Variation in overstory biomass among glacial landforms and ecological land units in northwestern Lower Michigan

Variation in overstory biomass and mean annual biomacc increment (MABI) of upland forest stands was studied at 2 spatial scales: glacial landforms (1:250 000-1:1000 000) and ecological land units (1:10 ooo-1:80 000). Ecological land units were defined based on combinations of ground-flora vegetation, soil and physiography. Overstory biomass ranged from 105 t/ha (MABI = 1.5 t ha^-1yr^-1) on glacial outwash landforms to 208 t/ha (MABI = 3.2 t ha^-1yr^-1) on morainal landforms; 37% of the total variation in biomass was accounted for by landform. Analysis at the ecological land unit scale accounted for a higher proportion of variation c60% of the total. Overstory biomass among ecological land units ranged from 85 t/ha(MABI) = 1.3 t ha^-1yr^-1) for oak-dominated forests occurring on xeric sandy outwash sediments to almost 250 tHa(<MABI = 3.6 t ha^-1yr^-1) for sugar maple-red oak (Acer saccharum-Quercus rubra) forests occurring in mesic morainal positions. Variation in biomass appeared to be strongly related to differences in species composition and variation in soil moisture availability. A relatively strong association between ground-flora composition and productivity was indicated. -from Authors