Location: Southwest Watershed Research Center
Project Number: 2022-13610-013-028-I
Project Type: Interagency Reimbursable Agreement
Start Date: Aug 1, 2024
End Date: Jun 1, 2029
Objective:
Objectives: 1) Establish and maintain a Snowpack, Soil-Moisture and Fuel-Moisture Monitoring Network in Northern Arizona, 2) Develop a database (SnowPix) for the collection, standardization, and serving of these ecohydrologic datasets among ARS, the Cooperator, and future data contributors and end-users (e.g. fire behavior modelers), 3) Develop field methods for remote sensing of wildfire fuels moisture, and 4) Quantify how vegetation management regulates wildfire fuels moisture as mediated by snowpack dynamics and soil moisture.
Rationale: Recent studies in various vegetation types have uncovered strong linkages between soil moisture and fuel moisture, but these linkages have not been quantified across Northern Arizona, which contains the Four Forest Restoration Initiative (4FRI), a priority landscape under the U.S. Wildfire Crisis Strategy. Recent studies in Northern Arizona have quantified how forest management mediates snow processes and resulting soil moisture dynamics, however, there remains a critical need to assess consequences of forest management on fuels moisture. In situ soil moisture measurements are still the best way to track soil moisture, especially in topographically complex and forested terrain. While there are active networks of soil moisture across agricultural soils, there is a growing need and a new coordinated push to develop networks across forested soils by ARS, the Cooperator, and other USDA partners. ARS helps coordinate a network of snow and soil moisture monitoring sites across northern Arizona. Recent results from these sites have demonstrated that thinned forest stands have significantly greater peak snowpack, snowmelt volume, and soil moisture at all depths and significantly greater tree canopy moisture content, especially during regional drought years, and that the 3-dimensional forest structure of the post-thinning forest affects the amount and timing of snowmelt due to changes in radiation balance and snow sublimation. The ability to link in situ measurements of snowpack and soil moisture with measurements of live and dead fuel moisture across different forest conditions (i.e., gradients of elevation, topography, 3-dimensional vegetation structure, climate, and highly variable interannual weather) will lead to improved forest health predictions through better drought indices, estimations of fuel loading, and predictive capacity of models for fire risk, spread, and severity.
Approach:
Study Sites:
Field measurements will focus on two forest management experimental sites on federal lands in northern Arizona where ARS and the Cooperator have been conducting research since 2019. Database development will include a network of 20 existing Snowtography sites where ARS is conducting research and any new sites established by the Cooperator.
Snow Measurements:
ARS will make daily snowpack measurements at 30-75 locations per focus site using Snowtography (snow-photography), a low-cost, automated system combining trail cameras with staff gauges deployed across gradients of forest structure to capture the resultant spatial variability in snow sublimation, snowmelt, and soil moisture. ARS led development of a Snowtography Handbook https://www.ars.usda.gov/pacific-west-area/tucson-az/southwest-watershed-research-center/research/snowtography/
Soil Moisture:
ARS and the Cooperator are measuring soil moisture with ~120 buried sensors across both focus sites with sensors for volumetric water content and soil water potential, which is a more direct indicator of plant water availability. Measurements are split among managed, unmanaged, and burned treatments for analysis of treatment impacts.
Surface Fuel Characterization:
ARS will assist the Cooperator with characterizing fuel loads across all time-lag categories (e.g., 1hr, 10hr, 100hr, 1000hr) via the Brown’s fuel transect method. ARS will help the Cooperator collect and process lidar data and UAV Structure-from-Motion imagery to estimate aboveground total biomass to determine surface fuel and aboveground biomass reductions from vegetation management and fire.
Fuel Moisture Dynamics:
ARS will assist the Cooperator in making fuel moisture content measurements including continuous measurements with automated sensors, direct gravimetric assessment, and infrared thermography. ARS will receive training in use of thermography to estimate vegetation moisture content and will contribute use of one ARS-owned thermal camera.
Comparisons Amongst Treatments:
The study will apply standard analysis-of-variance techniques to compare fuel types and moisture of different fuel classes across treatments (thinned/masticated, non-thinned, and burned). The vegetation structure, snowpack, soil moisture, fuel moisture, and climate data will be used to inform predictive models of fuel moisture over a range of 3-dimensional forest structure characteristics and over years with varying weather.
Database Development:
ARS has developed a prototype database called SnowPix to organize and share data and metadata across 20 Snowtography stations overseen by 10 different groups partnering with ARS across the Colorado River Basin. SnowPix is modeled after the well-known AmeriFLUX database, a “coalition of the willing” which shares consistent, high quality flux tower data for use in many hundreds of empirical and modeling studies. This project will further develop the SnowPix database to meet the needs of data contributors as well as data users, especially future groups using SnowPix data to train and evaluate models of fuels moisture and fire behavior.
