Burned Plots Research Articles

Differential effects of fire on the occupancy of small mammals in neotropical savanna-gallery forests

Fire is a global disturbance that has a strong influence on biodiversity. Seasonal fires are common in neotropical savannas of South America, yet few studies have analyzed how the fauna of these habitats and nearby forests respond to fire. We evaluated the effects of fire on the community of non-volant small mammals in the Colombian llanos by comparing their populations in both unburned (no record of fire for the last 20 years) and recently burned areas (three years after the last fire event). Vegetation structure was monitored at 240 plots. We used hierarchical single-season occupancy modeling to determine potential effects of fire on small mammal detection and occupancy. Our results indicate that fire has long-term effects on plant diversity and richness, as well as on the species composition. Three years after the last fire event, the average richness of plant species at burned sites was lower than at unburned sites. Fire also affected the distribution of vegetation strata leading to an increased abundance and diversity of plants in the ground and herbaceous strata in burned plots. The hierarchical models indicate that mammals’ occupancy tracks these changes in vegetation structure. However, the effect of fire was not consistent among species. We found that fire may restrict (Didelphis marsupialis), promote (Zygodontomys brevicauda) or have no impact (Oecomys sp.) on the mammals’ distribution depending on how each species uses the strata that disappeared because of fire. These findings provide evidence toward wildfire prevention for biodiversity conservation in fire-sensitive ecosystems of northern South America.

Fire slightly decreases the competitive effects of a thorny cushion shrub in a semi‐arid mountain steppe in the short term

AbstractQuestionsStudies in alpine environments have highlighted dominant facilitative effects of cushion species for diversity. Many fewer studies have assessed the effects of cushion shrubs in drier and less cold mountain habitats and how these effects vary within the shrub canopy and with increasing drought stress with exposure and disturbance by fire.LocationA mountain steppe of the Golestan National Park in the semi‐arid climate of northeast Iran.MethodsWe quantified the cover of understorey species at the center and edge of the canopy of the thorny cushion shrub Onobrychis cornuta and in paired open areas, in north and south exposures and unburned and burned plots, two years after a fire. Soil chemical variables and moisture were measured in treatments. We quantified cushions’ center and edge effects on understorey species cover with the Relative Interaction Index (RII). Treatment effects on RII cover were analyzed with generalized linear mixed‐effects models (GLMM) and species composition with Correspondence Analysis.ResultsIn unburned plots, competition for cover was very high at cushion centers and strongly decreased at cushion edges. Exposure stress did not affect competition in unburned plots. Fire slightly decreased competition but only at center cushion shrub position and at south exposure. Species composition was mostly affected by exposure and fire treatments, although there was subtle variation in species composition among patches due to fire. Cushion position, fire and exposure treatments affected soil moisture and chemical variables, but soil changes did not explain cushion effects on understorey cover and their variations along treatments.ConclusionsThe effects of the cushion shrub were highly negative and in particular at cushion center, likely due to interference and competition for light in a dry and not too cold environment. Fire only slightly decreased competition in the short term, likely due to the delayed response of understorey species to disturbance induced by fire.

Assessing the fire resilience of the savanna tree component through a functional approach

Changes in savanna's fire regimes, either through fire suppression or through an increase in fire frequency, can negatively affect their resilience. We evaluated the extent to which the aboveground biomass, diversity (taxonomic and functional) and resilience (functional redundancy and functional response indices) of savanna tree communities differ between burned and unburned plots. Burned plots experienced two fire events over the ten-years prior to sampling, while unburned plots experienced fire suppression over the same time period. We found that aboveground biomass was 40% smaller in burned plots, indicating that fire regimes must be included as a source of variation in models estimating the potential of savannas to store carbon. Burned plots had a higher functional diversity of vegetative traits but a smaller functional diversity of reproductive traits, indicating that generalizations about the effect of fire on tree functional diversity should be viewed with caution. Periodic fires can benefit savanna tree biodiversity by maintaining the balance between light-demanding and shade-tolerant species but can also increase the dominance of species with less specialized reproductive traits that do not rely on animal interactions. Burned plots had slightly lower functional redundancy but similar functional response diversity compared to unburned plots, suggesting that both communities harbor tree species that might respond positively or negatively to fire and, therefore, will be able to maintain the ecosystem functions considered under a future scenario of fire-suppression or increased fire frequency. Therefore, a longer-term fire suppression (>10 years) or a return fire interval of less than 4 years may be necessary to reduce the resilience of the savanna tree component, considering the ecosystem functions analyzed in this study.

