211 Quiz 2

4-stage model stage 1

Stand Initiation

Key processes:

o Stand initiating disturbance followed by colonization by early-successional / pioneer

species.

• Key structural attributes:

o Accumulation of biomass, beginning of vertical stratification (plants grow at different rates)

o May appear “brushy (overgrowing of small plants)

4-stage model stage 2

Stage name:

o Stem Exclusion

• Key processes:

o Density-dependent mortality (i.e., higher probability of mortality in areas that are more

“crowded”).

o Resource limitation leading to intense competition

• Key structural attributes:

o Very dense canopy, but trees have small crowns.

o Single-cohort canopy. (All trees originating at roughly the same time)

4-stage model stage 3

Stage name:

o Understory Re-Initiation

• Key processes:

o Differentiation of canopy structure.

o Density-independent mortality. (. Deaths related to small-scale disturbance, like insects or pathogens.)

o Small canopy gaps resulting in more light reaching forest floor.

o More herbs, shrubs, and seedlings.

o New cohort of shade-tolerant tree species establishes

• Key structural attributes:

o Trees in canopy have large crowns

Emergence of a new cohort of trees in the understory.

4-stage model stage 4

Stage name:

o Old-growth

• Key processes:

o Gaps form in canopy due to mortality of individual trees or small groups of trees. Deaths

due to senescence (old-age death, especially of early-successional or pioneer cohort),

small-scale disturbances (e.g., wind), and pathogens

o These gaps allow tree regeneration, or recruitment (into the canopy) of previously

suppressed trees in the understory.

• Key structural attributes:

o Multiple cohorts

o Large, dead standing trees (snags) and significant coarse woody debris.

o Some large live trees, but also diversity in tree sizes.

o High vertical and horizontal structural diversity. E.g., multiple layers in the canopy and

variation as you move through the forest.

What are some potential shortcomings of this 4-stage model? (For example: What is this model

missing or failing to account for? In what ways might this model be unrealistic?)

This model assumes disturbance is severe and primarily plays a role in stand imitation.

o Assumes stand-initiating disturbances create a “blank slate” for the new ecosystem,

with no remaining legacies of the pre-disturbance ecosystem.

o Focused very heavily on the early stages of stand development, even though this may be

a short part of the stand history in areas (like coastal BC) with very long-lived tree

species.

Name the stages in the 8-stage model of stand development?

1. Disturbance and legacy creation

2. Cohort establishment

3. Canopy closer

4. Biomass accumulation + competitive exclusion

5. Maturation

6. Vertical diversification

7. Horizontal diversification

8. Pioneer cohort loss.

What are some of the key differences between the 4-stage and 8-stage models of stand development?

The 8-stage model accounts for legacies left behind after the disturbance rather than assuming that the forest is starting from nothing like the 4-stage model does.

• More descriptive.

• 4-stage focuses on early development while 8-stage focuses on the whole lifespan.

general definition of old growth

• forest with very old trees where ecological processes can occur w/o human intervention (self sustaining)

• has big widely spaced trees

• canopy dominated by long-lived shade-tolerant species

• has a diverse range of tree ages (constant tree regeneration)

• wide range of tree sizes

structure of old growth

• vertical diversity (multilayered canopy)

• horizontal diversity (birds eye view, dif density and gaps)

• snags (non-living) standing dead trees (habitats)

• snags fall = course woody debris

small scale disturbances of old growth

• old growth structure is dominated by small scale disturbances

• wind

• small disease/pests

• senescence, death of old age

• this leads to gap dynamics (more light availible) which are filled by shade tolerant species

What makes Douglas-fir a somewhat unusual member of old-growth coastal temperate rainforests?

• douglas fir is a shade intolerant species but has a very long lifespan (500-1000) so it may live well into the old-growth stage.

• The established trees will continue to survive, but will not regenerate

8 stage model - stage 1

Disturbance and biological legacies

• some mature trees likely survive first major disturbance (legacies)

• legacies survive and begin repopulating

8 stage model - stage 2

Cohort establishment

• new cohort of trees estabish (hemlock and douglas fir are pioneer species in BC)

• strongly effected by legacies of previous stand (source of seeds)

8 stage model - stage 3

Canopy closure

• trees fill up spaces, full forest, no new trees can establish

• high density, high relative humidity (beneficial), protected from wind

8 stage model - stage 4

Biomass accumulation and competitive exclusion

• trees grow rapidly competing for resources, density dependant mortality

• may be some self thinning (entire plant dies) and pruning (shed lower branches)

