Experimental Studies on the Weed Communities on Cultivated Land : II. The types of individual distribution of the important species and the law of geometrical progression of species on the weed communities

Abstract

(1) The mode of distribution was examined based on the dispersion diagram (unit area 6×6, 3×3 sq. cm.). It was calculated by means of X2-test for the deviation from the POISSON distribution, POISSON type by BLACKMAN, double POISSON type by THOMAS and POLYA-EGGENBERGER type on the important species in weed communities on various crop fields and fallow fields. (2) It is generally recognized that the distribution types of species such as Polygonium Blumei, Digitaria adsedens, Cyperus Iria, Dopatorium junceum, Rotala indica, etc. which propagate by scattering seeds were fitted satisfactorily to POISSON series of random distribution, when the, goodness of fit by means of X2-test was tested, though there were two types, one was more suitable to BLACKMAN'S value and the other to THOMAS' value, when the, value of actual density (D) to BLACKMAN'S type (m) or THOMAS type m(1+λ) were compared respectively (Table l). But the distribution of weed species including Aneilema Keisak, Eleocharis acicularis, Juncellus serotinus, which propagate by such an organ ds root, solon, rhizome, was fitted to THOMAS' type and PE type of contagious distribution. (3) It was recognized a linear relation as the fitness of MOTOMURA'S law of logarithmic series, namely, the log. number of individuals-rank and the log. weight-rank of species relation were shown on some growth stages on the weed communities in fallow field. Then before and after of these stages it was indicated L-type or S-type (Fig. 1). It is also shown a linear relation from the community including rice crop plants and weeds (Fig. 2). Such a linear relation seems to indicate a kind of the temporary stability of interspefic competition.