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: We found that the diurnal dynamics of AM fungal hyphae were visible – producing images of in situ and extra-radical AM fungal hyphae (Fig.2) – and quantifiable with the Soil Ecosystem Observatory. Using this new technology, we found that the rates of relative growth and dieback of AM fungal hyphae were significantly different across the four 6-h intervals comprising a 24-h day : night cycle (Fig.3; Kruskal–Wallis χ2 = 25.505, df = 3, P < 0.0001 (production); Kruskal–Wallis χ2 = 77.5848, df = 3, P < 0.0001 (mortality)). Peak growth rates of AM fungal hyphae occurred between 12:00 and 17:59 h, with a mean growth rate of 154 μm mm−3 soil h−1. This rate of growth was approximately four times greater than the growth observed in other intervals, which ranged from 27 to 47 μm mm−3 soil h−1. Similar to growth, the relative dieback rates of AM fungal hyphae were greatest between 12:00 and 17:59 h, and slightly greater than growth (170 μm mm−3 soil h−1). Dieback in nonpeak intervals ranged from 63 to 102 μm mm−3 soil h−1. Hyphal dieback and growth showed a clear minimum in the morning (i.e. 00:00–06:00 h) with rates of 63 and 27 μm mm−3 soil h−1, respectively.
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.