Cross scale structure, functional redundancy and spatial resilience of a boreal stream network
Abstract: Assessing how ecological functions are distributed within and across temporal and spatial scales is crucial for understanding the relative resilience of ecosystems, and thus how to effectively and efficiently manage them. In this study, we assess spatial cross-scale distribution of functional feeding groups of benthic invertebrates in a headwater stream network across two seasons. We evaluated functional characteristics of the system (based on Shannon diversity, richness, and evenness indexes) and the degree of redundancy within and across spatial scales for individual feeding groups. In addition, we estimated the relative importance of environmental vs. spatial factors for regulating both the distribution of functions (functional composition) and the species that comprise functional groups (functional redundancy) for each spatial scale identified. Measures of functional diversity and within-scale redundancy of functions were similar in both seasons, but cross-scale resilience was higher in autumn under hydrologically more stable conditions, compared to spring. However, both within-scale redundancy and cross-scale redundancy assessed through spatially explicit modelling was generally low, suggesting an apparent low relative spatial resilience of the stream network. This apparent low resilience was partly due to a few species explaining the spatial models. Species contributing to stochastic noise could not be included in our assessment of cross scale reinforcement but may still contribute to increase resilience. Both environmental and spatial factors were important determinants of the scale-specific functional composition and redundancy. This highlights that components of resilience, such as response diversity and adaptive capacity, need to be studied not only as a function of local disturbance regimes, but also in relation to connectivity and the potential for organisms to disperse between sites, which are also important aspects of ecological resilience.
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