TITLE:
Forest Response to the US 1990 Clean Air Act: The Southern Spruce-Fir Ecosystem
AUTHORS:
Stephen A. Banks
KEYWORDS:
Southern Spruce-Fir; Balsam Woolly Adelgid; Forest Stand Development; Forest Response; Forest Regeneration; Atmospheric Deposition; Forest Decline
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.3,
February
8,
2014
ABSTRACT: The history of the Black Mountains in North Carolina and the southern
Spruce-Fir ecosystem has been fraught with widespread forest decline since the
mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the
most recognized causes of decline. Uncertainty arose about the future of these
forests, and projections were made regarding the endangerment or extinction of
the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains
dating 1985, 2002, and 2012. Indications that the Fraser fir population is
stabilizing from a “boom-bust” cycle of population growth and has entered the
stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to
2002, and then declined 40% by 2012 at the highest elevations in the forest.
Overall, fir appeared to be more impacted on western facing slopes than eastern
ones. The population of red spruce experienced a steady decrease in live stem
counts, but an increase in live basal area through all years, and at all
elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce
was also most negatively impacted on western facing slopes. Live stem density
was significantly higher (P 0.001) than eastern plots, but live
basal area was similar between the two aspects. Atmospheric deposition
concentrations of the four main acidic molecules at Mt. Mitchell all peaked in
1998, but decreased by 2012. These reductions, occurring shortly after
tightened regulations in the 1990 amendments to the Clean Air Act may have
potential implications for increased forest resilience.