Strategies for forest resilience in the face of environmental change

Project Overview

Forests in flux: strategies for resilience in the face of environmental change

Our objective was to understand the influence of retaining treetops and branches in forests after a partial harvest, and to develop straightforward, effective, and practical solutions for forestland owners and managers to maintain forest health, enhance species diversity above and below ground, and foster growth and productivity. We recommend that treetop material be retained on the ground during and after a partial tree harvest, to benefit pollinators, soil-dwelling arthropods, and overall forest regeneration.

Forestry-related businesses in the Northeast support 1.5 million jobs and generate more than $12 billion per year. Regional forests are highly valued for income and for many other ecosystem services, including beauty, nature, privacy, and as an inter-generational resource.  However, Northeastern forests are threatened by climate change, which is bringing higher temperatures, greater diversity and survival of pests and diseases over winter, and introduction of harmful invasive species. 

The primary focus of this research was understanding the influence of retaining treetops and branches in forests after a partial harvest. We investigated the impact of such retention on tree seedling establishment and subsequent growth, on woodland insect pollinators and on soil invertebrate communities. We identified and measured more than 500 tree seedlings and saplings of many species in Cornell University forests in the vicinity of Ithaca, NY. All trees selected had germinated after a prior forest thinning and were either surrounded by piles of woody material from treetops and branches, or were in nearby plots devoid of wood on the forest floor. In subsequent years, we re-measured 175 of those tagged trees to compare size, survival, and growth rates. We also observed and collected insects in a forest site that was moderately thinned 12 years previously and a forest site that was heavily thinned seven years before. In addition, we collected and analyzed soil cores at five forested stands and compared the species diversity and abundance of soil-dwelling invertebrates in large treatment plots where all treetop material was removed, and plots where moderate-sized and large-sized treetop material was retained.

The Impacts

We found that retaining treetops and branch material during a harvest increases tree species diversity and community composition, enhances growth of several desirable species, and may influence tree survival and health. Overall, our evidence showed that retention of woody material after a harvest of the sawlogs leads to reduced deer browsing and enhanced forest regeneration. We also found higher numbers of pollinating insects in forests near piles of woody materials than in nearby open sites. Further, soil-dwelling invertebrates were greater in number and diversity in plots with treetop material, as compared to areas where treetops were removed.

Headshot of Stephen Morreale with leaves background

Principal Investigator

Project Details

  • Funding Source: McIntire-Stennis
  • Statement Year: 2023
  • Status: Completed project
  • Topics: Forests, biodiversity, ecosystem health, climate change, sustainability