Burning in the Growing Season Effects on Grass

When land managers start a prescribed burning program they often wonder whether fire will kill their grass, particularly during the growing season. To answer this question, the history of grasslands/shrublands needs to be considered. Fire is common through much of North America as a natural disturbance and a land management tool. Native Americans used fire as a part of their everyday existence from cooking meals to preparing camp sites and even hunting and warfare. With so much fire being used, historically, landscapes burned throughout the year. However, the intentional use of growing-season fire as a management tool remains controversial due to potential damage to fire sensitive herbaceous plant species that may be of benefit to both livestock and wildlife. 

Growing-season grazing is a common practice that, if done at appropriate stocking rates, can benefit pastures as a whole. The common practice of growing-season grazing and growing-season fire were compared to see if there was a difference in plant growth and survival. For 10 years, plant communities burned in the dormant season and during the growing season and were monitored. The study found that the particular time of year that the fire occurred did not affect the plant community. The amount of rainfall was the dominant driving factor affecting grass production.

Figure 1. The relative abundance of little bluestem in pastures burned in the dormant season or the growing season. The solid line represents the rainfall received on the pastures the previous growing season.

Individual little bluestem plants were burned at multiple developmental stages to see how growing-season fire affected survival and growth. Plant age was the primary factor affecting plant survival with nearly all seedlings dying when burned. However, once plants reached 18 weeks old, survival was nearly 100%. Plant survival was similar for plants that were burned or clipped to simulate grazing suggesting that growing-season burning doesn’t have any greater effect on plants that grazing. One advantage that growing-season burning had was that both aboveground production and belowground biomass were both increased after burning, while growing-season clipping reduced production. 

Figure 2. Above-ground grass production on plants either burned and clipped or clipped alone.The letters represent groups that had similar production.

Figure 3. Below-ground  root production on plants either burned and clipped or clipped alone.The letters represent groups that had similar production.

Grasses in the Great Plains are well adapted to both grazing and burning during the growing season and can be included in a successful land management strategy.