Wildland fire in ecosystems: Effects of fire on soil and water

This state-of-knowledge review about the effects of fire on soils and water can assist land and fire managers with information on the physical, chemical, and biological effects of fire needed to successfully conduct ecosystem management, and effectively inform others about the role and impacts of wildland fire. Chapter topics include the soil resource, soil physical properties and fire, soil chemistry effects, soil biology responses, the hydrologic cycle and water resources, water quality, aquatic biology, fire effectson wetland and riparian systems, fire effects models, and watershed rehabilitation

Riparian Fuel Treatments in the Western USA: Challenges and Considerations

Fuel reduction treatments are being conducted throughout watersheds of the western United States to reduce hazardous fuels in efforts to decrease the risk of high-severity fire. The number of fuel reduction projects that include near-stream environments is increasing, bringing new challenges to riparian management. Riparian areas are protected by administrative regulations, some of which are largely custodial and restrict active management. However, riparian areas have also been affected by fire suppression, land use, and human disturbance, so manipulative treatments of vegetation and other fuels may be needed in some locations to maintain riparian biodiversity and restore valued functions. This report is a synthesis of current knowledge on the effects of wildfire and fuels treatments in riparian areas of the interior western United States, and includes the following: (1) a literature review of fire effects on riparian and aquatic characteristics and functions, provided as background for considering the need and potential impacts of fuel treatments; (2) a review of the potential effects of prescribed fire and mechanical treatments on riparian and aquatic resources and biota; (3) results of an online survey of resource managers, summarizing information about proposed and completed fuel reduction projects in riparian areas and wetlands in the interior west; (4) suggestions for pre- and post project-level monitoring for riparian fuels projects; and (5) a presentation of case studies, describing riparian fuel treatments with different objectives and methods. Research on the effects of fuel treatments on riparian and aquatic resources is limited, and monitoring of projects is highly encouraged, especially in watersheds supporting species of concern. Results of the online survey showed that habitat restoration is a common objective for many fuel treatments that include riparian areas; for each of the case studies, restoration of near-stream habitat for wildlife was a major goal. The integration of riparian fuel treatments with other aspects of fire and watershed management could potentially improve riparian condition in multiple stream and vegetation types

Physical Vulnerabilities from Wildfires: Flames, Floods, and Debris Flows

Humans live in or adjacent to wildland ecosystems that burn periodically and are part of nearly all ecosystems that are in the pyrosphere. There are many hazards posed by wildfire and certain consequences of living in these ecosystems. Most are associated with wildfire, but the increased use of prescribed fire is an issue because of associated risks with human attempts to manage ecological goals. The hazards posed by wildfire involve cultural and economic loss, social disruption, infrastructure damage, human injury and mortality, damage to natural resources, and deterioration in air quality. The economic and human health and safety costs are on the rise due to increasing wildland-urban interface problems and extreme wildfire behavior brought on by climate change. In the past, urban fires have been the greatest threat to human health and safety killing over 100,000 people. World ecosystems have been modified extensively by fire. We live on a “fire planet.” With larger human populations and a changing, drying climate, the impact of fire on humans and the hazards faced by our natural and developed world will continue to increase. The increase in wildfire hazards in the twenty-first century will require higher levels of training, increased investments in wildfire personnel and infrastructure, greater wildfire awareness, and improved planning to reduce fire impacts

Os efeitos dos fogos florestais nas comunidades de macroinvertebrados lóticos em Portugal

