George Harper. British Columbia ... Keith Thomas. British Columbia .... conifer) over the 14-year post-treatment period (Harper et al., in press) (cph: clumps per ...
108
Extension Note
December 12
The Growth of Bigleaf Maple 20+ Years after Harvesting
George Harper British Columbia Ministry of Forests, Lands and Natural Resource Operations Victoria, B.C.
Introduction
Philip Comeau University of Alberta Department of Renewable Resources Edmonton, Alta. Keith Thomas British Columbia Ministry of Forests, Lands and Natural Resource Operations Victoria, B.C.
Bigleaf maple (Acer macrophyllum Pursh) (Figure 1) is a component of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and red alder (Alnus rubra Bong.) stands and occasionally occurs in pure stands in southern portions of the Coastal Western Hemlock biogeoclimatic zone (Meidinger and Pojar 1991) of British Columbia. Its best growth is on the moist and rich soils of river terraces, floodplains, and seepage sites at relatively low elevations (below 300 m) (Haeussler et al. 1990; Minore and Zasada 1990).
wood is used for higher-value appearance-grade products, such as flooring, furniture, and millwork. Bigleaf maple is also being tapped for syrup production in some parts of the British Columbia coast. After harvesting, the stumps of bigleaf maple sprout vigorously and can produce up to 60 stump sprouts with growth of 2 m or more in height annually (Lauterbach and Warren 1982; Cole and Newton 1990) (Figure 2). Bigleaf maple sprout clumps (hereafter called clumps) can reach a crown diameter of 5 m in 2 years, and by 40 years, a maple clump can cover an area as large as 100 m2 (Thomas and Comeau 1998).
figure 1 Bigleaf maple foliage.
BROADLEAF MIXEDWOOD MANAGEMENT
Bigleaf maple is a valuable commercial tree species (Minore and Zasada 1990) capable of reaching 30 m in height and 120 cm in diameter. The
figure 2 An unmanaged bigleaf maple clump of stump sprouts after leaf fall.
As a result, bigleaf maple stump sprout clumps are considered serious competitors of Douglas-fir (Haeussler et al. 1990) and other conifers. Clumps can rapidly occupy available growing space and overtop planted seedlings, resulting in increased mortality and reduced growth (Knowe et al. 1995). In addition, maple sprouts can cause conifer damage through contact with branches and leaders, and heavy leaf litter from established maple stands can smother small seedlings. Retaining bigleaf maple in mixture with conifers may be valuable for soil carbon and nutrient cycling (Fried et al. 1990). In addition, the presence of maple may contribute to stand structure, species diversity, wildlife habitat, and landscape aesthetics (Figure 3).
the 1988 harvesting (Figure 5). The remaining uncut clumps were well distributed within each plot. In Study 2, the impact of density control within clumps was explored by following the growth of residual sprouts after spacing. Study 2 used a completely randomized design with three treatments each randomly assigned to 10 maple clumps: (a) untreated control, (b) space to 30 cm between sprouts, and (c) space to 60 cm between sprouts. The tallest sprouts with the best form figure 4 Maple stumping treatment.
The practice of maple sprout thinning is common on southern Vancouver Island, but little information documenting treatment effectiveness has been published. The Experiment
figure 3 Retained uncut maple may avoid clump competition issues and provide wildlife tree habitat.
Historically, control of maple has been most successful when using herbicides (Wagner and Rogozynski 1994) or stump removal treatments (Figure 4). Density management of bigleaf maple clumps and sprouts may offer improved sawlog merchantable yield and shortened rotations. Thinning or spacing treatments may accelerate the growth of residual clumps or stems.
