Heiland Lukas, Kunstler Georges, Šebeň Vladimír, Hülsmann Lisa
Bayreuth Center of Ecology and Environmental Research (BayCEER), Ecosystem Analysis and Simulation (EASI) Lab University of Bayreuth Bayreuth Germany.
Theoretical Ecology University of Regensburg Regensburg Germany.
Ecol Evol. 2023 Jul 4;13(7):e10232. doi: 10.1002/ece3.10232. eCollection 2023 Jul.
In forest communities, light competition is a key process for community assembly. Species' differences in seedling and sapling tolerance to shade cast by overstory trees is thought to determine species composition at late-successional stages. Most forests are distant from these late-successional equilibria, impeding a formal evaluation of their potential species composition. To extrapolate competitive equilibria from short-term data, we therefore introduce the JAB model, a parsimonious dynamic model with interacting size-structured populations, which focuses on sapling demography including the tolerance to overstory competition. We apply the JAB model to a two-"species" system from temperate European forests, that is, the shade-tolerant species L. and the group of all competing species. Using Bayesian calibration with prior information from external Slovakian national forest inventory (NFI) data, we fit the JAB model to short time series from the German NFI. We use the posterior estimates of demographic rates to extrapolate that will be the predominant species in 94% of the competitive equilibria, despite only predominating in 24% of the initial states. We further simulate counterfactual equilibria with parameters switched between species to assess the role of different demographic processes for competitive equilibria. These simulations confirm the hypothesis that the higher shade tolerance of saplings is key for its long-term predominance. Our results highlight the importance of demographic differences in early life stages for tree species assembly in forest communities.
在森林群落中，光照竞争是群落组装的关键过程。人们认为，物种在幼苗和幼树对上层树木遮荫的耐受性方面的差异决定了演替后期阶段的物种组成。大多数森林距离这些演替后期的平衡状态较远，这阻碍了对其潜在物种组成的正式评估。因此，为了从短期数据推断竞争平衡，我们引入了JAB模型，这是一个具有相互作用的大小结构种群的简约动态模型，它侧重于幼树种群统计学，包括对上层竞争的耐受性。我们将JAB模型应用于欧洲温带森林的一个两“物种”系统，即耐荫物种L.和所有竞争物种的组合。利用来自斯洛伐克国家森林清查（NFI）外部数据的先验信息进行贝叶斯校准，我们将JAB模型拟合到德国NFI的短时间序列中。我们利用人口统计学速率的后验估计来推断，尽管在初始状态中仅占24%，但在94%的竞争平衡中将成为优势物种。我们进一步模拟了物种间参数切换的反事实平衡，以评估不同人口统计学过程对竞争平衡的作用。这些模拟证实了这样一个假设，即L.幼树较高的耐荫性是其长期占优势的关键。我们的结果强调了早期生命阶段人口统计学差异对森林群落中树种组装的重要性。
