How geomorphic context governs the influence of wildfire on floodplain organic carbon in fire-prone environments of the western United States

We draw on published studies of floodplain organic carbon storage, wildfire-related effects on floodplains in temperate and high latitudes, and case studies to propose a conceptual model of the effects of wildfire on floodplain organic carbon storage in relation to climate and valley geometry. Soil organic carbon typically constitutes the largest carbon stock in floodplains in fire-prone regions, although downed wood can contain significant organic carbon. We focus on the influence of wildfire on soil organic carbon and downed wood as opposed to standing vegetation to emphasize the geomorphic influences resulting from wildfire on floodplain organic carbon stocks. The net effect of wildfire varies depending on site-specific characteristics including climate and valley geometry. Wildfire is likely to reduce carbon stock in steep, confined valley segments because increased water and sediment yields following fire create net floodplain erosion. The net effect of fire in partly confined valleys depends on site-specific interactions among floodplain aggradation and erosion, and, in high-latitude regions, permafrost degradation. In unconfined valleys in temperate latitudes, wildfire is likely to slightly increase floodplain organic carbon stock as a result of floodplain aggradation and wood deposition. In unconfined valleys in high latitudes underlain by permafrost, wildfire is likely in the short-term to significantly decrease floodplain organic carbon via permafrost degradation and reduce organic-layer thickness. Permafrost degradation reduces floodplain erosional resistance, leading to enhanced stream bank erosion and greater carbon fluxes into channels. The implications of warming climate and increased wildfires for floodplain organic carbon stock thus vary. Increasing wildfire extent, frequency, and severity may result in significant redistribution of organic carbon from floodplains to the atmosphere via combustion in all environments examined here, as well as redistribution from upper to lower portions of watersheds in the temperate zone and from floodplains to the oceans via riverine transport in the high-latitudes. © 2019 John Wiley & Sons, Ltd.     

Sources of inherent infiltration variability in postwildfire soils

An automated disc infiltrometer was developed to improve the measurements of soil hydraulic properties (saturated hydraulic conductivity and sorptivity) of soils affected by wildfire. Guidelines are given for interpreting curves showing cumulative infiltration as a function of time measured by the autodisc. The autodisc was used to measure the variability of these soil hydraulic properties in three different sample sets: (a) a reference soil consisting of a nonrepellent, uniform, fine sand; (b) soils with the same soil textural classification derived from the same bedrock geology but having different initial burn severities; and (c) soils from different bedrock geology but having the same burn severity. The autodisc infiltrometer had greater sampling rates and volume resolution when compared with the visual minidisc infiltrometer from previous studies. There was no statistical difference in the mean values measured using the autodisc and visual minidisc, but the variability of the autodisc measurements was significantly less than the visual minidisc for a given set of samples. The greatest variability of soil hydraulic properties in reference samples with uniform particle size was attributed to different pore geometries (coefficient of variation [COV] = 0.28–0.34). Unburned field samples (same soil type) with heterogeneous particle sizes had greater variability (COV = 0.57–0.78) than the reference samples. However, this basic variability decreased or remained constant in these field samples as burn severity increased. Additional sources of variability (COV = 0.53–1.99) were attributed to multiple layers resulting from ash or sediment deposition. Results indicate that resolving differences in soil hydraulic properties from different sites requires more than the common 10 random samples because of the multiple sources of variability.     

Regional patterns of postwildfire streamflow response in the Western United States: The importance of scale‐specific connectivity

Wildfires can impact streamflow by modifying net precipitation, infiltration, evapotranspiration, snowmelt, and hillslope run‐off pathways. Regional differences in fire trends and postwildfire streamflow responses across the conterminous United States have spurred concerns about the impact on streamflow in forests that serve as water resource areas. This is notably the case for the Western United States, where fire activity and burn severity have increased in conjunction with climate change and increased forest density due to human fire suppression. In this review, we discuss the effects of wildfire on hydrological processes with a special focus on regional differences in postwildfire streamflow responses in forests. Postwildfire peak flows and annual water yields are generally higher in regions with a Mediterranean or semi‐arid climate (Southern California and the Southwest) compared to the highlands (Rocky Mountains and the Pacific Northwest), where fire‐induced changes in hydraulic connectivity along the hillslope results in the delivery of more water, more rapidly to streams. No clear streamflow response patterns have been identified in the humid subtropical Southeastern United States, where most fires are prescribed fires with a low burn severity, and more research is needed in that region. Improved assessment of postwildfire streamflow relies on quantitative spatial knowledge of landscape variables such as prestorm soil moisture, burn severity and correlations with soil surface sealing, water repellency, and ash deposition. The latest studies furthermore emphasize that understanding the effects of hydrological processes on postwildfire dynamic hydraulic connectivity, notably at the hillslope and watershed scales, and the relationship between overlapping disturbances including those other than wildfire is necessary for the development of risk assessment tools.     

