EARLY GROWTH RESPONSE IN TREES FOLLOWING PEATLAND DRAINAGE

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1 EARLY GROWTH RESPONSE IN TREES FOLLOWING PEATLAND DRAINAGE G.R. Hillmn nd J.J. Roerts INFORMATION REPORT NOR-X-408 Northern Forestry Centre

2 The Cndin Forest Service s Northern Forestry Centre is responsile for fulfilling the federl role in forestry reserch nd technology trnsfer in Alert, Ssktchewn, Mnito, Nunvut, nd the Northwest Territories. The min ojective is reserch in support of improved forest mngement for the economic, socil, nd environmentl enefit of ll Cndins. The Northern Forestry Centre is one of five centers of the Cndin Forest Service, which hs its hedqurters in Ottw, Ontrio. Le Service cndien des forêts, Centre de foresterie du Nord, représente le gouvernement fédérl en Alert, en Ssktchewn, u Mnito, u Nunvut et dns les Territoires du Nord Ouest en ce qui trit ux recherches forestières et u trnsfert de technologie. Cet orgnisme s intéresse surtout à l recherche en vue d méliorer l méngement forestier fin que tous les Cndiens puissent en profiter ux points de vue économique, socil et environnementl. Le Centre de foresterie du Nord constitue l un des cinq étlissements du Service cndien des forêts, dont l dministrtion centrle est à Ottw (Ontrio).

3 EARLY GROWTH RESPONSE IN TREES FOLLOWING PEATLAND DRAINAGE G.R. Hillmn nd J.J. Roerts 1 INFORMATION REPORT NOR-X-408 Cndin Forest Service Northern Forestry Centre Pest Mngement Regultory Agency, Room D446, Tupper Building, 2720 Riverside Drive, Ottw, Ontrio K1A 0K9.

4 Her Mjesty the Queen in Right of Cnd, 2006 Ctlogue No. Fo133-1/408E-PDF ISBN ISSN This puliction is ville t no chrge from: Nturl Resources Cnd Cndin Forest Service Northern Forestry Centre Street Edmonton, Alert T6H 3S5 A microfiche edition of this puliction my e purchsed from: Micromedi Proquest 20 Victori Street Toronto, Ontrio M5C 2N8 TTY: (Teletype for the hering-impired) ATS: (ppreil de télécommuniction pour sourds) Lirry nd Archives Cnd Ctloguing in Puliction Hillmn, G. R. (Grhm Roin), Erly growth response in trees following petlnd dringe [electronic resource] / G. R. Hillmn nd J.J. Roerts. (Informtion report ; NOR-X-408) Electronic monogrph in PDF formt. Mode of ccess: World Wide We. Includes strct in French. Issued lso in printed form. Includes iliogrphicl references: p. ISBN Ct. no.: Fo133-1/408E-PDF 1. Blck spruce--alert--growth. 2. Tmrck--Alert--Growth. 3. Petlnd forestry--alert. 4. Forest dringe--alert. I. Roerts, J. J. ( Jessic Jye), II. Northern Forestry Centre (Cnd) III. Title. IV. Series: Informtion report (Northern Forestry Centre (Cnd) : online) NOR-X-408 SD397.B53H C This report hs een printed on Cndin recycled pper. ii

5 Hillmn, G.R.; Roerts, J.J Erly growth response in trees following petlnd dringe. Nt. Resour. Cn., Cn. For. Serv., North. For. Cent., Edmonton, AB. Inf. Rep. NOR-X-408. ABSTRACT The growth of lck spruce (Pice mrin (Mill.) BSP) nd tmrck (Lrix lricin (Du Roi) K. Koch) on two drined petlnds, t McLennn nd Wolf Creek in centrl Alert, ws greter thn on undrined control res 9 10 yers fter dringe. On the drined plots, dimeter growth ws times, height growth times, nd volume growth times tht on the undrined control plots. There were no cler differences in growth mong vrious ditch spcings (30, 40, 50, nd 60 m), nd correltion etween tree growth nd distnce of trees from the nerest ditch ws poor. These results suggest tht drwdown of the wter tle ws sufficient to crete unsturted zones tht fcilitted equitle tree growth cross the strips etween ditches. Tree ring nlyses reveled tht increses in growth could egin s erly s 3 4 yers fter dringe. The successful regenertion of lck spruce on the control plots t McLennn nd the resonle size of lck spruce nd tmrck ingrowth on control plots suggest tht oth species re le to germinte nd survive on wet sites initilly, ut high wter tles inhiit their further development. Additionl periodic mesurements of oth species re necessry to determine long-term growth ptterns fter dringe nd to ssess the finncil fesiility of petlnd dringe s prcticl option in forest mngement. RÉSUMÉ À McLennn et Wolf Creek dns le centre de l Alert, l épinette noire (Pice mrin (Mill.) BSP) et le mélèze lricin (Lrix lricin (Du Roi) K. Koch) ffichent une croissnce supérieure dns deux tourières drinées, 9-10 ns près le dringe, pr comprison à leur croissnce mesurée dns des plcettes témoins non drinées. Dns les plcettes drinées, les ccroissements de l huteur, du dimètre et du volume ont été, respectivement, de 2,7 à 3,5, de 1,6 à 2,3 et de 4,4 à 9,7 fois plus élevés. Aucun effet net de l espcement des fossés (30, 40, 50 ou 60 m) sur l croissnce ne s oserve, et l corréltion entre l croissnce et l distnce des rres du fossé le plus proche est file. Ces résultts semlent indiquer que l issement du niveu de l nppe phrétique été suffisnt pour créer des zones non sturées qui ont fcilité une croissnce comprle des rres dns les ndes entre les fossés. D près des nlyses dendrométriques, l méliortion de l croissnce pourrit déuter 3 ou 4 ns près le dringe. Le succès de l régénértion de l épinette noire dns les plcettes témoins à McLennn et l tille risonnle du recrutement des deux essences dns les plcettes témoins Inf. Rep. NOR-X-408 iii

6 semlent indiquer que ces essences peuvent germer et survivre dns les terrins humides u déut, mis que le niveu élevé de l nppe phrétique inhie suséquemment leur croissnce. Il fudr continuer de mesurer périodiquement les rres des deux essences fin de déterminer les ptrons de croissnce à long terme et d évluer l fisilité finncière du dringe des tourières comme option prtique d méngement forestier. iv Inf. Rep. NOR-X-408

