kb/data/en.wikipedia.org/wiki/Fire_ecology-5.md

title	chunk	source	category	tags	date_saved	instance
Fire ecology	6/7	https://en.wikipedia.org/wiki/Fire_ecology	reference	science, encyclopedia	2026-05-05T07:18:10.171501+00:00	kb-cron

Restoration ecology is the name given to an attempt to reverse or mitigate some of the changes that humans have caused to an ecosystem. Controlled burning is one tool that is currently receiving considerable attention as a means of restoration and management. Applying fire to an ecosystem may create habitats for species that have been negatively impacted by fire suppression, or fire may be used as a way of controlling invasive species without resorting to herbicides or pesticides. However, there is debate as to what land managers should aim to restore their ecosystems to, especially as to whether it be pre-human or pre-European conditions. Native American use of fire, along with natural fire, historically maintained the diversity of the savannas of North America.

=== U.S. Oak Savannas and Oak Woodlands === Oak savannas and oak woodlands historically expanded across the Midwest, creating a transitional zone between the eastern deciduous forested United States and the Great Plains tall grass prairie region. However, due to human impact, these ecosystems are now some of the most degraded ecosystems in the world. Roughly around <1% of original savanna habitats remain in the United States, making conservation and preservation of these habitats extremely important. Management of these scarce ecosystems will assist in conserving native communities and biodiversity by providing habitat for wildlife and plant species.
Habitats are characterized by the domination of oak species, lack a woody midstory, and possess a diverse ground coverage community of grasses, forbs, and sedges. Fire plays an important role in keeping these ecosystem types healthy. The topography of the Midwest consists of rolling hills and open plains. Fire historically would have run through these landscapes, creating a mosaic of prairie, savanna, and woodland habitat types due to the varying intensity and frequency of fire across varying landscapes. Woodlands would have been more prominent in hillier regions, while oak savannas would have been the transition out of the hill country and into the Great Plains region.
The overstory canopy of oak species is key in defining these habitats. Oak savannas have a canopy that is around 10-30% coverage, while oak woodlands have a canopy that can reach up to 80% coverage. This is calculated by using a densitometer, which is a handheld device that measures the ratio of tree coverage compared to open sky. Due to the increase in fire suppression, the lack of large grazers, and agricultural landscape conversion, these communities have been transformed into degraded habitats that have a dense canopy cover, a lack of ground diversity, and an increase in invasive species. One goal in restoring these ecosystems is to open the canopy through the removal of midstory species and possible canopy cover species. After the reduction of tree density and canopy cover, prescribed fire is used to hinder woody encroachment, create a desirable place of development for seed germination, and remove excessive ground litter. Fire regime plays an important role in the restoration of oak savannas and oak woodlands and depends greatly on the desired outcomes from management. Desired outcomes can consist of the reduction of canopy cover, midstory, or small woodies, promoting and protecting oak sapling growth, or favoring forbs over grasses or vice versa. Choosing when to burn, how intensely to burn, and how often to burn are major questions when managing these ecosystems. In addition to prescribed fire, using herbicides, grazers, and browsers can increase biodiversity and resiliency. Herbicides can be used to control invasive species and to prevent regrowth from harvested trees. Choosing an herbicide that has low persistence and mobility in the soil will help prevent the effects on nearby organisms and pollution of groundwater, minimizing the risk of environmental contamination. In addition, grazers such as bison and browsers such as white-tailed deer can contribute to increasing the heterogeneity of these ecosystems, meaning that the landscape has more varied physical features. Using the combination of these practices is key in management of oak savannas and oak woodlands.

=== Great Plains shortgrass prairie ===

A combination of heavy livestock grazing and fire-suppression has drastically altered the structure, composition, and diversity of the shortgrass prairie ecosystem on the Great Plains, allowing woody species to dominate many areas and promoting fire-intolerant invasive species. In semi-arid ecosystems where the decomposition of woody material is slow, fire is crucial for returning nutrients to the soil and allowing the grasslands to maintain their high productivity. Although fire can occur during the growing or the dormant seasons, managed fire during the dormant season is most effective at increasing the grass and forb cover, biodiversity and plant nutrient uptake in shortgrass prairies. Managers must also take into account, however, how invasive and non-native species respond to fire if they want to restore the integrity of a native ecosystem. For example, fire can only control the invasive spotted knapweed (Centaurea maculosa) on the Michigan tallgrass prairie in the summer, because this is the time in the knapweed's life cycle that is most important to its reproductive growth.

=== Mixed conifer forests in the US Sierra Nevada === Mixed conifer forests in the United States Sierra Nevada used to have fire return intervals that ranged from 5 years up to 300 years, depending on the locale. Lower elevations tended to have more frequent fire return intervals, whilst higher and wetter sites saw longer intervals between fires. Native Americans tended to set fires during fall and winter, and land at higher elevations was generally occupied by Native Americans only during the summer.