Factors affecting connectivity and sediment yields following wildfire and post-fire salvage logging in California's Sierra Nevada

Sediment delivery following post-fire logging is a concern relative to water quality. While studies have assessed the effect of post-fire logging on sediment yields at different spatial scales, none have explicitly identified sediment sources. Our goal was to quantify post-fire and post-salvage logging sediment yields and use rill patterns to identify sediment sources. We measured the extent and type of logging disturbance, length of rills per unit area or “rill density”, ground cover, and sediment yields in nine logged and five control small catchments or “swales”, 0.09 to 0.81 ha, for 5 years after the 2013 Rim Fire in California's Sierra Nevada. The logged swales had a mean ground disturbance of 31%. After the first wet season following logging, there was no difference in either mean rill density (0.071 and 0.088 m m⁻², respectively) or mean transformed, normalized sediment yields between the control and logged swales. Untransformed mean sediment yields across three sites ranged from 0.11–11.8 and 1.1–3.2 Mg ha⁻¹ for the controls and salvage-logged swales, respectively. Rill density was strongly related to sediment yield and increased significantly with the amount of high-traffic skid trail disturbance in logged swales. Rill density was not significantly related to the amount of bare soil despite a significant relationship between sediment yields and bare soil. Rills usually initiated in bare soil and frequently connected high traffic skid trails to the drainage network after being diverted by waterbars. Rill connectivity and sediment yields decreased in control and logged swales where vegetation or other surface cover was high, suggesting this cover disconnected rills from the drainage network. Increasing ground cover on skid trails and between areas disturbed by post-fire logging and stream channels may reduce sediment yields as well as the hydrologic connectivity between hillslopes and the drainage network.     

Nutrient dynamics in an alpine headwater stream: use of continuous water quality sensors to examine responses to wildfire and precipitation events

Stream water quality can change substantively during diurnal cycles, discrete flow events, and seasonal time scales. In this study, we assessed event responses in surface water nutrient concentrations and biogeochemical parameters through the deployment of continuous water quality sensors from March to October 2011 in the East Fork Jemez River, located in northern New Mexico, USA. Events included two pre‐fire non‐monsoonal precipitation events in April, four post‐fire precipitation events in August and September (associated with monsoonal thunderstorms), and two post‐fire non‐monsoonal precipitation events in October. The six post‐fire events occurred after the Las Conchas wildfire burned a significant portion of the contributing watershed (36%) beginning in June 2011. Surface water nitrate (NO₃? N) concentrations increased by an average of 50% after pre‐fire and post‐fire non‐monsoonal precipitation events and were associated with small increases in turbidity (up to 15 NTU). Beginning 1 month after the start of the large regional wildfire, monsoonal precipitation events resulted in large multi‐day increases in dissolved NO₃? N (6 × background levels), dissolved phosphate (100 × background levels), specific conductance (5 × background levels), and turbidity (>100 × background levels). These periods also corresponded with substantial sags in dissolved oxygen (<4 mg l^?1) and pH (<6.5). The short duration and rapid rates of change during many of these flow events, particularly following wildfire, highlight the importance of continuous water quality monitoring to quantify the timing and magnitude of event responses in streams and to examine large water quality excursions linked to catchment disturbance. Copyright © 2015 John Wiley & Sons, Ltd.     

When insurance and goodwill are not enough: Bushfire Attack Level (BAL) ratings,risk calculations and disaster resilience in Australia

