Sugar maple (Acer saccharum Marsh.)-dominated northern hardwood forest
s were examined at four locations along an acid deposition and climati
c gradient in the Great Lakes region of the USA. The study sites were
matched in terms of physiography soils, stand history, and vegetative
characteristics. Measurements of basal area and biomass growth were ma
de for the 1988-1991 growing seasons. There were no significant differ
ences in either basal area or biomass increment among the four sites o
ver the 4 year period. There was a great deal of year-to-year variabil
ity with relative basal area growth rates ranging from as low as 0.2%
to as high as 2.4% on a single site in successive years. Growth effici
ency measures reflected this variability with as much as an 800% diffe
rence between successive years on a single site. When coupled with yea
r-to-year variability of up to 34% in leaf area related to heavy seed
years and defoliation, this indicates that growth efficiency and leaf
area measures are not consistent indicators of aboveground productivit
y for tolerant deciduous species, especially if derived from short-ter
m measurements or temporary plots.