Phenological studies in Australia: potential application in historical and future climate analysis

Phenological observations of eucalypts (Myrtaceae) were undertaken in four Australian states (New South Wales, Queensland, Victoria, and Western Australia) from the late 1920s until the early 1980s, by the respective State Forest Commissions. Unfortunately, few records have survived. For Victoria, surviving records encompass 42 forest districts, covering from less than 2 years to 42 years, and approximately 50 species. This paper concentrates on the flowering of four competing species (Eucalyptus leucoxylon, E. microcarpa, E. polyanthemos, and E. tricarpa) over 23 years (1940–62) from Maryborough, Victoria, recorded on a monthly basis by one observer over the period. This study represents one of the first attempts to utilize Australian phenological data to detect responses to climate change. There were no significant trends (P = 0.05) over time in the mean flowering commencement date. Forward stepwise regression found a significant relationship between temperature and flowering commencement in two species (E. leucoxylon: R2 = 0.42, P < 0.01; E. polyanthemos: R2 = 0.47, P = 0.02). Rainfall also had a significant influence on flowering commencement in E. tricarpa (R2 = 0.60, P < 0.01), E. leucoxylon (R2 = 0.43, P = 0.02) and E. polyanthemos (R2 = 0.24, P < 0.01). The combination of temperature and rainfall (with temperature exerting the greatest influence), however, was significant for all species and had the most explanatory power (ranging from R2 = 0.74 to 0.85, P < 0.01). Overall, in response to predicted increases in temperature and summer rainfall, E. leucoxylon and E. tricarpa would commence flowering later. In E. polyanthemos and E. microcarpa, increased temperature and rainfall will result in an earlier onset of flowering. Copyright © 2002 Royal Meteorological Society.