The effect of quadrat size, plant size, and plant distribution on frequency estimates in plant ecology

The theoretical foundation for frequency estimates, as used in plant ecology, is discussed. An equation is derived in which the absence value is linked with the quadrat size, the plant unit size, the plant density, and the aggregation of the plant units. Graphical methods are used to estimate the density and the average size of the individuals of a species for a random distribution. Departure from a random distribution can also be detected by these methods. It is shown that if an estimate of the average plant unit size is combined with the frequency estimates, then the reliability of the results is increased considerably. The value of frequency estimates made with one, two, or more sizes of quadrats is discussed