The Opax Mountain Silvicultural SystemsProject: Preliminary Results for ManagingComplex, Dry Interior Douglas-fir Forests

Extension Note72

David J. Huggard517 E. 10th StreetNorth Vancouver, BC V7L 2E7

André Arsenault, Alan Vyse, and Walt Klenner B.C. Ministry of Forests Southern Interior Forest RegionKamloops, BC V2C 2T7

Abstract

The Opax Mountain Silvicultural Sys-tems project explores managementoptions for some of the issues facingmanagers of complex forests in thedry Interior Douglas-fir (IDF) bio-geoclimatic zone. The project includestwo study areas: one in the IDFxh

variant and one in the IDFdk. Eacharea has six operational-scale harvesttreatments: uncut control; %removal of merchantable volumeusing individual tree selection (ITS);% ITS; % ITS with uncutreserves; % removal using a mix-ture of patch cuts of ., ., and .ha; and 50% removal with patch cutsof a similar nature as the % removal.The project includes studies of:• fire history and other natural dis-

turbance agents;• regeneration in openings and

under partial canopy;• edge effects on microclimate,

snowmelt, and soils;• effects of canopy density, gap sizes,

site preparation, and edges onplanted seedlings, natural regener-ation, and vegetation (includingcover layers, individual species, andgroups such as forage plants,weeds, soil seedbanks, and ectomy-corrhizal hosts); and

• harvest treatment effects and habi-tat relationships of wildlife groups,including terrestrial invertebrates,arboreal beetles, small mammals,songbirds, woodpeckers, and ungul-ates.We summarize results for many of

the individual studies at Opax Moun-tain, dealing with the important man-agement issues of natural disturbanceregimes, regeneration, management ofvegetation resources, and conserva-tion of biological diversity in man-aged dry IDF stands. Naturaldisturbances at the site cover a widespectrum of sizes, frequencies, severi-ties, and effects on stand structure.Responses of the many study variablesshow that no one management treat-ment will maintain all valued compo-nents in the IDF forest. Together,these results support the use of arange of management practicesbroader than the current uneven-agedmanagement widely practicedthroughout the dry IDF biogeoclimat-ic zone. In particular, patch-cut systemswith openings >. ha, or extendedrotations to permit the developmentof large live trees, snags, and coarsewoody debris would complementindividual tree selection systems.

Ministry of Forests Forest Science Program

Introduction

Variability and Management of theInterior Douglas-fir (IDF) ZoneForests of the dry Interior Douglas-fir(IDF) biogeoclimatic zone (Lloyd etal. 1990) of British Columbia areamong the most variable in theprovince. Although often dominatedby a single tree species (Douglas-fir),the forests show great regional andfine-scale variation. Regionally, IDFforests are denser and more produc-tive in the central Interior, and moreopen and patchy, and slower-growing,in the drier southern Interior. Thestructure and composition of IDFforests also varies with elevation,from upper-elevation IDF stands thatgrade into dense lodgepole pinestands of the Montane Spruce (MS)biogeoclimatic zone, to open standsadjacent to the low-elevation openPonderosa Pine (PP) or Bunchgrass(BG) biogeoclimatic zones. At upperelevations and in northern areas ofthe IDF zone, spring frosts play animportant limiting role for Douglas-fir, while summer drought is a keyfactor at lower elevations.

Structures of IDF stands are oftencomplex and can include large, widelyspaced trees with open understories,dense thickets of small trees, or vari-able mixes of patchy overstory andunderstory trees (Figure ). Slope,aspect, drainage, soil depth, andunderlying geology all affect standstructure. In addition, a wide range ofnatural disturbances affect thesestands, including: lightning; stand-replacing, moderate-severity, andlight understory fires; endemic andperiodic outbreaks of western sprucebudworm, Douglas-fir tussock-moth,Douglas-fir bark beetle, and mountainpine beetles; and other disturbanceagents, such as root rots and wind-throw. Periodic harvesting and annuallivestock use over the past centuryhave also shaped stand structure.

Despite this natural variability,

drier IDF forests throughout thesouthern Interior have traditionallybeen managed using uniform partialcutting. When regulated harvestingwas first introduced years ago, low-volume removals were prescribed andstems were marked to ensure that ahealthy residual stand was retained.As the demand for timber increased,economic pressures changed harvest-ing to a diameter-limit system. Thiswas easier to administer but oftenresulted in poor-quality retained treesand concern about long-term recruit-ment. More recently, stem markinghas returned in an attempt to retainor create a desired size distribution oftrees. With increased scrutiny offorestry practices, ever more complexguidelines have been introduced toregulate harvesting and regeneration

of partially cut IDF stands with theintent of creating a multi-aged stand(Klenner and Vyse ). Recent driversfor harvest include large- and small-scale salvage following wildfire andmountain pine beetle outbreaks.

This approach to managing IDFforests has created two problems.First, the regulations are cumbersome,and not conducive to results-basedforestry. More importantly, no singleapproach is likely to successfully meetthe wide range of objectives forestersare now responsible for: harvest eco-nomics, regeneration, forest health,biological diversity, water quality, andother forest resources. Specific man-agement issues in the IDF zone havehighlighted problems with widespreaduse of uniform partial cutting:• Lack of regeneration in some par-

Stand structure in the IDFxh2 varies greatly.

tially cut stands is an operationalconcern. While shading by retainedtrees should reduce dry conditionsthat threaten regenerating trees,root competition for water by resid-ual trees may be a more importantchallenge to regeneration.

• At the same time, there is uneaseabout some very dense stands withpoor growth, low understory pro-ductivity, and high fuel loading.

• Planting is used to remedy regen-eration problems, but grass com-petition for moisture (Heinemanet al. ) and frost damage haveled to many plantation failures.Site preparation can be used toreduce competition and frost, butit is expensive and difficult toapply following partial cutting.

• Multi-layer stands are susceptibleto attack by western spruce bud-worm. This contributes to a wide-spread perception of an ongoing“decline” in forest health in theIDF zone.

• Production of forage for cattle isanother responsibility of forest man-agement throughout the IDF zone,which may not be best addressedwith uneven-aged systems.

• Many species in the IDF zone alsorely on forest features difficult tomaintain with uniform partial cut-ting, such as large snags or inter-spersed openings and densepatches.

