Ecological Indicators 56 (2015) 6–14 Contents lists available at ScienceDirect Ecological Indicators jo ur nal ho me page: www.elsevier.com/locate/ ecolind Management intensification effects on autotrophic and heterotrophic soil respiration in subtropical grasslands Julius B. Adewopo a , Maria L. Silveira a,∗ , Sutie Xu a , Stefan Gerber b , Lynn E. Sollenberger c , Tim Martin d a University of Florida, Range Cattle Research and Education Center, 3401 Experiment Station, Ona, FL 33865, USA b University of Florida, Soil and Water Science Department, 2185 McCarty Hall A, Gainesville, FL 32611, USA c University of Florida, Agronomy Department, Gainesville, FL 32611, USA d University of Florida, School of Forest Resources and Conservation, 359 Newins-Ziegler Hall, Gainesville, FL 32611, USA a r t i c l e i n f o Article history: Received 9 October 2014 Received in revised form 17 March 2015 Accepted 20 March 2015 Keywords: Soil carbon Spodosol Grazing land a b s t r a c t Sustainable management of grassland ecosystems for improved productivity can enhance their poten- tial to sequester atmospheric CO 2 in the soil. However, land-use management influences the quantity and quality of carbon (C) inputs which may, in turn, affect microbial activity and soil C decomposition rates. Understanding the potential changes in magnitude of soil C loss through respiration is critical for a comprehensive assessment of land-use conversion and grassland management impacts on terrestrial C dynamics. Thus, this study was designed to assess the effect of land-use management intensification on soil respiration in subtropical grasslands. Experimental sites consisted of a gradient of management intensities ranging from native rangeland (lowest), silvopasture (intermediate), to sown pasture (high- est). Increasing management intensity from native rangeland to sown pasture elevated soil respiration. There was a significant effect of ‘season vs. management’ interaction on total soil respiration (R S ), with greater increases in R S from summer to winter in sown pasture (∼200%) compared to native rangeland and silvopasture (∼91%). The temperature sensitivity of R S and heterotrophic soil respiration (R H ) increased with management intensification, with a highest Q 10 of 1.55 and 2.29, in sown pasture, compared to Q 10 values of 1.09 and 1.48 in native rangelands. These results suggested that potential increases in soil C stock with intensification may be susceptible to faster turnover under warming climate scenarios. Improved resilience (and longer residence) of additionally sequestered soil C after intensification may be crucial for long-term ecological resilience, especially with changing climatic conditions. These findings are relevant for sustainable grassland management, especially within subtropical ecoregions, and add to the under- standing of changes that may occur in rates of soil C losses as native grasslands are converted to more productive grassland ecosystems. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Grassland ecosystems constitute about 40% of the global land area and play a significant role in the global terrestrial C cycle (Knapp et al., 1998; Wang and Fang, 2009). Due to the relatively high C sequestration rates (mainly associated with below-ground C pools) and extensive area, grasslands are recognized for their Abbreviations: RS, total soil respiration; R A , autotrophic soil respiration; RH, heterotrophic soil respiration; S Moist , soil volumetric moisture content; STemp, soil temperature; SOC, soil organic carbon. ∗ Corresponding author. Tel.: +1 863 735 1314; fax: +1 863 735 1930. E-mail address: mlas@ufl.edu (M.L. Silveira). great potential as net sink for atmospheric CO 2 and climate change regulator (Follett and Reed, 2010; U.S. EPA, 2012). Marginal changes in soil C sequestration rates in grasslands can have significant impacts on atmospheric CO 2 concentrations (Follett and Reed, 2010). Globally, soils contain 1500 Pg C which is twice the amount of atmospheric C pool (Schlesinger and Andrews, 2000), with grasslands containing ∼12% of the overall terrestrial soil C pool (Schlesinger, 1977). However, grassland management can alter the quantity and quality of litter inputs and, subsequently, impact the amounts and stability of C stored in the soil (Conant et al., 2001, 2004; Dubeux et al., 2006). For instance, in the USA grassland intensification, mainly through the conversion of native grass- lands into more intensively managed ecosystems, has fostered http://dx.doi.org/10.1016/j.ecolind.2015.03.025 1470-160X/© 2015 Elsevier Ltd. All rights reserved.