Spatio‐temporal Processes in a Calcareous Grassland

Abstract

Abstract The herbaceous plant communities occurring on nutrient‐poor calcareous soils of north‐western Europe are typically rich in species, with as many as 30–40 species m‐2. It is an open question as to what dynamic properties allow this diversity. We review evidence that we have collected on the spatial and temporal processes operating in a calcareous grassland community in England to address this issue. Our data indicate spatial aggregation of individuals within species consistent with the modular growth of the species concerned, but there is little evidence to suggest spatial structure generated by interactions between species, and we have been unable to separate most species tested into different niches. The development of spatial structure of the community through time is also consistent with dynamics that depend principally on the modular growth patterns of the different species. We suggest that there is a nonlinearity in the per capita rate of increase with the property that the community is no more than weakly dependent on densities of the species under natural conditions. The dynamic of the community is then driven more by forces external to the community than by density‐dependent effects within the community.