High-severity wildfire reduces richness and alters composition of ectomycorrhizal fungi in low-severity adapted ponderosa pine forests

Ponderosa pine (Pinus ponderosa) forests are increasingly experiencing high-severity, stand-replacing fires. Whereas alterations to aboveground ecosystems have been extensively studied, little is known about soil fungal responses in fire-adapted ecosystems. We implement a chronosequence of four different fires that varied in time since fire, 2 years (2015) to 11 years (2006) and contained stands of high severity burned P. ponderosa in eastern Washington and compared their soil fungal communities to adjacent unburned plots. Using Illumina Miseq (ITS1), we examined changes in soil nutrients, drivers of species richness for ectomycorrhizal (plant symbionts) and saprobic (decomposers) fungi, community shifts, and post-fire fungal succession in burned and unburned plots. Ectomycorrhizal richness was 43.4% and saprobic richness 12.2% lower in the burned plots, leading to long-term alterations to the fungal communities that did not return to unburned levels, even after 11 years. Differences in the post-fire fungal community were driven by pyrophilous, “fire-loving” fungi, including the ectomycorrhizal Ascomycete genera Pustularia and Wilcoxina, and the saprobic Basidiomycete genus Geminibasidium. Ectomycorrhizal and saprobic fungi were intimately linked to the soil environment: depth of the organic matter, total carbon, total nitrogen, and their interaction with fire predicted ectomycorrhizal richness. Whereas total carbon, time since fire, treatment, and the interaction between time since fire and treatment predicted saprobic richness. We conclude that high-severity wildfires lead to lower ectomycorrhizal richness and significantly altered ectomycorrhizal and saprobic communities in fire-adapted ecosystems, selecting resilient and fire-adapted species, such as W. rehmii and Geminibasidium sp., thus initiating post-fire succession.

Matching methods to quantify wildfire effects on forest carbon mass in the U.S. Pacific Northwest.

Forest wildfires consume and redistribute carbon within forest carbon pools. Because the incidence of wildfires is unpredictable, quantifying wildfire effects is challenging due to the lack of prefire data or controls from experiments over a large landscape. We explored a quasi-experimental method, propensity score matching, to estimate wildfire effects on aboveground forest woody carbon mass in Washington and Oregon, United States. Observational data, including national forest inventory plot measurements and satellite imagery metrics, were utilized to obtain a control set of unburned plots that are comparable to burned plots in terms of environmental conditions as well as spatial locations. Three matching methods were implemented: propensity score matching (PSM), spatial matching (SM), and distance-adjusted propensity score matching (DAPSM). We investigated if propensity score matching with and without spatial adjustment led to different outcomes in terms of (1) balance in covariate distributions between burned and control plots, (2) mean carbon mass obtained from the selected control plots compared to burned and all unburned plots, and (3) estimates of wildfire effects by burn severity. We found that PSM and SM, which use only the environmental covariate set or the spatial distance for estimating propensity scores, respectively, did not appear to produce a comparable set of control plots in terms of the estimated propensity scores and the outcomes of mean carbon mass. DAPSM was the preferred method both in balancing the observed covariates and in dealing with unobservable confounding variables through spatial adjustment. The average wildfire effects estimated by DAPSM showed clear evidence of redistribution of carbon among aboveground woody pools, from live to dead trees, but the consumption of total woody carbon by wildfire was not substantial. Only moderate burn severity led to significant reduction of total woody carbon mass across Washington and Oregon forests (64% of control plots remained on average). This study provides an applied example of a quasi-experimental approach to quantify the effects of a natural disturbance for which experimental settings are unavailable. The study results suggest that incorporating spatial information in addition to environmental covariates would yield a comparable set of control plots for wildfire effects quantification.

