Microclimate and environmental change decades following repeat wildfire and vegetation type conversion in a central Arizona ponderosa pine forest

Authors: PETRIE, M - University Of Nevada Las Vegas, Las Vegas, Nv; HAMMOND, K - University Of Nevada Las Vegas, Las Vegas, Nv; Biederman, Joel; Devine, Charles; LEONARD, J - Us Forest Service (FS); TYLER, R - Us Forest Service (FS)

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2026
Publication Date: 6/16/2026
Citation: Petrie, M.D., Hammond, K.D., Biederman, J.A., Devine, C.J., Leonard, J.M., Tyler, R. 2026. Microclimate and environmental change decades following repeat wildfire and vegetation type conversion in a central Arizona ponderosa pine forest. Agricultural and Forest Meteorology. 388. Article 111297. https://doi.org/10.1016/j.agrformet.2026.111297.
DOI: https://doi.org/10.1016/j.agrformet.2026.111297

Interpretive Summary: This research explores how repeated wildfires and the subsequent loss of forest cover alter the local soil moisture and temperature conditions, aiming to quantify the environmental shift from a ponderosa pine forest to a more arid-like landscape. USDA researchers in the Tucson Southwest Watershed Research Center in collaboration with University and Forest Service researchers compared a relatively intact ponderosa pine forest (PIPO) with a nearby area that suffered a severe, stand-replacing fire in 2000 (PIPO burned) in central Arizona. By monitoring meteorological data and soil moisture/temperature from 2022–2025, they measured how the lack of tree canopy in the burned area impacted solar radiation, wind speed, snowmelt, and soil water retention. The study reveals a startling "elevation shift," where the environmental conditions of the burned high-elevation forest now resemble those of much lower, hotter, and drier pinyon-juniper woodlands. This work is critical for land managers and conservationists in the southwestern US, as it provides physical evidence that wildfire can trigger permanent "type conversion," making it increasingly difficult for original forest species to ever recover under ongoing warming weather trends.

Technical Abstract: Wildfire is altering forested landscapes across the southwestern United States. There is opportunity to better understand regional landscape change by comparing more and less wildfire-affected forest areas at local scales. We evaluated meteorological and above- and belowground environmental variables in less-disturbed (PIPO: 2016 understory wildfire) and more-disturbed (PIPO burned: 2000 stand-replacing, 2016 understory) ponderosa pine forest in central Arizona, USA. PIPO burned experienced low conifer recovery and extensive woody plant type conversion following the 2000 wildfire. Using ground-based instrumentation and snow transect data, we found considerable abiotic differences between PIPO and PIPO burned during a recent period (2022-2025 water years) with near-average air temperatures and precipitation, and one very dry cool season (2025). These included significantly higher warm season (April-September) and cool season (October-March) solar radiation, wind speed, surface and soil temperature, and reference evapotranspiration. Although average snow depth was significantly higher at PIPO burned, its snow often melted earlier in the spring. Near surface soil moisture (10, 20, 40 cm) at PIPO burned was significantly lower than PIPO in both the warm and cool season. Underscoring the severity of these changes, we found that many meteorological and environmental variables at PIPO burned (2168 m) were on average more similar to those of lower elevation pin˜on pine-juniper woodland (1605 m) than they were to PIPO (2190 m), and the dynamics of soil temperature and moisture were often dissimilar between PIPO and PIPO burned. These local abiotic changes, here associated with repeat wildfire and woody plant type conversion over the past 25 years, illustrate the considerable transformation of forested landscapes in the southwestern US.