ABOVEGROUND PRODUCTION AND CANOPY DYNAMICS IN SUGAR MAPLE AND RED OAK TREES IN SOUTHWESTERN WISCONSIN

Aboveground net primary production, canopy allometry, growth efficiency, and sapwood volume were compared for early- to mid-successional red oak (Quercus rubra L.) and late-successional sugar maple (Acer saccharum Marsh.) co-occurring in young and mature natural stands in southwestern Wisconsin. For similar-diameter trees, shade-tolerant sugar maple supported a significantly greater (p < 0.05) stem, branch, and foliage biomass and leaf area than mid-tolerant red oak. Red oak and sugar maple had similar stem net primary production rates over a 5-year period (1984-1988), but sugar maple had a significantly greater total aboveground net primary production than similar-diameter red oak. However, red oak had a significantly greater (p < 0.0001) growth efficiency (stem net primary production per unit of leaf area) than sugar maple. The significantly greater sapwood volume, but equal stem volume, of sugar maple versus red oak suggests that annual stem maintenance respiration costs may be greater for sugar maple than for red oak. Possible causes for differences in stem net primary production and growth efficiency between early- and late-successional tree species are discussed.