Causes of Post-Fire Runoff and Erosion: Water Repellency, Cover, or Soil Sealing?
Isaac J. Larsen, Lee H. MacDonald, Ethan Brown, Daniella Rough, Matthew J. Welsh, Joseph H. Pietraszek, Zamir Libohova, Juan de Dios Benavides-Solorio, Keelin Schaffrath. 2009. Causes of Post-Fire Runoff and Erosion: Water Repellency, Cover, or Soil Sealing? Soil Sci. Soc. Am. J. 73:1393-1407
Full text [here, 2.1MB]
Selected excerpts:
Abstract
Few studies have attempted to isolate the various factors that may cause the observed increases in peak flows and erosion after high-severity wildfires. This study evaluated the effects of burning by: (i) comparing soil water repellency, surface cover, and sediment yields from severely burned hillslopes, unburned hillslopes, and hillslopes where the surface cover was removed by raking; and (ii) conducting rainfall simulations to compare runoff , erosion, and surface sealing from two soils with varying ash cover. The fire-enhanced soil water repellency was only stronger on the burned hillslopes than the unburned hillslopes in the first summer after burning. For the first 5 yr after burning, the mean sediment yield from the burned hillslopes was 32 Mg ha-1, whereas the unburned hillslopes generated almost no sediment. Sediment yields from the raked and burned hillslopes were indistinguishable when they had comparable surface cover, rainfall erosivity, and soil water repellency values. The rainfall simulations on ash-covered plots generated only 21 to 49% as much runoff and 42 to 67% as much sediment as the plots with no ash cover. Soil thin sections showed that the bare plots rapidly developed a structural soil seal. Successive simulations quickly eroded the ash cover and increased runoff and sediment yields to the levels observed from the bare plots. The results indicate that: (i) post-fire sediment yields were primarily due to the loss of surface cover rather than fire-enhanced soil water repellency; (ii) surface cover is important because it inhibits soil sealing; and (iii) ash temporarily prevents soil sealing and reduces post-fire runoff and sediment yields.
Introduction
Wildfires increase hillslope- and watershed-scale runoff and sediment yields by several orders of magnitude (e.g., Prosser and Williams, 1998; Robichaud and Brown, 1999; Moody and Martin, 2001; Benavides-Solorio and MacDonald, 2005; Malmon et al., 2007). Land use and climate change have increased, or are projected to increase, the size and frequency of fires in many wildland environments (e.g., Mouillot et al., 2002; Hennessy et al., 2005; Westerling et al., 2006). The increase in fire risk is generating considerable concern about the potential adverse effects on water quality, aquatic habitat, and water supply systems (Rinne, 1996; Robichaud et al., 2000; Moody and Martin, 2001; Burton, 2005).
The large increases in runoff and sediment yields after high-severity fires have been attributed to several factors, including: (i) soil water repellency (DeBano, 2000; Doerr et al., 2000); (ii) loss of surface cover ( Johansen et al., 2001; Pannkuk and Robichaud, 2003); (iii) soil sealing by sediment particles (Lowdermilk, 1930; Neary et al., 1999); and (iv) soil sealing by ash particles (Mallik et al., 1984; Etiégni and Campbell, 1991). The problem is that the relative contribution of each factor to the observed increases in post-fire runoff and sediment yields is largely unknown (Shakesby et al., 2000; Letey, 2001). This lack of understanding hampers our ability to predict post-fire sediment yields and design effective post-fire rehabilitation treatments.
Impacts of California Wildfires on Climate and Forests: A Study of Seven Years of Wildfires (2001-2007)
Thomas M. Bonnicksen. 2009. Impacts of California Wildfires on Climate and Forests: A Study of Seven Years of Wildfires (2001-2007). FCEM Report No. 3. The Forest Foundation, Auburn, CA.
Full text [here]
See also FCEM Reports No. 1 and 2 [here]
Selected Excerpts:
Executive Summary
This study (FCEM Report No. 3) and the previous study (FCEM Report No. 2), use a new computer model, the Forest Carbon and Emissions Model (FCEM), to estimate greenhouse gas emissions from wildfires and insect infestations, and opportunities to recover these emissions and prevent future losses.