7 CONTENTS INTRODUCTION METHODS Description of Study Ares McLennn Wolf Creek Wter Tle Control McLennn Wolf Creek Smple Plots McLennn Wolf Creek Tree Ring nd Stem Anlyses McLennn Wolf Creek Sttisticl Anlyses RESULTS Chnge in Groundwter Tle Levels Stnd Sttistics Dimeter nd Height Growth Bsl Are nd Volume Growth Comprison of Growth on Drined Plots with Growth on Better Site 8 Tree Ring nd Stem Anlyses Tree Age nd Response to Dringe Ingrowth Regenertion Distnce of Trees from the Nerest Ditch DISCUSSION CONCLUSIONS ACKNOWLEDGMENTS LITERATURE CITED Inf. Rep. NOR-X-408 v

8 TABLES Chrcteristics (s men nd stndrd error) of lck spruce nd tmrck on the McLennn petlnd 1 yer fter (1988) nd 10 yers fter (1997) dringe Chrcteristics (s men nd stndrd error) of lck spruce nd tmrck on the Wolf Creek petlnd efore (1987) nd 9 yers fter (1996) dringe Growth of tmrck nd lck spruce on drined plots t McLennn nd Wolf Creek compred with growth of lck spruce on good, undrined site Chrcteristics (s men nd stndrd error) of lck spruce trees cut t McLennn in Octoer 1994 nd lck spruce nd tmrck trees cut t Wolf Creek in Octoer Men periodic nnul increments, efore nd fter dringe, clculted y the computer progrm STEM for the destructively smpled trees on the control nd drined plots t McLennn nd Wolf Creek Periodic nnul increments for lck spruce nd tmrck on drined res, s reported in Cndin studies FIGURES McLennn ditch network pln, showing loctions of instrumented trnsects nd smple plots Wolf Creek ditch network pln, showing loctions of instrumented trnsects nd smple plots Incrementl dimeter, height, sl re, nd volume of lck spruce nd tmrck Growth response to dringe Current-yer (1994) height growth of lck spruce t McLennn, showing ge response to dringe for 12 trees from the control re (undrined) nd 12 trees from the 50-m spcing re (drined) Dimeter, height, sl re, nd stem density of lck spruce nd tmrck ingrowth Blck spruce nd tmrck regenertion on h smple plots Blck spruce dimeter increment t McLennn nd lck spruce height increment t Wolf Creek, s second-order polynomil functions of distnce from the nerest ditch vi Inf. Rep. NOR-X-408

9 INTRODUCTION In the 1980s, the construction nd expnsion of pulp mills nd swmills in Alert incresed considerly. At the sme time, crown lnds continued to e withdrwn for uses other thn forestry. The predictle decline in the ville wood supply resulting from these ctivities prompted the Alert Forest Service to seek other mens to expnd the forest lnd se for wood fier production. The first nd most ovious considertion ws the 4 x 10 6 h of petlnd supporting stgnnt, noncommercil stnds of lck spruce (Pice mrin (Mill.) BSP) nd tmrck (Lrix lricin (Du Roi) K. Koch) in the province. The ojective of drining petlnd is to provide suitle rooting environment for trees y enhncing soil ertion, soil temperture, nd wter regimes nd y promoting nutrient exchnge etween the soil nd the trees. Petlnd forestry in North Americ is reltively new; consequently, long-term growth nd yield dt for lck spruce nd tmrck growing on such petlnds efore nd fter dringe re scrce. Most of the dt tht re ville for these species were otined y mesuring trees long highwys, rilwys, or griculturl ditches (Päivänen nd Wells 1978; Wng et l. 1985; Trottier 1986; Dng nd Lieffers 1989; Lieffers nd McDonld 1990) or in smple plots on n engineered ditch network (Stnek 1968; Hillmn et l. 1990; Sundström 1992). Although ll the studies cited provide some growth nd yield dt, the mount of long-term ( yers) growth nd yield dt is very limited. In 1985, the Alert Lnd nd Forest Service nd the Cndin Forest Service jointly estlished engineered ditch networks to study the growth of forest stnds fter dringe nd the environmentl impct of dringe on three petlnd types in centrl Alert (Hillmn et l. 1990). The purpose of this pper is to report on the results from two of the study sites, McLennn nd Wolf Creek, otined 9 10 yers fter dringe. Both sites support lck spruce nd tmrck. The McLennn site supports mostly young lck spruce with minor component of older tmrck. At the Wolf Creek site, out two-thirds of the stnd consists of tmrck; the rest is lck spruce. The ojectives of the study were to determine (1) if, t 9 10 yers fter dringe, significntly more growth in dimeter, height, sl re, nd volume, nd significntly more nturl regenertion occurred in lck spruce nd tmrck in drined res; (2) the effects of ditch spcing on these tree growth vriles; nd (3) the functionl reltionships etween distnce of trees from the nerest ditch nd four growth vriles (growth in tree dimeter, height, sl re, nd volume).