Assessment of species diversity and distribution of woody species on selected plots in Olokemeji Forest Reserve, Ogun State, Nigeria

The Assessment of forest species composition and species diversity is essential in understanding the status of tree population and diversity for conservation purpose. Olokemeji forest reserve is situated in the lowland rain forest of south-western Nigeria and it occupies a total land area of 58.88 km2 . Six study plots of 50m2 each were randomly selected and designated as Frequently Burnt Plot 1, Frequently Burnt Plot 2, Harvested Plot, Unharvested Unburnt Plot, Arable Plot 1 and Arable Plot 2 for the purpose of assessment of species diversity and distribution of woody species. Seven species of trees were identified belonging to five families. One hundred and eighty two stands were enumerated, with Unharvested Unburnt Plot having the highest number of trees at 50. The dominance index for the woody flora was 1 in Frequently Burnt Plot 1 and 2 as well as Arable Plot 1 and 2 except for the Harvested Plot that had the lowest (0.29) while the Unharvested Unburnt Plot had 0.75. Highest species richness was recorded at the Harvested Plot at 0.71. The species diversity in Harvested Plot was low (1.54), while it was extremely low in Unharvested Unburnt Plot (0.43). Evenness index was lowest in the Unharvested Unburnt Plot at 0.43. Tectona grandis had the highest relative importance value in the Frequently Burnt Plot 1. The low species richness and species diversity is a direct indication of anthropogenic interference in the study plots and the forest reserve; this requires urgent mitigation to prevent a total loss of its structure and function as expected of a forest reserve.
 Keywords: Species, Diversity, Evenness, Anthropogenic, Forest, Dynamics

Deeper burning in a boreal fen peatland 1‐year post‐wildfire accelerates recovery trajectory of carbon dioxide uptake

AbstractPeatlands contain a globally significant store (30%) of soil carbon (C). Within the Canadian Western Boreal Plains, where peatlands are a dominant feature, the climate is becoming warmer and drier, coupled with an increase in forest fire incidence. The response of peatlands to forest fire is likely to be a key determinant in the future of C storage of Boreal peatlands. This study examined the impacts of fire on key environmental controls on CO2 fluxes at the plot‐scale (using static chambers) between burned and unburned understory vegetation throughout the growing season of 2017 in a treed fen impacted by the Horse River wildfire (2016) in Fort McMurray, Alberta, Canada. Both gross ecosystem productivity (GEP) and total respiration (Rtot) were less at burned plots compared with unburned. Temporal patterns varied between the plots, where both component of CO2 fluxes at the unburned plots were largest in June, whereas at the burned plots, CO2 fluxes peaked in the late growing season. GEP and net ecosystem exchange (NEE) showed a positive relationship with depth of burn, with the deepest burned areas showing significantly greater CO2 uptake, coinciding with both increased bioavailable phosphorus and greater moss recolonization. At the unburned plots, soil temperature was a dominant control on CO2 fluxes. This work demonstrates the importance of the depth of burn to post‐fire carbon fluxes and how a knowledge of burn severity and depth can inform understanding of the recovery trajectory of northern peatlands following fire disturbance.

