We examined how the occurrence and structure of grasses and woody plants changed after 12 yr of a fire season manipulation and removal of livestock herbivores. Applying high intensity fires in the summer preserved the structural integrity of this semiarid live oak (Quercus virginiana Mill.) savanna while decreasing or eliminating numerous problematic plants in the understory and overstory, such as prickly pear cactus (Opuntia spp.), sacahuista (Nolina texana S. Watson), Ashe juniper (Juniperus ashei J. Buchholz), Pinchot's juniper (J. pinchotii Sudw.), and honey mesquite (Prosopis glandulosa Torr.). In the less intense repeat winter burning treatments, undesirable woody plants were generally maintained at pretreatment levels in the overstory but all woody plants except Ashe juniper increased in the understory. Alternatively, areas excluded from fire in the control treatment rapidly transitioned from a grass-tree codominated savanna environment to one that is heavily dominated by woody plants. In the grass community, the most frequently occurring grass species in the winter burn treatment differed from summer burn and control treatments, whereas the summer burn treatment was not different from the control. Of the herbaceous plants, only little bluestem (Schizachyrium scoparium [Michx.] Nash) responded to fire treatments. Little bluestem increased in the winter burn treatment, remained fairly constant in the summer burn treatment, and decreased in the control. Other grasses varied largely as a function of annual weather variability, the removal of livestock, and legacy effects resulting from pre-existing variability. These findings suggest that fire can reduce or eliminate woody plant species that threaten the stability of live oak savannas while having little long-term effect on grasses desired by rangeland managers. Resumen Examinamos el cambio que hubo en la ocurrencia y estructura de gramíneas y plantas leñ osas después de 12 añ os de manipulación de la época del fuego y exclusión del pastoreo por el ganado. Por medio de la aplicación de alta intensidad de fuego durante el verano se preservó la integridad estructural de estas sabanas semiáridas de encino (Quercus virginiana Mill.) mientras decrecieron o se eliminaron una gran cantidad de plantas problemáticas que se ubican arriba y abajo de la cobertura arbórea, tales como especies de nopales (Opuntia spp.), sacahuista (Nolina texana S. Watson), Ashe juniper (Juniperus ashei J. Buchholz), Pinchot's juniper (J. pinchotii Sudw.), y mezquite (Prosopis glandulosa Torr.). En las áreas tratadas con fuegos de menor intensidad y repetidamente durante el invierno, las plantas leñ osas indeseables se mantuvieron generalmente en niveles existentes a antes de la aplicación de las quemas en la cobertura aérea, pero todas las plantas leñ osas excepto Ashe juniper se incrementaron en los lugares debajo de los árboles. Por otra parte, las áreas excluidas del fuego en los tratamientos que se usaron como controles cambiaron rápidamente pasando de ambientes dominados por pastos-á...

Research was conducted at the Sonora Research Station during a 4-year period (1984 to 1988) to measure differences in herbaceous vegetation response between two 'I-pasture l-herd grazing systems. Grazing tactics were short duration (SDG-7 days graze, 42 days rest) and high intensity, low frequency (HILF-14days graze, 84 days rest). Stocking rate for the 2 treatments was 10.4 ha/auy. Total aboveground net primary production (ANPP) varied significantly among years but not between grazing treatments. Signiflcant, divergent shifts in composition did occur over the 4 years as a function of grazing treatment. Shortgrass production in the SDG pastures increased from 45% of the total ANPP for year 1 to 74% for year 4. Shortgrass ANPP in the HILF pastures comprised 44% of the total herbaceous production for year 1 and 51% for year 4. Midgrass ANPP in SDG pastures comprised 3.8% of the herbact ous production for year 1 and 13.6% for year 4. Midgrass production in the HILF pastures represented 4.7% for year 1 and 33.9% for year 4. Our data indicate the SDG system did not promote secondary succession from shortgrasses to midgrasses as effectively as did the HILF system.

Ninety-eight and 88 female Angora kid goats (6 mo of age) were grazed/browsed on Edwards Plateau rangeland in 92- and 88-d trials in 1989 and 1990, respectively. The goats were either not supplemented (negative control, NC) or fed isoenergetic amounts of corn (C), a corn/cottonseed meal/molasses mixture (C/CSM), or a corn/cottonseed meal/fish meal/molasses mixture (C/CSM/FM). The C/CSM and C/CSM/FM supplements provided equal CP but different amounts of ruminally undegraded protein (UDP). The goats were allowed to graze/browse in a common pasture and were separated into treatment groups three times each week for feeding. Intakes of supplement and forage were measured using a dual-marker technique. Forage intake was not increased with supplemental feeding (P = .21), but tended (P = .08) to be greater with high-protein supplements than with C. Total digestible DMI was greater (P < .01) for supplemented goats and was not affected by supplement type. Supplemental feeding increased BW gain (P < .01) and clean fleece weight (CFW; P < .01). High-protein supplements increased BW gain (P < .01), CFW (P = .07), fiber diameter (FD; P < .01), and staple length (P < .01) compared with C. Greater amounts of UDP (C/CSM/FM) did not increase BW gain (P = .99) but tended to increase CFW (P = .12) and FD (P = .15). Supplemental feeding increased total digestible DMI by partial substitution (corn) for forage or addition (high-protein supplements) to forage, and both energy and protein increased BW gain and CFW and influenced mohair traits.