Climate change affecting off-season longan (Dimocarpus longan Lour.) production at alluvial plains of Thailand

Off-season longan is an important commercial fruit crop at the alluvial plains of the central region in Thailand such as Sumutsakhon and Ratchaburi provinces. During the high demand season in late December and early February, flowers' growth has to encounter great loss from climate changes namely “hot wind”. In order to monitor and evaluate the effect of “hot wind”, on flowers, the present experiment was undertaken in a longan orchard at Ban Phaeo districts, Samutsakhon. The results revealed that “hot wind”, occurring on July 11-12, 2017, has complex characteristics. There was a sudden change in microclimate and wind from the northwestern (300-330° in a clockwise direction from the North) was detected prior to a suddenly increased air temperature, decreased relative humidity, increased VPD (vapor-pressure deficit), while the soil moisture content decreased. After that damage in flowers was observed, especially in young inflorescences with a size of below 5 cm long, and thus influenced their off-season productivity. The major evidence occurred during July to September. Significant decrease in vegetative growth of new flush and young leaves occurred, and then the transformation of flower buds to vegetative buds was about 80%. New flushes stopped their growth, after that some damaged flower buds showed the transformation returning to vegetative phase. The above information could be a key playing an important role in establishment of performance or strategies to alleviate the “hot wind” in the future.