Patterns of plant species richness in relation to different environments: An appraisal

We review patterns of plant species richness with respect to variables rela ted to resource availability and variables that have direct physiological i mpact on plant growth or resource availability. This review suggests that t here are a variety of patterns of species richness along environmental grad ients reported in the literature. However, part of this diversity may be ex plained by the different types and lengths of gradients studied, and by the limited analysis applied to the data. To advance in understanding species richness patterns along environmental gradients, we emphasise the importanc e of: (I) using variables that are related to the growth of plants (latitud inal and altitudinal gradients have no direct process impact on plant growt h); (2) using multivariate gradients, not single variables; (3) comparing p atterns far different life forms; and (4) testing for different shapes in t he species richness response (not only linear) and for interaction between variables.