Scale-dependent variability of density estimates and morphometric relationships in subtidal stands of the kelp Lesson/a trabeculata in northern and central Chile

Abstract

Several morphological parameters, and estimates of density and evenness per depth, were analyzed for stands of the subtidal kelp Lessonia trabeculata Villouta et Santelices from 2 zones, central and northern Chile. Two sites in each zone were sampled for 2 yr, and variability patterns were statistically described using site or zone as classification factors. Bathymetric profiles of density showed a strong qualitative and quantitat~ve variation among sites, contrasting with the high evenness in spatial distribution of plants per depth interval, despite intervals of varylng length. Relationships among morphometric parameters changed markedly across spatial scales, producing a high variance in biomass predictions. In most cases, strong site-and zone-specific components were identified, which account for the variability in morphology at both spatial scales. Zone effects may mirror water motion and temperature regimes, among other factors, and site effects may be related to specific habitat configurations. These results show that extrapolation from structural features of single stands for characterizing species may result In misleading inferences. The detection of scale-dependent patterns proved to be a useful starting point for comparative studies of population structure, and necessary before attempting generalizations.