Effects of Alternative Silvicultural Treatments on Regeneration in the Southern Appalachians

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Virginia Tech

Harvesting practices in the southern Appalachians have moved away from clearcutting in favor of variable retention harvesting systems. A study was initiated in 1995-8 to investigate the effects of retaining varying numbers of residual trees on regeneration in seven silvicultural treatments. A second study specifically focused on stump sprouting in only three of those treatments. The treatments for first study included: a clearcut, commercial harvest, leave-tree, shelterwood, group selection, midstory treatment, and an uncut control. The second only focused on the clearcut, leave-tree, and shelterwood.

These treatments were implemented in seven stands in Virginia and West Virginia over two physiographic provinces, the Appalachian plateau and Ridge and Valley. The stands were even-aged oak dominated Appalachian hardwood stands on fair quality sites with average ages ranging from 63 to 100 yrs. Permanent plots were randomly located in each stand and all overstory trees (>5m tall) were inventoried and tagged prior to harvest. Regeneration was also quantified. Harvest occurred between 1995-8. For the current studies the plots were re-inventoried 9-11 years post-harvest and all regeneration in all treatments as well as stump sprouts in the selected treatments were quantified.

The first study utilized a mixed model ANOVA to analyze five species groups: oak, maple, black cherry-yellow-poplar, miscellaneous, and midstory. Response variables included importance value, average height, and density compared within species group and among treatments. Differences between sprout and seedling origin regeneration were also investigated within species group among treatment. Results indicated that oak densities were similar in all of the treatments, and stump sprouts were larger and more frequent than seedlings. Maple exhibited an increase from pre-harvest overstory importance and exhibited competitive sprouting. The black cherry-yellow-poplar group had few but highly competitive sprouts and a considerable increase in seedling origin regeneration in all treatments. The miscellaneous species densities increased as well with more competitive sprouting in some treatments. The midstory species were excluded from the analysis as it was assumed these species would not occupy canopy positions in a mature stand.

The second study investigated differences in the percent of stumps that sprouted and the number of sprouts per stump. The percent data were analyzed using a non-parametric one-way ANOVA and regression analysis, while the sprouts per stump data were compared in a mixed model ANOVA and regression. Species were combined into six groups: the red oak group, chestnut oak, red maple, white oak/hickory group, mixed mesic group, and midstory group. The plateau tended to have reduced sprouting compared to the Ridge and Valley for most species groups and treatments. The red oak group, chestnut oak, and red maple exhibited reduced sprouting with increased residual basal area. The mixed mesic group did not show any effect in sprouting related to residual basal area. Only chestnut oak showed fewer sprouts per stump as residual basal area increased.

clearcut, leave-tree, shelterwood, group selection, stump sprouts, oak, mixed model, silviculture, Appalachian hardwoods