Abstract: This work investigated the phenology of Parah tree
(Elateriospermum tapos) using the General Purpose Atmosphere
Plant Soil Simulator (GAPS model) to determine the amount of Plant
Available Water (PAW) in the soil. We found the correlation
between PAW and the timing of budburst and flower burst at Khao
Nan National Park, Nakhon Si Thammarat, Thailand. PAW from the
GAPS model can be used as an indicator of soil water stress. The low
amount of PAW may lead to leaf shedding in Parah trees.