dry dipterocarp forest for 181 days, we found that the average soil CO2 efflux were 4.8±2.3 (n=12,919) and 1.9±0.8 (n=15,626) μmol m-2s-1, respectively. Their accumulative soil CO2 emissions were 6.69 and 2.62 kg CO2 m-2 y-1, respectively. The Rs accounted for 70.87% and 44.56% of the Re, respectively. Rs in dry dipterocarp forest and mixed deciduous forest were strongly correlated to soil moisture (p<0.01). In addition, Rs in mixed deciduous forest was about 2.6 times higher than in dry dipterocarp forest. This may indicate more active soil and forest floor processes. In addition, we found that there were higher temporal variations of soil CO2 fluxes at mixed deciduous forest when compared to dry dipterocarp forest. This may be attributed to higher variations in rainfall which caused higher variations in soil moisture and in soil respiration. ACKNOWLEDGMENT This research was financially supported by Center of Excellence for The Joint Graduate School of Energy and Environment (JGSEE), Center of Excellence on Energy Technology and Environment (PERDO) and the National Research University Project (NRU) of Thailand’s Office of the Higher Education Commission. REFERENCES 1 (2015) The United Nationswebsite. Online. Available: http://www.un.org/ sustainabledevelopment /biodiversity/ 2 L. Yiqi, and Z. Xuhui, Soil Respiration and the Environment, USA: Elsevier Academic Press, 2006. 3 V. Le Dantec, D. Epron, and E. Dufrêne, “So i l CO2 e ff l u x i n beech f o r e s t : Comparison of two closed dynamic systems”, Plant Soil, vol.214 (1-2), pp. 125-132, Aug. 1999. 4 T. Hirano, H. Setoyama, Y. Tanaka, and D. Relationships between Soil Respiration (Rs) with Moisture and Temperature in Soil Daily mean soil respiration rates (or soil CO2 effluxes) in dry dipterocarp forest and mixed deciduous forest were strongly correlated to soil moisture (r2=0.60, p<0.01, n= 150 and r2=0.75, p<0.01, n=136, respectively) but there was no clear relationships to soil temperatures as shown in Fig.2 c-d. Although soil respiration rates did not relate to soil temperature in seasonal scales, it may relate in diurnal scales (or 24-hour scales). These results indicated that soil respirations in two forests at seasonal scales were mainly controlled by soil moistures, similar to those reported by others 2, 5, 8. Aside from moisture and temperature in soil, controlling factors of soil respirations were substrate supply and ecosystem productivity, soil pH, soil oxygen, nitrogen, and soil texture 2. In this study, soil texture in mixed deciduous forest at MKL site had higher soil water- holding capacity than dry dipterocarp forest at DFR site which were a sandy clay loam soil and a loamy sand soil, respectively. Soil texture could influence soil respiration through its effects on soil porosity and moisture. In addition, above ground litterfall is another important factor influencing the CO2 flux from the forest ecosystems 2. In this study, the litterfall production in a mixed deciduous forest at MKL site (8.91 ton ha-1 y-1 of dry weight, measurement between June 2003 and May 2005 14) was higher than in the dry dipterocarp forest at DFR site (6.42 ton ha-1 y-1 of dry weight, measurement in 2009 15). Therefore soil respiration (Rs) and their contributions to ecosystem respiration (Re) from the mixed deciduous forest were higher than from the dry dipterocarp forest. IV. CONCLUSIONS Measuring soil CO2 by using CO2 profile gradientin mixed deciduous forest and Proceedings of the International Conference on Climate Change, Biodiversity and Ecosystem Services for the 157 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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