Vegetation and Tree Regeneration

(Schofield and Wagner) The abundance, diversity, and composition of plants among and within harvested gaps (i.e., four growing seasons after harvest), natural gaps, and under the closed canopy were compared.  Total plant cover was greatest in harvest gaps (34.9% mean cover per gap) and least under the closed canopy (10.6% mean cover per gap).  Mean cover in natural gaps was 25.5%.  Balsam fir was the most abundant species in all three conditions.  Total cover was correlated with distance from the gap center of the largest harvest gaps (1,170 – 2,106 m2) with the highest cover occurring in the gap centers.  Species richness per sample area was greater in harvest gaps > natural gaps > closed canopy but was not correlated with location within the gap.  The most significant change in plant communities was an increase in the abundance of ruderal and exotic invasive species in the larger harvest gaps. Species evenness (measured as the slope of the dominance diversity curves) indicated that 1) plant distribution was uneven under all conditions and 2) that plant cover was least evenly distributed under the closed canopy.  Seedlings (<0.5 m tall) were the most abundant form of tree regeneration, and saplings (0.5 – 2.0 m tall) were most abundant in harvested gaps.  Balsam fir was the most abundant tree species regenerating in natural gaps, while red maple was most abundant in harvested gaps. Harvested gaps tended to have higher numbers of red maple and paper birch in all height classes. Conifers dominated the natural gaps more, with balsam fir, eastern hemlock, and eastern white pine being the predominate species. Regeneration under closed canopies was more indicative of the overstory species, with balsam fir, red and sugar maples, and eastern hemlock more common, particularly in the larger height classes (>2.0 m tall).