E x t e n s i o n N o t e # 3 5 M a r c h 2 0 0 1

RESEARCHISSUE GROUPS

Soil Conservation

Wildlife Habitat

Hydrology

Forest Health

Reforestation

Stand Tending

Ecosystem Inventory andClassification

Biodiversity

Silvicultural Systems

Guideline Verification

Extension

INTRODUCTION

This project was developed toaddress the challenge of extractingcommercial timber from the MontaneSpruce (MS) and Sub-Boreal Pine–Spruce (SBPS) zones in the westcentral interior of B.C., whilemaintaining suitable habitat forpopulations of northern caribou, anecotype of woodland caribou(Rangifer tarandus caribou).

Within the Cariboo Forest Region,northern caribou are considered akey management species. Under theCariboo-Chilcotin Land Use Plan (ahigher level plan under the ForestPractices Code), about 20% (202,000ha) of caribou habitat will becomeavailable for timber extraction using“modified harvesting” practices. Inwinter, caribou feed primarily onterrestrial and arboreal lichens in lowelevation forests in the MS and SBPSzones. Caribou prefer mature andold lodgepole pine (Pinus contorta)forests with abundant terrestriallichen and low snow depthfor easy cratering. Caribou also seekout mature to older spruce (Piceaengelmannii x glauca) and pinestands, often adjacent to wetlands

and meadows, where arboreal lichenis concentrated.

Clearcutting is the standardsilvicultural system for lodgepolepine forests. Harvesting removes thearboreal lichen and, without asubstantial snow pack, mayphysically damage the terrestriallichen. The terrestrial lichen can alsobe damaged by site preparationtechniques and by changes inmicroclimate. Removal of theoverstory canopy allows increasedlight and frost frequency, as well asextreme fluctuations in humidity andtemperature. Lichen dispersal,establishment, and growth are slowand it may take many decades beforethe quantity of terrestrial lichenwithin a clearcut is comparable toold stands. Even more time isrequired to restore arboreal lichenbiomass.

For these reasons, alternativesilvicultural systems are being testedfor their effectiveness in reducing theimpact of harvesting on caribouhabitat, particularily on importantlichen forage species. Before thealternative silvicultural systems arerecommended, other issues such as

Itcha – Ilgachuz AlternativeSilvicultural Systems Project:Microclimate, Planted Stock andNatural Regeneration

tree regeneration, windthrow,wildlife diversity, tree insectsand diseases and long-termproductivity must also beinvestigated. This researchproject provides the opportunityto study each componentrelative to the others and willresult in an integrated resourcemanagement solution.

OBJECTIVESThis extension note describesthird and fourth year resultsregarding short-term impact ofgroup selection and irregulargroup shelterwood silviculturalsystems, using whole-tree andstem-only harvesting methods,on:• micro-climate• survival and growth of

planted lodgepole pine andhybrid white spruceseedlings; and

• natural regeneration ingressrate

SITE DESCRIPTION ANDCLASSIFICATIONFive harvest blocks wereselected from Riverside ForestProducts Ltd. development areasouth of Punkutlaenkut Creekin the West Chilcotin. Theblocks are on a gently rolling,high elevation plateau nearSatah Mountain (52°28’N, 124°43’W), about 12 km south ofthe summit of the Itcha Range.The two lowest elevation blocks(1320 and 1360 m) are in theSubBoreal Pine - Spruce VeryDry Cold (SBPSxc) Subzonewhile the three higher elevationblocks (1430, 1520, and 1640m) are in the Montane SpruceVery Dry, Very Cold (MSxv)Subzone. The stands in theseblocks are even-aged, single-

layered lodgepole pine stands,typical of these two subzones.No other tree species are foundon the SBPS blocks, but a fewhybrid white spruce andsubalpine fir occur on the MSblocks. Undergrowthvegetation is low-growing anddominated by kinnikinnick(Arctostaphylos uva-ursi),lichens, and patches ofpinegrass (Calamagrostisrubescens). Relatively fewvascular species occur, but arich variety of lichens, primarilyCladonia species, are present.The undergrowth vegetation onMSxv zonal sites is dominatedby crowberry (Empetrumnigrum), grouseberry(Vaccinium scoparium),mosses, and lichens.

