Bob Zybach, PhD

Program Manager,



Presentation Time

Friday, September 8, 2006, 12:00 PM


Mystery of the 16th Century: Kalapuya-Amin Cultural Landscapes of 1450 and 1750

Handout: Kalapuyan Perspectives: Recorded Memories of Tribal Elders. Excerpt from B. Zybach 1999 OSU MAIS thesis: Appendices C-I [see pages 250-251; 300-318].

PowerPoint Presentation. 47 JPG slides.

Select Bibliography

Presentation Summary

During the course of the last century, hundreds of people have counted and recorded the rings of thousands of trees throughout the Oregon Coast Range and Willamette Valley. A common result of these efforts is tree species, sizes, ages, and distribution have become known and documented over a large portion of the region. Very few of these trees have exceeded 400 years age, and none are known to have achieved 600 years; that is, almost all old-growth Coast Range and Willamette Valley trees measured since the 1800s began to grow sometime after 1500. Before 1700 or 1750, these same trees were seedlings, saplings, and second-growth, and old-growth (trees less than 200 years old) hardly existed at all in the landscape.

No one knows why.

This is an important finding for several reasons. The Oregon Coast Range and Willamette Valley contain many of the largest and fastest growing forest tree species in the world. Yet Douglas-fir, Sitka spruce, western hemlock, redcedar, black cottonwood, red alder, and white oak all tend to live much longer in other regions of the Pacific Northwest. Douglas-fir, for example, is known to reach ages of 750, 1000, or even more years in areas of the western Cascades, Olympic Peninsula, or Vancouver Island; but not in the Oregon Coast Range or Willamette Valley, where it very rarely achieves an age of 500 years. The same general pattern is true for white oak throughout the Willamette Valley, where the vast majority of old-growth trees are also less than 500 years old.

Something happened in western Oregon during the 1500s that resulted in widespread forestation of several different tree species in the 16th and 17th century. Common speculation among several forest scientists is that catastrophic forest fires deforested much of western Oregon during that time, including almost all coastal forests. The stated assumption of these scientists is that the fires burned across vast tracts of old-growth, but little evidence exists to support that belief. If such fires did occur, it seems as likely they burned grass, ferns, saplings, or second-growth as older trees. Lightning fires are rare in the region, and historical fires of similar magnitude, such as those that occurred from 1849 until 1951 (the individually named "Great" Yaquina, Nestucca, Coos, and Tillamook Fires), were all caused by people.

Were human populations far greater in the 1400s than the 1500s, thus requiring many more cooking fires and widespread land management practices? Would a catastrophic reduction in local human populations necessarily result in rapid forest expansion? Or could other factors, such as catastrophic winds, diseases, or insect infestations, been a cause?

Catastrophic fires hypothesis

If this hypothesis is accurate, there should have been a huge influx of carbon in lakes, swamps, and soil horizons resulting from the fires and decomposition of trees. This layer of organic material should have formed a regional "marker" (Zybach 1999: 247-249) readily identifiable by scientists engaged in soil studies, palynology, or analysis of lake sediments. To date, no such marker has been noted (Impara 1997: 265). Other possible markers, such as old stumps, snags, or fallen trees, should have been noted and documented by early journalists, painters, or photographers, but there is nothing there, either. No evidence exists -- other than the unexplained absence of old-growth trees of a certain age -- that widespread catsrophic wildfires covered 90% or more of the Oregon Coast Range and the Willamette Valley during the 16th cenury.

Reduction in Indian burning practices hypothesis

Was widespread conifer forestation throughout the Oregon Coast Range in the 1500s and 1600s possibly triggered by a significant decline in Indian populations? Some evidence suggests large numbers of people died on the Coast Range between 1500 and 1550 (Denevan 1992). If so, a number of processes may have occurred on a grand scale similar to what happened after 1775, 1830, 1850; that is, a widespread afforestation of Indian prairies, brakes, balds and savannahs would have likely occurred. This process has been observed in the eastern US as well. For example, William Wood, who lived in Massachusetts Bay colony from 1629 to 1633, wrote:

"it being the custom of the Indians to burne the wood in November, when the grasse is withered, and leaves dryed, it consumes all the underwood, and rubbish, which otherwise would over grow the Contrey, making it unpassable, and spoyle their much affected hunting; so that by this meanes in those places where the Indians inhabit, there is scarce a bush or bramble, or any cumbersome underwood to bee seene in the more champion ground . . . In some places where the Indians died of the Plague some foureteene yeares agoe, is much underwood, as in the mid way betwixt Wessaguscus and Plimouth, because it hath not beene burned" (Russell 1983: 82).

