No abstract

AcknowledgmentsI thank all those who helped with this effort over the years. Special recognition, however, is due Stanley E. Westfall, range technician with the Station, and Roni J. Lavine, student aid, who were my mainstays.

Concerns for the future of California's oak-woodlands have intensified the need to better understand how different overstory species affect herbage standing crops and species frequencies. Data from over 8,000 plots harvested between 1961 and 1968 at the San Joaquin Experimental Range in the Sierra Nevada foothills of central California show that peak standing crops averaged 2,795 kg/ha in the open; 3,086 kg/ha under blue oak (Quercus dougkr-s&l,840 kg/ha under interior live oak (Quercus wislizenii); 1,696 kg/ha under digger pine (Pinussabiniana); and 1,917 kg/ ha under buck brush (Ceanothus cuneatus). Overstory species affected standing crops differently on different range sites. On swales, standing crops were less under live oak and digger pine than in open areas. On open-rolling uplands, standing crops were less in the open and under live oak than under blue oak. On rocky-brush uplands, standing crops were less under all other overstory species than under blue oak. Data on species frequency suggest that herbage species of later successional stages are more common under trees. The frequency of plant species varied with the species of overstory, and a diversity of overstory species may help to maintain adequate species diversity among understory species.

Herbage production is important to all concerned with range land. The range conservationist aims to grow the largest amount that can be used efficiently. The rancher must do the harvesting. The research worker tries to evaluate the herbage production processes. All are interested in the rate of herbage growth, the maximum production reached, and the decline in available herbage during the dry season. Much research into the California annual type stipulates sampling at the time of maximum weight. If the moment of maximum herbage weight is short a lengthy period of sampling may confound normal seasonal changes with pasture or treatment differences. A normal decline of herbage weight following maturity is a loss of forage that may be falsely attributed to grazing. This study was concerned with the problems of how long herbage weights of species and of the plant community remained at or near maximum and the magni-1 Currently Rang e Conservationist

Methodology for assessing trend in range condition is still evolving. This paper demonstrates use of Dice's community similarity coefficient, 2a/(2a + b + c), with communities present at 3 times and a notional community as a goal. Coefficients range from 0 (indicating a complete lack of similarity) to 1 (indicating complete similarity). Similarity is classed as low (0-0.25), moderate (0.26-0.50), high (0.51-0.79, or full (0.76-1). Study of time-goal coeffrcent graphs is suggested for deciding whether trend is up, down, or static. Defining goals and lack of statistical tests are major limitations. The goal concept and use of data standardization are discussed.