Unburned Areas Research Articles

Use of an Edaphic Microarthropod Index for Monitoring Wildfire Impact on Soil in Mediterranean Pine Forests

The aim of this study was to investigate the potential of the Biological Soil Quality index (QBS-ar index) for monitoring the impact of wildfires on Mediterranean pine forests soils. The QBS-ar is a simplified eco-morphological index, based on edaphic microarthropods. We analyzed the QBS-ar values of pine stands burned one or two times and at different time spans from fire (from 10 days to 11 years after fire), in comparison to the unburned control area. Effect of fire on the biological soil quality evaluated with QBS-ar index was analyzed using univariate and multivariate techniques. Our results showed a significant variation of QBS-ar values between burned areas and those never burned. The impact of fire on the QBS-ar index and the microarthropod community was higher in the areas burned twice. A relevant average dissimilarity of taxonomic groups was found between the control area and the area burned twice, but also between the control area and the one observed 3 months after the fire. The taxa that contributed more to the dissimilarity were Pseudoscorpiones and Diplopoda, which reduced their presence after fire. Our study shows that the QBS-ar index is a dependable method for monitoring the impact of fire on soil quality in forest ecosystems and indicates that edaphic microarthropods communities in these Mediterranean pine forests return to the before fire condition 11 years after fire. The QBS-ar index could therefore be a useful tool for monitoring forest ecosystem rehabilitation after fire.

Population collapse of a Gondwanan conifer follows the loss of Indigenous fire regimes in a northern Australian savanna

Colonialism has disrupted Indigenous socioecological systems around the globe, including those supported by intentional landscape burning. Because most disruptions happened centuries ago, our understanding of Indigenous fire management is largely inferential and open to debate. Here, we investigate the ecological consequences of the loss of traditional Aboriginal fire management on fire-exposed savannas on the Arnhem Plateau, northern Australia, using the fire-sensitive conifer Callitris intratropica as a bio-indicator. We contrast Kakadu National Park, where traditional Aboriginal fire management was severely disrupted during the early twentieth century following Aboriginal relocation to surrounding settlements, and an adjacent Aboriginal estate where traditional Aboriginal fire management endures. Since 2006, traditional Aboriginal fire management at this site has been overlaid by a program of broad-scale institutionalized burning in the early dry season, designed to reduce greenhouse emissions. Using remote sensing, field survey, and dendrochronology, we show that on the Aboriginal estate, C. intratropica populations depend on the creation of a shifting patch mosaic of long unburned areas necessary for the recruitment of C. intratropica. However, the imposition of broad-scale fire management is disrupting this population patch dynamic. In Kakadu, there have been extreme declines of C. intratropica associated with widespread fires since the mid twentieth century and consequent proliferation of grass fuels. Fire management in Kakadu since 2007, designed to increase the size and abundance of patches of unburned vegetation, has not been able to reverse the population collapse of C. intratropica. Our study demonstrates that colonial processes including relocation of Indigenous people and institutional fire management can have deleterious consequences that are nearly irreversible because of hysteresis in C. intratropica population dynamics.

Phenology Patterns and Postfire Vegetation Regeneration in the Chiquitania Region of Bolivia Using Sentinel-2

The natural regeneration of ecosystems impacted by fires is a high priority in Bolivia, and represents one of the country’s greatest environmental challenges. With the abundance of spatial data and access to improved technologies, it is critical to provide an effective method of analysis to evaluate changes in land use in the face of the global need to understand the dynamics of vegetation in regeneration processes. In this context, we evaluated the dynamics of natural regeneration through phenological patterns by measuring the maximal and minimal spectral thresholds at four fire-impacted sites in Chiquitania in 2019 and 2020, and compared them with unburned areas using harmonic fitted values of the Normalized Difference Vegetation Index (NDVI) and the Normalized Burn Ratio (NBR). We used two-way ANOVA test to evaluate the significant differences in the values of the profiles of NDVI and NBR indices. We quantified severity at the four study sites using the dNBR obtained from the difference between pre- and postfire NBR. Additionally, we selected 66 sampling sites to apply the Composite Burn Index (CBI) methodology. Our results indicate that NBR is the most reliable index for interannual comparisons and determining changes in the phenological pattern, which allow for the detection of postfire regeneration. Fire severity levels based on dNBR and CBI indices are reliable methodologies that allow for determining the severity and dynamics of changes in postfire regeneration levels in forested and nonforested areas.

