Wildfire effects on water quality in forest catchments: A review with implications for water supply

Synthesis of the literature suggests that physical, chemical, and biological elements of a watershed interact with long-term climate to influence fire regime, and that these factors, in concordance with the postfire vegetation mosaic, combine with local-scale weather to govern the trajectory and magnitude of change following a fire event. Perturbation associated with hydrological processes is probably the primary factor influencing postfire persistence of fishes, benthic macroinvertebrates, and diatoms in fluvial systems. It is apparent that salmonids have evolved strategies to survive perturbations occurring at the frequency of wildland fires (10°–102 years), but local populations of a species may be more ephemeral. Habitat alteration probably has the greatest impact on individual organisms and local populations that are the least mobile, and reinvasion will be most rapid by aquatic organisms with high mobility. It is becoming increasingly apparent that during the past century fire suppression h...

Fire and Aquatic Ecosystems in Forested Biomes of North America

Severe, stand-replacing fires affect large areas of northern temperate and boreal forests, potentially modifying ecosystem function for decades after their occurrence. Because these fires occur over large extents, and in areas where plant production is limited by nitrogen (N) availability, the effect of fire on N cycling may be important for long-term ecosystem productivity. In this article, we review what is known about postfire N cycling in northern temperate and boreal forests experiencing stand-replacing fires. We then build upon existing literature to identify the most important mechanisms that control postfire N availability in systems experiencing severe, stand-replacing fires compared with fires of lower severity. These mechanisms include changes in abiotic conditions caused by the opening of the canopy (for example, decreased LAI, increased solar radiation), changes in ground layer quantity and quality (for example, nutrient release, permafrost levels), and postfire plant and microbial adaptations affecting N fixation and N uptake (for example, serotiny, germination cues). Based on the available literature, these mechanisms appear to affect N inputs, internal N cycling, and N outputs in various ways, indicating that severe fire systems are variable across time and space as a result of complex interactions between postfire abiotic and biotic factors. Future experimental work should be focused on understanding these mechanisms and their variability across the landscape.

Postfire Soil N Cycling in Northern Conifer Forests Affected by Severe, Stand-Replacing Wildfires

SUMMARY

1. We monitored streams within the Gila River drainage in south-western New Mexico, U.S.A., over a 5-year period, to investigate the influence of ash input on water quality and stream biota following forest wildfires.



2. Nutrients [ammonium, nitrate, soluble reactive phosphate (SRP)], potassium and alkalinity were most affected by fires; all were increased in stream water following ash input. Concentrations of each returned to prefire conditions within 4 months. Ammonium and nitrate also increased in stream water as a result of atmospheric fallout (e.g. smoke) from fires outside the catchment.



3. Periphyton biomass was not affected significantly by wildfires, although there was a shift in diatom assemblage to smaller more adnate taxa. Cocconeis placentula was frequently the dominant postfire species.



4. The influence of wildfires on macroinvertebrates ranged from minimal to dramatic reductions in density depending upon the duration of ash flows and the characteristics of the ash material that entered each system. Macroinvertebrate densities returned to prefire conditions within 1 year.



5. An in-situ ashing experiment was conducted on a first-order stream in the Gila River drainage to monitor on-site physiochemical and biotic responses during and after fire ash addition, for comparison with ash delivery from real wildfires on monitored streams. Physical–chemical parameters and algae and macroinvertebrates were monitored in an ashed and upstream reference reach for 13 months. Results generally substantiated findings from monitored streams.



6. Concentrations of major ions and nutrients, as well as turbidity, conductivity and pH, increased immediately in stream water below the point of ashing, while dissolved oxygen decreased. Changes in water chemistry were short-lived (=24 h) except for SRP. The concentration of SRP in stream water was significantly higher in the ashed reach than the control reach for at least 1 month after ash input.



7. Periphyton biomass and diatom assemblages were not significantly altered in the ashing study, whereas macroinvertebrate density was measurably lower in the ashed reach for nearly a year. Macroinvertebrate drift was over 10-fold greater in the ashed reach compared with the reference reach during ashing. Dissimilarity between macroinvertebrate communities in the reference and ashed reaches was significantly greater than variation within reaches for nearly a year.

Effects of wildfire ash on water chemistry and biota in South-Western U.S.A. streams

Stratigraphic charcoal data are used to interpret combustion at a range of spatial and temporal scales. Interpretation is based on assumptions regarding how charred particles are transported to and deposited in sedimentary basins and how the variance structure of stratigraphie profiles is affected by transport. Here we examine evidence for “background” and “local” signals in stratigraphie data based on total abundances of particles and on distributions of particle sizes. Distributions of particle sizes in sediments and in the atmosphere show remarkable consistency, with a ~ 2% decrease in frequency for a 1% increase in particle diameter. Relatively large differences in source distance are required to produce differences in particle size distributions. Thus, stratigraphie samples with disproportionate representation of large particles are likely to represent a nearby source. Simple transport models suggest particles 100 to 101 μm have substantially longer atmospheric residence times than do particles > 102 μm. Several factors can produce a “dichotomy” (background vs local) in total abundances of charred particles. Transport during a single experimental burn shows abrupt decline in accumulation at a burn edge and relatively constant values out to 102 m. Saltation and redistribution of particles in surface runoff following fire are expected to focus accumulation within a catchment (local scale). The amount of transport that occurs by these modes is unstudied. The stratigraphie record appears to support a distinction between local, catchment sources vs. fires burning at greater distance. Charcoal profiles often show distinct peaks when fires burn within a lake catchment but are unaffected by fires that occur at greater distance. Broad subcontinental scale patterns in particle accumulation indicate shifts in regional importance of fire. The low frequency variance can be extracted from charcoal profiles and used to differentiate local from background changes in burning. Although the empirical data are still far too few to permit good characterization of particle transport, the evidence suggests utility in the concepts of background and local signals in profiles.

Background and Local Charcoal in Sediments: Scales of Fire Evidence in the Paleorecord

Neste artigo, analisou-se o Programa Lares – Habitacao Popular (PLHP), programa estadual para reducao do deficit habitacional, o qual contribui para o empoderamento feminino, no caso das mulheres beneficiadas na Zona da Mata mineira. Embora nao seja um programa direcionado para as mulheres, aquelas que sao chefes de familia tem prioridade para o recebimento da casa. Nesta analise foram entrevistadas 236 beneficiarias do PLHP em 17 municipios, utilizando-se a Estatistica Descritiva e o teste de confiabilidade Alfa de Cronbach, para validacao do constructo Empoderamento. Com o intuito de verificar se existe diferenca entre o nivel medio de empoderamento do grupo de mulheres mutuarias e o de beneficiarias, foi realizado o teste nao parametrico U de Mann-Whitney, para amostras independentes. Os resultados indicaram que o empoderamento das mulheres em seu sentido transformador foi expressivo, podendo-se sugerir que o PLHP, ao proporcionar condicao de moradia digna, contribui para o processo de empoderamento feminino.

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Myriam Marta Soares

Papers

Programa lares habitação popular: transformações na vida das mulheres beneficiadas