Sheffer Efrat, Canham Charles D, Kigel Jaime, Perevolotsky Avi
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey,United States of America.
Cary Institute of Ecosystem Studies, Millbrook, New York, United States of America.
PLoS One. 2014 Feb 28;9(2):e90178. doi: 10.1371/journal.pone.0090178. eCollection 2014.
Afforestation efforts have resulted in extensive plantations of either native or non-native conifers, which in many regions has led to the spread of those conifers into surrounding natural vegetation. This process of species colonization can trigger profound changes in both community dynamics and ecosystem processes. Our study disentangled the complexity of a process of colonization in a heterogeneous landscape into a simple set of rules. We analyzed the factors that control the colonization of natural woodland ecosystems by Pinus halepensis dispersing from plantations in the Mediterranean region of Israel. We developed maximum-likelihood models to explain the densities of P. halepensis colonizing natural woodlands. Our models unravel how P. halepensis colonization is controlled by factors that determine colonization pressure by dispersing seeds and by factors that control resistance to colonization of the natural ecosystems. Our models show that the combination of different seed arrival processes from local, landscape, and regional scales determine pine establishment potential, but the relative importance of each component varied according to seed source distribution. Habitat resistance, determined by abiotic and biotic conditions, was as important as propagule input in determining the density of pine colonization. Thus, despite the fact that pine propagules disperse throughout the landscape, habitat heterogeneity within the natural ecosystems generates significant variation in the actual densities of colonized pine. Our approach provides quantitative measures of how processes at different spatial scales affect the distribution and densities of colonizing species, and a basis for projection of expected distributions. Variation in colonization rates, due to landscape-scale heterogeneity in both colonization pressure and resistance to colonization, can be expected to produce a diversity of new ecosystems. This work provides a template for understanding species colonization processes, especially in light of anthropogenic impacts, and predicting future transformation of natural ecosystems by species invasion.
植树造林活动导致了大量种植本地或非本地针叶树，在许多地区，这使得这些针叶树扩散到周围的自然植被中。物种定殖过程会引发群落动态和生态系统过程的深刻变化。我们的研究将异质景观中定殖过程的复杂性分解为一组简单的规则。我们分析了控制以色列地中海地区人工林中的阿勒颇松扩散至天然林地生态系统定殖的因素。我们开发了最大似然模型来解释阿勒颇松定殖于天然林地的密度。我们的模型揭示了阿勒颇松的定殖是如何由通过种子扩散决定定殖压力的因素以及控制天然生态系统对定殖抗性的因素所控制的。我们的模型表明，来自局部、景观和区域尺度的不同种子到达过程的组合决定了松树的建立潜力，但每个组成部分的相对重要性因种子源分布而异。由非生物和生物条件决定的生境抗性在决定松树定殖密度方面与繁殖体输入同样重要。因此，尽管松树繁殖体在整个景观中扩散，但天然生态系统内的生境异质性导致定殖松树的实际密度产生显著差异。我们的方法提供了不同空间尺度上的过程如何影响定殖物种分布和密度的定量度量，以及预期分布预测的基础。由于定殖压力和对定殖抗性的景观尺度异质性导致的定殖率变化，预计会产生多样的新生态系统。这项工作为理解物种定殖过程提供了一个模板，特别是考虑到人为影响，并预测物种入侵对自然生态系统的未来转变。
