Effects of fertilization on soil respiration, heterotrophic respiration, and temperature sensitivity in an oil tea plantation

As the largest carbon pool of terrestrial ecosystems, soils constitute important sources and sinks of global CO2 balance. Soil respiration is an important pathway of carbon fluxes between the atmosphere and terrestrial ecosystems. Further, soil respiration can also influence terrestrial carbon cycling through climate feedbacks, specifically temperature sensitivity (Q10). Oil tea (Camellia oleifera) is an important native woody oil crop, and has been widely developed in south China in recent years. High-level fertilization has been widely adopted to increase growth of oil tea trees and maintain soil fertility. In this study, the effects of fertilization on soil respiration, heterotrophic respiration and temperature sensitivity in an oil tea plantation were examined. Static chambers and gas chromatography were used to collect and analyze gas samples. To differentiate soil respiration and soil heterotrophic respiration, the trenching method was used. There were four treatments in this study: oil tea plots with fertilization (OF), oil tea plots without fertilization (CK), trenching plots with fertilization (OF-T), and trenching plots without fertilization (CK-T). The results showed that fertilization had no significant effects on either soil respiration or heterotrophic respiration. Soil CO2 effluxes in different treatments (OF, CK, OF-T, CK-T) were 77.91±2.59, 73.71±0.97, 66.82±1.02, and 66.84±3.94 mg C m-2 h-1, respectively. The temperature sensitivity of soil CO2 effluxes was 1.77±0.01, 1.75±0.03, 1.96±0.01, 1.79±0.03 in OF, CK, OF-T, and CK-T respectively. Fertilization significantly increased temperature sensitivity of soil heterotrophic respiration, with the Q10 values in the OF-T plots significantly higher than those in the CK-T plots. In addition, fertilization significantly increased soil NH+4 -N and NO-3 -N contents in the surface layer (0-10cm). We also found significant linear relationships between the Q10 of soil CO2 effluxes and soil NH+4 -N, as well as NO-3 -N contents. Our findings may provide basic data for greenhouse gas inventories and understanding their responses to climate change in a typical cash crop plantation in south China.