DISTRIBUTION OF PRIMARY FOREST PLANT-SPECIES IN A 19-YEAR OLD SECONDARY FOREST IN FRENCH-GUIANA

Secondary succession in a 19-y old tropical rainforest of French Guian a was investigated through the distribution pattern of primary forest species. The experimental plot of 25 ha was logged to simulate conditi ons of a paper pulp cut. Enumeration of all plants of height greater t han or equal to 50 cm in 52 subplots 10 m x 10 m indicated the number of species and individuals in five species categories; short-lived pio neer species, pioneer species that persist in mature forest, primary f orest species capable of germinating in shade, primary forest species that indicate a preference for clearings (small gaps) in mature forest and understorey primary forest species. Change in proportion of the m ost abundant species (greater than or equal to 1 cm dbh) over the last 15 y indicated a decrease in short-lived pioneer species and an incre ase in pioneers that can persist in the mature forest. Proportion of s pecies categories per height class indicated that primary forest speci es were mainly found in the lower height class in this forest which is largely dominated by secondary forest tree species forming a canopy t hat rarely exceeds 20 m. Individuals of primary forest species were en countered on ARBOCEL as sprouts from large stumps, sprouts from juveni les or as untraumatised saplings or juveniles. The distribution patter n in a 4-ha area of 11 selected primary forest canopy tree species rev ealed an overall trend in recolonisation of this species category in t he secondary forest. Considered individually, the clustered distributi on of stems of Eperua grandiflora showed the importance of regeneratio n through sprouting or remaining individuals. The gradient distributio n, oriented from the edge to the centre of the studied plot, and displ ayed by the stem densities of Virola michelii, suggested a recent prog ressive dispersal of seeds. A more dynamic recolonisation front was ob served for the primary forest understorey species Cassipourea guianens is and was probably linked to both the initial logging conditions and the fact that this species fruits when relatively young.