Frontiers of Biogeography

Predicting the ecological effects of environmental perturbations remains challenging due to complex interactions between species and the environment, which constantly adapt the ecological memory and, thus, the future response of ecosystems. General theoretical frameworks like the Complex Adaptive Systems (CAS) theory might provide a solution. Here I discuss the applicability of the CAS theory for ecosystems by examining its three major principles (interaction, adaptation and scale dependence) for spring fens. For these ecosystems, adaptation of plant communities to historical environmental stressors (acidification) affecting the resilience to subsequent perturbations (climatic extremes) is empirically shown. Alternative stable states in community composition initiated by acidification turned out to be stabilized by abiotic-biotic feedbacks. Furthermore, ecological response of species to temperature showed high cross-scale similarity. I argue that the exceptional environmental character of spring fens qualifies these ecosystems as ideal model systems to test and further develop CAS theory for ecology and biogeography.