JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Weather patterns significantly influence annual vegetation, both within and between years. The impact of these weather patterns on standing crop, cover, and botanical composition were investigated during the years 1955-1973 inclusive. Standing crop increased as the growing season progressed from March to June, while cover declined. Erodium spp. Carduus pycnocephalus, Geranium spp. and Hypochoeris glabra all declined between these 2 calendar dates.Other annual species increased in botanical composition as the growing season progressed. Weather patterns primarily influenced total standing crop during the initial period of plant growth. Following germination, temperatures were typically warm and conducive to plant growth; drought at this time suppressed total standing crop. Consistent precipitation following fall germination, and again during the period of rapid plant growth in spring, contributes to a "grass year" in the annual type. The sequence of freezing temperatures in relation to phenology of developing grass seedlings determines the relative proportion of annual grass species from one year to the next. Botanical composition of Trifolium spp. and Medicago hispida depends upon mild autumn weather, particularly when such fall weather favors none of the annual grass species. Botanical composition of Erodium spp. positively correlated with weather patterns associated with dry fall conditions. Multiple regressions of standing crop on weather patterns produced useful guidelines for manipulating animal units to achieve complete utilization of available forage, particularly when these equations were implemented in seasonal stages.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Allen Press andSociety for Range Management are collaborating with JSTOR to digitize, preserve and extend access to Journal of Range Management. This content downloaded from 91.229.248.154 on Tue, 17 Jun 2014 23:42:33 PM All use subject to JSTOR Terms and Conditions LITERATURE CITED BLACKMAN, G. E. 1935. A study of statistical methods of the distribution of species in grassland associations. Bot. Rev. 49: 749-777. CLAPHAM, A. R. 1936. Overdispersion in grassland communities and the use of statistical methods in plant ecology. Jour. Ecol, 24: 232-251. RAY, R. J. 1959. A phytosociological analysis of the tall-grass prairie in northeastern Oklahoma. Ecology 40: 255-261.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.