•Australian provenances of Avicennia marina developed in isolation of each other.•Differences between provenances are evolutionary adaptations due to site conditions.•Pronounced differences between ...provenances offer choices for planting or breeding.
Avicennia marina is the most widely distributed of all mangrove species. This study examined phenotypic characteristics of seedlings raised from seven provenances of the species widely spread around the Australian coast from tropical to temperate regions. Seedlings were grown together for 18 months in a glasshouse at Lismore in sub-tropical eastern Australia. The provenances displayed differences in propagule and seedling size and seedling leaf characteristics that could be related to geographic occurrence but showed no distinct geographical cline. Consistent with other phenotypic and genetic studies of A. marina, phenotypic variation was mainly between provenances and between individuals across the entire population, rather than between individuals within any one provenance. The results suggested that provenance populations may have developed individually, separated by geographical barriers. If it can be assumed that characteristics observed in the present trial are likely to expressed by provenances when grown away from their natural environment, the present work has identified provenances that might be explored to find desirable individuals with phenotypes that might have value in mangrove planting or breeding programmes.
Growth behaviour of the relatively shade-intolerant species Eucalyptus dunnii and the rather more shade-tolerant Corymbia citriodora was considered during several growth periods over 8-14 years of ...age in experimental plantation monoculture in subtropical New South Wales. Larger trees dominated growth in any stand; this was consistent with the principle that inter-tree competition in such forests is for light and is asymmetric in that larger trees shade smaller trees but the reverse does not occur. Once competition was established, competition-induced mortality of C. citriodora was less than that of E. dunnii. A model relating tree diameter growth rate to tree diameter, competitive position in the stand and stand basal area was developed. The model showed that smaller, hence partially shaded, trees in stands of C. citriodora were better able to maintain their growth rates than equivalent trees in stands of E. dunnii. It is hypothesised that this reflects the greater shade tolerance of C. citriodora. This pattern of growth led to a more even distribution of tree size classes across the stand in the more shade-tolerant species.
PDF