ABSTRACT

Home and contents insurance is integral to household and community resilience against disasters. Yet many households are underinsured. While causes for underinsurance have been widely researched, changes to Australian building regulations in the last decade has established a new source of insurance miscalculations. Bushfire Attack Level (BAL) ratings can inflate rebuilding costs by 20% or more, yet BAL ratings remain obfuscated to homeowners and are notoriously confusing to navigate. After the October 2013 bushfires in New South Wales, the Blue Mountains Local Recovery Steering Group found that ‘information on the BAL process, the guidelines, the expected costs, the consulting experts and a property’s bushfire-prone status is literally all over the place’. This paper aims to provide clarity on the subject, tracing the precise socio-technical means through which disaster risk is perceived and assessed. The paper conceptualises insurance and risk ratings as calculative devices that provide both a technical solution to reduce financial losses and a philosophical tool for risk rationalisation. It then builds on interviews conducted with residents in the Blue Mountains affected by the 2013 bushfires, to ascertain how such calculative devices practically affect communities at risk. The paper concludes by outlining potential solutions to a confusing and costly problem in Australia, highlighting critical public awareness issues surround BAL ratings, which have profound insurance and wellbeing implications for people rebuilding and recovering from bushfire.     

Reply to “Comments on Climatology: The Challenge for the Eighties Revisited”

Book reviews in this article

The Heated Debate: Greenhouse Predictions Versus Climate Reality. ROBERT C. BALLING JR. San Francisco: Pacific Research Institute for Public Policy, 1992. xxxvi and 195 pp., diags., tables, index, and biblio. $21.95 cloth (ISBN 0-936488-47-6).

Mountain Weather and Climate, 2nd edition. ROGER G. BARRY. New York: Routledge, Chapman and Hall, 1992. xx and 402 pp., maps. diags., photos, index, and biblio. $89.95 cloth (ISBN 0-415-07112-7); $29.95 paper (ISBN 0-415-07113-5).

Late Quaternary Environmental Change: Physical and Human Perspectives. MARTIN BELL and MICHAEL J. C. WALKER. Essex, England: Longman Group, 1992. xiv and 273 pp., maps, diags., index, and biblio. $39.95 paper (ISBN 0-582-04514-2).

Planning for Earthquakes. PHILIP R. BERKE and TIMOTHY BEATLEY. Baltimore: The Johns Hopkins University Press, 1992. xv and 210 pp., maps, diags., photos, tables, app., acronyms, index, and biblio. $38.00 cloth (ISBN 0-8018-4255-7).

Industrialization and Development in the Third World. RAJESH CHANDRA. London: Routledge, 1992. xvii and 124 pp., maps, figs., photos, and index. $14.95 paper (ISBN 0-415-01380-1).

Waste Location: Spatial Aspects of Waste Management, Hazards and Disposal. MICHAEL CLARK, DENIS SMITH, and ANDREW BLOWERS, eds. London: Routledge, 1992. xv and 257 pp., maps, diags., index, and refs. $85.00 cloth (ISBN 0-415-04824-9).

Water Diversion and Export: Learning from Canadian Experience. J. C. DAY and FRANK QUINN. Waterloo, Ontario: Department of Geography, University of Waterloo, 1992. xx and 215 pp., 14 maps, 4 diags., 17 tables, 12 photos, glossary, and biblio. $25.00 (Can.) paper (ISBN 0-921083-42-4).

The Native Population of the Americas in 1492, 2nd edition. WILLIAM M. DENEVAN, ed. Madison: The University of Wisconsin Press, 1992. xxxviii and 353 pp., maps, figs., tables, index, biblio. $45.00 cloth (ISBN 0-299-134-30-X); $14.95 paper (ISBN 0-299-13434-2).

Touring North America (series). ANTHONY R. DE SOUZA, ed. New Brunswick: Rutgers University Press, 1992. 13 volumes; pages varying from approximately 100 to approximately 300 each; maps, diags., indices, and biblios. $9.95 each paperback; $25.00 each volume in cloth; boxed gift set of all 13 volumes in paperback $129.95. (ISBNs for cloth and paperback editions range from 0-8135-1870-9 to 0-8135-1895-4 inclusive).

Urban Transport Planning: A Developmental Approach. HARRY T. DIMITRIOU. New York: Routledge, 1992. xviii and 346 pp., diags., index, and biblio. $92.50 cloth (ISBN 0-415-03857-X).

Colonialism and Development in the Contemporary World. CHRIS DIXON and MICHAEL HEFFERNAN, eds. Rutherford, NJ: Mansell, 1991. viii and 232 pp., maps, diags., index, and biblio. $70.00 cloth (ISBN 0-7201-2072-1).

The Betweenness of Place: Towards a Geography of Modernity. J. NICHOLAS ENTRIKIN. Baltimore: The Johns Hopkins University Press, 1991. xii and 196 pp., notes, and indices. $38.50 cloth (ISBN 0-8018-4083-X); $13.95 paper (ISBN 0-8018-4084-8).

