Marcia J. Lambert

Nutrient cycling within a 27-year-old Eucalyptus grandis plantation in New South Wales

A 27-year-old stand of flooded gum (Eucalyptus grandis Hill ex Maiden) in the North Coast Region of N.S.W. was assessed in relation to aboveground distribution and turnover of organic matter, nitrogen, phosphorus, calcium, magnesium and potassium. Of the 453 t ha−1 of aboveground organic matter present, 394 t was in the tree, 42 t in the understorey and 28 t in the forest floor. The total nitrogen, phosphorus, calcium, magnesium and potassium contents of the stand were 739, 44, 1254 and 658 kg ha−1, respectively, and the understorey contained 35%, 35%, 16%, 24% and 49% of the above-ground distribution of these nutrients respectively. Although the developing rainforest understorey comprised a relatively small portion (9.3%) of the total aboveground biomass, it played a disproportionate role in nutrient accumulation and uptake, and had an annual net accumulation of 14%, 55%, 59%, 30%, 44% and 69% of the aboveground organic matter, nitrogen, phosphorus, calcium, magnesium and potassium respectively. The net annual removal from the soil was 30, 1, 38, 5 and 31 kg ha−1 year−1 for nitrogen, phosphorus, calcium, magnesium and potassium, respectively. Flooded gum had very high accumulations of calcium in the bark and the effect of this in nutrient cycling is discussed. An idealised management system, to exploit and optimise the nutrient cycle of flooded gum, has been hypothesided.

The relationship between sulphur and nitrogen in the foliage ofPinus radiata

SummarySulphur and nitrogen on a gram atom basis occur in organic forms inP. radiata foliage and seeds in a ratio of 0.030 and this is the same as the S:N in the proteins present in the organic material. The ratio is in close agreement with the ratio found by many workers for legumes and gramineous plants. The ratio was found to be constant for a very large number of samples collected over a wide geographic area of south-eastern Australia; for samples collected over a number of years from on and off ash-bed sites; for samples collected at different times of the year; for samples from various parts of the tree crown; and for whole seeds, seed coats and the fleshy part of seeds ofP. radiata.If total-N is known, organic-S is given by 0.030xtotal-N. This is the level of S actually required for the complete constitution of the plant material. If S is present in excess of this basic requirement, then sulphate-S is present and S is probably adequate. If total-S is not grater than organic-S, then a true S deficiency probably exists. Data on sulphur alone are not enough to assess the status of plants since the amount required is proportional not to the weight of the foliage but to the amount of organic nitrogenous substance to which the S contributes in a fixed proportion.In theP. radiata samples studied, there was no accumulation of nitrogen over that required to balance the organic-S present and hence it appears that nitrogen is only taken up at the rate at which sulphur is available and protein formation will be limited to the availability of nitrogen.

Effects of forest harvesting nutrient removals on soil nutrient reserves

SummaryIntensive harvesting of native eucalypt forests is carried out in the Eden area in the south east coastal region of New South Wales, Australia. Soil nutrient capital and nutrient removals in forest harvesting were estimated together with potential impacts of these removals on the nutrient capital balance. Soils were anlysed from eighty sites for phosphorus fractions, including organic phosphorus fractions, and total and exchangeable cations. Based on typical forest harvesting systems, it was found that 3–4 kg phosphorus would be removed per hectare. Due to equilibrium between the various soil phosphorus components, depletion would not be solely from the more available pools. It is expected that at least four forest rotations (320 years) would be required before any detectable change would occur, within forest communities. A similar depletion estimate was calculated for the potentially most vulnerable cation, calcium. The other nutrient cations, magnesium and potassium had considerably greater reserves.

Site variation in Pinus radiata plantations and implications for site specific management

Abstract685,000 ha of Pinus radiata(D. Don) plantations in Australia werecategorized using a matrix of mean annualrainfall, rainfall regime and Parent Rock Codefrom a Technical Soil Classification. Datawere obtained from a number of differentorganizations which in total managed nearly allthe Australian P. radiata plantations. The selected characteristics were those whichcould be obtained at an acceptable level ofconfidence from all sources. Such acharacterization of plantation sites provided asystem for utilization of technical informationand extrapolation of research results and alsoa basis for the development of Site SpecificManagement systems. Analysis of theinformation indicated the high degree ofvariability of environments in whichplantations have been established withinAustralia and also the distinctive nature ofindividual regions. Such differences betweenareas make extension of silvicultural andrelated information difficult from one area toanother without appropriate validation. Abroad comparison with 1.26 million hectares ofP. radiata plantations in New Zealandindicated only a small overlap of areas of sitetypes between Australia and New Zealand. Assumptions derived in one location on thesites, characteristics, models and/or genotypeswould require significant testing beforeconfident application could be undertaken toanother area. The value of a Site SpecificManagement system for research planning andapplication of research and operational resultswas demonstrated from analysis of a series ofexperimental trials assessing application offertilizer after thinning and from evaluationof soil carbon in P. radiataplantations.

