Length- and Weight-Diameter Relations of Serviceberry Twigs

Abstract

In a study of the relation between serviceberry (Amelanchier alnifolia) twig diameters and twig lengths and weights, a total of 852 twigs from 110 plants on 11 different sites was examined. Equations for the regression of length and weight on diameter were developed. Despite significant variations in regression related to site, plant size, and twig location on the plant, relatively small sam- ples of browsed twigs were found to provide precise estimates of browse utilization. Estimates of big game browse utilization provide a basis for game range manage- ment in most western states. Methods used to collect this information vary from esti- mating overall percentage utilization (Al- dous 1944, Cole 1958) or length utilization (Dasmann 1951) to clipping shrub halves before and after browsing (Grimm 1939) and measuring marked twigs before and after browsing (Dasmann 1948). Almost without exception, clipping and measuring have proved to be expensive and tedious, while estimating lacks the accuracy desired for intensive range management. One way to circumvent these problems might be a technique that does not require repetitive measurement in the spring and fall. If lengths and weights of unbrowsed twigs could be determined from diameter measurements, a single postbrowsing sam- ple would replace two measurements of marked twigs. This paper reports the results of an in- vestigation of the relationships between twig diameters and lengths and twig diam- eters and weights of serviceberry in western Montana.