Assuming this hypothesis is correct: With the massive loss of lives, homes, and communities and the threat of white invaders, survivors would likely be less inclined to venture into isolated areas away from towns and established campgrounds. Hunting and gathering would also be greatly reduced and likely confined to known areas, and deer, elk, bear, seal, sea lion, clam, and mussel populations would likely have boomed (Kay 2002: 248-250). Many heavily tilled swamps and marshes, with a reduction or elimination of regular harvesting activities, would begin to grow trees (willow, ash, crabapple, cedar, cottonwood, etc.), as would scattered meadows, abandoned town sites, inland prairies, and the perimeters of savannahs. If oaks and/or filberts were being managed as plantations (speculative evidence), the creation of new orchards would have probably stopped. Spruce and hemlock would begin foresting coastal headlands, ridges, prairies, and valleys, as Vaughn (1923) described for the Tillamook area in the 1850s; Douglas-fir would begin populating isolated meadows, prairies, berry patches, and the perimeters of bottomland prairies and savannah, as Moravets (1932) describes; true fir would begin populating higher elevation berry patches and the perimeters of balds on the west slope (Aldrich 1973) and seeps and highlands within the Willamette Valley (Zybach 1999); and riparian areas would begin to grow brush and gallery forests in many places. The whole process would take about 20 to 60 years (e.g., Gannett 1902; Weyerhaeuser 1947; Winter et al 2002), and by 1600 or 1650, a large portion of the Coast Range would have been coated with young and thriving second growth stands. These stands would have contained few snags and little “large, woody debris," and would have been interspersed with scattered pockets and relatively small stands of parent seed trees. By 1800, many of these stands would be old-growth around 200 years of age, and by 1950 they would be 350 year-old trees very similar to "ancient" forestlands described in FEMAT (1993), but with a marked absence of charred snags, stumps, logs or other "biological legacy" (e.g., Impara 1997; Franklin et al 2002). Around 1700 and thereafter, large-scale "one careless match" fires, independent of changed human population numbers, would begin to enter the landscape as canopies filled in and tree mortality created fuels. A large-scale mosaic of even-aged forested tracts would begin to form. Reburns would begin to reduce the amount of snags, large woody debris, and other biological legacy in those areas as well, but there would still be more of these materials than in the parent stands, due to increased tree densities that preceded mortality.

Is it possible that the Coast Range was far more populated in the 1400s or 1500s than has been estimated? If so, what evidence exists that might be proof of a higher population? The apparent surplus food stores created by wapato, camas, bracken fern, acorns, tarweed seeds, and other vegetables, as well as coastal marine animals, hunting, and anadromous fish runs, seems to point to the possibility of enough food for a much larger population than has been documented. Certainly, land and housing would have been no problem for larger numbers of people; current populations demonstrate that fact. Firewood for heat, light, and cooking was also abundant. The afforestation and forestation processes that have taken place during historical time as Indian populations and practices declined provide additional supporting evidence, especially if parallels can be made with the widespread establishment of forest trees in the 1500s. It would also help explain the consistent age of Willamette Valley white oak with Douglas-fir, redcedar, and spruce to the west. Too, there would not be the layer of organic material that would mark widespread wildfires, nor would there be evidence of large, older snags, downed old-growth logs, or wind throw-"stirred" soils for the same reasons. Instead, one might reasonably expect to find large tracts of abandoned croplands producing nuts, fruits, bulbs, roots, berries, stalks, and other foods, and archaeological evidence of large, thriving communities near the mouths of streams and rivers. Thousands of acres of abandoned croplands have been located, but otherwise relatively little historical or archaeological evidence has been produced indicating significantly larger populations in the 1500s than were recorded in the late 1700s. Note, however, that little effort has been made to locate such evidence, and it may yet remain to be discovered.

