Data from: Form–function relationships in a marine foundation species depend on scale: a shoot to global perspective from a distributed ecological experiment

Form-function relationships in plants underlie their ecosystem roles in supporting higher trophic levels through primary production, detrital pathways, and habitat provision. For widespread, phenotypically-variable plants, productivity may differ not only across abiotic conditions, but also from distinct morphological or demographic traits. A single foundation species, eelgrass (Zostera marina), typically dominates north temperate seagrass meadows, which we studied across 14 sites spanning 32-61° N latitude and two ocean basins. Body size varied by nearly two orders of magnitude through this range, and was largest at mid-latitudes and in the Pacific Ocean. At the global scale, neither latitude, site-level environmental conditions, nor body size helped predict productivity (relative growth rate 1-2% d-1 at most sites), suggesting a remarkable capacity of Z. marina to achieve similar productivity in summer. Furthermore, among a suite of stressors applied within sites, only ambient leaf damage reduced productivity; grazer reduction and nutrient addition had no effect on eelgrass size or growth. Scale-dependence was evident in different allometric relationships within and across sites for productivity and for modules (leaf count) relative to size. Z. marina provides a range of ecosystem functions related to both body size (habitat provision, water flow) and growth rates (food, carbon dynamics). Our observed decoupling of body size and maximum production suggests that geographic variation in these ecosystem functions may be independent, with a future need to resolve how local adaptation or plasticity of body size might actually enable more consistent peak productivity across disparate environmental conditions.

植物的形态-功能关系是其通过初级生产、碎屑通路以及栖息地提供来支撑更高营养级的生态系统功能的核心基础。对于分布广泛、表型变异丰富的植物而言，其生产力不仅会随非生物环境条件发生变化，还会因独特的形态或种群统计特征产生差异。单一建群种鳗草（Zostera marina）通常是北温带海草床的优势物种，本研究针对该物种开展了横跨北纬32°至61°、覆盖两大洋盆的14个样地的调查。该研究范围内的植株体尺寸变异幅度近两个数量级，且在中纬度海域与太平洋海域中体型达到最大。全球尺度下，纬度、样地级环境条件以及植株体型均无法有效预测其生产力（多数样地的相对生长率为每日1%~2%），这表明大叶藻在夏季维持相似生产力的能力极为突出。此外，在样地内施加的一系列胁迫因子实验中，仅自然存在的叶片损伤会降低其生产力；移除植食者与添加养分均未对鳗草的体型或生长产生显著影响。尺度依赖性在生产力、构件（叶片数量）与体型的异速关系中体现明显：样地内与跨样地的异速关系存在显著差异。大叶藻的生态系统功能涵盖两类：与体型相关的栖息地提供、水流调节，以及与生长速率相关的食物供给与碳循环动态。本研究观测到的体型与最大生产力的解耦现象表明，这些生态系统功能的地理变异可能相互独立，未来仍需阐明体型的本地适应或表型可塑性如何在各异的环境条件下实现更为稳定的峰值生产力。