Plantation establishment

The early plantations were established with stock from small nurseries, which used seed from existing trees or overseas sources. From the very earliest days it was found that the use of open-rooted seedlings was satisfactory for most pines and this simplified nursery operations. The importance for good seedling growth of appropriate mycorrhiza-forming organisms in the nursery soil was noted by Kessell[11] in 1927 and this became a normal requirement in pine nurseries.

Nursery technology developed to keep pace with the expansion of planting programs and the better understanding developed through research. Nurseries became larger and operations such as root pruning to strengthen root growth and seedling 'lifting' became more mechanized, with much of the new equipment being developed in New Zealand. As early as 1939 propagation by cuttings was shown to be feasible by Jacobs at the Commonwealth Forestry Bureau[12] but this has only recently been adopted to any significant degree for the production of plantation stock.[13]

For the early plantations the clearing and planting operations were essentially manual and labour-intensiv -not such a disadvantage during the Depression years, when large areas were established -but became progressively more mechanized after the Second World War. From the earliest times much of the land used was abandoned farm land, or land carrying scrub or poor quality trees. When this was cleared and its vegetation stacked and burned it was observed that where ash beds had been, the subsequent growth of the plantation was improved. This so-called 'ash bed' effect was shown by Pryor[14] in 1963 to be due to increase in soil nutrients and possibly also to modification of the soil and its organisms by the high temperatures.

Mechanized planting of the open-rooted pine seedlings was introduced in 1950 using US-developed machinery and produced about a tenfold increase in labour productivity. Later developments in low ground pressure tracked vehicles gave the ability to establish plantations satisfactorily in poorly drained sites and extend the range of country that could be utilized. A ripping, ploughing and mounding technique developed in Queensland overcame soil compaction and pasture grass problems with former grazing land.

A major problem was competition from 'weed species' such as wattles that regenerated after clearing, burning and cultivating. They were originally controlled by hand cutting but in the 1950s chemical methods were introduced. Aerial spraying was begun in Victoria in 1967 but most spraying is now ground-based to achieve better control of distribution. The synergism between fertilization and weed control in their effects on early growth rate, indicated first by Waring and later quantified by Cromer et al., has now become a major consideration in plantation establishment.

Thinning

Thinning to remove suppressed and badly formed trees and to improve productivity from the remaining ones was not generally accepted in the early plantations as it was often believed that in the absence of a use for the wood removed its cost could not be justified. In 1933 the South Australian government entered into negotiations with APM for the possible utilization of thinnings in a pulp mill being considered for that State. Because of disagreement on the price for the thinnings, however, APM did not proceed with the mill and it was not until 1942 that a major use for them was found, in a small pulp and paperboard mill built by Cellulose Australia Ltd. at Millicent. Significant new outlets started to be created in the 1960s by the increased use of pine by the pulp industry and the start of the particleboard industry.

Australian Academy of Technological Sciences and Engineering