The Women Outside: Meanings and Myths of Homelessness. STEPHANIE GOLDEN. Berkeley: University of California Press, 1992. ix and 265 pp., index and biblio. $25.00 cloth (ISBN 0-520-07158-1).

The Transformation of Agriculture in the West. DAVID GRIGG. Oxford, England, and Cambridge, MA: Basil Blackwell, 1992. xiv and 141 pp., maps, diags., index, and biblio. $19.95 paper (ISBN 0-631-17094-4).

Derelict Landscapes: The Wasting of America's Built Environment. JOHN A. JAKLE and DAVID WILSON. Savage, MD: Rowman and Littlefield, 1992. xviii and 342 pp., illus., index, biblio. $65.00 cloth (ISBN 0-8476-7735-4); $23.50 paper (ISBN 0-8476-7736-2).

Iranian Cities: Formation and Development. MASOUD KHEIRABADI. Austin: University of Texas Press, 1991. xiv and 132 pp., maps, diags., photos, appendices, notes, glossary, biblio., and index. $27.50 cloth (ISBN 0-292-72468-3).

The Pentagon and the Cities. ANDREW KIRBY, ed. Newbury Park, CA: Sage Publications, 1991. Urban Affairs Annual Reviews, vol. 40. x and 207 pp., tables, maps, index, and biblio. $43.95 cloth (ISBN 0-8039-3845-4); $19.95 paper (ISBN 0-8039-3846-2).

Geographic Perspectives on Soviet Central Asia. ROBERT A. LEWIS, ed. London and New York: Routledge, 1992. xv and 323 pp., maps, diags., index, and biblio. $69.95 cloth (ISBN 0-415-07592-0).

Conquest and Survival in Colonial Guatemala: A Historical Geography of the Cuchumatan Highlands, 1500–1821. W. GEORGE LOVELL. Montreal and Kingston: McGill-Queen's University Press, 1992. xxxviii and 279 pp., maps, diags., glossary, notes, index, and biblio. $19.95 paper (ISBN 0-7735-0903-8).

Contested Lands: Conflict and Compromise in New Jersey's Pine Barrens. ROBERT J. MASON. Philadelphia: Temple University Press, 1992. xii and 257 pp., maps, tables, index, and biblio. $44.95 cloth (ISBN 0-87722-925-2).

Making Sense of Place: Children's Understanding of Large-Scale Environments. M. H. MATTHEWS. Savage, MD: Harvester Wheatsheaf, Barnes and Noble Books, 1992. xiv and 271 pp., maps, diags, tables, index, and biblio. $54.50 cloth (ISBN 0-389-20987-2).

Sources of Metropolitan Growth. EDWIN S. MILLS and JOHN F. MCDONALD, eds. New Brunswick: Center for Urban Policy Research Press, 1992. xxvii and 306 pp., maps, diags., index, and biblio. $29.95 cloth (ISBN 0-88285-135-7).

Resource Management in Developing Countries. PETER H. OMARAOJUNGU. Harlow, England: Longman, 1992. xvi and 213 pp., maps, diags., tables, index, and biblio. $39.95 paper (ISBN 0-582-30102-5).

A Moveable Shore: The Fate of the Connecticut Coast. PETER C. PATTON and JAMES M. KENT. Durham: Duke University Press, 1992. viii and 143 pp., maps, diags., index, and biblio. $49.95 cloth (ISBN 0-8223-1128-3); $19.95 paper (ISBN 0-8223-1147-X).

Agricultural Reform in China: From Communes to Commodity Economy 1978–1990. SIMON G. POWELL. Manchester, England: Manchester University Press, 1992. viii and 231 pp., maps, diags., tables, and biblio. $69.95 cloth (ISBN 0-7190-3382-9).

The Caribbean in the Wider World, 1492–1992: A Regional Geography. BONHAM C. RICHARDSON. Cambridge: Cambridge University Press, 1992. xvi and 235 pp., maps, tables, index, and biblio. $49.95 cloth (ISBN 0-521-35186-3); $16.95 paper (ISBN 0-521-35977-5).

Scavengers, Recyclers, and Solutions for Solid Waste Management in Indonesia. DANIEL T. SICULAR. Berkeley: Center for Southeast Asian Studies, University of California at Berkeley, 1992. xii and 197 pp., maps, tables, photos, glossary, biblio., and index. $16.50 paper (ISBN 0-944613-13-6).