• The multi-layered stand structurecreated by uniform partial cuttingrepresents only a small part of therange of conditions that wouldhave arisen historically throughnatural disturbances.

The Opax Mountain Silvicultural Systems ProjectMotivated by these concerns, researchersestablished the Opax Mountain projectto examine partial cutting and alter-native ways to manage dry IDF forests.The project is one of several silvicul-

tural systems projects in BritishColumbia. All share the idea that themost reliable way of providing practi-tioners with the information theyneed to make responsible decisions isby comparing treatments with a repli-cated experimental design at an oper-ational scale. Research at thesilvicultural systems sites is multi-dis-ciplinary to address the many respon-sibilities faced by applied users. TheOpax site also developed as aresponse to a direct conflict betweenforesters, who viewed the area as aneasily accessible timber source, andpublic groups concerned with envi-ronmental values. The large-scaleresearch site helped resolve the con-flict by allowing some timber harvest-ing, while providing information toimprove management in the longterm and fostering communication.This Extension Note presents anoverview of the project, initial results,and preliminary interpretations forpractitioners and the interested public.

Study SiteThe Opax Mountain site is located

km northwest of Kamloops, B.C. Thesite contains two adjacent study areasof about ha each: one at –

m elevation in the IDFxh variant(Mud Lake) and the other at –

m in the IDFdk2 variant (OpaxMountain). Both sites have highly var-ied topography, creating ecosystemsthat range from numerous small wet-lands and a wide variety of foresttypes, to dry rocky outcrops associatedwith old volcanic flows. The IDFdk2study area has about one-third lodge-pole pine mixed with Douglas-fir,while lodgepole pine is rare and local-ized in the IDFxh site, which borderson grasslands. Aspen occurs in scat-tered patches and spruce grows insome wetter areas (Bealle-Statland). Selective logging took place atlower elevations during a short periodof homestead settlement from to

. Much of the study area was againlogged in – when most of thelarger and better-formed stems wereremoved and milled on site.

The two study areas at OpaxMountain were each divided into sixexperimental treatment units ofabout ha, with the following treat-ments applied in a randomized-blockdesign (Figure ):. Uncut control (D & I). % merchantable volume removal

using uniform partial cutting (F & L). % area removal using small patch

cuts of ., ., and . ha (C & K). % uniform removal (B & G). % removal with patch cuts (E & J). % uniform removal over % of

the block, with the remaining %as uncut reserves (A & H).The area was harvested in winter

– with the co-operation ofthe Ministry of Forests Small BusinessProgram. The uniform partial cutswere not implemented with the stan-dard operational prescription of equalremoval across the diameter distribu-tion. Instead, a diameter-limitapproach was used to remove largertrees. As well as allowing comparisonsof uniform versus patch removal, theintent was to test the effects of remov-ing particular stand structures such aslarge stems and snags. Comparisonsof pre- and post-harvest permanentsample plots showed that all treat-ments removed the intended volume,except that .% of the volume wasremoved in the % uniform treat-ments (Bealle-Statland ). The dis-crepancy was due to low precision inthe initial cruise plots that were usedto establish the diameter limits.

To remove the confounding influ-ence of livestock grazing on vegetationsuccession and regeneration, cattlewere excluded from the area with thehelp of professional horse riders duringthe first eight years of the study, andthereafter by a barbed wire fence thatwas installed around the study area.

The Isobel project, a complementary study that integrates livestockgrazing into the monitoring design,was implemented in (Klenner) in an adjacent area.

Two experimental ground distur-bance treatments (mechanical scarifi-cation and prescribed burn) wereapplied to subplots within the mainharvesting treatments to examine veg-etation and regeneration response.

In unharvested forest and in thelarge patch-cut openings (. ha), threelevels of downed wood were createdexperimentally to examine the habitatrelationships between downed woodand small mammals. To achieve theselevels, downed wood (> cm in diame-ter) levels were manipulated to createhigh, moderate, and low downed woodconditions (Craig ) in randomlychosen areas of residual forest and the.-ha patch cuts. Two additional treat-ment units were added to the originaldesign to ensure that three replicateswere available for this study (M & N).

The multi-disciplinary work atOpax Mountain examines natural dis-turbances, stand structure, microcli-

mate, soils, tree regeneration, vegeta-tion, and wildlife species. Researchershave taken three general approaches todealing with the natural variability ofIDF stands and the effects of the har-vest treatments:

. Natural disturbances and standstructure: Studies of fire, insects, andother disturbances examined how thevariable structure of IDF forests arose.The “ecosystem management”approach contends that forest man-agement should “mimic natural dis-turbances.” While it would be verydifficult and costly to mimic allaspects of natural disturbances in the

IDF zone, we can learn from naturaldisturbances to help develop manage-ment objectives for many values. Hownatural disturbances interact withmanagement actions is also critical forunderstanding the long-term structureand condition of managed IDF stands.

. Canopy closure, gaps, and edges:For many resource values, the patchyIDF forest is best seen as a continuumof canopy closure and canopy gaps ofdifferent sizes. This approach is espe-cially well suited to studies of regener-ation and vegetation that are closelytied to light, water availability, and soilconditions. Harvesting can create new

Site overview of the Opax Mountain Silvicultural Systems project.

Composition of treatments by “gap classes”.

gaps, enlarge others, or reduce canopyclosure. From this perspective, patchcuts are just larger gaps. Larger open-ings also create edge effects into theopening or into forest.

The patchy uncut forest at theOpax site includes about % densecanopy, % moderate canopy, %open canopy or small gaps, % gapsof about m2, and % large natu-ral or historical openings (Miège et al.). Light partial cutting changesthis distribution by substantiallyincreasing the area in the two largergap sizes. Heavier partial cuttingincreases the number of these largegaps (Figure 3) and reduces theamount of denser canopy closure.Patch cuts produce large gaps, whilehaving less effect on small gaps anddenser canopy closure.

. Overall silvicultural systems treat-ments: Studies of mobile wildlifespecies examined the effects of theoverall silvicultural systems treat-ments on the abundance, demogra-phy, or behaviour of selectedindicator species. Additional worklinked some species to the habitat ele-ments that harvesting affects.

