Effects of fertilization on seasonal patterns of foliar mass and nutrients of tamarack and black spruce on undrained and drained minerotrophic peatland sites

We investigated seasonal patterns of needle mass and foliar N, P and K of tamarack (Larix laricina (Du Roi) K. Koch.) and black spruce (Picea mariana (Mill.) B.S.P.) as affected by fertilization of undrained and drained minerotrophic peatland sites. The drained site was ditched in fall 1987. Four N-P-K fertilization treatments. i.e. 0-0-0, 0-80-120, 200-80-120, and 400-80-120 kg ha-1, replicated three times on each site were applied at the end of May 1989. Short-shoot needle of tamarack and current and one-year needles of black spruce were sampled bi-weekly from 12 June to 15 October, 1989. Drainage and fertilization modified the foliar phenology of tamarack. Budbreak and senescence of needles were delayed on the drained site. N-fertilization delayed senescence of tamarack needles for two weeks on the undrained site. Needle mass of short-shoots of tamarack and current needles of black spruce increased during needle expansion on both sites. During needle maturation, current needle mass of black spruce increased on both sites in all treatments with greater increase in N-fertilized plots. N-fertilization increased foliar N of both species on both sites with greater increase on the drained but decreased foliar P and K throughout the season. PK-fertilization increased P and K contents and concentrations of tamarack on the drained site and of current and one-year-old needles of black spruce. For tamarack, drainage without fertilization increased rates of efflux (negative value) of foliar N, P and K. N-fertilization increased influx of N and P during needle elongation and expansion, i.e. phases 1 and 2, respectively. During needle senescence, efflux of N and K on the drained site were greater in N-fertilized plots than in N0PK plots. For black spruce, drained without fertilization resulted in an influx of P and K and efflux of N. Additionally, N-fertilization increased influx of P in the undrained site during needle expansion.