Chapter 6

Archaeobotanical Remains

by Karen R. Adams, Kristin A. Kuckelman, and Vandy E. Bowyer

Introduction

The rich and diverse botanical assemblage from Sand Canyon Pueblo (Site 5MT765) provides an excellent data set with which to assess the role of plant resources in the subsistence economy of Pueblo Indians just before the depopulation of the Mesa Verde region in the late A.D. 1200s. In this chapter, we present the results of analyses of the ancient plant remains in flotation and macrofossil samples collected from this site; as appropriate, we also use the results of previous analyses of Sand Canyon archaeobotanical remains (Adams 1989*3, 1989*5; Bowyer 1995*1; Gish 1988*2, 1990*1; Scott and Aasen 1985*1). Our goal was to detect and interpret patterns of food, fuel, and construction-material use by the inhabitants of Sand Canyon Pueblo.

This chapter begins with a brief summary of the environmental setting of Sand Canyon Pueblo, which is followed by a description of the methods used to process and analyze the flotation and macrofossil samples collected from the site. Analytic results are then reported, including a review of construction wood, fuels, plant foods, seed caches, and intentionally modified plant materials from the village. These sections are followed by a discussion of the paleoenvironment and subsistence, including resource depletion and changes in subsistence strategies near the end of village occupation. This document was prepared between 1995 and 2004. All data used in this chapter were current as of September 2004.

Environmental Setting

Vegetation in the vicinity of Sand Canyon Pueblo represents two major biotic communities, the Great Basin Desertscrub (Turner 1982*1) and the Great Basin Conifer Woodland (Brown 1982*1). Vegetation in the vicinity of Sand Canyon is characterized by pinyon pine (Pinus edulis) and Utah juniper (Juniperus osteosperma), interspersed with shrubs such as big sagebrush (Artemisia tridentata). The understory comprises numerous herbaceous plants, including grasses (Gramineae), mustards (Cruciferae), and mallows (Malvaceae). Some plants, such as reeds (Phragmites), cottonwoods (Populus), and willows (Salix), prefer the moister soils in the area, whereas members of the cactus family, such as prickly pear (Opuntia), are found in the dry locations. For a more complete list of plants in the Sand Canyon locality, see Lightfoot et al. (1993*1:6).

Farming was an integral part of the subsistence system of the Sand Canyon Pueblo inhabitants and included dry-land farming and run-off irrigation agriculture. Soil type, precipitation, length of growing season, and surface topography all played critical roles in the success of ancient farming in the Mesa Verde region. The following paragraph provides a brief overview of some of these factors. More-comprehensive discussions of environmental factors that would have affected the crop yields of the farmers of Sand Canyon Pueblo can be found in Dean and Van West (2002*1), Lightfoot et al. (1993*1), Van West and Dean (2000*1), and Van West and Lipe (1992*1).

The upland soils in the area are eolian silts categorized as Mesa Verde loess and Sage Plain loess (Arrhenius and Bonatti 1965*1). Today, as in the ancient past, these arable soils are farmed (Lightfoot et al. 1993*1). Much of the precipitation in the region occurs in the form of winter snow and summer monsoon rains (Lightfoot et al. 1993*1). An adequate quantity of snow is particularly important for dry-land farming because snow provides the soil moisture needed for seed germination in the spring as well as the deep soil moisture required to sustain growth during drier months (Erdman et al. 1969*1:19). Corn Growing Degree Days (CGDD), a measure of the accumulation of heat over the course of the growing season, and annual precipitation are important factors that determine the best locations in the Mesa Verde region for growing maize. CGDD is computed for each day as the difference between the mean daily temperature (maximum minus minimum, divided by 2) and 50° Fahrenheit, or the minimum temperature necessary for maize to mature (Adams and Petersen 1999*1:23–24). Surface topography (slope and aspect) and edaphic factors, such as soil depth, also affect the agricultural productivity of land (Lightfoot et al. 1993*1). Studies of ancient climate and agriculture in southwestern Colorado have shown that, within the Sand Canyon locality, agricultural productivity would have varied considerably between locations and from year to year (Dean and Van West 2002*1; Van West and Dean 2000*1).