EXPERIMENTAL DESIGN ANDTREATMENTSThe experimental design is arandomized block. Each of fiveharvest blocks was divided intofour, approximately equal-sizedtreatment units (about 15 haeach). Three harvestingtreatments (described below)and an unlogged control wererandomly assigned to the fourtreatment units within eachblock. Clearcuts, adjacent tothe trial blocks, were includedin the planted stock trial andmicroclimate monitoringproject. Harvesting was done inwinter to reduce physicaldamage to the lichen.Harvesting on all blocks beganin January 1996 and wascompleted in April.

Treatments 1 (T1) and 2 (T2)are irregular group shelterwoodsilvicultural systems where thetarget area removal was 50% insmall openings 20–30 m in

diameter. The residual standprovides shelter for terrestriallichen. The two treatmentsdiffer by method of harvest:

• Treatment 1 (T1): StemOnly Harvesting (SOH).Trees were felled and piledusing a feller-buncher. Thetrees were delimbed,topped, and cut-to-length atthe stump with a processor,then moved to roadside bya forwarder. Slash waspiled to minimize theamount of lichen coveredand maximize the numberof plantable spots. Thistreatment has considerablymore slash in the openingsthan Treatment 2.

• Treatment 2 (T2): WholeTree Harvesting (WTH).Trees were harvested usingconventional equipmentand methods (feller-buncher, grapple skidder,and roadside processing).Roadside processinginvolved delimbing, pilingand burning the debris.Terrestrial lichens could bedisturbed by skidding ofwhole trees to roadside.Also 3–7% of the treatmentunit is occupied by a right-of-way processing area;however, less slash is left inthe openings to affectterrestrial lichens and thereare a wider range ofplanting sites.

Treatment 3 (T3): Stem OnlyHarvesting (SOH). This is agroup selection silviculturalsystem treatment based on a33% area removal in 15 mdiameter openings. Thistreatment was harvested using

the system described forTreatment 1.These study blocks will bemanaged on a longer rotationthan is currently used forlodgepole pine (80 years) orspruce (120 years). On theirregular group shelterwoodunits (T1 and T2), the second50% of the block will beharvested in approximately 70years. The first 50% of theblock is expected to be readyfor second harvest in 140 years.For the group selectiontreatment (T3), the cutting cycleis 80 years, at which time afurther 33% of the area will beharvested. The first 33% of theblock is expected to be readyfor a second harvest after 240years.

STAND DESCRIPTIONAll blocks associated with thistrial have no previousmanagement history. All standswere likely initiated after stand-destroying wildfires between160 and 220 years ago.Lodgepole pine regenerationafter wildfire in these subzonesis typically rapid and notaffected by competing shruband herbaceous vegetation. Theresulting stands are mostlyeven-aged and single-layered.General dryness of the sites andperiodic mortality due tomountain pine beetle result inmoderately open stands in theSBPSxc. Patches of young pineregeneration are common inthese stands, although theyrarely reach into the maincanopy. In the MSxv, fewertrees are killed by mountainpine beetle so stands tend to bemore closed and clearly single-layered, with little natural

regeneration beneath thecanopy.

MICROCLIMATEMicroclimate has a very strongeffect on survival, conditionand growth of seedlings in theMS and SBPS zones. Sixclimate stations were set up,starting in 1997, in blocks 1, 3and 5. Soil and air temperatureprofiles (15 cm soil, 1 cm soiland 15 cm air) were measuredin three openings (one perblock) in the 50% WTHtreatment and three adjacentclearcuts. The centre, south andnorth edges of each openingwere measured while in theclearcuts two profiles, 10 mapart, were monitored. Datapresented in Table 1 are basedon the mean of the profiles byblock and treatment.The study blocks are harshgrowing sites for trees becauseof frequent growing seasonfrosts. In the clearcuts, 49% ofthe nights have averagetemperatures below 0°Ccompared to 37% in the partialcuts. Frosts, sufficiently severeto cause significant tissuedamage (-4°C), also commonlyoccur on the clearcuts (18% ofthe nights). This was reducedto 5% in the partial cuts.Growing degree days (measureof available heat formetabolism) and July soiltemperatures indicate that soilsin the clearcuts are warmer thanthe partial cuts in all blocks andall years. Within the openingsthe centre and sunny edges are1-2 °C warmer than the shadyedges. The soil data from 1999and 2000 shows that block 5,the highest elevation block, iscooler than either block 1 or 3.Data from 1998, a low snow