Spatial patterns of unburned refugia in Siberian larch forests during the exceptional 2020 fire season

AbstractAimWildfire is an essential disturbance agent that creates burn mosaics, or a patchwork of burned and unburned areas across the landscape. Unburned patches, fire refugia, serve as carbon sinks and seed sources for forest regeneration in burned areas. In the Cajander larch (Larix cajanderi Mayr.) forests of north‐eastern Siberia, an unprecedented wildfire season in 2020 and little documentation of landscape patch dynamics have resulted in research gaps about the characteristics of fire refugia in northern latitude forests, which are warming faster than other global forest ecosystems. We aim to characterize the 2010 distribution of fire refugia for these forest ecosystems and evaluate their topographic drivers.LocationNorth‐eastern Siberia across the North‐east Siberian Taiga and the Cherskii‐Kolyma Mountain Tundra ecozones.Time period2001–2020.Major taxa studiedCajander larch.MethodsWe used Landsat imagery to define burned and unburned patches, and the Arctic digital elevation model to calculate topographic variables. We characterized the size and density of fire refugia. We sampled individual pixels (n = 80,000) from an image stack that included a binary burned/unburned, elevation, slope, aspect, topographic position index, ruggedness, and tree cover from 2001 to 2020. We evaluated the topographic drivers of fire refugia with boosted regression trees.ResultsWe found no substantial difference in fire refugia size and density across the region. The fire refugia size averaged 7.2 ha (0.09–150,439 ha). The majority of interior burned patches exceed the potential wind dispersal distance from fire refugia. Topographic position index and terrain steepness were important predictors of fire refugia.Main conclusionsUnprecedented wildfires in 2020 did not impact fire refugia formation. Fire refugia are strongly controlled by topographic positions such as uplands and lowlands that influence microsite hydrological conditions. Fire refugia contribute to postfire landscape heterogeneity that preserves ecosystem functions, seed sources, habitat, and carbon sinks.

Copiotrophic Bacterial Traits Increase With Burn Severity One Year After a Wildfire

Wildfire and burn severity influence soil microbial communities during post-fire recovery. If post-fire differences in microbial communities affect soil carbon (C) pool dynamics, altered microbial communities could influence the transition of forests from C sources to C sinks during ecosystem recovery. For example, fire may change the abundance of copiotrophic and oligotrophic bacteria, influencing the kinetic rates of soil C pools due to differences in C-acquisition strategies and nutrient requirements. We assessed differences in soil bacterial communities and soil C pool kinetics 1 year after a wildfire in a mixed-conifer forest in northern California, United States. We determined whether differences in bacterial communities and soil C pools were related to copiotrophic versus oligotrophic life history strategies. Specifically, we assessed bacterial community oligotrophy versus copiotrophy based on phyla relative abundances and predicted 16S gene copy numbers. We then determined whether these life-histories were correlated with C pool kinetic rates. We further determined whether C degradation metabolic pathways predicted using PICRUSt2 were related to C pool kinetics. We found that copiotrophic bacteria exhibited greater abundance in burned areas than unburned areas, evidenced by increases in 16S rRNA gene copy number and by taxonomic classifications. Furthermore, the abundance of predicted metabolic pathways associated with fast-cycling C compounds increased with severity, including carbohydrate, alcohol, and amine degradation pathways, suggesting increased copiotrophic metabolic strategies. In contrast, the abundance of metabolic pathways of slow-cycling aromatic C compounds did not change, indicating oligotrophic metabolic strategies did not increase. The kinetic rate of the active C pool was positively related to the copiotrophic metabolic pathway of alcohol degradation, and negatively related to oligotrophic pathways like aromatic compound degradation. The links between C pool kinetics and phylum-level life-strategy classifications were ambiguous. Overall, our results suggest that metabolic life-strategies are related to soil C pool kinetics and could have short- and long-term impacts on soil C persistence during post-fire recovery. In the short-term, increased copiotrophy could increase soil C effluxviarapid cycling of labile C pools. However, over the longer-term lower prevalence of oligotrophic strategies could allow aromatic compounds associated with pyrogenic C to accumulate, increasing stable soil C stocks.

