On pattern in vegetation
In a study of distribution patterns in grassland vegetation density determinations were made in 154 stands, using stratified random samples of quadrats, and distance measurements obtained with the point centred quarter method. The results showed that individuals in the population, regardless of species, were randomly dispersed if the substrates were reasonably homogeneous, and disturbances were absent. Heterogeneity of the substrate, disturbances, and what may be termed successional development, commonly caused deviations from randomness, resulting in more or less pronounced aggregation. The exact form of aggregation depended on the mode of vegetative or sexual reproduction of the species involved. On homogeneous substrates, species occurring with high densities often were dispersed in a regular pattern, usually as regularly dispersed aggregates. The species involved were mostly bunch grasses, or herbs with branching caudices. The cause of "regular aggregation" appeared to be the breaking up of the bunches or caudices into several individuals, due to ageing of the plants.