The Study of Silvics__________________

References

Klinka, Worrall, Skoda and Varga. 2000. The distribution and synopsis of ecological and silvical characteristics of tree species of British Columbia’s forests. Order from Canadian Cartographics Ltd.

• Required text.

Burns and Honkala. 1990. Silvics of North America. Agriculture Handbook 654. Washington, DC: USDA, Forest Service.

• Supplementary reading, mainly for life history.

http://www.na.fs.fed.us/spfo/pubs/silvics%5Fmanual

Readings for today’s lecture

• Klinka et al. 2000. Pages 1-19.

• Burns and Honkala. Pages 1-11.

What is silvics?

Silvics: – Is the ecological study of forest trees– Includes life history and general characteristics of forest trees

and stands– Environmental factors– Population genetics– Basis for the practice of silviculture

Silviculture: – the science and art of cultivating forests based on knowledge of

silvics. – The theory and practice of controlling the establishment,

composition, growth and structure of forests.

Role of Silvics in Forestry

• Management and restoration of forests, and maintaining/promoting desired attributes:

– Tree species choice– Methods of regeneration– Methods of cultivation– Effects of regeneration and cultivation on productivity and quality

• This requires knowledge of– ecological characteristics of trees species– how environment affects behaviour and growth of trees.

Role of Silvics in Ecosystem Classification • Intimately integrated• Ecological study of forest trees encompasses

the conditions under which they grow ---climatic, topographic, edaphic and biotic (i.e., their ecological niche).

• With knowledge of silvics and ecosystems, basic interpretations about each ecosystem type (BEC) can be made:– Stand composition (tree species choice)– Silviculture system (regeneration cuttings)– Potential productivity– Hazards– Biodiversity

Tree species

Conifers (18)•Western hemlock (Hw)•Mountain hemlock (Hm)•Western redcedar (Cw)•Alaska yellow cedar (Yc)•Amabilis fir (Ba)•Grand fir (Bg)•Subalpine fir (Bl)•Douglas-fir (coast, interior) (Fdc, Fdi)•Sitka spruce (Ss)•Engelmann spruce (Se)•White spruce (interior spruce) (Sw, Si, Sxw)•Black spruce (Sb)•Western white pine (Pw)•Whitebark pine (Pa)•Lodgepole pine (Pl)•Jack pine (Pj)•Juniper•Western yew

Deciduous (10)•Red alder (Da)•Mountain alder•Sitka alder•Bigleaf maple•Pacific madrone•Garry oak•Bitter Cherry•Western Flowering Dogwood•Black cottonwood (Act)•Trembling aspen (At)•Balsam poplar (Ab)•Paper birch (Ep)

Main Silvics Topics

General description (nomenclature, distribution, identification characteristics, botanical features)

Ecological characteristics (habitats, associates, tolerances)

Life history (seed production, germination, form and size of mature trees)

• Genetic variationSilvicultural applications

Ecological characteristics

Geographic range (distribution in western North America)

Climatic amplitude (climate class, BEC zones)Orographic amplitudeEdaphics (SMR, SNR)Shade and exposure toleranceFrost and flood resistanceResistance and risk to damaging agentsSilvical characteristicsSpecial adaptations

Geographic range

Area Region

1. Western North America 1.1 Pacific

1.2 Mainly Pacific and less Cordilleran

1.3 Pacific and Cordilleran

1.4 Mainly Cordilleran and less Pacific

1.5 Mainly Cordilleran and marginally Central

1.7 Pacific, Cordilleran, and central

2. Eastern North America 2.1 Cordilleran and more northern Central

2.2 Cordilleran and more southern Central

2.3 Central and Atlantic, marginally Cordilleran

3. Northern American transcontinental

3.1 Complete (Atlantic to Pacific)

3.2 Incomplete (Atlantic to east of Pacific)

4. Asian and North American

5. Circumpolar 5.1 Transcontinental complete

5.2 Transcontinental incomplete

Climatic amplitude

• Indicates species climatic tolerances

• Characterized by climatic regions and climatic characteristics of BEC zones

Climatic regions used to describe climatic amplitude

Climatic region Characteristics

Arctic tundra

=High Arctic

MTWM<10oC; MMT<0oC 9-11 mo.

Alpine tundra MTWM<10oC; MMT<0oC 7-9 mo.

Subarctic Cold, snowy climate with MTWM>10oC; 2 mo. with MMT>0oC.

Montane boreal † Cold, snowy climate with MTWM>10oC; MTCM<-3oC; <4 mo. with MMT>10oC.

Subalpine boreal † Similar to montane boreal but higher snowfall, shorter growing season, and cooler daytime temp.

Temperate * † Cold, snowy boreal climate but > 4 mo. with MMT>10oC.

Semi-arid Evaporation>precipitation; no headwaters

Mesothermal * † Mild, rainy climate with MTCM<18oC and >-3oC

Tropical MTCM>18oC

* Cold (< 4 mo. MMT>10oC), cool (MTWM<22oC), warm (MTWM>22oC)† dry, wet (no distinct dry season)

Continentality strata

Stratum Characteristics

Hypermaritime Outer coast under dominant influence of Pacific Ocean

Maritime Coastal areas on windward side of Coast Mountains under prevailing influence of Pacific Ocean

Submaritime Coast-interior ecotone on leeward side of Coast Mountains under strong influence of Pacific Ocean

Subcontinental Coast-interior ecotone adjacent to Coast Mountains under weak influence of Pacific Ocean

Continental Interior areas east of Coast Mountains under prevailing influence of continental air masses. Winter-cold, summer-warm to hot climates.

