Data from: Interacting livestock and fire may both threaten and increase viability of a fire-adapted Mediterranean carnivorous plant

1. Quantifying interactive effects of environmental drivers on population dynamics can be critical for a robust analysis of population viability. Fire regimes, among the most widespread disturbances driving population dynamics, are increasingly modified by and interact with human activities. However, viability of fire-adapted species is typically assessed overlooking disturbance interactions, potentially resulting in suboptimal management actions. 2. We investigated whether increasing human disturbances in fire-prone ecosystems may pose a threat or an opportunity to improve population viability, using demographic data of the carnivorous, post-fire recruiting plant Drosophyllum lusitanicum, endemic to heathlands in the southwestern Mediterranean Basin. We built integral projection models and simulated population dynamics under different combinations of two key disturbance types affecting populations: fire and livestock browsing and trampling. We used perturbation analyses to determine potential long-term consequences of maintaining fundamentally different disturbance types. 3. Despite most populations inhabiting browsed habitats, simulations showed a greater extinction risk in populations under high livestock pressure compared with ones under low or moderate pressures. Extinction risk decreased when fire return intervals shortened in populations under low or moderate livestock pressure; however, the opposite pattern emerged in heavily browsed populations, where short intervals between fires increased extinction.
4. Elasticity analyses showed that decreases in viability under frequent disturbance interactions (heavy browsing and frequent fire) may be explained by selection against seed dormancy in populations with frequent browsing and trampling. This may potentially cause populations to collapse when fires kill above-ground plants without populations being able to recover from a seed bank. 5. Synthesis and applications: Incorporating disturbance interactions can result in a different assessment of viability of a fire-adapted species than considering fire regimes alone. In Mediterranean ecosystems, fire management may be more effective when integrating moderate human activities. However, replacing fires by human disturbances, a currently widespread strategy in many fire-prone ecosystems, is not recommended since it may fundamentally alter population dynamics and selection pressures and decrease viability of fire-adapted species.

1. 量化环境驱动因子对种群动态（population dynamics）的交互效应，对于开展可靠的种群生存力（population viability）分析至关重要。作为驱动种群动态最广泛的干扰因子之一，火灾制度（fire regimes）正日益受到人类活动的改造，并与人类活动产生交互作用。然而，当前对火适应物种（fire-adapted species）的生存力评估通常忽略了干扰交互效应，这可能导致管理措施次优。
2. 本研究以分布于地中海盆地西南部石楠灌丛的食肉型火后再生植物露松（*Drosophyllum lusitanicum*）的种群人口统计数据为基础，探究易火生态系统（fire-prone ecosystems）中日益增强的人类干扰究竟会对种群生存力构成威胁，还是带来改善的契机。我们构建了积分投影模型（Integral Projection Model, IPM），并针对两种影响种群的关键干扰类型（火灾与家畜啃食、踩踏）的不同组合模拟种群动态；通过扰动分析（perturbation analyses），明确维持截然不同的干扰类型可能带来的长期种群后果。
3. 尽管多数种群栖息于受家畜啃食的生境，模拟结果显示，相较于低、中度家畜压力下的种群，高家畜压力种群的灭绝风险更高。在低或中度家畜压力的种群中，火灾回归间隔（fire return intervals）缩短会降低灭绝风险；但在重度啃食的种群中则呈现相反模式：火灾间隔越短，灭绝风险越高。
4. 弹性分析（elasticity analyses）结果表明，在高频干扰交互作用（重度啃食+高频火灾）下种群生存力下降，其原因可能是频繁啃食与踩踏的种群中，自然选择对种子休眠（seed dormancy）产生了负向筛选作用。当火灾杀灭地上植株后，种群无法通过种子库（seed bank）完成恢复，进而可能引发种群崩溃。
5. 综合与应用：相较于仅考虑火灾制度的评估，纳入干扰交互效应后，对火适应物种生存力的评估结果会有所不同。在地中海生态系统中，结合适度人类活动开展火管理可能会更具成效。然而，当前许多易火生态系统中普遍采用的"用人为干扰替代火灾"的策略并不可取，因为这可能从根本上改变种群动态与选择压力，进而降低火适应物种的生存力。