Topic 30 Flashcards
Conservation must integrate ecology with
social, political and economic systems
Natural disturbances
windstorm, ice storms, lighting fires, hurricanes, floods, insect outbreaks, grazing animals
Human disturbances
have more profound and long lasting impact on communities than natural disturbances
Human activities involve..
continuous management of communities
Completely remove natural communities and replace with…
- cultivated cropland
- pastures
- monoculture forests
- paved highways
Often natural disturbances are ..
enhanced by human activities
Lightning fires
important disturbance regime in forest communities in North America. require enough dry fuel for ignition
Fires natural occurs..
every 50-200 years
Some forest species have come to depend on forest fires
- jack pine
- fireweed
- moose feed on new growth
- burned plant material quickly enriches the soil
Fire suppression programs in Canada and US national parks:
- park managers attitude: fire is destructive
- fire suppression programs
- fire towers
- smoke jumpers
- firebreaks
- smokey the bear
Human enhanced fires
Yellowstone national park in USA. 1988 dry year with high fuels and winds. 36% of parks forest burned. accept importance of fire in long term dynamics
Park managers and fire management regime
- controlled burns: allows some natural fires to burn and reduce fuel
- prescribed burns: start small fires
Mountain pine beetle
native to North America feeding on pine trees
Spruce budworm
native to North America, but causes sever defoliation of millions of acres of spruce and fir. cyclical outbreaks every 35-40 yrs
Forest tent caterpillars
native, mostly managing to aspen. cyclical outbreaks of about 3 years every 10-12 yrs
Emerald ash borer
invasive pest from asia with documented spread through Canada since 2002. devastating to ash trees
Insect outbreaks are important ..
disturbance regime in forest communities in North America
Bark beetles
attack particular tree species by boring into bark. show up as needs turn red. dead trees provide nesting and roosting habitat for birds. wind fall cause dead trees blow over and creates gap in mature forests for secondary succession to begin
Forest managers attitude for insect outbreaks
grow tree as a crop rather than a forest. (clear cut, spray herbicides, plant seed one tree species, repeat)
Monocultures lead to..
massive insect outbreaks
Beetle forest in Northern BC
50% of BC central interior economy is driven by forest industry, aggressively logged infested areas to slow the beetle outbreak. 1972-2002 clearcutting results in largest clearcut in world (bowrun cut)
Monoculture
growing one species in an area
