Elevated CO2 alters the rhizosphere effect on crop residue decomposition
Background and aims
Elevated atmospheric CO2 (eCO2) can affect microbial decomposition of native soil organic carbon (SOC) via enhanced root exudation and rhizosphere activity. Few studies have examined the effect of eCO2 on the decomposition of newly-added crop residues, which are important to understand below-ground C changes. A soil microcosm experiment was conducted to examine whether eCO2 would enhance the rhizosphere effects on the decomposition of crop residues.
White lupin (Lupinus albus L. cv. Kiev) was grown for 34 or 62 days under ambient CO2 (aCO2, 400 μmol mol−1) or eCO2 (800 μmol mol−1) in a low-C (2.0 mg g−1) soil which was amended with or without dual 13C and 15N labelled wheat, field pea or canola crop residues. An isotopic tracing technique was adopted to partition residue-derived CO2 from total below-ground CO2 efflux. Two independent groups of data were analysed statistically at either Day 34 or 62.
The presence of white lupin increased the decomposition of all residues at Day 34. This positive rhizosphere effect on residue decomposition decreased and was even reversed at Day 62, probably due to depletion of labile C, or microbial N limitation, or rhizosphere acidification. The eCO2-induced decomposition depended on residue type at Day 34. Specifically, when compared to aCO2, eCO2 did not affect the decomposition of canola residue, increased that of field pea residue by 13.5% but decreased wheat straw decomposition by 7.4%. However, residue decomposition was, on average, 13% higher under eCO2 at Day 62, which was correlated positively with the increase in rhizosphere extractable C (P < 0.01).
Elevated CO2 generally increased residue decomposition in the rhizosphere, but this effect was mediated by residue type at Day 34. Enhanced residue decomposition under legumes at eCO2 may favour C turnover and the release of residue N.
Keywords13C 15N Dual-labelling Lupinus albus Residue type Residue decomposition Rhizosphere effect
We are grateful to anonymous reviewers for their valuable comments, Mark Richards for providing the white lupin seeds, Dr. Clayton Butterly for providing the Tenosol soil and involvement of dual-labelled crop-residue generation, and Leanne Lisle for performing the IRMS analysis.
- Cheng W, Kuzyakov Y (2005) Root effects on soil organic matter decomposition. In: Wright SF, Zobel RW (eds) Roots and Soil Management: Interactions between Roots and the Soil, Agronomy Monograph no. 48. ASA-CSSA-SSSA, Madison, pp 119–143Google Scholar
- Isbell RF, NCST (2016) The Australian soil classifiction. CSIRO Publishing, MelbourneGoogle Scholar
- Paterson E, Thornton B, Midwood AJ, Osborne SM, Sim A, Millard P (2008) Atmospheric CO2 enrichment and nutrient additions to planted soil increase mineralisation of soil organic matter, but do not alter microbial utilisation of plant- and soil C-sources. Soil Biol Biochem 40:2434–2440CrossRefGoogle Scholar
- Pregitzer KS, Zak DR, Loya WM, Karberg NJ, King JS, Burton AJ (2007) The contribution of root-rhizosphere interactions to biogeochemical cycles in a changing world. In: Cardon ZG, Whitbeck JL (eds) The rhizosphere: an ecological perspective. Elsevier Academic Press, Burlington, pp 155–174CrossRefGoogle Scholar
- Smith P, Davies CA, Ogle S, Zanchi G, Bellarby J, Bird N, Boddey RM, McNamara NP, Powlson D, Cowie A, Noordwijk M, Davis SC, Richter DD, Kryzanowski L, Wijk MT, Stuart J, Kirton A, Eggar D, Newton-Cross G, Adhya TK, Braimoh AK (2012) Towards an integrated global framework to assess the impacts of land use and management change on soil carbon: current capability and future vision. Glob Chang Biol 18:2089–2101CrossRefGoogle Scholar
- Weisskopf L, Le Bayon R-C, Kohler F, Page V, Jossi M, Gobat J-M, Martinoia E, Aragno M (2008) Spatio-temporal dynamics of bacterial communities associated with two plant species differing in organic acid secretion: a one-year microcosm study on lupin and wheat. Soil Biol Biochem 40:1772–1780CrossRefGoogle Scholar