Natural Wildfires Research Articles

Modeling Cumulative Effects of Wildfire Hazard Policy and Exurban Household Location Choices: An Application of Agent-based Simulations

The flow of amenity-based migrants to fire-prone areas of the US Rocky Mountain West has brought increasing attention to wildfire hazard mitigation management. This paper attempts to build agent-based models which link natural amenity driven exurban growth to wildfire mitigation regimes to provide a framework for assessing cumulative effects of hazard mitigation policy under alternative policy structures. Three simulations were built to demonstrate how agent-based models (ABM) can be used to examine and compare people's choices of residential location in response to natural amenities and wildfire policies. This paper investigates the ways in which policy effects are incorporated dynamically into the land development decision-making process at an individual level in a case study area. Our results show that individual location choices with respect to wildfire risk are sensitive to wildfire mitigation policies.

CHARCOAL RECORDS OF HOLOCENE WILDFIRES AND ENVIRONMENTAL CHANGES IN THE WEIHE RIVER DRAINAGE

The Weihe River drainage is situated in semi-arid and sub-humid monsoon-sensitive areas in the north of China. Charcoal preserved in the loess-soil profile provided records of wildfire history and climatic changes during the late Holocene. Total organic carbon,magnetic susceptibility and charcoal analysis of two Holocene loess profiles in the study area have revealed the relationship between Holocene wildfire activity,human activity and climatic changes. The results show that the climate was arid and local wildfire occurred frequently during the late time of the last glacial period before 11 500 aBP when steppe vegetation expanded from the Inner Mongolian Plateau southerly over the Weihe River drainage. Conversely,wildfires were reduced during the early Holocene. During the Holocene climatic optimum between 8 500 and 3 100 aBP,natural wildfires were largely reduced. Pathogenic alteration to the accumulated dust processes was so active that forest-grassland formed under the humid-warm climate of the Holocene Megathermal. However,localized wildfires in connection with human activities frequently occurred in different patterns at the study sites. With the drier climate and more intensified historical land-use,human-set fires were more common than the natural fires. Very high levels of biomass burning and deteriorated land-use conditions caused a regional desertion by the arable farming communities and the invasion of nomads in the northern part of the Weihe River drainage during the last 3 100 years. After 1 500 aBP,the amount of charcoal sharply decreased and wildfire occurrence slowly disappeared,which may have resulted from totally cultivated land for farming and fully established agricultural landscape in the southern part of Weihe River drainage of the Loess Plateau; meanwhile,mixed agriculture of semi-cultivation and semi-animal husbandry was gradually developed in the northern part of the Weihe River drainage.

Prescribed burning impact on forest soil properties–A Fuzzy Boolean Nets approach

The Portuguese northern forests are often and severely affected by wildfires during the Summer season. These occurrences significantly affect and negatively impact all ecosystems, namely soil, fauna and flora. In order to reduce the occurrences of natural wildfires, some measures to control the availability of fuel mass are regularly implemented. Those preventive actions concern mainly prescribed burnings and vegetation pruning. This work reports on the impact of a prescribed burning on several forest soil properties, namely pH, soil moisture, organic matter content and iron content, by monitoring the soil self-recovery capabilities during a one year span. The experiments were carried out in soil cover over a natural site of Andaluzitic schist, in Gramelas, Caminha, Portugal, which was kept intact from prescribed burnings during a period of four years. Soil samples were collected from five plots at three different layers (0–3, 3–6 and 6–18) 1 day before prescribed fire and at regular intervals after the prescribed fire. This paper presents an approach where Fuzzy Boolean Nets (FBN) and Fuzzy reasoning are used to extract qualitative knowledge regarding the effect of prescribed fire burning on soil properties. FBN were chosen due to the scarcity on available quantitative data. The results showed that soil properties were affected by prescribed burning practice and were unable to recover their initial values after one year.

