Extension Note
41
Conifer Response to Brushing Treatments: A Summary of British Columbia Data
December
Ministry contacts: Philip G. Comeau, Balvinder S. Biring, and George J. Harper B.C. Ministry of Forests Research Branch P.O. Box 9519, Stn Prov Govt Victoria, BC V8W 9C2 (250) 357-3299 email:
[email protected]
This extension note summarizes available information on the consequences of brushing treatments to conifer performance. It provides a brief review of information from neighbouring areas and a summary of results from studies conducted in British Columbia. Introduction Brushing treatments are widely used in British Columbia forests to control non-crop vegetation in order to improve the survival and growth of tree seedlings, and to accelerate or ensure development of a free-growing
plantation. The total amount of public forest land brushed annually has increased from ha in to ha in (B.C. Ministry of Forests ) (Figure ). During , manual treatments (including manual and motormanual cutting and bending and girdling treatments) were used to treat ha, at a cost of $ million, representing % of the area brushed (Figure ), and % of brushing expenditures. In , herbicide treatments were used to treat ha (% of the area brushed), and sheep browsing was used to treat ha (%). According to the B.C. Ministry of Forests () the cost of manual treatments averaged $/ha, groundapplied herbicide treatments averaged $/ha, aerially applied herbicide
figure 2 A summary of brushing
figure 1 Brushing activities on public forest lands in British Columbia have more than tripled since 1985. (Source: B.C. Ministry of Forests 1998.)
treatments used in British Columbia in 1996 (72 500 ha were treated in 1996). (Source: B.C. Ministry of Forests 1998.)
Ministry of Forests Research Program
treatments averaged $/ha, and sheep browsing averaged $/ha (for each individual treatment entry). Survival and growth responses to brushing depend upon the nature and intensity of competition, crop tree size and condition at the time of treatment, and the level and duration of competition control achieved by treatments. In some circumstances, such as in areas where dense stands of red alder develop, conifers may be virtually excluded after – years without treatment (Walstad et al. ). In their summary of results from more than studies from various locations around the world, Stewart et al. () report increases of up to % in stand volume over the short term (up to years after treatment). Ten-year growth responses to sheep browsing in a coastal Oregon Douglasfir plantation showed a height growth increase of % and diameter increase of % (Sharrow et al. ). In the northern Rocky Mountains of the United States, Boyd () reports large increases in survival and growth of Douglas-fir, ponderosa pine, and lodgepole pine – years after control of grasses and herbaceous vegetation using glyphosate or hexazinone. Height was typically .–. times that of untreated control, and diameter ranged from . to . times that of untreated seedlings. Several studies in the southeastern United States have also demonstrated growth responses resulting from control of woody and herbaceous vegetation (e.g., Oppenheimer et al. ; Colbert et al. ; Britt et al. ). In New Brunswick, MacLean and Morgan () report that balsam fir had % greater stem volume and were % taller than untreated trees years after manual release treatments. Herbicide application (,-d +,,-t) resulted in stem volumes that were .–. times those of untreated trees years after treatment. In a study done in Ontario, Sutton () reports that weed control during the first years after planting re-
sulted in increases in average tree stem volume of white spruce at age of between and %. This extension note summarizes information reported from vegetation management trials conducted in British Columbia that provide data on conifer seedling survival or more years after treatment. This summary is restricted to commonly used treatments: manual brushing treatments, single applications of glyphosate herbicide, and sheep browsing (, , or years). A more detailed discussion of treatment options is provided by Hart and Comeau (), Biring et al. (), and Boateng (). Growth responses to operationally applied treatments are likely to be smaller than those reported for research trials. Results from research trials illustrate potential growth gains under ideal conditions and are not truly representative of operational brushing because: ) research trials tend to focus on sites