Soil respiration and the hydrolysis of fluorescein diacetate (FDA) as a measure of total microbial activity were investigated in central Korea, at three sites that had been changed from abandoned agricultural lands to natural vegetation: rice field conversion to forest (RF), crop field conversion to shrub (CS), and indigenous forest (IF). Seasonal variations in soil respiration were affected by soil temperature and, to a lesser extent, by photosynthetically active radiation (PAR) and soil moisture. The mean annual rate of soil respiration ($gCO_2m^{-2}hr^{-1}$) was highest at CS (0.36), followed by IF (0.29) and RF (0.28), whereas the total annual soil respiration ($kgCO_2m^{-2}yr^{-1}$) was 2.82 for CS, 2.46 for IF, and 2.40 for RF. Mean annual FDA hydrolysis (${mu}gFDAmin^{-1}g^{-1}dry;soil$) was higher at RS (4.56) and IF (4.61) than at CS (3.65). At all three land-use change sites, soil respiration was only very weakly correlated with FDA hydrolysis.