Post-fire recruitment and resprouting of a threatened montane eucalypt

Changing climate is predicted to result in increased frequency and size of wildfires in south-eastern Australia. With increasing area burnt there is increased potential for entire species distributions to be burnt in a single fire event. This is particularly the case for range-restricted threatened species. Eucalyptus canobolensis (L.A.S.Johnson & K.D.Hill) J.T.Hunter is restricted to Mount Canobolas, New South Wales, Australia. In 2018, the majority of the E. canobolensis population was burnt by wildfire. One-year post-fire, we measured recruitment, resprouting and mortality of E. canobolensis. At higher fire severities, smaller trees were more likely to resprout from their bases only, as their stems were killed (i.e. ‘top kill’). Seedling regeneration only occurred in burnt plots. Our study demonstrates that E. canobolensis has a fire response typical of many eucalypts, characterised by seedling recruitment and larger trees resprouting epicormically, even after high-severity fire. Nevertheless, E. canobolensis response to repeat and short-interval fire remains unknown, and smaller trees appear to be vulnerable to top kill. Although much of Australia’s flora can respond to fire, this response is likely to be challenged as fire extents increase, especially if this is combined with increasing fire severity and/or frequency. These changes to the fire regime are a particular threat to species with restricted distributions.

Influence of experimental fires on mesofauna communities (Collembola and Acari) of two types of meadows

The impact of prescribed fires in grasslands on soil mesofauna was studied in the field experiment. The study was carried out on two types of meadows: on mineral (meadow I) and organic soils (meadow II), near Warsaw (52o10’N; 20o50’E). In November 2007 sampling plots, 1 m2 in size were chosen at random and burned. Soil samples were taken just after fire and in April, July and November, 2008 to the depth of 10 cm from unburned plots (control), at the edge of fire and in burned plots. The soil mesofauna was extracted from soil samples in the Tullgren apparatus. There were not found any effects of prescribed fires on mesofauna densities. However, a slight increase of mesofauna abundance was observed on burned areas 12 months after experimental fires on the meadow I and decrease on the meadow II. Just after fire, on burned areas, only euedaphic species of Collembola were present among mites communities dominated Oribatida, with thick cuticule.

Historical Fire and Ventenata dubia Invasion in a Temperate Grassland

Ventenata (Ventenata dubia L.) is an invasive annual grass that has rapidly expanded its range across temperate grassland and shrub-steppe ecosystems in western North America. However, there is little published regarding its ecology, especially its relationship with fire on rangelands. The objective of this study was to examine the effect of fire on ventenata invasion in the Pacific Northwest Bunchgrass (PNB) Prairie. Given the influence of fire on the invasion of other annual grasses such as cheatgrass (Bromus tectorum L.), we expected that fire would facilitate the spread and increase in abundance of ventenata. In addition, we considered that annual variation in precipitation might mask the effect of fire and drive the year-to-year variation in production of ventenata. Therefore, we resampled 56 plots in 2015 and 2016 where frequency and foliar cover of ventenata had been recorded in 2008 and where 12 of these plots had burned in the past 15 yr. We then compared ventenata abundance (frequency and foliar cover) between burned and unburned plots within each sampling yr (2008, 2015, and 2016), as well as the change in abundance over time. Our data revealed that ventenata frequency and cover increased on all plots. However, there was not significantly higher abundance in burned plots in any of the sampling years. In addition, ventenata abundance did not increase more in burned plots over time. Our findings suggest that, unlike cheatgrass, fire may not be a driving factor in the spread and increase of ventenata across the PNB Prairie. This finding has important implications for the management and control of ventenata, as well as the conservation of the PNB Prairie.

Structural resistance and functional resilience of the Chaco forest to wildland fires: an approach with MODIS time series

AbstractForests have resistance that allows them to resist fires without changing to another state, and resilience that allows them to recover after disturbance. These properties are determined by many structural and functional determinants that interact between them. Despite the importance of structural resistance and functional resilience to wildland fires, few studies have evaluated the combined effect that structural and functional determinants have on them. Our goal was to assess the structural resistance and functional resilience to fire using remote sensing information. We specifically assessed the combined effect of pre‐fire vegetation characteristics, burn severity, and post‐fire precipitation on forest structural resistance and functional resilience to fire. Eighty‐five forest plots of 250 m × 250 m were selected in areas that burned in 2003. For each burned plot, a paired unburned control plot of 250 m × 250 m was selected outside the burned areas. We measured burn severity and post‐fire precipitations (2004–2011). We analysed MODIS time series in order to calculate the following pre‐ (2002) and post‐fire (2011) phenological parameters: minimum level of photosynthetic activity per year; maximum level of photosynthetic activity per year; length of growing season per year; integral of annual photosynthetic activity; relative seasonality of photosynthetic activity. Also we detected plots that changed into a shrubland eight years after the fire. Fifty three per cent of burned plots changed from forest into a shrubland state. Results show that the forest structural resistance to fire depends on the balance between the level of severity and the parameters related to pre‐fire aboveground net primary production. The impact of pre‐fire vegetation characteristics on functional resilience ability was driven by burn severity and it’s interactions with pre‐fire productivity and seasonality. Results suggest that changes in forest species composition and aboveground net primary production reduced forest structural resistance and functional resilience to fire.

