Tree water relations study in Sal (Shorea robusta Gaertn.) forest in Kumaon Central Himalaya.

This study was carried out at 500 m elevation in a pure forest of Sal (Shor ea robusta) (trees generally above 25 m in height) in Kumaun region of Cent ral Himalaya (between 29 degrees 8' latitude and 79 degrees 20' longitude) where the average rainfall is approximately 1800 mm of which 80% occurs in the monsoon period to determine the seasonal changes in soil water potentia l tree water potential and leaf conductance. Seasonal fluctuations in soil water potential were not reflected in predawn tree water potential and leaf conductance. However, leaf conductance declined sharply during the peak su mmer drought as a result of stomatal closure. No significant correlation (r = 0.148i) existed between soil water potential (at 60 cm depth) and predaw n tree water potential. The relatively high values of leaf conductance thro ughout the study (except summers) supports the fact that S. robusta seems t o keep its stomata open throughout the year, carrying out photosynthesis in all seasons las leaf conductance is assumed to be related to photosynthesi s). However, the species different in degree of fall in leaf conductance in response to adverse climatic conditions showing a significant decrease in leaf conductance during the peak summer time of year 2, and winters of year 1.