Stand management treatments (e.g., thinning, fertilization) and regimes (planting density, post-thinning density, and fertilizer prescriptions) have large potential impacts on the amount, size, value, and timing of timber harvested from managed forests in the B.C. interior. This project continued the scheduled re-measurement, analysis and reporting of an extensive network of previously established stand management research installations throughout the B.C. interior. Published project deliverables for 2003/04 have provided several valuable interim results. Building on the results from previous studies, the effects of boron (B) and sulphur (S) on the nutrition and growth of lodgepole pine in the B.C. interior have been more clearly defined. Pre-fertilization foliar analysis was shown to be a useful tool for identifying stands that are either B deficient or at risk from N-induced B deficiencies following fertilizer operations. The ability of a small amount of added B to improve the health and growth of trees over a prolonged period was also clearly demonstrated. Previous studies have implicated S deficiency, either induced or exacerbated by N fertilization, as a major factor limiting the growth response of N-fertilized lodgepole pine in the B.C. interior. Results reported in 2003/04 reduce uncertainty regarding the choice of appropriate sources and rates of S to include in fertilizer prescriptions for S deficient sites. Published interim results from another study document the effects of differing levels of Sitka alder retention on the development of retained alder and on the growth and foliar nutrition of young, naturally regenerated lodgepole pine. Given the small absolute differences in growth of lodgepole pine among the various alder retention treatments after 6 years, forest practitioners can likely assign a low priority to the control of Sitka alder in the SBS biogeoclimatic zone. The effect of alder density on lodgepole pine foliar N was strongly linear, with the highest N levels measured in the high alder retention treatment. However, the positive impact of alder retention on foliar N resulted in probable imbalance of N relative to S and other nutrients. The published interim results from several lodgepole pine thinning trials in the B.C. interior clearly demonstrate the need for forest managers to consider the trade-off between individual-tree piece-size and per-hectare yield when prescribing thinning treatments. Despite larger and faster growing trees at the wider spacings, both stand basal area and stand total volume were generally inversely related to spacing level. However, interim results also demonstrate how juvenile spacing can accelerate the accumulation of merchantable volume, thereby shortening technical rotations. As such density control may be a useful technique for addressing age-class imbalances in the timber supply or for reducing the risk of catastrophic losses to pests, such as mountain pine beetle, which normally attack older stands. The thinning study is also providing valuable insight into the degree to which thinning may increase some risks and reduce others associated with managing lodgepole pine.
Robert Brockley et al.
Brockley, Robert P., Sanborn, Paul T.; Johnstone, Wayne D.; van Thienen, Frank J.. 2004. Effects of nitrogen and boron fertilization on foliar boron nutrition and growth in two different lodgepole pine ecosystems. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report