Fate of applied nutrients in a long-term superphosphate trial inPinus radiata

SummaryNutrient contents of aPinus radiata stand, that is, aboveground tree, understorey, forest floor and soil to 200 mm depth, were estimated in a replicated fertilizer trial, treated 30 years previously. The fertilizer treatments were 0, 25, 50, 75 and 100 kg P/ha as broadcast superphosphate. Highly significant growth responses had been obtained to the applied P. Estimation of the P content of the stand showed that 129%, 89%, 72% and 67% of the applied P was found in the 25, 50, 75 and 100 kg P/ha treatments respectively. The larger losses of P at the higher application rates would explain the lack of increased response with the highest application rate, however, it also shows that significant quantities of P are still present after a period of 30 years, giving a basis for growth responses in the subsequent rotations. Elevated quantities of N, Ca, Mg and K were found in the treatments compared with the control and these could not be explained on the basis of atmospheric inputs. For the cations, uptake from deeper in the soil profile could explain most of the effect but not for the higher amounts of N which, in the case of the highest superphosphate treatment, amounted to an accumulation of 27 kg N/ha/yr. These nutrient changes together with increased soil organic matter contents are considered to have provided a long term increase to the site productivity.

Soil phosphorus forms and related tree growth in a long term Pinus radiata phosphate fertilizer trial

Abstract Soil P fractions have been estimated in a 30‐year‐old replicated superphosphate experiment established in Pinus radiata. The treatments were 0, 25, 50, 75 and 100 kg.P ha‐l broadcast applied and the timber productivity was increased from 144 m3 ha‐l to 396 m3 ha‐1 merchantable volume over 30 years. The soil P fractions were basically as in the Chang and Jackson 7 p fractionation procedure, except each fraction was further separated into organic and inorganic components. The total organic P fractions accounted for more than 55% of the total P and were correlated with changes in organic matter. The results indicated an equilibrium situation had developed between the various components and that, based on correlations with tree growth, the readily soluble organic fractions could be the most important P forms for long term forest productivity.

Available phosphorus forms in forest soils and their possible ecological significance

Abstract For a range of northern N.S.W. forest soils typical of Australian east coast forests, both inorganic and organic P have been determined on sequential soil extracts. Organic P was present in each extract, and in most extracts was a high proportion of the total P, regardless of soil type. Using the sum of the P concentrations in the most neutral extracts as an index of available P, the organic component ranged from 352 to 88% of the total available P. Soil parent material appeared to exert the strongest influence on both soil total P and on the proportion of organic P/total P which ranged from 26% to 81%. The results have been discussed in relation to soluble organic P and its availability in forest ecosystems. The soil organic P results have been discussed in relation to P availability and supply within the forest ecosystem.

Soil nutrient-vegetation relationships in the Eden area, N.S.W.: III. Foliage nutrient relationships with particular reference to Eucalyptus subgenera

Summary Foliar nutrient concentrations were determined for the dominant tree species occurring on plots established during a previously reported soil survey in the Eden area. Generally, within-species nutrient variation was low and few significant correlations were found between soil nutrient levels and foliar concentrations for individual species. However, foliar nutrient concentrations differed significantly between species and when the data for all species were pooled, significant relationships were found between foliar phosphorus, nitrogen, calcium, potassium and sulphur levels and soil chemical properties. The species with the higher foliage nutrient concentrations were clearly associated with the more fertile soils. Eucalypt subgenera are considered in relation to their ecology and nutrition, and distinctive relationships are concluded to exist between site nutrition and the distribution of Eucalyptus subgeneric groups.

Fertilization of Pinus radiata plantations after thinning. I Productivity gains

Summary Significant productivity gains (>30% increases in basal area and volume increment over 7 years) are identified as achievable by careful site and stand specific application of NP fertilizers to Pinus radiata plantations after thinning. Treatment effects are generally more pronounced for NP combination treatments than treatments involving application of N or P alone although site, plantation and treatment selection is critical to optimise productivity gains. Where foliar analysis indicates P to be growth limiting, correction of that deficiency is required before significant gain can be made by application of N. Annual growth responses peak in the period 2–4 years post-treatment and are less evident 6 years post-treatment in most trials. Climatic conditions, particularly rainfall in the growth seasons 1 to 4 years post-treatment, influence the magnitude of the fertilizer (and thinning) responses. Responses are apparent across the tree size class distribution in the treated stand. However the largest ...

Sustainable management of native and exotic plantations in Australia

The emphasis of plantation management changes as the resource and the market develop. This is especially the case when a plantation program is developing a new timber resource, is not the case with many of the Pinus radiata (D. Don) plantings in the southern hemisphere. Australia establishes and manages plantations of both exotic conifer and native hardwood (Eucalyptus spp.) plantations, and these vary in their stage of development. The tenure and objectives in establishment have varied, but some key aspects of the resources may be analyzed. Optimization of production per unit area was not a prime objective during the developmental stages of many exotic pine plantations. Currently, with increased commercial emphasis, this has changed to a greater focus on increased value through Site Specific Management and tree improvement through which gains of at least 20 percent are expected during the first stages. With a key objective of sustainability, questions regarding impacts of soils, water, and biological changes need consideration and are being addressed.The eucalypt plantation resource in Australia is smaller in extent than is the pine resource, but of increasing importance, especially as the plantations are perceived to be more environmentally and ecologically acceptable than exotic conifers. In the past, questions of productivity, especially in relation to impacts of natural pests and diseases, have been raised. Sustainability of all plantations is a critical aspect, however, for specific issues there are different emphases with different species. For example, the relatively, high removal of calcium in smooth barked Eucalyptus plantations is seen as important in long term forest management.