Effects of nutrient removal by harvesting practices and fertiliser addition on end-of-rotation radiata pine wood quality

Abstract

With intensification of forest management, there has been increasing focus on the impacts of harvest residue removal on tree growth and long-term site productivity. The intensity of harvest removals, which has a direct impact on the available nutrient pools, influences tree growth and are also likely to impact the quality of wood formed. This study focused on the effects of harvesting residue removal practices (whole tree + forest floor, whole tree and stem only) at the end of the previous rotation and repeated fertiliser addition during the current rotation on selected wood quality attributes. Growth, wood density and standing tree acoustic velocity data were collected from almost 600 radiata pine (Pinus radiata D. Don) trees from long term site productivity trials across New Zealand (Woodhill, Tarawera and Berwick Forests). A sample of 116 trees were felled to obtain detailed wood quality measurements on logs and cross-sectional discs at different heights along the stem. There was little or no effect of different levels of harvesting removal on any of the measures of wood quality. However, repeated fertiliser addition throughout the course of the rotation (up to 3200 kg N ha−1 at Woodhill Forest) did result in adverse impacts on wood density, stiffness, branch size and heartwood content. The degree to which these affect returns to forest growers and end-product performance will depend on the market segment that logs are being sold into. It is recommended that nutritional strategies aimed at increasing forest productivity should incorporate studies to evaluate their potential adverse impacts on wood quality.