23.3 - Fires As An Ecological Disturbance Over Geological Time

ecological disturbance

events that influence the makeup of an ecosystem

• adds or removes organisms

• alters level of available resources

factors that affect the impact of disturbances

• intensity

• geographic extent

• frequency - single fire can rejuvenate forests but repeated reduces recovery time

intermediate disturbance hypothesis

moderate levels of disturbance promote more diversity than high or low levels

high levels of disturbance effects

lowers diversity by exceeding tolerance and recovery times of species that grow/colonise slowly = faster growing fills gaps

low levels of disturbance

reduces diversity by allowing most competitive species to monopolise resources = prevent less dominant species from becoming established

fire triangle

3 factors - ignition, climate and vegetation, that determine the occurrence of fires at landscape scale

• climate determines condition of fuels -

fire productivity gradient

describes the relationship between fire frequency and biomass production across different ecosystems

• very arid with low productivity = infrequent fires

• highly wet and productive environments = low fires bc trouble igniting

• intermediate zone - medium productivity and dryness = perfect for fires

net effect of cultural burning 

• reduced landscape fuel loads

• reduced vertical connectivity of fuels

• protection of fire sensitive ecosystems

• connection to country and improved Indigenous livelihoods

• sign. less carbon released than wildfires