BMPs for forested riparian area vegetation management
By Kim Ingram, University of California Ag & Natural Resources
According to Rob York, Forestry Specialist at UC Berkeley, riparian areas are disturbance dependent. They are an important component of a forested ecosystem, hosting abundant biodiversity in plant, insect, and animal species. As the interface between aquatic and terrestrial habitat, 'disturbance' in the riparian ecosystem can be
Photo 1. Forested riparian area. Photo by Kim Ingram, UC ANR
many things, including 'natural' and 'human caused'. California Native Indian tribes often applied fire in riparian areas to encourage the re-sprouting of desirable tree and shrub species that respond well to low-intensity fire.
Managing riparian vegetation calls for creativity. With increasing tree mortality from drought, insects and diseases, climate change effects and increasing intensity of wildfire, forest landowners and forest researchers are asking more questions around how to treat vegetation within riparian areas to address fire hazards from fuels accumulation, as well as to protect the complexity of the area.
Vegetation management activities done in riparian areas can be ecologically justified and even necessary for long-term sustainability. California landowners should familiarize themselves with the associated rules and regulations laid out in the California Forest Practice Rules. Under the rules, the Watercourse and Lake Protection Zone (WLPZ), also called Streamside Management Areas, defines areas of land along both sides of a creek or stream, or around the circumference of a lake or spring, that buffer riparian areas against soil disturbances that potentially come from heavy equipment. The width of a WLPZ varies between 50 and 150 feet depending on slope, the class of the watercourse, and the geography of the location. Within the WLPZ, percentages of surface cover, canopy cover, and undisturbed areas must be maintained to protect water resources and wildlife habitat.
Though specific to California, best management practices for WLPZs from the California State Water Resources Control Board, can be a guide to other areas of the country and include:
Evaluate sensitive riparian conditions in areas with the potential to be directly impacted by management activities, including existing roads, skid trails and landings; unstable and erodible watercourse banks, unstable upslope areas, flood prone areas, and riparian zones.
Map spawning/rearing habitat for anadromous salmonids and evaluate the condition of the habitat using habitat typing that, at a minimum, identifies the pool, flatwater, and riffle percentages.
Protect vegetation in the WLPZ, marking trees within WLPZs, before thinning or preharvest activities begin, to ensure shade retention and preservation of a multi-storied stand. Provide for future large woody debris for aquatic habitat.
Protect soils to prevent erosion, treating exposed mineral soil adjacent to perennial streams with mulch, riprap, grass seed, or chemical soil stabilizers to reduce soil loss. This does not apply to the traveled surface of roads.
Establish an Equipment Limitation/Exclusion Zone that prohibits or allows for limited use of heavy equipment in order to prevent soil disturbance, erosion and sedimentation into watercourses.
For landowners looking for guidance on vegetation management, options include:
Hand thinning and pile burning - ensuring that ash does not reach the watercourse;
Prescribed fire - in the spring or after fall rains begin;
End lining - used to remove larger trees using cables and heavy equipment that is stationed outside of a buffer area; and
Mechanized harvesting - which can be allowed to occur in some cases.
Landowners should recall that whatever vegetation management activities used, has advantages and disadvantages particular to the specific site location and conditions.