Holocene wildfires related to climate and land-use change over the Weihe River Basin, China

Charcoal particles preserved in the loess-palaeosol profiles provide records of wildfires during the Holocene. Total organic carbon, magnetic susceptibility and charcoal analysis and OSL dating were carried out in the Holocene loess-palaeosol profiles at two sites in the Weihe River basin. The analytical results show that natural wildfires occurred frequently during the last glaciation when climate was dominated by northwest continental monsoon and steppe vegetation expanded southerly to the Weihe River basin. Wildfire occurrence decreased during climatic amelioration in the early Holocene. During the Holocene Climatic Optimum between 8500 B.P. and 3100 B.P., natural wildfire occurrence was reduced greatly. Pedogenic alteration to the accumulated dust was intensified because of the humid-warm climate brought on by southeast maritime monsoon. Localized fire events in connection with human activities of the Neolithic occurred in several episodes over the region. During the late Holocene when climate become drier, wildfire occurrence over the upland hills shows a pattern different from that in the Guanzhong Basin. Over the upland hills in the north, charcoal concentrations show a decreasing trend in the recent loess and topsoil. It indicates infrequent biomass burning during the last 3100 years. This is attributable to nomadic occupation of the loess hills during the Bronze Age and the development of a land-use pattern of livestock farming in most part of the history. Over the loess tableland in the Guanzhong Basin in the south, abruptly increased charcoal concentrations in the recent loess and topsoil show very high level of biomass burning. This is attributable to the increasingly intensified land reclamation for cereal cultivation from the Bronze Age. This study provides new insights into wildfires over the semi-arid and sub-humid regions in connection with climate and land-use change.

Soil–plant relations in Mediterranean forest environments

During recent decades, Mediterranean forest ecosystems have been subjected to natural wildfires, as well as to important changes in land use. One of the main changes to the landscape has undoubtedly been the reforestation of marginal croplands (Pardos et al. 2007). Soil organic matter has a direct influence on soil conservation, water storage and fertility, and therefore is also an important factor in the perturbations and changes. Many studies in recent years have focussed on soil C dynamics within the context of global change (Bravo et al. 2008). Thus, soil fractionation (e.g. Knicker et al. 2006; Rovira and Vallejo 2007), microbial community (e.g. Zornoza et al. 2009) and biochemical parameters (e.g. Miralles et al. 2009; GonzalezPerez et al. 2008) have been widely studied in different types of forests and under various environmental conditions. The influence of changes in quantity and quality of soil organic matter on water repellency and aggregate stability is also important (e.g. Arcenegui et al. 2008). To predict hydrological functioning under different environmental scenarios, numerous experimental plots have been established in recent years, particularly in Spain, where such plots have been established in contrasting environments ranging from areas with a semi-arid Mediterranean climate to high Pyrenean mountains, mid-altitude mountains and Dehesa environments (i.e. Garcia-Ruiz et al. 2008; Gonzalez-Perez et al. 2008; Hernandez-Santana et al. 2008). Dehesas (with 3–5 million ha, located in dry regions of south-western Europe with poor acidic soils) are the most extended agroforestry system in Europe. They are multipurpose agrosilvopastoral systems with extensive land use, where apart from native grasses, Mediterranean shrubs and periodical crops are combined with widely spaced and scattered oak trees, which forms an open permanent upper storey (tree density from 10 to 80 trees per ha, depending on its main use). Nowadays, Dehesas are considered as habitats to be preserved because of the high biological diversity they include. In Mediterranean countries, the negligible commercial value of forestry products means that aspects such as protection against desertification and conservation of the diversity of flora and fauna assume a relatively more important role. In this context, several species-specific models have been developed for accurate assessment of the suitability of a territory for reforestation (Rubio and Sanchez-Palomares, 2006). However, in some Mediterranean areas where forest growth is high, fast-growing species, such as Eucalypts, pines and other species are now dominant. This implies improvements as regards water regulation and soil protection against erosion. However, the export of large amounts of nutrients as a consequence of forest establishment has also led to the need for studies to assess the sustainability of different models of this type of silviculture (i.e. Merino et al. 2005; Blanco et al. 2005). The Sociedad Espanola de Ciencias Forestales (SECF: Spanish Society for Forestry Sciences) was established in 1991. The Ecology, Ecophysiology and Forest Soil Study Group (one of 19 SECF Study Groups) held its most recent meeting on 22 and 23 October 2007, at the University of Salamanca. The meeting included a large variety of topics: soil chemistry, physics, microbiology, carbon flows, fertility, amendments, biogenic cycles, allelopathy, ecological modelling, silviculture treatments, forest fires, etc. A. Rubio (&) A. Blanco Ecology and Soil Science Unit, ETSI Montes, Polytechnic University of Madrid, 28040 Madrid, Spain e-mail: agustin.rubio@upm.es