Doutoramento em BiologiaThe effects of wildfires in Mediterranean lotic communities are still poorly documented. Despite some progress in recent years, the published data refer mainly to studies conducted in North America, with little information on European rivers. Given the importance of regional geographic context, both on the effects of fire and on the resilience of the communities, the gap in the biogeographical knowledge represent a limitation to the implementation of appropriate management measures. This thesis consists in a systematic study of the effects of fire on the macroinvertebrate communities of streams of North and Central Portugal. A chronosequence survey was conducted in order to analyze long-term effects of wildfires (1-18 years) and provide chronological information on the ecological recovery of macroinvertebrate communities. The results indicated that the macroinvertebrate communities recover in abundance and taxa richness and in terms of community structure about two years after the fire impact. A short-term survey was also carried out, where the initial response of macroinvertebrates to fire disturbance was documented, in streams recently affected by wildfires. The parameters analyzed were compared with reference sites without fire impact for the last 20 years. In all sampling periods, lower abundance and lower species richness were recorded in impacted streams, and differences in community structure were found between burnt sites and reference sites. In our study, both on long -term and short-term surveys, the environmental features that conditioned the response of biological communities were evaluated. River size, the extent of the burnt area, conductivity, along with channel characteristics and riparian vegetation, were considered determinant in the response of macroinvertebrates communities to fire impact, and can influence the susceptibility of stream ecosystems. We also analyzed the data of the short-term survey on a trait approach. Differences on functional diversity and on frequency of several trait modalities were analyzed. Specific differences in the food group and reproductive strategies between burned and not burned sites were recorded. Despite the unequivocal negative impact of wildfire on macroinvertebrate communities of Portuguese streams, the recovery seems to be rapid, demonstrating their resilience to this type of disturbance.Os efeitos dos fogos nas comunidades lóticas mediterrânicas estão ainda mal documentados. Apesar do progresso verificado nos últimos anos, os dados publicados referem-se principalmente a estudos efetuados na América do Norte, sendo escassa a informação relativa aos rios Europeus. Dada a importância do contexto geográfico regional, quer nos efeitos do fogo no meio ambiente quer na resiliência das comunidades, a lacuna no conhecimento biogeográfico representa uma limitação à implementação de medidas de gestão adequadas. A presente tese consiste um estudo sistemático dos efeitos do fogo nas comunidades de macroinvertebrados dos ribeiros do Norte e Centro de Portugal. Foi analisada uma cronosequência para averiguar o efeito do fogo numa escala temporal mais alargada (1 a 18 anos) providenciando informação cronológica sobre a recuperação ecológica das comunidades de macroinvertebrados a longo prazo. Os resultados indicaram que as comunidades de macroinvertebrados recuperam em abundância, riqueza taxonómica e em termos de estrutura das comunidades cerca de dois anos após o impacto Num estudo a curto prazo, em ribeiros recentemente afetados por fogos florestais, foi documentada a resposta inicial dos macroinvertebrados à perturbação pelo fogo e os parâmetros analisados foram comparados com locais de referência onde não ocorreram fogos nos últimos 20 anos. Em todos os períodos amostrados registou-se menor abundância e menor riqueza específica nos ribeiros impactados, bem como diferenças ao nível da estrutura das comunidades entre locais ardidos e os locais de referência. Tanto no estudo a longo prazo como no estudo a curto prazo, foram avaliados os fatores ambientais que condicionaram a resposta das comunidades biológicas. O tamanho do rio, a extensão da área ardida, condutividade, bem como as características do canal e da vegetação ripária, são determinantes na resposta dos macroinvertebrados ao impacto do fogo, e podem influenciar o grau de susceptibilidade dos ecossistemas lóticos. Foram ainda analisados os resultados dos levantamentos a curto prazo numa abordagem do ponto de vista funcional. Foram analisadas as diferenças ao nível da diversidade funcional e ao nível da frequência das várias características funcionais dos organismos. Foram registadas diferenças pontuais em termos do grupo alimentar e estratégias de reprodução, entre locais ardidos e não ardidos. Apesar do inequívoco impacto negativo do fogo nas comunidades de macroinvertebrados aquáticos, a recuperação parece ser rápida, demonstrando a sua resiliência perante este tipo de perturbação

Effects of fire on the hydrology, biogeochemistry, and ecology of peatland river systems

Peatlands are found around the world and cover ~3.4% of the Earth’s surface. In the UK, peatlands cover 17.2% or ~1.58 Mha of the land surface and occur mainly in upland areas covering the headwaters of most major British rivers. However, large areas are now subject to prescribed vegetation burning despite policy guidance that recommends a strong presumption against burning deep blanket peat. Wildfires occur sporadically but are forecast to increase in frequency in the future. This paper provides a synthesis of current knowledge about how UK peatland-dominated river catchments respond to fires caused by prescribed vegetation burning and uncontrolled wildfire. We provide insight into the effects of fire on the hydrology, biogeochemistry, and biota of peatland river ecosystems, and the peatland-soil-driven controls on these effects at the catchment-scale. Burning increases the depth to water table and water-table variability, although some small-scale studies indicate shallower water table in some places. More work is needed on fire effects on peatland river flow, but recent results suggest a complex response with smaller flow peaks for burned systems associated with most rainfall events, but enhanced peaks compared to unburned systems for the top quintile of rainfall events with the largest total rain. Evidence from biogeochemical studies suggests that fire leads to increased dissolved organic C concentrations in rivers. River biota responses primarily include significant reductions in the density of grazing mayflies but increases among detritivores including Chironomidae and Baetis mayflies. We provide a conceptual synthesis that links the main responses of terrestrial and aquatic systems to fire, and we summarize some major research gaps that should be prioritized to inform future policy around peatland management

Long-term effects of portuguese forest fires on morphology and aquatic habitat structure of lotic ecosystems