8 stage model - stage 5

Maturation

• max height and canopy size

• canopy develops layers

• shade tolerant plants establish

8 stage model - stage 6

Vertical diversification

• start of old growth

• complex, multilayer canopy

• density independent and dependant mortality

8 stage model - stage 7

Horizontal diversification

• gap formation, large = more light, more regeneration

Pioneer Cohort Loss

• shade intolerant pioneer species absent from understory

stand

spacially continuous group of trees

unit of forest

stand structure

• physical distribution of trees and plants in stand

stand development

stand over time

cohort

• group of trees developing together after single disturbance

single - cohort

• stand development after single disturbance

• even aged

Multi - cohort

• trees arise after 2 or more disturbances

• un-even aged

Canadian Ecozones

• large ecological unit characterized by interacting abiotic and biotic factors

• each has unique geology, climate, vegetation, wildlife and human factors

• hierarchical (ecozones => ecoprovinces => ecoregions)

• used for reporting and planning

Determinants of ecozones

• Climate, Geology, and Soils

• Temperature

N-S gradient (day length and sun angle)

Location and continentality (coast vs inland)

• Precipitation

Pacific maritime air masses and prevailing westerlies (name winds from direction wind comes from)

air masses from arctic (cold and dry) and gulf of mexico (warm and humid) collide along polar front

Canadian shield

• lots of shallow bedrock which doesn’t break down into soils

• low soils and lots of wetlands (water cant penitrate soils)

Mountain ranges

• coastal (western canada)

• rockies (east of coastal mountains)

• Arctic (northern canada)

Boreal shield, Taiga shield, Hudson Planes

• boreal forest dominated by coniferous species (white and black spruce) (foundation is wetlands and bogs)

• Canadian Northern Shield, exposed rock and permafrost

• wetlands and bogs

• The south has deeper soil, and glaciers left more sediment

Arctic cordillera, Northern and Southern arctic

• non forested tundra

• high latitude , low solar evergy

• low ppt but humid

• permafrost prevents perculation into soil = abundant surface water

• little water avail to plants, sparse vedge

Atlantic maritime and Mixed Wood Plains

Acadian forest

• SE of cad shield

• densley populated, settler impacts (forest heavily mod)

• mixed forest

• cooler wetter regions (maritime) with thinner soils (cad shield)

Great lakes- st lawrence and Corolinian Forests

• SE of cad shield

• densely pop , settler impacts (forest heavily mod)

• dom by deciduous trees

• warmer deeper soils (more inland and glacier deposits)

Prairies, Boreal, Taiga Plains

• Grasslands and boreal forest

• in rainshadow of rockies

• glacial influence (topography, soils, wetlands and lakes)

• S-N gradient (Grasslands => parkland=>forest)

Pacific Maritime, Montane, Boreal, Taiga Cordillera

• Coastal, Montane, and Subalpine Forests

• western cordillera (all mountain ranges of western canada)

• temp gradient (S-N) (north is cooler with latitude)

• elevation gradient (cooler and moist higher)

• precipitation gradient (W-E) (higher ppt in west)

• Diverse topography

• big change of climate over short different

• diverse vegetation

• diversity effects human impacts (valley bottoms, farming)

Canadian national forest inventory

• established between 2000 and 2006

• ongoing monitoring of forests provides info on state (conditions) and sustainable management of canadian forests

• covers 12 forested ecozones (out of 15 total)

• network of permanent plots (remeasure same plots) every 10 years

• plots cover 1% of land mass

• ground plots, photoplots, remote sensing data plots

• provides dominant species, volume, tree ages, and land use

How mix of plots are used together?

Remote sensing surveys

• grid network of “photoplots” from satalite and aerial imagery

field surveys

• “ground plots” cover 8% of photoplots

• big enough to capture variation

We use a mix of both. We use ground plots to understand and reassure our photoplots. Remote sensing allows for field plots to be continuous from detailed field measurements

Why is an ongoing forest inventory important?

• early identification of insects and disease for forest protection

• monitoring of harvesting patterns, ensures sustainable logging

• long-term land-scaping planning, what to conserve vs harvest

• quantification of carbon sequestration, track carbon storage

Orographic effects (mountains and their positions)

• vegetation effected by climate

• high variation of climate and vegetation in mountaneous ares

• as elevation increases, temp decreases and vise versa

Environmental lapse rate

• non moving air

• decreases at 6.4 degrees Celsius/ 1000m

Names of sides of mountain when wind is present

wind hitting side = windward

opposite side = leeward

orographic uplift

• after wind hits windward side of the mountain, it gets pushed up by slope

adiabatic cooling

• as air is pushed up mountain by orographic uplift, it expands and cools

• less pressure

adiabatic warming

• as air desends on leeward side of mountain it compresses and warms

• highh atmospheric pressure and higher temp

relative humidity

• % of water air has from its water holding capacity (ie has 40% of total capacity filled with water so 40% RH)

• amount of water vapor present/amount of water vapour the air can hold

• as temperature decreases, the air can hold less water and relative humidity increases

• as air temp decreases more the air is fully saturated of water and cannot hold more = 100% relative humidity