Results

Natural Disturbance Agents

Studies of fire, insects, and other distur-bances seek to understand how the vari-able structure of IDF forests arose, andto provide information to help guidemanagement. Windthrow is an addi-tional direct post-harvest concern.

Fire: Our initial fire history resultsat Opax suggest that low-, moderate-,and high-severity fires have occurredin a complex pattern across the locallandscape over the last years. Forexample, the mean fire return intervalvaried between and > years(Arsenault and Klenner ). TheIDFxh site has experienced more fre-quent fires than the IDFdk2 site, butexamples of all three types of fireseverity are present at both sites.

Insects: We detected seven spruce bud-worm outbreaks over the last years(Campbell et al. ). Again, these out-breaks varied in space and time. We arecurrently examining the relationshipbetween fire events, spruce budworm,and climate over the last years.Mountain pine beetle outbreaks have alsoaffected the upper part of the study area,and the whole site has likely experiencedDouglas-fir bark beetle mortality and theeffects of several species of root disease.

Windthrow: Post-harvest wind-throw was high in the uncut controland % ITS units in the IDFdk studyarea due to their exposure (Miller andMaclauchlan ; A. Vyse, unpub-lished data). Lodgepole pine hadslightly higher windthrow rates thanDouglas-fir where the speciesoccurred together, and the wind-thrown pine tended to be larger(Miller and Maclauchlan ). Wind-throw was – times greater within m of the edges of .- and .-haopenings, but not affected by .-hapatch cuts. However, this edge effectdid not amount to higher overallwindthrow rates in the patch-cuttreatments compared with ITS.

Windthrown trees were used by bothprimary (tree-killing) and secondarybark beetles, with % of down lodge-pole pine attacked and % of Douglas-fir (Miller and Maclauchlan ).However, this did not appear to con-tribute to attacks on live trees, as smallendemic patches of Douglas-fir beetlewere not associated with windthrow(Miller and Maclauchlan ). Wind-throw and endemic bark beetles at thesite have moderate, patchy effects onstand structure. A recent outbreak ofmountain pine beetle is killing lodgepolepine in the IDFdk site, but the net effecton the stand has yet to be evaluated.

Natural disturbance agents – sum-mary: The wide variation in historicaldisturbances does not support the cre-ation or maintenance of a multi-lay-ered stand across extensive areas inthe IDF zone. The application of a uni-form, all-aged management system

will not reflect the range of variabilityin structure and pattern of the forestcreated by historic natural disturbances.Nor is it likely to be the best manage-ment option in the face of expectednatural disturbances such as fire, west-ern spruce budworm outbreaks, or rootdisease. The variety of disturbances alsomakes it very difficult to predict howwell any silvicultural system in the IDFzone will perform in the long term.Some issues associated with this uncer-tainty will be addressed by long-termoperational trials like the Opax study.

Microclimate and Soils

Measurements of snow, soil tempera-ture, moisture, and nutrients help inunderstanding what conditions areneeded for tree growth, as well as howsuitable managed stands are for othervegetation and wildlife.

Snowmelt: Snowmelt showed a pro-nounced but short edge effect assoc-iated with harvested openings.Mid-winter snow depths were typical-ly cm deeper across openings thanin the forest. In late winter, snowdepths dropped cm within m ofthe northern (south-facing) edge.They remained about cm deeperup to m into the opening on theshaded north-facing side (Figure )(Huggard et al. ). These differ-ences in exposure lead to an averagesnow-free date nearly a month earlieralong the northern edge than on thesouthern edge of openings. Earlierbare ground may lengthen the grow-ing season for trees and other vegeta-tion, but may also lead to droughtlater in the summer.Soil temperature: In the summer, soiltemperatures showed a similar edgeeffect, with temperatures at cmdepth oC higher than the average onthe northern edge of openings, andoC lower on the southern edge (Fig-ure ) (Bissonnette and Lloyd ).Both edge effects disappeared by minto the opening.

Study variables, approaches, and methods at the Opax Mountain Silvicultural Systems site

Study variable Approach Method

Growth and yield Treatments Periodic measurements in permanent sample plotsStand development Treatments Age and growth reconstructed from tree rings

and stem analysis, projections using computermodels

Fire regime1 Across site Reconstructed from tree rings using fire scars andtree age as indicators

Douglas-fir defoliators2 Across site Reconstructed from tree rings, corrected forannual climate effects

Bark beetles Treatments Species and abundance of arboreal beetles recordedusing multiple funnel traps, bark- and wood-boringbeetles associated with blowdown

Windthrow Treatments, edges Transect surveys 3 years after harvest

Soil temperatures Edges Thermocouples across edges

Soil moisture3 Edges Moisture blocks across edges

Snow depth and duration Treatments, edges Mid-winter and spring snow depth transectsSoil chemistry, N4 Treatments, edges Chemical and N availability measures on forest

floor and mineral soil samples

Decomposition Treatments, edges Mass loss of litter bagsAdvanced regeneration Treatments Periodic measurements of abundance and height

growth of seedlings established before harvestSeedfall Treatments, edges Abundance of tree seeds recorded by species in

traps along transectsPlanted Fd, Pl, and Py Openings, under Periodic measurements of survival and growthseedlings canopy using operational surveysSeedlings and planted seeds Gap size, edge, Germination, survival, and growth of planted

site prep seedlings and seeds (some protected with mesh)Natural regeneration Treatments, gap size Ingress in vegetation and site prep regeneration

plotsSeedling bank Patches of seedlings Age and radial growth reconstructed from tree age structure5 rings, height growth measured by internode lengthVascular plants6 Gap size, edge, Species, % cover, and height recorded in plots on

site prep transects, gap classes, site prep trialsLichens and bryophytes Gap size, edge, % cover of selected species and groups

site prepSoil seedbanks7 Patch cuts, leave Vegetation plots, soil samples, and species of

strips germinants from soil samples in greenhouse trials

Ectomycorrhizal fungi Host associations Root samples of tree and shrub species

Habitat elements Treatments 5.6 m radius plots, CWD intercept transectsWoodpeckers8 Treatment, edge, Transect counts, nest, and foraging observations

habitat using radio-telemetrySong birds Treatment Abundance and species recorded using point

count surveysWinter use by mammals Treatment, edge, Snow-track surveys

habitatSquirrels, mice, and voles9 Treatment, edge, Live trapping, habitat plots, radio-telemetry, and

habitat CWD manipulation experiments.

