) in the later (optimal and terminal) stages. No increase in species richness from the initial to the terminal stage was found for deadwood-inhabiting epiphytes and the ground-layer vascular plants. Canonical correspondence analyses identified characteristic bryophyte and lichen species for the different development stages, while the bulk of vascular ground layer species occurred across all stages with no stage preference. 4. Stem diameter was an even more important driver of epiphyte diversity and species composition than the development stage. All stages of the primeval forests (including the initial) were more species-rich in epiphytes and, when investigating larger plot numbers, also in vascular plants than the production forests. 5. Synthesis. In primeval forests of European beech, plant species richness did not differ significantly between the consecutive forest development stages, while species composition did. This is attributable to the smal-scale mosaic structure of the forest, rapid gap closure by beech, and the continuity of deadwood across the stages, which reduces spatio-temporal differences in microhabitat availability in the forest. Bryophytes and lichens are species-richer, and vascular plants at least similarly rich, in the primeval as compared to the production forests, if the study area is sufficiently large.

1. 林分结构、平均树龄、枯木量与小气候在天然林动态过程中均发生显著变化。现存为数不多的温带森林生物群系原始林，是探究森林动态与经营方式对森林结构、功能以及植物多样性（phytodiversity）影响的宝贵研究对象，目前学界对这些影响的认知仍不够充分。
2. 研究选取了斯洛伐克东部的3对欧洲山毛榉（Fagus sylvatica）原始林与生产林，用以探究天然林发育阶段对维管植物、苔藓植物以及地衣的物种丰富度与物种组成的影响。此外，本研究还将森林发育的初始阶段、最优阶段与顶级阶段的多样性格局，与邻近生产林的多样性格局进行了对比。
3. 附生苔藓植物与附生地衣的样地级物种丰富度从初始发育阶段到顶级阶段呈上升趋势，但仅地衣在后期（最优与顶级阶段）表现出显著更高的累积物种丰富度（γ diversity）。枯木栖生附生植物与地表层维管植物的物种丰富度，并未从初始阶段到顶级阶段出现提升。典范对应分析（canonical correspondence analyses）识别出了不同发育阶段的特征苔藓与地衣物种，而绝大多数地表维管植物物种在所有发育阶段均有分布，无明显的阶段偏好性。
4. 树干直径对附生植物多样性与物种组成的驱动作用，甚至比森林发育阶段更为显著。相较于生产林，所有发育阶段的原始林（包括初始阶段）的附生植物物种丰富度更高；若调查样地数量足够多，维管植物的物种丰富度也呈现同样趋势。
5. 综合讨论。欧洲山毛榉原始林中，植物物种丰富度在连续的森林发育阶段之间并无显著差异，但物种组成存在明显分异。这一现象可归因于森林的小尺度镶嵌结构、山毛榉快速填补林隙，以及各阶段枯木的连续性——这些因素降低了森林内微生境可利用性的时空差异。若研究区域足够大，原始林的附生苔藓与地衣物种丰富度更高，而维管植物的物种丰富度至少与生产林持平。