Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Jaén, Spain.
Estación Experimental de Zonas Áridas, EEZA-CSIC, Almería, Spain.
Plant Biol (Stuttg). 2018 Nov;20(6):1083-1092. doi: 10.1111/plb.12870. Epub 2018 Jul 19.
Global change drivers are currently affecting semiarid ecosystems. Because these ecosystems differ from others in biotic and abiotic filters, cues for plant regeneration and management derived from elsewhere may not be applicable to semiarid ecosystems. We sought to determine the extent to which regional variation in regeneration prospects of a long-lived semiarid keystone shrub depends on anthropogenic habitat degradation, plant-animal interactions and climate determinants. We investigated the regeneration ability (via population size structure, juvenile density and juvenile/adult ratio), fruit set and seed dispersal of Ziziphus lotus in 25 localities spanning the range of its threatened habitats in Spain. We dissected the relative contribution of different regeneration determinants using multiple regression and structural equation modelling. Population regeneration was extremely poor, and size structures were biased towards large classes and low juvenile densities and juvenile/adult ratios. Poor regeneration was often coincident with seed dispersal collapse. However, the positive effect of seed dispersal on population regeneration disappeared after considering its relationship with habitat degradation. Protected areas did have juveniles. Together, these data suggest that habitat degradation directly impacts juvenile establishment. Our results provide insights into habitat and species management at the regional level. Z. lotus populations are currently driven by persistence-based dynamics through the longevity of the species. Nonetheless, collapsed seed dispersal, poor regeneration and the removal of adults from their habitats forecast extinction of Z. lotus in many remnants. The extreme longevity of Z. lotus provides opportunities for recovery of its populations and habitats through effective enforcement of regulations.
全球变化驱动因素正在影响半干旱生态系统。由于这些生态系统在生物和非生物过滤器方面与其他生态系统不同，因此其他地方衍生的植物再生和管理线索可能不适用于半干旱生态系统。我们试图确定长期存在的半干旱关键灌木的再生前景的区域变化在多大程度上取决于人为生境退化、动植物相互作用和气候决定因素。我们调查了西班牙受威胁栖息地范围内 25 个地点的枣(Ziziphus lotus)的再生能力（通过种群大小结构、幼树密度和幼树/成年比）、结实率和种子散布。我们使用多元回归和结构方程模型分析了不同再生决定因素的相对贡献。种群再生能力极差，大小结构偏向大类别和低幼树密度和幼树/成年比。再生不良通常与种子散布崩溃同时发生。然而，在考虑到种子散布与生境退化的关系后，种子散布对种群再生的积极影响消失了。保护区确实有幼树。这些数据表明，生境退化直接影响幼树的建立。我们的研究结果为区域水平的生境和物种管理提供了新的见解。Z. lotus 种群目前通过物种的长寿维持基于持久性的动态。尽管如此，种子散布崩溃、再生不良以及成年个体从栖息地中移除，预示着 Z. lotus 在许多残余物中灭绝。Z. lotus 的极端长寿为通过有效执行法规来恢复其种群和栖息地提供了机会。
