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Water from air: an overlooked source of moisture in arid and semiarid regions.

McHugh TA, Morrissey EM, Reed SC, Hungate BA, Schwartz E - Sci Rep (2015)

Bottom Line: This phenomenon rapidly increased soil moisture and stimulated microbial carbon (C) cycling, and the flux of water vapor to soil had a stronger impact than temperature on microbial activity.In a semiarid grassland, we also observed that non-rainfall water inputs stimulated microbial activity and C cycling.Together these data suggest that, during rain-free periods, atmospheric moisture in drylands may significantly contribute to variation in soil water content, thereby influencing ecosystem processes.

View Article: PubMed Central - PubMed

Affiliation: U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, USA.

ABSTRACT
Water drives the functioning of Earth's arid and semiarid lands. Drylands can obtain water from sources other than precipitation, yet little is known about how non-rainfall water inputs influence dryland communities and their activity. In particular, water vapor adsorption--movement of atmospheric water vapor into soil when soil air is drier than the overlying air--likely occurs often in drylands, yet its effects on ecosystem processes are not known. By adding (18)O-enriched water vapor to the atmosphere of a closed system, we documented the conversion of water vapor to soil liquid water across a temperature range typical of arid ecosystems. This phenomenon rapidly increased soil moisture and stimulated microbial carbon (C) cycling, and the flux of water vapor to soil had a stronger impact than temperature on microbial activity. In a semiarid grassland, we also observed that non-rainfall water inputs stimulated microbial activity and C cycling. Together these data suggest that, during rain-free periods, atmospheric moisture in drylands may significantly contribute to variation in soil water content, thereby influencing ecosystem processes. The simple physical process of adsorption of water vapor to soil particles, forming liquid water, represents an overlooked but potentially important contributor to C cycling in drylands.

No MeSH data available.


Path diagram displaying the role of soil temperature and soil moisture in regulating soil CO2 efflux rates under a reduced model.Arrows represent unidirectional causal relationships. The amount of variation that can be explained by the model is indicated by the R2 values associated with each response variable. Standardized path coefficients (r) associated with each arrow reflect the strength of each relationship (p  <  0.001 in both cases). The full model also included the direct assessment of temperature effects on CO2 efflux rates, but since that relationship was not statistically significant, no arrow is shown.
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f3: Path diagram displaying the role of soil temperature and soil moisture in regulating soil CO2 efflux rates under a reduced model.Arrows represent unidirectional causal relationships. The amount of variation that can be explained by the model is indicated by the R2 values associated with each response variable. Standardized path coefficients (r) associated with each arrow reflect the strength of each relationship (p  <  0.001 in both cases). The full model also included the direct assessment of temperature effects on CO2 efflux rates, but since that relationship was not statistically significant, no arrow is shown.

Mentions: In order to test the hypothesis that increased soil moisture from non-rainfall water inputs was the main driver of soil CO2 efflux in the field (Supplementary Fig. S2), we conducted a path analysis to determine how soil temperature and moisture affected soil respiration. A theory-constrained full model was developed to represent all hypothetical relationships between soil temperature, soil moisture, and soil CO2 efflux within our system. Using the experimental data, a reduced model was attained by sequentially removing paths in order of largest probability value until all remaining paths were significant (Fig. 3). These results are consistent with a scenario in which low temperatures enable the movement of water vapor from air to soil, and the subsequent increase in soil moisture, in turn, stimulates soil CO2 efflux rates. This demonstration of increased CO2 efflux in the laboratory and under field conditions provides strong evidence that atmospheric water influences the activity of soil microorganisms.


Water from air: an overlooked source of moisture in arid and semiarid regions.

McHugh TA, Morrissey EM, Reed SC, Hungate BA, Schwartz E - Sci Rep (2015)

Path diagram displaying the role of soil temperature and soil moisture in regulating soil CO2 efflux rates under a reduced model.Arrows represent unidirectional causal relationships. The amount of variation that can be explained by the model is indicated by the R2 values associated with each response variable. Standardized path coefficients (r) associated with each arrow reflect the strength of each relationship (p  <  0.001 in both cases). The full model also included the direct assessment of temperature effects on CO2 efflux rates, but since that relationship was not statistically significant, no arrow is shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561883&req=5

f3: Path diagram displaying the role of soil temperature and soil moisture in regulating soil CO2 efflux rates under a reduced model.Arrows represent unidirectional causal relationships. The amount of variation that can be explained by the model is indicated by the R2 values associated with each response variable. Standardized path coefficients (r) associated with each arrow reflect the strength of each relationship (p  <  0.001 in both cases). The full model also included the direct assessment of temperature effects on CO2 efflux rates, but since that relationship was not statistically significant, no arrow is shown.
Mentions: In order to test the hypothesis that increased soil moisture from non-rainfall water inputs was the main driver of soil CO2 efflux in the field (Supplementary Fig. S2), we conducted a path analysis to determine how soil temperature and moisture affected soil respiration. A theory-constrained full model was developed to represent all hypothetical relationships between soil temperature, soil moisture, and soil CO2 efflux within our system. Using the experimental data, a reduced model was attained by sequentially removing paths in order of largest probability value until all remaining paths were significant (Fig. 3). These results are consistent with a scenario in which low temperatures enable the movement of water vapor from air to soil, and the subsequent increase in soil moisture, in turn, stimulates soil CO2 efflux rates. This demonstration of increased CO2 efflux in the laboratory and under field conditions provides strong evidence that atmospheric water influences the activity of soil microorganisms.

Bottom Line: This phenomenon rapidly increased soil moisture and stimulated microbial carbon (C) cycling, and the flux of water vapor to soil had a stronger impact than temperature on microbial activity.In a semiarid grassland, we also observed that non-rainfall water inputs stimulated microbial activity and C cycling.Together these data suggest that, during rain-free periods, atmospheric moisture in drylands may significantly contribute to variation in soil water content, thereby influencing ecosystem processes.

View Article: PubMed Central - PubMed

Affiliation: U.S. Geological Survey, Southwest Biological Science Center, Moab, UT, USA.

ABSTRACT
Water drives the functioning of Earth's arid and semiarid lands. Drylands can obtain water from sources other than precipitation, yet little is known about how non-rainfall water inputs influence dryland communities and their activity. In particular, water vapor adsorption--movement of atmospheric water vapor into soil when soil air is drier than the overlying air--likely occurs often in drylands, yet its effects on ecosystem processes are not known. By adding (18)O-enriched water vapor to the atmosphere of a closed system, we documented the conversion of water vapor to soil liquid water across a temperature range typical of arid ecosystems. This phenomenon rapidly increased soil moisture and stimulated microbial carbon (C) cycling, and the flux of water vapor to soil had a stronger impact than temperature on microbial activity. In a semiarid grassland, we also observed that non-rainfall water inputs stimulated microbial activity and C cycling. Together these data suggest that, during rain-free periods, atmospheric moisture in drylands may significantly contribute to variation in soil water content, thereby influencing ecosystem processes. The simple physical process of adsorption of water vapor to soil particles, forming liquid water, represents an overlooked but potentially important contributor to C cycling in drylands.

No MeSH data available.