Characteristics Of Soil And Productivity Of Pinus Radiata (D. Don) In New South Wales. I. Relative Importance Of Soil Physical And Chemical Parameters*

Aust. J. Soil Res., 1986, 24, 95-102

Characteristics of Soil and Productivity of Pinus radiata (D. Don) in New South Wales. I. Relative Importance of Soil Physical and Chemical Parameters*
N. D. ~ u r v e y A., B. ~ u d r and J. ~ u r n e r ~ ~ a ~
*Forestry Section, University of Melbourne, Parkville, Vic. 3052. "New South Wales Forestry Commission, Sydney, N.S.W. 2000.

Abstract Theobjectives of the study were to determine whether selected soil physical and chemical parameters could be used as predictors of site and the productivity of Pinus radiata (D. Don). The study was carried out in the Lithgow district of New South Wales. Sixty plots were located in first-rotation unthinned stands of P. radiata of age 11 years. None of the stands had received fertilizer. The stands wereselected to cover a wide range of merchantable volume production (0-175 m3 ha-'), and were located on a range of geological types including siltstone, medium-grained quartz sandstone, conglomerate, and rhyolitic tuff and lava. Soil depth was positively correlated, and per cent sand negatively correlated with all stand production variables. No other soil physical-or chemical variables were correlatedconsistently with stand variables. Discriminant analysis was used to test for the ability of a selected subset of soil physical and chemical variables to discriminate (a) between three volume production classes, and (b) between three geological groups. Soil depth, per cent sand, and total nitrogen contributed to two functions which discriminated between volume production groups. Cation exchangecapacity, Bray phosphorus, per cent sand, exchangeable sodium, and total nitrogen contributed to two functions which discriminated between geological groups. Thus soil physical parameters were predominant in discriminating between volume production groups, and soil chemical parameters were predominant in discriminating between geological groups.

Introduction The need to define soil parameterswhich affect wood production arises from the economic advantages of improved silvicultural management of plantations and improved prediction of wood volume and piece size production over a planted estate stratified on a pertinent pedological basis (Turvey 1980, 1983). Knowledge of the relative importance of soil parameters restricting tree growth should allow for subsequent amelioration of siterestrictions and improvement in yield on poorer sites. Site definition using soil surveys based on criteria observable in the field are cheap, on a per hectare basis, relative to other silvicultural costs, but the costs of soil surveys based on criteria measurable only in a laboratory are much more expensive (Burrough et al. 1971; Turvey 1984.) Thus the unit area cost and overall cost of a soil surveycan be reduced and the survey made more effective if important soil parameters observable in the field are defined as delineators of site.

* An earlier version of this paper was presented at the Symposium, 'Soil physical factors and forest tree growth', Forestry Section, University of Melbourne, Creswick, Vic., 20-21 August 1984.

N. D. Turvey et al.

In the management of forest areasvarying quantities of information are required on soils, and hence differing resources and survey techniques are needed to obtain it (Turner 1985). Within any one geographical region of broadly similar climate, the relative importance of a range of soil parameters for defining site may vary according to geological variation and the range of resultant weathering products. Thus within such a region theparameters of soil depth, soil texture, nutrient status, organic matter etc. will vary with one another across lithologies. Soil parent material as a delineator of forest productivity or other forest management activity can provide a relatively cheap classification, since geological maps are often readily available for otherwise pedologically unmapped forest areas. Turner and Holmes (1985)...