Lectures Flashcards
Whats Population?
All the individuals of a species that constitute a specific group or occur in a specific habitat.
What are species?
Related organisms capable of interbreeding.
What is Community?
Assemblage of different species that occur together in a habitat.
What is Habitat?
The place or environment where a species lives. Exhibits all the necessary requirements to fulfill its life cycle. Some species use different habitats for different parts of their life cycles.
Describe what is meant by niche?
Defined as the “specific ecological role” of a species in an ecosystem.
Fundamental vs. realized
What is meant by realized niche?
The net result of competition with other species.
explain Symbiosis.
what are the 3 possibilities of these relationships?
A close and continual interraction between two species that benefits one or both of them.
Can be one of these 3
- Commensalism: benefits one, no harm or benefit to the other
- Mutualism: both benefit
- Parasitism - one is harmed or experiences detrimental effects.
Define tolerance
The ability to withstand adverse environmental conditions.
What are some factors that influence populations?
Survivorship (demographics) Growth (exponential or logistic) Equilibrium, (carrying capacity) Reproduction (R vs K) Distribution (uniform or clumped) Density (competition, disease, predation) Cycles (species env. interactions.)
What does release refer to?
Rapid expansion of a species when conditions change favourably. (removal of competition/ opening of the canopy)
What is displacement?
Decrease of a species when an unfavourable condition is introduced. (ex. introduced predators or invasive species)
What is a keystone species?
Central to the overall function of the environment
What are the 3 types of survivorship? give examples.
Type 1 curve - high late mortality (Humans)
Type 2 curve - equal chance of mortality (mice)
Type 3 curve - high early mortality (Trees, Some animals like Sea Turtles)
What are demographics?
Age distribution
Explain r and K reproductive strategies
r refers to rate. Strategy is to create a large number of inexpensive offspring to increase the chances of survival. This happens in unstable environments where population density is not an issue because it never reaches full size. Exhibits type 3 survivorship
K refers to carrying cap. Strategy is to create Few expensive offspring and it is common in stable environments where populations reach carrying capacity. Exhibits a type 1 survivorship pattern where units have a long life expectancy and mature and die later in life.
What is Succession?
A sequence of changes in plant/animal communities that occupy an area over a period of time.
-Can also be seen as the process of change by which biotic communities replace eachother, with alterations to the physical environment.
What is primary succession?
Starting from scratch (No biotic components to start from)
Usually after a catastrophic disturbance
ex. Post glacial soils, sometimes the upper part of landslides, sand dunes.
What is secondary succession?
When there is a disturbance that does not completely wipe out the ecosystem.
ex. Logging, windthrow, fires etc
-Biotic material left behind to provide a base population for other species to establish from.
What is ecological succession?
The interaction of biotic and abiotic components of ecosystems, resulting in changes to both.
What is a SERE?
Entire sequence of biotic communities that occupy a site and replace each other over time, following disturbance of original community.
What are seral stages?
Specific stages of a sere with regards to the species present during that time.
What are autogenic and allogenic disturbances?
Autogenic - biotic
- Colonization
- Competition
Allogenic - abiotic
- fire
- flood
- landslides
- volcanic eruption
What things affect the rate of change in succession?
- The degree of environmental change that must occur before one community can replace another
- The productivity of organisms
- The longevity of organisms (Typically early lived species in earlier seral stages.)
- Resistance to invasion by other species occupying site
Briefly define a “Climax” forest
Relatively stable over time and self regenerating.
What does Xerosere refer to?
list a couple common features…
Very dry sites
- rock surfaces exposed by landslides or fire
- little or no water holding capacity
- no capital of nutrients
- Lichens often first species to establish
- Take a long time to develop
What does mesosere refer to?
Mesic sites
- loamy
- moderately fertile
- mid slope
- first colonized by herbs unless low in N
- eventually conifers will establish themselves.
What does Hydrosere refer to?
Wetlands
- start in wetlands
- invaded by phytoplankton and bottom rooted plants
- followed by sedge, rushes mosses and shrubs such as labrador tea.
- Common trees are Pl and Yc.
What is a stand?
An area of forest, relatively homogenous with respect to key variables like age/volume/key species
What is a forest landscape?
A mosaic of forest stands and non-forest ecosystems
Why is natural disturbance important to silviculture?
- It is inevitable
- It is used as a model for ecosystem based management. We can better understand how natural succession takes place so that we can minimize negative effects of harvesting.
What are biological legacies?
Can be organisms, organic matter, snags that remain after a disturbance and create a foothold for other species to establish.
What does multiple cohorts refer to?
Refers to disturbances that create diverse stand situations where many different ages are present due to many low severity disturbances. The trees are the “cohorts”
What does single cohort refer to?
Refers to one catastrophic disturbance that results in an even aged homogenous stand due to even age. The even age trees are the “cohorts”
What is horizontal differentiation?
Gaps in crown that open up over time. Refers to diversification of density.
What is vertical diversification?
The difference in vertical growth of trees in the same area, like overstory and understory.
What is GPP?
What shape pf curve would correlate with it?
Gross Primary Production (biomass)
Sigmoid curve
What shape of curve would CWD and understory diversity follow?
A U shaped curve due to less diversity during the stem exclusion phase
What is NPP?
What shape curve would it follow?
Net Primary Production
Bell shaped curve due to the net effect of mortality
Why does BC have such old growth on the west coast?
Absence of disturbances like fire have allowed our forests to develop for much longer than most others.
What are some characteristics of old growth?
- Infrequent Fire
- Wind Disturbance
- Gap Dynamics
What are some main attributes of old forests
Tree scale attributes -habitat Stand scale attributes -multiple aged forest Landscape scale attributes -Very diverse stand conditions
List some structural attributes of OG
- Wide range of tree sizes (reverse J) diameter distribution
- Large trees for species and site
- Large snags of various decay
- Richness and productivity of understory plant communities
- Multiple Canopy Layers
- Canopy Gaps
How are canopy gaps measured?
2 measurements
- from canopy to canopy
- from wood to wood
What are Edaphic openings?
Openings in forest due to natural features like streams rivers rock outcrops wetlands etc. NOT MAN MADE
