Changes in nutrient heterogeneity along sand dune and slack chronosequences at Tentsmuir Point, Eastern Scotland

Recent models have attempted to explain species coexistence and community structure by resource heterogeneity at a spatial scale below that of the individual plant. In this paper, we examine how heterogeneity changes through time. A comparative study of the heterogeneity of pH, phosphate, nitrate and nitrite levels was made within and along a transect inland from the shore at Tentsmuir Point, Fife, Scotland, an example of primary sand dune succession. This locality provided marked topographic relief created by dunes and slacks, and a well-characterised chronosequence. Soil samples were taken at the intersections of grids in quadrats. To examine macroscale heterogeneity in soil constituents, these intersections were 1 m apart in each direction in a large quadrat (5 m × 2m); for microscale heterogeneity they were 0.1m apart in a smaller quadrat (50 cm × 20 cm).

Mean concentration levels, and spatial heterogeneity of the values of nutrients and pH changed with time through the stages of the succession. pH and nitrate showed a simple decrease with time, whereas the other nutrients showed a more complex pattern of change.

Microscale heterogeneity was found to be greater than macroscale heterogeneity. Furthermore, principal components analysis of the two data sets showed differences in the main axes of variation, such that in the macroscale data set the main axis showed a trend from dune sites, through fresh water slacks to those influenced by salt water, while in the microscale data set the main axis related to levels of nitrogen.