Aspen regeneration on log decking areas as influenced by season and duration of log storage

Transcription

1 Uth Stte University Aspen Biliogrphy Aspen Reserch 29 Aspen regenertion on log decking res s influenced y seson nd durtion of log storge Kevin N. Renkem Victor J. Lieffers Simon M. Lndhusser Follow this nd dditionl works t: Prt of the Forest Sciences Commons Recommended Cittion Renkem, Kevin N.; Lieffers, Victor J.; nd Lndhusser, Simon M., "Aspen regenertion on log decking res s influenced y seson nd durtion of log storge" (29). Aspen Biliogrphy. Pper This Article is rought to you for free nd open ccess y the Aspen Reserch t DigitlCommons@USU. It hs een ccepted for inclusion in Aspen Biliogrphy y n uthorized dministrtor of DigitlCommons@USU. For more informtion, plese contct dyln.urns@usu.edu.

2 New Forests (29) 38: DOI 1.17/s y Aspen regenertion on log decking res s influenced y seson nd durtion of log storge Kevin N. Renkem Æ Victor J. Lieffers Æ Simon M. Lndhäusser Received: 17 Decemer 28 / Accepted: 27 April 29 / Pulished online: 8 My 29 Ó Springer Science+Business Medi B.V. 29 Astrct This study ssessed spen regenertion on decking res s ffected y seson of log deck uilding nd durtion of log storge; s well s root wounding, soil compction, nd slsh depth. On former decking res tht were uilt fter summer hrvest, spen regenertion ws 5% lower nd root deth 35% greter compred to former decking res of fll hrvest. Durtion of log storge fter fll hrvest hd little effect on spen regenertion; short (1.5 3 months) or long (11 months) storge resulted in similr regenertion. Slsh lod ws gretly incresed on decking res while root wounding nd soil ulk density were only slightly incresed compred to controls. For est mngement prctices, log storge fter summer hrvest should e voided especilly when logs re kept over the growing period when suckering occurs. Additionlly, removing the interwoven mt of slsh covering decking res nd limiting mchine trffic to frozen soil will ensure vigorous suckering. Keywords Populus tremuloides Borel forest Hrvesting trffic Lndings Slsh ccumultion Root dmge Soil compction Introduction Numerous studies hve reported insufficient spen sucker estlishment (Btes et l. 1993; Shepperd 1993; Nvrtil 1996; Kzems 1996; Stone nd Elioff 1998; Smidt nd Blinn 22; Berger et l. 24; McN 1994; Corns nd Mynrd 1998; Stone 21; McIssc et l. 26; Zenner et l. 27) nd growth (Btes et l. 1993; Corns nd Mynrd 1998; Kzems nd Heussler 25) on designted skid trils, hul rods, nd lndings fter hrvesting. These res cn occupy up to 2% of cutovers (Kzems nd Heussler 25; McIssc et l. 26), nd poor growth of regenerting spen on such lrge re could cuse shift to lower site index thn it ws originlly (Kzems nd Heussler 25). K. N. Renkem (&) V. J. Lieffers S. M. Lndhäusser Centre for Enhnced Forest Mngement, Deprtment of Renewle Resources, University of Alert, 4-42 Erth Sciences Building, Edmonton, AB T6G 2E3, Cnd e-mil: renkem@ulert.c

