Data from: Regeneration processes on coarse woody debris in mixed forests: do tree germinants and seedlings have species-specific responses when grown on coarse woody debris?

1. Tree regeneration on coarse woody debris (CWD) is considered to be one the most ecologically valuable aspects of CWD in forest systems. However, most studies have focused solely on uncovering the differences in establishment and growth on CWD (regarded as a homogeneous substrate) in comparison to the forest floor. Our study concentrates on the underlying mechanisms of germinant and seedling colonization patterns and demographic responses relative to various properties of CWD. 2. We analyzed the effects of CWD properties (decay class, form, species and diameter) on: (1) germinant and seedling annual counts, (2) annual germinant and seedling survival, and (3) seedling growth and height. Our study comprised three species (beech, fir, and spruce) over 7-year span in two old-growth stands in the Western Carpathians, and employed generalized linear models and mixed models to test for differences between species. 3. CWD properties affected regeneration at the germination stage. There were some demographic differences between species relative to CWD properties. Decay class had the most pronounced effect on beech, not only on its establishment but also survival and growth. Beech and spruce established and survived in higher densities on beech CWD, while their height growth was enhanced on conifer-derived CWD, particularly on spruce CWD. Stumps enhanced establishment of all species and survival of conifer seedlings. 4. Synthesis: Our study shows that CWD properties do influence seedling establishment, growth, height distribution and survival. Moreover, there may be trade-offs between seedling growth and survival among tree species growing on different species of CWD. This highlights the need to include CWD heterogeneity as a factor that can affect the role of CWD in regeneration in forest ecosystems.

1. 森林生态系统中，粗木质残体（coarse woody debris, CWD）上的树木更新被认为是CWD最具生态价值的功能之一。然而，现有研究大多仅聚焦于对比粗木质残体（常被视为均质基质）与林地地表的树木定植与生长差异。本研究旨在揭示不同粗木质残体属性下，树木萌发体与幼苗的定植格局及种群动态响应的内在机制。
2. 我们分析了粗木质残体的各项属性（腐烂等级、形态、物种来源与径级）对以下三方面的影响：（1）萌发体与幼苗的年度数量；（2）萌发体与幼苗的年度存活率；（3）幼苗的生长与株高。本研究以西喀尔巴阡山脉的两处老龄林分为研究样地，历时7年跟踪3个树种（山毛榉、冷杉与云杉）的更新过程，并采用广义线性模型与混合效应模型检验不同树种间的差异。
3. 粗木质残体属性会作用于树木更新的萌发阶段。不同树种对粗木质残体属性的种群动态响应存在显著差异。腐烂等级对山毛榉的影响最为显著，不仅涉及定植过程，还包括存活与生长表现。山毛榉与云杉在山毛榉来源的粗木质残体上定植密度与存活率更高，而它们的株高生长在针叶树来源的粗木质残体上得到促进，尤以云杉来源的粗木质残体效果最为突出。残桩可提升所有树种的定植率，并提高针叶树幼苗的存活率。
4. 研究总结：本研究证实，粗木质残体属性确实会影响幼苗的定植、生长、株高分布与存活率。此外，生长在不同物种来源粗木质残体上的树种，其幼苗生长与存活之间可能存在权衡关系。这一结果凸显了在森林生态系统更新研究中，需将粗木质残体异质性作为影响其功能发挥的关键因子纳入考量。