Long-toed salamanders Treatments Pitfall trapping and pond surveysShrews and terrestrial Treatment, edge, Pitfall traps, habitat plotsinvertebrates habitat

Arboreal beetles Treatments Funnel trapsStand dynamics simulations Treatments Computer modelling of stand structure using

different management scenarios1Superscript numbers are related to the following study photos.

Illustrations of the range of studies being conducted at the Opax site. Numbers relate to superscripts in Table 1.

1Fire regime 2Douglas-fir defoliators

3Soil moisture 4Soil chemistry, N

5Seedling bank age structure 6Vascular plants

7Soil seedbanks 8Woodpeckers

9Squirrels, mice, and voles

Microclimate and soils – summary:Soil moisture: Potential drought stressfor plants, measured by soil waterpotential, was very high in openingsat the northern edge, and was alsohigh at the southern edge (Orchansky). However, soil water potential m into the opening was onlyslightly greater than values in theuncut forest. The high drought stressat all locations in late summer, exceptin wet microsites, indicates that mois-ture may limit productivity.Nitrogen: Mineralized nitrogen wasincreased by both partial and patchcuts, primarily in the form of nitrate(NO3) (Figure ) (Hope et al. ).The nitrification effect was apparentwithin m into the opening. Theincrease in nitrate was not due toincreased litter decomposition, whichremained constant across the openingand into the forest (Figure ) (Hope etal. ). Altered microbial activity dueto carbon changes and reduced uptakeof nitrate by trees are possible explana-tions for the increase in NO3. Increasedavailability of nitrogen in the openingscould promote seedling growth duringthe first year, but would likely besequestered by grasses in subsequentyears. Other nutrients showed minoror no changes in the harvested areas(Hope and Prescott ).

Natural Regeneration

Studies of seedfall, germination, naturalingress, and growth and survival ofadvanced regeneration assess the contri-bution of natural regeneration to silvicul-tural objectives as well as increase ourunderstanding of IDF forest dynamics.

Seedfall: Douglas-fir seedfall occurredfrequently but irregularly. Over years, it was abundant in years andnearly absent in years. About .

times more seed fell at the IDFxh

site (Arsenault and Vyse ). Theamount of seedfall was not affectedby the uniform selective cutting, sug-

gesting that the crowns of retainedtrees expanded and produced moreseed. Low amounts of pine seedfallevery year suggest that the cones aremostly serotinous.

Seedfall declined rapidly across theedges of the patch-cut treatments.Over the first 5 years of seedfall mon-itoring, seedfall was . viable seedsper square metre per year in theuncut forest, . at the edge of open-ings, . at m into openings, and .

at over m into openings.In addition, a sowing experiment

using Douglas-fir seeds showed veryhigh rates of seed consumption(>%). Even seeds protected with

Edge effects in snow depth (left) and summer soil temperatures (right), from forest on the north side (south-facing edge)through 1.6-ha openings into the south forest (north-facing edge). Values are differences from the overall mean value of thevariable. Curves have been fitted to show the researchers’ interpretation of the original data (shown by symbols).

Edge effects in two forms of mineralized nitrogen (µg/g), and in litter decom-position (% of standard litter samples remaining after 3 years).

small mesh grid from vertebrates(small mammals and birds) were con-sumed at high rates (–%) (Doneyand Lloyd ).Natural regeneration: Post-harvest nat-ural regeneration was extremely irregu-lar. Only % of plots had newseedlings years after harvesting, sug-gesting that suitable conditions forregeneration are infrequent and dependon particular combinations of weath-er and seedfall. After the high seedfallin the IDFxh site in the fall of ,many germinants were observed on theforest floor on a variety of seedbeds inthe control and uniform cover treat-ments. However, very few survived thesubsequent hot dry summer.

In a comparison of natural ingressin screefed, lightly burned, and undis-turbed experimental plots, screefedsites had natural seedlings perhectare, while burned and undisturbedplots had less than per hectare(Doney and Lloyd ). Survival ofthese natural seedlings after years waslow (% in screefs, % in burns).Advanced regeneration: Advancedregeneration was abundant in theIDFdk study area and moderatelyabundant in the IDFxh zone.• Mean density was highest in the con-

trol and decreased in the ITS treat-ments with increasing harvest levels(Table 2) (Kaipainen et al. 1998).

• The occurrence of regenerationwas very patchy. At the IDFxh

site, almost one third of regenera-tion plots had no regeneration, and% had more than five seedlings per-m2 plot. The proportion ofempty plots was lower in theIDFdk site (%) and the propor-tion of plots with more than fiveseedlings was much higher (%).

• Height growth of advanced regen-eration over post-harvest yearswas greatest in the % ITS unitsand in the controls (Table ) (P.Puttonen, unpublished data).

Natural regeneration – summary: Cur-rent management practices in the IDF

zone assume that natural regenerationwill be rapid and well distributed, butwe found the reverse. Pre-harvestingadvanced regeneration can occur inhigh densities and responds well afterlogging, but was very patchy, and wasdestroyed in the larger openings. Nat-ural regeneration after harvesting wasabsent in the larger openings, but,even in the ITS treatments, ingresswas slow because seedfall was erratic,seed consumption was high, and ger-mination was poor after hot dry sum-mers. Exposure of mineral soilincreased germination but smallseedlings did not tolerate drought.

Planted Seedlings

Planting is widely used to enhance andensure regeneration of large openings.Survival and growth were tracked forthree species of conifer seedlings plant-ed in openings and under differentcanopy conditions in partial cuts.

Seedlings in openings: Three species ofseedlings—Douglas-fir, ponderosapine, and lodgepole pine—wereplanted in mechanically preparedscreefs in openings.• Within a species, survival rates

were the same, but growth wasslightly better in .-ha openingsthan in smaller patch cuts (Table )(A. Vyse, unpublished data).

• Lodgepole pine had substantiallyhigher survival and growth at bothstudy areas than Douglas-fir andponderosa pine.

• Growth of all species was moder-ately higher at the IDFxh studyarea.

• By far the fastest-growing trees atthe Opax Mountain site are aspenwhere these have resprouted natu-rally. They have already become amajor structural feature in someopenings.

