Dans la région de N'Djaména, la présence de colonies de Cyanophycées psammophiles (Scytonema sp.) a été relevée sur de nombreux pâturages. Cette présence semble liée à une diminution de la biomasse herbacée par imperméabilisation de l'horizon superficiel. Dans le cadre de cette hypothèse, elle serait à l'origine d'une accélération des processus érosifs, en facilitant le ruissellement d'une part et en diminuant la protection des sols réalisée par les pailles d'autre part. Par ailleurs, il apparaît que la présence de l'algue est liée à un certain appauvrissement du cortège floristique; ce phénomène marquerait donc le début de la dégradation des pâturages sur sable et aurait valeur d'indicateur
2D URING the academic year 1948-49, one research team of the Laboratory for Research in Social Relations undertook an exploratory study of the relations between certain aspects of group behavior and individual characteristics. The results of that study are presented in this and subsequent articles. The present report describes the groups and methods used in the research; it also analyzes the stability of the thirteen small groups studied, and their similarity and disparity on selected sociological and psychological characteristics. Test-retest performances on personality and sociometric measures are analyzed, and selected variables are related to measures of satisfaction with experiences in the group residence units.Subsequent articles will appear on the following topics: methodological problems in the study of interrelationships among group members; factors associated with the productivity of groups; leaders, followers, and isolates in small organized groups; leadership structures in small organized groups; and cohesiveness in groups.The nature of this study and its purposes deserve brief comment. It was designed to be descriptive, primarily, and productive of hypotheses; it was to deal with an actual field situation, with the attendant complexity of variables; it was to provide an opportunity
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