Subproject Summary

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Introduction:

Vegetation competition can have a significant impact on conifer survival and growth. In British Columbia over 60,000 ha of forest land are brushed annually to ensure the successful establishment and growth of free growing forests (B.C. Ministry of Forests 1997). During 1995-1996 approximately 37,000 ha were manually brushed in the province.

With the increase in public concern over the use of pesticides, manual brushing has become the most common and most expensive method of brushing forest plantations. The increased use of manual brushing as a means of reducing the impact of vegetation on conifer survival and growth has created a need for knowledge on the effectiveness of manual brushing.

Information is required on the effects of timing of manual brushing treatments as well as the frequency and minimum size of the brushed area. This information is necessary for forest managers to make informed decisions regarding manual brushing as a vegetation management treatment option.

Objectives:

• To provide detailed physiological information on seedling response to the time of manual brushing treatments.

Treatments:

Layout:

• 600 spruce seedlings were located, tagged, mapped and randomly assigned to one of the three time of manual brushing treatments.
• All vegetation within a one meter radius of each seedling was manually cut with a machete or a cutting saw.
• Seedlings had been selected at a minimum distance of 2.5 m to avoid any overlapping treatment areas.
• Brushing treatments were applied in 1994, 1995,  and 1996.
• At select dates, 24 seedlings from each treatment wer measured for height, diameter and crown width. Vegetation assessments and seedling fluorescence measurements were collected prior to destructive sampling.
• In the laboratory, seedlings were dissected into needles, shoots and roots for dry weight determination.
• Needle area determined by volume displacement and regression analysis.
• A total of 9 harvest dates were planned over 5 years to assess spruce seedling growth response to brushing treatments.

Sites:

1. Bigger Creek

Major Findings:

Vegetation competition was composed primarily of E. angustifolium and R. parviflorus with minor components of various low shrubs and herbs. The vegetation however did not develop cover levels necessary to produce a high competition environment. Vegetation cover did not reach levels necessary to significantly affect seedling survival however, as the seedling results suggest vegetation was at a level sufficient to affect spruce seedling growth.

The early and late summer brushing treatments significantly reduced total cover and competition index.

There were no significant treatment differences found in spruce seedling height at any harvest date. Early summer brushing did allow for an increased diameter growth during the summer months however, seedling diameter appeared to have reached a maximum by August restricting further diameter growth and allowing the other two treatments to narrow the diameter development gap which occurred during the summer months.

References and Publications (Click on Highlighted References to Obtain an Electronic Copy in PDF Form):

Harper, G. 1998. Physiological Component of the Nelson Forest Region Multifactor Manual Brushing Study - Hybrid spruce response to time of manual brushing in the ICHmw - a detailed growth analysis. DRAFT. Fourth year results progress report. B.C. Ministry of Forests, Research Branch, Victoria.

Harper, G. 1996. Physiological Component of the Nelson Forest Region Multifactor Manual Brushing Trial - Bigger Creek Site. ECW Abstract. B.C. Ministry of Forests, Research Branch, Victoria.

Harper, G., P.G. Comeau, J. Pollack, and C.F. Thompson. 1995. Physiological Component of the Nelson Forest Region Multifactor Manual Brushing Study - Destructive sampling to determine the effects of manual brushing on the physiology and growth response of conifer seedlings. Working Plan. B.C. Ministry of Forests, Victoria.

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Last Updated: May 29, 1998.