3 324 New Forests (29) 38: Lndings or decking res re of prticulr concern s they re the most hevily impcted (Berger et l. 24). Typiclly, poor regenertion on lndings hs een ttriuted to the disturnces cused y concentrted-skidder trffic on these res (Shepperd 1993; Berger et l. 24); however decking nd storge of the logs might lso hve n impct (Nvrtil 1996). After trees hve een delimed the logs re often stored in pile (log deck) next to the rod. In some instnces the log deck is huled immeditely nd the impct is thought to e negligile (Nvrtil 1996), ut more often huling is delyed. The dely llows logs to dry for up to yer so tht hul weights re reduced, or it llows for drier or frozen hul rod conditions (R. Butson, Personnel communiction, Alert Pcific Ltd). The impct tht log deck uilding nd storge hs on spen regenertion is not known, ut it my hve severl negtive effects. A log deck could ct s physicl rrier to emerging suckers preventing them from photosynthesizing. As result, the crohydrte reserves of the root system in the newly cut re would not e mintined nd portions of the root system might die, which would cuse poor regenertion once the log deck is removed (DesRochers nd Lieffers 21; Lndhäusser nd Lieffers 22). The lrge volume of logs nd rk on the decking re could lso produce lechtes tht re high in phenols. High concentrtions of phenols from spen-deris cn cuse decrese in the growth of spen (Conlin 21). The impcts of log storge re likely greter the longer the log deck is stored ecuse lrger mount of crohydrtes will e lost to mintennce respirtion (DesRochers et l. 22). The seson of uilding log deck could hve n effect s well; log deck uilt in the summer when soil tempertures re wrm cn result in greter depletion of crohydrtes y respirtion compred to the fll (DesRochers et l. 22). While log storge length nd timing lone could negtively ffect spen regenertion, other conditions such s slsh lod nd the effects of mchine trffic, soil compction nd root wounding, could reduce spen suckering on decking res. Slsh ccumultion cused y deliming cn dely thwing nd wrming of the soil (Bell 1986) or ct s rrier to the emergence of suckers (Lndhäusser et l. 27). Soil compction reduces root respirtion nd growth (Htchell et l. 197; Rurk et l. 1982); root wounding frgments the root system (Zhner nd Deyle 1965); nd the wounds cn serve s entry points for decy (Bshm 1988; Pnkuch et l. 23). All of these disturnces to the root system could led to reduction in the root s ility to produce dequte regenertion (Shepperd 1993). The ojective of this study ws to ssess spen regenertion on log decking res tht hd een reclimed fter huling. The tretments were seson of uilding of the decks, nd secondly, durtion of storge of logs on decks. Root condition, soil ulk density, nd slsh lod were lso evluted to determine their influence on spen regenertion. Methods Study re The study ws conducted within 1, h forestry plnning unit of Alert Pcific Forest Industries Ltd. locted in the Borel Mixedwood Ecoregion, 5 km northest of Lc L Biche, Alert (etween 55 6 to 55 1 N nd to W). This Ecoregion receives 38 mm of precipittion nnully with the wettest months eing June nd July. Averge tempertures rnge from 13.8 C in the summer to -1.5 C in the winter. Soils in this re re fine-textured gry luvisols, nd the dominnt cover type is spen (Populus tremuloides (Michx.)) with minor components of white spruce (Pice gluc (Moench)

4 New Forests (29) 38: Voss), lsm poplr (Populus lsmifer L.), pper irch (Betul ppyrifer (Mrsh.)), nd lck spruce (Pice Mrin (Mill.) BS.P.) in low res (Strong nd Leggt 1992). From lte June to lte Octoer of 26, 1,1 h of spen-dominted sites in the plnning unit were cler-cut using full tree hrvesting methods. This involved cutting with feller-uncher hrvester, skidding the entire tree to rodside decking re with grpple skidders, deliming, nd cutting the tree to length t the decking re. Following deliming, the logs were stcked into decks 1 2 m in height nd less thn 2 m from the rod side. Decking occurred within 2 weeks fter hrvesting egn. Log decks were plced directly on the existing soil s result there ws no scrping or removl of ny soil for the uilding of the decking re. The dtes when the log decks were uilt nd when logs were huled vried etween cutovers. Cutovers selected for the study were (A) erly summer logged (June to erly July) nd hd the logs stored during the sme growing seson nd were huled in the fll (summer short storge); (B) lte summer logged (August to Septemer) nd hd the logs huled the sme fll (fll short storge); nd (C) lte summer logged (August to Septemer) nd hd the logs huled fter the following growing seson (fll long storge) (Tle 1). After the log decks were huled, corse slsh ws spred or piled y ulldozer nd urnt (R. Butson, Personnel communiction, Alert Pcific Ltd.). In most circumstnces, however, there ws still consolidted lyer of finer slsh such s fine twigs, rnches, nd rk covering the former decking re. Smpling design In totl 26 decking res spced minimum of 25 m prt were exmined. Ech of these ws pired with control, i.e., minimlly distured re pproximtely 15 m from the edge of the hrvested re ut within 1 m of the log decking re. Five decks ech were exmined from the summer short storge, nd fll short storge tretments nd 16 were selected from the fll long storge tretment res (Tle 1). Becuse the log decks hd een removed t the time of the study, their position ws determined y the presence of rk deris ner the hul rod s deliming ws done on the decking res (R. Butson, Personnel communiction, Alert Pcific). Once the presence of the log deck hd een confirmed, eight suplots, on trnsect running prllel Tle 1 Hrvest informtion for log-deck storge tretment sites Tretment Replictes Cut Hul Cut dte indictes the strt of hrvest nd hul dte is when the logs were removed from the log deck re Fll long storge Fll short storge Summer short storge 6 7 August 26 2-July August July August July August July Septemer 26 2-July August July August 26 3-Septemer August Novemer Septemer 26 3-Novemer Septemer 26 3-Novemer July Octoer June Novemer-26

