Growth response of Eucalyptus clones to different soils in a nursery environment

[摘要] ENGLISH ABSTRACT: A nursery clonal test of 20 clones was established at the University of Stellenbosch on eightsoil treatments consisting of combinations of four soil types and two lime levels. One clonewas from first-generation and 15 were from second-generation Eucalyptus grandis selectedin 13 different open pollinated family trials and two full-sib trials. Three hybrid clones wereselected from two E. grandis x E. camaldulensis and one E. grandis x E. urophylla families.Soil collection was done in four different places in the Western Cape, specificallyLourensford near Somerset West, Pampoenvlei near Malmesbury and Grabouw andHelshoogte near Stellenbosch. The yellowish soil from Grabouw and the reddish soil fromHelshoogte were clayey while the black and light soils from Lourensford and Pampoenvleirespectively were sandy soils. Two lime levels, with or without lime application, on thesesoils generated eight soil treatments.Results are firstly presented in tables and the delineation of significant differences betweenthe rankings of clones, replications, soil types, soil treatments for selected variables given byDuncan's New Multiple Range Test is included.Graphical presentations are used to illustrate some of the trends over all the single effects,that is soil types, lime levels and clones. Analysis of variance for the simplified modeldetected a highly significant difference for soil treatments, which is the combination ofdifferent soil types and lime levels. Quite strong correlations between the soil treatmentswere also evident.Assessments of height, diameter, root and shoot mass were made at age 12, 18 and 24weeks. Number of branches was assessed at 24 weeks.All the single effects were found to be statistically different for most variables at all ages. The most outstanding on the two-way interactions is the general insignificance of clone xsoil type, clone x lime and soil type x lime interaction, for height and diameter growth butindeed not for shoot mass and root mass. This might mean that height and diameter alone arenot sensitive enough but when leaves are induded in mass (like a volume) then moreexpression is obtained justifying the interaction found at 24 weeks for root and shoot massfor all two-way interactions. Generally the three-way interaction seems insignificant. Onceagain, shoot mass shows some sensitivity being perhaps an indication of whole treeresponse to environment.Analysis of variance for the simplified model showed that soil treatment (soil type x lime),results were highly significant for all the variables studied. When diameter and height meanswere studied in terms of phenotypic correlations between sites (soil treatments), quite strongcorrelations were evident between the soil treatments.Clone x soil treatment interaction, was also detected by means of regression coefficients.Some clones were found to be stable for variable shoot mass, for instance, AG I, AG3-B,AG6, AGl2 and AGI4. Average stability clones were GUI, GCI and GC2 while unstableclones were identified as AG5, AG8, AGII, AG13 and AGI5.The magnitude of genotype x environment interaction is low implying that it will not affectbroad sense heritability ( there are too few clones to reliably estimate) as well as geneticgain. It is noted that genotype x environment interaction tends to disappear for height anddiameter over time, while it remains for shoot mass (volume of the tree) and number ofbranches at age 24 weeks.The results from this study are encouraging for further research aimed at developingtechniques for early prediction of genotype x environment interaction in eucalypt trees.

[发布机构] Stellenbosch University