Diurnal patterns of productivity of arbuscular mycorrhizal fungi revealed with the Soil Ecosystem Observatory.
Bottom Line: AM fungal hyphae showed significantly different rates of growth and dieback over a period of 24 h and paralleled the circadian-driven photosynthetic oscillations observed in plants.Growth and dieback events often occurred simultaneously and were tightly coupled with soil temperature and moisture, suggesting a rapid acclimation of the external phase of AM fungi to the immediate environment.Changes in the environmental conditions and variability of the mycorrhizosphere may alter the diurnal patterns of productivity of AM fungi, thereby modifying soil carbon sequestration, nutrient cycling and host plant success.
Affiliation: Department of Environmental Earth System Science, Stanford University, Stanford, CA, 94305, USA; Department of Global Ecology, Carnegie Institution for Science, Stanford, CA, 94305, USA; Center for Conservation Biology, University of California, Riverside, CA, 92521, USA.Show MeSH
Mentions: Like plants, AM fungi may express diurnal-scale patterns of growth, dieback and net productivity, in accordance with endogenous circadian systems or environmental stimuli (Heinemeyer et al., 2006); however, to date, no study has tested this directly. Although not suggestive of a diurnal periodicity per se, Johnson et al. (2002) found that the in situ flux of pulse-derived 13C peaked in its release as 13CO2 in AM fungi-colonized soil cores in the first 0–6 h, revealing a rapid allocation of host plant C to AM hyphae. Previous field-based studies on AM rhizomorphs – that is, distinct, large cords comprising several hyphal strands – using in situ manual minirhizotrons (Fig.1), showed rapid diurnal changes in rhizomorph length, with growth up to 105.4 cm m−2 d−1 (Heinemeyer et al., 2006; Vargas & Allen, 2008a,b; Hasselquist et al., 2010). Given that diel changes in rhizomorphs were dynamic over a 24-h interval, this suggests that individual fungal hyphae may respond similarly. Together, these results suggest that the productivity of mycorrhizal fungi has yet to be quantified at the time scale in which it operates and, if so, any patterns of growth and dieback over a 24-h day : night cycle remain undiscovered.
Affiliation: Department of Environmental Earth System Science, Stanford University, Stanford, CA, 94305, USA; Department of Global Ecology, Carnegie Institution for Science, Stanford, CA, 94305, USA; Center for Conservation Biology, University of California, Riverside, CA, 92521, USA.