Bacteria of soil and pasture leaves at Claudelands Showgrounds

Summary

Leaf and soil samples from the Claudelands Showgrounds at Hamilton have been examined for seasonal changes and quantitative, taxonomic, and physiological differences.

The numbers of bacteria on the leaves are very much greater than in the soil and are commonly of the order of 100,000,000/g. wet weight. Numbers tend to be higher in summer and autumn and lower in winter and early spring. Conversely, the soil population tends to be lower in summer and higher in autumn, winter and spring.

Spore-forming bacteria form a major element of the soil Hora, but are uncommon on leaves. Conversely, micrococci are far more comm:m on leaves than in soil. Of the Gram-negative bacteria pigmented f1avobacteria are dominant on leaves hut not in soil. Aerobacter cloacae occurred both in soil and on the leaves but pigmented aerogenic fermenters also occurred on the leaves. Streptomyces are characteristically absent from the leaves.

The soil flora remained relatively unchanged throughout the year but the physiological character of the leaf flora showed marked seasonal changes particularly evident in the spring when the incidence of aerogenic fermenters rose sharply and there were appreciably fewer pigmented bacteria.

Despite the close physical proximity of the leaf and soil floras each preserves its integrity and its distinctive taxonomic and physiolorrical character.