Stem and branch form of 20-year-old radiata pine in relation to previous land use

Abstract

Summary The growth and form of 20-year-old radiata pine stands were assessed in relation to previous land use in Sunny Corner State Forest, near Lithgow, N.S.W. Basal area and merchantable volume were higher in ex-pasture (grazed land) and ex-improved pasture (grazed and cropped sites) than in an ex-native forest site, but the trees on former pastures were more deformed. A range of defects including multiple leaders, forks, stem sinuosity, butt sweep and heavy branching were most prevalent in the ex-improved pasture site. Up to 44% of trees in the ex-improved pasture were severely deformed and less than 50 stem ha−1 were considered suitable as sawlog quality trees. Only 12% of trees in the ex-native forest site had severe defects. Soil and foliar chemistry data showed that stem and branch deformities increased with increasing site fertility, and that deformity was directly correlated with soil mineral-N concentrations. Deformity was also correlated with foliar manganese, aluminium and calcium, and some defects were similar to symptoms of boron deficiency. The role of these elements in “poor form” requires further study. Stand density also appeared to affect deformity. The results suggest that high densities may partially counteract the effect of high site fertility in the development of stem and branch defects.