The use of the species-area relationship, or the accumulation species curve, to determine sampling sufficiency in phytosociological studies is a current technique, despite of being a controversial issue. The definition of an optimum sample size is based on the idea that the larger the sample size, the greater the number of species in the sample, but the rate of increase becomes progressively smaller so the curve tends to a flat line. The point where the curve becomes horizontal is the minimal area to represent the plant community: the sampling sufficiency. This concept assumes that the plant community is a spacially discrete entity with fixed species composition. In tropical forests, the identification of communities boundaries is particularly difficult and, due to their high species richness, the species accumulation curves do not become flat, even with large sample sizes. The species accumulation curve is unsuitable to determine optimum sample size in tropical forests because these curves do not behave as expected, futhermore the concept of sampling sufficiency itself rests upon a problematic definition of plant community.
phytosociology; sampling sufficiency; species-accumulation curve; species-area relation