Climate change hypothesis

The climate change hypothesis is that an abrupt and prolonged cooling period, the so-called "Little Ice Age" of ca. 1450 to ca. 1850, created ideal weather conditions for establishing tracts of Sitka spruce, Douglas-fir, Ponderosa Pine, and other long-lived conifer species, throughout western North America (Cromack et al 2002: 180-184; Sessions 2003: 27). The warming trend that signaled the end of the Little Ice Age begins in 1850, coinciding with the first of the Great Fires. Warming and drying patterns continued over the next century, as did catastrophic fires. Current weather conditions, coupled with a possibility of Global Warming, make re-creation of historical forest conditions in regards to species mix, age, and structure, difficult or impossible (Cromack et al 2002: 216-217; Sessions et al 2003: 57). In this hypothesis, Indian burning patterns are secondary to climate and weather regarding fuel history and current planning assumptions.

For North America, Jones and Bradley (1995: 654) note: "No prolonged periods of cool temperatures are evident between 1640 and 1820." For the western US, they rely on Fritts and Shao's (1995) tree ring work to conclude that, from 1602 forward, all of the five western US regions "show little evidence of protracted cool periods with the coldest period occurring during the late 19th and early 20th centuries" (Jones and Bradley 1995: 654-655).

In remarking on climate maps based on 1901-1970 mean values, Fritts and Shao (1995) note: These maps might be regarded as an estimate of the departures of the Little Ice Age climate beginning in 1602 and ending in 1900 from the 1901-1970 mean climate. The reconstructed annual temperature variations in the western United States do not show a Little ice Age cooling, but lower temperatures are clearly evident east of the Rocky Mountains (Fritts and Shao 1995: 277).

Although thousands of trees in the Willamette Valley and Oregon Coast Range -- covering hundreds of thousands of acres -- have had their rings counted, no evidence has been presented that changing climate conditions have affected tree growth patterns or migration. Graumlich (1987) looked specifically for evidence of climate change in her tree ring study, but was only able to document a few years of apparent severe drought, and no long-term trends. In addition, both Graumlich and Fritts and Shao were limited in their interpretations by having access to a limited amount of tree ring data from the Coast Range. The assumption that old-growth trees in southwest Oregon--because of their current species distribution and regeneration problems--were established under "cooler [Little ice Age] conditions," may not apply for the Coast Range to the north. The moderating effects of the Pacific Ocean and the relatively low elevation of coastal mountains have resulted in little or no glaciation of the Coast Range for thousands of years, and further indicates that the climate of the Range was not significantly different during the Little Ice Age than now. Therefore, it is unlikely that climate change is a principal factor in the establishment of old-growth forests in the 16th and 17th century in the Oregon Coast Range or Willamette Valley.

Remarkable coincidences hypothesis

A fourth possibility is that a remarkable series of coincidences occurred throughout the Coast Range in the 15th century. In this scenario insects, diseases, wildfires, droughts, earthquakes, human plagues, tidal waves and/or other events took place, coincidentally resulting in widespread deforestation followed quickly by reforestation of forestlands and afforestation of grasslands. This hypothesis -- a series of interrelated catastrophes of "biblical proportions" -- seems fairly unlikely and has no current proponents. This hypothesis would account for a condition (common age of historical Coast Range old-growth) that has not been widely discussed. This hypothesis, if true, should have caused an identifiable soil marker and left significant "biological legacy" (snags, stumps, logs) from earlier, destroyed stands. The answer to this hypothesis may already exist in the soil profiles, pollen and sediment cores that have been used for other research questions. A series of such events should have left ample evidence--including vivid oral traditions--that can still be sampled. The lack of such evidence does not discount this hypothesis entirely, but does help discount the possibility.

Summary: "weight of the evidence"

Research for this thesis documented widespread forestation in the 16th century that resulted in stands and groves of old-growth Douglas-fir, oak, and Sitka spruce during historical time. Four hypotheses are discussed that might explain this condition: 1) Did a regional-scale catastrophic fire complex destroy most of the Coast Range's forests (followed by reforestation)? 2) Did a decimation of local Indian communities lead to lesser burning practices over a smaller area of the landscape (followed by reforestation of burned forests and afforestation of abandoned grasslands)? 3) Did cooling brought on by the Little Ice Age cause a unique tree seed germination condition that resulted in historical old-growth forests? 4) Did a remarkable series of coincidences, including the possibilities of insects, disease, floods, fire, wind, tidal waves, meteor strikes, or earthquakes, strike western Oregon, resulting in widespread deforestation (followed by reforestation and afforestation)?

