This study was conducted to evaluate the effect of site quality on allometric equations, stem density and biomass expansion factors(BEFs) in a 20-year-old Machilus thunbergii plantation. The study site was located in Jindo county, Chollanam-do, southern Korea. Total 14 trees were harvested from the good site(tree height: 6.7 m) or poor site(tree height: 4.6 m) assumed by tree height growth. Allometric equations, stem density and biomass expansion factors were calculated from the sampled trees. Site-specific allometric equations of tree components were significant(p<0.05) with diameter at breast height(DBH). Also, generalized allometric equations could be applied to estimate tree biomass regardless of the difference of site quality because of no significant effect on slope of site-specific allometric equations. Aboveground tree biomass was significantly higher in the good site(81.0 Mg ha-1) than in the poor site(46.3 Mg ha-1). Stem density was not significantly different between in the good site(0.65 g cm-3) than in the poor site(0.67 g cm-3), whereas aboveground tree and leaf BEFs were significantly higher(p<0.05) in the poor site(aboveground: 2.23; leaf: 0.42) than in the good site(aboveground: 1.82; leaf: 0.23). The results indicated that aboveground Biomass and Biomass expansion factors of a Machilus thunbergii plantation were affected by site quality.

This study was conducted to determine the relationship between stand and soil environmentalfactors, and soil respiration rates at various levels of basal area in a 40-year-old natural redpine(Pinus densiflora S. et Z.) stand in southern Korea. Soil respiration rates were measuredmonthly using an infrared gas analyzer system from six basal area treatments between 21.4 m2ha-1 and 46.7 m2 ha-1 for one year. Soil respiration at various levels of basal area showed aclear monthly variation, which had a similar pattern to soil temperature. The mean annualsoil respiration rates were positively correlated with increasing basal area(r=0.86, p<0.05),aboveground tree carbon (C) storage(r=0.85, p<0.05) and needle litter C fluxes(r=0.88, p<0.05),but the rates were not correlated by the soil environmental factors(p>0.05) such as the meanannual soil temperature, soil water content, soil pH, and soil organic C content during the studyperiod. The results indicate that it is important to understand the role of stand attributes in themean annual soil respiration rates in a stand level.