5 326 New Forests (29) 38: to the hul rod were positioned in the middle of the decking re (pproximtely 6 m from the rod). The suplots were spced minimum of 5 m prt nd mximum of 15 m depending upon the length of the decking re. Suplots flling on stumps tht prevented root nd soil smpling or on res with visile rutting, evidence of urnt slsh, or on low spots were voided y moving them 2 m further long the trnsect. A similr trnsect of eight suplots ws estlished in the control re. The suplots for ech trnsect were verged so tht ech trnsect represented replicte. Mesurements In August of 28, 2 yers fter hrvesting, mesurements of sucker density nd height were mde in ech suplot for ll tretments including the control plots. Mesurements of root condition, soil ulk density, nd slsh coverge were tken in every second of the eight suplots. The numer of spen nd lsm poplr suckers were counted in circulr.1 h regenertion suplot (s lsm poplr constituted\2% of the suckers, they were not differentited in the results from the spen suckers). The height of the leding spen sucker in ech qurter of the regenertion suplot ws lso mesured. Becuse only 1 yer old suckers were found in the fll-long storge tretment, while the other tretments, including the control, hd 2-yers-old suckers, comprison ws mde for first yer growth mong the tretments. First yer growth for the 2-yers-old suckers ws clculted sed on rtio of first to second yer growth. The rtio ws determined y rndomly smpling 1 suckers nd mesuring first nd second yer growth seprtely using ud scrs. Root condition ws ssessed y spding 32 cm y 32 cm pit in the centre of every second suplot. All spen nd lsm poplr roots greter thn.5 cm nd less thn 2. cm in dimeter (considered the dominnt suckering roots (DesRochers nd Lieffers 21)) were collected from ech pit to 15 cm-depth of the minerl soil. The roots were stored t 5 C nd trnsported ck to the lortory. The totl liner length of roots nd the lengths of root tht ws lckened nd/or ded were mesured. The proportion of ded to totl length ws then clculted. The numer of visile wounds tht covered more thn 1 cm 2 of surfce re of the roots were lso counted, nd expressed s the numer of wounds per liner meter of root. The core method ws used to determine soil ulk density (Blke nd Hrtge 1986). Soil cores (325 cm 3 ) were tken from the top 1 cm of minerl soil. The soil ws tken ck to the lortory where it ws dried to constnt weight t 8 C. Rocks or orgnic mtter greter thn.3 cm in dimeter ws removed y sieving nd their weight nd volume ws sutrcted from the core volume. The dried soil ws weighed nd soil ulk densities were clculted s g/cm 3. Slsh depth ws quntified y tking the verge depth of slsh deris from three spots within.25 m 2 t the center of ech plot. The depth ws mesured from the upper lyer of slsh to the top of the originl soil LFH lyer. Dt nlysis An initil comprison ws mde etween the decking nd control res. This involved grouping ll vriles from the three log deck tretments into one. The comprison ws mde with one-wy ANOVA using the GLM procedure in SAS (SAS Institute, version 9.1). The sttisticl model ws Y ¼ l þ T þ e

