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Green Fireguards

By Mike Porter
Senior Wildlife and Fisheries Consultant

Posted Jul. 1, 1996

A green fireguard can be a useful alternative to a bare soil fireguard or other types of fireguards. A green fireguard is managed to promote green vegetation and to minimize mulch.

It is more fire resistant than a mowed fireguard consisting of only dormant plants. It is less prone to erosion and provides a firmer surface for transporting fire equipment than a bare soil fireguard. A bare soil fireguard tends to cause erosion in sloping uplands typical of this region. When wet, the muddiness of a bare soil fireguard can limit access around a burn area.

In this area, a green fireguard is used primarily with cool season burns. A green fireguard is created and maintained with timely mowing and sometimes planting. Proper mowing reduces burnable plant material, enhances germination success of cool season plants, and reduces competition from warm season plants. Planting provides a source of cool season plants where the seed bank is inadequate.

A green fireguard should be mowed at least twice during summer and once during fall. The vegetation should be mowed as short as possible each time. The most important times to mow the fireguard are mid to late June, late August, and mid to late fall soon after the first killing freeze. The first mowing each year should be postponed until after mid June to allow seed to mature on cool season plants. The June mowing removes spring growth.

The late August mowing removes most of the summer growth and prepares the site for germination of cool season plants. Fall mowing removes fall growth of warm season plants and provides the maximum amount of time for mulch decomposition and scattering before cool season burns. Of course, more frequent mowing during summer and fall will prepare an even better fireguard, but it often becomes impractical to allocate more resources to fireguard preparation.

Excessive amounts of mulch on a fireguard can be raked away with a hay rake. The mulch should be raked to the side away from the fire. Mulch piled up on the burn side will burn and smolder for a relatively long time. Smoldering mulch can blow across a fireguard and start an unwanted fire. Extinguishing smoldering mulch is difficult requiring lots of water and labor.

A green fireguard and a pasture road in the same path make a good combination. Traffic across the road minimizes plant growth and enhances mulch decomposition and scattering. Mowing for fireguard purposes helps identify and maintain a road. A wider fireguard is usually better than a narrower one. No single width is appropriate for all burning situations, but 12-24 feet of width works well for many range burning situations.

When existing cool season plants are inadequate, species such as ryegrass, rescue grass, oat, rye, wheat, white clover, and others can be planted. Many cool season species can work in a fireguard for a late winter or early spring burn. However, several species such as ryegrass, bromegrasses, and annual clovers generally do not produce adequate growth locally in a fireguard for a late fall or early winter burn.

Species such as rye, oat, or established white clover are probably better in a fireguard for a late fall or early winter burn. White clover is a perennial clover that can work in a green fireguard with moist fertile or shaded soil. It generally does not work well in droughty, upland, exposed soil in this area.

Even under ideal management, a green fireguard is rarely as effective as bare soil for stopping fire. Dormant mowed stubble in a green fireguard can allow a fire to burn across unless extinguished. Where fire can burn through a green fireguard, fire intensity is minimized due to the short vegetation allowing easy fire control and economizing water use. A bare soil fireguard is usually a better choice if terrain is level to gently sloping. Bare soil fireguards are created with a disc, plow, bulldozer, or grader.

Regardless of the fireguard used, planning and management should be enacted now for a prescribed burn that will be conducted during the coming fall, winter, or spring.

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