Seedlings in partial cuts: Seedlingswere planted in small mechanicallyscreefed spots in the % uniformresidual stand at the IDHxh2 site years after harvesting. The patchycanopy of the residual stand providedan opportunity to study the perform-ance of three species of plantedseedlings under a full range of canopyclosure. Survival of Douglas-fir,lodgepole pine, and ponderosa pinewas relatively high except under nearlycomplete canopy closure (Table )(Vyse et al. ). All three species

Density and growth of advanced regeneration and natural regeneration ingress insix silvicultural systems treatments, and in IDFdk versus IDFxh

Treatment Control ITS 20% 20% patch ITS+res ITS 50% 50% patch dk/xh

Advanced regen (/ha) 4149 3522 657 2371 1972 709 4.3

Ht. growth (%, 4 yr) 64 44 40 40 84 44 2.1

Nat. regen (/ha, 4 yr) 2450 650 500 950 1125 475 0.4

Note: green = best option(s), yellow = somewhat worse, orange = poor.

Performance of operationally planted seedlings in screefed sites in three openingsizes, and in IDFdk versus IDFxh

Species Measure 0.1 and 0.4 ha 1.6 ha dk/xha

Fd and Py Survival (%, 4 yr) 74 74 1.1

Diameter (mm, 5 yr) 28 33 0.7

Height (cm, 5 yr) 121 124 0.7

Pl Survival (%, 4 yr) 92 92 1.0

Diameter (mm, 5 yr) 36 48 0.8

Height (cm, 5 yr) 192 230 0.8

Note: green = best option(s), yellow = somewhat worse, orange = poor.aValue in IDFdk/value in IDFxh.

showed declining growth rates ascanopy closure increased, with substan-tial declines even under –% closure(Table ). The reduced performancemay be due to shading, but tree per-formance could also be strongly affect-ed by root competition for limited soilmoisture with retained trees and withpinegrass.Planted seedlings – summary: Withscreefing to reduce vegetation compe-tition, all three conifer species arelikely to meet regeneration objectivesin both variants. Lodgepole pine per-formed better (survival and growth)in both variants, but it should not berelied on exclusively for regenerationof openings in the IDF zone, for sev-eral reasons:

. It is nearly absent naturally inthe IDFxh study area, suggesting thatit may not do well in the longer termin that variant.

. The structural variation pro-duced in stands dominated by Doug-las-fir is an important ecologicalcharacteristic of the IDF zone.

. A recent mountain pine beetleoutbreak in the Opax area suggeststhat widespread promotion of lodge-pole pine–dominated second-growthstands may be a risky strategy.

Planted seedlings can be grownunder canopy where required to meetstocking standards, and, in theselower-light situations, Douglas-firdoes as well as lodgepole pine. Grow-ing-season frost is rare at the site; ourresults may not apply to parts of theIDF zone where frost is an issue.

Vegetation

Individual plant and lichen species are amajor component of biodiversity, andvegetation offers habitat for wildlife,potential competition for conifer regen-eration, cattle forage, hosts for mycor-rhizal fungi, and a source of weedspecies. Vegetation studies examinedeffects of canopy closure and gap size,small site preparation treatments, andchanges across the edges of openings.

Vegetation response to gap classes: Veg-etation cover layers and speciesgroups showed various responses togap classes:• Shrub and herb cover, and lichens

to a lesser extent, were most abun-dant under open canopy and insmall gaps, and were sparse underdense canopy (Table ) (Miège etal. ). Rose was most commonin gaps of any size. Spirea wascommon in all treatments exceptunder dense canopy closure. Rat-tlesnake plantain was one of only afew vascular plant species closelyassociated with dense or moderatecanopy closure.

• The percentage cover of the lichenPeltigera declined in large gaps andpatch cuts.

• Bryophytes, including the domi-nant Pleurozium, were also mostabundant under moderate canopyclosure, and were least abundant inopenings of any size. Mossesdeclined mainly where substrateswere disturbed in openings.

• Cover of forage plants was slightlygreater in small and moderateopenings, but was also high inlarge openings and patch cuts, withpinegrass the dominant foragespecies.

• Occurrence rates of ectomycor-rhizal fungi on tree and shrubspecies measured at the site (Dur-rall and Gillespie ; Hagermanet al. ) were combined withcover of these species (Miège et al.) to index ectomycorhizzal

Performance of three species of seedlings planted under different levels of canopyclosure

Canopy closure (%)

0–20 20–40 40–60 60–80 80–100

Fd+Py survival (%, 4 yr) 85.0 81.2 82.5 86.0 71.2

Pl survival (%, 4 yr) 92.2 93.0 77.2 80.1 73.8

Fd height (cm, 4 yr) 42.4 28.8 23.6 16.0 11.2

Py height (cm, 4 yr) 59.2 38.0 28.0 22.0 22.8

Pl height (cm, 4 yr) 88.0 59.2 49.2 34.0 25.6

Note: green = best option(s), yellow = somewhat worse, orange = poor.

Cover of vegetation layers, functional groups, and species in six canopy closureand gap classes, and in IDFdk versus IDFxh (5 years after logging)

Canopy closure/gap classa

Variable 1 2 3 4 5 6 dk/xh

Shrub cover (%) 5.4 9.3 12.3 11.4 9.9 8.7 0.8

Herb cover (%) 17.3 31.5 41.4 44.3 38.0 35.0 0.9

Bryophyte cover (%) 7.4 10.9 8.0 4.9 3.7 3.1 0.9

Lichen cover (%) 0.4 1.3 0.9 1.0 0.5 0.1 2.3

Forage cover (%) 21.2 33.8 46.6 48.5 42.3 41.0 0.7

Weed cover (%) 0.4 0.9 2.8 4.1 5.4 5.1 0.2

N-fixer cover (%) 1.7 3.5 4.6 5.7 4.8 2.3 0.9

EMR fungi hosts (index) 10.0 6.9 4.4 2.1 1.2 0.8 0.8

Rose (%) 1.0 1.0 2.0 3.0 1.9 2.3 0.3

Spirea (%) 0.9 2.3 3.1 2.0 3.3 2.5 0.8

Pinegrass (%) 8.5 11.0 18.5 17.9 15.8 16.2 1.0

Rattlesnake plantain (%) 0.2 0.2 0.1 0.1 0.0 0.0 0.7

Pleurozium (%) 2.4 4.3 2.9 0.7 0.2 0.0 0.7

Peltigera (%) 0.3 0.4 0.4 0.4 0.2 0.1 0.8

Species richness (species/16 m2) 28.3 31.1 29.6 29.0 29.7 27.9 0.8

Note: green = best option(s), yellow = somewhat worse, orange = poor, red = serious concern.aSee legend in Miège et al. (2002) for definition of canopy closure/gap classes (1 = most dense/dark, 6 = very open/bright).

host potential (Table ). These hostspecies decreased in burned areas,and showed a strong negative trendin abundance with increasingopenness or gap size (Table ).