Massive amounts of organic matter are grown over almost every acre of western Oregon soil each year. This is because of the climate-moderating effects of the ocean, relatively low elevation, and remarkably large conifer, oak, and alder trees that grow in predictable locations. These plants leave distinct records of their existence across the landscape: trees and other vascular plants leave rings on their stumps, pollens in peat bogs, forest fires deposit charcoal in lake sediments, and dead trees leave snags, stumps, logs, and piles of rotted wood in their wake.

Regional-scale catastrophic fires should have produced an identifiable carbon "marker" in soils and sediments and left significant evidence of past forests above ground. Because this evidence is apparently lacking, such an occurrence seems unlikely. An interconnected mosaic of tree-killing events is also unlikely, both because of statistical improbabilities and the same lack of evidence associated with widespread fire. It is possible that an abrupt cessation of Indian burning resulted in widespread forestation of the Range, but archaeological, anthropological, and historical evidence is also lacking in this regard. It is also possible that a relatively small number of people--say a number consistent with the historical populations of the 1800s--could have systematically kept historical forested areas burned clean, but their motivation for doing so is unknown. Could forest burning have been systematically undertaken during the course of extended inter-tribal or international warfare? As a method of hunting or controlling Grizzly bears? Traditional hunting practices? Any of these explanations are possible, however unlikely. In each instance, though, is the assumption that people could have kept western Oregon largely free of conifer trees if they had wished to do so. Constant, regular fires would not have produced a signature charcoal layer in lake bottoms or soils and would have eventually eliminated any "biological legacy" remaining from earlier, forested conditions. If continuous burning patterns were stopped, whether by change in population, culture, technology, or land ownership, it would have led likely to the growth of even-aged stands of trees throughout the Range, as occurred during historical time. Evidence of forest establishment related to climate change (cooling associated with the Little Ice Age) is also lacking: first, the Little Ice Age seems to have had little, if any, effect on Coast Range climate, and second, Douglas-fir and other native Coast Range trees continue to reproduce, flourish, and grow at rates similar to those measured over the past several centuries (Zybach 1983; Tappenier et al 1997).

Until more research is completed, one can only conjecture as to what may have happened in the 1500s to spawn the vast forested tracts of subsequent centuries. If they were caused by wildfire, the fires were probably caused by people; if they resulted from afforestation, they likely grew from lands previously burned on a regular basis by people. Climate, earthquakes, insects, and diseases may have aided either or both of these processes, but were not likely the principal causes of deforestation or catalysts for forestation. In sum, the widespread establishment of conifer forests throughout the Oregon Coast Range in the 16th century was likely a result of Indian burning practices, including both wildfires and prescribed burns. Whether a significant portion of the forests resulted from a reduction in landscape burning practices, or whether such a reduction may be related to reduced human populations, is unknown.

Select Bibliography

Zybach, Bob, Mack Barrington and Thomas Downey 1995. "Converting Historical Information to GIS: Political Boundaries of the Douglas-Fir Region, 1788 to 1995," Journal of Forestry. Vol. 93, No. 5: 15-20.

Zybach, Bob 1999. Using Oral Histories to Document Changing Forest Cover Patterns: Soap Creek Valley, Oregon, 1500-1999. (PDF_File) MAIS Thesis, Oregon State University, Corvallis, Oregon: 321 pp.

Zybach, Bob 2002. "The Alseya Valley Prairie Complex, ca. 1850: Native Landscapes in Western GLO Surveys," (PDF_File) IN: Changing Landscapes: "Sustaining Traditions." Proceedings of the 5th and 6th Annual Coquille Cultural Preservation Conferences, 2001 and 2002, Don Ivy and R. Scott Byram (eds.), Coquille Indian Tribe, North Bend, Oregon: 161-188.

Zybach, Bob 2003. The Great Fires: Indian Burning and Catastrophic Forest Fire Patterns of the Oregon Coast Range, 1491-1951. (HTML_Defense Draft) PhD Dissertation, OSU, Corvallis, Oregon: 458 pp.

Zybach, Bob 2006. “Forests of the Pacific Northwest: Sustainable Use and Resiliency,” The Consultant. Annual publication of the Associated Certified Foresters of America: 14-18.