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Conifer-regeneration failure is often observed on sites invaded by ericaceous shrubs. In northeastern Quebec, Canada, these sites are frequently characterized by dense Kalmia angustifolia L. – Rhododendron groenlandicum (Oeder) K.A. Kron & Judd cover. Such failures are potential consequences of nutrient limitation, allelopathy, or low soil temperatures. Conversion of productive forests into heaths poses a threat to the maintenance of forest productivity and biodiversity. We evaluated scarification, spot fertilization, and increased seedling foliar N concentration as treatments to promote planted black spruce (Picea mariana (Mill.) BSP) seedling survival and growth. We measured seedling, vegetation, and soil responses to the treatments for 5 years following planting. Scarification had positive impacts on seedling growth: the differences between scarified and unscarified plots increased over time, and double-pass scarification proved slightly more effective than a single-pass treatment. Responses to scarification were enhanced when seedlings were fertilized. A slow-release fertilizer with micronutrients proved slightly more effective than the 26N–12P–6K formulation; the latter also induced higher mortality than the former or no fertilizer. Gains due to increased N concentrations based on nursery practices were significant but short-lived. Our results demonstrate how silviculture and nursery practices can be used for resetting the secondary succession where ecosystem retrogression is observed following K. angustifolia – R. groenlandicum invasion. [ABSTRACT FROM AUTHOR]

Genetic diversity was studied in four Canadian ecological populations, each corresponding to a Canadian ecozone, of Chondrostereum purpureum, including 93 isolates of various host origin. Pseudo-allelic frequencies were estimated at each of 22 putative RAPD loci by scoring for presence or absence of amplicons in haploid mycelial cultures. The analysis of the hierarchical population structure did not reveal any trend with regard to ecological or host origin. Total gene diversity (HT+ = 0.288) was mostly attributable to diversity within populations (Hst = 0.269). In addition, the AMOVA analysis detected most of the molecular variability within subpopulations (89.3%; P < 0.001) whereas a significant (7.3%; P =0.001) proportion of the gene diversity was found among subpopulations, within ecozones. The results indicate that C. purpureum is a highly heterogeneous pathogen with a continuously distributed population across Canada (Gst = 0.048) and underscore the importance of considering the population structure in the process of its registration as a microbial control agent. A genotype isolated in either central of eastern Canada (ecozones 2,4, and 5 populations) and selected for its potential as a biophytocide should be considered indigenous in any of these regions of intended use. [ABSTRACT FROM AUTHOR]