Resilience to disturbance is a cross-scale phenomenon offering a solution to the disturbance paradox

Abstract

Resilience is the ability of an ecosystem to return to a previous state following disturbance. Ecological communities may demonstrate resilience after long periods of time. However, short-term outcomes of disturbance may be reduced functionality despite an increase in biodiversity, a phenomenon known as the disturbance paradox. Silvicultural management regimes are ecological disturbances that vary with the frequency of tree harvests, the age of the tree when harvested, spatial arrangement of harvest, and the area of forest removed. Therefore, they are expected to result in different levels of resilience among forest communities over time. We used the response of temperate hardwood forest beetle communities to different timber harvest treatments in a long-term research study to test predictions of ecosystem resilience. We also aimed to determine whether this system shows evidence of the disturbance paradox. We predicted that (1) communities following harvest differ from pre-harvest communities, (2) areas treated with even-aged management and uneven-aged management would show community trajectories back to pre-harvest communities, (3) the more concentrated disturbance of the even-aged management would lead to a lower community resilience, and (4) community change would be attributed to an increase in pest species using recently harvested wood. The communities did change after timber harvests, but while the dissimilarity between pre- and post-treatment communities was the same for the two treatments, the departure and return to the pre-harvest community state were along different community trajectories. Furthermore, communities in both treatments showed similar resilience by returning to pre-harvest community composition at the same rate. As predicted, the abundance of species most responsible for post-harvest community shifts were those that feed on living wood. This, along with a decrease in abundance of decaying wood decomposers, indicated that the disturbance paradox was playing out in this system.