Sediment Losses from Forest Management: Mechanical vs. Chemical Site Preparation After Clearcutting

Abstract

AbstractThe comparative effects of mechanical and chemical site preparation on water yields and sediment losses following forest clearcutting were evaluated over a 4‐yr period in the Athens Plateau area of southwestern Arkansas. After 1 yr of pretreatment measurements, three forested watersheds were clearcut and the residual vegetation and debris were sheared and windrowed but not burned. Three watersheds were clearcut in a similar manner, but received chemical site preparation. Residual trees on two watersheds were injected with 2–4,D amine; the third watershed was aerially sprayed with a mixture of Tordon® (active ingredient; picloram [4‐amino‐3,5,6‐trichloropicoline acid]) and Garlon® (active ingredient; triclopyr [3,5,6‐trichloro‐2‐pyridinyloxyacetic acid]). Three additional watersheds were left undisturbed for controls. Mean annual sediment losses on the mechanically, site prepared watersheds during the first posttreatment year were significantly higher than those from either the chemically site prepared watersheds or controls. Chemical site preparation did not significantly increase sediment losses. Although 2nd yr losses for the mechanical site preparation and control treatments doubled over 1st‐yr levels, no significant treatment effect was detected for either site preparation treatment. Third‐year losses decreased below 1st‐yr losses for all treatments but not to pretreatment year levels. The relatively sharp declines in sediment losses during the third posttreatment year were attributed to rapid regrowth of natural vegetation on the sites.