HM

M SM SC

Example: Climatic amplitude of Amabilis fir

• Maritime subalpine boreal –(wet cool temperate) – wet cool-cold mesothermal

• Description includes (1) continentality stratum, (2) temperature or precipitation variations where they exist, (3) climate class

• Ordered left to right from coldest to warmest

Frequency of occurrence

• (infrequent): species is uncommon or rare, not throughout latitudinal class (north, central, and southern)

• frequent: species is common and generally present through class

• very frequent: species is abundant throughout class

Orographic amplitude(general relief in conjunction with climate)

Orographic class

Species distribution

Submontane At foot of mountains, on lowlands, and on plains and bottomlands

Montane On hills or mountain slopes between lowlands and subalpine boreal climates

Subalpine Middle and low latitudes at high elevations with subalpine boreal climates; also low elevations in subarctic

Alpine Middle and low latitudes in highest mountains with tundra climate; also low elevations in arctic

Species occurrences in biogeoclimatic zones

Biogeoclimatic Zone Abbrev. Climate

Alpine Tundra AT Alpine tundra

Mountain Hemlock MH Maritime subalpine boreal

Coastal Western Hemlock CWH Wet cool (cold) mesothermal

Coastal Douglas-fir CDF Dry cool mesothermal

Engelmann spruce-subalpine fir ESSF Cool continental subalpine boreal

Spruce-Willow-Birch SWB Cold continental subalpine boreal

Montane Spruce MS Mild continental subalpine boreal

Boreal White and Black Spruce BWBS Cold continental montane boreal

Sub-boreal Spruce SBS Mild continental montane boreal

Sub-boreal Pine - Spruce SBPS Cool continental montane boreal

Bunchgrass BG Cool semiarid

Ponderosa Pine PP Dry cool temperate

Interior Douglas-fir IDF Moist cool temperate

Interior Cedar-Hemlock ICH Wet cool temperate

Edaphic amplitude

Soil Moisture Regime

1. XD (extremely dry)

2. ED (excessively dry)

3. VD (very dry)

4. MD (moderately dry)

5. SD (slightly dry)

6. F (fresh)

7. M (moist)

8. VM (very moist)

9. W (wet)

10. VW (very wet)

• (infrequent), light green on edatopic grid• frequent, green• very frequent, dark green

Amabilis fir: SMR (slightly dry) – fresh – moist – very moist – (wet)SNR: very poor – poor – medium – rich – very rich

Soil Nutrient Regime

1. VP (very poor)

2. P (poor)

3. M (medium)

4. R (rich)

5. VR (very rich)

Soil m

i ne ral iza

ble N

Water deficitAET/PET<1.0

No water deficitDemand=supply

Water table present in growing season

Edatopic grid for the CWHdm subzone upland sites, fluctuating water table sites, and floodplains

Shade tolerance and exposure classes

Class Description

Shade tolerant

Moderately shade tolerant

Shade intolerant

Protection requiring Require short- or long-term protection from parent stand; very shade tolerant or moderately shade tolerant species

Exposure tolerant In some situations survive and grow successfully without protection, even more so in open areas; shade tolerant or moderately shade tolerant

Exposure requiring Require full exposure to light for survival and growth; shade intolerant

Variation in shade tolerance? Shade tolerance appears to increase as climate becomes warmer or cooler and the soil becomes drier.

Species tolerances

Tolerances Criteria

Frost Freezing resistance of dormant buds and twigs

Heat Resistance to heat injury

Drought Ability to endure or avoid drought (stomatal closure, deep roots)

Flooding Ability to endure fluctuating or permanent water table

Nutrient deficiency or excess

Based on growth responses to nutrient conditions and ecological amplitude along soil nutrient gradient

Damaging Agents

Damaging agent Criteria

Snow resistance or resilience

Depends on crown architecture and stem and branch wood structure.

Wind resistance Uprooting and bole breakage. Depends on roots, crowns, height, HDR, wood structure.

Fire resistance and risk Species resistance (e.g., bark thickness) and risk in climatic region

Insect and pathogen risk

Depends on host specificity, climate, longevity, genetics

Resistance classes:•Low (L): frequent damage•Intermediate (M): some damage•High (H): rare damage

Risk classes:•Low (L): infrequent or rare damage•Intermediate (M): damage may be frequent but not all stands affected•High (H): damage frequent

Successional role and tree species associates

•Successional role (primary, secondary, stand developmental stages)•Occurrence in naturally established stands•Occurrence in pure and mixed species stands•Area and extent of association with other tree species

Silvical characteristics

Characteristic ConsiderationsReproduction capacity

Minimum cone or fruit bearing age; seed crop frequency, crop size, seed soundness, potential for vegetative reproduction

Seed dissemination capacity

Speed of seed fall, seed weight, seed structure

Potential for natural regeneration in low light and in the open

Seed durability and longevity, seed germination and stratification requirements, germination requirements, seedbed suitability, shade tolerance

Potential for initial growth rate (<5 years)

Species and site

Response of advance regeneration to release

Time delay for increased growth, shade tolerance, the need for protection/exposure

Silvical characteristics

Characteristic ConsiderationsSelf-pruning capacity in dense stands

Species, site and stand density

Crown spatial requirements

Species differences in length, width, and weight of live-crown, as unaffected by stand density

Light conditions beneath mature closed canopy

Understory vegetation development

Potential productivity Site index trends geographically and orographically

Longevity Low < 100 years; Medium >100 but <300; high > 300 years