The preliminary effects of different regimes and frequencies of repeated fertilization on foliar nutrition and growth of eight young lodgepole pine and interior spruce forests in north-central British Columbia are reported. At least 6 years of growth measurements have been obtained from seven of the eight maximum productivity installations. These results indicate that the repeated fertilization of young managed forests may be a potentially viable strategy for addressing timber supply challenges in the interior of British Columbia. Young spruce plantations are apparently particularly well suited to intensive forest management. Although four of the five lodgepole pine installations have produced significant growth gains following periodic (every 6 years) and yearly fertilization, the responses to date have been more variable and consistently smaller than those obtained at the spruce study sites. In the lodgepole pine installations, annual applications of nitrogen and other nutrients produced 6-year relative stand volume increments that ranged from 2% lower to 120% higher than control values. In contrast, 6-year stand volume increases of 213-280% were obtained from yearly fertilization at the spruce study sites. In one spruce stand, 9-year stand volume increment in the most intensively fertilized treatment was almost four times larger than in the unfertilized stand. This represented an absolute volume gain of 45 m3/ha. Lodgepole pine growth responses appear to be inversely related to fertilization intensity. Foliar nutrient imbalances and growth disruptions have apparently been induced by large, and frequent, nitrogen additions at some lodgepole pine study sites, despite the frequent inclusion of other macro- and micronutrients in fertilizer prescriptions for repeatedly fertilized treatment plots. Conversely, the largest spruce responses have been associated with the most intensive fertilization treatments. It is too early to project the potential impacts of intensive fertilization on harvest volume and/or rotation length of managed interior spruce and lodgepole pine forests in north-central British Columbia. However, preliminary growth responses from maximum productivity research installations appear to be tracking along pathways similar to the Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L.) optimum nutrition studies in Sweden. Growth projection models estimate that the rotation length of Norway spruce may be shortened by as much as 40-60 years by frequently applying balanced fertilizers. Continued monitoring of stand development in all maximum productivity installations is important, to see whether these early species growth trends continue, and to determine how closely growth gains from periodic fertilization (i.e., every 6 years) of spruce and pine will approximate the responses achieved by yearly nutrient additions.
Rob Brockley...[et al.]
Berch, Shannon M., Brockley, Robert P.; Battigelli, Jeffrey P.; Hagerman, Shannon M.; Holl, Brian; Simpson, David G.; Amponsah, Isaac G.; Lieffers, Victor J.; Comeau, Philip G.; VanAkker, Lara; Alfaro, René I.; Sanborn, Paul T.. 2005. Effects of intensive fertilization on timber and non-timber resources. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report