OOS 5-8
Embracing variability: environmental dependence and indirect effects in ecological restoration
In heterogeneous landscapes, one can expect a complexity of restoration outcomes. In particular, the effectiveness of management is likely dependent on where it occurs (environmental conditions) and how it indirectly affects other components of the system (community context). Although managers appreciate context-dependency, they rarely can apply this variable landscape view in decision-making because they do not have the quantitative tools to predict the nature of the variability. Here, we demonstrate one approach to improve decision-making for a reserve in Orange County, California USA. We surveyed plant, soil and landscape characteristics of 131 grassland and coastal sage sites that received management involving herbiciding target exotic plant species and native propagule addition. We used path analysis to describe how each of these management approaches directly affected the proximate management targets (targeted exotics and native species, respectively), as well as how interactions with environmental conditions and indirect effects through these proximate targets influenced outcomes.
Results/Conclusions
Management had the intended direct effects: the application of herbicide and propagule additions directly reduced exotics and increased native species, respectively. Surprisingly, we found that these proximate effects occurred largely independently of environmental conditions and that often these proximate effects did not cascade through the community as intended. Specifically, while herbicide did reduce the cover of targeted exotic plant species, this reduction resulted in only slight increases in native species due to the negative effect of non-targeted exotics. We suggest that the quantitative evaluation of the variability in restoration outcome can be part of an adaptive management approach to increase decision-making efficacy in complex managed landscapes.