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.
Highlights
The Southern Appalachian Mountains of North Carolina, Virginia, and Tennessee house a unique and rare forest ecosystem type known as the Appalachian Spruce-Fir [1]
The community level analysis for the Black Mountains over the past 27-year time span revealed a high quantity of dead stem density (DSD) at the highest elevation (1980 m) in 1985
By 2002, significant increases in Live stem density (LSD) at the 1980 m elevation range occurred. This dramatic increase in LSD was mainly attributed to Fraser fir as it comprised more than 80% of all stems at this elevation, and showed significant increases in LSD by 2002
Summary
The Southern Appalachian Mountains of North Carolina, Virginia, and Tennessee house a unique and rare forest ecosystem type known as the Appalachian Spruce-Fir [1]. Canopy dominating tree species in these forests include the red spruce (Picearubens Sargent) and the endemic Fraser fir (Abiesfraseri [Pursh] Poiret). These historical forest ecosystems are remnants of the Pleistocene epoch in an era when the northern reaches of the forests were affixed to the Appalachian southern reaches [1,2,3]. Species composition differences exist in the Appalachian ranges where Picearubens dominates rather than Piceamariana or Piceaglauca, as in boreal systems. The endemic Fraser fir, Abiesfraseri, exists only in the southern Appalachian ranges, as opposed to Balsam fir, Abiesbalsamea, in the boreal reaches [5]. A deciduous shrub understory consisting of Rhododendron catawbiense exists in the Appalachian spruce-fir forest [1,6], whereas boreal forests are essentially one-storied with few shrub species [7]
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