This report shows that the wildfires that scorched California from 2001 to 2007 seriously degraded the state’s forests and contributed to global warming. Political and economic obstacles to managing forests and restoring burned forests are the root causes of the wildfire crisis.
The impact of California’s wildfires on climate and forests is one of the most important issues of our time. It is imperative to take action now to prevent the annual recurrence of disastrous and costly fire seasons.
The wildfire crisis is becoming more serious each year. Fires are getting bigger, more destructive, and more expensive. In 2001, California wildfires burned one-half million acres. In 2007, 1.1 million acres burned, and an estimated 1.4 million acres burned in 2008 destroying 1,000 homes. This was the most destructive fire season in the state’s history and 2009 could be worse.
From 2001 to 2007, fires burned more than 4 million acres and released an estimated 277 million tons of greenhouse gases into the atmosphere from combustion and the post-fire decay of dead trees. That is an average of 68 tons per acre. These wildfires also kill wildlife, pollute the air and water, and strip soil from hillsides. The greenhouse gases they emit are wiping out much of what is being achieved to reduce emissions from fossil fuels to battle global warming.
The emissions from only the seven years of wildfires documented in this study are equivalent to adding an estimated 50 million more cars onto California’s highways for one year, each spewing tons of greenhouse gases. Stated another way, this means all 14 million cars in California would have to be locked in a garage for three and one-half years to make up for the global warming impact of these wildfires.
Aspen: A Vanishing Resource
Charles E. Kay. 2009. Aspen: A Vanishing Resource. Mule Deer Foundation Magazine, No. 25, pp. 32-39.
Full text (without photos):
I have conducted scientific research on aspen for more than 25 years. During that time, I have personally measured more aspen stands in a greater number of locations than any other ecologist, living or dead. I have also personally measured more aspen exclosures than any person who has ever lived. In addition, I have made more than 800 repeat photosets depicting aspen.
My research, as well as that for others, has documented a major decline in aspen throughout intermountain North America since European settlement. Historical research and repeat photographs indicate that declines of 60% to 90% are common. My home state of Utah, for example, once contained over two million acres of aspen, but today there are less than 800,000 acres and aspen is still being lost. Moreover, many western aspen stands contain old-age or single-age trees and have not successfully regenerated for 80 years or longer. Colorado and other areas in the West have recently experienced the demise of large blocks of aspen — termed Sudden Aspen Decline Syndrome. All this should be of critical concern to readers of Muley Crazy because aspen provides ideal habitat for mule deer. IDEAL! Or at least it once did.
Before we can understand why aspen has declined, why aspen is still in serious freefall, and what we and the land management agencies can do to reverse that trend, a short lesson in aspen autecology is in order. We also need to dispel some serious myths about aspen. First, as any textbook will tell you, aspen is the most widely distributed tree in North America. Second, aspen is a clonal species and what we commonly call trees are actually ramets, having risen from a common root source via suckering. This means that the clone is the individual, not each tree. Moreover, many western aspen clones are quite large, often an acre or more in size, and one clone on Utah’s Fishlake National Forest, named Pando, has been identified as the largest living organism on Earth — a fact recently confirmed by genetic analysis. Pando covers approximately 106 acres, contains an estimated 50,000 trees (ramets), and weighs approximately 6,000 tons.
In a landscape dominated by large blocks of aspen, individual clones are easiest to spot during spring leaf-out or during autumn, as different clones produce new leaves at slightly different rates and turn color, or different colors, at slightly different times. One would have to be very cold-hearted not to appreciate aspen in all its golden fall splendor! This is why, when asked, I tell everyone that I study charismatic megaFLORA! There is nothing quite like hunting mule deer, or elk, in aspen during autumn, expect perhaps chasing gray ghosts in the lowveld.
