Ground-Dwelling Invertebrate Abundance Positively Related to Volume of Logging Residues in the Southern Appalachians, USA

April D Boggs,Dennis W Hazel,Cathryn H Greenberg,D Magdalena Sorger,Clyde E Sorenson,Christopher E Moorman

doi:10.3390/f11111149

Abstract

Invertebrates, especially those dependent on woody debris for a portion of their life cycle, may be greatly impacted by the amount of downed wood retained following timber harvests. To document relationships between invertebrates and logging residues, we sampled invertebrates with pitfall traps placed near or far from woody debris in 10 recently (2013–2015) harvested sites in western North Carolina with varying levels of woody debris retention. We measured the groundcover and microclimate at each trap and estimated site-level woody debris volume. We modeled predictors (e.g., site-level woody debris volume, percent woody debris cover at the trap site, site type) of captures of spiders (Araneae), harvestmen (Opiliones), centipedes/millipedes (Chilopoda/Diplopoda), ground beetles (Carabidae), rove beetles (Staphylinidae), other beetles, ants (Formicidae), grasshoppers (Acrididae/Tetrigidae), crickets (Gryllidae), and cave crickets (Rhaphidophoridae). In addition, we modeled ant occurrence at a finer taxonomic resolution, including red imported fire ants (Solenopsis invicta Buren) and 13 other genera/species. Forest type, whether hardwood or white pine (Pinus strobus L.) overstory preharvest, was a predictor of invertebrate response for 21 of 24 taxonomic analyses. Invertebrate captures or the occurrence probability of ants increased with increasing site-level woody debris volume for 13 of the 24 taxa examined and increased with increasing coarse woody debris (CWD; diameter ≥ 10 cm) cover at the trap level for seven of 24 taxa examined. Our results indicate that woody debris in harvested sites is important for the conservation of a majority of the taxa we studied, which is likely because of the unique microclimate offered near/under woody debris. Stand-scale factors typically were more important predictors of invertebrate response than trap-level cover of woody debris. We recommend implementing sustainability strategies (e.g., Biomass Harvesting Guidelines) to retain woody debris scattered across harvested sites to aid in the conservation of invertebrates.

Highlights

Downed wood is a critical component of forest ecosystems and provides numerous ecological services, such as carbon sequestration [1,2], soil nutrient replenishment [1,2,3], and erosion control [1,4].Forests 2020, 11, 1149; doi:10.3390/f11111149 www.mdpi.com/journal/forestsDowned wood can serve as “nurse logs” for tree seedlings, providing increased survival and/or decreased competition from other plants [5,6,7,8]
We studied relationships between residual downed wood and invertebrates in 10 recent timber harvests, ranging in size from 3.2 to 16.6 ha, which were located on public land in western (Henderson and Transylvania County) North Carolina, USA (Figure 1)
Prior studies showed that downed wood retention either negatively or neutrally impacts red imported fire ants, we showed that red imported fire ants were negatively correlated with downed wood (CWD percent cover) at the trap level and positively correlated with woody debris volume at the site level [38,78]

Summary

Introduction

Downed wood is a critical component of forest ecosystems and provides numerous ecological services, such as carbon sequestration [1,2], soil nutrient replenishment [1,2,3], and erosion control [1,4].Forests 2020, 11, 1149; doi:10.3390/f11111149 www.mdpi.com/journal/forestsDowned wood can serve as “nurse logs” for tree seedlings, providing increased survival and/or decreased competition from other plants [5,6,7,8]. Downed wood provides nesting and escape cover for a variety of wildlife, including small mammals, amphibians, and birds e.g., [13,14,15,16]. Larger diameter downed wood (CWD) provides food for wildlife, either directly for saproxylic invertebrates (taxa directly or indirectly dependent on downed wood for some portion of their life cycle [18,19,20]) or indirectly by providing cover for invertebrates and small mammals that in turn serve as prey. Without dead and dying wood, populations of these valuable invertebrates would decline, along with the ecosystem services (e.g., decomposition) they provide [25,26]

Objectives

Methods

Results

Discussion

Conclusion