LEAF ELEMENT CONCENTRATIONS AND SELL PROPERTIES IN FIRST-ROTATION AND2ND-ROTATION STANDS OF RED ALDER (ALNUS-RUBRA)

Successive rotations of nitrogen-fixing red alder (Alnus rubra Bong.) may alter soil properties, potentially influencing future tree growth and nutrition. We examined the effects of red alder on soil properties and next-rotation alder leaf and leaf litter element concentrations. A conversion experiment was initiated in 1984 by clearcutting a 50-yea r-old red alder stand and an adjacent 50-year-old Douglas-fir (Pseudot suga menziesii (Mirb.) France) stand. Both areas were replanted with r ed alder, yielding first- and second-rotation alder plots. Prior to co nversion, the 50-year-old alder plot had higher total soil C, N, and e xtractable Ca, Mg, and Al, while pH and available P were lower. The se cond-rotation plot had lower leaf P, Ca, and Mg concentrations than th e first-rotation plot in 1988 and 1989; it also had lower leaf K, Mn, and Fe concentrations in 1989. The second-rotation plot had lower leaf litter N, P, K, Mg, and Fe concentrations, and litter-fall mass and e lement transfer rates were 30-49% those of the first rotation. The fin dings indicate a potential decrease In availability of most macronutri ents when growing repeated rotations of red alder on glacial till deri ved soils.