Lyford Mapped Tree Plot at Harvard Forest since 1969

Permanent forest plots provide an empirical understanding of forest change over time, and are an invaluable part of forestry and ecological research. Walter Lyford began measurements of a 2.88 ha red oak-red maple forest on the Prospect Hill Tract of Harvard Forest in 1969. All trees over 2 inches (5 cm) were mapped on very large-scale (1 inch = 5 feet) hand-drawn maps, and included live and dead trees, stumps, windthrows and other features such as stone walls, boulders, soil moisture and a damage boundary from the 1938 hurricane. All living and dead trees have been re-located and measured (diameter at breast height, canopy class for live trees; condition, decay class, diameter, bole length and stem orientation for fallen dead trees) in 1969, 1975, 1987-1992, 2001, and 2011. In 2001, the original, hand-drawn maps were digitized using ArcView GIS. From 1969 to 2011, red oak (Quercus rubra) increased its dominance of 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%. While red oak and red maple continue to account for the majority of the basal area in the stand, the secondary 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 comprising 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.