where serious problems exist or are anticipated; ) research sites tend to be more uniform than operationally treated areas; and ) research treatments are generally much more effective and more uniform, due to more careful control of application and timing and a greater investment in time and energy in a small area. Results from remeasurement of operationally treated areas are less likely to reflect these limitations. Interactions between Conifer Seedlings and Neighbouring Vegetation When neighbouring vegetation occurs with sufficient density, cover, and height, it can adversely affect survival and growth of tree seedlings by competing for light, water, and/or nutrients, by causing physical damage, by altering soil and air temperatures, or by harbouring rodents or other organisms that damage young trees. Herbs, shrubs, and broadleaf trees serve a number of important roles in
the ecosystem that must be considered in the development of any treatment prescription. These include: ) providing food and shelter for wildlife; ) reducing soil erosion and conserving nutrients on site; ) enhancing soil nutrient availability through nitrogen fixation (Sitka alder and red alder) and other processes; ) protecting conifer seedlings from frost and sunscald; and ) reducing insect and disease problems (e.g., weevil damage to spruce; root disease). When deciding if treatments are warranted, it is important to evaluate the potential benefits against the potential longerterm impacts of brushing. Broadleaf trees such as paper birch, trembling aspen, black cottonwood, balsam poplar, red alder, and bigleaf maple can serve as a nurse crop and can reduce problems associated with root disease, weevil damage, and frost damage. Cutting or spacing of birch is likely to increase Armillaria ostoyae damage to susceptible conifers (Douglas-fir, spruces, and pines). Field studies in the southern interior indicate that cutting of birch may worsen root disease (Armillaria) problems for susceptible conifers, while herbicide treatments used to control birch may not. On sites with Armillaria it may be best to allow mixtures to develop and grow naturally, with minimal intervention. (This will result in a natural mixedwood stand, and reduces the risk of financial losses by minimizing expenditures on such sites.) When retention of a broadleaf component is desirable because of its contributions to forest health, nutrient cycling, biodiversity, and long-term sustainability, reduction of broadleaf densities, rather than complete removal, may be an option for achieving both objectives. There is substantial opportunity for increased utilization of broadleaf tree species in British Columbia. In some areas, managing for broadleaves may provide better financial returns than expending funds on the conversion of
broadleaf stands to coniferous stands (Vyse ). Response of British Columbia Conifers to Brushing Treatments Crop tree responses to brushing can include: ) physical and physiological damage resulting from treatments; ) increases or decreases in survival; and ) increases or decreases in height and diameter growth rates. Seedling damage Damage to seedlings may occur following some treatments. For example, herbicide treatments using glyphosate may damage exposed leaders and needles of western hemlock and western redcedar, and may under some circumstances also cause damage to Douglas-fir and spruce. In some cases, even damaged seedlings respond favourably to vegetation control, and can end up being larger than untreated (and undamaged) seedlings (Harper et al. ). Poor management of livestock can result in damage to crop seedlings due to browsing and trampling if browsing projects are not managed properly (e.g., Sharrow et al. ; Newsome et al. ). When crop seedlings are not readily visible but are buried in vegetation, there is substantial risk of damage from cutting tools. Roberts () reported that % of the young Douglas-fir seedlings sampled across a number of sites in Oregon were damaged by chainsaws or falling brush. Holmsen and Whitehead () report that % of seedlings that were obscured by vegetation at the time of treatment were damaged, while % of seedlings that were visible were damaged. Survival Statistical analysis of survival data is available for only a limited number of replicated trials in British Columbia.
figure 3 Glyphosate is the herbicide used most commonly for silvicultural purposes. It is generally applied during late summer using backpack sprayers or aircraft.
