Fire regime

A fire regime is the pattern, frequency, and intensity of the bushfires and wildfires that prevail in an area over long periods of time.

[2] If fires are too frequent, plants may be killed before they have matured, or before they have set sufficient seed to ensure population recovery.

[2] Fire regimes are characterized by a variety of factors including vegetation composition, fuel structure, climate and weather patterns, and topography.

[2] Other factors such as post-disturbance successional stages and types of previous management on the landscape may also be used to describe a fire regime's characteristics.

Fire regimes are also impacted by topography, slope exposure, landscape management, and ignition (which may be human or lightning-caused).

The United States has the Monitoring Trends in Burn Severity (MTBS) Project which uses satellite data to map fires from 1984 onward.

[1][13] Decreasing fire intervals negatively affect the ability of fire-killed species to recover to pre-disturbance levels, leading to longer recovery times.

The fire-climate interactions of a changing climate are predicted to reduce population recovery for plants solely dependent on seed production for re-population.

These changes will shorten fire intervals, which will reduce the time for plants to accumulate seeds and potentially allowing for selection of more flammable species.

A study in southeast Australia found that widespread losses of mountain ash following prolonged wildfire seasons have burned 87% of the species range.

Subsequent re-burns of immature mountain ash led to complete regeneration failure and conversion of forest cover to shrubs and grasslands.

[15] Bushfire is especially important in Australia, where much of the vegetation has evolved in the presence of regular fires caused by the Aboriginal practice of firestick farming.

[citation needed] The California chaparral and woodlands ecoregion, covering a large portion of the U.S. state, is dependent on periodic natural wildfires for optimal health and renewal.

[19] Another example of invasive species affecting fire regimes can be found with the spread of the Brazilian pepper tree (Schinus terebinthifolia) on native plant communities.

Populations exist in Australia, South Africa, the Mediterranean, southern Asia, and the southeastern United States.

Brazilian pepper is often found in disturbed soils and substrates and often outcompetes native plant communities creating monoculture-like conditions.

As Brazilian pepper moves into an area, it creates a sub-canopy layer that often outcompetes grasses and ground cover species.

A recent model found that a 4-year fire-return interval would eradicate an initial 100 pepper female population within 25 years.

Brazilian pepper may create a shaded humid understory and reduce fine fuel loads in areas of historically frequent fire, which therefore increases the fire-return interval thus negatively affecting the fire-adapted plant community.

Fire regime classification by ecosystem type. Fire severity and frequency is linked to vegetation type. [ 3 ]
LANDFIRE (Landscape Fire and Resource Management Planning Tools), is a collaborative program between the U.S. Department of Agriculture and Department of the Interior that provides geospatial data on fire regime characteristics such as vegetation, habitat, carbon sources/sinks, fire, etc. The data is used to help map fire events and look at broad scale fire regime effects.
NASA imagery showing the interrelatedness of climate and fire. Active fires are represented by red dots. [ 14 ]
Brazilian pepper trees are encroaching on native plant communities throughout the southeastern U.S. and causing changes to the frequency and severity of fire regimes and ecosystems. [ 20 ]