Revision of a growth and yield model for radiata pine in New Zealand

This paper describes a major revision of a stand growth model for radiata pine belonging to N.Z. Forest Products Limited. Estimated growth and yields obtained from unthinned and specified thinned regimes are predicted from a stand level simulator. A fully compatible stock and stand table is also produced from single tree equations. The functions and methods used to calculate these statistics are described, and their rationale discussed.     

Modeling internode length and branch characteristics for Pinus radiata in New Zealand

It is recognized that estimation of internode length and maximum branch size is important for the prediction of clearwood in unpruned timber stands, as well as for evaluating the quality and value of logs in general. A review of existing branch models reveals a diversity of approaches as well as a tendency for results to be species specific. Here, a branch model is developed for Pinus radiata in New Zealand, capable of predicting successive internode lengths, the number of branches on each branch cluster, and the size of each branch up to the green crown (GC) at site index age 20. Inputs to the model include tree height and diameter at breast height (dbh) (both at age 20) and basal area per hectare of the top 100 stems. Further optional inputs are an ocular count of the number of branch clusters up to the green crown, and branch factor (BF)—the size of the biggest branch in the first cluster encountered above 6 m. The vertical distributions of internode length and maximum branch diameter are found to reach maxima around 0.3–0.4 of relative height. Internode length and the number of branches per whorl were found to be independent of tree size, site index and stand density. Stems per hectare is not required as an explicit predictor variable but it appears implicitly through tree dbh. Some model output is given and the results are discussed.     

Utility of multivariate analyses in examining foliage composition and soil nutrition in a factorial fertilizer experiment

The data for this paper were derived from a previously reported field trial with Pinus radiata which was treated with fertilizer at planting and three subsequent occasions. The experiment tested factorial combinations of urea (n), dicalcium phosphate (p), gypsum (s) and potassium chloride plus trace elements (b).At 5 years-of-age bole development was substantially increased by p alone, but p and n in combination increased growth further still. Urea, applied alone, had no, or retardive effects. Foliage concentrations of N, P, K, Ca, Mg, Fe and Mn were raised by p or n and p in combination, but Zn concentrations were not changed. Urea alone caused significantly lower Fe, Mg, Ca, and K concentrations in foliage.The 16 fertilizer combinations created a series of diverse soil nutrient conditions. For the ameliorative treatments (p and np), soils were characterized by high levels of total P and N, and exchangeable NH ₄ ⁺ and Ca ²⁺ whereas soils treated with n alone had low levels of the cations Mg²⁺, Ca²⁺, and Na⁺, but higher A1³⁺. While not contributing to stem growth, the s and b treatments also formed unique soil nutrient concentrations; s induced appreciable increases in Ca²⁺ while b resulted in a 3.5-fold increase in K⁺.Multivariate statistical analyses aided examination of the experimental data, whereas univariate analyses became cumbersome or repetitive, or gave no insight into individual contributions to overall variation. Eigenvalues extracted from discriminant analyses did provide this information, and ranked effects in order of importance. The effects of urea fertilizer on concentration of a number of elements in the foliage and on soil nutrient status were small but had marked effects on growth. It is envisaged that multivariate techniques can be utilized with other trial data, provided such experiments are soundly designed and adequately replicated.