6 New Forests (29) 38: where Y ws the men of the vrile (sucker density, first yer height of the leding sucker, percent ded root, numer of wounds, soil ulk density, or slsh depth); l ws the popultion men for the vrile; T ws the effect of the tretment (decking re or control); e ws the rndom error. A mens seprtion test ws not used s there were only two tretments. A seprte set of one-wy ANOVAs ws used to compre the three log deck tretments. The sttisticl model nd vriles tested were the sme ut the tretments were summer short storge, fll short storge, or fll long storge. Unlike the other vriles, sucker density on log deck res ws found to hve significnt reltionship with the sucker density of the pired control. Thus, sucker density ws nlyzed with ANCOVA using the sucker densities from the pired controls s covrites. The model tested ws similr to tht of the ANOVA except X ws included s the covrite. Y ¼ l þ T þ X þ e Provided the ANOVA or ANCOVA ws significnt, two plnned comprisons were mde using the LSD mens comprison test: summer short storge versus fll short storge to determine the impct of seson of log deck uilding nd fll long storge versus fll short storge to ssess the effects of storge durtion. A finl set of one-wy ANOVAs ws used to evlute ny difference etween the decking res of the tretment sites. Sucker density nd first yer height of the leding suckers from the pired controls of the three decking tretments were compred. The sttisticl model ws the sme s used for the previous ANOVA. No mens seprtion tests were performed s none of the ANOVAs were significnt. For ll ANOVAs nd the ANCOVA the vrile residuls met the ssumptions of normlity sed on the Shpiro Wilk test nd homogeneity of vrinces using Brtlett s test. The ssumptions for the covrite used in ANOCVA were ssessed grphiclly. An lph vlue of.5 ws used to determine significnce in ll tests. Multiple regression nlysis ws used to exmine the reltionships etween suckering density or height with root wounding, soil ulk density, nd slsh depth. Dt from ll tretments nd the control ws used, nd dummy vriles were used to ccount for the effect of the tretment. However, using stepwise selection in the regression procedure in SAS, root wounding, soil ulk density, nd slsh depth were not useful predictors in the model. Results Generl impct of decks The vigor of spen regenertion nd mount of living root ws significntly reduced on log decking res (Tle 2). Sucker density on decking res ws 16,659 stems h -1 (cross ll decking tretments) while controls hd nerly three times the density with 47,47 stems h -1 (Fig. 1). First yer height growth of the leding suckers on decks ws out hlf tht of the controls; 55 cm on the decks nd 95 cm in the control (Fig. 1). As well, on decking res 58% of the roots were ded compred to 33% for the control (Fig. 1c). Root wounding, soil ulk density nd slsh lod were significntly greter on the decking res thn the controls (Tle 2). Roots hd 2.2 wounds per meter on decking

7 328 New Forests (29) 38: Tle 2 Results of one-wy ANOVAs for the comprison etween ll log deck nd control res Response vriles df F-rtio P vlue 1. Sucker density \.1 2. First yer height \.1 3. Ded roots \.1 4. Root wounding Soil ulk density Slsh depth \.1 5 A C E 1.5 Suckers h Ded root (% of root length) Soil ulk density (g cm -3 ) B 2.5 D. 6 F Height (cm) Wounds / meter of root Depth of slsh (cm) Control Decking re. Control Decking re Control Decking re Fig. 1 Comprisons etween minimlly distured res of cutover (control) nd decking res, Sucker density of spen. First yer height growth of the leding suckers. c Percent of ded roots y root length,.5 2. cm in dimeter. d Density of wounds greter thn 1 cm 2 on spen roots.5 2. cm in dimeter. e Bulk density of the top 1 cm of minerl soil. f Depth of slsh such s rk nd rnches. Different letters indicte sttisticlly significnt differences for ech grph res compred to 1.2 for the control res (Fig 1d). Soil ulk density on decks (1.5 g cm -3 ) ws 5% higher thn the controls (1.43 g cm -3 ) (Fig. 1e). The difference in slsh depth etween decking res nd controls ws lrge with n verge of 5.9 cm on the decks nd 2.3 cm in the control (Fig. 1f).

