Effects of serpentine soil factors on Virginia pine (Pinus virginiana) seedlings

Effects of simulated serpentine soil conditions (elevated Mg:Ca ratio and N i concentration) on seedlings from populations of Virginia pine (Pinus virg iniana Mill.) from serpentine and non-serpentine sites were evaluated in sa nd culture. We determined (1) how seedlings are affected by elevated Mg:Ca ratio and Ni concentrations, (2) if there are interactive effects between M g:Ca ratio and Ni concentrations on seedling growth, needle pigment concent rations, and nutrition, and (3) if Virginia pine populations from serpentin e areas are edaphic ecotypes. A Mg:Ca ratio of 5 and 50 mu M Ni both reduce d seedling growth compared with control seedlings grown in the presence of the standard Mg:Ca ratio of 0.5 and no Ni. Interactive effects between Mg:C a ratio and Ni concentrations were highly significant for growth, foliar pi gments, and needle and root elemental concentrations. Nickel-mediated reduc tions in growth and foliar pigment concentrations were less at the serpenti ne Mg:Ca ratio of 5 than at the standard (non-serpentine) Mg:Ca ratio of 0. 5. Foliar N was reduced by Ni concentrations as low as 10 mu M, and foliar and root K, Ca and P concentrations were significantly reduced by Ni concen trations above 25 mu M, with greater reductions at a Mg:Ca ratio of 0.5 tha n at a Mg:Ca ratio of 5. There were no population x serpentine soil factor interactions for seedling growth, foliar pigment concentrations, or nutriti on, suggesting that seedlings from trees growing on serpentine soils are no t edaphic ecotypes. We conclude that serpentine conditions present at the s ite of seed collection have not resulted in the selection of edaphic ecotyp es of Virginia pine with respect to Mg:Ca ratio and Ni concentration.