Coastal Ecology Lab, National Observation and Research Station for Shanghai Yangtze Estuarine Wetland Ecosystems, MOE Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, 2005 Songhu Road, Shanghai 200438, China.
Coastal Ecology Lab, National Observation and Research Station for Shanghai Yangtze Estuarine Wetland Ecosystems, MOE Key Laboratory for Biodiversity Science and Ecological Engineering, School of Life Sciences, Fudan University, 2005 Songhu Road, Shanghai 200438, China; Shanghai Academy of Landscape Architecture Science and Planning, NO. 899 Longwu Road, Shanghai 200232, China.
Sci Total Environ. 2021 May 15;769:144854. doi: 10.1016/j.scitotenv.2020.144854. Epub 2021 Jan 19.
Restoration has been increasingly adopted to halt trends in coastal wetland loss globally. Existing restoration often assumes that once abiotic stress is relieved, disturbances are prevented, and invasive species are eradicated, coastal wetlands will recover if propagules of native species are supplied either through natural dispersal or planting. Whether other factors including consumers can help explain the often suboptimal performance of existing restoration remains poorly understood. In a series of field experiments in the Yangtze estuary, we examined the relative importance of abiotic stress and crab grazing in regulating the recovery of the native foundation plant species Scirpus mariqueter in salt marsh areas where exotic cordgrass was successfully eradicated. We found that grazing by herbivorous crabs, rather than abiotic stress, was the primary obstacle restricting the recovery of planted Scirpus. This negative effect of crab grazing varied predictably across elevation and was strongest at low elevations where abiotic conditions were positive for Scirpus. These findings highlight that i) measures to control crab grazing are needed to enhance the success of Scirpus restoration, even in areas where abiotic conditions are set to be optimal, and ii) restoration measures purely focused on reducing abiotic stress could be ineffective or suboptimal in field conditions, likely jeopardizing restoration investment and success. Since top-down control of foundation plant species is common in many coastal wetlands and can be especially important in degraded systems where herbivores are abundant, we urge that future coastal wetland restoration assesses for the impacts of grazers and, when present, apply intervention measures.
恢复已越来越多地被采用以阻止全球沿海湿地的丧失趋势。现有的恢复往往假设，一旦消除了非生物胁迫、防止了干扰以及根除了入侵物种，如果提供了本地物种的繁殖体，无论是通过自然扩散还是种植，沿海湿地就会恢复。其他因素，包括消费者，是否有助于解释现有恢复效果往往不佳的原因，这仍然知之甚少。在长江口的一系列野外实验中，我们研究了生物胁迫和蟹类摄食在调节外来互花米草成功根除后的原生基础植物种海三棱藨草在盐沼地区的恢复中的相对重要性。我们发现，食草蟹类的摄食，而不是非生物胁迫，是限制种植海三棱藨草恢复的主要障碍。蟹类摄食的这种负面影响可预测地随海拔高度变化，在对海三棱藨草有利的低海拔地区最为强烈。这些发现强调：i）即使在非生物条件有利于海三棱藨草的地区，也需要采取控制蟹类摄食的措施来提高海三棱藨草恢复的成功率；ii）仅关注减轻非生物胁迫的恢复措施在野外条件下可能无效或效果不佳，这可能危及恢复投资和成功。由于许多沿海湿地中都存在对基础植物物种的自上而下的控制，并且在食草动物丰富的退化系统中尤为重要，因此我们敦促未来的沿海湿地恢复评估食草动物的影响，并在存在食草动物时采取干预措施。
