Forest Response to the Decline of a Dominant Species: Ecosystem to Regional Analyses of the Impact of the Hemlock Woolly Adelgid on Northeastern Forests

Harvard University, Cambridge MA

Investigators

Abstract

The introduction of exotic pathogens and pests to forest ecosystems represents a powerful agent of ecological change that may selectively remove dominant tree species and simultaneously stimulate widespread human disturbance in the form of pre-emptive and salvage logging. Due to the increasing global movement of organisms and materials, the selective decline and elimination of tree species is an increasingly important ecosystem disturbance that warrants intensive study at stand to regional scales. The recent unimpeded infestation of the hemlock woolly adelgid (HWA) across the northeastern U.S. provides an unusual opportunity and critical imperative to examine the ecological consequences of the removal of a keystone tree species, eastern hemlock, on forest composition, structure, and function. HWA is generating widespread mortality and initiating intensive logging of hemlock from North Carolina to Massachusetts and threatens to produce a range-wide decline or elimination of this ecologically, culturally, and economically important species. Specifically, mortality of hemlock stands with sparse understories may lead to a lengthy period of forest ecosystem reorganization resulting in new, distinct forest types and major changes in ecosystem function including disruption of decomposition, nitrogen cycling and nitrate leaching. Broader impacts from this study include: 1) incorporation of new ecological findings into scientific publications, presentations, and public outreach; 2) informing the public and land managers by distributing findings to the HWA working group and other web-based products; 3) integration of data into existing collaborative efforts with regional experts and professionals; and 4) strong educational training in research design, field techniques, and data and laboratory analyses for students in the graduate and Research Experience for Undergraduate (REU) programs at the Harvard Forest.