SEASONAL-VARIATION OF PHOSPHATASE-ACTIVITY IN WOODLAND SOILS

Seasonal variation of phosphatase activity in 0-5 cm soils from 1.6 m2 plots in 48 English Lake District woodlands has been studied. Six per cent or 21% of the total variation in phosphatase activity at the assay temperature of 13°C was seasonal if activity was expressed respectively as phenol liberated g-1 soil or cm-3 soil. No seasonal pattern of activity at 13°C was detectable within individual plots due to high within-plot spatial variation. By averaging the results of all 48 plots, a seasonal pattern was identified but this did not resemble the seasonal pattern of soil available P content. Two, possibly three, peaks of activity occurred during the year, one in summer, a second after leaf-fall in autumn and possibly a minor peak in spring. The highest activity occurred in mid-winter. When adjusted to field temperature, 19 or 37% of the total variation in phosphatase activity, expressed respectively in terms of g-1 soil or cm-3 soil, was seasonal. The same three peaks of activity were still apparent, but their relative heights were altered, with maximum activity occurring in summer. After adjustment to field temperature, the seasonal pattern could be detected in many of the individual plots, if activity was expressed in terms of cm-3 soil, and reflected the seasonal pattern of soil available P. Soil phosphatase data should be expressed in terms of activity per unit soil volume and adjusted to field temperatures, if the biological significance of the seasonal variation in activity is to be appreciated. © 1979.