By Andrew Nix, Forest Management Specialist
Streamside Management Zones (SMZs) are areas of riparian forest that are adjacent to bodies of water such as rivers, creeks, ponds, or intermittent streams. These riparian forests differ from upland forests in their hydrology, plant community, soils, and topography. Riparian forests are generally biologically diverse and fulfill several roles in the ecosystem. Riparian forests have undergone tremendous change due to urbanization, agriculture and forestry over the past century. SMZs serve as filter strips that reduce the volume and flow of surface runoff (a source of erosion and sedimentation), filter sunlight to maintain plant systems and reduce water temperature change in the water body, and provide pathways for animal movement.
In the Southeast, SMZs are usually associated with surrounding uplands that are intensively managed for pine timber production. In these intensively managed forests, SMZs are used as a Best Management Practice for forestry to stay within the confines of the Clean Water Act (CWA). While keeping forestry operations within the CWA, SMZs are serving as travel corridors for wildlife and can link areas of more mature forest habitat that are needed in the life cycle of some species of wildlife. For forestry in Alabama, SMZ width is set at a minimum of 35 feet on either side of the streambed, with extra allowances for steep slopes or highly erodible soils. For wildlife in Alabama, SMZ widths larger than the forestry minimums are highly desirable as the biological diversity will usually increase with width. Less mobile forms of terrestrial wildlife also need wider SMZs and these SMZs need to link habitat that is suitable for these species. SMZs are not permanent set-aside areas; they are management zones as the name implies.
Forests are dynamic and change is taking place all the time. Periodic timber harvest using low impact harvesting systems and group or single tree selection cutting are ideal in managing both the timber and habitat within the SMZ. Fifty percent of the original canopy cover is the minimum that should be retained within the SMZ for it to function biologically. Landowners should have their SMZs clearly marked and decide if they will allow any harvest within the SMZ before any timber sale.
SMZs in Alabama can serve the landowner and the public in many ways when they are properly managed. Excellent timber, wildlife habitat, and water quality can all be found in properly managed SMZs.
For more information contact your district Department of Conservation and Natural Resources wildlife biologist, County Extension agent, or the Alabama Forestry Commission.
Streamsize Management Zones (pdf from the Ala. Forestry Commission)