Growth of 10 Tree Species in Relation to Location and Microclimatic Gradients in a Strip Shelterwood

Strip shelterwood systems are used in some areas to favour establishment of intolerant and moderately tolerant tree species or to facilitate harvesting. There is substantial variation in microclimate within cleared strips, which can influence survival and growth of regeneration. The growth of the established regeneration depends on the microclimate (light, soil moisture, air and soil temperature) at different locations in gaps. This poster presents results from a study being conducted at Nakusp in Southern BC, Canada. The purpose of this study is to improve our understanding of the microclimatic pattern after gap creation and its influence on the growth of planted seedlings of 10 native tree species. Preliminary results, collected 13 to 14 years after planting, show gradual increase of light and air temperature from the south to the north edge of the gaps. Soil moisture stress also increased from the south to the north edge. Species are showing variable growth response to these gradients. Shade intolerant species performed better at the centre and north edge of the gap, while shade tolerant species have survived and established well under the canopy and near the edges. Among the tree species evaluated, Western hemlock and Engelmann spruce were best suited to the south edge and in the intact forest, while Douglas fir performed best at north edge and inside the opening. Regardless of their shade tolerance classification, all the species grow best near the centre of the opening, where light levels are highest