year, found that the soil in therooting zone dropped belowfreezing (down to -3°C) formost of the winter in all blocksand both treatments. This couldcause root damage andtherefore affect seedlingperformance. In the deepsnowpack year (1999) the soilremained closer to 0°C due tothe insulating effect of thesnow. The soils on theseresearch sites are colder thanthose documented in the IDF,ICH and SBS in the CaribooRegion, perhaps resulting inslower tree growth rates.

Microclimate SummaryThe number of severe frostevents is greatly reduced in thepartial cuts compared to theclearcuts. However, shadingwithin the openings causescooler soil temperaturesespecially on the shady edges.The cooler soils in block 5 mayreduce tree growth especially inthe partial cut. Years with lowsnowfall increase the risk ofground freezing and rootdamage.

PLANTED STOCKThe trial plots were springplanted in 1997 with thefollowing stock types: PSB415B SX 1 + 0 and PCT 415BPL 1 + 0. A total of 4,694 treeswere planted in the five blocks.In treatments, T1, T2 andclearcut there are 6 plots eachcontaining 41 trees while in T3there is 10 plots containing 25trees. The plots were pairedwithin each treatment unit basedon species.

Survival and condition

Survival of seedlings wascompared between treatments.

Survival of spruce was lower

Table 1. Summary of microclimate data recorded in clearcuts (CC) and partial cuts (PC)

Year Subzone Elev.(m)

Block Treatment Sample period Min. 15 cm airtemperature

Average 15 cm soiltemperature

No. of nights Growingdegree days

July

(<0°C) (<-4°C) (>5°C) (°C)1997 SBPSxc 1290 1 CC June 5 – Sept 24 74 26 648 11.8

PC (112 days) 51 12 545 11.3MSxv 1420 3 CC 53 12 656 11.8

PC 34 5 472 10.01998 SBPSxc 1290 1 CC May 1 – July 31` 40 15 544 14.5

PC (92 days) 32 4 495 13.8MSxv 1420 3 CC 29 6 533 14.3

PC 23 2 413 12.51999 SBPSxc 1290 1 CC June1 – Sept 16 56 28 621 11.4

PC (108 days) 45 12 600 11.2MSxv 1420 3 CC 43 13 648 11.4

PC 34 3 509 10.1MSxv 1620 5 CC 54 21 451 10.5

PC 38 7 401 9.22000 SBPSxc 1290 1 CC June 1 – Sept 13 57 33 654 12.5

PC (105 days) 44 8 573 11.8MSxv 1420 3 CC 52 10 625 12.2

PC 41 1 470 10.7MSxv 1620 5 CC 60 21 518 11.4

PC 44 2 350 9.4

overall in the clearcuts (76%)than in all partially cuttreatments (90-93%) (Fig. 1).Spruce survival was highlyvariable between clearcuts,ranging from 40% in block 5 to98% in block 3. Survival ofpine was similar between partialcuts and clearcuts (93 – 96%).Comparisons were also madebetween the treatments based oncondition (good, fair, or poor).The proportion of pine in eachcondition class did not vary bytreatment but spruce trees in the50% harvest treatments weremore likely to be in goodcondition (43%) compared toeither the clearcuts (18%) or30% harvest treatment (28%).

Condition was examined inmore detail by looking at the

stem, foliage and leaders of theseedlings. Stems were healthy(>87%) but the foliage andleaders, especially on the sprucetrees showed environmentalstress. The spruce foliage waschlorotic on 16-21% ofseedlings in the clearcuts and50% partial cuts, while itaveraged 33% in the 30%

treatment. Also, a largeproportion of the spruceseedlings had dead buds due tofrost in the clearcuts (40%);however, this was reduced inthe partial cuts (10-13%). Incontrast, the foliage wasgenerally healthy (73-76%) forthe lodgepole pine planted in alltreatments. For spruce, 73-78%

0

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100

clearcut 50%SOH 50%WTH 30%SOH

Treatment

Per

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pine spruce

Figure 1: Survival of pine and spruce in clearcuts and partial cutsfour years after planting

of the leaders were rated healthyregardless of partial cuttingtreatment; however, only 48%were healthy in the clearcuts. Inthe clearcuts, there was a highproportion of terminals thatwere dead (43%) due to frost.In the partial cuts, there werealso dead terminals (7-13%). Incontrast, more than 82% of thepine trees had healthy leaders inthe partial cuts and 76% in theclearcuts. Ungulate browsingwas noticeable in all treatmentunits, especially on the pine (6-11%).

