School of Biosciences, The University of Melbourne, Parkville, Victoria, Australia.
School of Biosciences, The University of Melbourne, Parkville, Victoria, Australia.
Environ Pollut. 2022 Oct 1;310:119803. doi: 10.1016/j.envpol.2022.119803. Epub 2022 Jul 20.
Artificial light at night (ALAN) is a recognised disruptor of biological function and ecological communities. Despite increasing research effort, we know little regarding the effect of ALAN on woody plants, including trees, or its indirect effects on their colonising invertebrates. These effects have the potential to disrupt woodland food webs by decreasing the productivity of invertebrates and their secretions, including honeydew and lerps, with cascading effects on other fauna. Here, we cultivated juvenile river red gums (Eucalyptus camaldulensis) for 40 weeks under experimentally manipulated light (ALAN) or naturally dark (control) conditions. To assess direct impacts on tree growth, we took multiple measures of growth at four time periods, and also measured physiological function, biomass and investment in semi-mature trees. To assess experimentally the direct and indirect (tree-mediated) impacts of ALAN on invertebrates, from 19 weeks onwards, we matched and mismatched trees with their original ALAN environments. We colonised trees with a common herbivore of E. camaldulensis, the red gum lerp psyllid (Glycaspis nr. brimblecombei) and then measured the effects of current and historic tree lighting treatment on the psyllid life cycle. Our data revealed direct effects of ALAN on tree morphology: E. camaldulensis trees exposed to ALAN shifted biomass allocation away from roots and into leaves and increased specific leaf area. However, while the intensity of ALAN was sufficient to promote photosynthesis (net carbon gain) at night, this did not translate into variation in tree water status or photosystem adaptation to dim night-time light for ALAN-exposed trees. We found some evidence that ALAN had broad-scale community effects-psyllid nymphs colonising ALAN trees produced more lerps-but we found no other direct or indirect impacts of ALAN on the psyllid life cycle. Our results suggest that trees exposed to ALAN may share morphological responses with trees under dim daylight conditions. Further, ALAN may have significant 'bottom-up' effects on Eucalyptus woodland food webs through both trees and herbivores, which may impact higher trophic levels including woodland birds, mammals and invertebrates.
人造光夜间（ALAN）是生物功能和生态群落的公认干扰因素。尽管研究工作不断增加，但我们对 ALAN 对木本植物（包括树木）的影响及其对其定殖无脊椎动物的间接影响知之甚少。这些影响有可能通过降低无脊椎动物及其分泌物（包括蜜露和 lerps）的生产力，从而对其他动物群产生级联效应，从而破坏林地食物网。在这里，我们在实验操纵的光（ALAN）或自然黑暗（对照）条件下培养了 40 周的幼年河红胶（Eucalyptus camaldulensis）。为了评估对树木生长的直接影响，我们在四个时间段内对生长进行了多次测量，还测量了生理功能、生物量和半成熟树木的投资。为了评估 ALAN 对无脊椎动物的直接和间接（树木介导）影响，从 19 周开始，我们将树木与原始 ALAN 环境相匹配和不匹配。我们用 E. camaldulensis 的常见草食动物，红胶 lerp 叶蝉（Glycaspis nr. brimblecombei）殖民树木，然后测量当前和历史树木照明处理对叶蝉生命周期的影响。我们的数据显示了 ALAN 对树木形态的直接影响：暴露于 ALAN 的 E. camaldulensis 树木将生物量分配从根部转移到叶子上，并增加了比叶面积。然而，尽管 ALAN 的强度足以促进光合作用（净碳增益）在夜间，这并没有转化为树木水分状况的变化或对夜间暗光的光系统适应。我们发现一些证据表明 ALAN 具有广泛的群落效应-在 ALAN 树上定殖的叶蝉若虫产生了更多的 lerps-但我们没有发现 ALAN 对叶蝉生命周期的其他直接或间接影响。我们的结果表明，暴露于 ALAN 的树木可能与在昏暗日光条件下的树木具有相似的形态反应。此外，ALAN 可能通过树木和草食动物对桉树林地食物网产生重大的“自下而上”影响，这可能会影响包括林地鸟类、哺乳动物和无脊椎动物在内的更高营养级别的动物。
