skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Measurements of Soil Moisture, Infiltration, and Hydrophobicity in Yosemite National Park Across Differing Fire Histories
The impact of wildfire on soil properties is difficult to predict, partially due to a shortage of field observations. To help address this need, we have assembled a unique dataset of soil properties (moisture, infiltration rate, and water drop penetration time) at over 100 individual locations within Yosemite National Park. These locations cover a wide range of fire history, soil texture, vegetation cover, and topography. Measurements span May 2022 through July 2023, capturing both a dry year and a wet year. A subset of sites burned in late summer 2022, allowing for pre- and post-fire measurements. Each individual site was measured 1-3 separate times. Water drop penetration time was measured at the soil surface, 1cm, and 3cm depths. Infiltration rate was measured at the soil surface and at 3cm depth using a mini disk infiltrometer.  more » « less
Award ID(s):
2011346
PAR ID:
10625343
Author(s) / Creator(s):
; ;
Publisher / Repository:
Hydroshare
Date Published:
Subject(s) / Keyword(s):
fire soil moisture hydrophobicity water drop penetration time infiltration Yosemite
Format(s):
Medium: X
Location:
Yosemite National Park
Institution:
Desert Research Institute
Sponsoring Org:
National Science Foundation
More Like this
  1. null (Ed.)
    There is an increased risk of future fire disturbances due to climate change and anthropogenic activity. These disturbances can impact soil moisture content and infiltration, which are important antecedent conditions for predicting rainfall–runoff processes in semi-arid regions. Yet these conditions are not well documented. This case study provides critical field measurements and information, which are needed to improve our understanding of mechanisms such as precipitation and temperature that lead to the variability of soil properties and processes in urban and burned landscapes. In June 2018, a fire burned a portion of the riparian zone in Alvarado Creek, an urban tributary of the San Diego River in California, United States. This fire provided an opportunity to observe soil moisture content and infiltration for one year after the fire. Three transects (one burned and two unburned) were monitored periodically to evaluate the complex spatial and temporal dynamics of soil moisture and infiltration patterns. Average dry season soil moisture content was less than five percent volume water content (%VWC) for all transects, and the burned transect exhibited the lowest %VWC during the wet season. Infiltration rates displayed a high degree of spatial and temporal variability. However, the location with the highest burn severity had the lowest average infiltration rate. The observed differences between the burned and unburned transects indicate that the fire altered hydrologic processes of the landscape and reduced the ability of the soil to retain water during the wet season. This research provides the first high-resolution soil moisture and infiltration field analysis of an urban fire-disturbed stream in southern California and a method to characterize post-fire hydrologic conditions for rainfall–runoff processes. 
    more » « less
  2. The Caldor fire burned ~222,000 acres of the Eastern Sierra Nevada during summer–fall 2021. We evaluated the effects of this “megafire” on the physical properties of a sandy soil developed from glacial tills to document fire-induced soil modifications in this region. We measured soil water retention and hydraulic conductivity functions as well as the thermal properties of five core samples from control (unburned) areas and eight core samples from burned soil of the same soil unit. Soil water repellency was measured in terms of water drop penetration time (WDPT) in the field and apparent contact angle in the laboratory on control and burned soil as well as ash samples. Soil organic matter (SOM) and particle and aggregate size distributions were determined on control and burned soil samples. Additionally, scanning electron microscopy (SEM) was used to image microaggregates of control and burned soil samples. We found a significant difference in SOM content and sand and silt aggregate size distribution between control and burned samples, which we associated with the disintegration of microaggregates due to the fire. We found no significant difference between soil water retention and hydraulic conductivity functions of control and burned soil but observed greater variation in saturated hydraulic conductivity and systematic shifts in thermal conductivity functions of burned compared to control samples. WDPT and apparent contact angle values were significantly higher for burned soils, indicating the occurrence of fire-induced soil hydrophobicity (FISH). Interestingly, the average apparent contact angle of the control soil was >90°, indicating that even the unburned soil was hydrophobic. However, the ash on top of the burned soil was found to be hydrophilic, having apparent contact angles <10°. Our results indicate that SOM and microaggregates were readily affected by the Caldor fire, even for sandy soil with a weakly developed structure. The fire seemed to have moderated thermal properties, significantly and soil wettability but had only minimal effects on water retention and hydraulic conductivity functions. Our findings demonstrate the complex nature of fire-soil interactions in a natural environment and highlight the need for additional investigation into the causes and processes associated with FISH and structure alterations due to fire to improve our ability to rapidly determine potential problem areas in terms of hazards commonly associated with fire-affected soils. 