• The abundance of introducedweedy plants increased withincreasing gap size. Weeds (intro-duced species) were more abun-dant in the IDFxh. Overall, smallgaps provided the best mix of veg-etation cover, including cattle for-age, with fewer weeds than largeropenings.

Vegetation – site preparation effects: Asexpected, all vegetation cover layers werereduced in the short term by burningand screefing, even though these experi-mental treatments were at very lowintensities. Vegetation condition in thedifferent treatments recovered at differ-ent rates (Table ) (Miège et al. ).On the burn plots, the overall cover ofshrubs, herbs, and forage plants recov-ered to control levels by year , but thescreefed plots remained at lower levels.Most common vascular species followedthe same pattern, as did rarer species(such as rattlesnake plantain) that aremostly associated with forest cover. Thecover of bryophytes, lichens, and nitro-gen-fixing plants did not recover sub-

stantially following either the burn orscreef treatment.Vegetation cover and species – edgeeffects: Vegetation measurementsacross edges generally differed betweenopenings and forest, usually with asharp change. Only a few variablesshow edge effects that extend morethan m into either the opening orthe forest (Brand and Lloyd ):• Tree cover 6 years after harvest was

slightly elevated in both screefed andundisturbed sites for a few metresinto the opening, and reduced slight-ly into the forest (Figure 7) (Brandand Lloyd 2001). This findingreflects seedfall into the opening,

and some windthrow disturbanceof the forest edge.

• Moss cover recovered slightly fromscreefing along the shaded part ofthe opening, but did not recover inopenings more than 10 m from theedge.The most notable edge effect on

vegetation species was an increase inpinegrass in hand-screefed plots, anda corresponding increase in forageproduction, – m into the opening(Figure ) (Brand and Lloyd ).This increase in pinegrass in screefsafter years is probably still insuffi-cient to cause competition problemsfor seedlings planted shortly after har-vest. The peak on the northern edge isunique to the the site preparationtreatment and requires further investi-gation. Reduced vegetation cover wasalso noted in openings within 5 m ofsome edges (e.g., early seral species)(Figure ), probably due to root com-petition for water with the adjacentretained trees. This root competitionat edges could reduce planted seedlingperformance, but this effect is notapparent in the operational planting.

During the 4-year post-harvestperiod, the percentage cover of weedsdid not increase in forest adjacent topatch cuts (Brand and Lloyd 2001).Species associated with older forestretained forest abundances at 6 minto the opening, but then mostly dis-appeared at greater distances (Figure8). Other vegetation species showed

Response by vegetation cover layers to edges of harvested 1.6-ha openings.

Cover of vegetation layers, functional groups, and species in three site preparationtreatments (3 years after site preparation), averaged across all crownclosure/gap classes

Variable Control Burn Screef

Shrub cover (%) 10.7 10.8 7.0

Herb cover (%) 41.3 41.9 20.6

Bryophyte cover (%) 10.6 2.4 5.9

Lichen cover (%) 2.1 0.0 0.1

Forage cover (%) 45.7 45.5 25.5

N-fixer cover (%) 5.3 3.2 2.7

EMR fungi hosts (index) 5.2 5.0 3.6

Rose (%) 2.4 2.1 1.4

Spirea (%) 2.2 2.7 2.3

Pinegrass (%) 16.0 18.8 10.0

Rattlesnake plantain (%) 0.2 0.1 0.0

Pleurozium (%) 4.6 0.8 0.5

Peltigera (%) 0.6 0.1 0.2

Species richness (species/16 m2) 33.3 26.4 28.1

Note: green = best option(s), yellow = somewhat worse, orange = poor, red = serious concern.

either no effect of edge distance (e.g.,Peltigera), or no effect of the openingat all (e.g., rose).Vegetation – summary: Vegetation thattolerates open conditions did equallywell in any opening size, but speciesassociated with canopy cover rapidlydeclined as openings increased beyond200 m2. Small gaps, therefore, main-tained a greater diversity of plantgroups, with fewer weeds than largeopenings. The results suggest that smallopenings caused by variable partialcutting in these stands can be used toensure regeneration success while min-imizing adverse effects on vegetation.

Most plant or lichen species orgroups of species were reduced byburning and screefing. Shrubs andherbs, including ungulate forage,recovered quickly in burns, but moreslowly in screefs, while bryophytes andlichens had not recovered in eithertype of disturbed site after years.

Wildlife

Wildlife studies examined effects of theharvest treatments and edges of open-ings on a range of species to representthe wide diversity of animal species—from terrestrial invertebrates and smallmammals and songbirds, to larger carni-vores and ungulates.

Habitat features: Habitat features usedby many wildlife species (e.g., largelive trees, snags) were reduced in mostharvest treatments, particularly thosewith % removal (Table ). However,changes were often minor comparedwith existing variation in these ele-ments in IDF stands. Snags werereduced in the % removal treat-ments, because almost all snags inthese treatments were felled to meetsafety regulations. Coarse woodydebris () volumes were substan-tially increased by logging slash in thetreatments with % patch cuts, whilethe % uniform treatments caused a

Edge effects on pinegrass (screefed and undisturbed sites) and three func-tional groups. Cover of old forest–associated species has been multiplied by10 for visibility.

Harvest treatment effects on wildlife habitat elements and animals. All values arepercentages of the highest abundance of the variable.