In most years, aspen produces millions of viable seeds, but seedings and clonal establishment from seed are virtually non-existent. To survive, aspen seedlings need bare mineral soil, no competing vegetation, and high soil moisture throughout germination and the first summer of life. Conditions that simply do not exist in the West today. Given aspen’s demanding seedbed requirements, it is thought that the environment has not been conducive to seedling growth and the widespread establishment of new clones since shortly after the glaciers retreated 10,000 or more years ago. This means that the clones you see in the West today have likely survived for thousands of years via vegetative, also called asexual, reproduction or regeneration.
Testimony of Dr. Peter Kolb on Mountain Pine Beetle
Peter Kolb. 2009. Testimony of Dr. Peter Kolb, Montana State University, before the House Natural Resources Subcommittee on Water and Power Hearing on Mountain Pine Beetle: Strategies For Protecting The West, June 16, 2009.
Full text [here]
Selected excerpts:
My name is Peter Kolb, and I am the Montana State University Extension Forestry Specialist and an Associate Professor of Forest Ecology and Management at the University of Montana College of Forestry and Conservation. I’m here today speaking on behalf of the Society of American Foresters (SAF), an organization of over 15,000 forest managers, researchers, and educators. I’ve been a SAF member for 27 years.
I am here today to offer you my testimony with regard to the bark beetle situation across western forests with specific reference to the conditions across the Montana with which I am most familiar. My perspective is not that of an entomologist, but that of a forest ecologist and management specialist whose main work objective is to help implement the results and conclusion of scientific research into practical working applications. I work in both academic circles as an applied researcher and educator, and in the forest practitioners’ realm, which gives me the opportunity not only to conduct relevant research, but to examine the effects of forestry applications. Just three days ago I returned from a week of working with family landowners and the Cree and Chippewa tribes of central Montana where we examined the forest conditions there and the effectiveness of various forest practices in combating a mountain pine beetle outbreak in the Bearpaw Mountains.
Bark Beetles
The bark beetle outbreak we are experiencing across the entire western portion of North America is the result of multiple ecological factors converging at the same time. Its occurrence is not a surprise for foresters across western forests as the current expansiveness of bark beetle activity has been building for many years. Bark beetles such as mountain pine beetles, one of the main culprits in the current outbreaks, have been extensively studied since the mid 1970s. Its life cycle and ecology are very well understood. It has been a natural part of western forests for millennia and its population cycles are fairly predictable. Under what we would characterize the average forest and climatic conditions of the past century it exists as a chronic population within pine forests, colonizing and killing trees that are unable or incapable of defending themselves due to a variety of physiological, genetic or environmental factors. It may be considered analogous to wolves circling a herd of caribou, culling out the weak, unfit and injured. As with any species, bark beetles have numerous pests and predators themselves including a variety of predatory beetles, wasps, nematodes, mites, fungal diseases, and larger predators such as bark gleaning birds and woodpeckers. Depending on the populations of these predators and pests, chronic bark beetle populations might be kept in check.
People of the Prairie, People of the Fire
Stephen Pyne. 2009. People of the Prairie, People of the Fire. The Wildland Fire Lessons Learned Center.
*****
Dr. Stephen J. Pyne is Regents Professor at Arizona State University. He is author of Awful Splendour: A Fire History of Canada (2007) Univ. British Columbia Press, Fire in America: A Cultural History of Wildland and Rural Fire (1982), Burning Bush: A Fire History of Australia (1991), World Fire: The Culture of Fire on Earth (1995), Vestal Fire: An Environmental History, Told Through Fire, of Europe and Europe’s Encounter with the World (1997), The Ice: A Journey to Antarctica (1986), and numerous other histories, memoirs, essays, and texts about fire.
This essay is one of three related essays about fire in the Midwest. The others are:
Missouri Compromise [here], and
Patch Burning [here]
*****
Full text [here]
Selected excerpts:
Twice over the past 20,000 years the Illinois landscape has been destroyed and rebuilt. In the first age the agent of change was ice, mounded into sheets and leveraged outward through a suite of periglacial processes from katabatic winds to ice-dam-breaching torrents. The ice obliterated everything, leaving as its legacy a geomorphic matrix of dunes, swales, moraines, loess, great lakes and landscape-dissecting streams.
