论文标题
关于简约模型在沿着Savanna Biome中生物地理梯度研究树草生物量分布的有用性
On the usefulness of a minimalistic model to study tree-grass biomass distributions along biogeographic gradients in the savanna biome
论文作者
论文摘要
我们提出并分析了一个旨在作为树草相互作用的动态结果的模型，在降雨梯度沿区域/大陆尺度下，在稀树草原生物群落中可观察到的广泛的植被体域。该模型基于两个普通的微分方程（ODE），用于木质和草生物量。它是从文献中进行参数化并保留数学障碍性的，因为我们将其限制在主要过程中，尤其是树草不发育的相互作用（促进或竞争性）和草火反馈。我们使用完全定性的分析来得出所有可能的长期动态，并在Bifur-cation图中表达与平均年降雨和火灾频率有关的。我们描绘了单位稳定性（森林，草原，稀树草原），双重性（例如森林 - 格拉斯兰或森林 - 萨瓦纳），甚至是可疑性的领域。值得注意的是，我们强调了两个大草原平衡可能是稳定的区域（可能是森林或草原）。我们验证了与以前使用类似ODE框架的尝试相反，所有水平的降雨量都可以回收有关随着火灾频率增加木质生物量的常识。因此，该框架似乎能够呈现出比经常想象的更现实和多样化的结果。我们的模型可以帮助弄清在当地数据稀疏或不存在的大型领土上的稀树草原植被的持续动态。为了探索使用模型参数不同组合的分叉图，我们已经开发了一个用户友好的R-shiny应用程序，网址为：https：//gitlab.com/cirad-apps/tree-grass。
We present and analyze a model aiming at recovering as dynamical outcomes of tree-grass interactions the wide range of vegetation physiognomies observable in the savanna biome along rainfall gradients at regional/continental scales. The model is based on two ordinary differential equations (ODE), for woody and grass biomass. It is parameterized from literature and retains mathematical tractability, since we restricted it to the main processes, notably tree-grass asym-metric interactions (either facilitative or competitive) and the grass-fire feedback. We used a fully qualitative analysis to derive all possible long term dynamics and express them in a bifur-cation diagram in relation to mean annual rainfall and fire frequency. We delineated domains of monostability (forest, grassland, savanna), of bistability (e.g. forest-grassland or forest-savanna) and even tristability. Notably, we highlighted regions in which two savanna equilibria may be jointly stable (possibly in addition to forest or grassland). We verified that common knowledge about decreasing woody biomass with increasing fire frequency is recovered for all levels of rainfall, contrary to previous attempts using analogous ODE frameworks. Thus, this framework appears able to render more realistic and diversified outcomes than often thought of. Our model can help figure out the ongoing dynamics of savanna vegetation in large territories for which local data are sparse or absent. To explore the bifurcation diagram with different combinations of the model parameters, we have developed a user-friendly R-Shiny application freely available at : https://gitlab.com/cirad-apps/tree-grass.
