The Seasonal Succession of Species in a Rice Paddy in Vientiane,Laos

A study was made of the community of organisms present in a rice paddy in Vientiane, Laos. The paddy was visited regularly for eighteen months, and the pattern of seasonal succession was studied. The major biological characteristics were noted including relative abundance of the 205 species observed. A few species were consistantly common whenever there was sufficient water in the paddy, but most had well defined seasonal periods during which they were abundant and actively propagating. In time the number of individuals of these dominant species declined and other species replaced them. During the part of the year that the field was flooded, four distinct aggregations of species succeeded each other. Thus, in the biological year of the rice paddy, two primary phases, dry and wet, were easily discernible, and within the wet phase, four periods could be defined by the successive aggregations of species. The species identified were similar to those reported to occur in the rice paddies of Northeast Thailand, but biological studies of Laos have been so infrequent that most species are reported for the first time from Laos, hence extending their geographical ranges.