Compound disease and wildfire disturbances alter opportunities for seedling regeneration in resprouter‐dominated forests
Compound disease and wildfire disturbances alter opportunities for seedling regeneration in resprouter‐dominated forests
复制标题
复合病害和野火干扰改变了以再生者为主的森林中幼苗再生的机会
作者：
Allison B. Simler‐Williamson;M. Metz;K. Frangioso;R. Meentemeyer;D. Rizzo
人为改变的干扰制度和不断变化的气候条件会减少种子的供应和合适的微型地点，限制恢复森林系统的幼苗再生。因此，在许多易受干扰的森林中，可以原地持续存在的重新发芽的植物预计将扩大其优势。然而，resprouters也可能受到挑战，不断变化的制度，和机制决定兼性幼苗招聘的resprouting物种，这将决定未来的传播和目前的持久性，这些人口，知之甚少。在resprouter为主的森林沿海加州，野火和新出现的疾病，橡树猝死（SOD）之间的相互作用，改变干扰的严重程度和树木死亡率，这可能会改变森林再生的轨迹。我们研究了这组复合干扰（1）评估种子限制，生物竞争和非生物条件对重新发芽种群幼苗再生的影响;（2）调查疾病-火灾相互作用是否会改变火灾后的幼苗再生，这对未来的疾病动态和森林组成的变化有影响。在一场野火影响了受SOD影响的森林中预先存在的地块网络之后，我们监测了八年多的幼苗丰度和存活率。火灾前和火灾后的数据，我们评估再生动态和干扰的严重程度，生物和非生物变量之间的关系，使用贝叶斯广义线性模型和混合模型。我们的研究结果表明，火后幼苗再生的重新发芽的物种形成对比机制，反映种子限制和竞争性释放。幼苗丰度下降，减少火后存活的成熟，同种茎，而地下生存的重新发芽的基因没有影响。然而，在种子来源坚持，幼苗丰度和生存普遍增加与火灾前的疾病影响的严重程度，这表明减少与成人的竞争可能会提高幼苗招聘在这个resprouter为主的系统。物种的再生反应不同，其相对敏感性SOD和建议成分的变化，这将决定未来的疾病管理和森林恢复行动。这些结果还强调，机制相关的生物竞争，种子的限制，并在成熟的冠层下的幼苗招聘的机会可能会决定可能的变化发生的再发芽性状。这一结果具有广泛的应用，其他系统的影响，人类改变制度，无性持续性可能是一个有益的生活史策略。
Human-altered disturbance regimes and changing climatic conditions can reduce seed availability and suitable microsites, limiting seedling regeneration in recovering forest systems. Thus, resprouting plants, which can persist in situ, are expected to expand in dominance in many disturbance-prone forests. However, resprouters may also be challenged by changing regimes, and the mechanisms determining facultative seedling recruitment by resprouting species, which will determine both the future spread and current persistence of these populations, are poorly understood. In the resprouter-dominated forests of coastal California, interactions between wildfire and an emerging disease, sudden oak death (SOD), alter disturbance severity and tree mortality, which may shift forest regeneration trajectories. We examine this set of compound disturbances to (1) assess the influence of seed limitation, biotic competition, and abiotic conditions on seedling regeneration in resprouting populations; (2) investigate whether disease-fire interactions alter postfire seedling regeneration, which have implications for future disease dynamics and shifts in forest composition. Following a wildfire that impacted a preexisting plot network in SOD-affected forests, we monitored seedling abundances and survival over eight years. With pre- and postfire data, we assessed relationships between regeneration dynamics and disturbance severity, biotic, and abiotic variables, using Bayesian generalized linear models and mixed models. Our results indicate that postfire seedling regeneration by resprouting species was shaped by contrasting mechanisms reflecting seed limitation and competitive release. Seedling abundances declined with decreasing postfire survival of mature, conspecific stems, while belowground survival of resprouting genets had no effect. However, where seed sources persisted, seedling abundances and survival generally increased with the prefire severity of disease impacts, suggesting that decreased competition with adults may enhance seedling recruitment in this resprouter-dominated system. Species’ regeneration responses varied with their relative susceptibility to SOD and suggest compositional shifts, which will determine future disease management and forest restoration actions. These results additionally highlight that mechanisms related to biotic competition, seed limitation, and opportunities for seedling recruitment beneath mature canopies may determine possible shifts in the occurrence of resprouting traits. This result has broad applications to other systems impacted by human-altered regimes where asexual persistence may be predicted to be a beneficial life history strategy.