16A.17
S,N - The economics of site preparation and its implications for forest policy
C.D.B. Hawkins, University of Northern British Columbia, Prince George, BC, Canada; and T. W. Steele and T. Letchford
A current trend in forest management is away from intensive regeneration practices in favor of silvicultural prescriptions that are considered to be lighter on the land. This study examined the current condition and projected yields of nine different site preparation treatments. The study was located in central British Columbia on two ecologically similar sub-alpine sites. Both sites were winter logged in 1981-82 using conventional harvesting methods. Treatments varied in intensity and included: raw planting (i.e., no site preparation); inversion of the LFH layer (scalping); mounding with 6-, 12-, and 24-cm mineral caps; chemical site preparation; chemical brushing; and combinations of mounding (24-cm) and chemical site preparation and mounding (24-cm) and chemical brushing. Chemical treatments consisted of an application of glyphosate at the rate of 2.25 kg of active ingredient per ha. All treatments were established in August 1983 with the exception of brushing which occurred in August 1985 when the plantation was 2 years old. Treatments were manually planted in the spring of 1984 with 2+1 bareroot transplant interior spruce seedlings (Picea glauca (Moench) Voss. X P. engelmannii Parry ex Engelm.). Tree survival, height, diameter at breast height (DBH), and condition were assessed in 1998 when the treatments were 15 years old. Stand development was projected for two rotation lengths - 75 and 150 years - using the TIPSY v3.0b growth and yield model and assuming an initial stand density of 1,400 seedlings per ha. By Age 15, significant differences in stand condition had emerged. Seedling survival was markedly poorer on the raw planted treatments, ranging from 25 to 65%. In contrast, the more intensive treatments of mounding and chemical site preparation and mounding and brushing had mean Age 15 survival rates of 96 and 100%, respectively. Moreover, the trees growing on the prepared sites were on average 1m taller and 3cm larger in DBH than the raw planted seedlings. Growth and yield simulations projected considerable differences in stand development between the unprepared and prepared sites. At Age 75, estimated timber yield ranged from 361 to 559 m3ha-1 for the mechanical and chemical site preparation treatments versus 197 to 286 m3ha-1 for the raw planted treatments, approximately a two-fold difference. This relative difference in timber volumes between treatments persisted throughout the longer rotation age of 150 years. Land expectation values (LEV) were calculated for each site preparation treatment assuming a real discount rate of 4%. Although the mounding and brushing treatment yielded the largest projected timber volume, it was not the most cost effective. Specifically, the high cost of stand establishment and tending was not offset by greater timber yields and revenues. The largest financial returns were associated with the 6-cm mounding treatment and the chemical site preparation treatment, each having LEVs of 917 and 991 CDN$ha-1, respectively, at a 75-year rotation age. In comparison, the LEVs for raw planting ranged from -391 to 229 CDN$ha-1. Collectively, these results suggest that moderate investments in site preparation may lead to a more efficient allocation of resources and a greater future timber supply.
Session 16A, Other
Wednesday, 9 October 2002, 1:30 PM-1:30 AM
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