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1. Vegetation and Fluvial Geomorphology Dynamics after an Urban Fire

   https://doi.org/10.3390/geosciences10080317  

   Mathews, Lauren E.; Kinoshita, Alicia M. (August 2020, Geosciences)

   null (Ed.)

   The goal of this research was to characterize the impact of invasive riparian vegetation on burn severity patterns and fluvial topographic change in an urban Mediterranean riverine system (Med-sys) after fire in San Diego, California. We assessed standard post-fire metrics under urban conditions with non-native vegetation and utilized field observations to quantify vegetation and fluvial geomorphic processes. Field observations noted both high vegetation loss in the riparian area and rapidly resprouting invasive grass species such as Arundo donax (Giant Reed) after fire. Satellite-based metrics that represent vegetation biomass underestimated the initial green canopy loss, as did volumetric data derived from three-dimensional terrestrial laser scanning data. Field measurements were limited to a small sample size but demonstrated that the absolute maximum topographic changes were highest in stands of Arundo donax (0.18 to 0.67 m). This work is the first quantification of geomorphic alterations promoted by non-native vegetation after fire and highlights potential grass–fire feedbacks that can contribute to geomorphic disruption. Our results support the need for ground-truthing or higher resolution when using standard satellite-based indices to assess post-fire conditions in urban open spaces, especially when productive invasive vegetation are present, and they also emphasize restoring urban waterways to native vegetation conditions. 

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2. Wildfire and Extreme Rainfall Reduce Soil Carbon and Nitrogen Pools in a Semiarid Shrubland Ecosystem

   https://doi.org/10.1029/2025JG009183  

   Lipson, D A; Alvarez, A G; Brouwer, J N; Cleland, E E; Lively, J B; Parsons, D S; Rivas, Fortunato Vincente; Smith, K L; Varon, E L; Xu, X (February 2026, Journal of Geophysical Research: Biogeosciences)

   Abstract Due to a combination of anthropogenic causes, semi‐arid shrublands like those in California and other Mediterranean‐type ecosystems are increasingly subject to wildfires and variable rainfall, including drought and atmospheric rivers. Fire changes soil structure, leaving soils vulnerable to erosion and loss of organic matter (OM), especially when followed by intense rain events. However, interactions of fire and extreme rainfall are challenging to study due to their unpredictability and the complex interacting factors such as fire intensity, vegetation structure, topography, and soil type. This study took advantage of a wildfire, natural variation in rainfall, and a controlled rain‐shelter experiment to examine the interactions of fire and rain on soil structure and OM storage. Fire reduced organic carbon and nitrogen associated with particulate organic matter and water stable aggregates, and changed soil hydrology, slowing infiltration of water to deeper layers. The combination of rain shelters and the extreme rain fall year (2023) allowed us to evaluate threshold effects of rain in post‐fire soils: in 2023, there was a loss of total soil OM from burned relative to unburned plots; rain shelter effects on soil organic matter pools were only detectable in 2023; and the interactive effects of fire and rain shelters in this year reduced infiltration of rain into soil in burned areas exposed to full rain conditions. These results suggest a feedback mechanism in which fire causes loss of soil OM, damages soil structure, and decreases rainfall infiltration, increasing erosion through increased runoff and slowing recovery of soil structure. 

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3. Urban Fire Severity and Vegetation Dynamics in Southern California

   https://doi.org/10.3390/rs13010019  

   Mathews, Lauren E.; Kinoshita, Alicia M. (January 2021, Remote Sensing)

   null (Ed.)