For the second, the agent was iron, forged into plows and then into rails. Coal replaced climate as a motive force, and people pushed aside the planetary rhythms of Milankovitch cycles and cosmogenic carbon cycles as a prime mover. They left behind a surveyed landscape of squared townships.
The first event worked through a geologic matrix; the second, a biological one; and they were equally thorough. All the state went under ice at least once; the last outpouring, the Wisconsin glaciation, pushed south from Lake Michigan and covered perhaps a third. The frontier of agricultural conversion put nearly all of the state to the plow, or where rocky moraines prevented it, to the hoofs of livestock. When it ended, only one-tenth of one percent of the precontact landscape remained more or less intact. Less than one acre out of a thousand held its founding character, and that acre was itself minced into a thousand, scattered pieces.
In both ice age and iron age, however, life revived after the extinction with fire as an informing presence – fire in the hands of people. The biological recolonization of the landscape after the ice had fire in its mix and expressed itself as oak savannas, tallgrass prairies, and grassy wetlands, stirred by routine burning. Fire was a universal catalyst; in particular, prairie and fire became ecological symbionts. The reconstruction of the second landscape has relied on industrial combustion, fueled by the fossil fallow of biomass.
But those intent on sparing, or actively restoring, the former landscape must appeal to open burning. A fire sublimated through a tractor does not yield the same effects as one let loose to free-burn through big bluestem. The regeneration of such settings is troubling –- unstable and scattered, an inchoate genesis still in the making, its reliance on fire both essential and challenged.
Patch Burning
Stephen Pyne. 2009. Patch Burning. The Wildland Fire Lessons Learned Center.
*****
Dr. Stephen J. Pyne is Regents Professor at Arizona State University. He is author of Awful Splendour: A Fire History of Canada (2007), Univ. British Columbia Press, Fire in America: A Cultural History of Wildland and Rural Fire (1982), Burning Bush: A Fire History of Australia (1991), World Fire: The Culture of Fire on Earth (1995), Vestal Fire: An Environmental History, Told Through Fire, of Europe and Europe’s Encounter with the World (1997), The Ice: A Journey to Antarctica (1986), and numerous other histories, memoirs, essays, and texts about fire.
This essay is one of three related essays about fire in the Midwest. The others are:
Missouri Compromise [here], and
People of the Prairie, People of the Fire [here]
*****
Full text [here]
Selected excerpts:
It is a biotic border that spans a continent, and it displays a continental sized roughness. In rude terms it traces the coarse shoreline between a sea of grass to the west and a land of mixed forests to the east, an edge sculpted into the ecological equivalent of bays, narrows, skerries, and estuaries, as climatic tides, the tectonic lurching of glaciers, and the sprawl of colonizing species have tugged and twisted, and here and there allowed grass or woods to mostly prevail. That textured shoreline holds a jumbled geography of incombustible wetlands and free-burning bottomlands, fire-flushed Barrens and fire-hardened forests, prairie peninsulas and prairie patches, oak mottes and woody copses, and landscapes latent with bits of them all, some extending over hundreds of miles.
It is a fractal frontier, patchy at every scale, with small patches within larger. And it is a frontier of fire, with each part checked or boosted by the ferocity and abundance of burning.
Cross Timbers
Even so, the Cross Timbers stand out. They proclaim a bold, woody headland, as distinctive as the White Cliffs of Dover, between the grassy sea that swells to the west and the humid forest that crowds the east. It is here that storm surges of fire, roaring over the long fetch of the Great Plains, whipped by the westerlies into whitecaps of flame, crash against the less combustible woods. The belt is long, stretching from the Edwards Plateau of Texas to the Flint Hills of Kansas; irregular and sinuous, roughly cruciform, historically varying from five to 30 miles wide, but at places spanning most of Oklahoma; and persistent, its 4.8 million hectares defying settlement’s attempts to log, plow, graze, or burn it into oblivion. Instead, it continues in Oklahoma to thicken with stubborn oaks – blackjack, shin, live, and post.
