Physical damage on tropical tree saplings: quantification and consequences for competition through height growth in a neotropical rain forest of French Guiana

This paper deals with the quantification and the effects of physical damage on tree regeneration dynamics in the tropical rain forest. We define physical damage as breakage resulting in a greater than 20 % reduction in stem diameter and its associated effects. A study of physical damage at the community level was made in March 1994 in primary forest and forest disturbed by silvicultural treatments at the Paracou research site in French Guiana. The frequency of damage varies with diameter class and the degree of forest disturbance due to the silvicultural treatments, ranging from 14.9 % for saplings greater than 6 cm DBH in undisturbed forest to over 50 % for smaller saplings in disturbed forest. Study at the specific level was made at the same site on saplings of three tree species with contrasting ecological temperaments, Bocoa prouacensis, Pradosia cochlearia and Goupia glabra, from March 1994 to March 1996. Damage frequencies varied from 34 % for saplings of the pioneer species Goupia glabra to 64 and 60 %, respectively, for the more shade tolerant species Bocoa prouacensis and Pradosia cochlearia. Physical damage does not directly influence height or diameter growth rates nor mortality within a species except for Pradosia cochlearia. However, diameter growth rates irrespective of damage are significantly different between species. Under certain circumstances, stem breakage may be an influential factor affecting the long term survival of pioneer species saplings because it modifies their social status. ((C) Inra/Elsevier, Paris.).