This thesis investigates long-term effects of forest fires on morphology and functioning of Portuguese streams via burned wood. Wildfires influenced the landscape dynamics across three regions examined, towards increases in shrublands encroaching into previously forested areas. Large wood amounts within 27 streams were low and are expected to decline in the future owing to wildfire. Likewise, wildfire was promoting wood lacking structural complexity, thus likely reducing habitat heterogeneity that improves conditions for aquatic organisms. The effect of fire providing wood with greater diameter will increase its probability for stream functions such as pool formation. However, this functionality may not persist because most of this wood was decayed and less stable in the channel. It is critical for aquatic communities if fire-derived wood falls directly into the river or if it is previously conditioned for some time on the forest floor; Efeitos a longo prazo dos fogos florestais na morfologia e estrutura do habitat em ecossistemas lóticos de Portugal ### Esta tese avalia os efeitos a longo prazo dos fogos florestais na morfologia e funcionamento de rios portugueses através da madeira ardida. O fogo influenciou a dinâmica da paisagem em três regiões estudadas, favorecendo a invasão por matos de áreas previamente florestadas. A quantidade de pedaços de madeira em 27 rios foi baixa e prevê-se a sua diminuição futura por influência do fogo. O fogo promoveu também a presença de madeira com menor complexidade estrutural, reduzindo provavelmente a heterogeneidade de habitat que melhora as condições para os organismos aquáticos. A madeira queimada tinha maior diâmetro, aumentando a probabilidade de função no rio, como a criação de fundões. Esta funcionalidade pode não persistir porque esta madeira estava degradada e menos estável no canal. É determinante para as comunidades aquáticas se a madeira dos fogos cai directamente no rio ou se é previamente condicionada durante algum tempo no solo da floresta

Fire as a disturbance in mediterranean climate streams

Mediterranean climate ecosystems are among the most fire-prone in the world; however, little is known about the effects of fire on mediterranean streams (med-streams). Fire impacts on med-streams are associated with increased runoff and erosion from severely burned landscapes during storms, particularly the first intense rains. Increased inputs of water, solutes, nutrients, sediment, organic matter, and ash to streams after fires are usually observed for months to up to 4 years. Return to pre-fire conditions is associated with vegetation recovery. Benthic algae, invertebrates, and fish are reduced to low levels by scouring floods after wildfire. If riparian zones are burned, benthic algae increase, and invertebrate communities become dominated by r-strategist species. Fishes are eradicated from reaches affected by intense wildfire and often do not re-colonize quickly because of downstream barriers. In general, med-stream communities appear to be more resilient to fire compared to streams in other ecosystems because of the rapid recovery of mediterranean upland and riparian vegetation and geomorphological conditions (1-4 years in med-streams vs 5-10 years in non-med streams). However, drought or mass sediment movements after fire can prolong fire effects. Studies of the long-term effects of fire and the consequences of fire management practices are still needed. © 2013 Springer Science+Business Media Dordrecht

Physicochemical and biological responses of streams to wildfire severity in riparian zones

We investigated the effects of a wildfire on stream physical, chemical and biological characteristics in a Mediterranean climate, comparing stream community structure and consumer resource use in burned versus unburned catchments in Santa Barbara County, CA, U.S.A. Canopy cover was lower and water temperature was higher in streams draining basins where the riparian vegetation burned than in streams in unburned basins or burned basins where riparian vegetation remained intact. Stream flow and suspended sediment concentrations during large post-fire storms and wet season nutrient levels were higher in burned than unburned catchments, with increased sedimentation after flood peaks. A year after fires, algal levels were highest in streams where riparian vegetation burned and lowest in streams in burned basins where the riparian canopy remained intact. In contrast, streams in burned basins had lower particulate organic matter, detritivore and predator levels than unburned basins, regardless of whether riparian vegetation burned. Where present, southern California steelhead trout (Oncorhynchus mykiss) were extirpated from burned basins. Algivore densities were high in streams with burned riparian vegetation for two post-fire years before declining to unburned stream levels. Shredder densities rebounded in streams in burned basins with intact riparian vegetation, but remained low for 4 years where riparian vegetation burned. Predatory invertebrate densities increased at sites where trout were eliminated by wildfire. Hydrogen stable isotope analysis indicated that the diets of most invertebrate taxa in streams with burned riparian vegetation a year after fires were comprised of a higher proportion of algal material than riparian detritus relative to invertebrates in streams with intact riparian vegetation. Wildfire impacts on stream food webs are determined, in part, by fire severity in the riparian zone. Streams with burned riparian canopies supported algal-based food webs and streams with intact riparian canopies sustained detrital-based food webs. Fire affected basal resources (nutrients, light, allochthonous inputs) with bottom-up effects on primary producers and consumers, but top-down effects were decoupled at the trophic link between invertebrate predators and primary consumers. © 2015 John Wile