Bushfires, Prescribed Burning, and Global Warming
Roger Underwood, David Packham, and Phil Cheney. 2008. Bushfires, Prescribed Burning, and Global Warming. Bushfire Front Inc. Occasional Paper No 1, April 2008 [here]
Roger Underwood is a former General Manager of the Department of Conservation and Land Management (CALM) in Western Australia, a regional and district manager, a research manager and bushfire specialist. Roger currently directs a consultancy practice with a focus on bushfire management and is Chairman of The Bushfire Front Inc.. He lives in Perth, Western Australia.
David Packham is Senior Research Fellow, School of Geography and Environmental Science, Monash University, Victoria.
Phil Cheney is Honorary Research Fellow, CSIRO, Canberra, ACT
Full text:
This is not a paper about climate change or the contentious aspects of the climate debate. Our interest is bushfire management. This is an activity into which the debate about climate change, in particular “global warming”, has intruded, with potentially damaging consequences.
Australia’s recent ratification of the Kyoto Treaty has been welcomed by people concerned about the spectre of global warming. However, the ratification was a political and symbolic action, and will have no immediate impact on the volume of carbon dioxide (CO2) in the atmosphere, and therefore will not influence any possible relationship between CO2 emissions and global temperatures.
However, the ratification could have an impact on Australian forests. Spurious arguments about the role of fire contributing to carbon dioxide emissions could be used to persuade governments and management agencies to cease or very much reduce prescribed burning under mild conditions.
Decades of research and experience has demonstrated that fuel reduction by prescribed burning under mild conditions is the only proven, practical method to enable safe and efficient control of high-intensity forest fires.
Two myths have emerged about climate change and bushfire management and are beginning to circulate in the media and to be adopted as fact by some scientists:
1. Because of global warming, Australia will be increasingly subject to uncontrollable holocaust-like “megafires”.
2. Fuel reduction by prescribed burning must cease because it releases carbon dioxide into the atmosphere, thus exacerbating global warming and the occurrence of megafires.
Both statements are incorrect. However they represent the sort of plausible-sounding assertions which, if repeated often enough, can take on a life of their own and lead eventually to damaging policy change.
Watershed Response to Western Juniper Control
Timothy L. Deboodt. 2008. Watershed Response to Western Juniper Control. Dissertation for the degree Doctor of Philosophy in Rangeland Ecology and Management, Oregon State University, presented on May 8, 2008.
Full text [here] (4.6 MB)
Abstract:
Western juniper (Juniperus occidentalis) encroachment has been associated with increased soil loss and reduced infiltration resulting in the loss of native herbaceous plant communities and the bird and animal species that rely on them. Hydrologically, however, change in water yield has been linked with the amount of annual precipitation a site received. Studies published in the 1970’s and 1980’s, suggest that a minimum 450 mm (18 inches) of annual precipitation was necessary before an increase in water yield manifested itself following vegetation manipulation.
In 1993, a paired watershed study was initiated in the Camp Creek drainage, a tributary of the Crooked River of central Oregon, to evaluate the impacts of cutting western juniper on the hydrologic function of those sites. The study involved a paired watershed approach using watersheds of approximately 110 hectares (270 acres) each to evaluate changes in a system’s water budget following the reduction of western juniper.
The 30 year average annual precipitation for the area is 350 mm (13.75) and during the study period, annual precipitation ranged from 80 percent to 129 percent of average. In 2005, following 12 years of pretreatment monitoring in the 2 watersheds (Mays and Jensen) all post-European aged juniper (juniper < 140 years of age) were cut from the treatment watershed (Mays).
Analysis indicated that juniper reduction significantly increased late season spring flow by 225 percent (alpha > .05), increased days of recorded ground water by an average of 41 days (alpha > .05) and increased the relative availability of late season soil moisture at soil depths of .76 m (27 inches) (alpha > 0.1).
Reconstructing the Fire History of the Jarrah Forest of south-western Australia
David Ward and Gerard Van Didden. 1997. Reconstructing the Fire History of the Jarrah Forest of south-western Australia. A Report to Environment Australia under the Regional Forest Agreement December 1997.
