Annual production of native grasses on the Texas Coastal Prairie was decreased by 90, 66, and 67 kg/ha in 1978, 1979, and 1981, respectively, for each 1% increase in mixed-brush canopy cover in the range, from 12 to 57%. Differences in regression coefficients among years were not significant (P$0.05), although rainfall varied from 84% of the 26-yr average (91.5 cm) in 1978 to 150% of the annual average in 1981. Grass production during the growing season (May through October) only was decreased by 58, 113, and 78 kg/ha in 1978, 1979, and 1981, respectively, for each unit percentage increase in brush canopy cover. A greater proportion of the annual rainfall occurred during the growing season of 1979 than during the drier spring and summer of 1978. Native grasses typical of brush-free Coastal Prairie occupy the interstitial areas among the mixed-brush mottes, but bunch cutgrass (Leersia monandra Swartz) is the only grass that persists from the canopy edge to 1.5 m inward from the brush driplines. Little or no herbaceous vegetation grows in the centers of the mottes.

Establishment of seedlings of big sagebrush subsequent to range weed control treatments limits the economic feasibility of such treatments for increased forage production. This study investigated the dynamics of seed production by this species as one step in understanding seedling establishment. Studies were conducted on five different ecological sites along the arid extremity of big sagebrush distribution in western Nevada. Demography, physical dimensional parameters, biomass, and community structure were determined for each site and related to seed production over a 4-yr period. In addition, seeds harvested from each site were used to grow plants that were transplanted to establish reciprocal gardens at all sites. Seeds were subsequently harvested from the plants in these gardens. The average stand studied was capable of producing about 50 million seeds/ha annually. The plant characteristics most closely correlated with seed production were leaf weight, canopy density, and root crown diameter. The stand that consistently had the highest average seed production had the lowest woody biomass accumulation rate. In reciprocal gardens, plants grown from this stand had the highest average seed production. Seed production of big sagebrush plants appears to be related to site characteristics, shrub biomass characteristics, and inherent genetic potential of the plants in a given collection.

The purpose of this study was to investigate seed dispersal and germination of seeds in the soil as factors in establishment of big sagebrush seedlings. Seed dispersal began at seed maturity in December. Under the shrub canopy the dispersal of seeds was greater to the east. Between shrubs the dispersal of seeds tended to be uniform. For 6 months of each year there were no detectable germinable seeds in the litter and surface soil at the sites sampled. Germinable seeds in the soil increased rapidly during seed dispersal but were not detected by June of the next season. Enrichment of bioassay samples with GA3 or KNO3 did not enhance emergence of big sagebrush seedlings. Big sagebrush seedlings were found at very low densities in areas previously burned in wildfires. This suggests the presence of viable big sagebrush seeds in the soil at a very low density.

Brownspine pricklypear (Opuntia phaecantha Engelm. & Bigel.) was effectively controlled within 2 yr following application of a 1:1 mixture of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] and picloram (4-amino-3,5,6-trichloropicolinic acid) at a rate of 0.6 kg ae/ha. Brownspine pricklypear canopy cover and dry weight declined from approximately 23% and 3800 kg/ha to 8% and 1600 kg/ha, respectively. No significant difference in total herbaceous forage dry weight was found between plants growing inside brownspine pricklypear canopy areas and plants growing outside the canopy areas. Differences between areas in species composition were significant in that cool-season grasses dominated the canopy area of the brownspine pricklypear colonies while warm-season grasses dominated the area outside the canopy. Control of brownspine pricklypear will enhance livestock carrying capacity of rangeland in the Rolling Plains of Texas by increasing forage availability but not forage production.