Relative Effects of Functional Diversity and Structural Complexity on Late-successional, Northeastern Hardwood Forest Carbon

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Tags: Carbon  

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This was presented by Samantha Myers as a part of a series of contributed talks from the 2022 FEMC Annual Conference. To learn more about the conference, visit: https://www.uvm.edu/femc/cooperative/conference/2022. Understanding forest stand conditions that support high levels of carbon storage and sequestration is of critical importance given increasing regional interest in forest carbon management. While numerous carbon management approaches exist, there is limited stand-level guidance to support such management. Instead, traditional measures of species diversity and structural complexity are used as indicators of a forest ecosystem's capacity to store and sequester carbon. Though these traditional measures of diversity are relatively simple to measure, the diversity of species functional traits may provide valuable information on forest productivity and ecosystem resilience over time. To better understand the role of functional diversity on forest carbon dynamics, we paired existing continuous forest inventory (CFI) data from Massachusetts Department of Conservation and Recreation with local functional trait observations (leaf nutrient content, specific leaf area, and wood density) from trees bordering CFI plots within late-successional forests in western Massachusetts. We applied a Bayesian hierarchical model to quantify the relative effects of functional, species, and structural diversity on live aboveground carbon. Our model importantly synthesized local functional trait information with existing species-level mean trait values applying a multivariate structure that accounts for inherent trait syndromes. Across 323 plot-year combinations, we found that structural complexity, functional diversity, and total basal area explained most of the variability in live aboveground carbon (R2= 0.91 [0.90, 0.93]). Replacing functional diversity with species diversity explained slightly less variability (R2=0.89 [0.87, 0.91]). Contrary to expectations, we found that functional diversity had a negative relationship with live aboveground carbon, possibly due to functional redundancy of dominant late-successional species in high-carbon plots. Study results will inform adaptive forest carbon management by synthesizing new understanding of the relative contributions of forest structure and functional diversity to long-term carbon storage in late-successional hardwood forests in the northeastern U.S.