Many physical, chemical, mineralogical, and biological soil properties can be affected by forest fires. The effects are chiefly a result of burn severity, which consists of peak temperatures and duration of the fire. Climate, vegetation, and topography of the burnt area control the resilience of the soil system; some fire-induced changes can even be permanent. Low to moderate severity fires, such as most of those prescribed in forest management, promote renovation of the dominant vegetation through elimination of undesired species and transient increase of pH and available nutrients. No irreversible ecosystem change occurs, but the enhancement of hydrophobicity can render the soil less able to soak up water and more prone to erosion. Severe fires, such as wildfires, generally have several negative effects on soil. They cause significant removal of organic matter, deterioration of both structure and porosity, considerable loss of nutrients through volatilisation, ash entrapment in smoke columns, leaching and erosion, and marked alteration of both quantity and specific composition of microbial and soil-dwelling invertebrate communities. However, despite common perceptions, if plants succeed in promptly recolonising the burnt area, the pre-fire level of most properties can be recovered and even enhanced. This work is a review of the up-to-date literature dealing with changes imposed by fires on properties of forest soils. Ecological implications of these changes are described.

/pdf/effects-of-fire-on-properties-of-forest-soils-a-review-1ymllzm5e7.pdf

Effects of fire on properties of forest soils: a review

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 effects on wetland and riparian systems, fire effects models, and watershed rehabilitation.

https://www.fs.fed.us/rm/pubs/rmrs_gtr042_4.pdf

Wildland fire in ecosystems: effects of fire on soils and water

Seed dispersal can be advantageous (1) in escape from density- or distance-dependent seed and seedling mortality, (2) by colonization of suitable sites unpredictable in space and time, and (3) by directed dispersal to particular sites with a relatively high probability of survival. Most previous research on the consequences of seed dispersal has focused on escape and colonization because adaptations ensuring directed dispersal are not expected under the paradigm of diffuse mutualism that characterizes the modern view of seed dispersal evolution. In this paper, I suggest that directed dispersal is more common than previously believed even in the absence of plant adaptations to promote it. Directed dispersal may be seen in particular among animaldispersed plants and in arid ecosystems or successional areas, but has been overlooked due to the lack of detailed data on seed shadows generated by particular species, and the fact that the alternative advantages of dispersal are not mutually exclusive. Although directed dispersal is never thought to be the only advantage of dispersal, it may often be ecologically important if one dispersal vector has a disproportionate effect on plant recruitment. Furthermore, in human-disturbed and managed ecosystems, directed dispersal may be important in restoration. More studies detailing the consequences of different patterns of seed dispersal will be useful for conservation and management strategies.

/pdf/advantages-of-seed-dispersal-a-re-evaluation-of-directed-27o4rzs08s.pdf

Advantages of seed dispersal: A re-evaluation of directed dispersal

This paper was presented at the conference ‘Integrating spatial technologies and ecological principles for a new age in fire management’, Boise, Idaho, USA, June 1999 Maps of fire frequency, severity, size, and pattern are useful for strategically planning fire and natural resource management, assessing risk and ecological conditions, illustrating change in disturbance regimes through time, identifying knowledge gaps, and learning how climate, topography, vegetation, and land use influence fire regimes. We review and compare alternative data sources and approaches for mapping fire regimes at national, regional, and local spatial scales. Fire regimes, defined here as the nature of fires occurring over an extended period of time, are closely related to local site productivity and topography, but climate variability entrains fire regimes at regional to national scales. In response to fire exclusion policies, land use, and invasion of exotic plants over the last century, fire regimes have changed greatly, especially in dry forests, woodlands, and grasslands. Comparing among and within geographic regions, and across time, is a powerful way to understand the factors determining and constraining fire patterns. Assembling spatial databases of fire information using consistent protocols and standards will aid comparison between studies, and speed and strengthen analyses. Combining multiple types of data will increase the power and reliability of interpretations. Testing hypotheses about relationships between fire, climate, vegetation, land use, and topography will help to identify what determines fire regimes at multiple scales.

/pdf/mapping-fire-regimes-across-time-and-space-understanding-3390h6ip5o.pdf

Mapping Fire Regimes Across Time and Space: Understanding Coarse and Fine-scale Fire Patterns

The challenge of quantitative risk analysis for wildland fire

(...) Receiver operating characteristic (ROC) curves show the tradeoffs that are possible by varying the decision criteria, show predictive performance with respect to chance, and show the difference between various models. Two ROC curves were generated to predict ponderosa pine mortality following fall prescribed fires in northern Idaho. One ROC curve was developed from rules of thumb using percent crown scorch. A second ROC curve was developed from a logistic mortality model using diameter at breast height and scorch height. (...)

A Signal Detection Framework to Evaluate Models of Tree Mortality Following Fire Damage

OSWALD, B. P. (Department of Plant and Soil Science, Alabama AM shading, moss, and large vegetation were not significantly effected by treatment. Seven western larch (Larix occidentalis) seeds were distributed after burning treatment on each sample point, and the number of germinations, germinants and seedlings were tracked over two growing seasons. Germinations (741) and germinants (656) from 17,500 seeds occurred on a wide variety of burned and unburned microsite types. Microsite types with successful germination, germinants, and seedling establishment are the "safe sites" (seedbed with proper conditions) for these stages of seedling development. Safe site requirements became more specific as the seedling developed, with only 47 seedlings surviving to the end of the first growing season. Seedlings survived on safe sites which represented 1.5% of the -total area. The eight physical characteristics used to describe microsite types were evaluated with discriminant analysis for significance at each seedling stage. Significant variables and interactions were identified for regression. Analysis produced high (R2 = 0.75) predictability at the end of the first growing season for initial seedling establishment. Safe sites are described for seedling establishment, with site, seedbed treatment, shading and moss as significant variables. The safe site concept appears useful in evaluating germination and initial establishment of western larch.

http://www.jstor.org/stable/pdfplus/2996944.pdf

Microsite variability and safe site description for western larch germination and establishment

A process for modeling short- and long-term risk in the southern Oregon Cascades

To determine the initial effects of slash pile burning on chemical and physical properties in the Vassar soil series, mineral soil samples from two depths (2.5 cm and 12.5 cm) were collected before and after burning slash piles of four fuel loadings (0.5 m, 1 m, 2 m and 3 m) over wet and dry soils, as well as from burned and unburned litter plots. Surface soil CEC decreased with increasing fuel loads, reflecting the increased combustion of fuels, longer residence time of the fires, and increased fire severity with these heavier loads. Available nitrogen increased with increasing fuel loads as a result of the increased total quantity of mineralization of organic N from the heavier fuels. While some cations (magnesium and sodium) increased after burning, others, such as calcium, in general decreased.

Leon F. Neuenschwander

Papers

A Signal Detection Framework to Evaluate Models of Tree Mortality Following Fire Damage

Microsite variability and safe site description for western larch germination and establishment

A process for modeling short- and long-term risk in the southern Oregon Cascades

Effects of slash pile burning on the physical and chemical soil properties of Vassar soils.

Shrub Response to High and Low Severity Burns Following Clearcutting in Northern Idaho