Seasonal variation of soil respiration rates in a secondary forest and agroforestry systems Kikang Bae • Don Koo Lee • Timothy J. Fahey • Soo Young Woo • Amos K. Quaye • Yong-Kwon Lee Received: 18 October 2011 / Accepted: 21 May 2012 / Published online: 24 June 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Agroforestry systems are widely practiced in tropical forests to recover degraded and deforested areas and also to balance the global carbon budget. However, our understanding of difference in soil respiration rates between agroforestry and natural forest systems is very limited. This study compared the seasonal variations in soil respiration rates in relation to fine root biomass, microbial biomass, and soil organic carbon between a secondary forest and two agroforestry systems dominated by Gmelina arborea and Dipterocarps in the Philippines during the dry and the wet seasons. The secondary forest had significantly higher (p \ 0.05) soil respiration rate, fine root biomass and soil organic matter than the agroforestry systems in the dry season. However, in the wet season, soil respiration and soil organic matter in the G. arborea dominated agroforestry system were as high as in the secondary forest. Whereas soil respiration was gener- ally higher in the wet than in the dry season, there were no differences in fine root biomass, microbial biomass and soil organic matter between the two seasons. Soil respiration rate correlated positively and significantly with fine root biomass, microbial biomass, and soil organic C in all three sites. The results of this study indicate, to some degree, that different land use management practices have different effects on fine root biomass, microbial biomass and soil organic C which may affect soil respiration as well. Therefore, when introducing agroforestry system, a proper choice of species and management techniques which are similar to natural forest is recommended. Keywords Agroforestry system Á Secondary forest Á Soil respiration Á Fine root biomass Á Microbial biomass Á Gmelina arborea and Dipterocarps Introduction Tropical forests contain approximately 37 % of the global terrestrial carbon pool in their vegetation and soils (Dixon et al. 1994). Because of their dominant K. Bae Á A. K. Quaye Department of Forest and Natural Resources Management, SUNY College of Environmental Science and Forestry, Syracuse, NY 13210, USA D. K. Lee Department of Forest Science, Seoul National University, Seoul 151-742, Korea T. J. Fahey Department of Natural Resources, Cornell University, Ithaca, NY 14853, USA S. Y. Woo Department of Environmental Horticulture, University of Seoul, Seoul 130-743, Republic of Korea Y.-K. Lee (&) Korea Forest Service, Government Complex-Daejeon, Bldg 1, 189 Cheongsa-ro, Seo-gu, Daejeon 302-701, Republic of Korea e-mail: shorea@korea.kr 123 Agroforest Syst (2013) 87:131–139 DOI 10.1007/s10457-012-9530-8