Fire severity assessment on peatland vegetation diversity

Forest fires have a significant impact on peatland ecosystem, including its vegetation diversity. Several approaches applied for forest fire severity assessment are available in the literature. This study aimed to implement field-based and spatial-aware fire severity assessments and to compare both approaches. Peat swamp forests of Ogan Komering Ilir, South Sumatera Province, for field assessment and Siak, Riau Province, for spatial assessment were selected in this research. Field-based fire severity assessment used indicators of vegetation analyses (individual tree damages, burned vegetation severity, and diversity index), which were measured and analyzed from sample plots in both burned and unburned areas. Spatial analyses of fires severity assessment employed Sentinel-2 satellite imagery with Normalized Burn Ratio (NBR) approach. The research revealed a significant change in tree species diversity, indicating a lower diversity in burned areas than the ones in pristine fields. Magnitude of changes in diversity was influenced by fire severity levels in burned areas and pre-fire condition of burned areas. Spatial analyses indicated low to high fire severity with burned area estimation for each fire severity class. Both approaches have their own benefits and challenges. Field-based severity assessment is beneficial for a detailed assessment of fire damages and losses, whereas spatial analyses would be considered for a broader estimation of fire severity. Both assessments are mutually implemented. Field-based assessment can serve as a verification tool for spatial assessment.

Modeling the Susceptibility of Forest Fires Using a Genetic Algorithm: A Case Study in Mountain Areas of Southwestern China

Modeling fire susceptibility in fire-prone areas of forest ecosystems was essential for providing guidance to implement prevention and control measures of forest fires. Traditional models were developed on the basis of random selection of absence data (i.e., nonfire data from unburned areas), which could bring uncertainties to modeling results. Here, a new model with the genetic algorithm for Rule-set Production (GARP) algorithm and 10 environmental layers was proposed to process presence-only data in the susceptibility modeling of forest fires in Chongqing city. To do this, 70% of 684 fire occurrence data (479) during the period of 2000–2018 were applied to train the proposed model. And, 30% of these fire occurrence data (205) and the same amount of no-fire data (205) were emerged as validation dataset. The results showed that, for some environmental layers (i.e., distance to the nearest road, land cover, precipitation, distance to the nearest settlement, aspect, relative humidity, elevation, wind speed, and temperature), their P values were less than 0.05, indicating that these 9 environmental layers have significant influence on the spatial distribution of fire susceptibility in Chongqing city. On the contrary, with a higher P value (i.e., 0.126), the slope layer has an insignificant effect on fire susceptibility in the study area. Furthermore, the results of receiver operating characteristic analysis (ROC) showed that the proposed model has a good performance with an AUC value of 0.869, an accuracy value of 0.732, a sensitivity value of 0.59, a specificity value of 0.873, a positive predictive value of 0.823, and a negative predictive value of 0.681. This study revealed the validity of the proposed model in modeling the susceptibility of forest fires.

