Data from: Consumer control as a common driver of coastal vegetation worldwide

Rapid, global anthropogenic alteration of food webs in ecosystems necessitates a better understanding of how consumers regulate natural communities. We provide a global synthesis of consumer control of vegetation in coastal wetlands, where the domineering role of physical factors such as nutrient and salinity, rather than consumers, has been emphasized for decades. Using a dataset of 1748 measures of consumer effects reported in 443 experiments/observations on all continents except the Antarctica, we examine the generality of consumer control in salt marshes and mangroves globally. Our analyses show that salt marsh herbivores, including insects, snails, crabs, waterfowl, small mammals, and livestock, generally and often strongly suppress plant survival, aboveground biomass, and height, while their effects on plant density, belowground biomass, reproduction, and cover are more variable. These effects occur in forbs, grasses, and shrubs, and in both seedlings and adult plants. Herbivores additionally affect plant nutrient stoichiometry, and mediate plant interactions, though their effects on plant diversity are less consistent. Higher trophic levels also affect plants, as predators facilitate plant growth through trophic cascades that suppress grazer abundance and grazing rate. In mangroves, there are also signs of consumer control, though the relatively few studies available have often focused on mangrove propagules and seedlings rather than adults. Our analyses further reveal that the strength of consumer control is regulated by many physical factors. Nutrient, disturbance, and flooding, for example, amplify the negative effects of herbivores. Along latitudinal gradients, increased temperature enhances the negative effects of ectothermic herbivores, but has no effect on those of endothermic herbivores. Consumer control of coastal plants is also apparent across study methodologies: in field and laboratory settings, in observational studies, in consumer exclusion and addition experiments, in natural and transplanted plants, and in experiments of various durations. The role of consumer control in coastal vegetation worldwide highlights the need to better recognize and theoretically conceptualize both top-down and bottom-up forcing and their interactions in coastal wetlands. Improved understanding and conservation of coastal wetlands will only occur if we incorporate what the science has revealed: trophic feedbacks are an important and pervasive determinant of coastal plant communities.

全球范围内快速发生的人类活动对生态系统食物网造成的改变，亟需我们更深入地理解消费者（consumer）如何调控自然群落的动态。本研究针对滨海湿地开展全球尺度的消费者调控植被作用综合分析——数十年来，学界一直强调养分、盐度等物理因素在此类生境中的主导作用，而非消费者的调控功能。我们整合了除南极洲以外所有大洲的443项实验/观测研究中的1748条消费者效应数据，以此检验全球范围内盐沼（salt marshes）与红树林（mangroves）中消费者调控作用的普遍性。分析结果显示，盐沼中的植食动物（涵盖昆虫、螺类、蟹类、水禽、小型哺乳类与家畜）通常会显著抑制植物的存活、地上生物量与株高；而它们对植物密度、地下生物量、繁殖能力以及盖度的影响则更为多变。此类效应可见于阔叶草本、禾本科植物与灌木，同时对幼苗与成株均产生作用。此外，植食动物会影响植物的养分化学计量比，并调控植物间的相互作用；不过它们对植物多样性的影响并不稳定。更高营养级的生物同样会对植物产生影响：捕食者可通过抑制植食动物的种群数量与取食强度的营养级联效应（trophic cascades），促进植物生长。在红树林生态系统中，同样存在消费者调控的迹象，但现有相关研究数量较少，且多聚焦于红树林的繁殖体与幼苗，而非成株。我们的分析进一步揭示，消费者调控作用的强度受多种物理因素调控：例如养分、干扰与淹水条件会强化植食动物的负面效应。在纬度梯度上，气温升高会增强变温植食动物的负面效应，但对恒温植食动物的效应无显著影响。不同研究方法下，消费者对滨海植物的调控作用均表现显著：包括野外与实验室环境、观测研究、消费者排除与添加实验、原生植物与移栽植物，以及不同时长的实验。全球范围内消费者对滨海植被的调控作用，凸显了我们亟需更好地认知滨海湿地中的下行控制（top-down forcing）与上行控制（bottom-up forcing）及其交互作用，并从理论层面予以阐释。只有充分纳入科学研究揭示的结论——营养级反馈（trophic feedbacks）是调控滨海植物群落的重要且普遍的驱动因素，我们才能进一步深化对滨海湿地的认知并开展有效保护。