Paul Soltesz' Graduate Defense Seminar

A Graduate Defense Seminar will be presented by Paul Soltesz, an MS student in Ecosystem Science, on Friday, June 20th at 1:00 p.m. in 460 Kottman Hall. He will present Large Wood Dynamics in Central Appalachian Headwater Hemlock Ravines.

In steep, forested, headwater streams, large wood (LW) is a critical component that influences ecological and geomorphic processes including channel structure, sediment and nutrient dynamics, flow regimes, and habitat formation. In the eastern US, LW dynamics may potentially change in eastern hemlock forests in response to the invasive insect, the hemlock woolly adelgid (HWA), which causes widespread tree mortality. To better understand the potential consequences from HWA and for effective management of natural resources, an understanding of LW dynamics in these systems prior to tree mortality is necessary. This study quantifies 1) LW distribution in Central Appalachian hemlock ravines, 2) influences on LW loading to streams, and 3) spatial grouping patterns of LW pieces based on accumulation, stability, and geomorphic impact characteristics of LW in these systems prior to HWA mortality and recruitment to the channel. A field study that included 24 streams located across southeastern Ohio, West Virginia, and western Virginia was conducted in which channel morphology, in-stream wood load, and wood recruitment potential were recorded. Wood loading ranges from 0.4 to 19.8 m³/100m (median 5.6 m³/100m), which is low relative to other areas of the world, and is attributed to reflect a legacy of logging. Pieces are generally small (e.g., less than bankfull width), though large pieces disproportionately affect LW dynamics in terms of wood volume and potential jam formation. Wood loads correlate both  with valley recruitment processes, including stand characteristics and valley geometry that influence wood entering the channel, and retention processes, including physical channel dimensions and substrate that influence transport through the channel. Higher loads are associated with smaller, confined basins, small channel dimensions, and low hydraulic driving forces. Pieces display a variety of characteristics, but three general grouping patterns result from piece dimensions and environmental factors including 1) larger, stable pieces that functionally store sediment, stabilize the bank, and create pools, 2) relatively stable pieces which deflect flow and dissipate energy with a seemingly random distribution, and 3) smaller pieces associated with flow deflection and energy dissipation composed of stable and unstable pieces. Information gained from this study will provide valuable knowledge on the role of LW in these systems, which is especially important to understand in light of potential HWA-related environmental change.