Fine-scale spatial structure in a grassland community: Quantifying the plant's-eye view

Abstract

1. The fine-scale spatial patterns of Agrostis stolonifera, Holcus lanatus and Lolium perenne were recorded in an English lowland grassland as presence/absence maps from 400-cell quadrats at two different scales (2 × 2 cm or 8 × 8 cm cells). 2. Local spatial structure in these patterns was quantified using spatial covariance functions. Distance- and direction-dependent components were examined separately for both intra- and interspecific patterns. The significance of departures from randomness was determined using Monte Carlo techniques. 3. The smaller-scale data showed that all three species were significantly aggregated, Agrostis to a greater distance (8 cm) than Holcus or Lolium (4 cm). The intensity of aggregation decreased in the order Lolium > Holcus > Agrostis. The larger-scale data suggested that this aggregation extended to greater distances, and that it was most intense in Agrostis. 4. Despite the lack of visual directionality in the environment, Agrostis showed a directional pattern at both scales, with Lolium varying in the same direction at the larger scale. 5. Only Agrostis and Lolium showed a significant interspecific relationship (segregated to 2 cm at the small scale, but aggregated to 8 cm at the larger scale). There was no evidence of directionality in the interspecific components of pattern. 6. The nature of spatial structure appears to depend on the scale of observation, but the smaller-scale data are more likely to provide a biologically interpretable measure of local spatial structure in this community.