This summary of external research relevant to Northeast Wilderness Trust’s (NEWT) conservation work was prepared by the organization’s Wildlands Ecology team. NEWT played no role in the funding, design, or execution of the research summarized here.

Study Title: “High rates of primary production in structurally complex forests”

Authors: Christopher M. Gough, Jeff W. Atkins, Robert T. Fahey, and Brady S. Hardiman

Publication: Ecology

Year Originally Published: 2019

Summary of Findings: This paper was aimed at understanding if canopy structural complexity could predict the net primary production (NPP) across temperate forests. Researchers used light detection and ranging (LiDAR) technology to measure structure, and compared it to more traditional metrics like species diversity and vegetation area index (VAI) to see which metric best explains forest productivity (used in this context to refer to the net production of above-ground wood).

Using mechanistic modeling to test how these different metrics related to NPP, the authors determined that canopy rugosity (a measure of “roughness”) was able to explain 83 percent of site-level variation in NPP, outperforming all other metrics. In other words, the roughness of the canopy is better at predicting the productivity of forests in this biome than any of the more conventional/traditionally used metrics like canopy leaf area, height, arrangement, and cover.

This finding highlights the value of maintaining forest structure to increased productivity, and increased productivity of aboveground wood is also known as carbon storage—meaning more complex forests play an outside role in forest carbon storage.

Outstanding Questions/Caveats:

• It is not clear whether this relationship would hold outside of North American temperate forests.
• This study also found a high degree of statistical overlap between structural complexity and species diversity, but it is not clear if there is causation here, or simply correlation.
• The study authors found canopy roughness/structural complexity to be the best predictor of production of above-ground woody biomass, but most ways the we model climate and carbon are not equipped to use this kind of data, and doing so might be computationally expensive or cost prohibitive.

Application to Northeast Wilderness Trust’s Work: NEWT promotes the development of structurally complex forests through the process of passive rewilding/passive management, meaning no woody biomass will be removed. This allows the forest to develop complexity over time, without the threat of a harvest resetting that clock.  This paper indicates that those structurally complex forests will be more “productive” meaning they will make more wood, and therefore store more carbon than similar forests that are less structurally complex.

Link to the Paper: https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2864