Methods and materials
Study site description
This research was part of a larger Diversity Study, which is evaluating the impacts of alternative silvicultural systems on animal and plant community ecology in the southern Appalachians. The Diversity Study had 7 study sites located in Virginia and West Virginia. The large 5-acre treatment areas required for the wildlife habitat component of the study precluded treatment replication at each location. Criteria used to initially select sites were:
- the overstory composition was predominately oak species
- the site index was in the range of 60-80 ft. at 50 years for upland oaks.
- the overstory was maturing or mature (50-150 years old)
- slopes were moderate (<45%) and aspects were generally southern
- stand regeneration was a viable management tool
Four of the seven sites from the Diversity Study were used in this component of the project. The four sites were selected based on the fact that they would have completed four years of growth following harvest at the time of measurement (Table 1). Study sites were located in the Jefferson National Forest in the Blacksburg (BB2), New Castle (NC) and Clinch Ranger Districts (CL2) in Virginia, and in MeadWestvaco’s Wildlife and Ecosystem Research Forest (WV1) in West Virginia (Fig.2).
The climate of all the sites is classified as temperate and moderately moist. The NC and BB2 sites are located in the Ridge and Valley physiographic province, have an average daily temperature of 69F in the July and 35F in December (Table 1). Average annual precipitation is 40 inches, distributed equally throughout the year. The CL2 site is located in the Cumberland Plateau physiographic province, has an average daily temperature of 69F in July and 37F in December. Average annual precipitation is 46 inches, distributed equally throughout the year.
The WV1 site in the Alleghany Plateau physiographic province, has an average daily temperature of 67F in July and 29F in December. Average annual precipitation is 45 inches, distributed equally throughout the year (NOAA, 2001).
The soils at all four sites are well-drained, and derived from sandstone and shale parent material from colluvium or residuum. Depth to bedrock ranges from 1.5-4.5 feet, and soils are rocky, well-drained and acidic. The soil type at BB2 is the Berks-Weikert complex (Creggar et al., 1985), characterized as a loamy-skeletal, mixed, active, mesic Typic Dystrudepts in the Berks series and a loamy-skeletal, mixed, active, mesic Lithic Dystrudepts in the Weikert series. There is no soil survey completed for the area around the NC site, but inspection of the soil leads to the conclusion that it is also a Berks-Weikert complex, only in a much stonier phase. The soil at CL2 is the Muskingum series (Perry et al.1954), which is classified as a fine-loamy, mixed, semi-active, mesic Typic Dystrudepts. The soils at the MeadWestvaco site are in the Gilpin-Dekalb stony complex (Pyle et al., 1982), and are classified as a fine-loamy, mixed, active, mesic Typic Hapludults in the Gilpin series and a loamy-skeletal, siliceous, active, mesic Typic Dystrudepts in the Dekalb series.
Treatment and plot layout
At each site, the 6 silvicultural treatments were randomly assigned to 5-acre treatments areas (Fig.3), with no buffer zone in between treatments. Within each treatment area, three 78.8ft.x78.8ft. “tree plots” were installed. The location for the center of the first tree plot was determined by using a random number generator to select an azimuth and distance from the treatment area center. To avoid overlap, the next two tree plot centers were located by adding 120 and 240 to the azimuth of the first plot. All tree plots were located at least 75 feet from the border of a treatment area. The plots were marked with PVC pipes at the corners and along the perimeter.
Within each tree plot, sixteen 19.7ft. x 19.7ft. “shrub plots” were established. A grid was overlaid on each tree plot, dividing it into 16 squares of equal size. A random number generator was used to select which 3 shrub plots to sample, which represent the sub-sampling unit. A total of 9 shrub plots were established in each treatment area (9 sub-sampling points). The corners of shrub plots, if on the tree plot perimeter, were located with the aforementioned PVC pipes. The corners of shrub plots completely in the interior of the tree plot were flagged. For post-harvest sampling, the shrub plots were re-located using the PVC pipes and flagging. If the flagging was not present, corners of a shrub plot were established using a compass, with the perimeter PVC pipes as reference points. Data regarding pre- and post-harvest regeneration in the silvicultural treatments were collected on these plots.
