Responses of Ground-Dwelling Invertebrates to Gap Formation and Accumulation of Woody Debris from Invasive Species, Wind, and Salvage Logging

Kayla Perry,Daniel Herms

doi:10.3390/f8050174

Abstract

Natural and anthropogenic disturbances alter canopy structure, understory vegetation, amount of woody debris, and the litter and soil layers in forest ecosystems. These environmental changes impact forest communities, including ground-dwelling invertebrates that are key regulators of ecosystem processes. Variation in frequency, intensity, duration, and spatial scale of disturbances affect the magnitude of these environmental changes and how forest communities and ecosystems are impacted over time. We propose conceptual models that describe the dynamic temporal effects of disturbance caused by invasive insects, wind, and salvage logging on canopy gap formation and accumulation of coarse woody debris (CWD), and their impacts on ground-dwelling invertebrate communities. In the context of this framework, predictions are generated and their implications for ground-dwelling invertebrate communities are discussed.

Highlights

Dynamic patterns of effects of canopy gap formation and coarse woody debris (CWD) accumulation may shift the relative importance of these factors over time, altering the impacts on ground-dwelling invertebrate community structure and function
We develop conceptual models of dynamic effects of disturbances caused by invasive insects, wind, and salvage logging on canopy gaps and downed CWD, and their implications for ground-dwelling invertebrate communities (Table 1)
We proposed conceptual models describing temporal relationships in the effect sizes of disturbance from invasive insect-induced tree mortality, wind storms, and salvage logging on canopy gap formation, accumulation of CWD, and soil disturbance, and their effects on ground-dwelling invertebrate communities

Summary

Disturbance in Forest Ecosystems

Disturbances are inherently variable events that generate spatial and temporal heterogeneity in forest ecosystems by altering habitat structure, energy and nutrient flow, and species composition, thereby shaping long-term patterns in community dynamics and ecosystem processes [1,2,3,4]. Outbreaks of invasive insects and strong winds are two disturbances that cause tree mortality in forest ecosystems [3,9,32,33,34,35,36], and affect millions of hectares of forest globally [37] These agents form canopy gaps and alter the amount of CWD on the forest floor, which has the potential to affect populations of ground-dwelling invertebrates. The magnitude of differences on the forest floor environment between a gap and the surrounding undisturbed forest is determined by local (gap size, shape, orientation, structure, and amount of edge) and landscape (gap isolation, number of gaps, and forest structure) characteristics [46,59] Canopy gaps and their associated environmental changes on the forest floor impact the abundance, diversity, and distribution of ground-dwelling invertebrates, including insects and spiders [46,53,60,61,62,63,64]. Dynamic patterns of effects of canopy gap formation and CWD accumulation may shift the relative importance of these factors over time, altering the impacts on ground-dwelling invertebrate community structure and function

Temporal Responses of Forests to Disturbance

Invasive Insects

Conclusions