Quantifying panarchy of lake systems: implication for resilience and management (Case study)

University essay from Uppsala universitet/Institutionen för geovetenskaper

Abstract: Liming has been used extensively in Sweden, but the management success has been only partial, mostly mitigating the impact of acidification rather than restoring the ecological communities to a self-maintaining pre-acidified state. Rather than a sound restoration tool, liming is a form of command-and-control management that comprises a significant disturbance in the system, which manifests in the form of profound alterations of biophysical settings of lakes. This thesis aims to assess biological responses to liming with a special focus on resilience by looking at the cross-scale interaction aspects of littoral invertebrate communities in limed lakes within the framework of panarchy theory. The thesis is based on multivariate time series modeling (AEM-RDA) to extract hierarchical temporal fluctuations patterns (temporal scales) in littoral invertebrate communities. This analysis tested for the premise of panarchy theory that complex systems are hierarchically structured. Time series analyses were followed by Spearman rank correlation analysis to test another premise of panarchy theory; namely, that “information” (e.g., management interventions) flows between these hierarchical scales. Specifically, Ca:Mg ratios were used as a surrogate of liming, and correlated with each temporal pattern identified by the AEM-RDA. The result showed the distinct temporal scales in littoral invertebrate communities in limed lakes, fitting the premises of panarchy theory and agreeing with previous studies that found hierarchical temporal organizations in other lake communities. The correlation analyses indicated weak cross-scale manifestation of Ca:Mg ratios in the littoral invertebrate communities, suggesting a weak information flow of liming in managed lakes. This “dilution” of management may provide one mechanism that could explain why liming is not effective in creating a self-organizing, resilient system. The results of this study allow shedding further light on liming as a coerced regime (degraded complex systems forced into a state of desired conditions (e.g., ecosystem service provisioning) through constant management). Most research has so far focused on the evaluation of traditional metrics of biodiversity, which have shown that community structure is substantially altered in limed lakes, deviating from those in circumneutral reference lakes and degraded acidified lakes. This thesis, therefore, concludes that integration of traditional ecological approaches and complexity studies may provide complementary insight into the organization of ecosystems and sustainable resource management.

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