The Relationship Between Standing Crop in Sedge Meadows and Summer Temperature

A major focus of ecology today, as indicated by the activities of the International Biological Program, is upon various aspects of ecosystem productivity. In order that productivity may be estimated over broader areas than can be encompassed by direct measurement, it is desirable that indirect methods (cf. Lieth 1965) be devised whereby easily measured environmental variables can be used to predict either productivity itself, or quantities such as standing crop which, for unexploited vegetation of similar life form, are closely related to productivity. Brylinsky & Mann (1973) have shown recently that energy-related variables, particularly mean air temperature, length of growing season, and latitude, are excellent global predictors of freshwater phytoplankton productivity, which itself is highly correlated with phytoplankton biomass. Bray & Gorham (1964) have likewise demonstrated a strong correlation between worldwide forest litterfall, a reflection of forest productivity, and latitude, which integrates the influence of insolation, temperature, and length of growing season. The sedge meadows with which this paper deals are of much less importance than forests and freshwaters, but they do constitute a common feature of northern and midlatitude landscapes. Hence it is of value to point out that the magnitude of their standing crop, measured over a wide range of habitats, is closely related to summer temperature. This energy-related environmental variable may therefore be used in broad-scale studies to estimate approximate standing crops for sedge meadows where actual data are lacking but where data for monthly mean temperatures are readily available.