DOZER LINES INFLUENCE POST-FIRE PLANT COMMUNITY RECOVERY

As wildfires increase in extent and intensity and threaten local communities, active suppression tactics are becoming more common, including the creation of fire lines. Post-fire, these sites can become populated with non-native species and risk type conversion if native species recovery is lacking. Minimal research exists on the plant community trajectory of these mechanically disturbed sites. We studied the 32-Fire located east of Chico, CA. A fire line approximately 0.5 km long ranging in width from 6–12.2 m was created by a bulldozer. To assess plant recovery, we established plots in three pre-fire vegetation types: California Black Oak (Quercus kelloggii Newb.), Manzanita (Arctostaphylos manzanita Parry), and Wedgeleaf Ceanothus (Ceanothus cuneatus [Hook.] Nutt.) within three disturbance levels: burned, unburned (reference), and disturbed dozer line. Sites were sampled in 2018 (six-months post-fire) and in 2019 (18-months post-fire). In 2019, dozer line sites in the Manzanita and Wedgeleaf Ceanothus vegetation types did not have the dominant species found in similar unburned or burned sites. Across all vegetation types, dozer line sites had significantly higher average percent non-native species cover, compared with respective burned (P < 0.001, 95% C.I. = 33.2, 64.8) and unburned areas (P < 0.001, 95% C.I. = -77.2, -45.5). While unburned Wedgeleaf sites average non-native cover was 11% (SD = 9) in 2018 and 20% (SD = 5) in 2019, Wedgeleaf dozer line sites average non-native cover remained high between survey years at approximately 85%. Manzanita dozer line sites had average nonnative cover of 76% (SD = 16) and 57% (SD = 25) in 2018 and 2019, respectively, while unburned Manzanita had 9% (SD = 9) and 16% (SD = 16). Manzanita and Wedgeleaf Ceanothus species present on the study site are obligate seeders. Since neither species survived the implementation of the dozer line and no new recruitment of these species was observed, future recruitment of obligate seeders in these areas is unlikely. This suggests that dozer line sites with obligate seeders as dominant or co-dominant species are at risk of type conversion from native chaparral to annual grasslands dominated by non-native species.

Numerical simulation of the influence of high-pressure methane jet on the premixed ignition flame of constant volume bomb

Because of stringent emissions regulations, internal combustion engines using natural gas have become an important direction for the low-carbon development of the internal combustion engine industry. The combustion process of the internal combustion engines using natural gas involves the interaction between the gas jet and the flame. In this study, the process of a methane jet impinging on a methane premixed ignition flame inside a constant volume bomb was simulated by CONVERGE software, and the changes in combustion and flow within the jet impinging flame flow field were investigated. A k-value was defined by the ratio of jet velocity to laminar combustion velocity, and k is found to be inversely proportional to the maximum value of the rate of change of flame surface area A, and k is proportional to the peak value of the rate of change of turbulent kinetic energy. It was also found that the jet intensifies the initial premixed flame under three k-value operating conditions, and the OH-based change rate within the flow field increases abruptly by a factor of 4–9 after the jet is added. The process of jet impingement on the flame is divided into three stages according to the mutual position of the jet and the premixed flame surface, and the evolution of the flame structure and the combustion behavior in the flow field under different stages are analyzed in the article. It was found that the initial premixed flame induced by the jet became unstable in the second stage and a stable turbulent combustion flame was formed in the third stage. Analysis of the parameter changes at three points on the axial direction of the jet nozzle revealed that the jet disturbance at the near-nozzle end was too large to form stable combustion. Meanwhile, at the far-nozzle end, the jet disturbance formed a vortex volume suitable for combustion, and turbulent combustion was produced by the heat-induced by the flame moving toward the unburned area and the vortex volume disturbance.

