Abstract. The study of vegetation dynamics in tallgrass prairie in response to fire has focused on dormant season fire in late successional prairies. Our objective was to determine if late season fire of varying frequency results in divergent successional patterns in an early successional tallgrass prairie disturbed by grazing and cultivation. Specifically, we evaluated the influence of late‐summer fires of varying frequency on community composition and species richness. We collected vegetation and environmental data on two sites burned in the late growing‐season at varying frequencies. These communities differed in composition depending primarily on edaphic factors, time since the last burn, and year‐to‐year variation. We interpret the time effect as related to changes in species composition accompanying plant succession that followed disturbance either from cropping and heavy grazing on the loamy site or heavy grazing on the shallow site. Other unidentified factors also have a role in vegetation dynamics on this prairie. Community composition and species richness were not consistently responsive to frequency of growing‐season fires.

Wildfire in the growing season is relatively frequent and interest is increasing in using growing-season fm in management of tallgrass prairie. However, the influence of fue in the growing season on forage production and species composition, especially in mid-successional tallgrass prairie, is largely unknown. Our objective was to compare vegetation composition and production on Loamy Prairie and Very Shallow ecological sites in mid-successional stages in response tu late growing-season fire at different frequencies. We applied 4 burning treatments (no burn, or 1, 2, or 3 burns iu 5 years) in the late growhtg season in southern Oklahoma during a series of years of above-average precipitation. The sites were dominated at the beginning of the study by early-and mid-successional species including prairie threeawn (Aristi oligantha (Michx)), a species indicating a disturbance history. After the initial burns in 1990, tallgrasses, little bluestem, and perennial grasses were reduced by burning on the Loamy site. Forbs were more productive on burned plots (1,9&t kg ha-') than on plots that were not burned (1,290 kg ha") averaged across sites. Total production was not reduced by burning in 1990. Growing-season burns in 2 consecutive years had little influence on species composition or production as compared to a single burn ht 2 years. Warm-season perennial grasses other than tallgrasses and little bluestem increased on the Loamy site, but decreased on the Shallow site. Production of cool-season perenuial grasses increased to almost 49% of total production on twiceburned plots averaged across sites. Other than the effect on coolseason perennial grasses, 2 burns over a two-year period bad little effect beyond the fmt growing season after the second bum. Twice-burned plots and plots burned 3 times produced more forbs than either plots that were burned once or not burned. Production of perennial grasses was opposite that of forb production. Total production was not reduced on either site regardless of fw frequency. Results indicate managers may expect a short-term reduction in production of forage grasses and an increase in forbs following late growing-season fire in mid-successional Mlgrass prairies,

Detailed information regarding forage quality and pasture productivity of various species and combinations that support rapid animal gains in the southeastern USA is needed for successful stocker cattle performance prior to feedlot placement. To evaluate productivity and quality of pastures for grazing beef (Bos taurus L.) steers, an experiment was conducted in 1979-1981 on a Typic Hapludalf. The 1.2 ha pastures were (i) Midland bermudagrass (Cynodon dactylon (L.) Pers.) + tall fescue (Festuca arundinacea Schreb.) seeded in 2S-cm rows + N, (ii) Midland + fescue in 2S-cm rows + legumes, (iii) Midland + fescue in SO-em rows + legumes, (iv) fescue + legumes, (v) common bermudagrass + fescue in 2S-cm rows + legumes, and (vi) orchardgrass (Dactylis glomerata L.) + ladino clover (Trifolium repens L.). Legumes refer to overseedings ofladino clover, red clover (T. pratense L.) and 'Kobe' lespedeza (Lespede:r.a striata (Thunb.) H & A). Midland + fescue at 2S em + N pastures were topdressed with 290 kg N ha -• each year.Pastures were grazed using a continuous put-and-take grazing management with stocking rate adjustments made to maintain orchardgrass at 8 to 14 em and other pasture combinations at S to 8 em. Forage growth and consumption were estimated by the cage-and-strip method. Yearling beef steers averaging 230 kg in the spring grazed 131 to 168 days and were weighed at 21-day intervals. Forage dry matter (DM) yield was 14.2 Mg ha -• for Midland + fescue at 2S em and ranged between 6.8 and 9.1 Mg ha-• for the other treatments. Forage consumption was 70% or more of growth in all treatments. Crude protein ranged from 134 to 158 g kg-•. Neutral detergent fiber ranged from 600 to 670 g kg-•, and acid detergent fiber was 390 g kg-•. Stocking rates were between 3.2 and 7.7 steers ha-•. Average daily gains were greatest on orchardgrass +clover (869g day-•) and ranged from 478 to 821 g day-• for the other pastures. Productivity was S91 animal grazing days ha-• for common + fescue at 2S em + legumes, 1S37 for Midland + fescue at 2S em, and ranged from 60S to 833 for the other pastures. Daily forage DM intake was 6.3 to 9.9 kg steer-•. Beef production was 392, 474, S10, S4S, S97, and 630 kg ha-• for common + fescue at 2S em + legumes, Midland + fescue at SO em + legumes, Midland + fescue at 2S em + legumes, orchardgrass + clover, fescue + legumes, and Midland + fescue at 2S em + N, respectively.

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