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| You are here: Research Branch > Stand Management > Fertilization > Maximum Productivity > Background Maximum Productivity Study- Background - |
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A smaller timber harvesting
land base, combined with age class imbalances in the timber inventory, are
creating serious timber supply challenges for the forestry sector in the
interior of British Columbia. Without strategic intervention, significant
mid-term timber supply shortfalls and declines in long-term harvest levels
are forecast for many interior forest management units. Increasing the
productivity and accelerating the development of young, managed forests is a
primary objective of several timber supply mitigation strategies being
developed for interior Timber Supply Areas and Tree Farm Licences to improve
the amount, and timing, of future harvests.
Fertilization is the most proven method for increasing harvest volume and accelerating the operability of established stands. As such, fertilization is widely viewed by forest planners and practitioners as a potentially valuable tool for mitigating "pinch points" in the mid-term timber supply caused by age class imbalances, and for increasing long term harvest levels. Accelerating stand development by fertilizing may become an especially important strategy in the B.C. interior given the huge negative impact of mortality caused by the mountain pine beetle on mid-term timber supply. During the past 20 years, the B.C. Ministry of Forests has sponsored extensive research to determine the nutritional status of interior forests and to document the effectiveness of "conventional" fertilization (i.e., a single fertilizer application) on improving stand growth across a wide range of species and sites. These studies have confirmed that nitrogen (N) deficiencies are widespread throughout the region, and that N additions often have a substantial positive effect on tree and stand growth. Other nutrient deficiencies, either induced or aggravated by N fertilization, have also been implicated as factors limiting the growth response of some N-fertilized interior forests. Recent studies have confirmed that growth responses may be enhanced if sulphur (S) and/or boron (B) is combined with N in fertilizer prescriptions. A single fertilizer application typically produces only a temporary increase in tree and stand growth (usually 6 to 9 years). However, fertilization research in other forest regions has demonstrated that sustained growth responses, and large reductions in rotation length, are achievable by repeatedly fertilizing young stands. For example, the growth of Norway spruce in Sweden has been doubled or tripled by frequently applying balanced fertilizers. Swedish growth projection models estimate that rotation lengths of Norway spruce may be shortened by 20 to 30 years in the south and by 40 to 60 years in the north by repeated fertilization. In the interior of British Columbia, productivity gains and accelerated stand development of similar magnitude would be of huge benefit in addressing timber supply challenges such as the amount, and timing, of future harvests. Long-term growth response data from area-based growth and yield field experiments are needed to document the potential impacts of "high input" silviculture on the growth and development of interior managed forests so that realistic expectations can be included in forest level analyses and mitigation strategies. However, increased timber production at the expense of wood value and ecosystem health is clearly not a desirable outcome. The potential detrimental impact of rapid growth on wood quality clearly needs to be evaluated, as do the effects of large nutrient additions on above- and below-ground timber and non-timber resources. The Ministry of Forests, Research Branch established nine "maximum productivity" field installations (six lodgepole pine and three interior spruce) in 9- to 15-year-old plantations and juvenile-spaced, harvest-origin stands between 1992 and 1999. One of the pine installations (inst. 8) was subsequently abandoned due to excessive red squirrel damage. The three spruce installations were established in three different subzones of the Sub-Boreal Spruce (SBS) biogeoclimatic zone, representing a broad range of climatic conditions. Three of the lodgepole pine installations were also established in the SBS zone, while the other two remaining pine sites are in the Engelmann Spruce–Subalpine Fir (ESSF) and Montane Spruce (MS) biogeoclimatic zones. The objectives of the "maximum productivity" study are to determine:
These objectives are being achieved through the coordinated efforts of an inter-disciplinary team of scientists and research technicians. Rob Brockley (Research Silviculturist, Ministry of Forests) is the project leader. |
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Last Modified: 2007 APR 20. Ministry contact: Frank van
Thienen
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