Insect infestations and the persistence and functioning of oak-pine mixedwood forests in the mid-Atlantic region, USA

• Published in: PloS one 2022-05, Vol.17 (5), p.e0265955-e0265955
• Main Authors: Clark, Kenneth L, Aoki, Carissa, Ayres, Matthew, Kabrick, John, Gallagher, Michael R
• Format: Article
• Language: English
• Subjects: 20th century; Age; Animals; Beetles; Biology and Life Sciences; Censuses; Coastal plains; Coleoptera; Composition; Coniferous forests; Continuity (mathematics); Damage; Defoliation; Dendroctonus frontalis; Disturbances; Ecological function; Ecology and Environmental Sciences; Ecosystem; Ecosystems; Eddy covariance; Evapotranspiration; Forest composition; Forest damage; Forest ecosystems; Forest productivity; Forest products; Forests; Growing season; Hardwoods; Harvest; Insects; Mortality; Oak; Pine; Pine trees; Pinus; Prescribed fire; Productivity; Quercus; Respiration; Seasonal variations; Trees; Understory; Vegetation
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0265955

Damage from infestations of Lymantria dispar L. in oak-dominated stands and southern pine beetle (Dendroctonus frontalis Zimmermann) in pine-dominated stands have far exceeded impacts of other disturbances in forests of the mid-Atlantic Coastal Plain over the last two decades. We used forest census data collected in undisturbed and insect-impacted stands combined with eddy covariance measurements made pre- and post-disturbance in oak-, mixed and pine-dominated stands to quantify how these infestations altered forest composition, structure and carbon dynamics in the Pinelands National Reserve of southern New Jersey. In oak-dominated stands, multi-year defoliation during L. dispar infestations resulted in > 40% mortality of oak trees and the release of pine saplings and understory vegetation, while tree mortality was minimal in mixed and pine-dominated stands. In pine-dominated stands, southern pine beetle infestations resulted in > 85% mortality of pine trees but had minimal effect on oaks in upland stands or other hardwoods in lowland stands, and only rarely infested pines in hardwood-dominated stands. Because insect-driven disturbances are both delaying and accelerating succession in stands dominated by a single genus but having less effect in mixed-composition stands, long-term disturbance dynamics are favoring the formation and persistence of uneven age oak-pine mixedwood stands. Changes in forest composition may have little impact on forest productivity and evapotranspiration; although seasonal patterns differ, with highest daily rates of net ecosystem production (NEP) during the growing season occurring in an oak-dominated stand and lowest in a pine-dominated stand, integrated annual rates of NEP are similar among oak-, mixed and pine-dominated stands. Our research documents the formation of mixedwood stands as a consequence of insect infestations in the mid-Atlantic region and suggests that managing for mixedwood stands could reduce damage to forest products and provide greater continuity in ecosystem functioning.