A comparison of long-term flowering patterns of Box-Ironbark species in Havelock and Rushworth forests

Long-term records were used to compare the flowering of Eucalyptus microcarpa, E. melliodora, E. leucoxylon, E. polyanthemos and E. tricarpa between Havelock Forest (1940-1971) and Rushworth District (1945-1970). Indices were developed and used to compare the mean monthly annual flowering patterns (e.g., mean duration, annual flowering success) between the two locations. Additionally, the long-term flowering pattern of each species between 1945 and 1970 was examined for concordance. Results of the analysis suggest that despite the similarity of species composition there are differences in flowering behaviour. Flowering always commences and peaks at Rushworth prior to Havelock. The earlier commencement is influenced by Rushworth's slightly warmer climate. There are also similarities. Only the flowering duration for E. melliodora was significantly different (P < 0.001). The annual flowering success (defined as the proportion of years when flowering occurred) was similar between both sites, except for E. polyanthemos, which had more reliable flowering at Havelock, flowering on average in 9 out of 10 years (compared to 7 out of 10 for Rushworth). E. tricarpa, E. leucoxylon and E. microcarpa were identified as concordant species, and E. polyanthemos and E. melliodora as discordant. The combination of results (indices and concordancy) suggests that three species (E. tricarpa, E. leucoxylon and E. microcarpa) occupy a similar temporal niche at the different sites (i.e., they flower contemporaneously), whilst the remaining two (E. polyanthemos and E. melliodora) species do not. The results provide a useful baseline description of the flowering behaviour of two important Box-Ironbark forest sites in Victoria, and may assist in understanding the migration of nectar-dependent species at the landscape scale.