Short-term effects of wildfire on Canary Islands’ endemic lizards

Mammalian herbivores prefer burned areas and this attraction has largely been attributed to the increased nutrient content of the postfire green flush and more recently to the avoidance of predators. However, alternative reasons for this attraction could be: (i) to avoid disease carrying and behaviour changing invertebrates; (ii) because burned areas are warmer microclimates; or (iii) to obtain minerals from the ash. This study tests for differences in tick and fly (Diptera) numbers between burned and unburned areas in Serengeti National Park, Tanzania. It also tests for differences in ground and air column temperatures between burned and unburned areas and for differences in the mineral content of ash in burned areas compared to the mineral content of green leaves in unburned areas. We found no difference in the abundance of either type of invertebrate between burned and unburned areas. Only ground temperature was higher in burned areas and this was only during the middle of the day, when increases in temperature would be less important than at night. Ash was higher in Al, Ca, Cu, Mg, Mn and P than nearby green leaves from unburned vegetation. Thus, obtaining minerals from ash is the only alternative reason for attraction to burned areas that maybe supported by this study.

Historical and future global burned area with changing climate and human demography

Wildfire regimes are changing in the western United States, yet the ways in which wildfires influence native bees, the resources they depend on for food and nesting, or the traits that influence their interactions with plants are poorly understood. In burned and unburned areas in Montana, USA, we investigated the abundance and diversity of native bees, floral and nesting resources, nesting success, and traits of flowers and bees. In two of the three localities studied, burned areas, including areas that burned with high-severity wildfires, supported higher density and diversity of native bees and the flowers they depend on for food and larval provisioning. Burned areas also had more bare ground for ground-nesting bees and more available coarse woody debris for cavity-nesting bees than unburned areas. Moreover, cavity-nesting bees were completely unsuccessful at nesting in artificial nesting boxes in unburned areas, while nesting success was 40% in burned areas. Mean bee intertegular distance (a trait strongly correlated with tongue length, foraging distance, and body size) was similar between burned and unburned areas. However, wildfires influenced both interspecific and intraspecific trait variation of bees and plants. Intraspecific variation in bee intertegular distance was higher in unburned than burned areas. Both interspecific and intraspecific variation in floral traits important for interactions with pollinators were generally higher in burned than unburned areas. Thus, wildfires generally increased the density and species diversity of bees and flowers as well as trait variation at both trophic levels. We conclude that wildfires—even large, high-severity wildfires—create conditions that support native bees and the resources they need to flourish, but that unburned areas maintain trait variation in landscape mosaics with heterogeneous fire conditions.

Prescribed burning is increasingly being used to restore and maintain oak-dominated (Quercus spp.) forests in the eastern United States. We assessed effects of prescribed burning on the nesting ecology of the Wood Thrush (Hylocichla mustelina). Recent declines in Wood Thrush populations have prompted concern about their conservation status. Low-intensity surface fires in mixed-oak forests resulted in reductions in midstory vegetation, a documented habitat requirement for Wood Thrushes, but local population levels of Wood Thrushes did not differ between burned and unburned areas. Wood Thrushes inhabiting recently burned areas selected nest sites where leaf litter cover, fern cover, densities of shrubs and saplings, and moisture levels were higher and where fire intensity was lower in comparison to random sites. Wood Thrushes also placed their nests higher off the ground, and in taller and larger-diameter trees and shrubs, in burned than in unburned areas. Reproductive success did not differ between burned and unburned areas. However, successful nests were placed higher off the ground and in areas with lower densities of shrubs and saplings than unsuccessful nests in both burned and unburned areas. Prescribed burning appeared to have minimal effects on nesting ecology of Wood Thrushes, given their flexibility in nest placement, with no adverse consequences in terms of reproductive success. Local variation in fire intensity and moisture levels also maintained availability of suitable nesting habitat within burned areas. Continued monitoring would be appropriate to further assess the response of Wood Thrushes to prescribed burning, particularly in consideration of their conservation status and the uncertainty associated with potential long-term effects of habitat change.

The seasonal dynamics of gross nitrogen (N) mineralization, nitrification, and mineral nitrogen consumption rates were studied with the 15N pool dilute technique in burned and unburned Leymus chinensis (Trin.) Tzvel. (Chinese Wildryegrass) grasslands. Gross N mineralization is the gross rate of the process of the conversion of organic N to the form during decomposition before N immobilization by microbes. Similarly, gross nitrification is the gross rate of the conversion of and organic N to before N immobilization by microbes, and consumption is sum of mineral N losses by biological or nonbiological processes. Results indicated that gross mineralization and nitrification rates, and consumption rates, and soil concentrations of were higher in burned grassland areas than in unburned areas in April and May and that all were lower or similar compared to unburned areas in September. The soil concentrations of indicated no difference between burned and unburned areas in April and May, but burned areas had higher in July and September. Results indicate that prescribed burning in spring could benefit the renewal of grasslands of northeast China through mobilization of soil N pools.

