Dipartimento di Ingegneria Agraria e Agronomia del Territorio, University of Naples Federico II, Portici (Na), Italy.
J Theor Biol. 2012 Nov 21;313:153-61. doi: 10.1016/j.jtbi.2012.08.008. Epub 2012 Aug 15.
Ring shaped patches of clonal plants have been reported in different environments, but the mechanisms underlying such pattern formation are still poorly explained. Water depletion in the inner tussocks zone has been proposed as a possible cause, although ring patterns have been also observed in ecosystems without limiting water conditions. In this work, a spatially explicit model is presented in order to investigate the role of negative plant-soil feedback as an additional explanation for ring formation. The model describes the dynamics of the plant biomass in the presence of toxicity produced by the decomposition of accumulated litter in the soil. Our model qualitatively reproduces the emergence of ring patterns of a single clonal plant species during colonisation of a bare substrate. The model admits two homogeneous stationary solutions representing bare soil and uniform vegetation cover which depend only on the ratio between the biomass death and growth rates. Moreover, differently from other plant spatial patterns models, but in agreement with real field observations of vegetation dynamics, we demonstrated that the pattern dynamics always lead to spatially homogeneous vegetation covers without creation of stable Turing patterns. Analytical results show that ring formation is a function of two main components, the plant specific susceptibility to toxic compounds released in the soil by the accumulated litter and the decay rate of these same compounds, depending on environmental conditions. These components act at the same time and their respective intensities can give rise to the different ring structures observed in nature, ranging from slight reductions of biomass in patch centres, to the appearance of marked rings with bare inner zones, as well as the occurrence of ephemeral waves of plant cover. Our results highlight the potential role of plant-soil negative feedback depending on decomposition processes for the development of transient vegetation patterns.
已在不同环境中报道了克隆植物的环形斑块，但这种模式形成的机制仍未得到充分解释。有人提出，内丛簇区的水分枯竭可能是导致这种情况的原因，尽管在没有限制水条件的生态系统中也观察到了环形模式。在这项工作中，提出了一个空间显式模型，以研究负植物-土壤反馈作为环形形成的另一种解释的作用。该模型描述了在土壤中积累的凋落物分解产生的毒性存在的情况下植物生物量的动态。我们的模型定性地再现了单一克隆植物物种在裸基质定殖过程中出现环形模式的过程。该模型有两个均匀稳定解，分别代表裸土和均匀植被覆盖，这两个解仅取决于生物量死亡和生长速率的比值。此外，与其他植物空间模式模型不同，但与植被动态的实际实地观测一致，我们证明了模式动态总是导致没有稳定图灵模式的空间均匀植被覆盖。分析结果表明，环形形成是两个主要成分的函数，这两个成分分别是植物对土壤中由积累的凋落物释放的有毒化合物的特定敏感性，以及这些化合物的衰减率，这取决于环境条件。这两个成分同时起作用，其各自的强度可以导致在自然界中观察到的不同环形结构，从斑块中心生物量的轻微减少到具有裸露内部区域的明显环形的出现，以及植物覆盖的短暂波的出现。我们的结果强调了负植物-土壤反馈取决于分解过程对瞬态植被模式发展的潜在作用。
