Teak Plantation Phenology Changes and its Relationships to Climate Variability in Lampang Province, North of Thailand

The study aimed to investigate changes in teak plantation phenology in Lampang Province, North of Thailand, and its relationships to climate variability. The study used time series of Normalized Difference Vegetation Index (NDVI) extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) from 2009 to 2012 to investigate changes in teak plantation phenology. The NDVI was validated by Leaf Area Index (LAI) and the negative logarithm of the ratio of daily downward solar radiation on the forest floor to that above the canopy (NLR). The results showed that NDVI was significantly correlated with LAI (r=0.81) and NLR (r=0.77). Analysis of phenology metrics revealed that the length of the growing season ranged between 264-324 days, starting from March to May and ending in January to March of the following year. In 2010, the starting of the season was delayed, and the length of the season was shorter than other years. NDVI was negatively correlated to maximum temperature (r = -0.85, p<0.0001), whereas positively correlated to precipitation (r=0.51, p<0.0001) during the period from April to May. During the end of the season (October to December), NDVI had significant and positive relationships with minimum temperature and precipitation (r=0.81, r=0.64), respectively. The study demonstrated that NDVI extracted from satellite is able to capture the teak plantation phenology and provide spatial and temporal information for long-term monitoring. The significant correlation between NDVI and climate factors in this study implies that future variability in meteorological variables under climate change would affect the forest ecosystem. The study area, Lampang Province, is located in Northern Thailand, with an area of 12,534 square kilometers. The province is situated on a plateau with an altitude of 268.80 meters above sea level. The average temperature in summer and winter is 41.50C and 10.50C, respectively, and the average annual rainfall is 1,098 mm. Teak plantation is widely distributed in Lampang, making it an ideal location for studying teak plantation phenology. The researchers used MODIS data, meteorological records, and observation data to analyze the relationships between teak plantation phenology and climate variability. The MODIS data provided information on surface reflectance, which was used to calculate NDVI. The meteorological records provided data on maximum and minimum temperature, accumulated precipitation, and other climate variables. The observation data was used to validate the NDVI pattern. The study found that the teak plantation phenology in Lampang Province is sensitive to climate variability, with changes in temperature and precipitation affecting the growing season and NDVI values. The study suggests that long-term monitoring of teak plantation phenology is essential to understand the impacts of climate change on forest ecosystems in Thailand.