Managing Invasive Plants: Concepts, Principles, and Practices link

U.S. Fish & Wildlife Service
America's National Wildlife Refuge System

MANAGING INVASIVE PLANTS: Concepts, Principles, and Practices

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Management Methods: Prescribed Burning

Photo of prescribed burn to control Phragmites at Prime Hook NWR, Delaware.
Prescribed burn to control the nonnative invasive grass Phragmites at Prime Hook NWR, Delaware.
Photo credit: USFWS

Introduction

Fire is a powerful, naturally occurring disturbance that influences a complex network of biological communities and ecological processes. The effect of fire on individual plants and plant communities is variable. In some cases fire may suppress invasive plant species, whereas in other cases fire may promote plant invasion and plant population expansion, which can change the patterns of fire over time and space.

Prescribed fires are intentionally set under controlled conditions to achieve specific management objectives. The use of prescribed fire is widely accepted as a primary tool for habitat restoration and management. The effectiveness of fire as an invasive plant management tool depends upon a wide range of variables and is specific to each situation and species. Prescribed fires are typically most beneficial when they mimic natural fire patterns in ecosystems that evolved with fire as a natural disturbance.

In this module, you will become familiar with

  • different roles of fire under natural and altered fire regimes, and in fire prescriptions
  • fundamentals of fire behavior and effects
  • principles and tactics for managing invasive plants with prescribed fire
  • examples of how prescribed fire can be integrated into invasive plant management

Natural Fire Regimes

Fire is one of many natural disturbances that has shaped landscapes for as long as vegetation has been present on earth (Agee 1993). Approximately 8 million lightning strikes occur globally each day, and lightning starts more than 6,000 fires in the United States each year (Pyne 1982).

The presence or absence of fire plays an important role in virtually all terrestrial ecosystems. The Nature Conservancy identified three broad ecosystem categories based on the natural occurrence of fire and vegetation response: fire-dependent, fire-sensitive, and fire-independent ecosystems (Hardesty et al. 2005).

Diagram describing FIRE DEPENDENT ecosystems where fire is essential, climatic conditions provide ample wetting and drying to promote growth of flammable vegetation for fuel, species posesses traits that respond positively to fire and may facilitate the fire’s spread. Examples include pine forests, shrublands, and grasslands. Diagram describing FIRE-SENSITIVE ecosystems, which have not evolved with fire as a significant recurring process. Species in these areas lack adaptations to respond to fire and mortality is often high. Examples include tropical and subtropical broadleaved forests. Diagram describing FIRE-INDEPENDENT ecosystems where fire may play little or no role in fire-independent ecosystems because conditions are too cold, too wet, or too dry to burn. Examples include deserts and tundra.
Diagram describing other ecosystems that lie in transition zones between fire-dependent, fire-independent, and fire-sensitive ecosystems and often exhibit a mixed response to fire.


Fire Regime Groups
Thumbnail of Fire Regime Groups map.
National, coarse-scale classification of five fire regime groups based on fire frequency and severity.

Climate variations around the globe influence the distribution of vegetation (natural fuels) and the conditions that favor different spatial and temporal patterns of fire, or fire regimes. Fire regime classifications can be simple to complex depending on their use for broadscale or in-depth assessments of the role and effects of fire. The US Fish and Wildlife Service (USFWS) uses the national, coarse-scale classification of five fire regime groups based on fire frequency and severity.

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Altered Fire Regimes

Fire Regime Condition Classes
Thumbnail of Fire Regime Condition Classes map.
Fire regime condition classes based on departure from the natural fire regime.

An altered fire regime is one that has been modified by human activities to the extent that the current fire patterns alter the viability and sustainability of desired ecosystems (Myers 2006).

Humans have manipulated fire since prehistoric times to create open hunting grounds, encourage growth of desired plant species, and protect human life and property. Human activities alter fire regimes directly through suppressing, preventing, and igniting fires, and indirectly by altering vegetation through livestock grazing, silviculture, and development.

Departure of fire patterns from their natural regimes can result in significant changes in biological communities and ecological processes and can elevate risk of catastrophic fire. The condition of the land is classified by land managers based on the degree by which current fire patterns differ from historical, natural fire patterns and the relative risk of losing key ecosystem components during a fire.

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Prescribed Fire

Photo of USFWS personnel igniting a prescribed fire with a drip torch.
US Fish and Wildlife Service has used prescribed fire for decades to control hazardous fuels on its lands. Photo credit: USFWS

Land managers now recognize the ecological importance of fire, which has become an important tool for many land management organizations and agencies. The USFWS is a leader in the safe, cost-effective use of prescribed fire. Since the 1930s, the USFWS has regularly used fire to enhance and maintain wildlife habitat in fire-adapted ecosystems, reduce hazardous fuels, and protect property and natural resources.

Prescribed fires are intentionally set and allowed to burn under a controlled set of conditions that define a fire prescription. Prescriptions are developed by experienced fire managers and ecologists who work together to create predictable fire characteristics that produce desired results.

A burn prescription for a particular area is outlined in a prescribed fire plan. The plan details

  • resource objectives
  • ignition methods
  • weather parameters
  • smoke management procedures
  • public notification
  • specialized protective equipment
  • firefighting resources
  • plants, animals, and physical characteristics of the site

Fire can be prescribed to control some invasive plant species and promote more desirable vegetation. However, fires create conditions such as open soil surfaces and increased nutrient availability that may enhance existing invasive plant populations and promote colonization by other unwanted species. Invasive plant populations may also influence fire behavior. Therefore, addressing invasive plants is an important element of fire planning, even when fires are prescribed to achieve objectives other than invasive plant management.

Fire Planning and Invasive Plants

Addressing invasive plants in fire planning begins with the Habitat Management Plan (HMP). The HMP should acknowledge concerns with invasive plant issues on the unit whether it's an invasive plant already present that might be enhanced by fire or an invasive plant outside the unit that might opportunistically colonize after a fire. The Fire Management Officer (FMO) should consult with the refuge biologist, the HMP, and local or regional experts to include a list of invasive plants, their locations, and how they may affect fire operations or the natural recovery of burned areas. The FMO then steps-down the HMP to specific fire management actions through the Fire Management Plan, to the prescribed burn plan, emergency stabilization plan, or other fire related plans. This information is then used after a fire to develop specific monitoring criteria to ensure compliance with the HMP.