Two studies indicate statistically significant effects of brushing treatments on conifer survival (Table ). One trial shows a small but significant decrease in survival of lodgepole pine years after manual brushing of a mixed hardwood community, due to Armillaria root disease (Heineman et al. ). McMinn () reports a significant improvement in survival of white spruce years after manual brushing of a mixed shrub community. For the remaining entries in the table, survival differences are variable and generally small. Improvements in survival should be expected only where competition levels are high (i.e., competition exceeds survival thresholds—notably in dense herbaceous, bluejoint, and mixed shrub complexes). Most mortality appears to occur during the first few years after planting, prior to the establishment and treatment of many of the studies reported in this summary. Consequently, these data, which come predominantly from the southern interior, should be interpreted
with caution and may not be entirely applicable to other parts of British Columbia. Mechanical site preparation, prompt planting with healthy seedlings, and early brushing (when required) are generally considered to be the most effective options for promoting survival. Growth Growth responses of conifer seedlings to various brushing treatments are summarized in Table . A large proportion of the reported information comes from the southern interior; care should be used in extrapolating results from only one region too widely. Height and achievement of free-growing Height responses to brushing treatments are highly variable (Table ). Sixteen of studies (%) show significant increases in height growth following manual brushing, while two (%) show decreased height, and (%) show
no significant response. Eleven of studies (%) show increased height following glyphosate treatment, while four (%) show decreased height, and (%) show no significant response. In general, releasing conifers from low to moderate levels of vegetation cover results in little initial increase in height growth and may even result in a reduction in height growth as growth is directed into diameter increment (i.e., under low to moderate levels of competition, etiolation causes enhancement of height growth at the expense of stem diameter and crown development). Height growth responses vary by vegetation complex, crop species, treatment type, years after treatment, and amount of competing vegetation encountered (competition intensity). The largest increase in conifer height was reported by Pollack and van Thienen ()— years after application of glyphosate (at – kg ai/ha), Sitka spruce height was . times that of untreated trees. Increases in height growth as a result of brushing treatments are reported in some studies conducted in the mixed hardwood, mixed shrub, dry alder, wet alder, red alder–shrub, and willow complexes. For manual treatments, significant increases in height are reported for: two of three trials in the ericaceous shrub, five of trials in the mixed shrub, and three of eight trials in the dry alder complex. For glyphosate treatments, significant increases in height are reported for: five of six trials in the mixed hardwood, and, four of six trials in the mixed shrub complex. Mather and Simard () show the potential for substantial increases in the percentage of seedlings that are free-growing – years after manual or glyphosate treatment. However, few data are currently available concerning the impacts of brushing on achievement of free-growing requirements. Where height or survival responses to treatment are small, treatment of herbaceous or shrubby
figure 4 Sheep browsing can be an effective method for controlling herbaceous vegetation in some plantations, providing that the terrain and site are suitable, and the livestock are properly managed. However, growth responses of conifer seedlings have been observed in only one of 12 documented studies conducted in British Columbia.
vegetation may have only marginal effects on achievement of freegrowing. Control of tall-growing shrubs or broadleaves such as red alder, bigleaf maple, paper birch, trembling aspen, and cottonwood will accelerate achievement of free-growing status by crop conifer seedlings through reduction of the tall deciduous canopy (Harper et al. ; Harper et al. ; Whitehead and Harper ). Seedling diameter Statistically significant diameter growth increases were recorded in of (%) manual brushing trials and in of (%) glyphosate trials, with diameter increases ranging up to . times that of untreated seedlings for manual treatments and . times that of untreated seedlings for glyphosate treatments. Twelve years after treatment of a mixed hardwood complex with glyphosate, Biring et al. () report that root collar diameter of white spruce was . times that of untreated seedlings Only one of sheep
