Is the degree of spatial aggregation of Calluna vulgaris regulated by nitrogen deposition or precipitation?

Abstract

Most plant species display a certain degree of spatial aggregation that may play an essential role in plant community dynamics, e.g. in regulating the importance of interspecific competitive interactions. Here, the hypothesis that the degree of spatial aggregation may be regulated by environmental drivers such as nitrogen deposition or precipitation is tested. The degree of spatial aggregation of Calluna vulgaris was investigated using spatial pin-point cover data from 3797 Danish dry heathland plots. The pin-point cover data was analyzed using the Pólya-Eggenberger distribution, where one of the parameters measures the degree of spatial aggregation. The degree of spatial aggregation was found to covary positively with nitrogen deposition and negatively with precipitation. The degree of spatial aggregation was found to decrease with time. The observed patterns of spatial and temporal covariation need to be followed up by more mechanistic cause and effect studies of the effect of environmental drivers on spatial aggregation.