Transcript Impacts of disease and insect outbreaks on ecosystem processes

Impacts of disease and insect
outbreaks on ecosystem
processes
Roger, Bob, John, Skeeter, Glenn,
Brian…
State changes vs species
changes
• Can have a large changeover in species composition without a
change in function
• An example of a state change: going form N mining to N
accumulation
Will anything favour plants?
• There are many species associated with plants (parasites as well as
mutualists); many of these will be positively affected by temperature
changes
• Many of the impacts will be interactive or cumulative, not acting in
isolation
• Given water constaints, it is difficult to think of many ways in which
plants would benefit from the likely climate change…
What’s the extreme scenario?
• Loss of all the major tree species:
– Spruce (combination of spruce budworm + increased
temepratures)
– Birch (increased temperature, possibly leaf miner
expansion (already in Fairbanks))
– Alder (canker)
– Aspen (leaf miner)
• Potential result: a grassland filled with invasive
plants, with occasional big black spruce…
Are there variables we could
monitor that would give us early
warning?
1) Monitor species currently causing outbreaks or
ones that might be here soon:alder canker,
birch leaf miner, bark beetle, spruce bud worm,
spruce bark beetle, root rots, tent caterpillar
2) Monitor more general variables on
plants:symptoms of root rot, obtain damage
types and pictures of leaves, measure needle
retention times (conifers) or leaf sizes
(deciduous) to give early warnings of stress
3) Monitor turnover of long-lived understory
plants (to get at birth and death rates and look
for shifts)
What turns an endemic parasite
into an outbreak species?
• Lots of examples from other systems
where this has happened
• How can we monitor this effectively?
• What constrains the current endemics?
Predation? Plant defenses? Competition?
Does it matter what kills a tree (a clear
threshold)?
Are the ecosystem consequences of death by
drought, fire, or herbivory / disease different?
• Proportion of needles still on tree may be different 
affects light level and future fire severity
• Drought likely results in lower turnover of nutrients and
carbon than death by herbivores (frass production)
• Proportion of downed trees may affect succession
• Reproduction prior to death may depend on mode of
death
• Harvest by humans: higher for intact logs
• Ability of decomposers to come in will be affected by
mode of death
• Fire mobilizes lots of P
• Other species may be affected by disease
Conceptual link between
disturbance and disease / insects
• Is an insect outbreak a low-level
disturbance?
– May have positive effects on mid-succesional
species that are released from competition for
light
Can we figure our ecosystem
impacts without waiting 100 years?
Ideas…
• Kill of spruce trees and see what happens
• Find a way to align disease gradients with
drought gradients…
• May have maximum temperatures (due to
solar maxima) in 2013-2015: get ready to
capture the impacts
Potential talks
• John Lundquist – landscape pathologist
• Glenn Juday: spruce budworm and climate
change
• Talk on how endemics become outbreak
species?