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Harvard Forest Symposium Abstract 2010
- Title: Regeneration Following Clearcutting of Red Pine Overstory - Year 20
- 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 2009 (year 20) after a five-year hiatus. Species, height class, origin (sprout or seedling) 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) was 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 and the current data are summarized across all 50 plots. 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 2009 remained negligible (<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 15 (2004) continued through 2009 (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, 15,384 stems/ha in 2004 and 10,079 stems/ha in 2009. The relative abundance of the three major tree species on the plots has remained the same since 1996. In 2009, white ash (33.3% of stems vs. 36.7% in 2004) remained the most numerous tree species, followed by red maple (25.5% of stems vs. 28.3% in 2004), and sugar maple (19.6% of stems vs. 13.4% in 2004), with the shade tolerant sugar maple increasing somewhat at the others expense. Black cherry suffered significant mortality, declining from 11.1% of stems in 2004 to just 3.9% in 2009. After declining somewhat in 2004 to 5.7% of stems, red oak increased to 8.3% in 2009; however, the majority of these were still small seedlings.
Overall, the percentage of stems that originated as seedlings rather than sprouts increased to 19.1%, up from 13.4% in 2004. From 1997 through 2001 about 20-25% of the stems counted originated as sprouts. This variation in percent seedlings is probably the result of varying annual seed crops and seedling survival interacting with increasing mortality of suppressed sprouts as the canopy thickens. The majority of these seedlings were red oak (38.5%) and white ash (30.8%), 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 the top three species is: white ash 28.9% (26.3% in 2004); sugar maple 24.3% (22.5% in 2004); and red maple 21.2% (23.6% in 2004). The greatest change again occurred in black cherry, which declined to 5.0% from 8.2% in 2004. Several early successional species, which are represented by only a few large stems, continue to maintain basal area importance: paper birch 10.7% (10.3% in 2004); pin cherry 5.7% (6.7% in 2004); and trembling aspen 3.8% (2.0% in 2004). A single red oak stem represents just 0.4% of the basal area on the plots (0.5% in 2004). We plan to resample again in year 25 (2014).
- Research Category: Large Experiments and Permanent Plot Studies
- Figures: regensumarea2009.pdf
regensumBA2009-corr.pdf
