Thursday, November 7, 2013

Managing uncertain restoration outcomes*

Human activity has impacted ecosystems around the globe, and the value of intact, functioning habitats is increasingly appreciated. One of the most important management options to maintain or increase the amount of functioning habitat is to restore destroyed, disturbed and degraded habitats. However, there is much concern about how predictable restoration efforts are and the management strategies that will maximize success. The reality that systems may reach very different, alternative ecosystem states is a problem for managers when they desire well defined outcomes. Thus the ability to understand and predict how different factors affect restoration outcomes would be an important development.

In the current issue of the Journal of Applied Ecology, Grman and colleagues examine how different factors influence prairie restoration outcomes –specifically the diversity and composition of the restored habitat. They considered several management, historical and environmental factors. For management, they compiled information on the type of planting, the diversity and density of sown seeds and fire manipulation. For local environmental variables, they considered different soil characteristics, shade levels, and site area. The historical influences included land-use history, rainfall during seed sowing and site age. Finally, they also considered the landscape context; specifically what habitats surrounded the restoration site.

Grman and colleagues show that restoration outcomes are most influenced by management decisions and site history. The density, composition and diversity of sown seeds had the greatest impact on restoration outcomes. Species richness was highest in sites sown with high diversity. High sowing density resulted in high beta diversity among sites. Site history had significant effects on non-sown diversity, but did not influence the diversity of sown species. Site characteristics failed to predict local diversity, but they were important for among site beta-diversity.

If success is measured in terms of species diversity, then this work clearly shows that management decisions directly influence success. Surprisingly, site characteristics had a minor influence on success, despite conceptual and theoretical models that predict system sensitivity to abiotic influences. This work reinforces the need to develop the best management options for prairie restoration and that the influences of site history and local conditions can be overcome by sowing decisions and site management.

Grman E., Bassett T. & Brudvig L.A. (2013). Confronting contingency in restoration: management and site history determine outcomes of assembling prairies, but site characteristics and landscape context have little effect. Journal of Applied Ecology, 50, 1234-1243.

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