Species Data from Other Attributes
A description of species composition can be obtained when procedures are followed to determine other attributes, such as biomass, cover, or density, provided the data is collected at the species or species group level. Species composition is calculated by expressing the contribution of each species relative to the value determined for the entire site, ie.,
This calculation must be repeated for each species or species group. Obviously, species composition cannot be correctly evaluated if all components of the vegetation are not included in the data, such as when sampling objectives focus on a few key species.
Frequency is generally regarded as an unsuitable basis for the description of species composition, because simply recording the presence of a species does not indicate its absolute amount.
References and Further Reading
Barbour, M.G., Burk, J.H., and W.D. Pitts. 1987. Terrestrial plant ecology. Benjamin Cummins Publishing Co, Menlo Park, CA. 2nd ed. pp. 191-193.
Heady, H.F., and G.M. Van Dyne. 1965. Prediction of weight composition from point samples on clipped herbage. Journal of Range Management 18:144-148.
Laycock, W.A. 1985. Density as a Method for Measuring Rangeland Vegetation. In W.C. Krueger. (Chairman). Symposium on use of frequency and density for rangeland monitoring. Proceeding 38th Annual Meeting, Society for Range Management, Salt Lake City, UT, February 1985. p. 96.