Initial census, composition, and spatial patterns within the 35 ha ForestGEO Plot at Harvard Forest

Background/Question/Methods

To investigate the forest dynamics across a larger range of scales in which many processes operate, Harvard Forest (HF) researchers, with assistance from the Center for Tropical Forest Science (CTFS) and the Smithsonian Institute’s Forest Global Earth Observatory (ForestGEO), recently completed an initial census of all woody stems within a 35 ha plot located at the Harvard Forest.  The HF MegaPlot is part of a global array of large-scale plots established by CTFS whose goals are to increase sampling efforts into temperate forests to explore ecosystem processes beyond population dynamics and biodiversity. The geography and size of the HF MegaPlot (500 m x 700 m) is designed to include a continuous, expansive, and varied natural forest landscape. The strategic plot location will yield opportunities for the study of forest dynamics and demography while capturing a large amount of existing NSF funded LTER (Long Term Ecological Research) science infrastructure (e.g. eddy flux towers, gauged sections of a small watershed, existing smaller permanent plots) and a century of observations and studies. The HF MegaPlot will enable an integrated study of ecosystem processes (e.g., biogeochemistry, hydrology, carbon dynamics) and forest dynamics by melding the past with current and future forest research.

Results/Conclusions

The HF MegaPlot has 108,131 live stems ≥ 1cm dbh, representing 77,125 individuals, and an additional 8,095 dead stems > 5 cm dbh.  Fifty-one woody species, including 1 invasive species (Frangula alnus), were recorded in the plot.  Live tree basal area averaged 42.16 m²ha^-1, of which 84% was represented by Tsuga canadensis ( 14.0 m²ha^-1), Quercus rubra ( 9.6 m²ha^-1), Acer rubrum ( 7.2 m²ha^-1) and Pinus strobus (4.4 m²ha^-1) .   Mean live stem density was 2204 ha^-1 and 3 species (T. canadensis,  A. rubrum, and Ilex verticillata) comprised 56% of all stems.  The seven most abundant canopy trees were significantly clumped at a range of scales within the plot.  Overall, 78% of the stems were < 10 cm dbh, and were dominated by shrub species. Species distribution patterns broadly followed topographic features and past land use history of the site. The HF ForestGEO plot is poised for significant change, as the invasive insect Adelges tsugae has recently infested the plot, threatening most T. canadensis stems. The plot data will be compared with other temperate plots worldwide and will integrate well with ongoing NSF-funded LTER (Long Term Ecological Research) and NEON (National Ecological Observation Network) studies.