The Latent Dirichlet Allocation model applied to airborne LiDAR data: A case study on mapping forest degradation associated with fragmentation and fire in the Amazon region

Abstract LiDAR data are being increasingly used to provide a detailed characterization of the vertical profile of forests. This characterization enables the generation of new insights on the influence of environmental drivers and anthropogenic disturbances on forest structure as well as on how forest structure influences important ecosystem functions and services. Unfortunately, extracting information from LiDAR data in a way that enables the spatial visualization of forest structure, as well as its temporal changes, is challenging due to the high dimensionality of these data. We show how the Latent Dirichlet Allocation model applied to LiDAR data (LidarLDA) can be used to identify forest structural types and how the relative abundance of these forest types changes throughout the landscape. The code to fit this model is made available through the open‐source r package LidarLDA in github. We illustrate the use of LidarLDA both with simulated data and data from a large‐scale fire experiment in the Brazilian Amazon region. Using simulated data, we demonstrate that LidarLDA accurately identifies the number of forest types as well as their spatial distribution and absorptance probabilities. For the empirical data, we found that LidarLDA detects both landscape‐level patterns in forest structure as well as the strong interacting effect of fire and forest fragmentation on forest structure based on the experimental fire plots. More specifically, LidarLDA reveals that proximity to forest edge exacerbates the impact of fires, and that burned forests remain structurally different from unburned areas for at least 7 years, even when burned only once. Importantly, LidarLDA generates insights on the 3D structure of forest that cannot be obtained using more standard approaches that just focus on top‐of‐the‐canopy information (e.g. canopy height models based on LiDAR data). By enabling the mapping of forest structure and its temporal changes, we believe that LidarLDA will be of broad utility to the ecological research community.

Short-Interval, Severe Wildfires Alter Saproxylic Beetle Diversity in Andean Araucaria Forests in Northwest Chilean Patagonia

The occurrence of short-interval, severe wildfires are increasing drastically at a global scale, and appear as a novel phenomenon in areas where fire historically returns in large time lapses. In forest ecosystems, these events induce drastic changes in population dynamics, which could dramatically impact species diversity. Here, we studied the effect on diversity of recent short-interval, severe wildfires (SISF), which occurred in rapid succession in the summers of 2002 and 2015 in Chilean Northern Patagonian Araucaria–Nothofagus forests. We analyzed the diversity of deadwood-dependent (i.e., saproxylic) and fire-sensitive beetles as biological indicators across four conditions: 2002-burned areas, 2015-burned areas, SISF areas (i.e., burned in 2002 and again in 2015), and unburned areas. Saproxylic beetles were collected using window traps in 2017 to 2019 summer seasons. To investigate the mechanisms underpinning the fire-related disturbance of the assemblage, we evaluated the effects of post-fire habitat quality (e.g., dead wood decomposition) and quantity (e.g., burned dead wood volume and tree density) on the abundances and species richness of the entire assemblage and also multiple trophic groups. Compared with the unburned condition, SISF drastically reduced species richness, evenness, and Shannon’s diversity and altered the composition of the saproxylic beetle assemblages. The between-condition variation in composition was accounted for by a species replacement (turnover) between SISF and 2015-burned areas, but both species replacement and extinction (nestedness) between SISF and unburned areas. Dead wood decomposition and tree density were the variables with the strongest effects on the abundance and species richness of the entire saproxylic beetle assemblage and most trophic groups. These results suggest that SISF, through degraded habitat quality (dead wood decomposition) and quantity (arboreal density), have detrimental impacts on diversity and population dynamics of saproxylic beetle assemblages. Therefore, habitat loss is a central mechanism underpinning fire-related biodiversity loss in these forest ecosystems.

Post-fire temporal trends in soil properties and revegetation: Insights from different wildfire severities in the Hengduan Mountains, Southwestern China

