Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91, Stockholm, Sweden.
Bolin Centre for Climate Research, Stockholm University, SE-106 91, Stockholm, Sweden.
Ecol Appl. 2023 Jun;33(4):e2851. doi: 10.1002/eap.2851. Epub 2023 Apr 2.
Forest fragmentation increases the amount of edges in the landscape. Differences in wind, radiation, and vegetation structure create edge-to-interior gradients in forest microclimate, and these gradients are likely to be more pronounced during droughts and heatwaves. Although the effects of climate extremes on edge influences have potentially strong and long-lasting impacts on forest understory biodiversity, they are not well understood and are not often considered in management and landscape planning. Here we used a novel method of retrospectively quantifying growth to assess biologically relevant edge influences likely caused by microclimate using Hylocomium splendens, a moss with annual segments. We examined how spatio-temporal variation in drought across 3 years and 46 sites in central Sweden, affected the depth and magnitude of edge influences. We also investigated whether edge effects during drought were influenced by differences in forest structure. Edge effects were almost twice as strong in the drought year compared to the non-drought years, but we did not find clear evidence that they penetrated deeper into the forest in the drought year. Edge influences were also greater in areas that had fewer days with rain during the drought year. Higher levels of forest canopy cover and tree height buffered the magnitude of edge influence in times of drought. Our results demonstrate that edge effects are amplified by drought, suggesting that fragmentation effects are aggravated when droughts become more frequent and severe. Our results suggest that dense edges and buffer zones with high canopy cover can be important ways to mitigate negative drought impacts in forest edges.
森林破碎化增加了景观中的边缘数量。风、辐射和植被结构的差异在森林小气候中形成了边缘到内部的梯度，而在干旱和热浪期间，这些梯度可能更为明显。尽管气候极端事件对边缘影响的潜在影响具有强烈且持久的影响，但对森林林下生物多样性的了解并不充分，在管理和景观规划中也经常不被考虑。在这里，我们使用一种新的回溯生长量化方法，使用具有年度节段的苔藓 Hylocomium splendens 来评估可能由小气候引起的生物相关边缘影响。我们研究了 3 年和瑞典中部 46 个地点的干旱时空变化如何影响边缘影响的深度和幅度。我们还调查了干旱期间的边缘效应是否受到森林结构差异的影响。与非干旱年份相比，干旱年份的边缘效应几乎强了一倍，但我们没有发现明确的证据表明它们在干旱年份更深入地渗透到森林中。在干旱年份，边缘效应在降雨量较少的地区更为强烈。较高的森林冠层覆盖和树木高度在干旱时期缓冲了边缘影响的幅度。我们的结果表明，干旱加剧了边缘效应，表明当干旱变得更加频繁和严重时，破碎化效应会加剧。我们的研究结果表明，密集的边缘和具有高冠层覆盖的缓冲区可以成为减轻森林边缘负面干旱影响的重要途径。
