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Harvard Forest Symposium Abstract 2005

  • Title: Regeneration Following Clearcutting of Red Pine Overstory - Year 15
  • Primary Author: John O'Keefe (Harvard Forest)
  • Additional Authors: Pamela Snow (Harvard Forest)
  • Abstract:

    Measurements of regeneration following removal in 1990 of a 64-year old red pine plantation on the Prospect Hill tract were made again in 2004 (year 15) after a two-year hiatus. Species, height, origin and evidence of browsing were recorded for all woody stems on 50 milacre (1.13 m radius) plots established on a five-meter grid within the clearcut. Diameter at breast height (dbh) is recorded for all stems greater than 7 m tall. A fenced exclosure was initially erected around half of the plots. The exclosure fence has not been maintained since year 5 because no evidence of significant differences in regeneration between the exclosure and the open area was found. Extensive mixed hardwood regeneration (generally less than 7 m tall) was cut back to the ground during harvest, ensuring at least initial dominance by sprouts.


    Browsing in 2004 remained at very low levels (<1% of stems). As mean tree height continues to increase both the amount of browsing and the impact of browsing on future stand characteristics should remain very low. Overall, our observations show that browsing has had little long-term impact during the regeneration of this stand. White ash, the most heavily browsed species, remains the most common species in the plots.




    The decline in stem density observed in year 12 (2001) continued through 2004 (Figure 1). After remaining fairly stable at around 20,000 stems/ha from 1996 through 2000, stem density dropped to 17,883 stems/ha in 2001 and 15,384 stems/ha in 2004. The relative abundance of major tree species has remained the same since 1996. In 2004, white ash (36.7% of stems) remained the most numerous tree species, followed by red maple (28.3% of stems), sugar maple (13.4% of stems) and black cherry (11.1% of stems). These percentages changed little from 2001. Red oak decreased from 7.5% of tree stems in 2001 to 5.7% in 2004, the majority of which were small seedlings.


    Overall, the percentage of stems that originated as seedlings rather than sprouts decreased to 13.4%, down from 19.3% in 2001, and about 23-25% from 1997 through 2000. This reduction in seedlings is probably due to the lower light levels reaching the forest floor as the sprouts grow taller with larger crowns. The majority of these seedlings (57.1%) were white ash, most less than .5 m tall.


    Basal area is calculated from dbh for all stems greater than 7 m tall (Figure 2). For these stems the basal area ranking of species generally follows density ranking (white ash 26.3% of the basal area, red maple 23.6%, sugar maple 22.5%, black cherry 8.2%) except that several early successional species (paper birch 10.3% of the basal area, pin cherry 6.7%, trembling aspen 2.0%), which are represented by only a few large stems, are much more strongly represented in basal area. The first red oak stem entered this category in 2004 representing just 0.5% of the basal area on the plots. Our next sampling will be done in year 20.


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