Estimating species loss of saproxylic insects under scenarios of reduced coarse woody material in eastern boreal forests

Abstract

Abstract. Increased exploitation of forests and residual biomass remaining after harvest has the potential to reduce biodiversity particularly of saproxylic organisms. We compare incidence-based species accumulation curves based on saproxylic flies collected using in situ emergence cages in 2006 and 2007 under two biomass harvesting scenarios. In these scenarios volume-based biomass targets would be achieved by either 1) selective removal of the largest individual pieces of coarse woody material (CWM) or alternatively 2) selective removal of smaller pieces of CWM with preferential retention of larger pieces of CWM with presumably greater conservation value. We then extrapolated a species accumulation curve to estimate thresholds of potential species loss as a function of CWM volume left within a forest stand using binomial mixing. More species would be maintained under the scenario that selectively targets larger individual pieces of CWM because of extremely large species turnover between individual sample logs and little relation between species richness and diameter of CWM. Given these circumstances, the number of individual pieces of CWM present in a stand may be more important in determining species richness than total volume of CWM for flies. When the species accumulation curve was extrapolated to stand-level volumes, species richness began to decline when CWM volumes were reduced below 40 m 3 /ha. We suggest that intensive management strategies aimed at recovering additional woody biomass should not exploit CWM volumes below these thresholds without mitigative measures aimed at replenishing dead wood volumes such as standing retention if maintaining biodiversity is an objective.

Simulating Long-Term Effects of Bioenergy Extraction on Dead Wood Availability at a Landscape Scale in Sweden

“…We can therefore conclude that bioenergy extraction does have significant impacts on the levels of dead wood in the landscape. Since the total levels of dead wood are already well below the suggested threshold of 20 m 3 ha −1 dead wood at which many saproxylic species can maintain viable populations [13,14], any significant decline is bound to be negative for dead wood dependent species. It therefore appears that, in our study region, it is not realistic that any scenario is going to achieve/maintain dead wood levels that are needed for biodiversity conservation without active measures to increase dead wood levels, e.g., by ecological restoration [23,85].…”

Succession of saproxylic beetles associated with decomposition of boreal white spruce logs

“…This is the uncut ‘control’ compartment for ‘G block’ of the EMEND experiment, set out during 1998–1999 to investigate impacts of variable retention harvesting, and it represents the pre‐harvest condition of a much larger (approximately 80 ha) stand. Because the distribution of saproxylic insects is locally patchy among logs (Work & Hibbert, ) and the capacity of the rearing facility was limited, we chose to maximize replication of decay classes from this single forest stand to better understand variation of CWD at the local scale.…”

Peyerimhoffia jaschhoforum (Diptera, Sciaridae), a new deadwood inhabiting species from Canada

“…All specimens were collected using in-situ photoeclectors (Fig. 1b) identical to those described in (Work and Hibbert 2011). Twenty male specimens were also collected from 70 cm log sections taken from a neighboring closed canopy jack pine forest (47.636 -83.243).…”