van Kampen Ruth, Fisichelli Nicholas, Zhang Yong-Jiang, Wason Jay
School of Forest Resources, University of Maine, Orono, ME 04469, USA.
Schoodic Institute at Acadia National Park, Winter Harbor, ME, USA.
AoB Plants. 2022 Mar 18;14(3):plac012. doi: 10.1093/aobpla/plac012. eCollection 2022 Jun.
Droughts interact with tree phenology to drive declines in growth. As climate change makes drought more likely in the Northeastern USA, it is important to understand how droughts at different times of year will lead to reduced height and diameter growth of trees. To determine how seasonal drought may reduce intra-annual growth, we implemented spring, summer or fall droughts on 288 containerized saplings of six tree species (, , , , and ). We tracked weekly soil moisture, leaf water potential, height, diameter and survival of all trees before, during and after each 6-week drought. We found that the tree species that conducted the majority of their height or diameter growth in the spring were most sensitive to spring droughts ( and ). also experienced significantly reduced growth from the spring drought but increased growth after the drought ended and achieved total height and diameter growth similar to controls. In contrast, summer droughts halted growth in most species for the remainder of the growing season even after the drought had ended. Fall droughts never impacted growth in the current year. These fine temporal-scale measurements of height and diameter growth suggest that tree response varies among species and is dynamic at intra-annual scales. These relatively rare data on intra-annual height growth sensitivity are important for canopy recruitment of saplings in forest ecosystems. Species-specific sensitivities of intra-annual growth to drought can inform models of forest competition in a changing climate.
干旱与树木物候相互作用，导致树木生长下降。随着气候变化使美国东北部更易发生干旱，了解一年中不同时间的干旱如何导致树木高度和直径生长减少至关重要。为了确定季节性干旱如何减少年内生长，我们对六种树种（、、、、和）的288株盆栽树苗实施了春季、夏季或秋季干旱处理。我们在每次为期6周的干旱之前、期间和之后，每周跟踪所有树木的土壤湿度、叶水势、高度、直径和存活率。我们发现，在春季进行大部分高度或直径生长的树种对春季干旱最为敏感（和）。也因春季干旱而生长显著减少，但在干旱结束后生长增加，最终达到了与对照相似的总高度和直径生长。相比之下，夏季干旱使大多数树种在生长季节的剩余时间里停止生长，即使在干旱结束后也是如此。秋季干旱从未影响当年的生长。这些对高度和直径生长的精细时间尺度测量表明，不同树种的反应各不相同，并且在年内尺度上是动态变化的。这些关于年内高度生长敏感性的相对罕见的数据，对于森林生态系统中树苗的树冠补充非常重要。不同树种年内生长对干旱的敏感性，可以为气候变化下森林竞争模型提供参考。
