Contrasting Rhizospheric and Heterotrophic Components of Soil Respiration during Growing and Non-Growing Seasons in a Temperate Deciduous Forest

Abstract

The contributions of heterotrophic respiration (RH) to total soil respiration (RS) for the non-growing season, growing season, and annual period are 84.8%, 60.7%, and 63.3%, respectively.Few studies have partitioned RS into its rhizospheric (RR) and heterotrophic components throughout the year in northern forest ecosystems. Our objectives were to quantify the contributions of non-growing season and heterotrophic respiration. We conducted a trenching experiment to quantify RR and RH in a temperate deciduous forest in Northeast China over two years using chamber methods. Temperature sensitivities (Q10) for RS and for RH were both much higher in the non-growing season (November to April) than those in the growing season. The Q10 for RS was higher than Q10 for RH in both seasons, indicating a higher temperature sensitivity of roots versus microorganisms. Mean non-growing season RS, RH, and RR for the two years were 94, 79 and 14 g carbon (C) m−2, respectively, which contributed 10.8%, 14.5%, and 4.5% to the corresponding annual fluxes (869, 547 and 321 g C m−2 year−1, respectively). The contributions of RH to RS for the non-growing season, growing season, and annual period were 84.8%, 60.7%, and 63.3%, respectively. Using the same contribution of non-growing season RS to annual RS, to scale growing season measurements, to the annual scale would introduce significant biases on annual RH (−34 g C m−2 yr−1 or −6%) and RR (16 g C m−2 yr−1 or 5%).We concluded that it was important to take non-growing season measurements in terms of accurately partitioning RS components in northern forests.

Keywords

• heterotrophic respiration
• autotrophic respiration
• temperature sensitivity
• non-growing season
• temperate forest