PARENT SESSION
Oral Session #25: Soil Ecology: Microbial and Invertebrate. Presiding: W. Parsons.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.

Influence of canopy tree types on litter production and soil microbial activities in Wisconsin River floodplain.

KANG, HOJEONG¹, THIEL, AARON¹, STANLEY, EMILY¹, ¹

ABSTRACT- Many large river floodplain ecosystems have undergone pronounced changes in forest species composition in the past 50 to 100 years. In Midwestern systems such as the Wisconsin River, floodplain forest changes have been driven by declines in relative abundances of oaks and basswood, and increases in ashes, elms, and silver maples. We assessed potential effects of these tree species shifts on soil biogeochemistry by comparing litter inputs, and chemical and microbial attributes of soils adjacent to 5 tree species that have experienced long-term shifts in relative abundance: Silver maple (Acer saccharinum), swamp white oak (Quercus bicolor), basswood (Tilia americana), green ash (Fraxinus pennsylvanica), and american elm (Ulmus americana). Soil texture, pH, organic matter content, extractable nutrients, and electron transport system (ETS), -glucosidase, -xylosidase, and phosphatase activity of soils were determined on 3 occasions over 2 years in the Wisconsin River floodplain. Silver maples produced the greatest amount of litter (184g m^-2) over a year. Microbial activity (1.6 g g^-1 hr^-1 for ETS, 16.4 nmole g^-1 min^-1 for -glucosidase, 5.4 nmole g^-1 min^-1 for -xylosidase, and 24.0 nmole g^-1 min^-1 for phosphatase) and organic matter content (15%) in surrounding soils were significantly greater for silver maples than for other trees. This implies that an increase in maples has potentially modified biogeochemical processes and soil C cycle.

KEY WORDS: Floodplain, Litter, Silver maple, Soil microbes