The use of reflectance values for the interpretation of natural and anthropogenic charcoal assemblages

Charcoal assemblages occur in both natural and archaeological settings. Cell wall reflectance values of charcoal in polished blocks under oil provide a proxy for temperature of formation. This paper aims to (1) determine whether wildfire charcoals and anthropological charcoals from various pyrotechnical activities can be distinguished using reflectance data and (2) establish if re-charring (i.e. use of charcoal fuel) can be recognised in the archaeological record through analysis of laboratory-produced re-charred charcoals and charcoals from an experimental iron smelt and traditional bronze casting which utilised charcoal fuel. Reflectance frequency data from assemblages representing burning of charcoal, in this case of iron smelting and bronze casting, indicates temperatures from above the mean value of charcoal production (>475°C) up to the maximum temperature reached in the subsequent process (i.e. >475 to >1,100°C). In contrast, wildfire charcoals showed a range of values including material with barely measurable reflectance (minimum values from 0.06% to 0.56%Ro) to maximum reflectance values varying from 1.65%Ro (Tilford) to 3.8%Ro (Zacca). The mean wildfire reflectance indicated temperatures in the range 325–400°C, which can therefore clearly be distinguished from that of the charcoal burning processes. The laboratory-produced re-charred charcoals take on the reflectance value of the highest temperatures experienced; reflectance values were not constrained by the original temperature of formation. High temperatures are most easily achievable by the burning of charcoal fuel, and hence high reflectance charcoals are likely to represent re-charred charcoal. Therefore, this quantitative reflectance method can be used in archaeology to determine the minimum temperature of formation of charcoals in anthropological processes which involve fire, can indicate the likelihood of use of charcoal or wood as fuel and can distinguish between an assemblage of high temperature anthropogenic charcoals and charcoals formed from natural wildfire.

Modelling human impacts on the Tasmanian wedge-tailed eagle ( Aquila audax fleayi)

The wedge-tailed eagle is Australia’s largest bird of prey and one of the largest eagles in the world. Aquila audax fleayi is an endemic Tasmanian subspecies isolated for 10,000 years from the nominate subspecies on the Australian mainland. The Tasmanian wedge-tailed eagle is classified nationally and at a State level as endangered due to its small number of breeding pairs, low breeding success and high rate of mortality from unnatural causes. The subspecies experiences mortality throughout its range from shooting, poisoning, trapping, road accidents, electrocutions and collisions with wind turbines, aircraft, fences and overhead wires, which we term ‘un-natural mortality’. A portion of the subspecies’ range is managed for timber production, which can lead to disturbance of nest sites and the loss of nest trees. We use a model of the eagle population from the Bass District in northeast Tasmania to explore the relative importance of different sources of mortality and nesting habitat loss, and the potential for mitigating impacts associated with unnatural mortality, disturbance, nesting habitat loss and human access to forests. We create a habitat map including suitable nest sites and link it to a dynamic landscape population model based on life history traits and disturbance responses. Using the program RAMAS-Landscape, we model alternative forest management scenarios, ranging from no timber harvesting and a natural wildfire regime, to scenarios prescribing native forest harvesting and regeneration and different levels of conversion of native forest to plantation under the same natural wildfire regime. The results indicate that the Tasmanian wedge-tailed eagle is sensitive to unnatural mortality, plantation establishment and native forest harvesting. The predicted decline over the next 160 years (∼65%) will most likely be driven largely by loss of current and potential future nest sites associated with harvesting activities, exacerbated by unnatural mortality in the wider landscape. Interventions that minimise unnatural mortality, reduce nest disturbance, and retain breeding habitat and nest sites may improve the prospects for the subspecies in the Bass District. If nest disturbance and unnatural mortality continue at the rates modelled here, the species appears to face a high risk of declining substantially in the region.

