Prescribed burning applied after a dry year increased (fall burns) or had no effect (spring burns) on pine resilience, measured as the capacity to reach pre-drought growth levels compared with unburned pines. In fall burns, there was a larger increase in resilience when the impact of drought and burning on pines was low and burning caused a significant release from tree competition. Prescribed burning after a dry year can decrease a tree’s resistance (inverse of growth reduction during disturbance); however, burning can increase resource availability and consequently tree resilience (capacity to reach pre-disturbance growth levels). In addition, the burning season can affect the latewood to earlywood ratio (latewood:earlywood) and thus have an impact on tree-ring density. To study the effects of two consecutive disturbances (drought and burning) on Pinus nigra spp. salzmannii and Pinus sylvestris in terms of (i) total tree-ring resistance, (ii) total tree-ring, earlywood and latewood resilience, and (iii) post-stress latewood:earlywood. We selected drought-affected trees (control) and drought-and-burning-affected trees (burned) for tree-ring sampling. For each tree, we measured total tree-ring, earlywood, and latewood widths to determine resilience and resistance indices and calculated pre- and post-stress latewood:earlywood as indicators of tree-ring density. We used linear mixed-effects models to relate these response variables to the pine species, burning characteristics, and competition release. Resistance was higher in control trees than burned trees. P. nigra showed lower resistance than P. sylvestris but higher resilience. Resistance positively influenced resilience. Specifically, as resistance increased, total tree-ring and latewood resilience increased significantly in pines burned during the fall compared with those burned in spring or control pines. In fall burns, the pines’ resilience increased, especially when pines were significantly released from tree competition. In P. nigra, post-stress latewood:earlywood increased after fall burns as pre-stress latewood:earlywood decreased. Prescribed burning can be a valuable management tool for overcoming the effects of a dry year on tree growth by increasing resilience, especially in P. nigra.

中文翻译：

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规定燃烧对黑松抗旱能力的影响。Salzmannii Dunal (Franco) 和 P. sylvestris L.

干旱一年后进行的指定燃烧对松树的弹性增加（秋季燃烧）或没有影响（春季燃烧），衡量标准是与未燃烧的松树相比达到干旱前生长水平的能力。在秋季烧伤中，当干旱和燃烧对松树的影响较低并且燃烧导致树木竞争显着释放时，复原力的增加幅度更大。干旱一年后规定的燃烧会降低树木的抵抗力（与干扰期间的生长减少相反）；然而，燃烧可以增加资源可用性，从而增加树木的恢复力（达到干扰前生长水平的能力）。此外，燃烧季节会影响晚材与早材的比例（晚材：早材），从而对树轮密度产生影响。研究连续两次干扰（干旱和燃烧）对黑松的影响。salzmannii 和 Pinus sylvestris 在 (i) 总树轮抗性，(ii) 总树轮、早材和晚材弹性，以及 (iii) 后应力晚材：早材方面。我们选择了受干旱影响的树木（对照）和受干旱和燃烧影响的树木（燃烧）进行树轮采样。对于每棵树，我们测量了总年轮、早材和晚材宽度，以确定弹性和抗性指数，并计算受压前和受压后的晚材：早材作为年轮密度的指标。我们使用线性混合效应模型将这些响应变量与松树种类、燃烧特性和竞争释放相关联。对照树木的抗性高于被烧毁的树木。P. nigra 的抗性低于 P. sylvestris 但韧性更高。抵抗力对恢复力产生积极影响。具体而言，随着抵抗力的增加，与春季或对照松木燃烧的松树相比，秋季燃烧的松树的总树轮和晚材弹性显着增加。在秋季烧伤中，松树的恢复力增加，特别是当松树从树木竞争中显着释放时。在 P. nigra 中，随着预应力晚材：早材的减少，后应力晚材：早材在秋季烧伤后增加。规定的燃烧可以成为一种有价值的管理工具，通过增加恢复力来克服干旱年份对树木生长的影响，尤其是在黑松中。与春季或对照松木燃烧的松树相比，秋季燃烧的松树的总年轮和晚材弹性显着增加。在秋季烧伤中，松树的恢复力增加，特别是当松树从树木竞争中显着释放时。在 P. nigra 中，随着预应力晚材：早材的减少，后应力晚材：早材在秋季烧伤后增加。规定的燃烧可以成为一种有价值的管理工具，通过增加恢复力来克服干旱年份对树木生长的影响，尤其是在黑松中。与在春季或对照松树中燃烧的松树相比，秋季燃烧的松树的总年轮和晚材弹性显着增加。在秋季烧伤中，松树的恢复力增加，特别是当松树从树木竞争中显着释放时。在 P. nigra 中，随着预应力晚材：早材的减少，后应力晚材：早材在秋季烧伤后增加。规定的燃烧可以成为一种有价值的管理工具，通过增加恢复力来克服干旱年份对树木生长的影响，尤其是在黑松中。