EFFECTS OF PINE PLANTATIONS AND ADJACENT DECIDUOUS FORESTS ON SOIL CALCIUM

Potential depletion of soil Ca and forest sustainability continue to be concerns. Previous studies from the north-central USA have reported depletion of Ca in soil but increased amounts in the overstory of deciduous compared with coniferous forests, with total system Ca remaining constant, To determine if those reports were generalizable, we sampled 38 pairs of red pine (Pinus resinosa Ait.) plantations and adjacent deciduous stands across the area. Records indicated site similarity before plantation establishment. Neither the texture of the rooting zone (0-32 cm), nor the texture, pH, or Ca content of the 32- to 100-cm soil layer differed between forest types, further supporting site similarity. Stands were similar in biomass, but because of lags in plantation establishment, the deciduous stands were older (60 vs. 45 yr), The deciduous stands had greater mass of Ca in the overstory and higher Ca concentration in the 0- to 4-cm mineral soil layer, Both Ca concentration and mass were greater in lower layers of the rooting zone (to 32 cm) under pine, Neither mass of Ca in the forest poor nor in mineral soil to 100 cm differed between types, Contrary to earlier reports, total system Ca was greater in deciduous stands. Our results and others from glaciated areas suggest that deeper soil layers provide minimal Ca to forest stands during a normal rotation, The initial quantity of Ca in the near-surface soil and the input-output balance determine Ca status of a site, but the role of deciduous forests in conserving the inputs deserves further scrutiny,