Bulling Mark T, Solan Martin, Dyson Kirstie E, Hernandez-Milian Gema, Luque Patricia, Pierce Graham J, Raffaelli Dave, Paterson David M, White Piran C L
Environment Department, University of York, Heslington, York, YO10 5DD, UK.
Oecologia. 2008 Dec;158(3):511-20. doi: 10.1007/s00442-008-1160-5. Epub 2008 Oct 3.
Heterogeneity is a well-recognized feature of natural environments, and the spatial distribution and movement of individual species is primarily driven by resource requirements. In laboratory experiments designed to explore how different species drive ecosystem processes, such as nutrient release, habitat heterogeneity is often seen as something which must be rigorously controlled for. Most small experimental systems are therefore spatially homogeneous, and the link between environmental heterogeneity and its effects on the redistribution of individuals and species, and on ecosystem processes, has not been fully explored. In this paper, we used a mesocosm system to investigate the relationship between habitat composition, species movement and sediment nutrient release for each of four functionally contrasting species of marine benthic invertebrate macrofauna. For each species, various habitat configurations were generated by selectively enriching patches of sediment with macroalgae, a natural source of spatial variability in intertidal mudflats. We found that the direction and extent of faunal movement between patches differs with species identity, density and habitat composition. Combinations of these factors lead to concomitant changes in nutrient release, such that habitat composition effects are modified by species identity (in the case of NH4-N) and by species density (in the case of PO4-P). It is clear that failure to accommodate natural patterns of spatial heterogeneity in such studies may result in an incomplete understanding of system behaviour. This will be particularly important for future experiments designed to explore the effects of species richness on ecosystem processes, where the complex interactions reported here for single species may be compounded when species are brought together in multi-species combinations.
异质性是自然环境中一个广为人知的特征，单个物种的空间分布和移动主要由资源需求驱动。在旨在探究不同物种如何驱动生态系统过程（如养分释放）的实验室实验中，栖息地异质性通常被视为必须严格控制的因素。因此，大多数小型实验系统在空间上是均匀的，而环境异质性及其对个体和物种重新分布以及生态系统过程的影响之间的联系尚未得到充分探索。在本文中，我们使用了一个中型生态系统来研究四种功能不同的海洋底栖无脊椎动物大型动物物种的栖息地组成、物种移动和沉积物养分释放之间的关系。对于每个物种，通过用大型藻类选择性富集沉积物斑块来生成各种栖息地配置，大型藻类是潮间带泥滩空间变异性的天然来源。我们发现斑块之间动物移动的方向和程度因物种身份、密度和栖息地组成而异。这些因素的组合导致养分释放随之发生变化，使得栖息地组成效应会因物种身份（对于NH4-N的情况）和物种密度（对于PO4-P 的情况）而改变。很明显，在此类研究中未能考虑自然的空间异质性模式可能导致对系统行为的理解不完整。这对于未来旨在探究物种丰富度对生态系统过程影响的实验尤为重要，如果将本文报道的单物种复杂相互作用扩展到多物种组合中，可能会更加复杂。