10 METHODS McLennn Description of Study Ares The experimentl dringe re is treed fen, chrcterized y og cp in plces, supporting 30- to 60-yer-old lck spruce nd tmrck. Stem densities rnge from 250 to stems h 1 for tmrck nd lck spruce, respectively. The petlnd is locted within the Dry Mixedwood Suregion of the Borel Forest Nturl Region of Alert (Alert Environmentl Protection 1994) out 15 km north of McLennn, Alert, t 55 o 52'N, 116 o 54'W (Fig. 1) nd t n elevtion of 660 m. The men nnul temperture t Pece River ( ) is 1.2 o C, nd the verge Jnury nd July tempertures re 16.6 o C nd 16.0 o C, respectively. The verge nnul precipittion is mm, mm of which flls during My through Septemer; the verge nnul snowfll is cm (Atmospheric Environment Service 2002). The estern portion of the experimentl re slopes gently (0.6%) from the southest towrd string of ever ponds locted to the northwest, wheres the western portion slopes (0.4%) from south to north (Fig. 1). Groundwter flow into the experimentl re is primrily from south nd west. A wter trck defined s vegettion types mrking the pth of minerl-influenced wters through petlnd (Sjors 1948; Heinselmn 1963) locted long the western edge of the experimentl re feeds into the nerest ever pond. One short, well-defined strem chnnel just north of the dringe network lso drins into the ever pond. The soil consists of pet more thn 1.5 m thick, overlying cly. A more detiled description of the experimentl re nd its climte, vegettion, nd soils ws provided y Hillmn (1992). Wolf Creek The experimentl dringe re is locted out 30 km southest of Edson, Alert (53 o 25'N, 116 o 03'W; Fig. 2) t n elevtion of 950 m. It experiences suhumid continentl climte with long, cold winters nd modertely wrm summers. It is occsionlly suject to wrm chinooks during the winter (Dumnski et l. 1972). The men nnul ir temperture t Edson ( ) is 2.0 o C, nd the verge Jnury nd July tempertures re 11.8 o nd 14.6 o C, respectively. The verge nnul precipittion is mm, mm of which flls during My through Septemer; the verge nnul snowfll is cm (Atmospheric Environment Service 2002). The experimentl re, which is out 132 h in extent, lies close to confluence of two Wolf Creek triutries, downstrem of lrge (>2 500 h) treed fen. The fen is ounded on the northest nd southwest y triutries of Wolf Creek (Fig. 2). Before dringe, pet thickness t 42 loctions cross the petlnd verged 1.70 m (stndrd devition 0.88 m; rnge m). The shllow pet lies ner the strem chnnels, nd the deep pet lies ner the center of the confluence re. Pet thickness lso increses upslope from the confluence re, i.e., towrd the southest. Groundwter flows in the direction of the topogrphic slope (0.6%), from southest to northwest, towrd the north triutry of the confluence. Uplnds with minerl soils locted t the south end of the fen provide the fen with stedy wter supply. The petlnd lies within the Lower Foothills Suregion of the Foothills Nturl Region of Alert (Alert Environmentl Protection 1994), nd, s is the cse in much of Alert s forested 2 Inf. Rep. NOR-X-408

11 50 m 50 m 50 m Alert Pece River McLennn Vlleyview Slve Lke 53 Edson Fort McMurry Edmonton McLennn Clgry km C r e e k P 'W P Groundwter well trnsects Tree growth smple plots Wether sttion Bever pond m 55 52'N 30 m 30 m 30 m 40 m Uplnd 40 m 40 m 60 m 60 m Control re Figure 1. McLennn ditch network pln, showing loctions of instrumented trnsects nd smple plots. Inf. Rep. NOR-X-408 3

12 Alert Pece River McLennn Vlleyview Slve Lke 53 Edson Fort McMurry Edmonton Wolf Creek Clgry km W o l f C r e e k 'W Sediment pond N W E S Groundwter well trnsects Tree growth smple plots Wether sttion m 53 25'N 30-m spcing W o l f C r e e k 40-m spcing 50 m 50-m spcing Control re 50 m Figure 2. Wolf Creek ditch network pln, showing loctions of instrumented trnsects nd smple plots. 4 Inf. Rep. NOR-X-408

13 res, the vegettion on the site originted fter fire. Tmrck nd lck spruce, oth open growing nd oth 50 to 60 yers old t the eginning of the study, re the predominnt tree species on the fen with stem densities of nd 800 h 1, respectively. The re ws sujected to intense geophysicl explortion for oil nd gs, nd, s result, the forest is now chrcterized y network of intersecting seismic lines, ech out 7 m wide. Detiled descriptions of soil profiles, soil properties, nd vegettion on the petlnd hve een provided y Mugsh et l. (1993) nd Hillmn (1996). Wter Tle Control The method used to lower nd monitor the wter tle levels ws the sme t oth loctions. A dringe ditch network ws designed, nd lines of trees were cut to provide ccess for the digging mchine. Trnsects were estlished, instrumented, smpled, nd surveyed to determine initil predringe conditions nd to mesure the effects of dringe on groundwter levels, pet susidence, nd other vriles. A Lnnen S-10 digger ws then used to excvte the dringe ditches. Groundwter tle mesurements were tken efore, during, nd fter ditching. Full detils of the groundwter studies hve een provided y Hillmn (1992, 1996). McLennn The design of the dringe ditch network (Fig. 1) ws sed on 30-m ditch spcings in the wter trck re nd 40-m spcings in the remining re. Different ditch spcings were evluted in the southwestern portion of the network. In 1986, efore ditching, five trnsects were estlished, one t loction outside nd out 400 m north of the ditch network nd four t different ditch spcings (30, 40, 50, nd 60 m) perpendiculr to ditch lines in the designted drined re. Construction of the ditch network commenced in the fll of 1986, efore the ground ws frozen, ut construction ws suspended during the winter months. Most of the ditching ws done in June 1987, nd ll work ws completed in July In totl, 30 km of ditches on 90 h ws excvted, resulting in dringe ditch density of 333 m h 1. At the down-slope end of the min ditch, C-shped sediment collector ditch ws constructed to cpture the sediment issuing from the ditches. Wolf Creek In 1986, network of dringe ditches 35 m prt ws mrked out on the selected re, with ccommodtion for control re nd 30-, 40- nd 50-m ditch spcings on the southest portion of the re (Fig. 2). It should e noted from this lyout tht the res contining the 30-, 40-, nd 50-m spcings were not hydrologiclly independent, ecuse there were nine lterl ditches upstrem from the 30-m spcing re intercepting groundwter flow, five ditches upstrem from the 40-m spcing re, nd two ditches upstrem from the 50-m spcing re. This mens tht less groundwter my hve reched the 30-m spcing re thn the 50-m spcing re, which might ffect tree growth response. Groundwter well trnsects were estlished on ech of the three ditch spcings perpendiculr to the ditch lines. In My 1987, control re ws estlished south of nd upstrem from the proposed ditch network. Groundwter tle configurtions were monitored from My through Octoer, 1986 to In fll 1987, the ditch network ws constructed in unfrozen ground nd sediment pond creted t the down-slope end of the min ditch to cpture sediment. An undistured uffer strip seprted the sediment pond from the wtercourse y 130 m. Its purpose ws to trp sediment prticles tht escped the sediment pond. A totl of 20 km of ditches ws dug on 60 h resulting in dringe ditch density of 333 m h 1. The entire network ws completed on 28 Octoer Smple Plots Two types of smple plots were used to mesure tree growth response to dringe (Figs. 1 nd 2). In the first, 5 m x 40 m smple plots were estlished in control re nd in ech ditch spcing re. In the drined res, the long xes Inf. Rep. NOR-X-408 5

