An Ecological Guide to New Planting Areas and Site Potential for Hoop Pine

Abstract

The need to extend the planting of hoop pine (Araucaria cunninghamii Ait.) in the subtropical region close to Brisbane in south Queensland and northern New South Wales, involves the prediction of site quality for this species in areas not previously considered for planting. The ecological relations and seral status of hoop pine are outlined. Phytogeographical evidence suggests that araucarian vine forests do not fully occupy suitable soils in the moist subtropical region because of past climatic changes and destruction by wildfires. Ecological and practical considerations suggest that the most favourable climatic zone for hoop pine planting in south Queensland and northern New South Wales is at altitudes below 2,000 ft (mean annual temperature above 62°F) and with average annual rainfall over 32 in. There is a dominant control of site index by soil mineral status provided that the soils are not excessively or poorly drained. An empirical scale of soil mineral status in relation to composition of parent rocks and topography is given for nine lithological types in south-eastern Queensland. The relationships of these soil factors and annual rainfall to the site index of hoop pine are shown diagrammatically. Site potential for hoop pine may also be predicted indirectly from indicator species and from the structural type of vine forest vegetation known to occur, or which may be presumed to be capable of occurring on a given site if fire were excluded. Site potential is higher in those vine forest types in which hoop pine occurs early in succession, and vice versa. Three extensive areas not yet exploited for hoop pine plantations are located; steep slopes on basaltic uplands, hilly areas on acid metamorphic rocks enriched by basic rocks, and rolling country derived from andesitic rocks in the 32–40 in. rainfall zone. The use of fertilizers in other areas, and problems of control of grass competition and resumption of unproductive freehold lands are briefly discussed.