Litter burning does not equally affect seedling emergence of native and alien species of the Mediterranean-type Chilean matorral

Central Chile differs from other areas with Mediterranean-type climate by the scarcity of natural wildfires. The Chilean matorral is highly invaded by alien plant species from other Mediterranean zones of the world, where natural, recurrent wildfires have been one of their ecological features at least since the Pliocene. This suggests that anthropogenic fires in Chile might favour alien plant recruitment, increasing the invasive process. We assessed the effect of litter burning on the emergence of alien and native species from the soil seedbank of a matorral of central Chile. Soil samples were taken from three types of microhabitats: (i) closed matorral; (ii) beneath the canopy of shrubs and trees from an open matorral; (iii) grassland. Each sample was split in two subsamples. One subsample was exposed to fire by burning the litter taken from its corresponding microhabitat, and the other subsample was left unburned and used as a control. Fire intensity, determined by the fuel type, affected more markedly the native seedbank survival than the alien one. The low-intensity fire produced by grassland litter did not significantly affect the emergence of native herbs but increased alien species richness. The high-intensity and the very high-intensity fires produced by litter burning from beneath the canopy of the closed and the open matorral, respectively, negatively affected the seedling emergence of both native and alien species, but did so in a more pronounced manner to native species. Therefore, anthropogenic fires in central Chile may promote the invasion of alien plants with favourable traits (i.e. heat-shock resistance of seeds) that are not present in the native flora.

Diversity of vascular plant species in the montane boreal forest of western Canada in response to climatic changes during the last 25 ka, fire, and land use

Summary: This paper examines the biodiversity of vascular plants in the vast boreal forest area of the southern Cordillera of western Canada. It was glaciated until 11 ka, and since then, vascular plants have had difficulties colonizing the de glaciated areas from the surrounding refugia. Problems include the topography, the comparatively inhospitable climate, limited source areas, natural wildfires, and fluctuations in climate. As a result, the forest consists of up to 494 species of vascular plants at any one site compared to 871 species at Mount Rainier, Washington State. For comparison, 2,993 taxa have been reported from British Columbia indicating the limited colonization that has occurred. European Man has added to these problems by increasing fire frequency and by extensive, repeated logging of large areas. A limited amount of intensive irrigated agriculture also occurs near southern rivers and lakes. The end result is a limited range of species, of which 30% are regarded as rare or endangered. The consumers of the resulting biomass are therefore also limited in their food supply.

Managing natural wildfires in Sierra Nevada wilderness areas

Past policies of excluding all wildfires from forests throughout the US are giving way to new strategies that incorporate naturally ignited fires into forest and fire management. In this paper, we evaluate the effects of long-standing natural fire programs (now referred to as wildland fire use or WFU) in two Sierra Nevada wilderness areas. We present reconstructions of historical fire occurrence using tree ring proxies, along with chronologies of tree recruitment, to infer the effects of WFU programs on forest structure. Historically, fires burned every 6 to 9 years, which moderated tree recruitment. Fire suppression policies established in the early 1900s successfully excluded fire and allowed for unprecedented tree recruitment. Despite the substantial changes in forest structure and composition, the frequency and extent of fires during the current WFU period (1972–present) approach historical levels. This information can provide some necessary insight in implementing WFU policy and developing management plans for similar forest types throughout the western US.

