PARENT SESSION
Oral Session # 65: Herbivory V: Deer, Geese, and Chemistry.
Presiding: K Bjorndal
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 103.
Deer and sedge effects on vegetation dynamics in a deer altered landscape.
Randall, Jesse *,1, Walters, Michael*,1, 1 Department of Forestry, East Lansing, Michigan
ABSTRACT- Great Lakes northern hardwood ecosystems with high deer densities have undergone profound vegetation changes. These include tree recruitment failure, decreased vertical structure complexity, and shifts in composition to less palatable species such as sedge (e.g. Carex pensylvanica). Some of these shifts may persist, even if deer are removed, potentially creating an alternate stable vegetation state. We are quantifying the impacts of high deer and sedge densities on vegetation dynamics with a field experiment that includes vegetation removal treatments, that are possible restoration methods (sedge removal, herbicide, herbicide and scarification, and controls), in deer exclosure and open areas. Here we present 2nd year results of a 5 year study. Planted sugar maple seedling survival was significantly greater in deer exclosures (81.6%) compared to open areas (54.2%). Sedge removal resulted in 1- increased survival for planted white ash when compared to controls in open areas, and, 2- compared to controls, large declines (>30%) in survival of sugar maple seedlings and biomass of herbs <25 cm tall, in open areas but not in exclosures. In 2001 Michigan experienced a prolonged growing season drought. Areas with sedge removal had higher soil moisture (9.9%), and lower visible damage to sugar maple seedlings than areas with sedge (8.6%). Treatments thus far show no effects on N mineralization rates, but standing pools of NH4+ in sedge removal areas have increased. Preliminary results from a companion greenhouse experiment corroborate our field results as sedge closes its stomates at lower predawn water potentials and transpires at a greater rate than sugar maple, and sedge decreases soil NH4+ below that of sugar maple. To date the restoration of vegetation does not appear to be effective in open areas, but herb biomass has returned to control levels within exclosures.
Key words: deer forest interactions, alternate stable vegetation state