Height and ground leveldiameter growthAccumulated height anddiameter growth of theseedlings, from 1997 - 2000, aresummarized by treatment inTable 2. At the end of thefourth growing season, heightgrowth of spruce wassignificantly greater in the threepartially cut treatments than inthe clearcuts while growth ofpine was not significantlydifferent. Spruce diametergrowth was marginally differentamong treatments due to lessgrowth in the 30% SOH

treatment compared to all othertreatments. The ground leveldiameter of pine wassignificantly larger in theclearcuts compared to all partialcuts. There are no significantdifferences between treatmentsfor the leader growth of pine in2000 (5 – 7 cm), or for spruceleader growth (4 – 6 cm) (Table2). Total height and totaldiameter of the seedlingsfollows the same pattern as forgrowth. Based on the fourthyear leader length, pine willreach the free-growing heightrequirement in the MS (1.0 m)by 15 years in all treatments butthis is less likely in the SBPSwhere the height requirement is1.4 m, unless the growth rateaccelerates. Spruce is expectedto reach the free-growing heightrequirement of 0.8 m in bothsubzones.

Planted Stock Summary

1. For pine, the method ofpartial harvesting (SOH orWTH) and amount harvested,have not affected survival orcondition. The height growthof planted pine is similar

between the partial cuts andclearcuts, although partialshading from thesurrounding stand is causingsome etiolation of theseedlings. Diameter growthis better in the clearcuts, butis not unreasonable in thepartial cuts. Based on currentdata, all treatments aresuccessfully regenerating;however, there is someconcern that the free-growingheight requirement of 1.4 mat 15 years in the SBPS maynot be met unless the growthrate accelerates in alltreatments.

2. To date, spruce survival andgrowth are variable in theclearcuts. Survival andgrowth are poor due to froston blocks that are very flat.Damage due to frost is muchlower in the partially cuttreatments in all blocks.There is some indication thatspruce is growing more andthe condition is better in the50% harvest treatmentscompared to the 30% harvesttreatments, perhaps due tobetter light conditions.

Table 2. Analysis of variance models and treatment means (least square) for: total height growth (2000 height –planting height), leader length (2000), total diameter growth (2000 diameter – planting diameter) andannual diameter growth (2000) of live seedlings. Treatment means with dissimilar letters aresignificantly different at a=.05.

Species Variable (cm) Treatment means pT1 - 50%

SOHT2 - 50%

WTHT3 - 30%

SOHClearcut

Pine Height growth 4 yrs 19.7 20.3 18.7 16.5 .36Leader length 6.7 6.9 5.4 6.8 .30Diameter growth 4 yrs .28b .30b .23b .46a .0001Diameter growth 1 yr .08b .09b .06b .20a .0005

Spruce Height growth 4 yrs 17.5b 20.2b 15.0b 9.9a .003Leader length 5.3 5.7 3.7 3.6 .16Diameter growth 4 yrs .32 .37 .25 .36 .06Diameter growth 1 yr .09 .10 .06 .12 .21

3. The chlorotic foliage on thespruce seedlings, especiallyin the SBPS blocks and 30%stem-only-harvestingtreatments, indicate aninability of the trees toobtain adequate nutrition.Poor root development, lackof nutrients in the soil, ordry conditions inhibiting themovement of nutrients tothe roots could all beresponsible for thiscondition.

