Changes in the biogeochemistry of micronutrients (Cu, Zn, Mn, and B) in soils are not widely explored, and studies of temporal changes in micronutrients over periods of decades are rare. At the Calhoun Experimental Forest in South Carolina, four decades of repeated soil sampling has allowed us to estimate long-term changes in micronutrient concentrations in a forest ecosystem. From an archive of samples collected at approximately 5-year intervals, soils from 1962 and 1997 were extracted with both 0.05M HCl and acid-ammonium oxalate (AAO). The median of AAO-extractable Mn, Zn, and Cu was 2.3-6.5 times the median of HCl-extractable Mn, Zn, and Cu for all depths. For Mn and Zn, the correlations between HCl and AAO extracts were 0.86 and 0.68 respectively suggesting that both methods extracted similar soil fractions, although AAO was much more aggressive at solubilizing metals. In the 35-year period, Mn, Zn, and B were depleted throughout the profile (0-60cm), however B declined significantly at each of the four soil depths extracted (p-value<0.001). In contrast, Cu remained relatively unchanged from 0-35cm, but increased significantly at 35-60cm over the same time interval (p-value<0.05). These results indicate the soil has little ability to resupply B, while Cu remains available over several decades. Long-term soil acidification, as much as 0.5-1.2 pH units decrease in the soil profile from 1962 to present, has likely been one factor in the observed patterns. This study suggests strikingly contrasting patterns of processes control the bioavailability of soil Cu, Zn, Mn, and B.