Determinants of fire intensity in working landscapes of an African savanna

BackgroundAn often cited rule of savanna fire ecology is that early dry-season fires burn less intensely than late dry-season ones; however, few studies base their experimental design on the practices of fire managers in working landscapes. The objective of this research was to study the factors influencing fireline intensity, combustion, and patchiness for a West African savanna under common vegetation and land management practices. We conducted 97 experimental fires by selecting burn plots and seasonal timing (early, n = 33; middle, n = 44; or late, n = 20) based on local practices in a typical working landscape. We collected data for biomass consumed, grass type, scorch height, speed of fire front, visual efficiency (patchiness), fire type, and ambient air conditions. We used multiple regression analysis to determine the key factors affecting fire intensity.ResultsMean intensity was lowest for the middle season fires and highest for the late season fires. Minimum fire intensity increased over the fire season except for a sharp drop mid season, while maximum intensity progressively decreased. Seasonal values were highly variable. Fire intensity was moderately positively correlated with scorch height and more modestly correlated with visual efficiency, but only marginally correlated with combustion completeness. Average combustion completeness increased weakly as the dry season progressed. Intensity of back-fires was determined primarily by seasonal timing and the associated ambient humidity and wind and, to a lesser extent, grass characteristics. Head-fire intensity was only feebly responsive to wind speed.ConclusionsWe found that, at the peak time of West African savanna burning, the intensity of fires decreased. Fire behaviors in working West African landscapes were more dependent on fire type and wind than seasonality. Finally, we found that fire intensity values were lower than those reported elsewhere due to the more representative conditions of the fire setting (under lower afternoon winds) and fuel loads (lower biomass on working landscapes). Future research should focus on the ecological impacts of fires set under such conditions on growth and death rates of savanna trees.

Burn severity and soil chemistry are weak drivers of early vegetation succession following a boreal mega‐fire in a production forest landscape

AbstractQuestionsDo burn severity and soil chemistry drive species and trait composition on recently burned clear‐cuttings? Does the spatial distribution of common, easily dispersed colonizers vary with distance to fire perimeter?LocationA 13,000 ha production forest landscape in boreal southern Sweden burned in a wildfire in 2014.MethodsVascular plants and bryophytes were recorded in permanent plots on clear‐cuts two and five years following fire, covering a burn severity gradient. Soil carbon content (reflecting burn severity), pH and nutrients were measured at plot level. Trait data were retrieved from the BIEN and LEDA databases and analyzed using community‐weighted mean (CWM) trait values. Statistical analyses included generalized linear mixed models (GLMMs), non‐metric multidimensional scaling (NMDS) and multivariate ANOVA.ResultsLow burn severity resulted in higher frequency of legacy species (e.g.Vaccinium myrtillus), while high burn severity facilitated colonizing species (e.g.Senecio sylvaticus). Vegetation varied with soil chemistry, expressed through pH. Species composition changed between years and deviated from unburned clear‐cuts. After five years the most common taxa on burned plots were the vascular plantsChamaenerion angustifolium,Betulaspp. andPopulus tremulaand the bryophytesCeratodon purpureusandPolytrichum juniperinum. CWM specific leaf area (SLA) decreased markedly with time and root buds increased with total carbon content in the soil (i.e., toward less severely burned plots), while soil pH was not associated with any studied trait.Chamaenerion angustifoliumdecreased with distance to the fire perimeter, whileCeratodon purpureusincreased.ConclusionsBurn severity and soil pH weakly drive vegetation dynamics in the early phase following fire on clear‐cuts, indicating a large influence of stochastic processes. Deciduous trees are common already after five years and their further expansion will affect light and nutrient availability. To understand future vegetation trajectories on burned clear‐cuts, studies need to incorporate the light factor and links between tree species’ identity and soil nutrient availability.

