Can the resistance and resilience of trees to drought be increased through thinning to adapt forests to climate change?

最近和预测的极端干燥和炎热夏季的增加，强调需要采取造林方法，在可能通过物种变化进行适应之前，在短期内提高现有森林的耐旱性。我们的目标是调查干旱期间的抗性以及干旱事件后的恢复（恢复力）是否可以通过间伐分配更多的生长空间给单个树木来增加。疏伐增加了种植树木获得土壤储水的途径，只要土壤储水是可用的。然而，这些树木也可能由于较高的蒸腾表面或地面植被增加的邻里竞争而处于不利地位。为了评估不同生长空间的树木在抗旱性上是否存在差异，我们将利用来自西尔松和孟氏伪杉树林间伐试验的树盘和树芯来研究先前干旱期间的蒸腾胁迫和生长减少及其随后的恢复。树木生态学和树木年轮中碳和氧的稳定同位素将用于量化通过疏化如何改变同化速率和气孔导度。研究结果将为制定短期造林适应战略以使森林生态系统适应气候变化提供重要信息。此外，本研究将提高我们对极端胁迫事件下树木抗性和恢复力之间关系的理解。

Recent and predicted increases in extremely dry and hot summers emphasise the need for silvicultural approaches to increase the drought tolerance of existing forests in the short-term, before adaptation through species changes may be possible. We aim to investigate whether resistance during droughts, as well as the recovery following drought events (resilience), can be increased by allocating more growing space to individual trees through thinning. Thinning increases access of promoted trees to soil stored water, as long as this is available. However, these trees may also be disadvantaged through a higher transpirational surface, or the increased neighbourhood competition by ground vegetation. To assess whether trees with different growing space differ in drought tolerance, tree discs and cores from thinning experiments of Pinus sylvestris and Pseudotsuga menziesii stands will be used to examine transpirational stress and growth reduction during previous droughts as well as their subsequent recovery. Dendroecology and stable isotopes of carbon and oxygen in tree-rings will be used to quantify how assimilation rate and stomatal conductance were altered through thinning. The results will provide crucial information for the development of short-term silvicultural adaptation strategies to adapt forest ecosystems to climate change. In addition, this study will improve our understanding of the relationship between resistance and resilience of trees in relation to extreme stress events.