Whitcraft Christine R, Levin Lisa A
Integrative Oceanography Division, Scripps Institution of Oceanography, La Jolla, California 92093-0218, USA.
Ecology. 2007 Apr;88(4):904-17. doi: 10.1890/05-2074.
Plant cover is a fundamental feature of many coastal marine and terrestrial systems and controls the structure of associated animal communities. Both natural and human-mediated changes in plant cover influence abiotic sediment properties and thus have cascading impacts on the biotic community. Using clipping (structural) and light (shading) manipulations in two salt marsh vegetation zones (one dominated by Spartina foliosa and one by Salicornia virginica), we tested whether these plant species exert influence on abiotic environmental factors and examined the mechanisms by which these changes regulate the biotic community. In an unshaded (plant and shade removal) treatment, marsh soils exhibited harsher physical properties, a microalgal community composition shift toward increased diatom dominance, and altered macrofaunal community composition with lower species richness, a larger proportion of insect larvae, and a smaller proportion of annelids, crustaceans, and oligochaetes compared to shaded (plant removal, shade mimic) and control treatment plots. Overall, the shaded treatment plots were similar to the controls. Plant cover removal also resulted in parallel shifts in microalgal and macrofaunal isotopic signatures of the most dynamic species. This suggests that animal responses are seen mainly among microalgae grazers and may be mediated by plant modification of microalgae. Results of these experiments demonstrate how light reduction by the vascular plant canopy can control salt marsh sediment communities in an arid climate. This research facilitates understanding of sequential consequences of changing salt marsh plant cover associated with climate or sea level change, habitat degradation, marsh restoration, or plant invasion.
植被覆盖是许多沿海海洋和陆地系统的基本特征，它控制着相关动物群落的结构。植被覆盖的自然变化和人为介导的变化都会影响非生物沉积物的性质，从而对生物群落产生连锁反应。我们在两个盐沼植被区（一个以多花米草为主，另一个以弗吉尼亚碱蓬为主）进行了修剪（结构）和光照（遮荫）操作，以测试这些植物物种是否会对非生物环境因素产生影响，并研究这些变化调节生物群落的机制。在无遮荫（去除植物和遮荫）处理中，与有遮荫（去除植物、模拟遮荫）和对照处理地块相比，盐沼土壤表现出更恶劣的物理性质，微藻群落组成向硅藻优势度增加的方向转变，大型动物群落组成发生改变，物种丰富度降低，昆虫幼虫比例增加，环节动物、甲壳类动物和寡毛类动物比例减小。总体而言，有遮荫的处理地块与对照地块相似。去除植被覆盖还导致了最具活力物种的微藻和大型动物同位素特征的平行变化。这表明动物的反应主要出现在微藻食草动物中，可能是由植物对微藻的改变介导的。这些实验结果表明，维管束植物冠层减少光照如何在干旱气候中控制盐沼沉积物群落。这项研究有助于理解与气候或海平面变化、栖息地退化、盐沼恢复或植物入侵相关的盐沼植物覆盖变化的一系列后果。