During 1995, Thomas and Comeau (1998) established two bigleaf maple studies to provide stand- and treelevel information on the effects of maple clump and sprout thinning on the growth of planted Douglas-fir and grand fir (Abies grandis [Dougl.] Lindl.). These two studies were located in a cutblock in the Coastal Western Hemlock xeric maritime variant (CWHxm2) near Port Alberni, British Columbia. During 1988, the block was clearcut harvested and planted with Douglasfir and grand fir. In 1995, up to 400 evenly spaced maple clumps per hectare (cph) were found. In Study 1, ten 30 × 30 m plots were established where various clump thinning densities ranging from 0 to 400 cph were assigned (that is, 0, 33, 67, 100, 133, 167, 200, 244, 300, and 400 clumps per hectare). In the spring of 1996, chainsaws and pruning saws were used to fell all sprouts arising from selected maple stumps left after
figure 5 A cut maple clump from Study 1, spring 1996.
were selected to leave. The remaining sprouts were cut with pruning saws. Study 1: Clump Thinning Results After 14 years, results from the Study 1 clump thinning plots suggested that there was no change in uncut maple and planted conifer crown area, height, or diameter at breast height (dbh) across the various cph treatments (Harper et al., in press). Cut maple clumps continued to re-sprout 5 years post-thinning, which together with the uncut maple resulted in wellestablished stand canopies dominated by maple. Twenty-two years after logging, the planted Douglas-fir and grand fir average height was about 9 m, and the tallest conifer height was
2
about 18 m. The average height of the uncut maple sprouts ranged from 15 to 20 m (Figure 6). Long-term changes in uncut maple clump and sprout size across the cph densities indicated that sprout development (dbh and height) was not influenced by clump density. Maple sprout growth was largely dependent on within-clump sprout density, not on stand clump density. Stand volume increment over the 14-year post-treatment period ranged from 106 to 183 m3/ha (7.6–13.1 m3/ha/ yr) (Figure 7). Such large stand volume increments in a relatively short period are comparable to high-site red alder and managed Douglas-fir plantations (Mitchell et al. 2010). These results suggest that there are opportunities to manage dense maple clump stands for short-rotation fibre plantations, hardwood sawlogs, and/or fuel. Study 2: Sprout Spacing Results In Study 2, the spacing treatments (Figure 8) initially increased sprouting activity; however, after 8 years
figure 7 Study 1 stand volume increment results by stand component (maple and planted conifer) over the 14-year post-treatment period (Harper et al., in press) (cph: clumps per hectare).
most of the smaller new sprouts had died (Figure 10a). Spacing the sprouts within a clump at either 30 cm or 60 cm significantly accelerated diameter growth of the remaining uncut maple sprouts (Figure 10b; Appendix 1). Thirteen years after spacing, the 60-cm spaced sprouts had average diameters 2.4 times those of the unspaced control clumps (Figure 10b). A minimum merchantable diameter of 12 cm was reached 8 years postspacing (16 years after harvesting) (Figure 10b). There was no significant difference in height between the treatments (Appendix 1). These observations reinforce the results of Study 1, thus indicating that maple sprout growth is largely dependent on within-clump sprout density, not on stand clump density (Figure 9).
figure 8 Study 2: spacing maple clump sprouts.
Management Implications
figure 6 Study 1: 30 × 30 m plots with stump sprout maple clumps and planted conifers.
Results from these two studies indicate that there are opportunities for intensively managing maple clumps to increase early sprout diameter growth. Sawlog objectives should focus on coppice-based
figure 9 A tagged uncut maple clump 22 years post-harvest.
3
figure 11 Sprout spacing to one per clump may lead to poor stem form if open grown. Retaining multiple sprouts per clump (three to five) may better promote branch pruning and straight bole development.
References
figure 10 Study 2: (A) average number of sprouts per clump, and (B) average tagged sprout dbh for the three treatments plotted over years post-thinning (see Appendix 1).
spacing designed to select healthy stems and optimize individual sprout growing space (Figure 11). The presence of maple clumps within a conifer plantation may significantly affect conifer survival and growth depending on clump density and proximity. The rapid early growth of bigleaf maple sprouts will result in maple-dominated stand development, and unless individual
conifers can maintain a similar level of height and crown growth within maple canopy gaps, few will survive in the long term to become crop trees. However, stands of maple clumps of stump sprout origin have the potential to produce high fibre volumes on short rotations. Planting conifers within regeneration gaps will ensure full site occupancy and maximize total yield.