    more » « less
  3. In the natural environment, wildfires affect how water interacts with soil leading to potentially catastrophic phenomena such as flooding, debris flows, and decreased water quality. Wildfires can cause soil sealing from increased soil water repellency, which in turn reduces infiltration and increases flood risk during rainfall. A 2017 meta-analysis found two properties that were affected by soil burning processes: Sorptivity (the capacity of a soil to absorb or desorb liquid by capillarity, S) and hydraulic conductivity (the ability for soil to transmit water when saturated, Kfs). Changes in these properties act synergistically to reduce infiltration, which increases erosion by accelerating and amplifying surface runoff. Thus, this research seeks to understand how soils subjected to severe burning compare to unburned soils. Using a mini-disk infiltrometer, field tests measured hydraulic conductivity of soils burned under slash and burn piles during the winters of 2016-17, 2020-21, and 2023-23 to better understand changes that occur in soil-hydraulic properties over time. These slash and burn piles served as approximate impacts for wildfires. Slash and burn piles also allow for paired measurements of unburned soils immediately adjacent to the burned area. Hydraulic conductivity was not significantly different when comparing burned and unburned soils 1 year after being burned. However, there was a significant difference between the hydraulic conductivity of soils burned 3 years ago compared to both unburned soil and soils burned 1 year ago. This suggests an interim process between 1- and 3-years post-burn that reduces hydraulic conductivity of burned soils. 
    more » « less
  4. Soil hydraulic properties (SHP) are among the indicators of the diversity and health of an ecosystem and are commonly measured by two criteria: infiltration and water retention capacity. This may be seen as an “Ecological Alteration,” resulting from the sum biological and nonbiological processes which modify the structure of the soil, including bioturbation and the accumulation of organic matter. These changes in soil structure drive the changes in SHP.  Central Chile has seen an abrupt and extensive land use/land cover transition from several hundred years of wheat cultivation (annually tilled) to short rotation (~25-30 yr) silviculture. This allows for neighboring assessment of soil impacts of transitioning from cultivated to uncultivated production as a function of time. Further, the region’s climate geography (a NorthSouth primary axis) allows us to view the soil health impacts of this change in planting along a precipitation gradient (850 – 1700 mm/yr) to help tease-out the impact of climate on temporal dynamics of soil properties.  We measured infiltration in five recently transitioned first rotation locations along this precipitation gradient. Sampling plots were established for continuous wheat, early-, mid-, and late-stage pine plantations, and Chilean Native Forest. We sampled in both the dry summer months and again in the wet winter months. In the dry sampling period, we found transitions from wheat to silviculture saw an initial decrease in infiltration; however, over time (~30 years) infiltration in the plantations approached that of the Native Forest (increasing approximately by an order of magnitude in 30 years). In the wet sampling period, the results were more inconclusive. Some plots did not show an increase in infiltration capacity while others showed a gradual increase over the same 30-year period.  
    more » « less
  5. Abstract Wildfire records demonstrate worsening patterns coupled with the spread to higher altitudes in several regions, raising the risk of post‐wildfire ground failures. This study investigates the post‐wildfire stability of unsaturated hillslopes against rainfall‐triggered shallow landslides. We developed a new physics‐based analytical framework incorporating wildfire‐induced changes in soil properties and near‐surface processes affecting the hillslope stability. A coupled hydromechanical infiltration model is integrated into an infinite slope stability analysis to simulate temporal changes in the depth profiles of soil water content, pressure head, and the resulting factor of safety (F.S.) of a vegetated slope. We consider the antecedent conditions of soil and vegetation cover, including the recovery phase after the fire, wildfire‐induced alterations in transpiration, and time‐varying infiltration rates. The model is verified against numerical simulations and employed in parametric studies evaluating the effects of wildfire severity and rainfall intensity‐duration. For the cases examined, it was shown that wildfire could reduce the F.S. of slopes by 25%. As a case study, the model successfully captured shallow rainfall‐triggered landslides that occurred in the Las Lomas watershed in California, USA, in 2019, 3 years after the Fish Fire burned the area. The proposed model uses measurable hillslope and wildfire characteristics and can be employed to evaluate the risk of shallow landslides in wildfire‐prone areas. 
    more » « less