Recovery of a boreal ground‐beetle (Coleoptera: Carabidae) fauna 15 years after variable retention harvest

Abstract

Retention harvests are preferred over traditional clear‐cuts for sustainable forest management because maintenance and re‐establishment of native forest biodiversity is a priority. However, few studies have examined long‐term responses of biotic assemblages to retention harvest at particular sites. We studied the effects of decreasing initial harvest intensities (clear‐cut, 10%, 20%, 50% and 75% dispersed green‐tree retention) on carabid beetle assemblages relative to assemblage changes in un‐harvested control stands in four successionally ordered cover‐types of boreal mixedwood forest. We also studied temporal effects by comparing assemblages over a 16‐year pre‐ and post‐harvest period, using data collected through monitoring of the EMEND (Ecosystem Management Emulating Natural Disturbance) experiment in NW Alberta, Canada. Retention harvests affected assemblages differently across cover‐types. Assemblages in compartments harvested in the earlier forest successional stages of ‘deciduous’ or ‘deciduous with spruce understorey’ converged towards the pre‐harvest structure of corresponding controls over time. In contrast, beetle assemblages in ‘mixed’ or ‘conifer’ compartments, that represent later successional forest, moved steadily away from their pre‐harvest structures during the first post‐harvest decade. These latter assemblages became strikingly more similar to those under deciduous canopies by 15‐year post‐harvest. Synthesis and applications. Variable retention harvests will promote and maintain biodiversity better than clear‐cutting. Higher retention levels promote faster recovery, but towards fauna typical of early successional forest in all cover‐types. Carabids associated with conifer habitats are less resistant to impact from harvesting than are those from broadleaf deciduous forest. Therefore, conifer‐dominated stands present the most significant management challenge and higher retention levels are required to promote rapid and effective faunal recovery in such late successional stands.

Rapid recovery of boreal rove beetle (Staphylinidae) assemblages 16 years after variable retention harvest

“…Our data further support our second hypothesis in showing that staphylinid assemblages would recover faster in early successional DD stands than in harvested compartments of late successional MX and CD stands, a pattern also evident for carabid assemblages at EMEND (Wu et al 2020). This also supports the previous study that carabid assemblages in boreal aspen‐dominated stands recovered more quickly than in Cordilleran conifer stands because of rapid post‐disturbance growth of aspen that led to faster recovery of interior forest environments typical of DD stands (Spence et al 1996).…”

“…The higher species richness in regenerating areas compared to mature stands matches observations at other sites in Cordilleran and boreal forests (Spence et al 1997, Buddle et al 2006, Pohl et al 2007). Carabids from the same trap samples as for staphylinids at EMEND exhibited similar patterns in species richness (Wu et al 2020); however, spider richness tended to be lowest in clear‐cuts (Pinzon et al 2016).…”

Spatial and temporal variation of epigaeic beetle assemblages (Coleoptera, Carabidae, Staphylinidae) in aspen-dominated mixedwood forests across north-central Alberta

“…Extensive subsequent sampling of carabid assemblages in aspen forests at another locality (EMEND) in the same Subregion, ca. 55-60 km to the northwest of the stands sampled in the present study, did not show unusually low catch or high species richness/ diversity (Wu et al 2020). As both stands sampled near Peace River were separated by only 2.8 km and were situated in an area including recently harvested stands, it seems that local conditions or perhaps some local landscape effects were likely responsible for low catch and high diversity of carabids.…”

“…Thus, some of the unique structure of Peace River carabid assemblages could be simply a statistical artifact of low catch. Nonetheless, absence of S. impunctatus in samples from stands near Peace River seems characteristic for this Subregion as extensive sampling of mature pyrogenic aspen stands elsewhere in this Subregion between 1998 and 2013 yielded very few individuals, and frequently none, in most sample years (Wu et al 2020).…”

Bryophyte Conservation in Managed Boreal Landscapes: Fourteen-Year Impacts of Partial Cuts on Epixylic Bryophytes

“…This has ignited a lot of interest in long-term studies to better understand species recovery after partial cut harvest (Baker et al, 2015;Fedrowitz et al, 2014), as longitudinal studies in permanent plots can provide strong evidence of species recovery (Dynesius, 2015). However, very few long-term partial cut harvest studies have resurveyed species assemblages in the same sites (Halpern et al, 2012;Bartels et al, 2018;Wu et al, 2020). Furthermore, given that the loss of old growth habitat and species is a major conservation concern (Vaillancourt et al, 2009), it is important to examine the ability of partial cut harvest to encourage old growth species assemblages.…”