Variable Uncut 20% ITS 20% patch ITS+res 50%ITS 50% patch

Canopy cover 83 100 60 47 75 67

Moss cover 80 100 71 33 60 46

Shrub cover 100 31 100 54 59 68

Snags 100 67 53 64 44 23

Coarse woody debris 35 33 29 46 51 100

Mule deer (winter) 100 71 58 50 31 4

Moose (winter) 100 57 49 0 10 47

Snowshoe hare (winter) 100 6 4 0 4 44

Grouse (winter) 100 98 29 100 41 59

Hairy Woodpecker (winter) 67 21 30 100 56 33

Yellow-rumped Warbler 74 100 65 72 74 100

Dark-eyed Junco 72 59 85 100 98 91

Golden-crowned Kinglet 100 50 75 33 25 52

Red squirrel 100 70 70 64 54 54

Flying squirrel 100 52 40 35 26 23

Yellow-pine chipmunk 13 21 34 61 51 100

Deer mouse 21 21 34 15 24 100

Meadow vole 18 29 43 23 31 100

Masked shrew 93 83 71 82 100 84

Montane shrew 48 61 57 68 100 75

Spiders 40 81 98 93 100 95

Centipedes 50 65 81 92 82 100

Ants 69 89 99 100 76 90

True bugs 100 51 61 40 30 48

Rove beetles 100 88 85 63 78 63

False darkling-beetle 82 14 46 37 100 20

Douglas-fir bark beetle 55 75 42 75 59 100

Secondary bark beetles 61 84 71 39 47 100

Note: green = best option(s), yellow = somewhat worse, orange = poor, red = serious concern.

minor increase. In the long term,these treatments will probably havelower recruitment of new afterthe logging debris has decayed.Winter tracking: Winter use by ungul-ates declined in the % removalunits, and dropped substantially with% removal (Table ) (Huggard andKlenner a). These results corres-pond to increased snow depths in theharvested areas, reaching depths (e.g.,> cm) that likely impede move-ments (Huggard and Klenner a).These critical depths were reachedeven at the IDFxh study area inmoderate- and deep-snow winters.The narrow – m leave strips inthe % patch-cut treatments wereapparently not wide enough to main-tain deer use. Snowshoe hares areclosely associated with dense patchesof small trees, which were nearlyeliminated by the uniform partial cuts(Table ). Leave strips around patchcuts retained some of this habitat forthe hares. Winter occurrence of RuffedGrouse and Sharp-tailed Grouse wasassociated with patchy deciduous treesand denser areas of forest.Woodpeckers: Eight species of wood-peckers used the site. Radio-trackedwoodpeckers had home ranges extend-ing well beyond the study area, encom-passing a wide variety of forest types.Woodpeckers nested almost exclusivelyin aspens, generally near natural orharvested edges (Klenner and Huggard). Other cavity-nesters, such asRed-breasted Nuthatches, preferred tonest near the tops of broken coniferand aspen snags. Trees selected for for-aging in winter tended to be recentlydead snags of moderate to large diam-eters (> cm dbh). However, differ-ences in woodpecker use of treatmentsin winter did not correspond closely toobserved changes in snag abundance,because of the highly patchy use of thesite by the birds.Songbirds: Several common songbirds,such as the Yellow-rumped Warbler,did not show pronounced effects of the

harvesting, likely due to the highlyvariable nature of the forest. Birds asso-ciated with open conditions, such asDark-eyed Juncos, showed only a mod-est increase in the more intensivelyharvested areas (Table ) (T. Dickinson,unpublished data). Species more asso-ciated with canopy cover and largertrees, such as Golden-crowned Kingletsand Western Tanagers, declined withharvesting intensity, but with high vari-ability (Table ).Squirrels: Density of red squirrelsdeclined in proportion to the percent-age removal of trees (Table ) (Herbers). In patch-cut areas, the squirrelsadjusted their territories to conform tothe leave strips, while in the uniformpartial cuts, they expanded territory sizeto incorporate roughly the same num-ber of trees. These territory changes didnot appear to affect survival of thesquirrels (Herbers ). Flying squir-rels declined more rapidly than redsquirrels, and northwestern chipmunksincreased to times their abundance inuncut forest in the patch cuts.Shrews: Masked and pygmy shrews atthe site showed no consistentresponse to treatments, while theabundances of montane and vagrantshrews increased in proportion topercentage removal in the harvesttreatments (Table ) (Huggard andKlenner 1998b). The abundance ofshrews increased along the northern

edge of openings in spring (Figure ),probably because earlier snowmeltencouraged plant growth and insectproduction in these locations.Salamanders: Long-toed salamanderswere too patchily distributed across thesite to assess treatment effects. Inponds, the effects of harvesting onreproductive success differed betweenthe IDFxh and IDFdk study areas (Fer-guson ). At lower elevations, pondsexposed by harvesting tended to dryout too early in the summer for suc-cessful production of young. At higherelevations, the extra heat in exposedponds appeared to promote growthand the production of larger young.Arthropods: The highly diverse arthro-pod community showed a variety ofresponses to the treatments. Groupsthat actively hunt on the ground, suchas spiders and centipedes, increasedwith increasing percentage removal,probably in response to greater forest-floor temperatures (Table ) (Huggard). Ants, which eat seeds and canreduce other components of insectdiversity, increased in the more openharvest treatments (Table ). Howev-er, the increase in ants was not pro-nounced, likely because favourablewarm, open conditions already occurthroughout dry IDF forests. Insectspecies caught in aerial traps, espe-cially bark beetles, were highly patchy,making comparisons of treatments

Edge responses of three small mammal species nests.

difficult (Table ) (Miller andMaclauchlan ).Wildlife – summary: Overall, treat-ments with % removal had less ofan effect on wildlife species than %removal. However, harvesting thesame amount of timber with %removal systems affects . times asmuch land as using a % system. Formost organisms, the observed reduc-tion in a % removal block was lessthan . times as much as in %removal treatments. Extensive lightpartial or patch cutting would there-fore have greater overall negativeimpacts on many organisms than lessextensive harvesting with greater per-centage removal. This summary, how-ever, could change as greaterpercentages of the harvestable landbase are affected over a rotation. Inaddition, light partial cutting requiresa more extensive system of activeroads and more frequent re-entryintervals, issues that were not evaluat-ed at the Opax site but may havedetrimental effects on wildlife.

