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Low-intensity burnings could be an effective silvicultural tool to prevent the occurrence and severity of wildfires. Nevertheless, their use as a forest fuel reduction tool may have a negative impact on soil properties. The aim of this investigation was to study the impact of a low-intensity prescribed fire on the main chemical properties of the soil (pH, electrical conductivity, and total organic carbon), and the diversity and composition of the soil bacterial communities in a semi-arid forest in SE Spain. Two similar stands were treated with a low-intensity prescribed burn in spring and autumn 2018 and were compared to an unburned stand. All soil samples were collected at the same time (autumn 2018). The chemical properties of the soil showed no significant differences between the prescribed burns and the control forest. Shannon and Pielou's diversity indices presented values significantly lower in the burned soils compared to the control. Prescribed burning did not modify soil bacterial community structure at the phylum level, but NMDS analysis did reveal a difference between soil bacterial communities at the genus level. Both prescribed burnings favoured some bacterial taxa over others, suggesting different thermal and bacterial resistance. The presence of Massilia, Pseudomonas and Arthrobacter could suggest a short-term ecosystem recovery. Therefore, prescribed burning in semi-arid forests could be suitable as a preventive tool against wildfires. [ABSTRACT FROM AUTHOR]

This study evaluates the effects of prescribed burnings on soil physico‐chemical and biological properties in the short term. This practice is still in the process of evaluation and its effect on Mediterranean pine forests is not understood completely. Prescribed burning was carried out in three plots of mixed Pinus halepensis and Pinus pinaster stands in Castilla‐La Mancha (Spain) while monitoring soil temperature. Vegetation coverage was measured and soil samples were taken before, immediately after and 1 year after burning. Texture, pH, soil electrical conductivity, cation exchange capacity, soil organic carbon, total nitrogen, available phosphorus, magnesium, calcium, potassium, basal soil respiration, microbial biomass carbon content and enzymatic activities of urease, dehydrogenase, phosphatase, and β‐glucosidase were evaluated by generalized linear models, and a principal component analysis was used to reveal the relations between variables. The vegetation cover was reduced by 85% after fire. Soil organic carbon increased immediately after burning to return to the previous values one year later. Phosphorous and cationic exchange capacity increased immediately after burning and remained high one year later, while electrical conductivity and sodium were significantly lower after a year. Basal soil respiration and glucosidase were not affected by prescribed burning. Microbial biomass carbon, urease, phosphatase, and dehydrogenase had significantly lowered one year after burning. Our results show that prescribed burning managed to decrease the vegetation cover of the understory while it also reduced soil biological functions in areas with poorly developed soil and a dry climate, where recovery periods can be longer than expected. [ABSTRACT FROM AUTHOR]

Fire regimes have a major influence on biodiversity in many ecosystems around the globe, yet our understanding of the longer‐term response of fauna is typically poor. We sampled bats with ultrasonic detectors in three different years in dry sclerophyll forests of south‐eastern Australia in a long‐term, management‐scale experiment. Frequent low‐intensity burning (every 2 or 4 years plus unburnt) and logging (with 33% retention of the original unlogged tree basal area) were manipulated to assess their effects on bats. We found that both the fire regime and regrowth after logging influenced the local bat community. The routine burning treatment (burnt every 4 years) in unlogged forest was consistently related to higher total bat activity (2–3 times) and species richness when compared to unburnt controls and logging treatments. Foraging activity was more variable, but it was typically lowest in Unlogged Unburnt Controls. These patterns were evident at both the detector site scale and the block scale and were probably due to a reduction in understorey stem density with burning, especially in unlogged forest. Bat activity was significantly lower across the entire study area (including controls) in 1 year, when sampling occurred within 6 months of burning. When pooled across burning treatments, unlogged forest supported higher bat activity (1.5 times) and species richness than logged forest (12‐ to 17‐year‐old regrowth), again most likely because of a negative association with high stem density in regrowth after logging. We conclude that low‐intensity burning had positive benefits for echolocating bats, most notably in unlogged forest. However, careful planning is required to generate heterogeneous vegetation patterns that are likely to be most suitable for a range of taxa. [ABSTRACT FROM AUTHOR]