The Sphinx in the City: Urban Life, the Control of Disorder, and Women. ELIZABETH WILSON. Berkeley: University of California Press, 1992. 191 pp., plates, index, and biblio. $35.00 cloth (ISBN 0-520-07850); $14.00 paper (ISBN 0-520-07864-0).

The Cultural Geography of the United States: A Revised Edition. WILBUR ZELINSKY. Englewood Cliffs: Prentice Hall, Inc., 1992. ix and 226 pp., maps, diags., index, and biblio. $21.95 paper (ISBN 0-13-194424-X).     

Water balance of a burned and unburned forested boreal peatland

We examined the water balance of a forested ombrotrophic peatland and adjacent burned peatland in the boreal plain of western Canada over a 3‐year period. Complete combustion of foliage and fine branches dramatically increased shortwave radiation inputs to the peat surface while halting all tree transpiration at the burned site. End‐of‐winter snowpack was 7–25% higher at the burned site likely due to decreased ablation from the tree canopy at the unburned site. Shrub regrowth at the burned site was rapid post‐fire, and shading by the shrub canopy in the burned site approached that of the unburned site within 3 years after fire. Site‐averaged surface resistance to evaporation was not different between sites, though surface resistance in hollows was lower in the burned site. Water loss at both burned and unburned sites is largely driven by surface evaporative losses. Evaporation at the burned site marginally exceeded the sum of pre‐fire transpiration and interception at the unburned site, suggesting that evapotranspiration during the growing season was 20–40 mm greater at the burned peatland. Although the net change in water storage during the growing season was largely unchanged by fire, the lack of low‐density surface peat in the burned site appears to have decreased specific yield, leading to greater water table decline at the burned site despite similar net change in storage. Copyright © 2013 John Wiley & Sons, Ltd.     

Stream exports of coarse matter and phosphorus following wildfire in NE Victoria,Australia

The temporal change in total phosphorus (TP) export from two burnt upland catchments is reported. Following wildfire in January 2003, two burnt forested headwater catchments (136 and 244 ha) in the East Kiewa valley, Victoria, were instrumented to measure discharge, turbidity and to collect stream water samples. In addition, samplers were positioned in the stream bed at the outlet of each catchment to continuously sample material transported along the bed of the stream. Approximately, every 2 weeks, the material collected by the stream bed samplers was weighed and sub‐sampled. The percentage of coarse (>1 and < 5 mm in diameter) mineral (including soil aggregates) and organic matter was determined and then analysed for TP. Between the first and third years after fire, sampled coarse matter and associated TP loads decreased by an average of 53% and 62%, respectively. Over the 3‐year study, the amount of coarse matter exported during winter/spring decreased considerably, whereas export rates during summer/autumn remained relatively constant. Coarse matter exports were estimated to be approaching pre‐fire levels after 3–4 years. Results on total suspended solids (TSS) TP and total dissolved phosphorus (TDP) from a parallel study are incorporated to explore TP partitioning. TP exported with TSS dominated the total TP export loads, with coarse matter TP and TDP each contributing approximately 10% over the study period. Copyright © 2010 John Wiley & Sons, Ltd.     

Effects of 2003 wildfires on stream chemistry in Glacier National Park,Montana

Changes in stream chemistry were studied for 4 years following large wildfires that burned in Glacier National Park during the summer of 2003. Burned and unburned drainages were monitored from December 2003 through August 2007 for streamflow, major constituents, nutrients, and suspended sediment following the fires. Stream‐water nitrate concentrations showed the greatest response to fire, increasing up to tenfold above those in the unburned drainage just prior to the first post‐fire snowmelt season. Concentrations in winter base flow remained elevated during the entire study period, whereas concentrations during the growing season returned to background levels after two snowmelt seasons. Annual export of total nitrogen from the burned drainage ranged from 1·53 to 3·23 kg ha^?1 yr^?1 compared with 1·01 to 1·39 kg ha^?1 yr^?1 from the unburned drainage and exceeded atmospheric inputs for the first two post‐fire water years. Fire appeared to have minimal long‐term effects on other nutrients, dissolved organic carbon, and major constituents with the exception of sulfate and chloride, which showed increased concentrations for 2 years following the fire. There was little evidence that fire affected suspended‐sediment concentrations in the burned drainage. Sediment yields in subalpine streams may be less affected by fire than in lower elevation streams because of the slow release rate of water during spring snowmelt. Published in 2008 by John Wiley & Sons, Ltd.