The Hengduan Mountains are frequently disturbed by high-risk wildfires. However, insufficient information is available on post-fire temporal trends in soil properties and revegetation of areas with various fire severities. To address this gap, two adjacent wildfires that occurred in 2010 and 2018 were selected. The study areas were divided into low (LS), moderate (MS), high (HS) severity fire burned areas and unburned (as control, UB) areas. Temporal trends in soil properties (0–5 cm): soil water repellency, saturated hydraulic conductivity, bulk density, soil moisture content (SMC), and soil organic matter content (SOM) were measured by in-situ and laboratory tests at 1, 7, 19 months (1MAF, 7MAF, 19MAF), and 10 years after the fires (10YAF), respectively. Temporal trends in post-fire revegetation were evaluated via on-ground surveys and remote sensing images. The statistical analysis results showed that the HS and MS fires significantly altered the soil properties and resulted in a remarkable decrease in vegetation coverage, leading to substantial bare soil 1MAF. The soil properties of the HS and MS fire burned areas had not recovered to normal due to the significantly decreased SOM and SMC 7MAF and 19MAF, and they had recovered to the pre-fire level 10YAF. The first three years following the fires were a crucial period for revegetation, during which the shrubs and bryophytes rapidly recovered, causing a rapid increase in vegetation coverage, and a corresponding sharp decrease in the coverage of bare soil. The incompletely recovered pines of the HS and MS areas provisionally resulted in a degeneration of the forest stand within a decade after the fire. We conclude that the fire-affected soil properties can return to normal within 10 years, and complete recovery of the vegetation requires a longer period than a decade. These results may provide scientific guidance for post-fire management of the burned area.

Supervised Machine Learning Approaches on Multispectral Remote Sensing Data for a Combined Detection of Fire and Burned Area

Bushfires pose a severe risk, among others, to humans, wildlife, and infrastructures. Rapid detection of fires is crucial for fire-extinguishing activities and rescue missions. Besides, mapping burned areas also supports evacuation and accessibility to emergency facilities. In this study, we propose a generic approach for detecting fires and burned areas based on machine learning (ML) approaches and remote sensing data. While most studies investigated either the detection of fires or mapping burned areas, we addressed and evaluated, in particular, the combined detection on three selected case study regions. Multispectral Sentinel-2 images represent the input data for the supervised ML models. First, we generated the reference data for the three target classes, burned, unburned, and fire, since no reference data were available. Second, the three regional fire datasets were preprocessed and divided into training, validation, and test subsets according to a defined schema. Furthermore, an undersampling approach ensured the balancing of the datasets. Third, seven selected supervised classification approaches were used and evaluated, including tree-based models, a self-organizing map, an artificial neural network, and a one-dimensional convolutional neural network (1D-CNN). All selected ML approaches achieved satisfying classification results. Moreover, they performed a highly accurate fire detection, while separating burned and unburned areas was slightly more challenging. The 1D-CNN and extremely randomized tree were the best-performing models with an overall accuracy score of 98% on the test subsets. Even on an unknown test dataset, the 1D-CNN achieved high classification accuracies. This generalization is even more valuable for any use-case scenario, including the organization of fire-fighting activities or civil protection. The proposed combined detection could be extended and enhanced with crowdsourced data in further studies.

Effects of a megafire on the arbuscular mycorrhizal fungal community and parameters in the Brazilian Cerrado ecosystem

Aim of the study: To evaluate the effects of a mega-fire on the arbuscular mycorrhizal fungi (AMF) community and parameters in soils under Cerrado vegetation. Study area: Chapada dos Veadeiros National Park, Goiás, Brazil. This site suffered the biggest fire in its history on October 10, 2017, with an affected area of 66,000 ha. Material and methods: We analyzed AMF spore density, roots’ mycorrhizal colonization rate, easily extractable glomalin (EEG), as well as the AMF genera present. These parameters were evaluated in burned and unburned areas of five common phytophysiognomies of the region. Main results: Fire presence immediately affected the mycorrhizal community parameters in Cerrado soils, which tended to increase afterwards. The presence of AMF genera did not differ between burned and unburned areas, with Acaulospora, Claroideglomus, Diversispora, Glomus, Funneliformis, Sclerocystis, and Gigaspora being present. The recovery of AMF community conditions in the Cerrado after fire events could also be observed in the mycorrhizal parameters evaluated, as the values of spore density, roots’ mycorrhizal colonization rate, and EEG were similar in the burned and unburned areas. Research highlights: AMF diversity, and especially their community parameters, show great recovery after fire events, since they are crucial in processes like nutrient cycling and soil aggregation.