8 New Forests (29) 38: Impct of seson of log deck uilding Building log decks during summer hrvest hd significnt negtive impct on sucker densities nd the mount of living roots (Tle 3). Suckering on decking res tht were hrvested in the summer nd hd 3 5 months of log storge hd hlf the density of suckers (7,574 stems h -1 ) compred to fll hrvest with months of log storge (16,472 stems h -1 ) (Fig. 2). The seson of estlishing log decks did not ffect the height of suckers. The first yer height of the leding suckers for oth tretments ws pproximtely 45 cm (Fig. 2). Condition of the root system in decking res ws different etween the two tretments. Two summers fter logging, 85% of the length of root system ws ded in the decking res of summer hrvested sites compred to 5% in the fll hrvested sites (Fig 2c). Root wounding, soil ulk density, nd slsh lod were not ffected y the seson of log deck uilding. The trend, however, ws for more wounds in the fll-hrvested sites (2.9 wounds m -1 ) compred to summer decks (1.9 m -1 ) (Fig. 2d). The men ulk density ws 1.5 g cm -3 (Fig 2e) nd slsh depth ws 6.1 cm for oth tretments (Fig. 2f). There were no differences in sucker densities or height growth etween the controls (non-decking res) of these two tretments (Tle 4). Sucker density (44,313 stems h -1 ) nd height growth (92 cm) were similr to the verge of ll controls (Fig. 1, ). Impct of log storge durtion The density of spen suckers nd the condition of the root system ws not ffected y the durtion of log storge fter fll hrvest (Tle 3). A men density of 19,641 stems h -1 ws found on long storge res (11 months) compred to 16,472 stems h -1 for short storge (1.5 3 months) (Fig. 3). First yer height growth of the leding suckers ws different etween the two tretments with the tller suckers eing on sites with long storge of logs (Fig 3). The condition of the root systems ws similr etween the long nd short storge. The rtio of ded to living roots ws not different s pproximtely hlf of the totl lengths of roots were ded in oth tretments (Fig. 3c). Log storge durtion did not ffect root wounding, soil ulk density, or slsh (Tle 3). Ech tretment hd 2 3 wounds m -1 of root (Fig. 3d). Soil ulk density ws on verge 1.5 g cm -3 (Fig. 3e) nd slsh ws out 6 cm deep (Fig. 3f). Tle 3 One-wy ANOVAs nd mens seprtion test results for comprison mde etween the three log deck storge tretments: summer short storge (summer) with fll short storge (fll) nd fll short storge (short) nd fll long storge (long) Response vriles Source of vrition df F-rtio P vlue Comprison (P vlue) Summer-fll Short-long 1. Sucker density Tretment Density (control) Covrite First yer height Tretment Ded roots Tretment Root wounding Tretment Soil ulk density Tretment Slsh depth Tretment

9 33 New Forests (29) 38: Suckers h A Ded root (% of root length) C Soil ulk density (g cm -3 ) E B 4 D. F Height (cm) Wounds / meter of root Depth of slsh (cm) Fll-short Summer-short Fll-short Summer-short Fll-short Summer-short Fig. 2 Comprisons etween log decks tht were uilt in n erly summer hrvest followed y 3 5 month of deck storge (summer-short storge) compred to decks tht were uilt in the fll nd huled months fter (fll-short storge). Sucker density of spen. First yer height growth of the leding suckers. c Percent of ded roots y root length,.5 2. cm in dimeter. d Density of wounds greter thn 1cm 2 on spen roots.5 2. cm in dimeter. e Bulk density of the top 1 cm of minerl soil. f Depth of slsh such s rk nd rnches. Different letters indicte sttisticlly significnt differences for ech grph Tle 4 One-wy ANOVA results for the comprison etween the pired controls of ech of the log deck tretments Response vrile df F-rtio P-vlue Sucker density First yer height There were no differences etween the controls (non-decking res) of these two tretments (Tle 4), nd sucker density nd height growth were pproximtely equl to the overll verge of the control (Fig 1, ; 47,431 stems h -1 nd 96 cm). Discussion The seson of log-deck uilding hd sustntil impct on spen regenertion. Decking res where the log decks were uilt during summer hrvest nd stored until the upcoming fll, hd spen sucker densities hlf tht of decking res tht were constructed in the fll nd huled shortly fter. The decrese in spen regenertion on decking res in

