This paper reviews the effects that resource manipulations, especially nutrient additions, have on productivity, diversity, species interactions and succession in natural and semi-natural low-growth-form terrestrial vegetation. In most studies, fertilization has resulted in an increase in productivity with a concomitant decrease in species diversity. Plant community productivity in nutrient-poor habitats (e.g. arctic tundra) however, has been relatively little affected by nutrient additions. Results from several fertilization experiments in nutrient-poor habitats indicate that competition may be an important component of community dynamics. Resource additions generally do not affect co-occurring species equally. In many cases, this results from an alteration of the relative competitive abilities of species. Several short-term fertilization studies have suggested that the rate of succession is increased by the addition of nutrients. Opposite trends however, have been reported in long-term studies. Contradictory results among some resource manipulation studies appear to stem largely from design limitations (e.g. only one resource was manipulated). Variability in habitat fertility, the type of resource added and the duration of enrichment also contribute to the difficulties involved in interpreting and comparing field experiments. A pluralistic approach combining glasshouse studies with both neighbour and resource manipulations in the field can be expected to lead to a greater depth of understanding of current controversies over the effects of habitat fertility on the intensity of competition and the relationship between competitive ability and tolerance of resource impoverishment.