Natural recovery from fire disturbance is more favorable than assisted recovery for the restoration of soil nematode-trapping fungi

A fire is usually considered a severe disturbance factor in the environment. Globally, rising temperatures and increasing human activities have intensified the severity and frequency of fire incidents, and research on post-fire recovery has inevitably become an important focus for ecologists. In terms of the restoration of burned areas, there are usually two primary approaches: natural recovery and assisted recovery. However, very few relevant studies have systematically compared these recovery alternatives, suggesting which one is more favorable to the overall restoration of an ecosystem, especially to the soil microbes that function as indispensable components of ecosystems. In this study, the restoration of soil nematode-trapping fungi (NTF) in natural and assisted recovery environments was compared. The results showed that although the NTF community structures differed among the sample sites, the counts and diversity of the NTF communities in the upper and lower soil layers in the natural recovery area were higher than those in the assisted recovery and unburned control areas. These findings suggest that artificial efforts to help ecosystem recovery after fire negatively affect the speed and quality of soil NTF community recovery. Instead, natural recovery appears to be a more suitable land management choice after fire disturbance.

Post-Fire Effects on the Globally Imperiled Chapin Mesa Milkvetch (Astragalus schmolliae), 2001–2019

Chapin Mesa milkvetch (Astragalus schmolliae) is an endemic, obligate pinon-juniper̴ woodland species that occupies approximately 2500 ha in southwest Colorado. In 2002 a crown fire burned 38% of the known distribution in Mesa Verde National Park. Initially, Chapin Mesa milkvetch (CMM) responded positively to the 2002 burn, increasing in density compared to unburned areas. Nine years post-fire (2011), the density in burned areas was nearly twice that of unburned transects. By 2013, the pattern had reversed, and by 2019, the juvenile and adult population in the burned area was reduced to half that of unburned (0.046 plants/m2 vs. 0.089 plants/m2). Recruitment of CMM in burned areas in 2019 was near zero: 4 seedlings in 63 burned transects vs. 6079 seedlings in 105 unburned transects. The downward trend in CMM density in the burn is likely associated with intensified competition from the dense grass cover. Prior to the burn, the grass cover in the to-be-burned area was qualitatively similar to that in present day unburned areas, which is 15%, almost exclusively muttongrass (Poa fendleriana), a shallow-rooted bunch grass. In 2019, cheatgrass (Bromus tectorum) and western wheatgrass (Pascopyrum smithii), seeded in 2002, dominated the cover in the burn, averaging 45% cover, collectively. Management practices that assist the recovery of burned pinon-juniper̴ woodland (and therefore CMM), as well as preserving the remaining old-growth pinon-juniper̴ stands, are likely key to CMM long-term survival.

Fire influences reproductive outcomes by modifying flowering phenology and mate-availability.

A recent study posited that fire in grasslands promotes persistence of plant species by improving mating opportunities and reproductive outcomes. We devised an investigation to test these predicted mechanisms in two widespread, long-lived perennials. We expect fire to synchronize flowering, increase mating and boost seed set. We quantified individual flowering phenology and seed set of Liatris aspera and Solidago speciosa for 3yr on a preserve in Minnesota, USA. The preserve comprises two management units burned on alternating years, allowing for comparisons between plants in burned and unburned areas within the same year, and plants in the same area across years with and without burns. Fire increased flowering synchrony and increased time between start date and peak flowering. Individuals of both species that initiated flowering later in the season had higher seed set. Fire was associated with substantially higher flowering rates and seed set in L. aspera but not S. speciosa. In L. aspera, greater synchrony was associated with increased mean seed set. Although fire affected flowering phenology in both species, reproductive success improved only in the species in which fire also synchronized among-year flowering. Our results support the hypothesis that reproduction in some grassland species benefits from fire.