At each site, the 6 silvicultural treatments were randomly assigned in 5-acre blocks, with no buffer zone in between blocks, to make the total area per site of 30 acres (Fig.3). The layout of the treatments in relation to one another was assigned at random. The treatments are defined as follows:
1) Control: no silvicultural activity within the stand.
2) Group selection system: Two or three groups, each from 0.25-0.50 acres, were made in each EU. All stems in the group cut were felled. Additionally, TSI thinning was conducted in the areas between harvest groups. Intensity of thinning was variable among sites. This treatment represents portions of the group-selection treatment area that were in the intensely harvested group cuts. Harvest plans call for re-entry to this treatment in 15-20 years to create an uneven-aged structure.
- Shelterwood system: 50-60 ft2/acre of main canopy basal area was retained following the initial cut. Residual trees were selected based on good form, dominant or codominant crown position, and species desirability (oaks and other commercial species). The residual stand will be harvested when satisfactory reproduction has been established and is ready to be released. At the time of the four-year post-harvest sampling, the residual overstory on all four sites was still intact.
- Commercial clearcut: 20-30 ft2/acre of basal area was retained following the initial cut. The residual stand was typically unmerchantable poletimber or sawtimber cull trees. The residual stand will remain through-out the next rotation, creating a two-aged structure. This treatment has been called a “junk shelterwood” or “irregular shelterwood” in previous studies. However, because of the poor quality of the residuals, and the lack of any intent to remove the overwood in the future, “commercial clearcut” was selected as the best description of this treatment.
- Leave-tree system: 10-20 trees/acre (approximately20ft2 of BA/ac) were left to remain throughout the rotation, thus creating a two-aged structure. Residual trees were selected based on good form, dominant or codominant crown position, and species desirability (oaks and other commercial species).
- Silvicultural Clearcut: Removal of all stems >2” DBH, creating an even-aged Non-merchantable stems were felled and left on the ground.
The condition of the group selection treatment warrants additional explanation. In the original 5-acre group selection treatment areas, the permanent plots did not necessarily fall in the actual group selection cuts. On the BB2 site, none of the 9 shrub plots were located in disturbed parts of the treatment area. As this study was examining regeneration after silvicultural treatments, it would be misleading to use these data under the treatment label “group selection.” To fix this problem, just prior to the 4th-sampling period, each shrub plot was classified as either inside or outside a group cut. This split one treatment area into two; what was formerly the “group selection treatment” now became the “group selection-cut” and “group selection-uncut” treatments. Once the re-classification was complete, nine new shrub plots were established inside a 5-acre group-selection treatment area. The new plots were established in the proportion needed to attain full sub-sampling intensity for both group selection treatments. If a group selection treatment area had 2 shrub plots inside a cut and 7 outside a cut, then 7 new plots were established inside a cut and 2 were established outside a cut. No pre-harvest or one-year data was available for these newly-established plots. Only data from the “group selection-cut” treatment is presented here.
Objectives and hypotheses
II. Literature review.
History of southern Appalachian forests
Ecophysiology of oak regeneration
Light and survival
Ecology and silviculture of eastern oaks.
Sources of regeneration-advanced regeneration
Sources of regeneration-stump sprouts
Oak regeneration and site quality
Silvicultural systems: clearcutting
Silvicultural systems: group selection
III. Methods and materials
Study site description
Treatment and plot layout
Description of pre-harvest conditions
Overall oak component
Individual stand descriptions.
WV1-Mill Creek, WV
Oak basal area
Description of post-harvest regeneration
Statistical comparison of post-harvest regeneration
Description of post-harvest stand conditions
Residual basal area and light levels
Soil moisture and available nitrogen.
D/CD oak regeneration relative density.
VII. Literature cited
VIII. Cirriculum Vitae.
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