Cole, E.C. and M. Newton. 1990. Efficacy of different herbicides on bigleaf maple sprout clumps. Proc. West. Soc. Weed Sci. 43:37–43. Comeau, P., F. Gendron, and T. Letchford. 1998. A comparison of several methods for estimating light under a paper birch mixedwood stand. Can. J. For. Res. 28:1843–1850. Fried, J.S., J.R. Boyle, J.C. Tappeiner II, and K. Cromack. 1990. Effects of bigleaf maple on soils in Douglas-fir forests. Can. J. For. Res. 20:259–266. Gendron, F., C. Messier, and P.G. Comeau. 1998. Comparison of various methods for estimating the mean growing season percent photosynthetic photon flux density in forests. Agric. For. Meteorol. 92:55–70.
4
_______. 2001. Temporal variations in the understorey photosynthetic photon flux density of a deciduous stand: the effects of canopy development, solar elevation, and sky conditions. Agric. For. Meteorol. 106:23–40. Haeussler, S., D. Coates, and J. Mather. 1990. Autecology of common plants in British Columbia: a literature review. For. Can. and B.C. Min. For., Victoria, B.C. FRDA Report 158. Harper, G., K. Thomas, and P. Comeau. The growth of bigleaf maple and planted conifers 14 years after maple clump spacing. B.C. Min. For., Lands Nat. Resourc. Ops., Victoria, B.C. Tech. Rep. In press. Knowe, S.A., B.D. Carrier, and A. Dobkowski. 1995. Effects of bigleaf maple sprout clumps on diameter and height growth of Douglas-fir. West. J. Appl. For. 10(1):5–11. Lauterbach, P. and L.E. Warren. 1982. Control of resprouting hardwood clumps with applications of triclopyr ester by hovering helicopter. Proc. West. Soc. Weed Sci. 35:36–38. Meidinger, D. and J. Pojar. 1991. Ecosystems of British Columbia. B.C. Min. For., Res. Br., Victoria, B.C. Spec. Rep. Ser. 6. Minore, D. and J. Zasada. 1990. Acer macrophyllum Pursh, bigleaf maple. In: Silvics of North America. Vol. 2: Hardwoods. R.M. Burns and B.J. Honkala (editors.). U.S. Dep. Agric. For. Serv. Washington, D.C. Agric. Handb. 654, pp. 33–40. Mitchell, K.J., M. Stone, S.E. Grout, M. Di Lucca, G.D. Nigh, J.W. Goudie, J.N. Stone, A.J. Nussbaum, A. Yanchuk, S. Stearns-
Smith, and R. Brockley. 2010. TIPSY version 4.2. Online. B.C. Min. For. Range, Res. Br., Victoria, B.C. www.for.gov.bc.ca/hre/ software/download.htm
bigleaf maple sprout clumps. West. J. Appl. For. 11(4):120–124.
Peterson, E.B., N.M. Peterson, P.G. Comeau, and K.D. Thomas. 1999. Bigleaf maple managers’ handbook for British Columbia. B.C. Min. For., Res. Br., Victoria, B.C. Misc. Rep. 090. www.for.gov.bc.ca/hfd/ pubs/docs/mr/mr090.htm
Thomas, K.D. and P.G. Comeau. 1998. Effects of bigleaf maple (Acer macrophyllum Pursh) on growth of understorey conifers and the effects of coppice spacing on the growth of maple (MOF EP1121.02). B.C. Min. For., Res. Br., Victoria, B.C. Exten. Note 24. www.for.gov. bc.ca/hfd/pubs/Docs/En/En24. htm
Tappeiner, J.C. II, J. Zasada, D. Huffman, and B.D. Maxwell. 1996. Effects of cutting time, stump height, parent tree characteristics, and harvest variables on development of
Wagner, R.G. and M.W. Rogozynski. 1994. Controlling sprout clumps of bigleaf maple with herbicides and manual cutting. West. J. Appl. For. 9(4):118–124.
appendix 1 Study 2: Statistical results from analysis of covariance (pretreatment as covariate) and Tukey means tests (means with different letters denotes significant difference at P< 0.05).
Treatment
dbh dbh Height year 1 year 13 year 13 (cm) (cm) (m)
Clump Clump sprout sprout number number year 1 year 13
Untreated A B A A A (5.1) (5.6) (15.5) (16) (8) 30 cm spacing
B A A B AB (6.1) (11.0) (15.7) (66) (6)
60 cm spacing
C A A B B (6.8) (13.6) (16.1) (52) (3)
p value
