Potential Impacts of Insect-Induced Harvests in the Mixed Forests of New England

Meghan Graham Maclean,Marla Markowski-Lindsay,Danelle Laflower,Matthew J Duveneck,David R Foster,David A Orwig,Jonathan R Thompson,Jonathan Holt,Mark Borsuk,David B Kittredge,Brett J Butler

doi:10.3390/f11050498

Abstract

Forest insects and pathogens have significant impacts on U.S. forests, annually affecting an area nearly three times that of wildfires and timber harvesting combined. However, coupled with these direct effects of forest insects and pathogens are the indirect impacts through influencing forest management practices, such as harvesting. In an earlier study, we surveyed private woodland owners in the northeastern U.S. and 84% of respondents indicated they intended to harvest in at least one of the presented insect invasion scenarios. This harvest response to insects represents a potentially significant shift in the timing, extent, and species selection of harvesting. Here we used the results from the landowner survey, regional forest inventory data, and characteristics of the emerald ash borer (Species: Agrilus planipennis Fairmaire, 1888) invasion to examine the potential for a rapidly spreading invasive insect to alter harvest regimes and affect regional forest conditions. Our analysis suggests that 25% of the woodland parcels in the Connecticut River Watershed in New England may intend to harvest in response to emerald ash borer. If the emerald ash borer continues to spread at its current rate within the region, and therefore the associated management response occurs in the next decade, this could result in an increase in harvest frequencies, from 2.6% year−1 (historically) to 3.7% year−1 through to approximately 2030. If harvest intensities remain at levels found in remeasured Forest Inventory and Analysis plots, this insect-initiated harvesting would result in the removal of 12%–13% of the total aboveground biomass. Eighty-one percent of the removed biomass would be from species other than ash, creating a forest disturbance that is over twice the magnitude than that created by emerald ash borer alone, with the most valuable co-occurring species most vulnerable to biomass loss.

Highlights

Forest insects and pathogens (FIPs) have significant impacts on U.S forests, each year affecting an area nearly three times the area of all wildfires and timber harvesting combined [1,2]
Parcels in the Connecticut River Watershed did not require knowing specific forest insect invasion characteristics; we found that the likelihood of harvesting in response to a forest insect for each parcel in an agent functional type relied on specific insect characteristics [17] (Appendix B)
We limited our study to family forest owners (FFOs) parcels as they represented the largest block of owners in the region and we wanted to focus our analysis on the complex FFO response to forest insects

Summary

Introduction

Forest insects and pathogens (FIPs) have significant impacts on U.S forests, each year affecting an area nearly three times the area of all wildfires and timber harvesting combined [1,2]. FIPs have significant indirect impacts on forests by altering management practices, often initiating pre-emptive and salvage harvesting [4]. The Northeast has the largest abundance of exotic FIPs in North America and their numbers and impacts are predicted to increase with climate change and unchanged. The impacts of damaging FIPs and FIP-induced harvesting in the mixed forests of the Northeast threaten the status of these forests as a carbon sink and the combined impacts of FIPs and subsequent management responses are increasingly important to understand, despite the inherent challenge of predicting landowner response to FIPs

Methods

Results

Discussion

Conclusion