14 of the plots were plced prllel to the ditches, centered t the midpoints etween ditches; these re referred to s prllel plots. The second set of plots ws oriented perpendiculr to ditches in the drined res to determine tree growth response in reltion to distnce of trees from the nerest ditch. These plots, with dimensions 5 m x x m (where x equls the distnce etween ditches), re clled perpendiculr plots. On ll plots, live trees with dimeter t rest height (dh) 1.1 cm were tgged with sequentilly numered luminum tgs, nd the tree numer, species, dh, tree height, nd condition (defect) codes recorded (Alert Forest Service 1991). On the perpendiculr plots, the distnce of ech tree to the center of the nerest ditch ws lso mesured. For ech tree, dh ws mesured to the nerest 0.1 cm with stndrd dimeter tpe, nd tree height ws mesured to the nerest 0.1 m with n 8.22-m telescoping height-mesuring pole. Height nd dh were used to determine gross totl volumes from individul tree volume tles for lck spruce nd tmrck (Hung 1994, 1994). The gross totl volume (m 3 ) used in this report is defined s the volume of wood from 0.00 m stump height to 0.0 cm top dimeter inside rk (Hung 1994, 1994). Ingrowth, consisting of those trees with dh 1.1 cm during the current remesurement ut dh < 1.1 cm during the previous mesurement, ws lso tgged nd mesured. A regenerted tree ws defined s ny tree stem 0.16 m or tller to mximum dh of 1.0 cm (Alert Forest Service 1991). A regenertion tlly ws done on 5 m x 10 m regenertion suplot nested within ech min plot, where ech regenertion suplot ws locted t one end of ech min plot. Within ech suplot, ll trees with dh < 1.1 cm were identified nd tllied y species, ccording to the following height clsses: m, m, m, m, nd > 1.20 m. McLennn The 28 plots on the drined re were estlished nd trees were first mesured in August 1988 (Fig. 1). Trees in the 15 control plots were mesured in summer Although the trees in the drined nd control plots were mesured in different yers, the control trees were mesured efore significnt growth occurred in Thus, from tree growth perspective, oth plot types were effectively mesured in All plots nd ssocited regenertion suplots were remesured in fll 1994 nd fll The results of the McLennn study re sed on incrementl growth (dimeter, height, sl re, nd volume) etween 1988 nd 1997, i.e., the response 10 yers fter dringe is sed on 9 yers of growth. Only those trees tht were mesured in 1988 or 1989 nd in 1997 re included in the incrementl growth nlyses. Wolf Creek The 39 plots on the drined re were estlished nd trees were first mesured in Octoer 1986 (Fig. 2). During the first mesurement of trees on the drined re, the height of every third tree ws mesured nd recorded. Susequently, the height of ll trees on the plots ws mesured. Tree heights tht were not mesured the first time were estimted on the sis of dh. Trees on the 12 control plots were mesured in July Mesurements were repeted in the fll of 1993 nd The results for Wolf Creek re reported s incrementl growth etween 1986 nd 1996, i.e., the response 9 yers fter dringe is sed on 10 yers of growth. Tree Ring nd Stem Anlyses After selected trees were felled nd sectioned, disks were otined t heights of 0.0, 0.3, 0.8, nd 1.3 m nd t height increments of 0.5 or 0.75 m therefter. Age nd ring widths were determined from two rdii on ech disk using Holmn digimicrometer nd television cmer. The computer progrms DUFFNO nd STEM, developed y Kvngh (1983), were used to process the resulting dt sets. The STEM progrm ws used to crry out stem nlyses nd generted tles showing verge nnul nd periodic nnul increments for dh, height, sl re, nd volume. Pired nd nonpired t-tests were run to test 6

15 the hypothesis tht there were no differences in dimeter growth etween trees from the drined res nd trees from the undrined res, efore nd fter ditching. McLennn In Octoer 1994, seven growing sesons fter ditching, one lck spruce tree ner ech control plot nd one ner ech of the 28 drined plots were felled nd sectioned for tree ring nd stem nlyses. Also in Octoer 1994, the ges of 12 lck spruce trees in the control re nd 12 lck spruce trees in the 50-m spcing re were estimted from stnding tree height. The trees were susequently felled, sectioned, nd mesured so tht their ges could e precisely determined through ring nlyses. Wolf Creek Twenty-four trees, consisting of three tmrck nd three lck spruce trees from the control re nd from ech of the three ditch spcing res ut outside the plots, were felled nd sectioned in mid- Octoer 1993, six growing sesons fter ditching. Sttisticl Anlyses For oth sites, the two species were ssessed seprtely ecuse of the lrge difference in popultion sizes. They lso grew t different rtes nd responded differently to dringe. The nture of this experiment nd the fct tht it ws conducted on such lrge scle mde it logisticlly impossile to rndomly ssign res within the forest to specific ditch-spcing tretment. Therefore, for nlyticl purposes we ssumed tht the experiment ws sed on completely rndomized design nd conducted one-wy nlyses of vrince (Delwiche nd Slughter 1998) on ll vriles, compring the tretment mens with Scheffé s test. Effects were considered significnt if p RESULTS Chnge in Groundwter Tle Levels At McLennn, the verge depths from the ground surfce to the wter tle efore ditching ( ) were 7, 17, 27, nd 18 cm for the 30-, 40-, 50-, nd 60-m ditch spcing res, respectively. After ditching ( ), the verge depths were 86, 83, 83, nd 91 cm, respectively. The chnges in wter tle levels on the control plots were negligile compred with the chnges tht occurred in the drined re. At Wolf Creek, the verge depths to the wter tle efore ditching ( ) were 17, 16, 6, nd 9 cm for the control nd the 30-, 40-, nd 50-m ditch spcing res, respectively. After ditching ( ), the verge depths were 24, 77, 52, nd 58 cm, respectively. A more detiled description of the results from the groundwter studies ws provided y Hillmn (1992, 1996). Stnd Sttistics A summry of stnd sttistics for lck spruce nd tmrck t McLennn, t the eginning nd end of the mesuring period, sed on dt from ll 43 plots (Tle 1), shows tht there were out 10 times s mny lck spruce trees s there were tmrck. This difference in numers explins the greter per hectre increments in sl re nd volume for lck spruce on the drined re, even though dimeter nd height increments for tmrck on the drined re were 1.7 nd 2.1 times, respectively, those of lck spruce. Although in 1997 the trees were still smll, dringe hd considerly incresed the dimeter, height, sl re, nd volume of oth species. Volume increses on the drined re were 4.1 nd 10.7 times tht on the control for lck spruce nd tmrck, respectively. Inf. Rep. NOR-X-408 7

