Thus, El Niño induced early and shortened the litter fall period. The gross primary production (GPP) was considerably decreased during El Niño years compared to those during the normal year. The net ecosystem exchange (NEE) were -26.34 to -309.53 gC m-2 during El Niño and -327.89 to -391.25 gC m-2 during the normal years. The high NEE and low GPP/RE indicate the net carbon loss during the El Niño. The less rainfall for extended period of time, low soil moisture and high soil temperature are the important factors controlling litter fall timing and carbon exchange. From these results it could be concluded that the extreme climatic events such as El Niño could induce early litter fall and reduce the potential of carbon uptake. Keywords: Litter fall, carbon exchange, El Niño, secondary dry dipterocarp forest I. INTRODUCTION Extreme climate variability such as El Niño has been found in higher frequency due to climate change 1. As atmospheric carbon dioxide concentration (Ca) is the largest contributor to global warming and climate change, forest ecosystems play an important role in controlling Ca through tree photosynthesis and respiration 2. Thus understanding the response of forest to climate extremes are important for both mitigation of atmospheric CO2 and adaptation to climate change of the forest 3. The importance of managing sustainable forest under climate change is highlighted as one of the 2030 Agendas for Sustainable Development and Sustainable Development Goals (SDG15) 4. El Niño is the phenomenon with apparent increasing sea surface temperature (SST) in tropical Pacific Ocean to west coast of South America that links to atmospheric major change by transportation of heat in ocean into the atmosphere. During the events, the rainfall location is shifted and drier conditions occurred in South eastern regions. The last El Niño occurred during 2009-2010 5, 6, 7 and since February 2015 we have been in the period of one of the strongest El Niño. In Thailand, a new maximum temperature of 44.6°C has been recorded 8. Moreover, long- term trends and variability of precipitation during 1955-2014 illustrated that Thailand had a lower amount of precipitation during El Niño years 9. The El Niño affects carbon exchange of a forest because the changing rainfall pattern and rising temperature over forests is tightly associated with CO2 uptake. Moreover, the El Niño also influences forest fires that enhances the release of massive CO2 into atmosphere 6. Although the understanding of carbon exchange and how increasing temperature affects its process are relatively well understood in the temperate forest, our knowledge in tropical dry deciduous forest is poor 10.In the tropics, 48.5% of seasonally dry tropical forests have been cleared for agriculture or other land uses and this causes the expansion of secondary forests 11, 12. In the tropical to subtropical regions of South- east Asia, a dry dipterocarp forest is one of the dominant forest types with unique forest characteristics and high diversity of several endemic species 13. Understanding carbon dynamics and the relationship with climate extreme is thus crucial. The study of biological cycle timing and its relationship to climate factors that is called “phenology” is crucial for understanding of carbon dynamics in forest 14, 15. The phenological shift might be attributed to climate change. More work is thus needed to know how a phenological response is being affected by climate change 14. This study investigated the phenological shift through 304 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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