Conservation of Water Quality Through Forest Management

Michael A. Blazier

Louisiana is part of a region of the United States with remarkable diversity of aquatic resources. For example, waters of the southeastern United States are home to the highest diversity of salamander species in the world. It is also estimated that the southeastern United States has approximately 90 percent of the world’s freshwater mussel species, and the region’s fish species variety is the highest in North America north of Mexico.

Forests coincide with much of Louisiana’s water bodies, so forest management practices are conducted with conservation of water quality in mind. Nearly half of Louisiana is covered with forests, and the state has a robust forest products industry that contributed $11 billion to the state’s economy in 2016. Many forests are managed to improve their survival and growth, and they are partially or fully harvested every 15 to 40 years or more (with harvest intervals depending on the tree species and products for which they are managed) to be made into products such as paper, paneling and structural lumber.

To assure forest management activities protect water quality, forest management professionals and loggers follow best management practices. The Dictionary of Forestry defines best management practices as “a practice or usually a combination of practices that are determined by a state or designated planning agency to be the most effective and practicable means (including technological, economical and institutional considerations) of controlling point and nonpoint source pollutants at levels comparable with environmental quality goals.” A point-source pollutant for water is a contaminant that can be traced to a single source, such as a pipe; such pollutants are not typical of forest management. A nonpoint-source pollutant for water is a contaminant that cannot be traced to a single source. Forestry activities can be associated with nonpoint-source pollution, so best management practices are used for conducting forestry operations to minimize this risk. Decades of research has revealed that when properly conducted, forestry best management practices are effective at minimizing the effects of forestry operations on water quality.

Best Management Practices for Forest Management Activities

Forestry activities that expose and disturb bare soil can lead to contamination of water bodies with errant nutrients via soil erosion. Forestry operations that have this potential and best management practices developed to minimize their effects on water include:

Roads. Forest roads are essential for managing forests and protecting them from fire, but they can be a source of erosion if improperly constructed. Best management practices for planning roads consist of constraining the extent of road networks, minimizing stream crossings, crossing streams at right angles, and avoiding road construction in areas with excessive slope. Considerations for road construction include minimizing exposed soil on roadsides, installing water diversion structures such as culverts and ditches during construction, including structures such as waterbars (narrow depressions) within roads to slow water runoff during heavy rain events, and ensuring that culverts are of proper size to carry water during heavy rains.

Timber Harvesting. Felling and moving (skidding) trees during harvests can disturb soil. Best management practices to minimize soil movement into water focus on avoiding harvest during weather conditions that could increase risk of soil movement, minimizing the number and size of skidding trails, keeping skidding loads light, scattering logging debris onsite to prevent rutting (Figure 1), minimizing or avoiding stream crossings, and minimizing the number of logging decks (areas where trees are de-limbed, piled and loaded onto trailers). A prominent best management practice for harvesting is the creation of streamside management zones. A streamside management zone is a designated area composed of a stream and a region around streams in which forestry activities are restricted (Figure 2). Streamside management zones serve as a vegetative filter for soil and nutrients to restrict their movement into streams. Suggested widths for streamside management zones are 35 feet on each side of intermittent streams (streams that flow seasonally) and 50 to 100 feet on each side of perennial streams (streams that flow continuously). Tree removals and equipment traffic during harvesting are kept to a minimum or avoided within streamside management zones, and no logging decks are located within these zones.

Reforestation. After forests are fully harvested they are replanted, often with tree seedlings (Figure 1). Soil conditions such as root-restricting subsoil layers and high water tables are impediments to seedling survival and growth, and these conditions can be ameliorated by skidder-drawn implements such as subsoil shanks and discs. Tractor-drawn machine planters are also an effective alternative to hand-planting seedlings for some sites. To reduce the erosion potential of these operations, they are avoided within streamside management zones, on sites with steep slope, and on sites with highly erosive soils. Where conducted, mechanical soil improvement and machine planting are done by following land contours.

Suppressing competing vegetation with herbicides in the initial year of forests greatly enhances seedling survival and growth. Prominent best management practices for herbicides include avoiding herbicide applications directly to water bodies, following herbicide labeling to minimize drift of herbicides to nontarget areas, and minimizing or avoiding herbicide application within streamside management zones. These best management practices are also followed for fertilization, which is sometimes conducted for forest plantations.

Best Management Practices Training

Implementing best management practices requires accounting for complex interactions of site, hydrology and equipment factors. These practices were developed with the best available research information and operational experience, and they are continually refined through ongoing research and monitoring efforts. Several important programs were developed in the mid-1990s to facilitate training on and adoption of best management practices. For forest management professionals, the Society of American Foresters administers the Certified Forester program. Under this program, professionals undergo continual training on the science and practice of sustainable forest management, including best management practices. Similarly, the Louisiana Master Logger program administered by the Louisiana Forestry Association provides technical training on logging safety, best management practices and environmental considerations. For forest landowners, there are forest certification programs, such as the Sustainable Forestry Initiative and American Tree Farm System, that certify their forests are managed with best management practices. In cooperation with these programs, LSU AgCenter forestry extension workshops provide Continuing Forestry Education and Continuing Logger Education credits for attendance. Through cooperative efforts among forest landowners, management professionals, natural resource agencies, and university research and extension, forestry best management practices are widely conducted in Louisiana to sustain water quality along with healthy forests.

Michael A. Blazier is a professor of forestry at the Hill Farm Research Station and School of Renewable Natural Resources.

(This article appears in the fall 2017 issue of Louisiana Agriculture.)

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Figure 1. Shortleaf pine seedling (encircled) planted near a logging deck in Claiborne Parish. Logging debris was scattered onsite to reduce soil erosion risk. Gravel was also placed along the logging road at a point of heavy traffic to protect soil.

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Figure 2. Streamside management zone surrounding a perennial stream within a loblolly pine forest in Claiborne Parish. Trees were left unharvested for at least 100 feet on both sides of the stream. To protect the stream from soil displacement, the stream crossing was constructed at a right angle to the stream and gravel was placed in the streambed at the crossing.

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Michael A. Blazier is a professor of forestry at the LSU AgCenter Hill Farm Research Station and the School of Renewable Natural Resources. Photo by Olivia McClure

1/8/2018 10:04:47 PM
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