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Harvard Forest Symposium Abstract 2015
- Title: Regeneration Following Clearcutting of Red Pine Overstory - Year 25
- Primary Author: John O'Keefe (Harvard Forest)
- Abstract:
Regeneration Following Clearcutting of Red Pine Overstory - Year 25
J. O'Keefe and A. Johnson
Measurements of regeneration following removal in 1990 of a 64-year old red pine plantation on the Prospect Hill tract were made again in 2014 (year 25) after a five-year hiatus. Species, height class, origin (sprout or seedling), evidence of browsing and condition (alive or dead) 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.
No evidence of browsing was observed in 2014. 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.
The decline in stem density observed in year 20 (2009) continued through 2014, but at a slower rate (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, 10,079 stems/ha in 2009 and 9,338 stems/ha in 2014. Red maple (34.4% of stems in 2014 vs. 25.5% in 2009) overtook white ash (20.6% of stems in 2014 vs. 33.3% in 2009) as the most numerous tree species in 2014 largely due to prolific sprouting of dying larger stems of red maple and little new sprouting of white ash. The more shade tolerant sugar maple remained the third most numerous species representing 19.6% of stems in both 2014 and 2009. Black cherry continued to suffer mortality, declining from 3.9% of stems in 2009 to 3.2% in 2014. Red oak continued to increase to 11.6% of stems in 2014 from 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 decreased to 16.4% in 2014, down from 19.1% in 2009, but only 13.4% in 2004. From 1997 through 2001 about 20-25% of the stems counted originated as seedlings. This variation in percent seedlings is probably the result of varying annual seed crops and seedling survival rates interacting with mortality of suppressed sprouts as the canopy thickens. In 2014 the majority of these seedlings were red oak (54.8%), 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 remained the same: white ash 29.5% (28.9% in 2009); sugar maple 24.6% (24.3% in 2009); and red maple 22.% (21.2% in 2009). The greatest change occurred in black cherry, which declined to 2.2% from 5.0% in 2009, and pin cherry, which declined to 3.8% from 5.7% in 2009. Two other early successional species, represented by only a few large stems, continue to maintain basal area importance: paper birch 12.1% (10.7% in 2009); and trembling aspen 5.4% (3.8% in 2009). A single red oak stem represents just 0.4% of the basal area on the plots (also 0.4% in 2009). We plan to resample again in year 30 (2019).
- Research Category: Conservation and Management
- Figures: regensumstems2014.pdf
regensumBA2014.pdf
