Effects of different intensities of thinning on ground beetles (Coleoptera : Carabidae) in a black spruce plantation

Abstract

Thinning is a silvicultural practice implemented to maximize harvest productivity. However, biodiversity conservation is a growing trend, therefore it is important to understand the short, and long-term effects of thinning on biodiversity. Ground beetles (Carabidae) play an important role as bioindicators of overall forest health. In order for forest managers and policymakers to balance economic growth and sustainability, we must understand how to implement optimal thinning practices. Ground beetles were sampled in replicated (n = 3) 15-year post-mechanical thinning plots ((CC): 100% basal area removal, heavy thin (HT): 45%, light thin (LT): 25%), 62- year-old mature site (controlled (CT)), and an 80-year-old untouched black spruce forest (reference (REF)). A total of 10234 individuals across 21 species were collected. Species richness was highest in reference (REF), and lowest in clearcut (CC). Total catches did not differ statistically among treatments. Heavy thin was found to be within controlled and light thin ordination. This may indicate that ground beetle biodiversity is not negatively affected by heavy thinning. It also illustrates that heavy thinning, light thinning, and controlled intensities share similar community structures. Overall, results conclude that heavy thinning and light thinning show similar recovery patterns, which could indicate that heavy thinning may not negatively impact the long-term recovery of ground beetle assemblages unless denoted as a forest specialist (narrow niche). Although REF and CT share similarities in stand age, there are still major differences in total catches and species composition.