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Dominant understorey shrubs can interfere with tree recruitment and affect forest succession. In boreal forests of eastern Canada, Kalmia angustifolia grows vigorously dominating post-harvest black spruce (Picea mariana (Mill.) BSP) forests and interferes with tree regeneration. Kalmia is a dominant understorey in all stages of forest development, but its response to canopy light level is unknown. We studied the morphological and physiological responses of Kalmia in open sun (control) and experimentally low, medium and high shades allowing 100, 60, 32 and 19 per cent of full sunlight representing 0, 40, 68, and 81 per cent shade, respectively. We tested the hypothesis that Kalmia responds positively to moderate shade by adapting morphologically with larger leaf area and fewer flowering shoots and physiologically by increased stomatal conductance, photosynthesis and foliar nitrogen than low or high shade. We found significantly increased leaf area, specific leaf area and decreased flowering shoots with increasing shade. Kalmia aboveground biomass was 31 per cent higher in low shade and 22 per cent lower in high shade compared with control. The highest maximum photosynthetic capacity (Amax) of Kalmia (9 µmol CO2 m−2 s−1) was found in control (full sunlight) and the lowest (5 µmol CO2 m−2 s−1) in the medium-shade treatment. We concluded that Kalmia adapts to moderate shade by morphological plasticity, reproductive trade-off (avoiding sexual reproduction) and physiological acclimation to low light. [ABSTRACT FROM AUTHOR]

Labrador, Canada is the last relatively undeveloped landmass of Boreal and subarctic Canada. Its land area is over 288,000 km2, with less than 1% developed, and a human population of below 30,000. Labrador is greater than 60% forest- and woodland-covered and over 30% tundra, soil and rock barrens. We review the ecology and distribution of forests, woodlands, and related vegetation of Labrador within the context of climate, forest site index, landform, soils, and disturbance. Recent ecosystem management through a public planning process with emphasis on past and future comanagement and development with traditional and western scientific principles is currently underway. Plant–animal interactions, traditional uses by aboriginal groups, and early history are also reviewed. [ABSTRACT FROM AUTHOR]