Biomass, production, and nutrient distribution of a pure Quercus variabilis Bl. stand (stand 1) and two mixed Q. variabilis -Q. mongolica Fisch. stands (stand 2 and 3) were investigated in central Korea. Stand 1 naturally occurred on a site with a southern aspect while stand 2 and stand 3 occurred on sites with a northern aspect. Total (overstory + understory vegetation) biomass (t ha -1 ) and annual production (t ha -1 year -1 ) were 137.8 and 11.1 for stand 1, 216.2 and 16.6 for stand 2, and 253.3 and 19.7 for stand 3. Nutrient contents (kg ha -1 ) in the vegetation were distributed as follows: K, N, Ca, Mg, Na, and P,, and were greatest in stand 3 followed by stand 2, and stand 1. Stand density influenced the differences in biomass, annual production and nutrient contents in the vegetation. Forest floor dry mass and N content (kg ha -1 ) were 13 400 and 169 for stand 1, 10 400 and 133 for stand 2, and 11 200 and 127 for stand 3. Total amounts of N, P and Na in the ecosystem were greatest in the upper 40 cm of mineral soil followed by the vegetation and forest floor. However, the vegetation contained a greater amount of K than the mineral soil. It appeared that microenvironments, such as, aspect influenced the distribution of natural oak species within a relatively small area and resulted in differences in biomass, production and nutrient distribution among the stands.

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Biomass and production of two stands with Quercus variabilis Bl. as the dominant species (stands 1 and 3) and one with Q. mongolica Fisch. as the dominant species (stand 2) were investigated in southern Korea. Stands 1 and 3 naturally occurred on sites with southerly aspects while stand 2 naturally occurred on northerly aspects; stand ages were similar for the three stands (36-38 years old). Total above-and belowground biomass including understory vegetation (Mg ha À1 ) was 108.4 for stand 1, 115.6 for stand 2, and 132.0 for stand 3, respectively. Understory vegetation constituted 17.4% of the total biomass in stand 1 but only 3.7-4.5% in stand 2 and stand 3. Roots constituted 20.1-24.6% of the biomass of the overstory vegetation. Although stand 3 showed the highest total biomass, net production was highest in stand 2 at 12.6 (Mg ha À1 year À1 ); net production levels for stands 1 and 3 were 11.7 and 11.1 (Mg ha À1 year À1 ), respectively. It appeared that the differences in site conditions related to aspect influenced the distribution of naturally regenerated oak species within a relatively small area and resulted in differences in biomass and production among the stands.