Elevated carbon dioxide and irrigation effects on water stable aggregates in a Sorghum field: a possible role for arbuscular mycorrhizal fungi

While soil biota and processes are becoming increasingly appreciated as important parameters for consideration in global change studies, the fundamental characteristic of soil structure is a neglected area of research. In a sorghum [Sorghum bicolor (L.) Moench] field experiment in which CO2[supplied using free‐air CO2 enrichment (FACE) technology] was crossed factorially with an irrigation treatment, soil aggregate (1–2 mm) water stability increased in response to elevated CO2. Aggregate water stability was increased by 40% and 20% in response to CO2, at ample and limited water supply treatments, respectively. Soil hyphal lengths of arbuscular mycorrhizal fungi (AMF) increased strongly (with a threefold increase in the dry treatment) in response to CO2, and the concentrations of one fraction (easily extractable glomalin, EEG) of the AMF‐produced protein glomalin were also increased. Two fractions of glomalin, and AMF hyphal lengths were all positively correlated with soil aggregate water stability. The present results further support the hypothesis that AMF can become important in global change scenarios. Although in this field study a causal relationship between hyphal length, glomalin and aggregate stability cannot be demonstrated, the present data do suggest that AMF could mediate changes in soil structure under elevated CO2. This could be of great importance in agricultural systems threatened by erosional soil loss.

[1]  J. Starr,et al.  Changes in Aggregate Stability and Concentration of Glomalin during Tillage Management Transition , 1999 .

[2]  C. Field,et al.  Rise in carbon dioxide changes soil structure , 1999, Nature.

[3]  C. Field,et al.  Soil biota responses to long-term atmospheric CO2 enrichment in two California annual grasslands , 1999, Oecologia.

[4]  P. Pinter,et al.  Free‐air CO2 enrichment and soil nitrogen effects on energy balance and evapotranspiration of wheat , 1999 .

[5]  M. V. D. van der Heijden,et al.  Increased allocation to external hyphae of arbuscular mycorrhizal fungi under CO2 enrichment , 1998, Oecologia.

[6]  J. Ingram,et al.  The interaction of soil biota and soil structure under global change , 1998 .

[7]  Hartley,et al.  Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems , 1998, Science.

[8]  M. Rillig,et al.  Soil fungal‐arthropod responses to Populus tremuloides grown under enriched atmospheric CO2 under field conditions , 1997 .

[9]  J. Lussenhop.  Let the Soil Work for Us , 1997 .

[10]  B. Degens.  Macro-aggregation of soils by biological bonding and binding mechanisms and the factors affecting these: a review , 1997 .

[11]  R. Miller,et al.  Soil aggregate stabilization and carbon sequestration: Feedbacks through organomineral associations , 1996 .

[12]  D. Coleman,et al.  Fundamentals of Soil Ecology , 1996 .

[13]  G. Daily,et al.  Restoring Value to the World's Degraded Lands , 1995, Science.

[14]  M. Wahlen,et al.  Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980 , 1995, Nature.

[15]  D. Pimentel,et al.  Environmental and Economic Costs of Soil Erosion and Conservation Benefits , 1995, Science.

[16]  D. Nehl.  Mycorrhizae in sustainable agriculture , 1995 .

[17]  S V Krupa,et al.  Plant responses to atmospheric CO2 enrichment with emphasis on roots and the rhizosphere. , 1994, Environmental pollution.

[18]  I. Jakobsen,et al.  External hyphae of vesicular arbuscular mycorrhizal fungi associated with trifolium subterraneum l. 1. spread of hyphae and phosphorus inflow into roots , 1992 .

[19]  R. Linderman.  Mycorrhizae in Sustainable Agriculture , 1992 .

[20]  I. Jakobsen,et al.  External hyphae of vesicular–arbuscular mycorrhizal fungi associated with Trifolium subterraneum L. , 1992 .

[21]  Peter Kuikman,et al.  Soil structural aspects of decomposition of organic matter by micro-organisms , 1990, Biogeochemistry.

[22]  J. Tisdall,et al.  Organic matter and water‐stable aggregates in soils , 1982 .