Contribution à l'analyse des structures forestières 1. Le grain des dominances

A method of simultaneous analysis of vertical and horizontal structure is described. It is particularly applicable to forest and shrubland. Data come from point-height analysis of vegetation: 100 sample points are arranged in 4 lines of 25, with 2 m between lines and 1 m between points on lines. At each point, specific lists of spaces intercepted optically are observed by vertical measurement strata. Strata depth is 10 cm when mean vegetation height is lower than 4-5 m, and 50 cm above this height. This study is based on height of upper vegetation presence, and applied to low forests of Nothofagus antarctica (Forest.) Verst. in Southern Chíle and Argentina. The authors summarize the data sequence by the cumulative sum technique. This technique allows the rapid and clear delimitation of three dimensional mosaic units of vegetation whose height varies vertically from the mean height. The pattern of these mosaic units is shown as three dimensional block diagrams, giving a good representation of structural dominance patterns.