<p>Wildfires are fundamental for maintaining ecosystem structure and functioning, and thus it is important to know how projected climate and land use changes will affect wildfire regimes globally. Fire-enabled vegetation models can be used to predict changes in fire regime but are still far from perfect since many of the processes that control different aspects of the fire regime are still relatively poorly understood. In this work, we investigated the underlying relationships between potential controls of different fire properties, including fire size, intensity and burnt area, at a global scale. We fitted three generalized linear models (GLM) to monthly data from 2010 to 2015 for fractional burnt area from the Global Fire Emissions Database version 4.1 (GFEDv4), fire size from the Global Fire Atlas database and median fire radiative power divided by square root of median fire size (as a proxy for fire intensity) from the MODIS MCD14ML dataset. We used partial residual plots between each predictor and each response variable to show the underlying linear relationships fitted by each model. We show that there are different controls on burnt area, on fire size and on fire intensity. Specifically, whilst burnt area is driven mainly by fuel availability and dryness, fire size is driven primarily by wind speed and fire intensity by tree cover and road density. Land fragmentation was highly limiting for fire size and burnt area whereas dryness was limiting for fire intensity. These findings suggest that it is possible to develop empirical models of multiple aspects of fire regimes which could be used to predict how these will change in the future. Furthermore, they highlight the importance of including landscape fragmentation as a control on fire explicitly within process-based fire models. Additionally, the limiting nature of dryness on fire intensity could be due to antecedent vegetation conditions and highlights the need for better representation of these conditions and their effect on fuel load. Finally, these results also suggest that the current treatment of ignition sources as an important driver in these models is unnecessary.</p>

Effects of prescribed burning on distribution and abundance of birds in a closed-canopy oak-dominated forest, Missouri, USA

Increasing wildfire frequency and severity in high‐elevation seasonal snow zones presents a considerable water resource management challenge across the western United States (U.S.). Wildfires can affect snowpack accumulation and melt patterns, altering the quantity and timing of runoff. While prior research has shown that wildfire generally increases snow melt rates and advances snow disappearance dates, uncertainties remain regarding variations across complex terrain and the energy balance between burned and unburned areas. Utilizing paired in situ data sources within the 2020 Cameron Peak burn area on the Front Range of Colorado, U.S., during the 2021–2022 winter, we found no significant difference in peak snow water equivalent (SWE) magnitude between burned and unburned areas. However, the burned south aspect reached peak SWE 22 days earlier than burned north. During the ablation period, burned south melt rates were 71% faster than unburned south melt rates, whereas burned north melt rates were 94% faster than unburned north aspects. Snow disappeared 7–11 days earlier in burned areas than unburned areas. Net energy differences at the burned and unburned weather station sites were seasonally variable, the burned area snowpack lost more net energy during the winter, but gained more net energy during the spring. Increased incoming shortwave radiation at the burned site was 6x more impactful in altering the net shortwave radiation balance than the decline in surface albedo. These findings emphasize the need for post‐wildfire water resource planning that accounts for aspect‐dependent differences in energy and mass balance to accurately predict snowpack storage and runoff timing.

Fire as driver of plant communities and soil properties changes in Puna grasslands in Southern Peruvian Andes

Restoration of an oak forest in east-central Missouri: Early effects of prescribed burning on woody vegetation

Although fire is a natural phenomenon in the dynamics of some biomes around the world, it can threaten the biodiversity of certain ecosystems. Climate change and the expansion of anthropogenic activities have drastically increased the occurrence of large-scale burnings worldwide. The 2020 fire events in the Pantanal marked a historically unprecedented record, burning an area of approximately 40,000 km2. However, how fires affect the local wildlife has yet to be evaluated. The aim of this study was to investigate the recovery of the avifauna in the Pantanal of Mato Grosso by comparing data selected from a previous study conducted between 2014 and 2016 with data collected in burned areas nine to twelve months after the fire. We compared diversity and community composition, investigated the influence of species trait foraging guild, foraging strata, and body mass on their response to fire, and complemented it with species’ individual responses. Bird richness and Shannon diversity were lower in burned areas, and the composition significantly varied between burned and unburned areas. The species’ response toward burned and unburned areas was significantly mediated by their traits, with smaller, piscivorous, omnivorous, ground and water, and midstory to canopy species being the most sensitive toward the environmental changes caused by the fire. Thirty-three species showed a negative response toward burned areas, but 46 species showed the opposite response, and 24 species were similarly abundant in unburned and burned areas. The present study is the first evaluation of the response of birds to the extreme fire events in the Pantanal and provides valuable insight into the recovery and resilience of local avifauna.