• at 100% RH theres potential for ppt

absolute humidity

amount of water vapour in air

Dry adiabatic lapse rate

• if air has less than 100% RH

• the rate of warming/cooling is 10 degrees celcius/1000m

Moist Adiabatic Lapse rate

• as air mass cools, it can hold less water, reaches 100% RH

• as it condenses, heat evergy is released

• cools at 6 degrees celcius/1000m

elevation effects on climate

high elevation

• colder (low atmospheric pressure)

• wetter (orographic ppt)

Low elevation

• warmer (higher atmospheric pressure)

• dries (less than 100% RH)

how temp varies in BC

• varies with latitude (suns solar E) and longitude (ocean)

• varies with elevation (cooler higher, less pressure)

• blanket of clouds holds in heat overnight

Precipitation causes

• caused when water condenses in air when air is cooler below its dew point and falls due to gravity

4 types of ppt caused by uplift

1) orographic

2) convergent

3) convective

4) frontal

PPT - snow

• snowpack abundance and persistence

• effects water availibility => length of growing season

• max at high altitude and latitude

• higher in west, lower in east of BC

• pos loop: high albedo, high reflection, low absorption of solar E, cooler temp, ppt as snow, more snopack, high albedo

latitude effect on temp

• influences sun angle, day length, seasonality, temp gradient

longitude effects on temp

• continentality and cloud cover

• land vs water

• in BC W => E gradient (maritime to conitinential)

Topography effect on temp

• aspect- orientation relative to sun

• elevation , temp down with increase elevation

PPT- orographic uplift

• airmass from ocean is pushed up and over mountain from wind

• releases ppt on windward side and then air goes east into rainshadow

PPT- Winter: convergent uplift

• in low pressure system

• warm and cold air air masses converge at ground level , they rise and water vapour condenses

• westerlies carry these moist airmasses onshore

• high pressure blocks westerlies

PPT summer- convergent uplift

• weaker low pressure

• low pressure shifts north and BC is dominated by high pressure

• vancouver- summer dry

Convectional uplift

• continential climates in BC

• surface heats up from sun and warms air around it

• air rises leads to clouds and thunderstorms

• summer - wet

frontal systems

• “front” = zone of contact of 2 air masses of dif pressures

• effects all parts of BC

dew point

temp at which relative humidity = 100%

at cooler temps, gas water condenses to liquid = cloud or fog and ppt can result

At a broad level how do topography and climate differ between

Wisconsin and BC?

Wisconsin is generally flat (due in part to glaciation), whereas BC is highly mountainous.

• Consistent climate across Wisconsin with only a minor temperature and precipitation gradient.

• BC climate can be highly variable in both temperature regime and precipitation amount.

• Wisconsin has a highly continental climate, while BC has a maritime climate on the coast and a

more continental climate in the interior.

From what you already know about the BEC system. How is the Wisconsin Habitat Classification

System similar to the BEC system?

Both strongly rely on soil characteristics, especially soil moisture regime (SMR) and soil nutrients regime (SNR).

• Both use understory indicator plant species to infer soil moisture and nutrient levels

• Habitat types (forest ecosystem types) are based on regional climates and then variation in local conditions (especially related to soil)

From what you already know about the BEC system. How is the Wisconsin Habitat Classification

System different from the BEC system?

• Wisconsin’s system is much simpler because its of relativity homogenous climate.

• Wisconsin’s system doesn’t directly examine soil.

• Wisconsin’s system has greater focus on multiple successional pathways for a given habitat type

climographs

• graph which shows climate (temp and ppt) of area

BEC

Biogeoclimatic Ecosystem classification in BC used to classify forest ecosystems

Zonal classification

• hierarchical system for classifying climate in BC

biogeoclimate units

• (zone+subzone+{varient}+{phases}

• characterized by similar climates

• can recognize based on vege in field

what are the hierarchical levels based on

zone- vegetation

subzone- plant associations’varient- variations due to topography and soils

“zonal” sites

• average and representative

• vegetation is just based on climate (not soils or aspect etc)

• site series (01)

• minor variability due to topography (moderate slope, aspect and location)

• Specific site conditions within a BEC zone

• Used as the reference site to describe what the zone is like

coastal zones

• mod by pacific ocean

• rainshadow of mountains

• altitudinal gradient (elevation)

• orographic effects

southern interior

• rainshadow of coastal range

• low latitude in BC

• strong altitudinal gradient and orographic effects

northern interior

• rainshadow of coastal range

• hjigh latitude in BC

• strong alt gradient and 0rographic effects

• continentality

how to name zones

ZONEyz

• yz are subzone

• y= ppt regime

x=v dry, d=dry, m=most, w=wet, v = very wet

• z=temp regime(interior), Coastal zones(continentality

interior temp regime

h=hot, w= warm, m=mild, k=cool, c=cold, v= very cold

continentality of coastal zones

h=hypermarine, m=maritime, s=submaritime