FRST 211 Final

common trees in CDF

common trees in CDF

coastal Douglas fir

W redcedar

red alder

grand fir

arbutus

Garry oak

Coastal BEC zones

CDF, MH, CWH

CDF

northern limit of range, strong rainshadow effect, Van Island and Gulf Islands

growing season water deficit

CWH

low-mid elevation along coast, windward side of coastal mountains

growing season water deficit

MH

subalpine elevations along coast, transitional to non-forested alpine

no water deficit

common trees in CWH

W hemlock, W redcedar, coastal Doug fir

amabilis fir, yellow cedar

sitka spruce, black cottonwood

red alder

common trees in MH

mountain hemlock, amabilis fir, yellow cedar

Garry oak ecosystem

naturally occurring Garry oaks and associated ecological processes

where are Garry oak ecosystems found

shady woodlands to open meadows with scattered trees and diverse understories

co-occurs with arbutus and Doug fir

Garry oak associated ecosystems

rock outcrops and coastal bluffs

maritime meadows and treeless grasslands

seasonal wetlands and small pools

cultural significance of Garry oak ecosystems

traditional land of Esquimalt and Songhee people

used fire to maintain open conditions and promote growth of food crops

historical changes of Garry oak ecosystems

increased: forest cover, fire intolerance, tree density

decreased: surface fire

recovery strategies of Garry oak

conservation of protected areas, habitat restoration, invasives removal, reintroduction of native species

traditional understanding of W redcedar regeneration

needed catastrophic disturbance to regenerate

4 assumptions of the traditional hypothesis for W redcedar regernation

1. tree size indicates age

2. populations establish as even-aged, post disturbance cohorts

3. abundant coarse woody debris represents recent mortality

   1. regeneration is insufficient to maintain canopy dominance

alternate hypotheses for W redcedar regeneration

1. WRC regenerates in fine scale canopy gaps

   1. WRC regenerates continuous, independent of disturbances

evidence against each of the 4 assumptions (WRC regen)

1. size is a poor indicator for age in shade tolerant species

2. WRC populations are uneven aged, the trees likely established beneath an existing canopy not a large opening

3. coarsewood doesn’t represent recent mortality, snags and logs of WRC are decay resistant

4. gap forming disturbances result in substrate suitable for successful seedling establishment

contemporary understanding of WRC population dynamics

it’s a combination of gap-phase establishment and continuous mode of recruitment from subcanopy to canopy

why is Yellow Cedar declining

fine roots grow in shallow soils to access nutrients

needs to snowpack to stay insulated

increasing temps (because of climate change) are causing early snowpack melt which gets rid of any insulation

roots are exposed to extreme cold temperatures → tree mortality, moisture stress, canopy loss

yellow cedar paradox

yellow cedar is injured by extreme cold weather during warmer climate then die of drought in a rainforest

BEC zones in mountain forests

IMA, ESSF, MS, ICH, PP/IDF

ICH BEC zone

low-mid elev on windward slopes

wetter local climates

MS BEC zone

mid elev on leeside

drier

ESSF BEC zone

high elev in the Souther 3/4 of BC

IMA/Alpine BEC zone

high elev throughout BC

climate of mountain forest BEC zones

interior & continental → cold winters and warm summers

orographic effects → windward is wet and leeward has rainshadow

snow → persistent snow → short growing season

IDF vegetation

transitional = low elev woodlands and high elev closed canopy forests

common trees = Doug fir, lodgepole pine

ICH vegetation

highest diversity of tree species in BC

drier sites = doug fir, W white pine, W larch, whitebark pine

wetter sites = W redcedar, W hemlock, subalpine fir, Engelmann x white spruce

MS vegetation

transitional, similar to ESSF and IDF

old forests with fire scars

extensive, young lodgepole pine stands

ESSF vegetation

common trees = ponderosa pine, subalpine fir, Engelmann spruce, W larch, Doug fir

IMA vegetation

treeless

non forested vegetation = dwarf shrubs, moss, liverworts, lichens, herbs, grasses

Natural Disturbance Types for mountain forest BEC zones

IMA = very rare fires, NDT 5

ESSF & ICH = rare stand initiating fires, NDT 1

= infrequent stand initiating fires, NDT 2

MS = frequent stand initiating fires, NDT3

BG, PP, IDF = frequent stand maintaining fires, NDT 4

limitations of NDT

underestimate biotic disturbances and disturbance interactions (fire x insects)

doesn’t take into account the complexity and importance of mix-severity fire regimes

three components of a silvicultural system

1. pre harvest

2. regeneration cutting method

   1. post regeneration treatments

types of silvicultural methods

clearcut

seed tree

shelterwood

selection (single tree and group)

patch cut

clearcut system

harvest an entire stand in a single harvest

area >1ha and >2 tree heights in width

50% open area climate

regeneration = even aged stand, shade intolerant or exposure tolerant species, species that grow on a range of substrates

seed tree system

selected trees/groups left during harvest

criteria for leave trees:

• large dominant trees

• wind firm

• good seed source

regeneration = shade int or exposure tol

shelterwood system

removes recessive components of a stand (mature trees removed in a series of cuts)

original stand → prepatory cut → seed cut → removal cut

single tree selection system

removes 1+ tree of a range of sizes → small gaps

creates multi cohort stands

very shade tolerant trees

group selection system

cut trees in defined groups

favours shade tolerant species

shade intolerant species can regenerate in gaps

creates multi cohort stands

patch cut system

openings <1ha in size

creates small even-aged stands