Ionic Composition of Forest Soil Solutions and Effects of Clearcutting

Soil solutions were sampled with porous‐cup suction devices during a rainy season (December 1974–May 1975) from adjoining uncut and clearcut Eucalyptus globulus forest areas in the Berkeley hills, California. Concentrations of K + , Ca 2+ , Mg 2+ , NO 3 ‐ , HCO 3 ‐ , and pH and specific conductance were lower in the clearcut. The high exchange capacity of the clay‐loam soil, the limited amount and duration of rainfall, and the removal of slash and litter from the clearcut were factors contributing to these results which differ from those of similar studies of the effects of clearcutting elsewhere. The relative proportions of Na + , Cl ‐ , and SO 4 2‐ were higher, and those of K + , Ca 2+ , NO 3 ‐ , and HCO 3 ‐ were lower in the clearcut compared to the forest; the proportions of Mg 2+ were the same. The relative ionic composition of soil solutions in the clearcut resembled that of the acid rain (pH 5.0). The higher proportion of HCO 3 ‐ in the forest was due to throughfall inputs, root respiration, and decomposition of the forest floor. No NH 4 + was detected in soil solutions from either area. Concentrations of most ions were correlated between and within soil horizons, although K + was an exception due to clay fixation. During anaerobic conditions, Mn and Fe and associated Cu and Zn were mobilized in the soil solution. Increased quantity of soil water following clearcutting resulted in increases in total amounts of most ions in solutions in the lower portion of the profile in the clearcut, compared to the uncut forest.