Managing natural wildfires in Sierra Nevada wilderness areas

Managing natural wildfires in Sierra Nevada wilderness areas

Precipitation associated with lightning-ignited wildfires in Arizona and New Mexico

From 1990 to 1998, over 17000 naturally ignited wildfires were observed in Arizona and New Mexico on US federal land during the fire season of April through October. Lightning strikes associated with these fires accounted for less than 0.35% of all recorded cloud-to-ground lightning strikes that occurred during the fire season during that time. Given the high aridity of this region, why do some lightning strikes ignite fires and others not? Natural wildfire ignitions in this region are often attributed to what is referred to as ‘dry’ lightning, or lightning with little or no precipitation. This study used daily and hourly gridded precipitation derived from historical gauge data to compare the amount of precipitation associated with natural wildfires and the amount of precipitation associated with lightning strikes that were not associated with natural wildfire events. Climatology of natural ignitions tend to peak before the time of the seasonal maximum lightning flashes and precipitation, suggesting ‘dry’ ignitions in the early part (e.g. late June, early July) of the wildfire season. Observed natural wildfires were more often associated with conditions of <2 mm of precipitation on the day of the event than were cases without an associated ignition. The majority of lightning flashes that did not cause a discovered wildfire were associated with a higher precipitation rate after the timing of the event, which suggests the possibility of the precipitation extinguishing the wildfires before discovery. Most lightning flashes that were not associated with a discovered ignition had twice as many hours with some measurable precipitation than where there were discovered ignitions, which eludes to the longer-term impact of preceding precipitation on the fuels than the lightning storm-associated precipitation. These results can be applied to gridded forecasts of amount of precipitation to indicate areas where there is an increased probability of natural wildfire ignition, assuming the other factors of ignition source and fuel availability are present.

Wildfire history and fire ecology of the Swiss National Park (Central Alps): new evidence from charcoal, pollen and plant macrofossils

Microscopic (> 10 mm) and macroscopic (> 200 mm) charcoal particles were analysed in sediments from two mires in subalpine coniferous forests at c. 1800 m a.s.l. in southeastern Switzerland. Pollen and plant macrofossils suggest that since 6000 BC, Pinus mugo ssp. uncinata (DC) Domin (‘upright mountain pine’) has mostly been the dominant tree species at one of the study sites (Il Fuorn). In contrast, forests dominated by Picea abies (Norway spruce) have formed the vegetation since c. 4000 BC around the mire ‘Fuldera-Palü Lunga’. Mean fire-return intervals (MFI) varied from 250 to > 600 years, depending on forest type, climate and land use. In mountain-pine forests (Il Fuorn), local fires occurred approximately every 250 years, even before the region was agriculturally used (ie, before 3600 BC). About 2000 years ago, intensified human impact as documented by the pollen record resulted in increased fire activity at Fuldera. Post-fire vegetation dynamics suggest that the mountain-pine stands at Il Fuorn had a moderate fire regime with a mix of surface and crown fires. In alpine ecosystems, the impact of fire is generally overshadowed by other disturbance factors such as windthrow, landslides, fungal decay and by climate changes or human land use. Nevertheless, our results show for the first time that natural wildfires exerted a major control on the subalpine coniferous forest ecosystems of the Swiss National Park and its neighbouring areas, eg, by contributing to maintain Pinus mugo ssp. uncinata forests throughout the mid and late Holocene.

Charcoal records of fire history in the Holocene loess–soil sequences over the southern Loess Plateau of China

Charcoal preserved in accretionary loess–soil profiles within the southern part of the Loess Plateau has recorded fire history and landscape evolution connected with climatic variations and human activities. Local wildfires occurred frequently during the late last glacial period and the early Holocene before 8500 years BP when steppe vegetation expanded from the Inner Mongolian Plateau southerly over the Loess Plateau. During the Holocene climatic optimum between 8500 years BP and 3100 years BP, natural wildfires were largely reduced. Pedogenesis of the Luvisols and Isohumisols was intensified because of the increased monsoonal precipitation and soil moisture. Localized fires in connection with human activities occurred in different patterns at the study sites. Fire seems to have been applied to vegetation clearance for land reclamation for millet cultivation at many places during the Neolithic and early Bronze Age. Levels of biomass burning were very high during the late Holocene, when the climate became drier and historical land-use became more intensive. At some sites, the intensity of human disturbance by fire and cultivation increased continuously during the last 3100 years. At the other sites, local fires occurred most frequently between 3100 years BP and 1500 years BP during the major period of land reclamation for cereal cultivation. Human burning of the landscape has been reduced since then.

