Soil-tree relationships in a forest of Pinus radiata with micronutrient deficiencies

Abstract

Multiple regressions of tree height and diameter on foliar nutrient contents of a second rotation 9-yearold Pinus radiata forest in an area with a history of micronutrient problems at Clover Hill (S.A.), showed low levels of copper and manganese and high chloride in trees with less height and larger diameter than normal. Areas which were swampy and had failed in the first rotation were better stocked than their surroundings in the second. Such areas were, however, more subject to disorder symptoms. The soils of the forest integraded and were: yellow podzolic, podzol, solodized solonetz and terra rossa. Swampy phases were observed in the podzol and particularly the solodized solonetz soils. Trees on the various soils had different foliar levels of copper, zinc, manganese, potassium, phosphorus, nitrogen, sodium and chloride. On increasingly swampy phases of the podzol, foliar copper and manganese decreased but nitrogen and sodium increased. The multiple regressions differed for the various soils; tree height increased and diameter decreased with higher foliar copper, manganese and nitrogen, whereas both increased with higher foliar zinc and sodium. On some soils the multiple regressions contained quadratic terms, enabling an estimate to be made for a 20% reduction in height (less than 1.5 ppm copper) or a similar increase in diameter due to tree malformation (less than 1.8 ppm copper). A similar reduction in height was also indicated when the foliar chloride was greater than 0.68 to 0.8%. Foliar phosphorus was unusually high at about 2.5 times the levels found in healthy trees in other forests. Statistical interactions between foliar nutrients did not contribute to the multiple regressions. Soil surveys to delineate saline and previously swampy areas should be part of future forestry investigations in the south-east of South Australia.