Week 10 - Presentations Flashcards
What type of flood discharge regime characterizes the Fraser River?
Nival
List three (3) species our guest speakers consider to be “invasive” to the Fraser River Estuary and a threat to its ecosystem.
hybrid cattails - typha x glauca
purple loosestrife
Spartina
Reed canary grass
Canada Geese
Complete the following graph by drawing a line to depict the general relationship between (x) distance from river mouth, and (y) % native species. Describe the shape/direction of the line if you can’t draw it.
native species are the HIGHEST percentage at the estuary (100)
the line decreases (lower percentage of native species) the further you move inland.
diagonal line that goes from (x=0,y=100) to (x=25,y=0)
Explain the relation you depicted in the graph question in the context of the Fraser River estuary. What physical factor did Dan Stewart principally attribute this relationship to?
native species that are found in the estuary are SPECIALIZED but less competitive - they do not need to be as competitive when they live in a harsher environment. They are adapted to inundations/ elevation, tidal flux, salinity, nutrient availability, etc.
Invasive species are extremely competitive but not as specialized.
the farther you move away from the mouth of the river and the tidal flux and salt wedge the less specialized they have to be and have to be more competitive.
inundation (elevation) stress and salinity stress decrease further upriver
Dan Stewart’s MSc research examined the cryptic invasion of non-native cattail, Typha x. glauca, to the Fraser River estuary. What two (2) types of “treatment” did he apply to cattail plots at his study site on Frenchie’s Island, to test effects on cattail growth (i.e., what 2 factors did he manipulate)?
his treatments were cutting and litter presence/absence.
he did cutting experiments
- did not cut
- cut once a year
- cut twice a year
twice a year cuts depleted the rhizomes of the cattails and even prevented them from producing flowers/ seeds
fencing in which the cattail stalks were removed and therefore would not smother the native veg
Of the two factors Dan manipulated on Frenchie’s Island and you identified in Question 5, which was found to have the greater effect on densities of Typha x. glauca over time?
he found removing litter had the greatest effect
Eric Balke’s MSc research examined tidal marsh recession along Sturgeon Bank in the Fraser River estuary. What are the four (4) hypotheses he has considered in his research to explain the recession?
sediment deficiency - due to the jetty ‘training’ the river and increasing the velocity with amouring to send the sediment into the sea instead of allowing for natural deposition to occur - this reduces the elevation because sediments are not being replenished and there is more inundation to plants in the marsh
salinity increases - due to the jetty blocking the allowance of fresh water into the estuary
goose herbivory - considered invasive species due to increased numbers and lack of migrating or increased numbers during migration - eat all the veg
sea level rise
none of these are the single reason for the marsh recession, they are all likely contributors AND the knives edge theory suggests that the plants in high-stress environments are already at their tolerance threshold
What is meant by the expression “coastal squeeze”? Explain how the “living dike” concept may be an option to mitigate coastal squeeze.
Coastal squeeze is the loss of natural coastal habitats and/or the deterioration of their quality due to anthropogenic sources such as infrastructure which impedes the natural landward retreat processes
The living dike project (building a dike higher and gradually widening the dike through sediment and natural vegetation to create a salt marsh) would increase the resiliency of the habitat and prevent the coastal retreat - it will diminish the forces of wave and storm impacts and provide a greater amount of space for habitats with the salt marsh veg