browsing trials reports a significant increase in diameter. Significant diameter increases resulting from glyphosate or manual brushing are documented in the fern, fireweed, mixed hardwood, mixed shrub, dry alder, wet alder, red alder– shrub, and willow complexes. In the fireweed complex, five of manual brushing trials, two of six glyphosate trials, and zero of five sheep trials report significant increases in diameter. In the mixed hardwood complex, five of manual and six of six glyphosate trials show significant increases in diameter. In the mixed shrub complex, seven of manual and seven of eight glyphosate trials show significant increases. The fact that glyphosate treatments in the mixed hardwood and mixed shrub complexes result in more consistent increases in diameter than manual treatments is likely a reflection of the longer duration and greater effectiveness of the glyphosate treatment. It is important to note that data on the effectiveness of sheep browsing are
very limited and should be interpreted with caution. There are no data currently available from the northern interior. Some of the trials included in this summary were established before the use of sheep browsing in conifer plantations had been adequately developed. Conclusions Studies done in British Columbia indicate that the growth of conifer seedlings can be improved through brushing treatments where treatment is required, where treatments are effective, and where crop seedlings are able to respond. Since most of the research presented in this summary comes from the southern interior, care must be exercised to avoid extrapolating to other areas where treatments have not been documented. Height growth responses are highly variable, with growth responses being the largest where dense broadleaf canopies were removed. Diameter increases are consistently reported following glyphosate treatment in the mixed hardwood and mixed shrub complexes, and following manual treatment in the mixed shrub complex. Studies of the effects of treatment timing in other regions indicate that growth gains are largest when treatments are applied at or just prior to the onset of competition. Delaying application of treatment can seriously compromise potential growth gains. Deloitte and Touche () estimate that, without control of competing vegetation, sustainable harvests would be reduced by as much as .%. However, the long-term yield implications of brushing are uncertain. Long-term data from permanent installations are required to document yield implications and to validate any prediction of yield increases due to brushing. The data presented in this report cannot be used to evaluate the effectiveness of the current operational brushing program since it is not known how well these studies
represent areas that are currently being treated (i.e., the studies reported here should not be considered a representative sample of operationally treated areas). Estimation of the gains accomplished by brushing treatments is limited by the lack of suitable data on the nature of sites being treated operationally (vegetation cover, vegetation height) and on the responses of crop seedlings to operational brushing treatments. Further information on responses to both operational and experimental treatments is required, particularly for the northern interior and coastal regions of British Columbia Such information should be obtained through reporting of collected data, from continuing remeasurement of study sites and monitoring installations, and through establishment of new installations to fill data gaps. There is also a critical need for studies to examine the implications of new techniques and changes in operational practices as well as for studies and tools to support improvements in vegetation management decisions. Acknowledgements The authors gratefully acknowledge the assistance provided by those who provided unpublished results and who reviewed draft copies of this summary. We are particularly grateful to Suzanne Simard for providing summaries of unpublished results from operational monitoring of treated sites in the southern interior. Funding for the publication of this extension note was provided by Forest Renewal BC (Project HQ-RE). Literature Cited Barron, D. . The effect of grass competition on tree seedling survival and growth. Interim Report —SX N. rd year results. B.C. Ministry of Forests, Nelson Forest Region, Nelson, B.C. Unpublished.