16 At Wolf Creek, out two-thirds of the stnd consisted of tmrck trees (Tle 2). Growth fter ditching ws greter on the drined res thn on the control, nd greter for tmrck thn lck spruce. Bsl re nd volume increses for tmrck on the drined re were 4 6 times tht of tmrck growth on the control, nd 3 5 times tht of lck spruce on the drined re. Dimeter nd Height Growth At oth sites, dimeter growth of lck spruce nd tmrck on the drined re ws significntly greter (p ) thn on the control re (Fig. 3A). There ws no difference in dimeter growth of tmrck mong the different ditch spcings, ut for lck spruce, the gretest dimeter growth tended to occur with 40-m spcing. Dimeter growth of lck spruce on the drined res ws times tht on the control res, wheres dimeter growth of tmrck on the drined res ws times tht on the control res. As mentioned erlier, the height of only one in three trees on the drined re t Wolf Creek were mesured initilly in Tree heights not mesured the first time were estimted on the sis of dh. The r 2 vlues otined for lck spruce nd tmrck ( nd , respectively) suggest close reltionship etween height nd dh in oth species, nd tht the use of predicted vlues of height in the nlyses did not unduly ffect the results. Height growth of lck spruce nd tmrck ws significntly greter (p ) on the drined re t McLennn nd Wolf Creek (Fig. 3B). With the exception of lck spruce t McLennn, there ws no difference in height growth mong the different ditch spcings. For oth sites, verge lck spruce height growth on the drined re ws times tht on the control re. Tmrck height growth on the drined res ws times tht on the control res. At Wolf Creek, for ll tretments, the height of lck spruce incresed y less thn 1 m over the period Height nd dimeter growth ws gretest for tmrck t McLennn nd lest for lck spruce t Wolf Creek. Bsl Are nd Volume Growth Bsl re growth of lck spruce nd tmrck ws significntly greter (p ) on drined sites t oth McLennn nd Wolf Creek (Fig. 3C). There were lso differences in sl re growth of tmrck mong the different ditch spcings t oth sites nd of lck spruce t McLennn. At oth sites, the verge sl re growth of lck spruce on the drined re ws times tht on the control re. For tmrck, the verge sl re growth on the drined res ws times tht on the control res. Volume growth of lck spruce nd tmrck on the drined res t oth sites ws significntly greter (p < ) thn on the control res (Fig. 3D). There were differences in volume growth mong ditch spcings t McLennn, ut not t Wolf Creek. Averge volume growth of lck spruce on the drined res ws times tht of lck spruce on the control res. For tmrck, volume growth on the drined res ws times tht on the control res. Comprison of Growth on Drined Plots with Growth on Better Site The men nnul increments for dimeter, height, sl re, nd totl volume for lck spruce on drined plots t McLennn nd Wolf Creek were compred with growth of similr-ged lck spruce on good, undrined site (Alert Energy nd Nturl Resources 1985). No dt were ville to mke similr comprisons for tmrck, so tmrck growth t McLennn nd Wolf Creek ws lso compred with lck spruce growth on the good site. The dimeter growth of lck spruce on drined plots compred fvorly with or exceeded tht of lck spruce on the good site (Tle 3). In contrst, height growth of lck spruce t McLennn ws slightly less nd t Wolf Creek ws less thn hlf 8 Inf. Rep. NOR-X-408

17 Tle 1. Chrcteristics (s men nd stndrd error) of lck spruce nd tmrck on the McLennn petlnd 1 yer fter (1988) nd 10 yers fter (1997) dringe Blck spruce Tmrck Chrcteristic Control Drined Control Drined Control Drined Control Drined Dh (cm) 2.4 (0.1) 3.0 (0.1) 3.4 (0.1) 5.1 (0.1) 3.6 (0.4) 4.0 (0.3) 5.2 (0.5) 7.5 (0.4) Height (m) 2.5 (0.1) 2.9 (0.1) 3.0 (0.04) 4.4 (0.1) 3.6 (0.2) 3.8 (0.2) 4.5 (0.3) 6.9 (0.3) Bsl re (m 2 h 1 ) 2.12 (0.46) 2.63 (0.39) 3.57 (0.57) 6.08 (0.63) 0.30 (0.10) 0.63 (0.14) 0.49 (0.14) 1.97 (0.41) Volume (m 3 h 1 ) 2.58 (0.81) 4.55 (0.27) 4.87 (1.00) (0.47) 0.56 (0.19) 1.39 (0.38) 1.11 (0.34) 7.26 (1.60) Stem density (h 1 ) 3387 (479) 2702 (235) 3387 (479) 2702 (235) 235 (74) 347 (62) 235 (74) 347 (62) Only trees mesured in oth 1988 nd 1997 re included in these totls. Ded trees, ingrowth, nd stems with dh < 1.1 cm re not included. Tle 2. Chrcteristics (s men nd stndrd error) of lck spruce nd tmrck on the Wolf Creek petlnd efore (1987) nd 9 yers fter (1996) dringe Tmrck Blck spruce Chrcteristic Control Drined Control Drined Control Drined Control Drined Dh (cm) 5.2 (0.3) 4.5 (0.1) 6.2 (0.3) 6.6 (0.1) 3.4 (0.2) 4.4 (0.1) 4.4 (0.2) 5.8 (0.1) Height (m) 4.1 (0.1) 3.9 (0.1) 4.7 (0.1) 5.5 (0.1) 2.8 (0.1) 3.5 (0.1) 3.2 (0.1) 4.3 (0.1) Bsl re (m 2 h 1 ) 2.54 (0.23) 3.31 (0.24) 3.26 (0.28) 6.37 (0.45) 0.46 (0.08) 1.91 (0.22) 0.69 (0.13) 2.76 (0.26) Volume (m 3 h 1 ) 6.93 (0.77) 8.72 (0.70) 8.91 (0.92) (1.32) 0.71 (0.14) 4.34 (0.64) 0.88 (0.25) 6.57 (0.80) Stem density (h 1 ) 821 (77) 1432 (193) 821 (77) 1432 (193) 396 (65) 895 (67) 396 (65) 895 (67) Only trees mesured in oth 1987 nd 1996 re included in these totls. Ded trees, ingrowth, nd stems with dh < 1.1 cm re not included. Inf. Rep. NOR-X-408 9

