Effects of dormant season soil flooding and soil temperature on pin oak (Quercus palustris) seedlings
Abstract
Bottomland forests are the dominant forest cover along the Mississippi Alluvial Valley. Changes in land use and hydrologic regimes have reduced the area of bottomland forest, putting pressure on the remaining area to meet multiple objectives. To maintain migratory waterfowl habitat, some forests are managed as greentree reservoirs and artificially flooded during the fall and winter. Red oaks are a desirable component of these forests for their acorn production, but oak decline and inadequate recruitment pose problems for maintaining quality habitat. Artificial flooding regimes may be a driving factor in oak decline, as flood timing and duration may be outside of historic conditions. Previous studies have shown growing season floods can inhibit root growth, but the impacts of dormant season flooding are not as well studied. We conducted a greenhouse study to determine how winter flooding at different soil temperatures affects the growth and development of Quercus palustris (pin oak) seedlings. We examined the effects of soil temperature and dormant season flooding on Q. palustris seedlings using insulated water baths at 5, 10, and 15 degrees C. Half of the seedlings received soil flooding for 60 days from January to March, after which floodwater was drained for the remainder of the study. Seedlings were harvested before, during, and after flooding. Root length was determined using scanned images and WinRHIZO (Regent Instruments, Inc), after which samples were oven-dried to determine mass. During soil flooding, root mass was significantly less in flooded seedlings than those that were not flooded. However, following drainage this difference was no longer present. By the end of the experiment, seedlings that received flooding exhibited greater lateral root mass and length than those that had not been flooded. Flooding had minor positive impacts on aboveground variables, such as increased stem area, but did not significantly impact aboveground seedling biomass. These findings suggest that Q. palustris may experience temporary stress during dormant season flooding but can recover without lasting effects. While these results seem promising for current greentree reservoir management practices, care should be taken in applying them to field conditions.
Degree
M.S.