Riparian forest and instream large wood characteristics, West Branch Sheepscot River, Maine, USA

This study examined riparian forest and instream large wood characteristics in a 2.7 km reach of the West Branch of the Sheepscot River in Maine in order to increase our basic knowledge of these components in a system that is known to have undergone multiple land conversion. The West Branch is approximately 40 km long, drains a 132 km2 watershed and is vitally important to the remnant population of Atlantic salmon (Salmo salar) and other native species. The riparian forest is comprised of relatively small trees with a mean DBH of 21 cm (SD ± 10.92) with 56% of the trees having a DBH <20 cm. Balsam fir (Abies balsamea) and red maple (Acer rubrum) are the most common species (54%), and 75% of all trees are short-lived, small diameter species. These data suggest the riparian forest in the West Branch Sheepscot River is dominated by young forest stands, a legacy of land use. During a survey conducted in 2005, 210 pieces of large woody debris (LWD) were identified in the study reach; an average of 78 pieces km−1. The total volume of pieces was 8.5 m3 or 3.2 m3 km−1 (LWD in this study is defined as pieces ≥10 cm in diameter and >2 m in length). The mean diameter of LWD was 17 cm with 75% of all pieces having a diameter <20 cm. Most pieces were oriented parallel or nearly parallel to the channel and did not appear to influence channel morphology. In contrast, larger pieces were more often in perpendicular or nearly perpendicular orientations, and were more likely to have a pool-forming function. Overall, the reach has low levels of stable large wood, which do not have a major influence on stream habitats.