Comparing patch-cut and individualtree selection systems at a given percent-age removal shows that each systemfavours roughly half the organismsstudied. A mix of practices at thelandscape level, combined with someunharvested areas or extended rotations,is recommended to maintain diversi-ty. Practices that help conserve criticalhabitat elements reduced by harvest-ing—such as dense patches, snags, oldtrees and aspen—could have the great-est positive effects for wildlife diversity.

Summary

This note outlines some of the studiesand the wide variety of responses tothe treatments and stand structurescreated by harvesting at Opax Moun-tain. The project is years old, so allresults reflect only initial post-harvestresponses. Results will change as treesregenerate and as succession, naturaldisturbances, and subsequent harvest

entries affect the forest. Conclusiveresults will not be obtained for severalgenerations. Managers should proceedwith caution. However, even thesepreliminary results demonstrate theobvious—but often neglected—lessonthat no single management approachwill maintain the full range of valuesthat are the professional responsibilityof forest managers. This point shouldbe made all the more strongly for thevariable IDF zone. In particular, thestandard silvicultural goal of main-taining an all-aged stem distributionwithin stands in the dry IDF zonecannot, by itself, meet all the manage-ment objectives for the zone.

Studies based on gap-size classesand the overall silvicultural systemstreatments help define harvest typesthat produce different responses for arange of variables. The most commonresult from Opax Mountain, for manyof the variables we examined, was thatopenings <. ha produce differentresults compared with openings >.

ha. Small openings (<. ha) are typi-cally created by individual tree orsmall-group selection systems appliedto the patchy natural IDF forest. Thelarger openings (>. ha) require cut-ting defined areas and should also beincluded as one of the managementtools for the IDF zone.

Studies of the natural disturbanceregime at Opax Mountain, includingboth fire and other agents, show avast range of variability in the size,severity, frequency, species-specificity,and effects on stand structure. Thiswork strongly reinforces the need touse a wide variety of managementtechniques in the dry IDF zone.Widespread application of any singlemanagement strategy, or one particu-lar stand structure goal, solely becauseit occurred under the natural distur-bance regime, is not supported by thework at Opax. An operational trial,the Isobel project adjacent to theOpax Mountain project, is extendingthe range of treatments being studied.

In addition to these general mes-sages, the work at Opax Mountainprovides more specific informationfor particular management topics:Regeneration: Harvested openings canbe successfully regenerated with anyof the three tree species examined,provided that planting occurs shortlyafter harvest and some screefing isused to remove competing vegetation.Lodgepole pine is likely to meet free-growing criteria faster than otherspecies, but should not be used exclu-sively because it does not meet allecological, economic, and forest-health objectives. Although plantedlodgepole pine is currently perform-ing well, we doubt its usefulness atlower elevations because the species isnot widely distributed in these standsnaturally. Advanced regeneration cansupplement restocking requirements,particularly at higher elevations, but itis very patchy. Harvesting operationscould target the release of such patch-es. Natural regeneration potential ismoderately high, particularly insmaller openings, if mineral soil isexposed, but survival is very low dur-ing hot dry summers.Vegetation: The range from opencanopy to moderately small openingscreated by partial cutting maintainsvegetation cover layers and accommo-dates many species, while also pro-ducing ungulate forage. Largeropenings are more productive forsome species, but also appear to pro-mote weedy species, particularly whenthey are near grassland areas withmany introduced plants. A few vascu-lar plants, along with bryophytes andsome lichens, are associated withdenser canopy cover, and decline inuniform partial cutting. Hence, patch-es of uncut forest are needed for thesegroups. Short or negligible edge effectssuggest that these uncut reserves neednot be very large.Wildlife: Uniform partial-cut harvest-ing is compatible with maintainingmany animal species. However, larger

openings also have associated species,including those that respond positive-ly to forest edges. Habitat featuresreduced by harvesting, such as densecanopy, large snags, and aspen,should be a management focus, with-in a diverse range of harvest systems.

Given the diversity of IDF ecosys-tems, it is difficult to know how broadlythe results from Opax Mountainapply. Although the abundance ofmany variables differed between theIDFdk and IDFxh study areas, overallresponses to harvest treatments, sitepreparation treatments, gap sizes, andedges were often similar. These resultssuggest some generality in the overallpatterns reported here. However, OpaxMountain has only one study area ineach of the variants. Confidence in thegenerality of the results—or knowledgeof how much they vary—will comeonly from work across the zone, but,given the few initiatives, much of thisknowledge will have to come fromother large-scale research as well asmonitoring IDF operational harvesting.Creating these opportunities to learn toimprove management is another funda-mental reason for encouraging morediverse practices in the IDF zone.

References

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Brand, N. and D. Lloyd. . Vegeta-tion response to clearcut edges inthe IDF at the Opax Mountain Sil-vicultural research site. B.C. Min.For., Kamloops Region, Kamloops,B.C. Unpublished report.

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Acknowledgements

We wish to thank our colleagues fromthe Opax Mountain research team forsharing their insight and data, whichmade this Extension Note possible. Inparticular we would like to acknowl-edge the contributions of CatherineBealle-Statland, Dan Bissonette, NicoleBrand, Rochelle Campbell, VanessaCraig, Tom Dickinson, Mona Doney,Dan Durrall, Christine Ferguson,Michelle Gillespie, Shannon Hagerman,Graeme Hope, Jim Herbers, JannaKaipainen, Dennis Lloyd, LorraineMaclauchlan, David Miège, Dan Miller,Alberto Orchansky, Cindy Prescott,Pasi Puttonen, Dan Smith, and RussWalton. We also wish to thank the restof the Opax Mountain research teamfor their support, and the many dedi-cated field assistants who contributedto the project over the last decade.Catherine Bealle-Statland, GraemeHope, Brent Olsen, Ken Soneff, andRuss Walton provided comments onan earlier version of this note. Fundingfor this project has been provided byForest Renewal BC, Forest InnovationInvestment, Forest InvestmentAccount (Forest Science Program),and the B.C. Forest Service.

CitationHuggard D.J., A. Arsenault, A. Vyse and W. Klenner. 2005. The Opax mountain silvicultural systems project: preliminary results for managing complex, dry InteriorDouglas-fir forests. B.C. Min. For., Res. Br., Victoria, B.C. Exten. Note 72. <http://www.for.gov.bc.ca/hfd/pubs/Docs/En/En72.htm>