Fire is often used in the management of North American grasslands, e.g. to counter succession to scrubland. It is hypothesised that a hot, intense, fast-moving fire results in more damage to grasses compared to a less intense, slow-moving fire. This study determined the effects of a range of fireline intensities on subsequent yield, plant height and number of seed stalks for two perennial grasses, the native tobosagrass Hilaria mutica and non-native weeping lovegrass Eragrostis curvula (introduced from South Africa for erosion control), in Texas (southwest USA).
Weeping lovegrass plots were located in a relatively homogeneous stand 5 km north of Brownfield city. Tobosagrass plots were located 11 km southeast of the town of Gail.
From 2 February to 15 April 1982 and from 14 March to 28 April 1983, 61 plots (minimum plot size 20 x 20 m) were burned: 17 plots were burned as headfires and 10 as backfires in lovegrass; and 22 as headfires and 12 as backfires in tobosagrass. Burns were undertaken in a variety of weather conditions producing a range of fireline intensities.
Fireline intensity (kW/m) was measured on the 61 plots. Relative humidity, air temperature, wind speed, soil moisture, soil temperature, and fuel moisture and fire spread rate were measured at time of burning.
Grass response was recorded in each plot after one growing season, sampling within 10, 0.25 m² quadrats in lovegrass and 15, 0.0625 m² quadrats in tobosagrass plots. The tallest leaf was measured and number of seed stalks counted. As a measure of standing crop, grasses were clipped 1 cm above the soil surface and samples dried and weighed. Percentage change in basal area was measured on lovegrass plots burned in 1982.
Over the two study years a wide range of fireline intensities was achieved (in tobosagrass plots ranging from 85-8,036 kw/h; in lovegrass plots from 67-12,603 kw/h).
Grass growth responses were not correlated with fireline intensity or any of the environmental parameters measured (both species recovering well). Higher fireline intensities did not cause a detrimental impact on either grass species in comparison with lower intensity burns.
Thus if management aims to remove scrub by burning in areas where tobosagrass or willow lovegrass are present, spring burning (under ambient conditions) is unlikely to be damaging to these grass species.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: https://www.uair.arizona.edu/holdings/journal/issue?r=http://jrm.library.arizona.edu/Volume41/Number5/