Bonanomi Giuliano, Bobrovskikh Aleksandr, Cartenì Fabrizio, Mazzoleni Stefano, Giannino Francesco
Department of Agricultural Sciences, University of Naples Federico II, Naples, Italy.
Task Force of Microbiome Studies, University of Naples Federico II, Naples, Italy.
Front Plant Sci. 2023 Jun 27;14:1079975. doi: 10.3389/fpls.2023.1079975. eCollection 2023.
Plant-soil negative feedback (NF) is a well-established phenomenon that, by preventing the dominance of a single species, allows species coexistence and promotes the maintenance of biodiversity. At community scale, localized NF may cause the formation of exclusion zones under adult conspecifics leading to Janzen-Connell (JC) distribution. In this study, we explore the connection between adult density, either conspecifics or heterospecifics, on the probability of occurrence of JC distributions. Using an individual-based modelling approach, we simulated the formation of exclusion zones due to the build-up of NF in proximity of conspecific adult plants and assessed the frequency of JC distribution in relation to conspecifics and heterospecifics density ranging from isolated trees to closed forest stands. We found that JC recruitment distribution is very common in the case of an isolated tree when NF was strong and capable to form an exclusion zone under the parent tree. At very low NF intensity, a prevalence of the decreasing pattern was observed because, under such conditions, the inhibitory effect due to the presence of the mother tree was unable to overcome the clustering effect of the seed dispersal kernel. However, if NF is strong the JC frequency suddenly decreases in stands with a continuous conspecific cover likely as a result of progressive expansion of the exclusion zone surrounding all trees in closed forest stands. Finally, our simulations showed that JC distribution should not be frequent in the case of rare species immersed in a matrix of heterospecific adults. Overall, the model shows that a plant suffering from strong NF in monospecific stands can rarely exhibit a recruitment pattern fitting the JC model. Such counterintuitive results would provide the means to reconcile the well-established NF framework with part the forest ecologists' community that is still skeptical towards the JC model.
Our model highlights the complex interconnection between NF intensity, stand density, and recruitment patterns explaining where and why the JC distribution occurs. Moreover, predicting the occurrence of JC in relation to stand density we clarify the relevance of this ecological phenomenon for future integration in plant community frameworks.
植物 - 土壤负反馈（NF）是一种已被充分证实的现象，它通过阻止单一物种占据主导地位，实现物种共存并促进生物多样性的维持。在群落尺度上，局部负反馈可能导致成年同种植物下形成排斥区，从而产生詹曾 - 康奈尔（JC）分布。在本研究中，我们探讨了成年植物密度（同种或异种）与JC分布发生概率之间的联系。我们采用基于个体的建模方法，模拟了由于同种成年植物附近负反馈的积累而导致的排斥区形成，并评估了与同种和异种密度相关的JC分布频率，密度范围从孤立树木到封闭林分。我们发现，当负反馈强烈且能够在母树下形成排斥区时，JC补充分布在孤立树木的情况下非常常见。在负反馈强度非常低时，观察到下降模式占主导，因为在这种条件下，母树存在所产生的抑制作用无法克服种子传播核的聚集效应。然而，如果负反馈强烈，在具有连续同种覆盖的林分中，JC频率会突然下降，这可能是由于封闭林分中所有树木周围的排斥区逐渐扩大的结果。最后，我们的模拟表明，在异种成年植物矩阵中稀有种的情况下，JC分布不应频繁出现。总体而言，该模型表明，在单种林分中遭受强烈负反馈的植物很少能表现出符合JC模型的补充模式。这种违反直觉的结果将为调和已确立的负反馈框架与仍对JC模型持怀疑态度的部分森林生态学家群体提供方法。
我们的模型突出了负反馈强度、林分密度和补充模式之间的复杂相互联系，解释了JC分布发生的地点和原因。此外，通过预测与林分密度相关的JC分布，我们阐明了这一生态现象对于未来整合到植物群落框架中的相关性。
