DISTRIBUTION OF SOIL INVERTASE IN RELATION TO THE ROOT SYSTEMS OF PICEA-SITCHENSIS (BONG) CARR AND ACER-PSEUDOPLATANUS L DURING DEVELOPMENTOF YOUNG PLANTS

A method is described for sampling rhizosphere soil under newly establ ished Picea sitchensis and Acer pseudoplatanus. The technique involves taking soil samples to a depth of 150 mm at 100 mm intervals along tr ansects, each 45 degrees from its neighbour, radiating from the base o f the stem. Invertase activities were measured in the soil samples and compared to their activities in fallow and rhizosphere soils. When th e field soil was dry, the tree root systems were carefully excavated t o retain as many fine roots as possible. The distribution of the soil invertase was matched to the spatial distribution of the roots showing the precise position of the rhizosphere relative to the initial 'blin d' soil sampling. Statistics were applied to derive equations for calc ulating the percentage enzyme activity relative to that found in rhizo sphere soil at various locations radiating from the base of the stem. This information was subsequently applied to soil sampled under trees of the same age as those excavated to give a non-destructive method fo r sampling rhizosphere soil routinely from under a large number of tre es.