Environment, Prehistory & Archaeology of Mount Rainier National Park, Washington
Greg C. Burtchard

Appendix C:
ECOLOGICAL SUCCESSION; IMPLICATIONS FOR PLANT AND ANIMAL ABUNDANCE, AND ARCHAEOLOGICAL SITE DISTRIBUTION PATTERNS

Author's note: The following text is reprinted from Greg C. Burtchard and Robert W. Keeler; 1991; Mt. Hood Cultural Resource Reevaluation Project: A Consideration of Prehistoric and Historic Land Use and Cultural Resource Survey Design Reevaluation, Mt. Hood National Forest, Oregon; report to USDA Forest Service, Gresham, Oregon; Laboratory of Archaeology and Anthropology; Portland State University; Portland, Oregon; pages 40-42. The section reproduced below provides ecological and theoretical background underlying statements regarding seral-stage productivity (phrased as relative forest maturity or ecosystem maturity) and archaeological site distribution patterns discussed in the body of this report. Bracketed [] comments have been added for this printing.

FOLKS HAVE TO EAT: RESOURCE DISTRIBUTION AND PREHISTORIC LAND-USE IN THE NORTHERN OREGON CASCADES

Throughout this chapter [Chapter 2 in Burtchard and Keeler 1991], we have implied that patterned distribution in the availability of resources, principally food resources, is of central importance to understanding patterned site distribution in the mountains. The modern structure of the Northwest Maritime Forest tends to limit food resource abundance overall, placing particular importance on locations within the forest that are less constrained by such limitations. These are places where weather, rainfall, soils and forest clearings combine to allow generation of diverse plant and animal communities. Such communities exist at present in high elevation parklands, weather and fire maintained open forests, and perennially wet meadows. Pollen from both [eastern and western] Cascade slopes suggest that such communities existed, and periodically expanded, during the period of human tenure in the central Cascades. Given the seasonal availability of resources needed to support human populations, it should not be surprising that Forest archaeologists are finding an increasing number of prehistoric localities in the montane uplands. The mountains were simply good places for people to be during the late summer and autumn months when critical exploitable food resources were most abundant. Below, we support this point and clarify basic causes underlying the resource pattern...

The Terrestrial Environment: Forest Maturity, and Plant and Animal Abundance

The availability of terrestrial resources is linked to seral succession and ecosystem maturity. Even though biomass increases during succession, the ratio of primary production to total biomass drops as ecosystems approach maturity. During succession, there is an increase in the proportion of inert or even dead matter with a low respiratory rate, such as wood, shells, and so on (Margalef 1968:31). In a forest, this means that, as maturity increases, the fraction of plant tissue available to support animal life decreases. Accordingly, the highest ratio of animal biomass to plant biomass is not found in the forest proper, but in grasslands or parklands in which vegetation is kept at a lower state of maturity [i.e., an early seral-stage] (Margalef 1968:44). In his discussion of mule deer habitat, Geist (1981:159) emphasizes the point: "Immature ecosystems, compared with climax ones, produce a greater amount of young, exploitable plant tissue per unit area." Because of this variation, deer tend to forage in open areas and/or take advantage of herbaceous growth along streambeds and marshes. He states the same premise even more directly in his discussion of elk ecology. "The greatest concentration of food is found where an animal has access to the entire food-producing (photosynthetic) layer of vegetation. For elk, this is in grasslands" (Geist 1982:227). [45] The point is clear for deer, elk and a variety of animals (including humans) that exploit forest habitats: terrestrial ecosystems with low to moderate maturity provide a higher fraction of edible plant (and animal) tissues than do mature forests.

