Subke, J.-A., N. Voke, V. Leronni, M. Garnett and P. Ineson (2010). Dynamics and pathways of autotrophic and heterotrophic soil CO2 efflux revealed by forest girdling. Journal of Ecology, online 7 October.
Quantifying pathways and temporal dynamics of carbon (C) flux between plants and soil is critical to our understanding of the long-term fate of C stored in soils. The potential priming of old organic matter decomposition by fresh C input from plants means that the impact of environmental changes on the interactions between plant C allocation and soil C storage need to be better understood. We used forest girdling to investigate the partitioning of total soil CO2 efflux (RS) into autotrophic (RA) and heterotrophic (RH) flux components and their interaction with litter decomposition.
The reduction in RS in girdled plots stabilized within two weeks at 65% of control plot values, indicating that RS is dominated by RH, and that only a small pool of available non-structural C remains in roots in late summer to sustain rhizosphere metabolic processes. RAcontributions declined from 35% late in the growing season to about 25% in winter.
Our results indicate that actual root respiration (RR) and respiration by ectyomycorrhizas and other rhizospheric organisms (RM) contribute c. 50% each to RA between September and early November. During winter, RA remained significantly greater than zero despite frequent sub-zero air temperatures, with RM being a dominant component of RA during this period.
Forest girdling significantly increased the age of C in soil-respired CO2, consistent with the removal of contemporary C derived fromRA. Partitioning of soil CO2 efflux on the basis of 14C results shows good agreement with the flux reduction observed between girdled and control plots.
Litter bag incubations indicate a promoting influence of an intact C supply to the rhizosphere on decomposition, indicating a positive rhizosphere priming effect.
Synthesis: Our results demonstrate significant contribution of mycorrhizas and other rhizosphere organisms to RS, and suggest a direct link between an intact rhizosphere and litter decomposition dynamics. These results highlight the tight coupling between autotroph activity and soil decomposition processes in forest soils, and add to the growing body of evidence that plant and soil processes cannot be treated separately.
Project /
SEI is developing the Shasta River Water Allocation Model to help evaluate potential management actions in the watershed under the California Water Action Plan.
Event on 11 April in Oxford /
Join us online or in person as we explore the barriers and enablers to supporting adaptation to climate change for marginalised groups.