EFFECT OF SLASH AND SOIL REMOVAL ON THE PRODUCTIVITY OF SECOND ROTATION RADIATA PINE ON A PUMICE SOIL

The effects of windrowing and skid site formation on site quality were examined in a 7-year-old, second rotation Pinus radiata stand growing on a yellow-brown pumice soil. Four site types were recognised — normal cutover, windrow, inter-windrow and skids. Standing volumes, after first thinning to 573 stems/ha, were 34.3, 40.7, 20.5 and 5.2m8/ha respectively. Relative to the normal cutover the overall windrowed area contained 7m3/ha less volume or the equivalent of a reduction in Site Index (mean top height in metres at age 20 yrs) of 2 m. Analysis of current season's foliage showed that N and B concentrations were lower on both skid and inter-windrow sites than on the windrow and normal cutover sites. Magnesium concentrations on the inter-windrow site were signifi-cantly lower than those on all other sites. Levels of total N and exchangeable Mg were lower in the skid site and inter-windrow soil profiles than in the normal cutover profile. Using regressions of soil depth on total soil N it was calculated that c. 2.5 and 26 cm of soil had been scalped off the inter-windrow and skid sites respectively