The desiccation of upper soil horizons is a common phenomenon, leading to a decrease in soil microbial activity and mineralization. Recent studies have shown that fungal communities and fungal-based food webs are less sensitive and better adapted to soil desiccation than bacterial-based food webs. One reason for a better fungal adaptation to soil desiccation may be hydraulic redistribution of water by mycelia networks. Here we show that a saprotrophic fungus (Agaricus bisporus) redistributes water from moist (–0.03 MPa) into dry (–9.5 MPa) soil at about 0.3 cm⋅min−1 in single hyphae, resulting in an increase in soil water potential after 72 h. The increase in soil moisture by hydraulic redistribution significantly enhanced carbon mineralization by 2,800% and enzymatic activity by 250–350% in the previously dry soil compartment within 168 h. Our results demonstrate that hydraulic redistribution can partly compensate water deficiency if water is available in other zones of the mycelia network. Hydraulic redistribution is likely one of the mechanisms behind higher drought resistance of soil fungi compared with bacteria. Moreover, hydraulic redistribution by saprotrophic fungi is an underrated pathway of water transport in soils and may lead to a transfer of water to zones of high fungal activity.
Amount of Redistributed water
Amount of redistributed water from chamber I to chamber II based on hydrogen stable isotope analyses (isotope mass spectrometer: delta V advantage, Thermo Fisher Scientific) of extracted water from collected soil samples of chamber II after deuterium-labeling of chamber I. Data is in relation to time after rewetting of chamber I and from all mesocosms of HR as well as control treatments (data used in Fig. 1).
Carbon dioxide production rates
Carbon dioxide and 13C-CO2 production rates based on efflux measurements using a infrared gas analyzer (LiCOR 820, Licor, USA) and an elemental analyzer (NA 1108, CE Instruments) – isotope ratio mass spectrometer (delta S, Finnigan MAT) linkage, respectively. Data is in relation to time after rewetting of chamber I and from all mesocosms of HR as well as control treatments.
Cumulative carbon mineralization of labelled plant material in chamber II
Cumulative carbon mineralization of labelled plant material in chamber II interpolated from measured 13C-CO2 efflux values (see also Carbon dioxide production rates.csv). Data is in relation to time after rewetting of chamber I and from all mesocosms of HR as well as control treatments.
Enzyme activity rates on soil surface of chamber II
Enzyme activity rates of N-acetylglucosaminidase (NAG) and cellobiohydrolase on soil surface of chamber II. Enzyme activite was measured using soil zymography with fluorogenic 4-methylumbelliferone-substrates. Data is in relation to time after rewetting of chamber I and the postion on the surface of chamber II (from 1-4 with increasing distance to the air gap). Values are given for all mesocosms of HR as well as control treatments.
Volumetric water change in chamber II
Volumetric water change in chamber II as monitored by soil moisture sensors (ECH2O-10 moisture sensors, Decagon Devices Inc). Data is in relation to time after rewetting of chamber I for all mesocosms of HR as well as control treatments.
Water potential of soil samples from chamber II
soil water potential ( as pF value) measured on collected soil samples from chamber II using the chilled mirror dewpoint method (WP4-T, Decagon Devices Inc.).Data is in relation to time after rewetting of chamber I and distance to the air gap (1=0-6.66 cm; 2= 6.66-13.33 cm; 3=13.33-20 cm). Values are given for all mesocosms of HR as well as control treatments.