Context matters: Natural tree mortality can lead to neighbor growth release or suppression
Context matters: Natural tree mortality can lead to neighbor growth release or suppression
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DOI：
10.1016/j.foreco.2022.120735
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发表时间：
2022-12-20
影响因子：
3.7
通讯作者：
Franklin, Jerry F.
中科院分区：
文献类型：
--
作者：
Chin, Alana R. O.;Lambers, Janneke Hille Ris;Franklin, Jerry F.
在竞争抑制树木生长的地方，相邻树木的死亡可以释放幸存的个体，导致生长增加。然而，原始森林是一个复杂的系统，树木在其中以竞争和促进的方式相互作用，这取决于它们的大小、物种和它们生长的广泛生态环境。因此，附近树木的死亡率的增长反应的幅度，甚至方向可能会有所不同，这对我们理解社区和生态系统水平的动态死亡事件的影响。不幸的是，虽然许多研究集中在光的可用性和一般拥挤对树木生长的影响，我们知道相对较少的自然发生的死亡事件对邻近树木的生长的影响。为了解决这个问题，我们使用了40年的数据，从15个永久性的森林监测地块在雷尼尔山古老的森林，比较观察到的预期径向生长的个别树木死亡后，他们最近的邻居。虽然我们发现了一般的生长释放反应的证据，这是不普遍的所有树木，特别是小树表现出生长抑制（而不是释放）以下相邻的树木死亡。除了小尺寸，生长抑制更有可能，如果死亡的邻居是同一个物种，通过地下网络介导的促进作用一致。在林分水平上，最近邻死亡后的平均生长释放最大的低密度林分与大树，海拔和社区组成也发挥了作用。数十年的监测可以揭示在邻近死亡事件发生后，个体树木的生长释放（或抑制）持续了多长时间，以及潜在的反应滞后和物种身份在确定与邻居的相互作用是竞争性还是促进性方面的作用。尽管如此，我们的研究结果表明，虽然成熟的树木有竞争力的影响，他们的较大的邻居，他们也有一个重要的作用，在支持向内生长的小树。更广泛地说，我们表明，个别相邻树之间的相互作用的性质是高度依赖的上下文。
Where competition suppresses tree growth, mortality of adjacent trees can release the surviving individuals, leading to a growth increase. However, primary forests are complicated systems, where trees interact in both competitive and facilitative ways mediated by their size, species, and the broad ecological context in which they grow. Thus, the magnitude and even direction of growth responses to the mortality of nearby trees may vary, which has implications for our understanding of community- and ecosystem-level dynamics following mortality events. Unfortunately, although many studies focus on the impacts of light availability and general crowding on tree growth, we know relatively little about the effects of naturally occurring mortality events on the growth of neighboring trees. To address this issue, we used 40 years of data from 15 permanent forest-monitoring plots in Mt Rainier old-growth forests, comparing observed to expected radial growth of individual trees following the death of their nearest neighbor. Although we found evidence of a general growth-release response, this was not universal among all trees, with small trees in particular exhibiting growth suppression (rather than release) following neighboring tree mortality. In addition to small size, growth-suppression was more likely if the dead neighbor was the same species, consistent with facilitative effects as mediated through belowground networks. At the stand level, the average growth release after nearest neighbor mortality was greatest in low-density stands with large trees, with elevation and community composition also playing a role. Decades more monitoring could reveal how long growth release (or suppression) is sustained by individual trees following neighboring mortality events, as well as potential response lags and the role of species identity in determining whether interactions with neighbors are competitive or facilitative. Nonetheless, our results suggest that although mature trees have competitive effects on their larger neighbors, they also have an important role in supporting the ingrowth of small trees. More broadly, we demonstrate that the nature of interactions between individual neighboring trees is highly context dependent.