In the Northwest Maritime Forest, this edible productivity/maturity association poses particular problems for resident human populations. Due to moisture and climate moderating effects of Pacific westerlies, the Maritime Forest naturally is able to achieve high maturity [relatively late-stage seral succession]. In a natural state, old-growth forests would have been common, but would not have been the best places to find food. The very presence of extensive Northwest Maritime Forest cover established a context that selectively favored more intensive, repeated human use of certain low maturity [early seralstage] places within the forested landscape; and less intensive, less frequent use of closed forest, high maturity [late seral-stage] areas. These low maturity places are parklands, meadows, recent burns and any other area where a combination of solar exposure, weather and soils facilitate vigorous low-lying vegetation. These are the places that permit relatively high primary productivity and contain the greatest abundance and diversity of food items. Included within this diversity were arguably the most critical of the upland resources —elk and deer, and perhaps huckleberries and bear. By directing their attention to low maturity areas in the Maritime Forest, prehistoric humans could not only reasonably expect to acquire such high return commodities, but maximize their opportunity to acquire supplemental or buffering resources (game birds, roots and berries) as well. Assuming that food acquisition is a prime reason for using the upland terrain, an understanding of the factors conditioning variable maturity in the northern Oregon Cascades is of key importance to understanding broad-scale patterns in human land-use and patterns in the relative density of their archaeologically preserved remains.

Low maturity areas are not uniformly or randomly distributed in the forest. In a natural state, they are maintained by circumstances that reduce stability of the maritime environment to an extent that represses tree cover but permits growth of a faster reproducing ground cover species. Such places are 1) frequently water saturated ground (wet meadows, swamps and marshes); 2) areas subject to unstable weather conditions [and heavy, late-melting snow loads] (subalpine parklands [and alpine tundra]); 3) solar exposure and/or shallow soils contributing to periodic desiccation (southern and western exposures on high slopes and ridgelines); 4) mesic areas contributing to periodic burning (above plus eastern slope pine forests); 5) tree blowdowns (primarily exposed ridges); and 6) mass sediment wasting (steep slopes). While wet meadows and mass wasting can occur at any elevation, most of the lower maturity areas tend to be situated at higher elevations and perhaps on the pine forested eastern slope. Over long stretches of time, these are places that should have supported the highest density and diversity of plants and animals, and consequently should have been the focus of repeated human hunting and gathering activity. From mid-summer through autumn, upland productivity was at its highest relative to the drier lowlands. Given relative resource abundance in these places at those times, it should not surprise us to find archaeological evidence of human occupation on or near these same upland places. Ridgelines, high elevation parklands, wet meadows were simply among the most productive places for human foragers to earn a living.

It should be noted that natural (non-human related) processes are not the only means by which low maturity states can be achieved and maintained. Humans are quite capable of meddling in such processes. The arguments above suggest that it is unreasonable to expect intelligent, foraging experts not to have recognized and availed themselves of the relative resource abundance of low maturity areas within the generally resource poor Northwest Maritime Forest. It is also unreasonable to expect them not to recognize that they could personally intervene to lower forest maturity in a manner that enhanced its exploitable productivity. Forest burning can maintain or expand grassland and parkland habitats thus improving its elk, deer and ultimately human carrying capacity. Given increasing population demands on available resources through time, we must assume that humans increasingly turned to enhancing resource potential through burning forest cover. The ability of humans to intentionally set fires coupled with the possibility of extensive (if infrequent) natural fires introduces a degree of chaos into the emerging pattern of low maturity and land-use in the Maritime Forest. Even so, it is reasonable to expect intentional burning to be differentially directed to 1) those areas that were already productive habitats (rather than attempting to create new habitat out of mature forest, and 2) to drier areas that could be burned most effectively. If so, the basic low maturity pattern noted above should generally hold as outlined. The most dramatic effect of human induced burning should have been to enlarge the naturally occurring boundaries.

In short, because exploitable resources have a patterned distribution in the northern Oregon Cascades [and in the Cascades generally], the archaeological remains of humans dependent upon those resources should be [spatially] patterned as well. An understanding of the impact of forest maturity on resource productivity provides an important element in understanding basic [site location] patterns in human use of the environment. Arguing solely from a maturity based perspective, we anticipate a relatively high density of prehistoric archaeological sites near 1) presently predictable places such as wet meadows, and on upper elevation ridges and [subalpine] parklands; and 2) functionally similar, but less predictable, places such as once dry meadows, ephemeral burns and artificially maintained lowmaturity areas that are now obscured by regenerated successional forest cover. ...

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