David Ward is Senior Research Scientist, Department of Conservation and Land Management (CALM) in Western Australia and Visiting Senior Research Fellow, Curtin University, Perth
Gerard Van Didden is a Retired Department of Conservation and Land Management officer
Full text [here]
Selected excerpts:
Introduction
… The jarrah forest is a complicated system, involving humans for thousands of years. Anthropologists tell us of the importance of fire in Aboriginal culture, and there is historical evidence in the letters and journals of early European explorers of south-western Australia that fires occurred as frequently as every 2-4 years, at least in some parts. …
This study reconstructs fire history from marks on the stems of grasstrees (Xanthorrhoea spp). This information meshes with the broad perspectives of history and anthropology, giving a framework within which we can link the concerns of biologists, soil scientists, fire fighters, and managers. In turn, the framework can be used to create a map of consciously linked research questions, relevant to management of the jarrah forest. …
Methods
Grasstree (Xanthorrhoea spp) stems were cleaned with a grinder, so exposing cream and brown growth rings (Ward 1996), which match with internal growth bumps (Lamont and Downes 1979). The grinding also exposed some bands of dark pigment in the old leaf bases. These dark bands occurred consistently at points on the stems where fires were known from CALM records to have occurred; and where fires were likely to have occurred, since the grasstree had flowered at that point. …
Xanthorrhoea thorntonii. Photo courtesy Department of Conservation and Land Management [here]
Some leafbases were carefully removed, washed in alcohol, and cut into 1 centimetre pieces measured from the proximal end. The length of leafbase can vary from tree to tree due to burning away by past fires (Drummond 1847). In this case each leafbase gave 5 pieces. Each year showed the twin band of cream and brown leafbases shown in Figure 1, and these were separated, giving a hundred samples for the decade. These samples were analysed by pyrolysis gas chromatography and mass spectrometry to identify the dark pigment (Challinor 1989, 1995). They were also analysed for zinc, calcium, magnesium, manganese and copper. …
Australian Bushfire Management: a case study in wisdom versus folly
Roger Underwood. 2009. Australian Bushfire Management: a case study in wisdom versus folly
Roger Underwood is a renowned Australian forester with fifty years experience in bushfire management and bushfire science. He has worked as a firefighter, a district and regional manager, a research manager and senior government administrator. He is Chairman of The Bushfire Front, an independent professional group promoting best practice in bushfire management.
One man’s wisdom is another’s folly - Ralph Waldo Emerson
Many years ago, still a young man, I watched for the first time the grainy, flickering black and white film of the British infantry making their attack on the opening day of the Battle of the Somme. The stark and terrible footage shows the disciplined soldiers climbing from their trenches and, in line abreast, walking slowly across no-man’s land towards the enemy lines. They scarcely travel a few paces before the German machine gunners open up. They are mown down in their thousands. They are chaff before a wind of fire.
I can still remember being struck nerveless by these images, and later my anger when I realised what that calamitous carnage represented. It spoke of the deep incompetence of the Generals who devised this strategy of doom and then insisted upon its implementation. It spoke of front-line men led by people without front-line experience. It spoke of battle planners unable to think through the consequences of their plans, and who devalued human lives. It spoke of a devastating failure of the human imagination.
Worst of all, the strategies of the World War I Generals demonstrated that they had not studied, or that they had forgotten, the lessons of history. In the final year of the American Civil war, 50 years earlier, the Union army had been equipped for the first time with Springfield repeating rifles, replacing the single shot muskets they had previously used and still were being used by the Confederate army. The impact on Confederate soldiers attacking defenders armed with repeating rifles was identical to that later inflicted by machine guns on the Western Front. But it was a lesson unlearnt, of collective wisdom unregarded.
None of you will have any difficulty in seeing where this analogy is taking me.
The catastrophic bushfires in Victoria this year, and the other great fires of recent years in Victoria, New South Wales, the ACT and South Australia are dramatic expressions not just of killing forces unleashed, but of human folly. No less than the foolish strategies of the World War I Generals, these bushfires and their outcomes speak of incompetent leadership and of failed imaginations. Most unforgivable of all, they demonstrate the inability of people in powerful and influential positions to profit from the lessons of history and to heed the wisdom of experience.
