B. Phenological Metrics of Teak Plantation Based on the phenological metrics extracted from TIMESAT program, SOSs varied among these three years, which started at 96, 152 and 80 day of year (DOY) in 2009, 2010 and 2011, respectively (Table 1). SOS in 2010 was delayed compared to other years. El Niño in 2010 may contribute to this change in phenology (Fig.3, 4). relationship with minimum temperature and precipitation (r=0.81 and r=0.64, p<0.0001, respectively) (Fig.8). These results imply that growing season might start when temperature decreases with precipitation increases during April to May. Thus, the results suggest that climate variables such as precipitation and temperature were the main controlling factors for NDVI, corresponding to plant phenology. However, more analysis on this relationship is needed to be conducted at teak plantations with different topographic and climate conditions, in order to test the hypothesis that precipitation and temperature control teak phenology and obtain further understanding on phenology and climate variation, especially under the context of climate changes. IV. CONCLUSIONS In this study, four years time series of MODIS NDVI image were processed with cloud removal in order to investigate the phenological variations driven by climate variability. From the results, we concluded that: - Processed MODIS NDVI was able to capture the changes of phenology of a teak plantation in this study. - The SOS of teak plantation was delayed in El Nino year, with significant effects on the variations of LOS during four years in this study. - Teak forests NDVI have a stronger relationship to maximum and minimum temperature than precipitation. - Further analysis on phenological metrics (such as comparison with photographs and field sensor data) in relation to meteorological variables is required for further understanding of the relationships between teak plantation phenology and climate variation, especially under the context of climate change. Table 1 Phenological Metrics of Teak Plantation Period 2009-2012 Year SOS (DOY) EOS (DOY) LOS (Day) 2009-2010 96 (April) 60 (March) 324 days 2010-2011 152 (May) 63 (March) 264 days 2011-2012 80 (March) 22 (Jan) 295 days On the other hand, EOSs in 2009, 2010 and 2011 were on 60, 63 and 22 DOY, respectively. As a result of the changes in SOS and EOS, LOS in 2010 with El Niño was about 264 days; shorter than in 2009 and 2011 by about 60 and 31 days, respectively. In general, analysis from phenology metrics shows that LOS of teak plantation ranged between 264 and 324 days. SOS occurred from March to May while EOS occurred in January or March of the following year. The patterns of teak forest phenology extracted from MODIS NDVI are consistent with those previously reported. Yoshifuji et al. 14 concluded that canopy duration of tropical seasonal forest is about 300-320 days. C. NDVI and Its Response to Climate Variables The Spearman correlation coefficient between NDVI (8 day period, 250 m resolution) and climate factors was calculated. Results indicate that NDVI was significantly and negatively correlated with maximum temperature (r=-0.85, p<0.0001), positively correlated with precipitation (r=0.51, p<0.0001) in the period of April-May (Fig.7). During EOS (October to December), NDVI had a significant and positive 278 Proceedings of the International Conference on Climate Change, Biodiversity and Ecosystem Services for the Sustainable Development Goals (SDGs): Policy and Practice 27-29 June 2016, Cha-am, Phetchaburi, Thailand
Proceedings of International Conference on Climate Change, Biodiversity and Ecosystem Services for the Sustainable Development Goals : Policy and Practice 27-29 June 2016 at the Sirindhorn International Environmental Park, Cha-am, Phetchaburi, Thailand
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