Response of boreal plant communities to variations in previous fire-free interval

The present study used overlapping burn scars from natural wildfires to examine the effects of changes in the fire-free interval on early successional plant communities in boreal forests of central Yukon Territory, Canada. Data on plant community composition and residual organic material were collected in the first decade of post-fire regeneration in two study areas with recent fire overlap. Sites with a shorter fire-free interval had reduced loads of deadwood and shallower organic layers after the most recent fire. Multivariate analysis of species cover indicated that sites in and out of the burn overlap zones also supported distinct plant communities. Differences in the plant communities were associated with a greater abundance of woody deciduous species, such as Populus tremuloides, Salix spp., and Shepherdia canadensis, at sites that had recently re-burned. Sites that burned after a longer interval had higher moss cover and greater abundance of Picea mariana, Calamagrostis canadensis, and Ribes glandulosum in one study area, and Epilobium angustifolium in the second area. Ordinations of species cover indicated that plant community patterns were most strongly associated with gradients related to fire history and topography. In general, shorter fire-free intervals reduced pools of residual plant material and favored dominance of resprouting, woody deciduous species.

Does clearfell, burn and sow silviculture mimic the effect of wildfire? A field study and review using litter beetles

The ecological effects of clearfell harvesting followed by high intensity burning are sometimes thought to mimic wildfire, the major natural disturbance regime in Tasmanian wet forests. We investigated whether the litter-inhabiting beetle populations in logged and burnt regeneration forest resembled those in forest regenerating following natural wildfire. Pitfall trapping and habitat assessment were conducted at three pairs of adjacent 33-year-old logging and wildfire regeneration sites. In total, 6128 beetles were collected, representing 179 morphospecies in 30 families. The beetle assemblages in logging and wildfire treatments could not be distinguished. However, beetle populations did differ subtly between sites. One Aleocharinae (Staphylinidae) morphospecies and one Carabidae species were more abundant at one of the three site pairs. Multivariate analyses of common species indicated that the litter beetle assemblages differed significantly between sites, and this was partially related to their degree of geographical separation. Environmental factors considered indicative of logging impacts did not differ between wildfire and logging regeneration treatments. Temporal and landscape scale differences between logging and the natural disturbance regime and changes to logging practices since these study sites were harvested may have negative impacts on litter beetles in the future. Changes to current harvesting practices are recommended to better mimic the natural disturbance regime and thus improve conservation of forest biodiversity.

Population increase in Kirtland's warbler and summer range expansion to Wisconsin and Michigan's Upper Peninsula, USA

The threatened Kirtland's warbler Dendroica kirtlandii breeds in stands of young jack pine Pinus banksiana growing on well-drained soils in Michigan, USA. We summarize information documenting the range expansion of Kirtland's warbler due to increased habitat management in the core breeding range in the Lower Peninsula of Michigan during 1990-2000. We collected records and conducted searches for the species in Michigan's Upper Peninsula and Wisconsin over 1978-2000. During that time 25 males were found in Wisconsin and 90 males in the Upper Peninsula. We documented colonization of Michigan's Upper Peninsula by six ringed males from the Lower Peninsula of Michigan. Four ringed birds also moved back to the core breeding range, including two males that made two-way movements between the core breeding range and the Upper Peninsula. Thirty-seven females were observed with males from 1995 to 2000, all in Michigan. Nesting activities were noted for 25 pairs and at least nine nests fledged young. One male ringed as a fledgling returned to breed in two subsequent years. After a 19-year period of population stability, the Kirtland's warbler population increased four-fold during 1990-2000, most likely in response to a tripling in habitat area. This increase in sightings and documented breeding may be related to habitat availability in Michigan's Upper Peninsula and to saturation of habitat in the main breeding range. The increase in extra-limital records during 1995-1999 corresponds to the time when the population went frorn the minimum to the maximum projected population densities, and a decline in natural wildfire habitat was just offset by new managed habitat for the Kirtland's warbler.

