Use of mean distance between plants in determining adequate plot size


Category:  Range Science
Linked Publication
Language: English
Author(s): Mustafa M. Baasher
Description: At a certain stage in the development of any science, the quali tative approach gives way to the more precise and exact quantitative one. Workers in the various fields of applied ecology have of late increasingly felt the need for approaching the various ecological problems in a quantitative way. One problem of plant ecology at the present time is to understand the laws which govern plant distribution and to learn how to interpret these laws quantitatively. The quantita tive approach is by no means an end in itself, for data which are accumulated and compiled have to be interpreted and put into meaningful and useful terms. Interspatial relationship among individuals and aggregates of plants has been acknowledged recently as having meaningful ecological implications of importance in community analysis. The mere realization that plants are commonly over-dispersed rather than under-dispersed was considered by Ashby (1948) as the most noteworthy advance in statis tical ecology of the preceding 11 years. Such spatial distributions are dictated by a cause and effect relationship and do not occur haphazardly. Goodall (1952a) surveyed previous work based on average distance between plants. He concluded that the idea is worthy of further study and attention. Cottam and Curtis (1956) advocated the use of distances between plants in forest inventory and cruising work. This rather neglected quantitative character shows signs of being more tenable to objective approach than other commonly known but more variable quantitative characters. The quest for an objective method in sampling has been among the important goals of most workers in vegetation analysis. Questions as to chat plot size and plot shape are apparently answered at present on subjective rather than objective reasoning. Objectivity in this respect is claimed by some workers to be unattainable and unpractical. The literature of quantitative and applied plant ecology contains many suggestions of criteria that might be applied so that an objective selection of plot size or reference plot and minimal-area could be achieved (Cain, 1938; Archibald, 1950; Hopkins, 1955). How ever, none of these suggestions could stand the criticism put forward against them and they were later dismissed as being subjective or fallacious (Ashby, 1936; Cain, 1938; vestal, 1949). This should not imply any legitimacy in the use of the subjective methods and should not stop or hinder our earnest quest for objective alternatives. This paper is an attempt to use the average distancel between plants as a criterion for estimating the plot size or reference area which should be used for sampling a given vegetation union. The same could also be used to detect change or trend by being a "reference plot" for such a union and to detect the successional changes which are more or less reflected in the manner of distribution (Fracker and Brischle, 1944; Watt, 1947; Ashby, 1948).