Effects of Atmospheric Factors on Parah (Elateriospermum tapos) Phenology in Southern Thailand

Leaf and flower phenology of Parah trees, Elateriospermum tapos a canopy species, was studied at Khao Nan National Park, in southern Thailand in 2007 and 2008. Within this national park, the study site is located at the Parah Park Ranger Station, latitude 8.86543 ° N and longitude 99.62230 ° E. Maximum and minimum temperatures, precipitation and relative humidity, were among the atmospheric parameters measured. In 2007, leaf bud burst occurred from 13 February to 24 March, for a period of 40 days. The maximum bud burst per day occurred on 1 March 2007. Flower burst occurred from 15 February to 30 March 2007 for a period of 44 days. The maximum flower burst per day occurred on 8 March 2007. In 2008, leaf bud burst and flower burst occurred at the same time from 2 January to 31 March for a period of 90 days. The maximum bud burst and flower burst per day occurred on 4 March 2008. Mean values of atmospheric parameters measured at Parah forest during bud burst and flower burst from January to March were similar for both years except that total precipitation was lower in 2007, 271 mm versus 294 mm in 2008. In 2007, bud burst occurred ahead of flower burst, when there was a clear drought period with the total amount of precipitation of 2.75 mm in February. On the other hand in 2008, leaf bud burst and flower burst were synchronous and the total amount of precipitation was 74.86 mm in February. Bud burst and flowering burst duration was twice as long in 2008 than in 2007. This longer duration could be due to the fact that precipitation in 2008 occurred during the beginning of leaf bud burst and flower burst causing an overall delay of bud burst and flower burst. These results indicate that timing and amount of precipitation play a major role in Parah phenology in southern Thailand.