The influence of mountain alder on the growth, nutrition, and survival of black spruce and Sitka spruce in an afforested heathland near Mobile, Newfoundland

Abstract

The natural invasion of mountain alder (Alnuscrispa (Ait.) Pursh) into monoculture plantations of black spruce (Piceamariana (Mill.) B.S.P.) and Sitka spruce (Piceasitchensis (Bong.) Carr.) afforded an opportunity to assess the effects of mountain alder on soils, and on the growth, nutrient status, and survival of spruce in eastern Newfoundland. The plantations were established on ploughed Kalmia–Vaccinium heath in 1968–1969. Significant increases in the growth of spruce were associated with the presence of high densities of mountain alder in the two plantations studied. The increases began 3–6 years after the invasion and establishment of mountain alder. Estimated nitrogen (N) contributions to each plantation from mountain alder leaf litter fall were approximately 50 kg•ha−1•year−1. Spruce foliage N content was 10–15% higher in high-density mountain alder (HD-alder) plots than in low-density mountain alder (LD-alder) plots, but other foliar nutrient concentrations were low and possibly deficient in the HD-alder plots. Development of a litter fall–humus layer was observed in HD-alder plots but not in LD-alder plots; however, B-horizon soil-N values did not differ significantly between HD-alder and LD-alder plots. The mountain alder invasion did not reduce the densities (stems/ha) of spruce. Additional studies on the autecology of Alnus spp. native to Newfoundland, and on alder-spruce interaction are recommended to further the development of an adequate ecological basis for heathland and peatland afforestation in the region.