Effects of prescribed burning on rodent community ecology in Serengeti National Park

A study on the effects of prescribed burning on rodent community ecology was conducted in Serengeti National Park, Tanzania. The study aimed at generating ecological knowledge about the changes in rodent communities when areas of the park are intentionally burned to regulate grasslands or reduce undergrowth that can lead to uncontrolled forest fires. A completely randomized design (CRD) factorial layout with two treatments (burned and unburned) and two replications was applied. A total of 148 animals comprising six species of rodent and one insectivore were captured over 2,940 trap nights. Among the trapped individuals, 41.9% were adults, 16.1% juveniles and 41.9% sub-adults. Males and females were at parity between treatments. Species abundance was estimated using the minimum number alive (MNA) method for different rodent species and was found to vary with treatment where Mastomys natalensis declined in burned plots whilst Arvicanthis niloticus increased. However, species diversity did not differ across treatments (F1, 10 = 0.15, p = 0.70). Differences in the reproductive condition of female M. natalensis (z = 4.408, df = 15, p < 0.001) and A. niloticus (z = 2.381, df = 15, p = 0.017) were observed between treatments showing that higher numbers of reproductively active females were observed in burned plots in March, whilst in unburned plots more were observed from November to February. Conservation strategies involving periodic habitat burning should, therefore, consider small mammal reproductive periods to ensure that species potentially at risk are not adversely affected and able to rapidly recover from the effects of burning in temporarily lowering food resources and longer term impacts of increased predation caused by reduced cover.

A climatic dipole drives short- and long-term patterns of postfire forest recovery in the western United States

Researchers are increasingly examining patterns and drivers of postfire forest recovery amid growing concern that climate change and intensifying fires will trigger ecosystem transformations. Diminished seed availability and postfire drought have emerged as key constraints on conifer recruitment. However, the spatial and temporal extent to which recurring modes of climatic variability shape patterns of postfire recovery remain largely unexplored. Here, we identify a north-south dipole in annual climatic moisture deficit anomalies across the Interior West of the US and characterize its influence on forest recovery from fire. We use annually resolved establishment models from dendrochronological records to correlate this climatic dipole with short-term postfire juvenile recruitment. We also examine longer-term recovery trajectories using Forest Inventory and Analysis data from 989 burned plots. We show that annual postfire ponderosa pine recruitment probabilities in the northern Rocky Mountains (NR) and the southwestern US (SW) track the strength of the dipole, while declining overall due to increasing aridity. This indicates that divergent recovery trajectories may be triggered concurrently across large spatial scales: favorable conditions in the SW can correspond to drought in the NR that inhibits ponderosa pine establishment, and vice versa. The imprint of this climatic dipole is manifest for years postfire, as evidenced by dampened long-term likelihoods of juvenile ponderosa pine presence in areas that experienced postfire drought. These findings underscore the importance of climatic variability at multiple spatiotemporal scales in driving cross-regional patterns of forest recovery and have implications for understanding ecosystem transformations and species range dynamics under global change.

