Climate variability in Tasmania based on dendroclimatic studies of Lagarostrobos Franklinii

Four new Huon pine ring-width chronologies complete a seven-chronology network from western Tasmania, and span an elevationial range from 200 to 950 metres above sea level. The new chronologies are from relict stands in the Frenchmans Cap area of western Tasmania, and range from 451 to 1925 years in length. Two are from rare subalpine sites above 800 metres, and two are from 550 and 700 metres, respectively. The sample depth in the earliest portion of the 950 metre-high chronology from Mt. Read, from which a 2792 year reconstruction of warm season temperature was previously derived, is substantially improved through the inclusion of several subfossil logs. The crossdating of ring sequences, and the climatic responses of the three earlier chronologies is confirmed. The chronology network enables a more complete analysis of Huon pine's climatic response throughout much of its latitudinal and elevational range. An improved temperature time-series (a composite of 9 coastal or near-coastal records surrounding Tasmania) is used for the calibration and verification of the climate response. Response function analyses clearly define the seasonal influence of temperature and preciptiation on Huon pine growth. An elevation dependence of the temperature response is revealed, reflecting the stratification of the climate in mountainous western Tasmania. This vertical structure is due to the effects of orographic uplift of westerly and southwesterly airflow, combined with a persistent subsidence-inversion layer above 700 metres. Apparent changes in the mean height of a persistent cloud zone (from 820 - 930 metres) are coincident with recent warming in the region. These changes appear to be associated with a poleward migration of the mean latitude of the Subtropical High Pressure Belt, and slackened zonal circulation. New reconstructions of temperature help define the regional extent of the climate signal from this region. Several unique qualities make Huon pine a valuable resource for palaeoenvironmental research, in particular the tremendous preservation properties of its wood which can survive for many thousands of years. The abundance of subfossil logs at most sites allows for great sample depth through time. Very long ring sequences allow for the preservation of low-frequency signals in the chronology indices, normally not afforded by dendroclimatological reconstructions. Such low-frequency signals are critical for the detection of natural climate variability on timescales of centuries to millennia, and allow for a more accurate assessment of recent trends in regional climate.