Yi Jun Xu
Louisiana is blessed with an abundance of forests and waterways. Miles of rivers, bayous and lakes provide Louisiana’s citizens with fishing, hunting, boating and recreational opportunities, which contribute to the state’s wealth and economic growth. Many of these water bodies are located in or adjacent to forested areas, which occupy nearly half of the state’s land base. Louisiana’s forests, water and economic and environmental well-being are inextricably intertwined.
Water quality of streams and bayous is not only dependent upon conditions within the channel, but can be significantly affected by the surrounding landscape. A riparian buffer comprised of trees and vegetation can help mitigate the impact of land uses, such as roads or agricultural fields that can affect a stream. Forested areas play an important role in maintaining healthy water quality by reducing surface runoff. They have the ability to slow down storm water runoff, allowing for increased infiltration and soil water storage. Excess nutrients are then absorbed into the soil, where they can be used by plants instead of reaching waterways and potentially causing eutrophication. Additionally, forests help reduce erosion, contributing directly to stream channel stability and habitat quality.
Maintaining forests near waterways helps protect water quality. Lower order streams hold small volumes of water and are especially prone to changing air temperature and the influence of sunlight. Trees help maintain the temperature of the stream by providing valuable shade, blocking direct sunlight with canopy cover. Stream temperature often affects other critical water quality parameters. For example, increased temperature tends to cause decreased dissolved oxygen, which is especially critical in many of Louisiana’s streams and bayous.
While protecting the environment, Louisiana’s forests produce a large variety of commercial products. Forests of Louisiana managed for timber production constitute the state’s top agricultural crop, contributing an estimated $4.55 billion to Louisiana’s economy in 2005. Because of the large land base of forests, management practices in forested areas directly or indirectly affect physical, chemical and biological properties of many waterbodies.
To minimize the effects from forestry operations, a best management practices (BMPs) manual was developed in 1988 for forest landowners, logging contractors and the forest industry to serve as a practical field guide. In 2000, the manual was revised with more detailed guidelines and technical procedures to be followed for each forestry operation. The revised manual, available on the Louisiana Department of Agriculture and Forestry Web site at www.ldaf.state.la.us, includes descriptions of federally mandated BMPs for forestry operations in wetlands and consists of an array of various forestland management guidelines and techniques to prevent sediment, nutrient and organic material runoff. Although it is a voluntary program, implementation of the BMPs is currently high across various land ownerships and regions in Louisiana (Figure 1).
The effectiveness of these forestry BMPs may vary widely from the southern coastal lowland to the northern upland of the state. Land managers need to understand the inherent variability of topography, soils and hydrology of the forested area for BMPs to be properly implemented and therefore effective. It is also important to determine how local forestry operations might affect stream conditions in the larger watershed.
LSU AgCenter scientists are conducting research to evaluate the effectiveness of current Louisiana Forestry BMPs. A study located in a predominately forested watershed, Flat Creek Watershed, in central Louisiana monitors water quality changes across the entire basin (See top of page 20). Storm runoff and nutrient discharge are being measured at various locations using automatic stream sampling systems. Physical, chemical and biological indicators are being analyzed to evaluate water quality changes with forestry operations that implement BMPs.
Geographic Information Systems (GIS) will also be used to identify spatial and temporal water quality patterns in the watershed. This spatial analysis will help the researchers quantify the effects of forest operations on water quality and evaluate the BMP effectiveness in water quality protection across the landscape. Such information will be essential in refining forestry BMP guidelines to optimize protection of stream health. Yi Jun Xu, Associate Professor, and Adrienne Viosca, April Mason and Philip Saksa, all graduate students, School of Renewable Natural Resources, LSU AgCenter, Baton Rouge, La.
(This article was published in the spring 2006 issue of Louisiana Agriculture.)