Differential herbivore occupancy of fire-manipulated savannas in the Satara region of the Kruger National Park, South Africa

The Kruger National Park’s (KNP) long-running experimental burn plots (EBPs) have a history of research projects, which improve the understanding of fire in savanna ecosystems. Using data from KNP’s aerial censuses (2005–2016) and in situ dung count data (2008–2017), this study assessed (1) herbivore densities on the Satara, N’Wanetsi and Marheya EBPs, on annual, triennial and no-burn treatments and across pre-, during and post-drought climate conditions; (2) herbivore densities of these EBPs relative to their non-manipulated surroundings and (3) the extent to which distance to water and rainfall influence ungulate densities. The results revealed that herbivore mean density differed significantly between the three EBPs of Satara and across their fire treatments. N’Wanetsi showed the highest density (0.30 animals/ha), whilst the lowest was found at Marheya (0.12 animals/ha). Overall, pre-drought density was higher on the annual plots (0.56 animals/ha), whilst higher post-drought density was evidenced on the triennial plots (0.80 animals/ha). On average, there were significantly higher herbivore densities on the EBPs (2.54 animals/ha) compared to the surrounding matrix at the larger scales of the Satara management section (0.15 animals/ha) and the central KNP (0.18 animals/ha). A positive correlation between herbivore mean density estimate and distance to water was shown. However, grazer mean density across fire treatments was strongly correlated to rainfall.Conservation implications: Given the variation in fire regimes and their application, and the non-uniform and elevated herbivore densities of the EBPs, inferences from the EBPs cannot be made to the larger KNP. The trials should rather be viewed as an isolated, fire herbivory experiment. It is also recommended to align the experiment with South African National Parks’ mandate by including biodiversity parameters like small mammals and insects in the monitoring of the plots.

Burning season and vegetation coverage influenced the community-level physiological profile of Mediterranean mixed-mesogean pine forest soils

Knowledge of forest soil ecology is necessary to assess vulnerability to disturbances, such as wildfires, and improve its microbial diversity and functional value. Soil microbiota play an important role in forest soil processes and are a key driver of postfire recovery, but they are very vulnerable to heat. According to future scenarios for climate and land-use change, fire regimes will undergo transformations in semiarid terrestrial ecosystems, mainly in the Mediterranean Basin. To develop tools for forest management in fire-prone areas, i.e., fire prevention, we assessed the impact of prescribed burnings on soil microorganisms in Mediterranean mixed pine forests. We hypothesised that low severity fire burns would not influence the functional diversity of soil microorganisms, although the burning season could influence that response due to seasonal variations in its vulnerability. We used the Biolog EcoPlate System to record soil biological indicators and assess the effect of the prescribed burning season (early or late season) on bacterial communities, including the soil–plant interphase. The soil microbiome response differed significantly according to vegetation coverage but prescribed burning season was not directly related. Burning increased the proportions of soil organic matter and soil organic carbon, and also promoted cation-exchange capacity and total phosphorus, which were higher following spring burns. Microbial richness and the Shannon–Weaver diversity index both showed a positive correlation with vegetation cover. However, microbial richness was triggered after burning uncovered patches of vegetation. We also noted differences in the usage pattern for the six substrate groups defined in our study: the use of carboxylic acids, amino acids and carbohydrates was higher in unburned plots and those subject to late burns, whereas amino acids did not predominate in early burn plots.

Litter removal through fire – A key process for wetland vegetation and ecosystem dynamics

Fire is a major driver of global vegetation patterns. It strongly reduces litter and thus alters physical and chemical properties of the environment. Studies investigating the interplay of fire and litter are scarce, and wetland ecosystems are strongly under-represented in research focusing on litter dynamics. We present data on short-term effects of fires in floodplain wetlands along the Amur River in the Russian Far East, an area with a high fire recurrence rate. We analysed vegetation and plant growth patterns as well as soil temperature and nutrient concentrations on recently burnt and unburnt control plots.Directly after fire, litter was reduced by more than 50% on burnt plots. This effect was no longer visible 15 months after fire, probably due to the high productivity of the floodplain ecosystem. Litter was found to act as a key determinant in the net of direct and indirect fire effects, by influencing early plant growth patterns of herbs and grasses. Furthermore, litter removal through fire significantly increased plant species diversity and soil temperature. Contrary, N and P concentrations in living plant biomass of grasses and herbs decreased with decreasing litter cover. Combustion during burning seems to be responsible for the negative direct fire impacts on nutrient concentrations, which were found for N and Mg.Litter removal through fire can strongly affect diversity patterns, dominance structures, and nutrient cycling in wetlands. With increasing fire frequency in the course of global change, significant structural and compositional changes in herbaceous wetland vegetation must be anticipated and the studied ecosystem may shift to reinforced N-limitation.