Comparison of the radiological dose from the Cerro Grande fire to a natural wildfire

Since the Cerro Grande fire burned portions of a Department of Energy facility where nuclear weapons research occurs, it is important to determine if the fire posed greater risk to the public than a natural fire. All wildfires release radioactive as well as other toxic pollutants into the atmosphere. Thus, it is important to determine if the radioactive air emissions from the Cerro Grande fire were statistically different than those from a natural wildfire, specifically the Viveash fire.

Short-term effects of aerially-applied fire-suppressant foams on water chemistry and macroinvertebrates in streams after natural wild-fire on Kangaroo Island, South Australia

In remote areas, wild-fires often must be controlled by applying fire-retardants and suppressants dropped from small aircraft. However, impacts of these chemicals on natural stream ecosystems are poorly known. Unintentional aerial application of fire-fighting chemicals (Phos-Chek WD-881 and ForExspan S) onto two small streams during a natural wildfire on Kangaroo Island, South Australia, provided an opportunity to study the short-term effects on water chemistry and aquatic invertebrates. Within 2 weeks of application, samples of water and macroinvertebrates were collected from sites upstream of the application point, within the zone of application, and downstream where burning had been controlled on two streams. Three sites on a reference stream in the same sub-catchment that had been burned by the same fire but without application of fire-suppressants were also sampled. All sites were resampled three months later (within two weeks of the first flushing rains). There were no marked differences in water quality among the sites on the reference stream but in one of the impacted streams where flow had ceased before the fire, dissolved and total phosphorus concentrations were elevated at the site where the fire-suppressants were applied. Phosphorus concentrations were reduced 2–3-fold at this site after brief flushing by rain. Conversely, dissolved and total N and P concentrations at the other impacted stream that flowed permanently did not differ among the sites and there was no evidence for persistent changes to water quality from the applied fire-suppressant foams. Taxon richness was higher at the application and downstream sites than at upstream sites in the two impacted streams. There were also no discernible effects of the fire-suppressants on macroinvertebrate assemblage composition or taxon richness within the two streams two weeks after the chemical application or soon after flushing rains. Assemblage composition in the temporary stream was significantly different from that in the reference and the other impacted stream but also appeared unaffected by the fire-suppressants. The lack of impact on resident stream macroinvertebrates may result partly from their inherent high tolerance to the harsh physical and chemical conditions of these streams, many of which typically cease flow in summer.

Late Triassic charcoal from Petrified Forest National Park, Arizona, USA

Fossil charcoal has been found in the Late Triassic Chinle Formation in Petrified Forest National Park, a location that is world famous for its silicified tree trunks. The material consists of charcoalified secondary wood, and has sufficiently well preserved plant anatomy to show it may be described as ‘araucarian type’, although it does display some minor differences from the anatomies described for the silicified gymnosperm trunks in the park. The presence of the charcoal proves that on occasion natural wildfires, most probably ignited by lightning, must have occurred in the Chinle Triassic palaeoenvironments, with resulting impacts on the biota of those times. It is currently impossible to estimate how often these fires occurred, as the incidence of charcoal here and in the whole fossil record apart from the frequency of ancient fires also reflects the preservation and burial conditions of the material. There is scant mention of Triassic charcoal in the literature, a notable absence given the abundance of charcoal that has been recorded in the Carboniferous, Jurassic, and Cretaceous periods. This lack of charcoal may support the theory that atmospheric oxygen levels were lower during the Triassic than in the Carboniferous.