10 New Forests (29) 38: Suckers h A Ded root (% of root length) C Soil ulk density (g cm -3 ) E Height (cm) B Wounds / meter of root D Depth of slsh (cm) F Fll-long Fll-short Fll-long Fll-short Fll-long Fll-short Fig. 3 Comprisons etween decks with 11 months of log-deck storge fter fll hrvest (fll-long storge) compred to decks where the log deck ws removed months fter fll hrvest (fll-short storge). Sucker density of spen. First yer height growth of the leding suckers. c Percent of ded roots y root length,.5 2. cm in dimeter. d Density of wounds greter thn 1 cm 2 on spen roots.5 2. cm in dimeter. e Bulk density of the top 1 cm of minerl soil. f Depth of slsh such s rk nd rnches. Different letters indicte sttisticlly significnt differences for ech grph the summer months hs typiclly een ttriuted to increses in soil compction, root wounding, nd slsh ccumultion due to unfrozen nd wetter soil conditions (Btes et l. 1993). These fctors hve een linked to incresed root deth (Bell 1986; Shepperd 1993) which would cuse decrese in sucker density (DesRochers nd Lieffers 21). However, ll of these conditions were similr etween the summer nd fll tretments (Fig. 2) despite wetter soil conditions during the summer tretments (R. Butson, Personnel communiction, Alert Pcific Ltd.). Also, the root wounding tended to e greter on the fll decks with short storge. Additionlly, poor regenertion fter summer logging hs often een linked to low root crohydrte reserves in the summer (Btes et l. 1993; Lndhäusser nd Lieffers 22), ut there were no differences in sucker density nd height growth etween the controls of the summer nd fll tretments suggesting tht seson of hrvest hd little direct impct on sucker density; this is supported y other studies (Mundell et l. 28; Mulk et l. 26). The cuse of poor regenertion on the summer decking res is likely relted to the log deck itself. The log deck ws plced on root system t time when soil tempertures were high nd when suckering would nturlly occur. The suckers produced were either unle to emerge from the soil s the log deck cted s physicl rrier, or if they did,

11 332 New Forests (29) 38: they were in drkness nd unle to photosynthesize. The wrm soil conditions cused high root respirtion (DesRochers et l. 22) nd the inility of suckers to photosynthesize would hve depleted crohydrte reserves, which hve een linked to the deth of portions of spen root systems nd poor sucker growth (e.g., DesRochers nd Lieffers 21; Lndhäusser nd Lieffers 22). This likely explins the lrge die-off of roots in the summer decking re nd the poor suckering in generl (Fig. 2c). In contrst to the seson of log deck construction, the durtion of log storge ppered to hve little effect on spen sucker density on the decking re when constructed in the fll (Fig. 3). These tretments hd different time-spns for sucker regenertion growth; the short storge hd 2 yers of growth while the long storge hd only 1 yer efore smpling. Self-thinning of spen suckers cn occur etween the first nd second seson in high density situtions where losses of 25% re not uncommon (Peterson et l. 1989). However, in regenerting stnds where initil sucker densities re low, e.g., less thn 2, stems/h, thinning is miniml in the second yer (Krsny nd Johnson 1992; Dvid et l. 21). The slightly higher sucker densities on the long compred to the short storge sites cn likely e explined y some thinning occurring in the short storge, ut it is prole tht sucker densities on the long storge res would hve een comprle to the densities on short storge res if it hd hd one more seson of growth. Height growth my lso hve een impcted y the different ge of suckers in this comprison s shoot dieck my hve occurred fter the first yer (Peterson nd Peterson 1992) in the short storge sites nd thus reduced mesurements of height growth on the fll-short storge (Fig. 3). In the fll hrvest, the presence of the log deck likely did not hve n incrementl impct on spen regenertion for severl resons. Mundell et l. (28) showed when spen is cut in lte summer, there ws no root suckering efore the following growing seson. Therefore, it cn e ssumed tht the root system did not sucker under the log decks in the fll nd deplete their crohydrte reserves s suggested for the summer decking res. However, these root systems lso did not sucker under the log deck the following growing seson s we did not find ny two-yer-old suckers on these decking res. The likely reson tht the root system filed to sucker in the summer under the deck ws relted to the insulting nture of the log deck, coupled with greter freezing during the prior winter. Typiclly snow cts s n insulting lyer nd cn prevent the ground from freezing deeply. However, in the cse of log deck, the snow will ccumulte on top of the log deck, ut since the ends of the deck remined open, there ws rek in the insulting lyer. As result cold ir could move etween the logs nd contct the ground resulting in deeper penetrtion of frost into the ground. We propose tht in the spring, the ground round the log deck melted nd soil tempertures incresed; however, under the log deck, soil temperture remined low s the deck intercepted rdition tht would typiclly wrm the soil. Lieffers nd Vn Rees (22) recorded tht soils froze erlier under loose lyer of corse slsh tht hd intercepted snow; these res lso remined cool over the following growing seson. As soil tempertures in the orel forest re lredy cool (Strong nd Leggt 1992) the log deck could prevent the soils from reching the 9 C necessry for suckers to grow (Lndhäusser et l. 26). Further, cool soils decresed root respirtion (DesRochers et l. 22). Consequently, root crohydrte reserves could remin reltively unchnged nd suckering potentil could e expected to e sustined once the log deck ws removed. As long-term storge of log decks filed to hve n impct on spen regenertion when constructed in the fll, the hypothesis tht lechtes from these logs could ffect spen regenertion (Conlin 21) cn e negted. Height growth ws ctully greter fter