Biring, B.S., P.G. Comeau, and J.O. Boateng. . Effectiveness of forest vegetation control methods in British Columbia. Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Handbook . Biring, B.S., W.J. Hays-Byl, and S.E. Hoyles. . Twelve-year conifer and vegetation responses to discing and glyphosate treatments on a BWBSmw backlog site. B.C. Ministry of Forests, Research Branch, Victoria, B.C. Working Paper . Boateng, J.O. . Herbicide field handbook. Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Handbook . Revised. Boyd, R.J. . Conifer performance following weed control site preparation treatments in the inland northwest. In Weed control for forest productivity in the Interior West. Proceedings of a symposium. D.M. Baumgartner, R.J. Boyd, D.W. Breuer, and D.L. Miller (editors). . Spokane, Wash., Feb. –, . British Columbia Ministry of Forests. . Annual Report of the Ministry of Forests for the fiscal year ended March , . British Columbia, Ministry of Forests, Victoria, B.C. Britt, J.R., R.J. Mitchell, B.R. Zutter, D.B South, D.H. Gjerstad, and J.F. Dickson. . The influence of herbaceous weed control and seedling diameter on six years of loblolly pine growth—a classical growth analysis approach. Forest Science :–. Coates, K.D. W.H. Emmingham, and S.R. Radosevich. . Coniferseedling success and microclimate at different levels of herb and shrub cover in a RhododendronVaccinium-Menziesia community of south central British Columbia. Canadian Journal of Forest Research : –. Colbert, S.R., E.J. Jokala, and D.G. Neary. . Effects of annual fertilization and sustained weed control on dry matter partitioning, leaf
area, and growth efficiency of juvenile loblolly and slash pine. Forest Science :–. Comeau, P.G. a. Effectiveness of repeated cutting treatments in a fireweed community. Expert Committee on Weeds Research Report, Western Canada Section Meeting, Dec. –, . Winnipeg, Man. Vol. , p. . ———. b. Effectiveness of repeated cutting treatments in a mixed-shrub/ herb community: Sullivan Site . Expert Committee on Weeds Research Report, Western Canada Section Meeting, Dec. –, . Winnipeg, Man. Vol. , pp. –. ———. c. Effectiveness of repeated cutting treatments in a mixed-shrub/herb community: Sullivan Site. Expert Committee on Weeds Research Report, Western Canada Section Meeting, Dec. –, . Winnipeg, Man. Vol. , pp. –. Comeau, P.G., B.S. Biring, and G.J. Harper.. Effectiveness of repeated manual cutting for release of Engelmann spruce from mixedshrub/herb vegetation. B.C. Ministry of Forests, Research Branch, Victoria, B.C. Draft Report EP ., February , . D’Anjou, B. . Effect of timing of manual treatment on red alder regrowth and conifer response — Project .. Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Research Memo . ———. . Response of non-crop vegetation to manual cutting and glyphosate and subsequent Douglasfir growth in the coast-interior transition. EP: a progress report. B.C. Ministry of Forests, Vancouver Forest Region, Vancouver, B.C. Deloitte and Touche Management Consultants. . Economic assessment of vegetation management in B.C. forests. Contractors Report prepared for B.C. Ministry of Forests, Silviculture Branch, Victoria, B.C. DeLong, D.L. and C.F. Thompson. . Efficacy testing of hexazinone
(Velpar - L ) and a manual treatment on cottonwood and thimbleberry in the ICH mw — SX N. B.C. Ministry of Forests, Nelson Forest Region, Forest Sciences, Nelson, B.C. Technical Report TR-. Harper, G.J., B.S. Biring, and J. Heineman. . Mackay River herbicide trial: conifer response years post-treatment. B.C. Ministry of Forests, Victoria, B.C. Research Report . Harper, G.J., R. Whitehead, and C.F. Thompson. . A comparison of manual brushing treatments in the ICHdw at Redfish Creek: -year results from blocks -. B.C. Ministry of Forests, Victoria, B.C. Extension Note . Hart, D. and P.G. Comeau. . Manual brushing for forest vegetation management in British Columbia: a review of current knowledge and information needs. B.C. Ministry of Forests, Victoria, B.C. Land Management Report . Heineman, J., S. Simard, and J. Mather. . PROBE Summary Memo. B.C. Ministry of Forests. Kamloops Forest Region, Kamloops, B.C. Herring, L.J. . Performance of white spruce following an early glyphosate brushing and weeding treatment. Expert Committee on Weeds Research Report, Western Canada Section Meeting, Nov. , and Dec. , . Winnipeg, Man. Vol. , p. . Holmsen, S.D. and R.J. Whitehead. . Comparison of clearing-saw attachments for weeding young plantations. Forestry Canada and B.C. Ministry of Forests, Victoria, B.C.. FRDA Report No. . MacLean, D.A. and M.G. Morgan. . Long-term growth and yield response of young fir to manual and chemical release from shrub competition. Forestry Chronicle : –. Mather, J. and S. Simard. . Conifer responses to vegetation management: PROBE data summary (Kamloops and Nelson Forest Regions). B.C. Ministry of Forests,
