Harvard Forest >

Harvard Forest Symposium Abstract 2012

• Title: Forty Years of Forest Measurements in the Lyford Grid Support the Continuation of the Northeastern Carbon Sink
• Primary Author: Katherine Eisen (Amherst College)
• Additional Authors: Audrey Barker Plotkin (Harvard Forest)
• Abstract:

  Previous studies have used atmospheric measurements and forest inventories to demonstrate that northeastern forests act as a carbon sink, but few have examined relationships between forest stand dynamics and carbon uptake. As the longest running permanent plot study at the Harvard Forest, the Lyford Grid serves as an excellent case study for long-term processes occurring in forested ecosystems. The Lyford Grid was established in 1969 by Harvard Forest scientist Walter Lyford, who censused all trees larger than 5 centimeters DBH in the 2.88 hectare continuous plot. All living and dead individuals were subsequently censused in 1975, 1991, 2001, and most recently, in the summer of 2011. Changes in species composition and total forest aboveground biomass in the Lyford Grid were analyzed to determine if stand dynamics impact the forest’s carbon uptake.
  
  
  
  From 1969 to 2011, Red oak (Quercus rubra) increased its dominance in the stand’s total basal area from 52% to 60%. However, red maple (Acer rubrum) has become relatively less abundant, decreasing from 30% to 23% of all individuals. While red oak and red maple continue to account for the majority of the basal area in the stand, a number of other species experienced a dramatic increase in relative abundance of individuals in the stand; yellow birch (Betula alleghaniensis), black birch (Betula lenta), American chestnut (Castanea dentata), American beech (Fagus grandifolia), witch hazel (Hamamelis virginiana), eastern white pine (Pinus strobus), and eastern hemlock (Tsuga canadensis) have increased from comprising 25% of the individuals in the stand in 1969 to 52% in 2011. The total biomass of living individuals is increasing linearly (R2=0.99, p=0.0002), which implies that the stand has not yet experienced an age-induced decrease in biomass accumulation. These results suggest that New England forests may be increasing the region’s carbon sink at a constant rate, largely due to the continued growth of dominant individuals. However, while red oak comprises the largest percentage of the total forest biomass and basal area, it is not prominent in the understory, suggesting the forest composition may change significantly in the future.
  
  

• Research Category: Large Experiments and Permanent Plot Studies