To conclude, in caribou habitat,partially harvested blocksshould be regenerated mostlywith lodgepole pine. Sprucecould be planted on shady southedges, wet microsites, or onedges where mistletoe is aconcern. Sites originallydominated by pine should notbe converted to spruce since theconsequences to terrestriallichen production (caribouforage) are unknown.NATURAL REGENERATIONUntil recently, clearcut blocks inboth the MS and SBPS zoneswere most often left for naturalregeneration followingharvesting. This is still the casein the SBPS, but currently in theMS blocks are typically plantedto ensure adequate stocking andshorten the time to free growingstatus. The objectives of thenatural regeneration studies areto test whether naturalregeneration will adequatelyrestock partially cut stands andto assess the effects of theharvesting treatments andbiogeoclimatic unit on naturalregeneration.

In order for natural regenerationto be successful there must besufficient seed, adequate

germination, and survival ofgerminants. Three studies havebeen undertaken to evaluate thepotential for naturalregeneration: seed inputfollowing tree harvesting, thecontinuation of seed rain afterharvesting, and the rate ofnatural regeneration ingress.

Input of seed followingharvestingIn order to determine if therewere differences in seeddensities related to harvestingmethod, cones were collectedfrom 20 – 0.5m² plots (one peropening) in T1 (50% SOH) andT2 (50% WTH) treatment unitsin blocks 1, 3, and 5. Asubsample of cones was openedand the seed was counted andcut to determine the number offilled (potentially viable) seedsper cone.

The literature suggests thatserotinous lodgepole pine coneson the ground after harvestingwill open quicker and morecompletely than cones elevatedabove the ground, due todifferences in warming. Theamount of filled seed on theground in serotinous cones wasmuch greater after whole treeharvesting (2.8 M seeds/ha) thanafter stem only harvesting(905,000 seeds/ha). For bothtreatments however, most(>85%) of the cones are elevatedin slash piles either at theroadside (whole treeharvesting), or in the harvestedopenings (stem only harvesting),rather than on the ground.Skidding of whole trees to theroadside leaves numerous coneson the ground, but the majorityare piled in slash at the roadsideand later burned. With stem

only harvesting, slash remainson site potentially making farmore seed available (up to 23.1M seeds/ha if all of the conesopened). However, the amountof slash and the position ofcones within the slash mayrestrict the amount of seedreleased and the availability ofsuitable seedbeds.

In blocks 1 and 3 more than86% of the cones on the groundhad released their seed bySeptember of 1996, one growingseason after harvest. In block 5,release of seed from cones onthe ground was lower (46%)than in blocks 1 or 3, possiblydue to the cooler temperatures.Across all blocks, seed releasefrom cones in elevated slash(20-60 cm above ground)ranged from 13 –35% andaveraged 24%. Release fromcones attached to branches onthe ground ranged from 40%(lower side of branch) to 73%(upper side of branch). Seedfrom elevated slash is less likelyto land on a suitable seedbedthan is seed that falls from coneson branches, or from individualcones on the ground.The effect of opening size onseed release was comparedbetween the 30% SOH (15 mdiameter openings) and the 50%SOH (26 m diameter openings)using class 1 cones (new,closed). By the end ofSeptember, there were noapparent differences betweentreatments for the amount ofseed released from coneswhether on the ground, onbranches, or in elevated slash.

Seed rainThe majority of lodgepole pineseed is found in serotinous

cones; however, a portion isreleased annually from non-serotinous cones. From 1997-1999, seed rain from residualtrees on block 3 was monitoredusing 10 traps in each of thefollowing treatment units:unharvested control, 30% SOHand 50% SOH. In the harvestedtreatments, traps were placed inthe harvested openings. Seedwas removed in May of eachyear, then counted and cut todetermine the number of filledseed. Seed rain varied betweenyears from a low of 47,000seeds/ha in 1997 to a high of137,000 seeds per ha in 1998.The amount of filled seedchanged annually, ranging from42 – 60 %. The proportion offilled seed generally increasedwith the size of the seed crop.Figure 2 shows no consistentdifference between thetreatments over the years.

IngressThis study was designed toevaluate natural regenerationdensities within openings in thevarious harvesting treatmentsand to test whether differencesare related to harvestingtreatment or biogeoclimaticzone.