Kamloops Forest Region, Kamloops, B.C. Unpublished draft report. Mar. . ———. . PROBE research in the southern Interior. PROBE Memos. B.C. Ministry of Forests, Kamloops Forest Region, Kamloops, B.C. McMinn, R.G. . Ecology of site preparation to improve performance of planted white spruce in northern latitudes. In Forest regeneration at high latitudes: experiences from northern British Columbia. School of Agriculture and Land Resources Management in cooperation with USDA Forest Service Pacific Northwest Forest and Range Experimental Station. Miscellaneous Report -. pp. –. Newsome, T. . Herbicide rate and timing trial in a fireweed complex on a backlog site in the ICHe subzone in the Cariboo Forest Region. B.C. Ministry of Forests, Cariboo Forest Region, Williams Lake, B.C. FRDA Project .. Progress Report. Newsome, T., B. Wikeem, and C. Sutherland. . Sheep grazing guidelines for managing vegetation on forest plantations in British Columbia. B.C. Ministry of Forests, Victoria, B.C. Land Management Handbook . Newton, M. and P.G. Comeau. . Control of competing vegetation. In Regenerating British Columbia’s forests. D.P. Lavender, R. Parish, C.M. Johnson, G. Montgomery, A. Vyse, R.A. Willis, and D. Winston (editors). University of British Columbia Press, Vancouver, B.C. Nicholson, A. . Water relations, survival and growth of Douglas-fir seedlings at a pinegrass dominated site in the Interior Douglas-fir zone of south-central British Columbia. M.Sc. thesis. Oregon State University, Corvallis, Ore. Oppenheimer, M.J., B.C. Shiver, and J.W. Rheney. . Ten-year growth response of midrotation slash pine plantations to control of competing vegetation. Canadian Journal of Forest Research :–.
Pollack, J. and P. LePage. . Roundup (gylphosate) herbicide trial at Hells Bells, Kispiox Forest District. SXR Third Progress Report. B.C. Ministry of Forests, Prince Rupert Forest Region, Research Section, Smithers, B.C. Pollack, J.C. and F. van Thienen. . Conifer release with glyphosate. Expert Committee on Weeds Research Report. Western Canada Section Meeting Dec. , , and , , Edmonton, Alta. Vol. , p. . Reynolds, P.E., D.G. Pitt, R. Whitehead, and K. King. . Three year herbicide efficacy, crop tolerance and crop growth response results for a glyphosate conifer release trial at Carnation Creek, British Columbia. In Proceedings of the Carnation Creek Herbicide Workshop, Dec. –, . Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Report , pp. –. Roberts, C.A. . Cooperative brush control study. Second year report. Report to Oregon Forest Industries Council. Unpublished. Sharrow, S.H., W.C. Leininger, and K.A. Osman. . Sheep grazing effects on coastal Douglas-fir forest growth: a ten-year perspective. Forest Ecology and Management :–. Simard, S. and J. Heineman. a. Nine-year response of Douglas-fir and the mixed hardwood-shrub complex to chemical and manual release treatments on an ICHmw site near Salmon Arm. Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Report . ———. b. Nine-year response of Engelmann spruce and the willow complex to chemical and manual release treatments on an ICHmw site near Vernon. Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Report . ———. c. Nine-year response of lodgepole pine and the dry alder complex to chemical and manual release treatments on an ICHmk site near Kelowna. Forestry Canada
and B.C. Ministry of Forests, Victoria, B.C. FRDA Report . ———. d. Nine-year response of lodgepole pine and the willow vegetation community at Ellis Creek to manual and chemical release treatments. B.C. Ministry of Forests, Kamloops Forest Region, Kamloops, B.C. Unpublished. ———. . Nine-year response of lodgepole pine and the pinegrass vegetation community at the Upper McKay Creek to chemical release treatments. B.C. Ministry of Forests, Kamloops Forest Region, Kamloops, B.C. Unpublished. Simard, S., J. Heineman, J. Mather, and D. Sachs. . Mortality results for PROBE sites. B.C. Ministry of Forests, Kamloops Forest Region, Kamloops, B.C. Unpublished. ———. . Conifer growth results for PROBE sites. B.C. Ministry of Forests, Kamloops Forest Region, Kamloops, B.C. Unpublished. Stewart, R.E. . Seeing the forest for the weeds: a synthesis of forest vegetation management. In Forest vegetation management for conifer production. J.D. Walstad and P.J. Kuch (editors). John Wiley and Sons, Inc., New York, N.Y. pp. –. Stewart, R.E., L.L. Gross, and B.H. Honkala. . Effects of competing vegetation on forest trees: a bibliography with abstracts. USDA Forest Service, Washington, D.C. General Technical Report WO-. Sutherland, C., T. Newsome, and N. Daintith. . Sheep grazing — a biological tool for controlling competing vegetation in spruce plantations. In Biocontrol of weeds: proceedings of a workshop held at the Western International Forest Disease Work Conference in Vernon, B.C., Aug. , . C. Dorworth and S.G. Glover (editors). Forestry Canada, Pacific Forestry Centre, Victoria, B.C. pp. –. Sutton, R.F. . White spruce establishment: initial fertilization, weed control, and irrigation evaluated after three decades. New Forests : –.