12 New Forests (29) 38: long-term storge of the log deck compred to the short-term storge. Similrly, Lndhäusser et l. (27) found reltively little impct of the lechtes generted from 4 cm of chipping deris from spen nd it ppers tht the lechtes from deck of logs does not rech the threshold tht dmges spen regenertion. Regrdless of log deck storge, regenertion on decking res ws poor, nd this reinforces the lrge ody of literture showing poor spen regenertion on lnding res (Btes et l. 1993; Nvrtil 1996; Berger et l. 24; McIssc et l. 26; Zenner et l. 27). While mny studies hve implicted soil compction for low sucker densities (Btes et l. 1993; Shepperd 1993; Stone nd Elioff 1998), increses in ulk density oserved in these studies were 1 3%, i.e., much greter thn the 5% we oserved in our study. Smll increses in ulk densities hve een found to ctully increse sucker density while decresing height growth (Stone 21; Kzems nd Heussler 25). As result, the significnt decreses in sucker density on decking res cn most likely e ttriuted to either root wounding or slsh ccumultion. Root wounding in this study ws much lower thn tht oserved y Shepperd (1993) on skid trils, while our density of wounds ws similr to tht of Frser et l. (24), who ctully sw n increse in sucker density with tht degree of wounding. However, root wounding cn led to the entry of decy nd disese which cn reduce height growth nd the effects of wounding nd the entry of decy cn e delyed (Bshm 1988). Therefore, wounding my not hve impcted sucker density, ut it could hve resulted in decrese in sucker height tht ws oserved. We elieve tht slsh depth is one of the min cuses of low sucker density in our study. The reduction of sucker density in our study is consistent with the results of Corns nd Mynrd (1998) nd Lndhäusser et l. (27) who sw 3 5% reductions in sucker density with chipping residue depth of 4 1 cm ecuse the residue cted s rrier to sucker emergence. The slsh on decking res ws similr to chipping residues s it ws composed of thick interwoven lyer of rk nd smll rnches nd likely hd similr effect. Also, slsh hs n insulting effect which keeps soil tempertures low nd will negtively influence height growth of the sucker regenertion (Bell 1986; Lvertu et l. 1994). However, while slsh depth likely hd significnt influence on sucker density, incresed soil ulk density nd wounding cn not e ignored s cuses detrimentl to spen regenertion. Soil compction nd root wounding (Shepperd 1993; Btes et l. 1993) re dependent on soil conditions such s texture nd moisture content during lnding construction nd skidding opertions (Shepperd 1993; McN et l. 21). Unfvorle soil conditions pper not to hve een significnt fctor in our study, ut under different conditions, compction nd root wounding my hve lrger impct. In conclusion, uilding nd storge of log decks during the growing seson significntly reduced regenertion densities elow the suggested minimum of 15, stems h -1 (Dvid et l. 21), nd storing logs over the summer should e voided during summer logging opertions. On the other hnd, log deck storge fter fll or winter hrvest for nerly yer my hve little incrementl impct on spen regenertion eyond tht s result of uilding the deck itself. The mount of interwoven slsh left on decking res even fter the clen-up my e mjor fctor limiting spen regenertion. This mt of deris should e crefully removed in the reclmtion of the decking re. However, cre must e tken to remove the deris without n excessive removl or dmge to the spen root system s result of lding too deep. In ddition, voiding excessive soil compction or direct dmge to the root system during opertion would likely improve spen regenertion in these prolem res; consequently logging on frozen ground should e the preferle option.

