The cool-season perennial Texas wintergrass Stipa leucotricha, is an important forage grass for domestic livestock and wildlife in Texas (southern USA). This study aimed to assess the effect of season of burning on Texas wintergrass and associated herbaceous species in two study sites: a 6.5 ha area of oak Quercus savannah in McCulloch County, and 7.5 ha of a mesquite Prosopis glandulosa - grassland community in Coleman County.
Experiments were randomized complete block designs. In the savannah, two experiments were undertaken.
Experiment 1 - treatments (burn; clip and remove vegetation and litter; and control) were applied to (3 x 3 m) subplots (4 replicates of each) in autumn (28 September 1979), winter (24 January1980) or spring (19 March 1980). Plant density and numbers of reproductive grass culms per plant were assessed on 3 June 1980 and 4 June 1981 in two (0.25 m²) quadrats per plot, and species frequency (by foliar hits using a point frame).
Experiment 2 - 10, 0.3 ha plots were established on two soil types. On each, two plots were burned (27 September 1979, or 24 January, 19 March or 21 November 1980) and two left unburned. Standing crop was recorded in 15 to 25 (0.25 m²) quadrats per plot (3 June 1980; 2 June and 23 October 1981) by clipping living herbaceous vegetation (to 2.5 cm stubble height), drying and weighing. Frequency was determined (as above).
In the mesquite grassland, eight 0.8 ha plots were arranged in two blocks. Two plots were unburned and two were burned (9 October 1979, or 25 January or 21 March 1980). Frequency was determined on each plot on 12 June and 10 October 1980, and 22 May and 6 November 1981. Plant density was measured in four (0.25 m²) quadrats per plot, and standing crop was determined.
In the savannah, burning or clipping Texas wintergrass did not affect the number of reproductive culms. Burning (any season) reduced standing crop for one year. Burning/clipping reduced wintergrass frequency for one year when conducted in January (control 74% vs. 52%), or March (control 68% vs. 44%) when large amounts of live grass was removed compared with autumn treatments.
In the mesquite grassland, burns tended to increase Texas wintergrass density, frequency and standing crop (perhaps due to reduced competition from abundant annual cool-season grasses). However, annual grass populations consistently tended to be higher in the second year after burning than on unburned plots. Increases in wintergrass were greater following autumn than spring burns.
If management aims to increase Texas wintergrass whilst reducing warm-season perennial grasses, burns should be undertaken in autumn (before Texas wintergrass growth begins and during warm-season grass growth). If the opposite is desired, burns should be conducted in winter/spring before warm-season perennial grass growth.
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