Variation in mosaic diversity in the forests of coastal northern New South Wales

Abstract

The measurement of diversity at the landscape scale is likely to suffer from many of the limitations that plague other measures of species diversity; there is little agreement as to how to calculate or interpret the measure or index. A recent addition to the suite of diversity measures is that of Scheiner's "mosaic diversity". In an attempt to accept Scheiner's challenge that "explorations of mosaic diversity among diverse landscapes ... will lead to new insights into the processes responsible for assembling species into communities" mosaic diversity has been calculated for 119 transects that sample the forests of the mid-north coast of New South Wales. Each transect is composed of five quadrats placed to encompass the variation in canopy floristic composition from xeric exposed slopes to mesic gullies. This paper looks at the environmental and spatial pattern of mosaic diversity. In addition I explore the relationship between mosaic diversity and other more readily grasped measures of diversity. Although very variable, Scheiner's mosaic diversity measure is shown to be weakly correlated with mean annual rainfall and mean annual temperature. In addition there is a weak trend in increasing mosaic diversity from the tablelands to the coast together with a trend of increase from south to north. Mosaic diversity did show a significant correlation with average species richness per quadrat within a transect but not with total species richness recorded on the transect nor with the number of alliances sampled by the five quadrats. The utility of this diversity measure to ecology remains unanswered by this study but the demonstration of weak relationships with both environmental and spatial variables given the small (5) sample size compared to that recommended (30+) suggests that further work is warranted.