13 334 New Forests (29) 38: Acknowledgments Thnks to Kevin Solrik, Eckehrt Mrenholtz, nd Jne Wolken for their ssistnce in the field. Roger Butson from Alert Pcific Ltd for ssistnce in site selection nd insight into hrvesting opertions. Funding ws provided y West Frser Mills, Weyerheuser Compny, nd NSERC. References Bshm JT (1988) Decy nd stin 1 yers lter in spen suckers sujected to scrifiction t ge 3. Cn J Res 18: doi:1.1139/x Btes PC, Blinn CR, Alm AA (1993) Hrvesting impcts on quking spen regenertion in northern Minnesot. Cn J Res 23: doi:1.1139/x Bell IE (1986) Logging prctices nd susequent development of spen stnds in est-centrl Ssktchewn. For Chron 62:81 83 Berger AL, Puetmnn KJ, Host GE (24) Hrvesting impcts on soil nd understory vegettion: the influence of seson of hrvest nd within-site disturnce ptterns on cler-cut spen stnds in Minnesot. Cn J Res 34: doi:1.1139/x4-97 Blke GR, Hrtge KH (1986) Bulk density. In: Klute A (ed) Methods of soil nlysis. Prt 1. Physicl nd minerlogicl methods, 2nd edn. Agronomy Monogrph 9, pp Conlin TSS (21) In-woods chipping: possile evidence for llelochemicl interction of lechte generted from tremling spen (Populus tremuloides Michx.) rk nd wood wste. For Chron 77: Corns GW, Mynrd DG (1998) Effects of soil compction nd chipped spen residue on spen regenertion nd soil nutrients. Cn J Soil Sci 78:85 92 Dvid AJ, Zsd JC, Gilmore DW, Lndhäusser SM (21) Current trends in the mngement of spen nd mixed spen forests for sustinle production. For Chron 77: DesRochers A, Lieffers VJ (21) Root iomss of regenerting spen (Populus tremuloides) stnds of different densities in Alert. Cn J Res 31: doi:1.1139/cjfr DesRochers A, Lndhäusser SM, Lieffers VJ (22) Corse nd fine root respirtion in Populus tremuloides. Tree Physiol 22: Frser EC, Lieffers VJ, Lndhäusser SM (24) Wounding of spen roots promotes suckering. Cn J Bot 82: doi:1.1139/4-9 Htchell GE, Rlston CW, Foil RR (197) Soil disturnce in logging. J For 68: Kzems R (1996) Where hve ll the ig pores gone? Impcts of concentrted hevy equipment trffic on ertion porosity nd ulk density in n spen ecosystem. In: Comeu PG, Hrper GJ, Blche ME, Boteng JO, Thoms KD (eds) Ecology nd mngement of B.C. Hrdwoods, Workshop Proceedings, FRDA Report 255. BC Ministry of Forestry, Richmond Kzems R, Heussler S (25) Soil properties, spen, nd white spruce responses 5 yers fter orgnic mtter removl nd compction tretments. Cn J Res 35: doi:1.1139/x5-175 Krsny ME, Johnson EA (1992) Stnd development in spen clones. Cn J Res 22: doi: /x92-19 Lndhäusser SM, Lieffers VJ (22) Lef re renewl, root retention nd crohydrte reserves in clonl tree species following oveground disturnce. J Ecol 9: doi:1.146/j x Lndhäusser SM, Lieffers VJ, Mulk T (26) Effects of soil temperture nd time of decpittion on sucker initition of intct Populus tremuloides root systems. Scnd J For Res 21: doi:1.18/ Lndhäusser SM, Lieffers VJ, Chow P (27) Impct of chipping residues nd their lechte on the initition nd growth of spen root suckers. Cn J Soil Sci 87: Lvertu D, Muffette Y, Bergeron Y (1994) Effects of stnd ge nd litter removl on the regenertion of Populus tremuloides. J Veg Sci 5: doi:1.237/ Lieffers S, Vn Rees K (22) Impct of slsh loding on soil tempertures nd spen regenertion. Sustinle Forest Mngement Network, Edmonton, Alert. Project Report 22-6 McIssc DA, Comeu PG, Mcdonld SE (26) Dynmics of regenertion gps following hrvest of spen stnds. Cn J Res 36: doi:1.1139/x6-77 McN DH (1994) Tillge of compcted hul rods nd lndings in the Borel forests of Alert, Cnd. For Ecol Mng 66: McN DH, Strtsev AD, Nguyen H (21) Soil wetness nd trffic level effects on ulk density nd ir-filled porosity of compcted orel forest soils. Soil Sci Soc Am J 65:8 1247

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