GROWTH ANALYSIS OF RESPONSES BY PLANTED WHITE-PINE AND WHITE SPRUCE TO CHANGES IN SOIL-TEMPERATURE, FERTILITY, AND BRUSH COMPETITION

A factorial field experiment, located near Chalk River, Ontario, Canada, was used to test the effects of brush competition, fertility, and soil temperature on first and second-season growth of planted white pine and white spruce. Soil temperature, soil moisture tension, and photosynthetically active radiation were continuously monitored to quantify treatment effects. Foliar nutrition was assessed on nursery stock pre-planting and on current and previous foliage age classes after one growing-season. Measurement of biomass components and leaf surface area was carried out after one growing-season. Increasing soil temperature improved the net photosynthetic rate (Pn) of both species in the first growing-season. Relative growth rate (Gr) of both species was positively affected by the soil temperature treatments but, because of changes in carbon partitioning and foliage morphology, was not directly related to Pn. Fertilization and brush control treatments caused compensating adjustments in morphology and biomass allocation that did not affect Gr in the first season. In the second season, environmental conditions changed and brush competition increasingly influenced growth. Despite the changes in environmental conditions during the plantation establishment period, the ability of trees to successfully adjust to environmental stress increased from the first growing-season to the second. © 1990.