Seasonal and diurnal dynamics of soil respiration fluxes in two typical forests on the semiarid Loess Plateau of China: Temperature sensitivities of autotrophs and heterotrophs and analyses of integrated driving factors Wei-Yu Shi a, c, e , Jian-Guo Zhang a, e , Mei-Jie Yan a, b , Norikazu Yamanaka d , Sheng Du a, b, * a State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China b Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China c State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, Shaanxi 710075, China d Arid Land Research Center, Tottori University, Tottori 680-0001, Japan e Graduate University of Chinese Academy of Sciences, Beijing 100049, China article info Article history: Received 24 March 2012 Received in revised form 15 April 2012 Accepted 16 April 2012 Available online 8 May 2012 Keywords: Autotrophic respiration CO 2 efflux Heterotrophic respiration Q 10 Semiarid forest abstract Partitioning of total soil respiration (R T ) into autotrophic (R A ) and heterotrophic (R H ) components was undertaken in two typical (natural and artificial) forests on the temperate, semiarid Loess Plateau of China, to determine and compare temperature sensitivities between the two components. The natural secondary forest was dominated by oak (Quercus liaotungensis) while the artificial forest was a plantation of black locust (Robinia pseudoacacia). Soil CO 2 efflux and different abiotic and biotic factors were measured during dormant and growing seasons. Temperature sensitivities of soil respiration compo- nents were investigated using the Q 10 function at diurnal and seasonal scales. The temperature sensi- tivities of autotrophic (R A ) and heterotrophic (R H ) respiration varied with the time scales (daily, seasonal, or annual) of the investigation, and were affected by other biological and environmental factors. The largest contribution of R A to R T was 46% in the oak forest and 60% in the black locust plantation during the growing season. During the dormant season it was as low as 12% in the oak forest and 6% in the black locust plantation. The Q 10 of R A for the black locust plantation was higher than for the oak forest during the growing season, but was lower during the dormant season. The Q 10 of R A in both forests was higher than that of R H at both diurnal and seasonal scales. Multiple regression analyses suggested that photo- synthesis is an important parameter in soil respiration studies and that a multiple-factor model may be more suitable during the annual periods. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Soil respiration is a significant component of the global carbon cycle, and is likely to affect global warming (Schlesinger and Andrews, 2000). Warming resulting from increasing greenhouse gases in the atmosphere has increased earth’s surface temperature by 0.67  C since 1850, and the temperature is expected to increase by another 1.1e6.4  C by the end of this century (IPCC, 2007). It was estimated that a warming of 0.03  C per year will increase soil respiration, producing a net release of an additional 60 Pg C from soil to atmosphere between 1990 and 2050 (Jenkinson et al., 1991). Forests play a major role as global reservoirs of soil carbon (Davidson and Janssens, 2006; Griffis et al., 2003, 2004; Luyssaert et al., 2008; Piao et al., 2009). Many measurements of soil respi- ration have been carried out in diverse forests around the world (Davidson et al., 2000; Falk et al., 2005; Gaumont-Guay et al., 2006a; Hashimoto et al., 2009; Longdoz et al., 2000; Zimmermann et al., 2010). Diurnal and seasonal patterns of soil respiration have been common topics in such investigations either for forests or other ecosystems. However, information on factors that drive soil respiration in forests remains limited. These include autotrophic respiration (R A ) from roots and rhizosphere, and a heterotrophic component (R H ) from litter and soil organic matter (SOM) decomposition (Kuzyakov, 2006). Mechanisms behind the patterns based on soil CO 2 parti- tioning have not been intensively studied, especially for the * Corresponding author. State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China. Tel.: þ86 29 87012411; fax: þ86 29 87012210. E-mail address: shengdu@ms.iswc.ac.cn (S. Du). Contents lists available at SciVerse ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio 0038-0717/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.soilbio.2012.04.020 Soil Biology & Biochemistry 52 (2012) 99e107