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METHODOLOGY
Study Area
The study sites were located on forest land throughout Virginia (Montgomery, Botetourt, Buckingham, Sussex, Nottoway, Faquier, Campbell, and Tazewell counties) and in the eastern part of West Virginia (Greenbriar, Summers, Fayette, and Mercer counties) (Figure 3).
Forestlands were owned and managed by various private, and industry companies, private landowners, and state agencies. Sites occurred in the Coastal Plain, Piedmont, Ridge and Valley, and Appalachian Plateaus physiographic regions (Table 4).
The Coastal Plain is made up of mainly plateaus, terraces, and broad swampy flats at lower elevations. This is the least weathered of Virginia’s physiographic regions with parent material being deposited by Atlantic Ocean began or sediments being deposited by the erosion from the Appalachian Highlands. Slope gradient within the SMZ averaged six percent across the study area and ranged between 3 and 13 percent (Table 4). Normal annual total precipitation range from 48 to 56 inches. The Coastal Plain borders and extends along the Piedmont region with the fall line separating the two areas (Buol, 1973). Due to the generally level terrain mechanized harvesting systems are common in this region.
The Piedmont region consists of gently rolling hills with rounded summits and shallow valleys that were created by the converging and folding of metamorphic rocks of various origins and plates. Topography in this region is generally steeper with an average 19% slope gradient found on study sites and ranging anywhere between 2 and 50 percent slope. Normal annual total precipitation equals 48 inches. The Piedmont Plateau surface is approximately 200 feet to 1000 feet above sea level. Erosion has played a major role in developing this region and generally the older soils are stratified above the younger coastal deposits. Although the Piedmont is steeper than the coastal plain, mechanized systems are still commonly used.
The Ridge and Valley region is 65 miles wide is located west of the Blue Ridge province. The topography is made up of long, narrow, even mountain ridges and valleys formed by folding due to plate tectonics followed by differential erosion. Slopes averaged 35 % in the study area and percentages ranged between 8 and 18 percent. These landforms were created from differential weathering and the process of sedimentary rocks eroding. Normal annual total precipitation equals 48 inches.
The Appalachian Plateau lies just west of the Ridge and Valley region and is characterized as winding, narrow-crested ridges and deep, narrow valleys with sandstone rock that is underlain in a horizontal pattern. Areas of high relief have been caused by the eroding of soils due to stream action that has taken place over millions of years. Our plateau sites are in West Virginia and the average slope was also 35 % with slope gradients ranging from 15 to 54 %. Normal annual total precipitation equals 40 inches. Manual systems are more common on the steeper areas in the Ridge and Valley and the Appalachian Plateau.
Soil Characteristics
Soils in these regions have formed from lava flows, hard crystalline, metamorphic, and sedimentary rock, and in unconsolidated sands, silts, and clays of fluvial, marine, and eolian origin (Buol, 1973). The two main soil orders that characterize these eastern forests are the alfisols and ultisols. Alfisols are acidic soils with high fertility levels and the diversity and activity of soil biota are high. Ultisols are characteristic of the southern part of the region. These areas are non-glaciated, older, and highly weathered soils that are more acidic than the alfisols and lower in fertility.
Vegetation Characteristics
Forests in these regions are comprised of the oak/hickory, southeastern coastal plain, and mixedmesophytic deciduous vegetation types (Barbour et al., 1999). Species composition found in the research plots were dominated by tulip poplar (Liriodendron tulipifera L.),white oak (Quercus alba), chestnut oak (Quercus prinus L.), red maple (Acer rubrum), black gum (Nyssa sylvatica), mockernut hickory (Carya tomentosa Nutt.), and sweetgum (Liquidambar stryaciflua). Other hardwoods occasionally found at these sites included beech (Fagus grandifolia Ehrh.), American basswood (Tilia americana L.), black locust (Robinia pseudoacacia), black cherry (Prunus serotina) sourwood (Oxydendrum arboretum), northern red oak (Quercus rubra L.), black oak (Quercus velutina Lam.), scarlet oak (Quercus coccinea Muench.), American hornbeam (Carpinus caroliniana Walt.), and cucumber tree (Magnolia acuminate L.). The softwood component included eastern hemlock (Tsuga canadensis Carr.), eastern white pine (Pinus strobes L.), and Virginia pine (Pinus virginiana).
Site Selection
SMZ sites used in this research were located throughout Virginia and parts of West Virginia. To locate potential study sites, I began by calling state officials, private businesses, industries and consultants and asking them if they had recent harvesting sites that met the desired conditions for this study. If they did, I then spent one day with the forester of that company in the field to physically assess if the site would actually meet the requirements. The requirements were either active or recently active harvesting sites (within 6 months) where the SMZ had been harvested to some degree and was a minimum width of 50 feet. The harvesting system needed to be either the cable-skidder winching system or the feller-buncher/grapple skidder system. Once the site qualified, I then attained permission to include this site in the study by the landowners and company representatives.
Harvesting Systems
Two types of conventional ground-based harvesting systems were evaluated in this study, a manual cable skidder system and a mechanized feller-buncher/grapple-skidder system (see section 1.6 for more information pertaining to harvesting systems). All sites were studied post-harvest, therefore a complete description of the actual harvest system is not available. Machine size and power varied depending on the size of the job and the company performing the harvest. Study plots were managed by different entities; public, private, and industrial companies. Some companies had employed their own logging crews while others contracted the jobs out to independent logging crews or timber agencies. Size of logging crews ranged from one to five employees per job and crews were unaware that this study was taking place. General descriptions of how each system operates are given below.
The manual system uses chainsaws to fell, top, and limb trees before extraction. The cable is then pulled from the winch of a rubber-tired skidder or bulldozer by either the skidder operator or another crew member to the log (Figure 4). Skidders may have winches, grapples, both or swing boom grapples attached depending on the harvesting operation. These logs are generally attached by three to five chokers and pulled to the skidder by the winch. They are then skidded, or dragged across the ground, out of the SMZ to a main skid trail or landing for loading and at no time during the operation are machines allowed to enter the SMZ. This type of system where cables are used is mainly for steep, wet, or broken terrain when it is unstable or unsafe for skidders to operate on or travel.
1.0 INTRODUCTION
1.1 Economic Considerations
1.2 Laws and Regulations
1.3 Forest Harvesting BMPs
1.4 Potential Harvesting Impacts on Water Quality
1.5 Streamside Management Zones (SMZs)
1.6 Harvesting Systems
2.0 SMZ GUIDELINES REVIEW
2.1 SMZ Width Recommendations
2.2 SMZ Harvesting Intensity Recommendations
2.3 SMZ Harvesting System Recommendations
3.0 STUDY OBJECTIVES
3.1 Objectives
3.2 Hypotheses
4.0 METHODOLOGY
4.1 Study Area
4.2 Site Selection
4.3 Harvesting Systems
4.4 Sample Plots
4.5 Parameters Measured
4.6 Statistical Analyses
5.1 Site Description
5.2 Canopy Cover vs. Basal Area
5.3 Visual Soil Disturbance
6.0 DISCUSSION
6.1 Harvesting Systems in SMZs
6.2 Harvesting Intensities on Visual Soil Disturbance
6.3 Basal Area vs. Canopy Cover
6.4 Impacts of Slope Gradient on Soil Disturbance
6.5 Soil Disturbance Location
7.0 CONCLUSION
8.0 REFERENCES
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Logging in the Streamside Management Zone: Effects of Harvesting System and Intensity on Visual Soil Disturbance