Sensitivity of Multifrequency Polarimetric SAR Data to Postfire Permafrost Changes and Recovery Processes in Arctic Tundra

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.

Canopies, the Final Frog-tier: exploring responses of a specialist treefrog to prescribed fire in a pyrogenic ecosystem

BackgroundPine flatwoods of the southeastern United States were shaped by frequent fires. Land managers use prescribed fires to control fuels but also to restore historical fire dynamics. Broad outcomes of this practice are well-understood, but impacts on many organisms are still being explored. Frogs, for example, have upland and wetland requirements, limited mobility, and skin susceptible to desiccation. Treefrogs spend most of their lives in uplands away from water. When fire approaches, animals may escape to an unburned area, shelter in place, or be killed by the fire. We examined which of these mechanisms is the prevailing short-term response for a specialist treefrog in a pyrogenic flatwood system.ResultsWe assessed the short-term impacts of prescribed fire on the dynamics of an upland flatwood specialist, the pinewoods treefrog Dryophytes femoralis, using a replicated before-after-control-impact field experiment. We set pipes as treefrog refugia at 3 m, 6 m, 9 m, and 9+ m in 12 pine trees spread evenly across two treatments: reference trees in units burned in 2020 and trees in units with 2021 prescribed fire. Prescribed fires occurred on 16 April and 21 July 2021. Every 2 weeks between 5 March and 5 September, we checked pipes for frogs and assigned them unique color marks. We observed 78 individuals with 199 additional recaptures. We modeled abundance (as raw counts), survival, and vertical movement using mark-recapture methods, multi-state, and mixed linear models with a Bayesian framework. Survival and recapture were comparable among prescribed fire treatments, but abundances and movement probability varied. Frogs in trees in areas burned during the study were more likely to stay in place and less likely to descend to lower heights. We observed more frogs in trees after a 2021 fire compared to reference trees.ConclusionsThe prevailing mechanism for resiliency to fire for pinewoods treefrogs was migration up large pines, then likely recolonization to lower vegetation layers when plants regreen post-fire. This substantiates conclusions from other works that the integrity of mature pines is key to sustaining native biodiversity. Future work and management should consider the three-dimensional structure of habitat when developing burn prescriptions and study designs.

Geospatial assessment of vegetation condition pre-wildfire and post-wildfire on Luštica (Montenegro) using differenced Normalized Burn Ratio (dNBR) index

Wildfire is one of the most dangerous environmental stressors in most vegetation zones worldwide. Determining and monitoring this stressor is important because of the disturbances that occur during the burning of biomass in ecosystems, as well as because of the damage or suffering of organisms. In the last decade, a greater number of wildfires and burnt areas were recorded in Southern Europe and Montenegro. Therefore, it is important to develop optimal methodology and models to help in better management of forest protection against wildfire. The spatial component in firefighting plays a significant role in management. In this context, Remote Sensing and Geographic Information Systems (GIS) come to the fore, which analyze spatial data and turn it into useful information - models applied in practice. The study aims to geospatial assess condition of vegetation pre-wildfire and post-wildfire in study area of the Luštica peninsula in Montenegro during the summer of 2017. Open and publicly available Sentinel 2 satellite was used. The scaled index differenced Normalized Burn Ratio (dNBR) of burned vegetation was applied as an indicator for assessing the state of vegetation after a wildfire in the open source software Quantum GIS (QGIS). The results of the damage assessment of the burned area based on the applied scaled index reveal that the category of low severity occupies an area of 335.86 ha (7%), moderately-low severity 250.13 ha (5%), moderately-high severity 406.22 ha (8%), high severity 238.03 ha (5%). The unburned areas occupy an area of 3624.95 ha (75%). This study contributes to assessing vegetation conditions and other accompanying activities pre-wildfire and post-wildfire using modern open-source geospatial tools.