Zhang Dongmei, Zhang Liwen, Lan Siqun, Zhao Lianjun, Han Guangxuan, Chen Lin
Tianjin Key Laboratory of Animal and Plant Resistance, College of Life Sciences, Tianjin Normal University, Tianjin, China.
CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Shandong Key Laboratory of Coastal Environmental Processes, YICCAS, Yellow River Delta Field Observation and Research Station of Coastal Wetland Ecosystem, YICCAS, Yantai, China.
Front Plant Sci. 2024 Aug 30;15:1418724. doi: 10.3389/fpls.2024.1418724. eCollection 2024.
Eutrophication resulting from anthropogenic activities has been recognized as a significant driver of changes in ecosystem functioning. Furthermore, it may exacerbate the top-down effect and thus exert an important impact on plant growth. To test this hypothesis, we conducted a 3-year manipulative field experiment to investigate the impacts of nitrogen addition and crab herbivory on the growth of in the salt marsh of the Yellow River Delta. The results demonstrated that a 3-year nitrogen addition can significantly increase the total nitrogen and carbon content of leaves, thereby enhancing their nutritional value and palatability, as well as increasing the proportion of leaves consumed by crabs. Therefore, nitrogen addition together with crab herbivory had a significant negative effect on height, leaf length, and leaf breadth in the ambient crab and procedural crab cage treatment compared to the crab exclusion treatment. The structural equation modeling further substantiated these findings. The model revealed a direct and positive correlation between nitrogen addition and leaf nutrient content (path coefficient = 0.34). Additionally, it demonstrated a direct and positive relationship between leaf nutrient content and the proportion of leaves consumed by crabs (path coefficient = 0.22). Simultaneously, there was an observed negative correlation (path coefficient = - 0.37) between the proportion of leaves consumed by crabs and plant functional traits, represented by leaf length in the model, during 2018. Moreover, the crab exclusion treatment significantly reduced the proportion of leaves consumed by crabs and thus enhanced the individuals, leaf number, and biomass. Overall, crab herbivory had a significant detrimental top-down effect on the growth of , and nitrogen enrichment may exacerbate this top-down effect. The findings of our study highlight the combined adverse effects of nutrient enrichment and top-down on plant functional traits and plant growth. The findings of this study will contribute to a comprehensive understanding of the underlying factors influencing vegetation degradation in coastal wetland, thereby establishing a solid theoretical framework for the conservation and management of wetland ecosystems within the context of global environmental change.
人为活动导致的富营养化已被公认为是生态系统功能变化的一个重要驱动因素。此外，它可能会加剧自上而下的效应，从而对植物生长产生重要影响。为了验证这一假设，我们进行了一项为期3年的控制性田间实验，以研究添加氮和螃蟹啃食对黄河三角洲盐沼中[植物名称未给出]生长的影响。结果表明，连续3年添加氮能显著增加[植物名称未给出]叶片的总氮和碳含量，从而提高其营养价值和适口性，同时也增加了被螃蟹吃掉的叶片比例。因此，与排除螃蟹处理相比，在有螃蟹和设置螃蟹笼的处理中，添加氮与螃蟹啃食共同对[植物名称未给出]的高度、叶长和叶宽产生了显著的负面影响。结构方程模型进一步证实了这些发现。该模型显示添加氮与叶片养分含量之间存在直接的正相关关系（路径系数 = 0.34）。此外，它还表明叶片养分含量与被螃蟹吃掉的叶片比例之间存在直接的正相关关系（路径系数 = 0.22）。同时，在2018年观察到被螃蟹吃掉的叶片比例与以模型中叶长表示的植物功能性状之间存在负相关关系（路径系数 = -0.37）。此外，排除螃蟹处理显著降低了被螃蟹吃掉的叶片比例，从而增加了[植物名称未给出]的个体数量、叶片数量和生物量。总体而言，螃蟹啃食对[植物名称未给出]的生长产生了显著的有害自上而下效应，而氮富集可能会加剧这种自上而下效应。我们的研究结果突出了养分富集和自上而下对植物功能性状和植物生长的综合不利影响。本研究结果将有助于全面了解影响沿海湿地植被退化的潜在因素，从而在全球环境变化背景下为湿地生态系统的保护和管理建立坚实的理论框架。
