This study looks at the growth of celery-top pine in mixed forest stands in the Warra region of southern Tasmania. An effective way of aging celery-top pine saplings and a greater understanding of the biometry and distribution characteristics in mixed forests of varying age were investigated.
The growth patterns of celery-top pine saplings were found to be different in different-aged stands of mixed forest. The density of saplings was greatest in an open small gap (an abandoned roadline of approximately 5 ha) of newly regenerating forest that afforded some protection from desiccation but did not over-shade the saplings. There were less saplings per hectare in a 1934 wildfire regrowth site and even less again at an oldgrowth site (greater than 360 years of age). The mean annual growth rate in both height and diameter was greatest also at the young regenerating site and least in the oldgrowth forest. In the oldgrowth forest beneath a closed canopy, saplings were typically suppressed. Despite this, there was continual recruitment of seedlings and survival of saplings under heavily shaded conditions, mostly on elevated sites such as mossy logs.
A tree age – diameter relationship was shown however there is significant variability of growth rate in this species and between tree populations at different elevations. From these results the average time required to obtain a sawlog of 30cm dbh would require a rotation of 145 years; 40 cm, 215 years; 50 cm, 305 years and 60 cm, 470 years. The high value uses of this timber such as boat building require large diameter trees and hence longer rotations, however markets for smaller logs do exist, such as flooring, craft and furniture making. Silviculture that produces high value timber (long rotation) is desirable for this species.
Future management of mixed forests may include a proportion of land for special species timber production. The diversity of silviculture available, from small group selection systems to aggregated retention, allows for longer rotations to be implemented within a working forest mosaic. Information such as age – diameter relationships for the special species timbers will help forest management planners in selecting rotation age for a multitude of practical outcomes.
The results of this study are based on a few forests of the Warra area in southern Tasmania. There was limited replication of sites, however, the results build on past studies in the southern forests by adding new information and consolidation to past conclusions. Further research is needed to test the application these conclusions in a broader context in Tasmania.
