Document: CRE-3-69-8

The effects of clearcutting and wildfire on ground-dwelling beetles.

CLAYTON, J.C.*

Utah State University, Logan, UT 84322, USA ¹

Abstract:
Timber harvesting is often proposed as a substitute for stand-replacing wildfire; many feel such a controlled disturbance plays a similar ecological role to the natural disturbance of fire. In order to gain more insight into the soundness of this management approach, the ground-dwelling beetle assemblages of recently burned, clearcut, and undisturbed forested plots (controls) near Logan, Utah were sampled between 1995 and 1999 using pitfall traps. Over 170 beetle species from 37 families were included in the study. Plots sampled included three burned plots in years 1-3 post-fire, four clearcuts in years 1-4 post timber harvest, and 10 forest stands dominated by lodgepole pine and subalpine fir. Beetle species richness, abundance, species-dominance curves, and trophic-group structure were all measured. Initial results show that a greater number of beetle species were trapped on burned plots than nearby forested plots. The clearcuts supported a reduced number of both beetle species and individuals when compared with forested plots during the warmest summer months; however, just after snowmelt the opposite was found. In contrast with some previous studies, species-dominance curves from the disturbed plots were not steeper than the undisturbed plots. The curves from clearcut, burned, and control plots all had similar, roughly log-normal shapes; thus, evenness did not differ among plot types. The trophic group structure of all plots differed only slightly from one another. Burned plots supported the highest percentage of herbivorous species (likely due to the quick herbaceous regrowth). In contrast, clearcut plots had the largest percentage of wood boring species, on average, and the lowest percent of herbivorous species (likely due to the very sparse herbaceous regrowth). The relative proportions of detritivores, omnivores, and predators did not differ dramatically among burns, clearcuts, and controls. Cluster analyses showed that burns, clearcuts, and mature forests all supported their own characteristic beetle species assemblage; most interestingly, the species composition from clearcut and burned plots were rather different from one another. I conclude that clearcutting has different short-term effects on the ground-dwelling beetle community from wildfire.

Keywords: fire, clearcut, timber harvest, disturbance, beetle, Coleoptera, species diversity, community ecology

This abstract is being presented at: 10:30 AM in session:
Poster Session #12: Disturbance Ecology.