Stem deformation in Pinusradiata associated with previous land use

Abstract

Pinusradiata may exhibit moderate to severe stem deformity (Toorour syndrome) when planted on ex-pasture sites in southern Australia. However, the deformity does not occur on ex-eucalypt forest sites unless N fertilizer is applied. While the symptoms of Toorour syndrome are visually similar to those induced by Cu deficiency, the syndrome is associated with high foliar Cu concentrations (and concentrations of Mn and Zn). Furthermore, although Cu-deficient trees typically exhibit lower stem lignin concentrations than nondeformed trees, there is no apparent reduction in the stem lignin concentrations of trees exhibiting Toorour syndrome. Unlike Cu deficiency, the syndrome is not alleviated by Cu fertilizer applications. From comparisons of soil chemical properties between ex-pasture (deformed) and ex-eucalypt (nondeformed) sites, across a range of soil types and lithologies, it is concluded that (i) the syndrome is associated with previous land use rather than soil type or lithology, (ii) the syndrome is associated with the high fertility of ex-pasture soils, in particular, high NO3-N production, relative nitrification, and Mn availability, and (iii) it is unlikely that the syndrome is a consequence of single trace element or other element deficiencies.