PARENT SESSION
Poster Session # 11: Disturbance Ecology.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Mycorrhizal colonization of maple and oak seedling roots exposed to prescribed fire and/or overstory thinning.
McQuattie, Carolyn*,1, Rebbeck, Joanne 1, 1 USDA Forest Service, Delaware, OH, USA
ABSTRACT- Disturbance from prescribed burning and/or thinning may change light and moisture conditions to favor oak reproduction and limit competitors such as red maple. However, the effects of these treatments on mycorrhizal colonization of oak and maple seedlings have not been evaluated. Thinning and prescribed burning, alone and in combination, are being used to study seedling responses to these disturbances in Vinton County, OH with four treatment combinations: undisturbed control (U); overstory thinned by 29% (T); prescribed burning (B); burning and thinning (BT). In June and August 2001 (first growing season following treatments), four seedlings (2 black oak, Quercus velutina, ectomycorrhzial species, and 2 red maple, Acer rubrum, endomycorrhizal species) from six plots per treatment were excavated from three subsites with different moisture levels (2 mesic, 2 intermediate, 2 xeric). Seedling root systems (48 per collection) were chemically preserved. Maple roots were cleared and stained, and percent endomycorrhizal roots per root system was quantified by point counting. In oaks, all root tips were inspected microscopically for a fungal mantle or Hartig net. Beaded oak roots displaying no obvious fungal mantle were stained to determine if endomycorrhizal structures were present. At both collection times, mycorrhizal colonization of maple roots ranged from 55% to 76%. Colonization was lowest at xeric sites. Colonization increased between June and August in each treatment; the greatest percent increase (15%) occurred in BT, possibly due to increased light and less competing vegetation. Oak roots were predominantly ectomycorrhizal. Colonization was highest in June for the U treatment (69%) and in August for the T treatment (61%). Beaded oak roots with endomycorrhizal structures (hyphal coils, arbuscules, vesicles) were observed at both collection times in the B and BT treatments. On disturbed sites, oak roots may form both ectomycorrhizal and endomycorrhizal associations that contribute to increased nutrient uptake and seedling survival.
Key words: prescribed fire, mycorrhizae