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Water regime history drives responses of soil Namib Desert microbial communities to wetting events.

Frossard A, Ramond JB, Seely M, Cowan DA - Sci Rep (2015)

Bottom Line: The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days.T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories).The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures.

View Article: PubMed Central - PubMed

Affiliation: Centre for Microbial Ecology and Genomics (CMEG), Genomic Research Institute, University of Pretoria, Pretoria, South Africa.

ABSTRACT
Despite the dominance of microorganisms in arid soils, the structures and functional dynamics of microbial communities in hot deserts remain largely unresolved. The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days. A total of 168 soil microcosms received wetting events mimicking fog, light rain and heavy rainfall, with a parallel "dry condition" control. T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories). The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures. In contrast to microbial diversity, microbial activities (enzyme activities) showed very little response to the wetting events and were mainly driven by soil origin. This experiment clearly demonstrates the complexity of microbial community responses to wetting events in hyperarid hot desert soil ecosystems and underlines the dynamism of their indigenous microbial communities.

No MeSH data available.


(A) Experimental setup representing the day when each wetting event treatment (F, LR, HR and C) was applied over the 36 days (sampling times are indicated with arrows) and (B) graph of relative humidity (%RH) in the microcosms.
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f2: (A) Experimental setup representing the day when each wetting event treatment (F, LR, HR and C) was applied over the 36 days (sampling times are indicated with arrows) and (B) graph of relative humidity (%RH) in the microcosms.

Mentions: An artificial “Namib desert precipitation solution” was synthesized, based on the averaged chemistry data of fog and rain occurring around the Gobabeb research station2 and consisting of: 2.5 ppm , 2 ppm , 3 ppm Cl−, 1.8 ppm Na+, 0.3 ppm K+, 1 ppm Ca2+, 0.4 ppm Mg2+, 0.4 ppm , and 0.9 ppm . Three different water treatments with different intensities and frequencies observed in the Namib Desert (Fig. 2; rates based on Eckardt et al.2) were simulated: 1) Fog (F): 15 mm (corresponding to 16 ml) rain-water month−1 delivered in 8 events (every 4 days); 2) Light Rain (L): 60 mm (corresponding to 64 ml) rain-water month−1 delivered in 8 events (every 4 days); 3) Heavy Rain (H): 60 mm (corresponding to 64 ml) rain-water month−1, concentrated in a single event (every 4 h over 36 hours). In parallel, a Control (C) with no “precipitation solution” addition was prepared. In order to compare the effect of frequency and intensity of water pulses among the treatments, the frequency of wetting events for F and LR treatments were similar throughout the experimental period. Similarly, the total quantity of water received between LR and HR treatments was similar at the end of the experimental period, although their wetting event frequencies differed (LR = 8 events, HR = 1 event).


Water regime history drives responses of soil Namib Desert microbial communities to wetting events.

Frossard A, Ramond JB, Seely M, Cowan DA - Sci Rep (2015)

(A) Experimental setup representing the day when each wetting event treatment (F, LR, HR and C) was applied over the 36 days (sampling times are indicated with arrows) and (B) graph of relative humidity (%RH) in the microcosms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508562&req=5

f2: (A) Experimental setup representing the day when each wetting event treatment (F, LR, HR and C) was applied over the 36 days (sampling times are indicated with arrows) and (B) graph of relative humidity (%RH) in the microcosms.
Mentions: An artificial “Namib desert precipitation solution” was synthesized, based on the averaged chemistry data of fog and rain occurring around the Gobabeb research station2 and consisting of: 2.5 ppm , 2 ppm , 3 ppm Cl−, 1.8 ppm Na+, 0.3 ppm K+, 1 ppm Ca2+, 0.4 ppm Mg2+, 0.4 ppm , and 0.9 ppm . Three different water treatments with different intensities and frequencies observed in the Namib Desert (Fig. 2; rates based on Eckardt et al.2) were simulated: 1) Fog (F): 15 mm (corresponding to 16 ml) rain-water month−1 delivered in 8 events (every 4 days); 2) Light Rain (L): 60 mm (corresponding to 64 ml) rain-water month−1 delivered in 8 events (every 4 days); 3) Heavy Rain (H): 60 mm (corresponding to 64 ml) rain-water month−1, concentrated in a single event (every 4 h over 36 hours). In parallel, a Control (C) with no “precipitation solution” addition was prepared. In order to compare the effect of frequency and intensity of water pulses among the treatments, the frequency of wetting events for F and LR treatments were similar throughout the experimental period. Similarly, the total quantity of water received between LR and HR treatments was similar at the end of the experimental period, although their wetting event frequencies differed (LR = 8 events, HR = 1 event).

Bottom Line: The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days.T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories).The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures.

View Article: PubMed Central - PubMed

Affiliation: Centre for Microbial Ecology and Genomics (CMEG), Genomic Research Institute, University of Pretoria, Pretoria, South Africa.

ABSTRACT
Despite the dominance of microorganisms in arid soils, the structures and functional dynamics of microbial communities in hot deserts remain largely unresolved. The effects of wetting event frequency and intensity on Namib Desert microbial communities from two soils with different water-regime histories were tested over 36 days. A total of 168 soil microcosms received wetting events mimicking fog, light rain and heavy rainfall, with a parallel "dry condition" control. T-RFLP data showed that the different wetting events affected desert microbial community structures, but these effects were attenuated by the effects related to the long-term adaptation of both fungal and bacterial communities to soil origins (i.e. soil water regime histories). The intensity of the water pulses (i.e. the amount of water added) rather than the frequency of wetting events had greatest effect in shaping bacterial and fungal community structures. In contrast to microbial diversity, microbial activities (enzyme activities) showed very little response to the wetting events and were mainly driven by soil origin. This experiment clearly demonstrates the complexity of microbial community responses to wetting events in hyperarid hot desert soil ecosystems and underlines the dynamism of their indigenous microbial communities.

No MeSH data available.