RESPONSES OF HARDWOOD REGENERATION TO FIRE IN MESIC FOREST OPENINGS -III - WHOLE-PLANT GROWTH, BIOMASS DISTRIBUTION, AND NITROGEN AND CARBOHYDRATE RELATIONS

The effects of fire on the carbon and nitrogen balance of northern red oak (Quercus rubra L.), white ash (Fraxinus americana L.), and sugar maple (Acer saccharum Marsh.) regeneration were studied in mesic openi ngs in a hardwood forest. A plot in each of four openings was burned i n the spring of both 1989 and 1990. Relative growth rate, leaf weight ratio, and concentrations of nonstructural carbohydrate and N were mon itored on planted and extant regeneration in burned and nonburned plot s. In the absence of fire, extant oak grew as rapidly as ash and maple , but the relative growth rate of planted oak was the lowest of any sp ecies or regeneration type. Repeated burning had little effect on the net growth of oak, but it decreased that of ash and maple by 24-85%. F ire effects on relative growth rate were mediated primarily by changes in leaf weight ratio, but the causes underlying these changes were no t fully elucidated. They were not consistent with trends in plant nons tructural carbohydrate or N concentration, which increased or remained unaffected after fire in all species. In general, oak possessed a num ber of characteristics, such as a high root starch concentration and a n abundance of belowground dormant buds, which appeared to contribute to its post-fire vigor.