Forest disturbance increased ground beetle species diversity

Theory predicts that species diversity is maximized at intermediate levels of disturbance due to trade-offs in traits for competition and colonization ability.  Carabidae are an ideal group for testing the effects of disturbance on community structure because they are highly responsive to environmental change and their dispersal potential can be characterized based on wing development.  To test the competition – colonization trade-off model, we characterized ground beetle assemblages at three levels of forest disturbance intensity (low, intermediate, and high) at Powdermill Nature Reserve in southwestern Pennsylvania.  We conducted a manipulative experiment with two disturbance treatments applied in factorial combination: presence and absence of canopy gaps and presence and absence of understory vegetation removal.  Ground beetle species composition changed with the disturbance treatments, as highly mobile, flying beetles marginally increased in plots with the presence of canopy gaps and absence of understory vegetation.  Consequently, and contrary to predictions of the competition-colonization trade-off model, ground beetle diversity tended to be highest in the most disturbed plots with canopy gaps and understory vegetation removed, as many forest species were still present.  Changes in species diversity and composition in response to disturbance may affect forest ecosystem services.  Therefore, understanding the effects of disturbance on biodiversity is critical for fostering sustainable forest management.