Litter decomposition and arthropod composition under different ultraviolet levels following prescribed burn in a subtropical pastureland

Reduction in faunal diversity is suggested to reduce litter decomposition, whereas increases in ultraviolet (UV) radiation may directly enhance or indirectly retard litter decomposition. Here we examined the effect of soil arthropods and UV radiation on litter decomposition in burned and unburned plots during a 469-day field experiment in a subtropical pastureland of Puerto Rico. Prescribed burn reduced soil arthropod diversity and increased UV radiation during the initial period of 240 days following the burn, and consequently reduced plant litter decomposition. The density of predators was lower in the burned than in control treatment. UV radiation reduced total arthropod density and diversity by retarding the recolonization of soil arthropods in the burned plots with reduced abundance of predators after 344 days post-burn incubation. Prescribed burn slowed down plant litter decomposition through direct reduction in arthropod diversity immediately after fire and through increase in UV radiation that retards the recolonization of arthropods in later stages after the prescribed burn in the subtropical pastureland.

Changes in Multi-Level Biodiversity and Soil Features in a Burned Beech Forest in the Southern Italian Coastal Mountain

In the context of global warming and increasing wildfire occurrence, this study aims to examine, for the first time, the changes in multi-level biodiversity and key soil features related to soil functioning in a burned Mediterranean beech forest. Two years after the 2017 wildfire, changes between burned and unburned plots of beech forest were analyzed for plant communities (vascular plant and cover, bryophytes diversity, structural, chorological, and ecological variables) and soil features (main chemical properties, microbial biomass and activity, bacterial community composition, and diversity), through a synchronic study. Fire-induced changes in the micro-environmental conditions triggered a secondary succession process with colonization by many native pioneer plant species. Indeed, higher frequency (e.g., Scrophularia vernalis L., Rubus hirtus Waldst. and Kit. group, and Funaria hygrometrica Hedw.) or coverage (e.g., Verbascum thapsus L. subsp. thapsus and Digitalis micrantha Roth ex Schweigg.) of the species was observed in the burned plots, whereas the typical forest species showed a reduction in frequency, but not in cover, except for Fagus sylvatica subsp. sylvatica. Overall, an increase in plant species and family richness was found in the burned plots, mainly in the herbaceous and bryophyte layers, compared to the unburned plots. Burned plots showed an increase in therophytes, chamaephytes, cosmopolites, steno-Mediterranean and Atlantic species, and a decrease in geophytes and Eurasiatic plants. Significant differences were found in burned vs. control soils for 10 phyla, 40 classes, 79 orders, 145 families, 342 genera, and 499 species of bacteria, with about 50% of each taxon over-represented and 50% under-represented in burned than in control. Changes in bacterial richness within several families (reduction in Acidobacteriaceae, Solibacteraceae, Rhodospirillaceae, and Sinobacteraceae; increase in Micrococcaceae, Comamonadaceae, Oxalobacteraceae, Pseudomonadaceae, Hymenobacteraceae, Sphingomonadaceae, Cytophagaceae, Nocardioidaceae, Opitutaceae, Solirubrobacteraceae, and Bacillaceae) in burned soil were related to fire-induced chemical changes of soil (pH, electrical conductivity, and cation exchange capacity). No evident effect of the wildfire was found on organic C content, microbial biomass (total microbial carbon and fungal mycelium) and activity, and microbial indexes (fungal percentage of microbial C, metabolic quotient, and quotient of mineralization), suggesting that soil functions remained unchanged in the burned area. Therefore, we hypothesize that, without an additional disturbance event, a re-establishment of beech forest can be expected but with an unpredictable time of post-fire succession.