Less Site Preparation Will Lower Timber Yields

Planting trees without site preparation will end up costing the province of British Columbia considerably in future timber production.

Projections show that small investments in site preparation could garner substantially greater financial returns from timber for the provincial government.

Raw planting, that is planting trees on logged areas with no site preparation, results in one-third to one-half the wood volume at the typical 75-year rotation age than the volume produced from cutblocks treated mechanically or chemically before planting.

In light of these results, the sharp trend away from site preparation in BC has alarming implications for future timber supply. Between 1992 and 2002, the area treated each year declined 69 percent, to 53,000 ha, comprising 39 percent of BC's forest land planted in 2002.

The timber yield and financial analyses are based on studies of 15-year-old spruce stands in the Sub-boreal Spruce biogeoclimatic zone southeast of Prince George, BC. Trees on prepared sites survived better, grew one metre taller, and almost 3 cm more in diameter than raw planted seedlings. Scarifying the ground, then building mounds generally produced the best results.

Costs for treatments varied widely, and due to inadequate tree survival on one site, raw planting was not always cheapest. Site preparation expenses were offset in the short term by enabling compliance with provincial free-growing and green-up requirements one or more years sooner.