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Abstract Microbial biomass is known to decrease with soil drying and to increase after rewetting due to physiological assimilation and substrate limitation under fluctuating moisture conditions, but how the effects of changing moisture conditions vary between dry and wet environments is unclear. Here, we conducted a meta‐analysis to assess the effects of elevated and reduced soil moisture on microbial biomass C (MBC) and microbial biomass N (MBN) across a broad range of forest sites between dry and wet regions. We found that the influence of both elevated and reduced soil moisture on MBC and MBN concentrations in forest soils was greater in dry than in wet regions. The influence of altered soil moisture on MBC and MBN concentrations increased significantly with the manipulation intensity but decreased with the length of experimental period, with a dramatic increase observed under a very short‐term precipitation pulse. Moisture effect did not differ between coarse‐textured and fine‐textured soils. Precipitation intensity, experimental duration, and site standardized precipitation index (dry or wet climate) were more important than edaphic factors (i.e., initial water content, bulk density, and clay content) in determining microbial biomass in response to altered moisture in forest soils. Different responses of microbial biomass in forest soils between dry and wet regions should be incorporated into models to evaluate how changes in the amount, timing, and intensity of precipitation affect soil biogeochemical processes.
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Water Responsive Fabrics with Artificial Leaf Stomata
Abstract Due to fiber swelling, textile fabrics containing hygroscopic fibers tend to decrease pore size under wet or increasing humidity and moisture conditions, the reverse being true. Nevertheless, for personal thermal regulation and comfort, the opposite is desirable, namely, increasing the fabric pore size under increasing humid and sweating conditions for enhanced ventilation and cooling, and a decreased pore size under cold and dry conditions for heat retention. This paper describes a novel approach to create such an unconventional fabric by emulating the structure of the plant leaf stomata by designing a water responsive polymer system in which the fabric pores increase in size when wet and decrease in size when dry. The new fabric increases its moisture permeability over 50% under wet conditions. Such a water responsive fabric can find various applications including smart functional clothing and sportswear. Graphical Abstract
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- Award ID(s):
- 1719875
- PAR ID:
- 10411982
- Date Published:
- Journal Name:
- Advanced Fiber Materials
- ISSN:
- 2524-7921
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Microbial biomass is known to decrease with soil drying and to increase after rewetting due to physiological assimilation and substrate limitation under fluctuating moisture conditions, but how the effects of moisture changes vary between dry and wet environments is unclear. Here, we conducted a meta‐analysis to assess the effects of elevated and reduced soil moisture on microbial biomass carbon (MBC) and nitrogen (MBN) across a broad range of forest sites between dry and wet regions. We found that the influence of both elevated and reduced soil moisture on MBC and MBN concentrations in forest soils was greater in dry than in wet regions. The influence of altered soil moisture on MBC and MBN concentrations increased significantly with the manipulation intensity but decreased with the length of experimental period, with a dramatic increase observed under a very short‐term precipitation pulse. Moisture effect did not differ between coarse‐ and fine‐textured soils. Precipitation intensity, experimental duration, and site standardized precipitation index (dry or wet climate) were more important than edaphic factors (i.e., initial water content, bulk density, clay content) in determining microbial biomass in response to altered moisture in forest soils. Different responses of microbial biomass in forest soils between dry and wet regions should be incorporated into models to evaluate how changes in the amount, timing and intensity of precipitation affect soil biogeochemical processes.more » « less
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Abstract Oxygen (O2) regulates soil reduction‐oxidation processes and therefore modulates biogeochemical cycles. The difficulties associated with accurately characterizing soil O2variability have prompted the use of soil moisture as a proxy for O2, as O2diffusion into soil water is much slower than in soil air. The use of soil moisture alone as a proxy measurement for O2could result in inaccurate O2estimations. For example, O2may remain high during cool months when soil respiration rates are low. We analyzed high‐frequency sensor data (e.g., soil moisture, CO2, gas‐phase soil pore O2) with a machine learning technique, the Self‐Organizing Map, to pinpoint suites of soil conditions associated with contrasting O2regimes. At two riparian sites in northern Vermont, we found that O2levels varied seasonally, and with soil moisture. For example, 47% of low O2levels were associated with wet and cool soil conditions, whereas 32% were associated with dry and warm conditions. Contrastingly, the majority (62%) of high O2conditions occurred under dry and warm conditions. High soil moisture levels did not always lead to low O2, as 38% of high O2values occurred under wet and cool conditions. Our results highlight challenges with predicting soil O2solely based on water content, as variable combinations of soil and hydrologic conditions can complicate the relationship between water content and O2. This indicates that process‐based ecosystem and denitrification models that rely solely on soil moisture to estimate O2may need to incorporate other site and climate‐specific drivers to accurately predict soil O2.more » « less
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Abstract Soil moisture heterogeneity can induce mesoscale circulations due to differential heating between dry and wet surfaces, which can, in turn, trigger precipitation. In this work, we conduct cloud-permitting simulations over a 100 km × 25 km idealized land surface, with the domain split equally between a wet region and a dry region, each with homogeneous soil moisture. In contrast to previous studies that prescribed initial atmospheric profiles, each simulation is run with fixed soil moisture for 100 days to allow the atmosphere to equilibrate to the given land surface rather than prescribing the initial atmospheric profile. It is then run for one additional day, allowing the soil moisture to freely vary. Soil moisture controls the resulting precipitation over the dry region through three different mechanisms: as the dry domain gets drier, (i) the mesoscale circulation strengthens, increasing water vapor convergence over the dry domain, (ii) surface evaporation declines over the dry domain, decreasing water vapor convergence over the dry domain, and (iii) precipitation efficiency declines due to increased reevaporation, meaning proportionally less water vapor over the dry domain becomes surface precipitation. We find that the third mechanism dominates when soil moisture is small in the dry domain: drier soils ultimately lead to less precipitation in the dry domain due to its impact on precipitation efficiency. This work highlights an important new mechanism by which soil moisture controls precipitation, through its impact on precipitation reevaporation and efficiency.more » « less
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Abstract Soil hydrology provides important background for understanding the fate of organic carbon (OC) buried by geomorphic processes as well as the influence of runoff, infiltration, and plant root uptake on long‐term erosion and landscape evolution. We modeled the hydrology of a 4.5‐m loess‐paleosol sequence on an eroding tableland in the U.S. central Great Plains using Hydrus 1D, a numerical unsaturated flow model, parameterized with high resolution measurements of the soil water retention and hydraulic conductivity curves, which were distinct for the loess and paleosols. We hypothesized that (a) the connection of paleosols to modern climate depends on their burial depth, (b) paleosols in the root zone would have broader pore‐size distributions than unweathered loess, and (c) this broader pore‐size distribution increased root water uptake and made vegetation more resilient to drought, increasing the stability of loess tablelands despite high erodibility and high local relief. Four years with varying total annual precipitation were simulated for the observed profile and two hypothetical profiles, one without paleosols and another with a shallow, strongly developed paleosol. In these simulations, soil moisture in shallow paleosols responds quickly to precipitation while a deeply buried paleosol is largely disconnected from the modern climate, contributing to buried OC preservation. Contrary to our expectation, the presence of paleosols did not increase root uptake relative to unweathered loess in either wet or dry years. The unweathered coarse loess we studied may have an optimal pore‐size distribution for root uptake, providing an alternative hypothesis for why highly erodible loess tablelands persist.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s42765-023-00269-5