18 c c c Dimeter increment (cm) McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck A C c c Height increment (m) Bsl re increment (m 2 h 1 ) 0 McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck c c c McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck B Volume increment (m 3 h 1 ) McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck D Control 30 m 40 m 50 m 60 m Figure 3. Incrementl dimeter (A), height (B), sl re (C), nd volume (D) of lck spruce nd tmrck (s men nd stndrd error). The growth periods for McLennn nd Wolf Creek were nd , respectively. Mens identified with the sme letter do not differ significntly t α = Inf. Rep. NOR-X-408

19 tht of lck spruce on the good site. Bsl re growth of lck spruce t Wolf Creek ws 21% of tht of lck spruce on the good site, wheres t McLennn it ws 84%. The corresponding vlues for volume growth of lck spruce t Wolf Creek nd McLennn were 6% nd 27%, respectively. The dimeter nd height growth of tmrck either exceeded or ws comprle to tht of lck spruce on the good site. Bsl re growth of tmrck t McLennn ws 33% of tht of lck spruce on the good site, wheres t Wolf Creek it ws 75%. The corresponding vlues for tmrck volume growth t McLennn nd Wolf Creek were 17% nd 34%, respectively. The noticele difference in sl re nd volume growth etween the uplnd site nd the two drined sites my e ttriuted, in prt, to the greter density of stems on the good site. There were nerly twice s mny trees on the good site s there were lck spruce trees t McLennn, nd three times s mny s there were tmrck trees t Wolf Creek. Tree Ring nd Stem Anlyses The summry for trees destructively smpled t McLennn nd Wolf Creek (Tle 4) shows tht the verge tree ge rnged from 50 to 70 yers nd tht tmrck growth ws fster thn tht of lck spruce. At McLennn, ring growth of lck spruce during the period ws greter on the drined re thn on the control re (Fig. 4A) 8 yers efore (p < 0.001) nd 8 yers fter (p < 0.001) ditching. On the control re, dimeter growth ws significntly less (p = 0.003) during the postdringe period thn during the predringe period. On the drined re, the difference etween pre- nd post-dringe dimeter growth ws not sttisticlly significnt (p = 0.077), lthough there ws definite tendency for dimeter to increse with time during the lst 5 yers of record. Growth trends for the drined nd control res t McLennn were initilly similr, mintining difference of out 0.4 mm in ring width, up until 2 yers fter dringe, eyond which time they ecme noticely different. Growth rte for ring width on the control res remined sttic etween 1989 nd 1994 t out 0.38 mm yer 1. During the sme period, the growth rte on the drined re incresed y 0.15 mm yer 1 so tht y 1994 the difference in ring width etween the res hd incresed to 1.16 mm. A scn of the 1994 ring widths t different loctions long the stems reveled tht, in nerly ll cses, the widest rings occurred ner ground level (Fig. 4B). In out one-third of the trees, ring widths were greter in the upper portion of the stem thn elsewhere, with the exception of the se (Fig. 4B). At Wolf Creek, the men ring widths t rest height for the 6 yers efore nd the 6 yers fter ditching (Fig. 4C) indicte tht tmrck nd lck spruce trees responded to ditching during the third nd fourth growing sesons fter ditching, respectively. On the drined re, postdringe ring widths were significntly greter thn predringe ring widths for tmrck (p < 0.001) nd lck spruce (p = 0.003). There were lso differences in postdringe ring widths etween tmrck nd lck spruce (p = 0.054). On the control re, there ws no difference etween the pre- nd post-dringe growth rings for either tmrck or lck spruce (p = nd 0.246, respectively). For lck spruce t McLennn nd oth species t Wolf Creek, ring widths incresed with time fter dringe nd showed no sign of leveling off. Further studies re necessry to determine how long these incresing trends continue. Additionl comprisons were mde using 6-yer pre- nd post-dringe verges (Tle 5) clculted y the computer progrm STEM. For the control res, there were no differences in growth of dimeter, height, sl re, or volume efore nd fter dringe, with one exception: t McLennn, predringe dimeter growth of lck spruce ws greter thn postdringe dimeter growth (p = ). For lck spruce on the drined re t McLennn, postdringe growth in dimeter, height, sl re, nd volume were significntly greter (p 0.004) thn predringe growth. On the drined re t Wolf Creek, dimeter nd volume growth of lck spruce were greter fter dringe thn efore (p ). Similrly, dimeter, sl re, nd volume growth of tmrck on the drined re t Wolf Creek ws greter fter dringe thn efore (p < ). Inf. Rep. NOR-X

20 Tle 3. Species nd site Blck spruce Growth of tmrck nd lck spruce on drined plots t McLennn nd Wolf Creek compred with growth of lck spruce on good, undrined site Dh (cm yr 1 ) Height (m yr 1 ) Bsl re (m 2 h 1 yr 1 ) Totl volume (m 3 h 1 yr 1 ) Good, undrined site McLennn Wolf Creek Tmrck McLennn Wolf Creek Height = m t 50 yers rest height ge. Tle 4. Species nd site Blck spruce Chrcteristics (s men nd stndrd error) of lck spruce trees cut t McLennn in Octoer 1994 nd lck spruce nd tmrck trees cut t Wolf Creek in Octoer 1993 n Age (yers) Dh (cm) Height (m) Bsl re (m 2 tree 1 ) Gross volume (m 3 tree 1 ) McLennn (3.4) 4.6 (0.4) 3.9 (0.2) (0.0002) (0.0008) Wolf Creek (8.0) 6.7 (0.8) 4.8 (0.4) (0.0012) (0.0041) Tmrck Wolf Creek (0.8) 8.8 (0.6) 6.9 (0.3) (0.0008) (0.0032) Tle 5. Men periodic nnul increments, efore nd fter dringe, clculted y the computer progrm STEM for the destructively smpled trees on the control nd drined plots t McLennn nd Wolf Creek Dh (cm yr 1 ) Height (m yr 1 ) Bsl re (dm 2 tree 1 yr 1 ) Volume (dm 3 tree 1 yr 1 ) Tretment Before After Before After Before After Before After McLennn, lck spruce Control Drined Wolf Creek, lck spruce Control Drined Wolf Creek, tmrck Control Drined Inf. Rep. NOR-X-408