We used full-polarimetric L-band and P-band synthetic aperture radar (SAR) data collected from the recent NASA Arctic Boreal Vulnerability Experiment (ABoVE) airborne campaign and Sentinel-1 C-band dual-polarization data to understand the sensitivity of radar backscatter intensity and phase to fire-induced changes in the surface and subsurface soil processes in Arctic tundra underlain by permafrost. The 2007 Anaktuvuk River fire on the Alaska North Slope was used as a case study. At ~10-year postfire, we observed a strong increase (>~3–4 dB) in the low-frequency radar backscatter in severely burned areas during the thaw season, in contrast to limited (< ~0.5 dB) C-band backscatter differences (VV and VH) between burned and unburned areas. However, C-band winter backscatter is generally higher (>1 dB) in burned areas than the adjacent unburned areas. Polarimetric decomposition analysis indicated a general trend toward more random surface scattering, and strong increases in double-bounce scattering and volume scattering power at both P- and L-band in the burned areas. The ice-rich yedoma region shows the largest backscatter increases in burned areas and the highest correlation with burn severity and microtopography changes. The above backscatter changes are attributed to increasing surface roughness and microtopography due to ice-wedge degradation and thermokarst development and increasing subsurface scattering due to an overall drier and deeper active layer in burned areas. Among all frequencies, P-band shows consistently larger contrast in backscatter power and phase between burned and unburned areas, which makes it potentially more useful to study fire–permafrost interactions in the Arctic over decadal time scales.

In steep landscapes, wildfire‐induced changes to soil and vegetation can lead to extreme and hazardous geomorphic responses, including debris flows. The wildfire‐induced mechanisms that lead to heightened geomorphic responses, however, depend on many site‐specific factors including regional climate, vegetation, soil texture, and soil burn severity. As climate and land use change drive changes in fire regime, there is an increasing need to understand how fire alters geomorphic responses, particularly in areas where fire has been historically infrequent. Here, we examine differences in the initiation, magnitude, and particle‐size distribution of debris flows that initiated within the area burned by the 2019 Woodbury Fire in central Arizona, USA, and those that initiated in a nearby unburned area. Despite similar rainfall intensities, unburned watersheds were less likely to produce debris flows. Debris flows in unburned areas initiated from both runoff and shallow landslides, while debris flows only initiated from runoff‐related processes in the burned area. The grain‐size distribution making up the matrix of debris‐flow deposits within the burned area generally had a lower ratio of sand to silt relative to debris flows that initiated in the unburned area, though there were no systematic differences in the coarse fraction of debris‐flow sediment between burned and unburned areas. Results help expand our ability to predict postwildfire debris‐flow activity in a wider range of settings, specifically the Sonoran Desert ecoregion, and provide general insight into the impact of wildfire on geomorphic processes in steep terrain.

Northern peatlands are experiencing increased wildfire disturbance, threatening peatland biogeochemical function and ability to remain major stores of carbon (C) and macronutrients (nitrogen—N, and phosphorus—P). The impacts of climate change-driven drying on peatland nutrient dynamics have been explored previously; however, the impacts of wildfire on nutrient dynamics have not been examined when comparing burned and unburned areas in a post-fire fen. This study assessed the impact of wildfire on N and P bioavailability, change in CNP stoichiometric balance and feedback on plant nutrient limitation patterns in a fen peatland, one-year post-wildfire, by comparing Burned and Unburned areas. Water extractable P increased up to 200 times in shallow leachate, 125 times in groundwater and 5 times in peat. Surface ash leachate had increased concentrations in Ammonium (NH4+) and Nitrate (NO3−), and through groundwater mobility, increased extractable N concentrations were observed in peat throughout the entire fen. The net mineralization of N and P were minimal at the Burned areas relative to Unburned areas. Fire affected plant nutrient limitation patterns, switching from dominantly N-limited to NP co-limited and P-limitation in moss and vascular species respectively. The top 20 cm of the Burned area C concentrations was higher relative to the Unburned area, with increased CN and CP ratios also being found in the Burned area. These findings suggest that the long-term effects of elevated C, N, and P concentrations on plant productivity and decomposition must be re-evaluated for fire disturbance to understand the resiliency of peatland biogeochemistry post-wildfire.

Fire regimes have distinct global controls, and how burnt area, wildfire size and wildfire intensity independently respond to changes in climate, vegetation, and human activity remains challenging to quantify. Here, we use robust empirical models of burnt area, fire size and a measure of intensity to explore the global sensitivity of fire regimes to changes in climate, atmospheric CO2 and human activity under contrasting climate states, specifically at the end of the century under two climate change mitigation scenarios and at the Last Glacial Maximum. Our simulations show a global shift in wildfire patterns by 2100 CE under both low- and high-mitigation scenarios with reduced burnt area in tropical regions but larger and more intense wildfires in extra-tropical regions. Under low mitigation, increases in burnt area worldwide overwhelm the current human-driven declining trend, with fire size and intensity increasingly limited by dryness and vegetation fragmentation. Under different future conditions burnt area continues to increase due to changes fuel availability and dryness, fire intensity is increasingly limited by fuel build-up, and fire size by fuel continuity. These trends differ from those shown in simulations at the last Glacial Maximum, which show decreased burnt area, alongside increased fire size and intensity compared to present, consistent with sedimentary charcoal evidence. The decoupling between different fire properties occurs because of the different temporal and spatial scales on which the controls of burnt area, fire size and fire intensity operate. Under future conditions, the effect of a warming climate and increasing atmospheric CO2 amplify each other, whereas in cold climate with low atmospheric CO2, they dampen each other. These findings have immediate implications for the improvement of process-based fire models, which currently do not take the distinctions between these fire properties into account. They also suggest that the current observed patterns of fire regimes today may not hold constant under changing conditions.