Thompson, C.F. . The effect of glyphosate treatments on a mixed brush community in the ICHd subzone (SX ). In Vegetation competition and responses: proceedings of the Third Annual Vegetation Management Workshop, Feb. –, , Vancouver, B.C. E. Hamilton and S. Watts (editors). Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Report . pp. –. Thompson, C.F., P. Bauer, and G.J. Harper. . Ten-year results from a motor-manual brushing trial for conifer release in the ICHdw. B.C. Ministry or Forests, Research Branch, Victoria, B.C. Unpublished file report. Vyse, A. . Should we grow mixtures of paper birch and Douglas-fir in the Interior Cedar–Hemlock biogeoclimatic zone? In Ecology and management of B.C. hardwoods. Workshop Proceedings, Dec. and , , Richmond, B.C. P.G. Comeau, G.J. Harper, M.E. Blache, J.O. Boateng, and K.D. Thomas (editors). Forestry Canada and B.C. Ministry of Forests, Victoria, B.C. FRDA Report . pp. –. Walstad, J.D., J.D. Brodie, and B.C. McGinley. . Silvicultural value of chemical brush control in the management of Douglas-fir. Western Journal of Applied Forestry :–. Whitehead, R.J. and G.J. Harper. . A comparison of four treatments for weeding Engelmann spruce plantations in the Interior Cedar– Hemlock Zone of British Columbia: ten years after treatment. Canadian Forestry Service. Information Report BC-X-.
table 1
Effects of brushing treatments on conifer survival in British Columbia
Complexa Aspen
Fern Fireweed
Subalpine herb
Mixed hardwood
Dry shrub Ericaceous shrub
Crop speciesb
Region
Assessment yearc
Replication
Untreated
Fd Pl Pl Se Sx Pl Pl Pl Se Se Se Se Se Se Sx Sx Se Se Se Se Cw Fd Fd Fd Fd Fd Fd Fd Pl Sx Sx Sx Pl Pl Se Se Se Se
K K K K,N K K K K K N N K,N K,N K K N K K K K K K K K K K K K K K K K K K K,N K N K
3 3 5 3 5 3 3 5 3 3 3 3 3 5 3 5 3 3 3 5 5 3 3 5 5 3 5 5 3 5 5 5 3 3 5 3 3 3
R U U R U R U U U U R R R U U U U U U U U U U U U R R R R U U U U R R R U U
95 100 89 96 11 76 97 100 86 61 65 94 53 97 100 97 81 31 97 78 92 100 89 94 100 94 89 94 95 100 97 92 89 80 71 76 97 94
Survival % Manual Glyphosate
Sheep
90 100 97 99 42 92 100 94 83 94 87 96 56 100 100 89 67 28 97 69 97 78 94 86 94 88 87 96 93 100 97 94 89 96 89 99 97 86