21 A) McLennn lck spruce Drined Control Ring width (mm) Yers B) McLennn lck spruce Drined Ring width (mm) Rtio of disk height/totl height (%) Ring width (mm) C) Wolf Creek lck spruce nd tmrck Blck spruce, control Tmrck, control Blck spruce, drined Tmrck, drined Yer Figure 4. Growth response to dringe. (A) Ring width t rest height of lck spruce t McLennn, efore nd fter dringe (s men nd stndrd error). n = 15 in the control re nd n = 23 in the drined re. The verticl rrow indictes time of ditching. (B) Men ring widths in 1994 t different loctions on the stems of 14 lck spruce trees from the drined re t McLennn. (C) Ring width t rest height of lck spruce nd tmrck t Wolf Creek efore nd fter dringe. n = 3 in the control re nd n = 9 in the drined re for ech species. The verticl rrow indictes time of ditching. Inf. Rep. NOR-X

22 Tree Age nd Response to Dringe The ility of trees to respond positively to dringe is governed y ge, mong other fctors. It is ssumed tht young, vigorous trees will respond etter thn older, mture trees. This seemed to e the cse for lck spruce t McLennn, where current-yer (1994) height growth decresed from 36 cm in 22-yer-old tree to 12 cm in trees 88 yers nd older (Fig. 5). On the undrined control re, the 1994 height growth ws consistently 3 cm or less regrdless of ge. Ingrowth Dringe hd no effect (p 0.073) on ingrowth (trees 1.1 cm dh etween the first nd current mesurement) dimeter t Wolf Creek, ut significnt differences (p ) in dimeter etween the dringe tretments nd the control were detected t McLennn (Fig. 6A). There were lso differences in dimeter mong the different ditch spcings. Overll, verge ingrowth dimeter ws 1.9 nd 2.4 cm for the control nd drined res, respectively. Dimeter on the drined res rnged from 1.2 to 1.4 times tht on the control res. The verge height of ingrowth ws significntly greter on the drined re thn on the control re (p ), for oth sites nd for the two species (Fig. 6B). At Wolf Creek, ditch spcing hd no effect on ingrowth height, wheres some differences were detected mong ditch spcings t McLennn. Overll, verge ingrowth height ws 2.2 nd 2.7 m for the control nd drined res, respectively. Height on the drined res rnged from 1.1 to 1.4 times tht on the control res. There ws significntly greter sl re (p ) for lck spruce ingrowth on the drined res t oth loctions nd for tmrck ingrowth t McLennn thn occurred on the control re (Fig. 6C). At Wolf Creek, the pttern of sl re ws similr for oth species, with no difference in sl re cross the different ditch spcings. Some differences in sl re mong ditch spcings were oserved t McLennn, notly for lck spruce, for which sl re on the 40- nd 50-m spcings ws 4.7 times tht on the control. Although ingrowth dimeter ws reltively uniform cross the tretments nd species t the two sites (Fig. 6A), this ws not the cse for ingrowth sl re. At McLennn, verge sl re of lck spruce ingrowth ws times tht of tmrck t oth loctions nd tht of lck spruce t Wolf Creek. The wide disprity in sl re per hectre of ingrowth cn e ttriuted to the difference in ingrowth density cross the different tretments t the two loctions (Fig. 6D). The ptterns of sl re nd density of ingrowth were similr, indicting tht sites with greter numer of ingrowth stems per hectre will produce greter sl re per hectre thn sites with fewer stems. At McLennn, ingrowth etween 1988 nd 1997 rised the stnd density of lck spruce to nd stems h 1 on the control nd drined res, respectively. The stnd density of tmrck incresed to 435 nd stems h 1, respectively. At Wolf Creek, the dditionl stems incresed tmrck densities to 944 nd stems h 1 on the control nd drined res, respectively. Blck spruce densities incresed to 546 nd stems h 1, respectively. Regenertion The numer of stems < 1.1 cm dh recorded for oth species t the two loctions during the finl mesurement session vried considerly ( stems h 1 ), with the dominnt species t ech loction producing the gretest numer of stems per hectre (Fig. 7). Tmrck regenertion t oth loctions nd lck spruce regenertion t Wolf Creek showed the sme generl trends detected for the other growth vriles, i.e., production on the drined res ws greter thn on the control res. Thus, verge regenertion on the drined res ws times tht on the controls. At McLennn, however, lck spruce regenertion on the control re ws 70% greter thn on the drined re. Noticele differences in regenertion were lso recorded etween the perpendiculr nd prllel plots. On ll tmrck plots (with the exception 14 Inf. Rep. NOR-X-408

23 of tmrck on the re with 60-m spcing t McLennn) nd on the lck spruce plots t Wolf Creek, the rtio of regenertion on the perpendiculr plots to regenertion on the prllel plots rnged from 1.2 to 6.6. At McLennn, the rtio for lck spruce rnged from 0.7 to 0.9. Thus lck spruce regenertion t McLennn ws greter on the prllel plots for ll ditch spcings. The stndrd errors for tmrck regenertion t Wolf Creek were lrge (Fig. 7), indicting tht there ws gret vrition mong plots within prticulr tretment. Distnce of Trees from the Nerest Ditch Attempts to find significnt correltions etween distnce of trees from the nerest ditch nd the vrious growth vriles using liner, log, polynomil, nd exponentil functions were generlly unsuccessful. At McLennn, for exmple, the correltions of dimeter increments versus distnce from the nerest ditch for lck spruce (Fig. 8A) were significnt (p < 0.01), ut the regressions ccounted for only 0.9% to 28% of the vrition. Similr regressions were run for tmrck, ut the results were questionle, ecuse of the smll numer of tmrck trees in the perpendiculr plots. At Wolf Creek, the est correltion for height increment of lck spruce ws otined with second-order polynomil for the 40-m spcing, where distnce of trees from ditch ccounted for 13% of the vrition (Fig. 8B). For the 30- nd 50-m spcings, distnce of trees from ditch ccounted for 3% nd 6% of the vrition, respectively. Polynomils derived for dimeter increment of lck spruce indicted tht, on the 30-m spcing, 35% of the vrition ws ssocited with distnce of trees from ditch, wheres on the 40-nd 50-m spcing, distnce of trees from ditch ccounted for 4% nd 10% of the vrition, respectively height growth (cm) Stump ge (yers) Drined Undrined Figure 5. Current-yer (1994) height growth of lck spruce t McLennn, showing ge response to dringe for 12 trees from the control re (undrined) nd 12 trees from the 50-m spcing re (drined). Inf. Rep. NOR-X

