Abstract：
In recent decades, die-off events in Pinus sylvestris populations have increased. The causes of these phenomena, which are usually related to local and regional extreme hot droughts, have been extensively investigated from a physiological viewpoint. However, the consequences of die-off process in terms of demography and vegetation dynamics have been less thoroughly addressed. Here, we projected P. sylvestris plot dynamics after a die-off event, under climate change scenarios, considering also their early demographic stages (i.e., seedlings, saplings and ingrowth from the sapling to adult class), to assess the resilience of P. sylvestris populations after such events. We used Integral Projection Models (IPMs) to project future plot structure under current climate, and under RCP4.5 and RCP8.0 climate scenarios, using climatic suitability - extracted from Species Distribution Models - as a covariable in the estimations of vital rates over time. Field data feeding IPMs were obtained from two successive surveys, at the end of the die-off event (2013) and four years later (2017), undertaken on populations situated across the P. sylvestris range of distribution in Catalonia (NE Spain). Plots affected by die-off experienced a loss of large trees, which causes that basal area, tree diameter and tree density will remain lower for decades relative to unaffected plots. After the event, this situation is partially counterbalanced in affected plots by a greater increase in basal area and seedling recruitment into tree stage, thus promoting resilience. However, resilience is delayed under the climate-change scenarios with warmer and drier conditions involving additional physiological stress, due to a reduced abundance of seedlings and a smaller plot basal area. The study shows lagged effect of drought-induced die-off events on forest structure, also revealing stabilizing mechanisms, such as recruitment and tree growth release, which enhance resilience. However, these mechanisms would be jeopardized by oncoming regional warming.
摘要：
近几十年来,樟子松种群的死亡事件有所增加。这些现象产生的原因,这通常与当地和地区的极端干旱有关，从生理角度进行了广泛的研究。然而,死亡过程在人口统计学和植被动态方面的后果尚未得到彻底解决。这里,我们预测了P.sylvestris在死亡事件后的图动态，在气候变化情景下，还考虑到他们的早期人口阶段(即，幼苗,树苗和从树苗到成虫类的向内生长)，评估此类事件后樟子松种群的恢复力。我们使用积分投影模型(IPM)来预测当前气候下的未来地块结构，在RCP4.5和RCP8.0气候情景下，使用气候适宜性-从物种分布模型中提取-作为随时间变化的生命率估计的协变量。从两次连续的调查中获得了输入IPM的现场数据，在死亡事件结束(2013年)和四年后(2017年)，对位于加泰罗尼亚（西班牙东北部）樟子树分布范围内的种群进行了研究。受死亡影响的地块经历了大树的损失，这导致了基底区域，相对于未受影响的地块，树木直径和树木密度将在几十年内保持较低。活动结束后,这种情况在受影响的地块中部分抵消了基础面积的更大增加和幼苗进入树木阶段的增加，从而促进韧性。然而,在气候变化情景下，由于温暖和干燥的条件涉及额外的生理压力，恢复能力会延迟，由于幼苗数量减少和地块基底面积较小。研究表明，干旱导致的死亡事件对森林结构的滞后效应，还揭示了稳定机制，如招募和树木生长释放，增强韧性。然而,这些机制将受到即将来临的区域变暖的危害。