   A combination of satellite image indices and in-field observations was used to investigate the impact of fuel conditions, fire behavior, and vegetation regrowth patterns, altered by invasive riparian vegetation. Satellite image metrics, differenced normalized burn severity (dNBR) and differenced normalized difference vegetation index (dNDVI), were approximated for non-native, riparian, or upland vegetation for traditional timeframes (0-, 1-, and 3-years) after eleven urban fires across a spectrum of invasive vegetation cover. Larger burn severity and loss of green canopy (NDVI) was detected for riparian areas compared to the uplands. The presence of invasive vegetation affected the distribution of burn severity and canopy loss detected within each fire. Fires with native vegetation cover had a higher severity and resulted in larger immediate loss of canopy than fires with substantial amounts of non-native vegetation. The lower burn severity observed 1–3 years after the fires with non-native vegetation suggests a rapid regrowth of non-native grasses, resulting in a smaller measured canopy loss relative to native vegetation immediately after fire. This observed fire pattern favors the life cycle and perpetuation of many opportunistic grasses within urban riparian areas. This research builds upon our current knowledge of wildfire recovery processes and highlights the unique challenges of remotely assessing vegetation biophysical status within urban Mediterranean riverine systems. 

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4. Long-term fire effects on soil and vegetation nitrogen cycling: potential links to persistent stream nitrate export

   https://doi.org/10.1071/WF25145  

   Rhea, Allison E; Covino, Timothy P; Rhoades, Charles C (February 2026, International Journal of Wildland Fire)

   BackgroundSoil and stream nitrate (NO3−) concentrations often increase after severe fire from elevated nitrogen (N) mineralization and reduced plant uptake. However, it is unclear how long these effects persist and contribute to stream N export. AimsWe examined the contribution of soil N supply and vegetation N demand to 19-fold higher stream NO3− export that has persisted since the 2002 Hayman Fire in Colorado, USA. MethodsWe compared soil N pools, inorganic N production, subsurface (0–100 cm) NO3− concentrations, vegetation cover, productivity and N demand 17 years post-fire. We sampled along burned and unburned hillslopes to evaluate whether near-stream vegetation and soils attenuated N loss during downslope transport. Key resultsMineral soil, leachate and groundwater NO3− concentrations were higher in burned than unburned hillslopes, despite similar mineralization rates. Burned uplands showed 62% lower productivity and 28% lower N demand relative to unburned forests. Riparian recovery exceeded uplands but remained incomplete relative to unburned conditions. Burned uplands acted as N sources, with slight reductions in soil NO3− in downslope riparian soils. ConclusionsSustained NO3− export was driven by reduced vegetation N demand and subsurface transport, not increased mineralization. ImplicationsRevegetation of severely burned uplands and riparian zones may enhance long-term N retention. 

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5. Spodosol development and soil organic carbon distribution along a lithosequence in perhumid coastal temperate rainforest

   https://doi.org/10.1002/saj2.20695  

   Fedenko, Jennifer; D'Amore, David; Spinola, Diogo; Portes, Raquel; Dere, Ashlee; Lybrand, Rebecca A (September 2024, Soil Science Society of America Journal)

   A dense concentration of old-growth forest and a wet, cold climate promote mineral weathering and leaching in coastal temperate rainforest soils. Our objective was to assess soil development and soil organic carbon (SOC) distribution across 18 soil profiles in remote, upland terrain of southeast Alaska where pedon data are sparse. We made soil morphological observations, collected samples, and completed laboratory analyses to measure SOC content, pH, and particle size distribution. The survey of upland backslope soils included north- and south-facing hillslopes derived from three lithologies (slate, metavolcanic, and phyllite). The soils across all sites were very gravelly (51.8 ± 20.4% coarse fragments), acidic (mineral soil pH 4.85 ± 0.45), and moderately deep (96.56 ± 37.80 cm); thin, broken E horizons were underlain by thick, carbon-rich spodic horizons. Soil development was relatively consistent as demonstrated by the Profile Development Index with values from 15 to 26 and Podzolization Index values spanning 8 to 14. A mean pedon SOC stock of 198.02 ± 81.42 Mg C ha−1 (n = 18) was calculated using data collected for all upland organic and mineral soils from our work. The accumulation of SOC was similar among soils formed from contrasting lithologies with averages of 182 ± 15.70 Mg C ha−1 for slate, 188 ± 53.80 Mg C ha−1 for metavolcanic, and 218 ± 124 Mg C ha−1 for phyllite. Our work contributes to soil morphological observations, laboratory data, and SOC stock estimates required to better constrain and model pedogenic processes and SOC stock in remote forests where data sets are limited. 

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