Source Simard et al. 1998 (28, 52, 100)d Mather and Simard 1998 (27–2) Mather and Simard 1998 (40–2) Heineman et al. 1999 Simard et al. 1998 (19) Simard et al. 1998 (49, 50, 65) Simard et al. 1998 (35) Mather and Simard 1998 (11–2) Mather and Simard 1998 (37–2) Mather and Simard 1997 (123) Heineman et al. 1999 Heineman et al. 1999 Simard et al. 1998 (13, 48, 109) Mather and Simard 1998 (11–2) Simard et al. 1998 (56) Simard et al. 1998 (112) Mather and Simard 1998 (13–2) Mather and Simard 1998 (38–2) Mather and Simard 1998 (42–2) Simard et al. 1998 (14) Mather and Simard 1998 (7–2) Mather and Simard 1997 (100) Simard et al. 1998 (30) Simard et al. 1998 (15) Simard et al. 1998 (21) Simard et al. 1998 (3, 12, 29) Heineman et al. 1999 Heineman et al. 1999 Heineman et al. 1999 Simard et al. 1998 (39) Mather and Simard 1998 (5–2) Mather and Simard 1998 (9–2) Mather and Simard 1998 (34–2) Coates et al. 1991 Heineman et al. 1999 Coates et al. 1991 Simard et al. 1998 (120) Mather and Simard 1998 (43–2)
Mixed shrub
Pinegrass Dry alder
Red alder
Wet alder Salal Salmonberry
Willow
Cw Fd Fd Fd Se Se Se Se Sw Sx Sx Fd Pl Pl Pl Pl Pl Sx Bg Cw Fd Fd Se Se Fd Fd Ss (1+0) Ss (1+1) Ss (1+2) Fd
N N K V K N N N P N K C N K K K K K V V V V N K V V V V V K
5 3 5 7 3 5 10 10 10 3 3 3 3 3 3 5 5 3 7 7 7 7 3 3 4 5 7 7 7 5
U U U R U R R R R U U R U R U U U U R R R R U U U U R R R U
94 92 100 98 31 86 96 100 75 61 25 36 80 100 100 100 61 100 93 97 56 88 100 100 97 97 95 96 100 100
83 97 100 89
77 28
90–100 80 95 90** 94 44 43–95
97 100 86
83 99 100 100 94 100 79–97 96 72 94–100 67 94
95 78
44 87 83 97 100 100
Simard et al. 1998 (101) Simard et al. 1998 (103) Simard et al. 1998 (16) D’Anjou 1999 (pers. comm.) Mather and Simard 1998 (38–2) Comeau et al. 1998 Whitehead and Harper 1998 Whitehead and Harper 1998 McMinn 1982 Simard et al. 1998 (123) Mather and Simard 1998 (19–2) Nicholson 1990 Barron 1989 Heineman et al. 1999 (4, 23, 55) Mather and Simard 1998 (31–2) Mather and Simard 1998 (10–2) Mather and Simard 1998 (8–1) Mather and Simard 1998 (18–2) D’Anjou 1991 B. D’Anjou 1999 (pers. comm.) B. D’Anjou 1999 (pers. comm.) D’Anjou 1991 Simard et al. 1998 (104) Simard et al. 1998 (24) B. D’Anjou 1992 (pers. comm.) B. D’Anjou 1992 (pers. comm.) J. Barker 1992 (pers. comm.) J. Barker 1992 (pers. comm.) J. Barker 1992 (pers. comm.) Simard et al. 1998 (17)
a – complexes follow descriptions provided by Newton and Comeau (1990); b – Crop species: Bg=grand fir, Cw=western redcedar, Fd=Douglas-fir, Hw=western hemlock, Pl=lodgepole pine; Se=Engelmann spruce; Ss=Sitka spruce; Sw=white spruce; Sx=interior (hybrid) spruce; Region (Forest Region): C=Cariboo, K=Kamloops, N=Nelson,P=Prince George, S=Prince Rupert, bold numbers indicate that treatment V=Vancouver; c – number of years after treatment; Replication: U=Unreplicated trial; R=Replicated trial; d – refers to PROBE installation or site; Blue/b resulted in a significant survival increase (p