24 c c Ingrowth dimeter (cm) McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck A c c McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck C Ingrwoth height (m) Ingrowth sl re (m 2 h 1 ) c McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck B c c c Ingrowth stem density (h 1 ) McLennn Wolf Creek McLennn Wolf Creek Blck spruce Tmrck D Control 30 m 40 m 50 m 60 m Figure 6. Dimeter (A), height (B), sl re (C), nd stem density (D) of lck spruce nd tmrck ingrowth (s men nd stndrd error). Ingrowth consists of stems (dh 1.1 cm) tht grew into the plots etween 1988 nd 1997 t McLennn nd etween 1986 nd 1996 t Wolf Creek. Mens identified with the sme letter do not differ significntly t α = Inf. Rep. NOR-X-408

25 Regenerted stem density (h 1 ) McLennn Wolf Creek Blck spruce McLennn Wolf Creek Tmrck Control 30 m (pr) 30 m (perp) 40 m (pr) 40 m (perp) 50 m (pr) 50 m (perp) 60 m (pr) 60 m (perp) Figure 7. Blck spruce nd tmrck regenertion (stems with dh < 1.1 cm) on h smple plots (s men nd stndrd error). Pr = prllel plots, perp = perpendiculr plots. Inf. Rep. NOR-X

26 Dimeter increment (cm) A) McLennn A B A 30 m; r 2 = B 40 m; r 2 = C 50 m; r 2 = D 60 m; r 2 = C D Distnce from ditch (m) 30 m 40 m 50 m 60 m Height increment (m) B) Wolf Creek A A 30 m; r 2 = B 40 m; r 2 = C 50 m; r 2 = B C Distnce from ditch (m) 30 m 40 m 50 m Figure 8. Blck spruce dimeter increment t McLennn (A) nd lck spruce height increment t Wolf Creek (B), s second-order polynomil functions of distnce from the nerest ditch. 18 Inf. Rep. NOR-X-408

27 DISCUSSION The results reported here show tht, in lck spruce nd tmrck, dimeter increments of up to 4.0 cm nd height increments of up to 3.5 m cn e chieved 9 10 yers fter tretment when petlnd dringe is used s mens of promoting forest growth. Bsl re of 4 m 2 h 1 nd gross totl volume exceeding 10 m 3 h 1 were ttined for oth species. Generlly, tmrck tended to grow fster thn lck spruce. These results were compred with those of other Cndin petlnd dringe studies. For this purpose, the results from ll studies re summrized s periodic nnul increments (Tle 6). In some of the studies, the effects of fertiliztion were investigted s well. Tle 6, however, records only dt from drined nd unfertilized plots. The growth periods for the studies shown rnged from 5 to 40 yers. Growth in dimeter, height, nd sl re for lck spruce t McLennn nd Wolf Creek compred fvorly with growth oserved in the other Cndin studies, ut volume growth in the current study ws 0.53 times or less thn tht recorded elsewhere (Tle 6). Blck spruce volume increses (per tree) in Alert, however, cn rech up to 28 times the predringe volume, especilly in very young trees (Wng nd Micko 1985; Wng et l. 1985). Differences etween results otined t McLennn nd Wolf Creek nd those otined in estern Cnd re to e expected ecuse the climtes of the two regions re different. In generl, the trees in the estern Cnd studies were older nd lrger thn those in the current study. Differences in stnd densities my lso e contriuting fctor when compring differences in growth in sl re or totl volume. Tmrck is not fully utilized y the forest industry in Cnd, nd consequently, growth dt for this species re scrce; for tmrck on drined sites, ville dt re even more limited. Two studies, one in Queec nd one in Alert, provide some informtion out tmrck growth on drined sites (Tle 6). In n evlution of different ditch spcings (20, 40, 60, nd 80) on tll-sedge nd tmrck swmp ner Quéec City, conducted 5 yers fter ditching, Trottier (1991) found tht the increses in dimeter nd height growth were proportionl to dringe intensity. Increses in dimeter rnged from 36% to 84%, nd increses in height from 36% to 68%. The increse on the control plot ws 15% nd 10% for dimeter nd height, respectively. In Alert, stem nlyses of very young tmrck showed tht pertree volume increses yers fter dringe my exceed 80 times the predringe volume (Wng nd Micko 1985). Height nd dimeter growth of lck spruce nd tmrck in the current study were generlly s good s or etter thn the corresponding growth of lck spruce on good uplnd, undrined site (Tle 3). Bsl re nd totl volume growth were etter on the uplnd site. The greter stnd density on the good site proly contriuted to the greter vlues recorded there. The increses in totl volume growth for lck spruce nd tmrck reported in this study re considered to e primrily the result of incresing the depth of the soil ertion zone through dringe nd, to lesser extent, opening up the stnd for the dringe ditches. The ltter effect my ecome more importnt t nrrower (10 to 20 m) ditch spcing, when even more trees would e removed to ccommodte the ditches. Bell (1986) reported tht cutting 7.3-m-wide seismic lines (for oil nd gs explortion purposes) in Alert resulted in increses in rdil increment of 15% to 20% in white spruce (Pice gluc (Moench) Voss) nd lck spruce, within distnce of onehlf dominnt height from the stnd edge fter 10 yers, where the dominnt height is defined s the verge height of trees with crowns extending ove the generl level of the cnopy nd receiving full light from ove nd prtly from the sides. The improved tree growth ws ttriuted to the greter vilility of nutrients, moisture, spce, nd sunshine. Inf. Rep. NOR-X