School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou, 341000, China.
Key Laboratory of Geographical Processes and Ecological Security in Changbai Mountains, Ministry of Education, School of Geographical Sciences, Northeast Normal University, Changchun, 130024, China.
Am J Bot. 2024 Nov;111(11):e16427. doi: 10.1002/ajb2.16427. Epub 2024 Oct 21.
The expected concomitant increase in multiple stressors such as herbivory and drought may threaten peatland ecosystems. How Sphagnum, the ecological engineers of peatlands, responds to combined stressors remains largely unexplored. Here we aimed to clarify resource allocations in Sphagnum during concomitant herbivory and drought.
S. magellanicum and S. fuscum were exposed to drought and herbivory together or separately in laboratory experiments and analyzed for growth (biomass production and net photosynthetic rate), defense (phenolics in leachates and phenolics in extraction) and nonstructural carbohydrates (soluble sugar and starch) in relation to untreated controls.
Herbivory and drought had significant interactive effects on Sphagnum growth and defense. In both species, drought without herbivory reduced the phenolics in leachate, but with herbivory increased phenolics, indicating a synergistic effect between herbivory and drought on Sphagnum defense. Both stressors significantly decreased biomass production, with the combined stress having a more negative effect. Interestingly, a growth-defense trade-off was found in the drought treatment of both Sphagnum species, but disappeared in the wet treatment. Conversely, a trade-off between soluble sugars and phenolics was found in the wet but not in the drought treatment, suggesting that soluble sugars may play a role in inducing the defense and hence mask the growth-defense trade-off in peat mosses.
Our results emphasize that predicting the impact of combined stressors on peat moss traits is complex and challenging. Future models should account for the effects of multiple environmental stressors to guide peatland conservation under climate warming.
随着食草和干旱等多种胁迫因素的预期增加，可能会威胁到泥炭地生态系统。然而，泥炭地的生态工程师——藓类植物如何应对这些复合胁迫因素在很大程度上仍未得到探索。本研究旨在阐明在同时受到食草和干旱胁迫时，藓类植物的资源分配情况。
我们在实验室实验中分别或同时将大型真藓（Sphagnum magellanicum）和小丛真藓（S. fuscum）暴露于干旱和食草胁迫下，并对其生长（生物量产生和净光合速率）、防御（渗出物中的酚类物质和提取液中的酚类物质）和非结构性碳水化合物（可溶性糖和淀粉）进行分析，与未经处理的对照进行比较。
食草和干旱对藓类植物的生长和防御有显著的交互作用。在这两个物种中，没有食草的干旱减少了渗出物中的酚类物质，但有食草的干旱增加了酚类物质，表明食草和干旱对藓类植物防御有协同作用。这两种胁迫都显著降低了生物量的产生，而复合胁迫的影响更为负面。有趣的是，在两种藓类植物的干旱处理中都发现了生长-防御权衡，但在湿润处理中则消失了。相反，在湿润处理中发现了可溶性糖和酚类物质之间的权衡，但在干旱处理中则没有，这表明可溶性糖可能在诱导防御方面发挥作用，从而掩盖了泥炭藓中的生长-防御权衡。
我们的研究结果强调，预测复合胁迫对泥炭藓特征的影响是复杂和具有挑战性的。未来的模型应考虑多种环境胁迫的影响，以指导气候变暖下的泥炭地保护。