The number of seedlings under130 cm tall were monitoredfrom 1996 to 1999 in permanentsample plots located in allblocks and harvested treatments.Monitoring will continue forseveral more years. About 50 –2 m² plots were established priorto harvest in each treatment unit.Following harvest, regenerationwas monitored in 188 plotslocated completely withinopenings; sample size rangedfrom 8 to 17 plots per treatmentunit. The number of seedlingswere tallied in each of the

following age/size classes byspecies: < 1 year, > 1 year but <10 cm tall, and > 10 cm but <130 cm tall. Data werecompared to regenerationingress data that were collectedpreviously from clearcuts in the

MS and SBPS.

Third year data indicate thatseedling densities wereconsistently higher on blocks inthe SBPS than in the MS zoneregardless of treatment.Regeneration densities weresimilar in the 50% SOH and50% WTH treatments in bothbiogeoclimatic units. In theSBPS zone, seedling densitieswere similar in the 50% SOH(26 m diameter openings) and30% SOH (15 m diameteropenings) units despite

differences in opening size. Inthe MS zone however, densitieswere substantially lower in the30% SOH, indicating that naturalregeneration at high elevationsmay be slow in small openings.

Regeneration densities in thesepartial harvest treatments weresimilar to third year regenerationdensities recorded previously inclearcuts in the MS and SBPSzones (Fig. 3). However,densities of germinants < 1 yearold is greater than in theclearcuts of the same age,indicating that seed rain fromadjacent residual trees maycontinue to increase seedlingdensities beyond that typical ofclearcuts.

Natural Regeneration

0

50,000

100,000

150,000

200,000

250,000

1997 1998 1999

See

ds

per

ha

control 50%SOH 30%SOH

42% filled

70%filled

60% filled

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SBPS MS SBPS MS SBPS MS SBPS MS

Ste

ms/

ha

Germinants < 1Yr

Seedlings >1Yr

Treatment 1 Treatment 2 Treatment 3 Clearcut Reference (not scarified)

Figure 2: Annual seed rain in block 3 treatments (control,50%SOH, 30%SOH)

Figure 3: Mean density of germinants (<1 year old) andseedlings (>1 year old) by harvesting treatment andbiogeoclimatic unit, three years after harvest

Summary1. Both methods of harvesting

(stem only and whole tree)leave many seed-bearingcones on the ground toinitiate a new stand.Although the number ofcones on the ground ishigher in the WTH treatment(treatment 2), more conesare left on site in the slash(piles and on branches) inthe stem-only harvestingtreatment (treatments 1 and3).

2. Opening size did not affectthe amount of seed released;however, fewer cones onthe ground opened in block5. Microclimate dataindicate that block 5 iscooler than other blocks (1and 3) where temperatureswere recorded.

3. Non-serotinous cones onadjacent residual treessupply an annual rain ofseed onto the harvestedopenings to initiate newgerminants.

4. Based on third year data,natural regeneration

densities are similar to thoserecorded after three years inclearcuts. It appears thatadequate stocking will likelybe achieved in the SBPS andin larger openings in theMS; however, naturalregeneration of the smallopenings (15 m) may beslow in the MS.

5. The extended rotation timeand long cutting cyclesbeing used in thesesilvicultural systems couldmake the use of naturalregeneration economicallyfeasible.

ACNOWLEDGEMENTS:

Funding for this research projectis provided by Forest RenewalBC and the Ministry of Forests.

Partners for this project include:

• The Ministry of Forests,Chilcotin Forest District

• Riverside Forest Products• Clusko Logging• The Ministry of

Environment Lands andParks.

We would also like to thank BobStathers for collecting themicroclimate data.

CONTACT:

Michaela Waterhouse, R.P.F.,R.P. Bio.Silvicultural SystemsResearcher(project administration andplanted regeneration)(250) 398-4405Michaela.Waterhouse@gems4.gov.bc.ca

Nola Daintith, R.P.F.Regeneration Forester(250) 398-4350Nola.Daintith@gems6.gov.bc.ca

Ordell SteenResearch Ecologist(natural regeneration)(250) 398-4409Ordell.Steen@gems9.gov.bc.ca

Harold Armleder, R.P.F.,R.P. Bio.Wildlife Habitat Ecologist(caribou strategy and timberharvesting)(250) 398-4407Harild Armleder@gems6.gov.bc.ca