Soil respiration is a major carbon pathway sensitive to environmental changes. Using prescribed burnings to reduce fuel accumulation and lower risks of large-scale wildfires has recently become more important. Prescribed burning can significantly alter the soil environment, but its effect in practice on soil respiration is not sufficiently understood. We evaluated the effects of prescribed burning on soil respiration before and after burning (May–July 2016). Prescribed burning was conducted in two natural pine areas by comparing a mixed stand of Pinus nigra Arn. ssp. salzmannii with Pinus pinaster Ait. to a pure stand of Pinus nigra Arn. ssp. salzmannii in the central Iberian Peninsula. Soil respiration was measured by an EGM-4 (Environmental Gas Monitor) infrared gas analyser in both burned and unburned (control) plots. Burnings were low-intensity, and slightly more energetic in the pure stand given its larger litter volume. Post-burning soil respiration followed a similar evolution to that in the control plots, but was greater in the pure stand burned zone and slightly lower in the burned plots in the mixed stand. No significant differences were found in any stand. Soil respiration significantly changed in temporal evolution due to increasing temperatures when summer began. We conclude that prescribed fire induces no changes in SR immediately after fire. This study helps understand how prescribed burnings can affect soil respiration in pure and mixed Spanish black pine forest stands. [ABSTRACT FROM AUTHOR]

This paper presents observational results of wind and plume thermodynamic structures measured during low-intensity subcanopy fires. In-situ meteorological data were collected during the two experiments in the Calloway Forest in North Carolina during the early spring 2010 and winter 2011. Plume updraft velocities between 2 and 4 m s −1 were mostly observed during the subcanopy fires with fire intensity of 1200–2500 kW m −1 . A maximum updraft velocity of 5.8 m s −1 and maximum temperature of 100 °C were recorded at the canopy top due to a head fire. Negative vertical velocities observed within the canopy were associated with cooler air temperatures relative to warm smoke plume temperatures during fire passage at the towers. Increased convection due to the head fire resulted in increased downward transport from above the canopy to the surface. Observed cumulative sensible heat fluxes were 52 kW m −2 and 169 kW m −2 near the surface, and larger values were found at mid canopy heights at both towers. The peak total heat flux of 50 kW m −2 and peak radiative heat flux of 18 kW m −2 observed in 2010 were associated with a head fire moving toward the sensors, whereas lower values of 19 kW m −2 and 9 kW m −2 were measured at the tower in 2011 as a result of a backing fire moving away from the sensors. [ABSTRACT FROM AUTHOR]

Context: After wildfire, surviving trees are of major ecological importance as they can help in the post-fire regeneration process. Although these trees may be damaged, they may also benefit from reduced fuel hazard and competition. However, little is known about the long-term growth response of surviving trees. Aims: This study aims to explain short- to long-term variations in the postfire growth of surviving black pines in an area burnt in 1994, focusing on levels of fire severity and tree sizes. Methods: Relative basal area increments were used to detect time-course variations in postfire radial tree growth depending on fire severity. Linear mixed-effects models were used to describe the factors affecting postfire ring growth. Results: In the short term, fire caused stronger reduction in growth in small trees with increasing bole char height. However, as time since fire increased, a positive effect of fire on growth due to reduced competition counteracted the short-term fire impacts. Indeed, small surviving trees demonstrated a surge in growth 15 years after the fire. Conclusion: It was concluded that reduced competition might offset the short-term negative effects of fire in surviving black pines. [ABSTRACT FROM AUTHOR]

Surface fuels are the critical link between structure and function in frequently burned pine ecosystems, which are found globally (Williamson and Black, 1981; Rebertus et al., 1989; Glitzenstein et al., 1995) [[1], [2], [3]]. We bring fuels to the forefront of fire ecology through the concept of the Ecology of Fuels (Hiers et al. 2009) [4]. This concept describes a cyclic process between fuels, fire behavior, and fire effects, which ultimately affect future fuel distribution (Mitchell et al. 2009) [5]. Low-intensity surface fires are driven by the variability in fine-scale (sub-m level) fuels (Loudermilk et al. 2012) [6]. Traditional fuel measurement approaches do not capture this variability because they are over-generalized, and do not consider the fine-scale architecture of interwoven fuel types. Here, we introduce a new approach, the "3D fuels sampling protocol" that measures fuel biomass at the scale and dimensions useful for characterizing heterogeneous fuels found in low-intensity surface fire regimes. •Traditional fuel measurements are oversimplified, prone to sampling bias, and unrealistic for relating to fire behavior (Van Wagner, 1968; Hardy et al., 2008) [7,8].•We developed a novel field sampling approach to measuring 3D fuels using an adjustable rectangular prism sampling frame. This voxel sampling protocol records fuel biomass, occupied volume, and fuel types at multiple scales.•This method is scalable and versatile across ecosystems, and reduces sampling bias by eliminating the need for ocular estimations.