Lecture 7- Peatland Disturbances Flashcards
What is a disturbance?
Discrete event that alters ecosystem composition, structure, function or physical environment
What is a disturbance regime?
Temporal and spatial patterns of disturbances, characterized by frequency, extent and severity of disturbances
What is resistance?
Ability of an ecosystem to withstand a disturbance (stays in the cup even with disturbances)
What is resilience?
Ability of an ecosystem to recover structure and function after disturbances (hydrology could have been completely changed, loses resistance and turns into a different ecosystem)
What are some natural disturbances in peatlands?
-Fire (lightning strikes)
-Insect outbreaks and pathogens
-Weather
-Permafrost
What are some anthropogenic disturbances in peatlands?
-Fire (human ignited)
-Drainage
-Forestry
-Oil and gas development
What influences the fire severity of peatlands?
-Tree mortality
-Peat consumption
-Carbon release
What influences resistance and resilience of peatlands?
-Species composition (fuel type)
-Microtopography
-Sphagnum dominance
-Surface wetness
-Peat moisture
-Time since last disturbance
What are the three fire severities in increasing order?
1.Surface fires
2.Stand-replacing fires
3.Peat fires
What are surface fires?
-Lower severity and intensity
-Annual to decadal frequencies
-Promote microtopography and sphagnum development (sometimes can regenerate really well with sphagnum)
What are stand-replacing fires?
-Fundamental process in northern peatlands
-All or majority of forest canopy burns (burn so fast that it doesn’t burn the peat)
-Decadal to centennial frequency
What are peat fires?
-Highest severity and intensity
-Can burn for months underground (zombie fires)
-Burn 40cm to 1m below
-Most detrimental
-How high is the fire or how fast
What do roads do to peatlands?
Changes flow of ground water and surface to and from peatlands which leads to modification of species composition and cover especially in road ditches
Describe metal and mineral mining
-Removal of peat and soil to access resources
-Increases water table when peat and soil are removed
-Leach contaminants during and after extraction
-Contaminants can persist for centuries
Describe peat harvesting
-Vegetation removed, peatlands drained, dried, then peat is harvested
-Peat exported and sold for horticultural purposes
-Completely destroy environment when you do that
-100s to 1000s of years to restore accumulated peat
What is the most common trees harvested in peatlands?
-Tamarack
-Black spruce
What happens to the water table when the trees are cut down?
The water table rises
What are implications of forestry in peatlands?
-Low tree productivity
-Results in higher water table
-Modify hydrology in adjacent peatlands and wetlands
-Increased soil compaction minimized by harvesting when ground in frozen
-Can regenerate in 10-20 years
What are some direct and indirect disturbances of oil and gas development?
-Removal of vegetation
-Removal and compaction of soil
-Altered hydrology
-Contamination
-Emissions
-Reduced resistance and resilience
What is open surface mining?
-Bitumen is close enough to surface can remove all vegetation and soil to mine
-Removal of entire peatland ecosystem and function
What happens to the peatland in open surface mining?
Increases salinity, gets into soil, salt water kills the plants
What is in situ mining?
Force deep underground bitumen deposits to surface
What does in situ mining do to the peatlands?
-Fragmentation and loss of contiguous peatlands
-Simplify microtopography
-Soil and hydrological changes
-Removal of overstory trees
-Loss of bryophyte species with shifts to graminoids and shrubs
What is reclamation?
Process of making severely degraded land suitable for another use (plant whatever as long as it fills ecological niche)
