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Degradation of boreal forest soil fertility caused by the invasion of Kalmia angustifolia : a forest management problem

Summary

Abstract of the paper presented to the 15th International Congress of the International Soil Conservation Organization: "Soil and Water Conservation, Climate Change and Environmental Sensitivity". May 18-23, 2008. Budapest, Hongrie. 6 p. In Canada's boreal forest, black spruce seedling growth is sometimes kept in check by the invasion of the ericaceous shrub, Kalmia angustifolia. A series of experiments were devised to elucidate the mechanisms by which Kalmia gains a competitive advantage over spruce. Soil incubations and bioassays revealed that humus formed under Kalmia produced very little mineal N. Kalmia was able to uptake soil N from this humus whereas black spruce seedlings could not. Kalmia foliage produced 5x more tannins than spruce needles, and the addition of purified Kalmia tannins to soil resulted in lower mineral N accumulation with no sign of this being provoked by microbial immobilization. Tannin-protein precipitates formed with Kalmia tannins contained more N than those produced with spruce tannins. These protein-tannin complexes were more easily metabolized by mycorrhizae associated with Kalmia than those associated with spruce. Kalmia tannins were shown to inhibit important soil enzymes (acid phosphatase, amidase and b-glucosidase), and these effects were concentration-dependent. Soil enzyme inhibition was higher when Kalmia leaves were added to forest humus, and a field study demonstrated a negative relationship between % Kalmia ground cover and soil enzyme activity. Silvicultural trials showed that fertilization had a positive effect on black spruce growth, but still better growth and improved soil properties were obtained by the complete eradication of Kalmia. Scarification is a promising management option to restore fertility on Kalmia-dominated cutovers.

Sector(s): 

Forests

Categorie(s): 

Conference and Presentation

Theme(s): 

Forestry Research, Forests, Silviculture

Author(s)

BRADLEY, Robert, Gilles JOANISSE, Philippe LEBEL, Nelson THIFFAULT et C. PRESTON

Year of publication :

2008

Format :

Paper

Keywords :

sheep laurel, black spruce, competition, allelopathy, soil fertility, nutrients, silviculture and yield of plantations, sylviculture et rendement des plantations, Kalmia angustifolia, Picea mariana, tannins

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