A STUDY OF THE OXYGEN REGIME AND ROOTING DEPTH IN DEEP PEAT UNDER PLANTATIONS OF SITKA SPRUCE AND LODGEPOLE PINE

Rooting depth, watertable depth and oxygen regime were measured in plo ts of Sitka spruce, lodgepole pine and a 50% mixture of each species p lanted on a deep unflushed blanket peat. The water-table was about 10 cm deeper and roots occurred about 2 cm deeper under the pine than und er the spruce or the mixture. In addition the mean concentration of ox ygen at 50 cm depth was significantly larger under the pine and the mi xture than under the spruce, showing that the rapid early growth of th e pine had started to dry the peat. There was no evidence of any impro vement in the growth of the spruce in the mixture compared to the pure Sitka spruce, suggesting that the expected nursing benefit had not oc curred.