Methods

Three types of vegetal samples were collected from Sand Canyon Pueblo: macrofossil, flotation, and pollen. Hundreds of samples were collected, many were processed, and a subset of those processed was analyzed (Table 1). Macrofossil samples are larger vegetal items handpicked by archaeologists during excavation. The results of analysis of 283 macrofossil samples compose a large data set; however, these data are incorporated into this chapter only when they provide insights that cannot be gleaned from the flotation data set. Flotation samples are bulk samples that were collected from primary refuse in thermal features (hearths, burned spots, and firepits), from secondary refuse (middens), and from a variety of other contexts that appeared likely to contain culturally interpretable vegetal remains (Table 2). Flotation collection is guided by a systematic sampling strategy, and thus the results lend themselves more readily to the detection of intrasite use patterns. Numerous pollen samples were collected from specific types of protected locations, usually on structure floors. However, because pollen samples from so few contexts were analyzed (Gish 1988*2, 1990*1; Scott and Aasen 1985*1), the results of pollen analyses are used minimally in this chapter.

Flotation and Macrofossil Samples

Additional information regarding the nomenclature, the sample types, and the general procedures used in the collection, processing, and analysis of flotation and macrofossil samples collected by Crow Canyon archaeologists is presented in Crow Canyon's online publications titled The Crow Canyon Archaeological Center Laboratory Manual (Ortman et al. 2005*1) and Archaeobotanical Analysis: Principles and Methods (Adams 2004*1). However, specific reports should be consulted for procedures used by various analysts (Table 1). The preprocessing volumes of the flotation samples analyzed by Adams and Bowyer ranged from 0.25 liter to 1.00 liter; the volumes of the other flotation samples from Sand Canyon Pueblo that were processed cannot be stated with certainty.

Two different methods were used to process the Sand Canyon Pueblo flotation samples. Flotation samples collected before 1991 were processed by methods outlined by Adams (1993*1). Samples collected after 1991 were processed using a technique outlined by Schaff (1981*1). Of those samples that contained more than 1.0 liter of material, only 1.0 liter of material was floated; the remaining material was curated. Some sampled contexts contained less than 1.0 liter of fill. The samples from these contexts were floated in their entirety.

Of the 80 flotation samples analyzed by Adams and Bowyer, the residua from only 25 samples were completely analyzed. The residua from the remaining samples were subsampled in a manner aimed at locating the broadest diversity of taxa within each sample. Subsampling was used primarily when the quantity of floated residue of a sample was too great for analysts to sort completely. See Archaeobotanical Analysis: Principles and Methods for a description of the subsampling and analytic procedures used.

Several references were consulted for anatomical descriptions of genera (Cutler and Whitaker 1961*1; Martin and Barkley 1961*1; Welsh et al. 1987*1). In addition, modern comparative material at the environmental archaeology laboratory at the Crow Canyon Archaeological Center aided in the identification of taxa.

Interpretive Framework

The analyzed flotation samples from Sand Canyon Pueblo were collected from primary refuse in thermal features, secondary refuse, de facto refuse, and a variety of other types of fill (Table 2). Primary refuse is defined as cultural materials discarded at their location of use; secondary refuse consists of materials discarded elsewhere (Schiffer 1972*1, 1987*1:18, 58). Primary refuse in thermal features is therefore associated with the last uses of the feature, whereas most deposits of secondary refuse accumulate over a longer period of time and result from a broader range of activities. De facto refuse is defined as cultural materials that were left behind but are still usable (Schiffer 1972*1, 1987*1:89). The three types of thermal features found and sampled at Sand Canyon Pueblo—hearths, firepits, and burned spots—are defined in Crow Canyon's online field manual.

The composition of the plant assemblage from a site—in particular, the relative abundance of domesticated plants, weedy species, and various fuelwoods—has the potential to shed light on past local ecologies and patterns of land use. Domesticates would have been grown in agricultural fields or small garden plots; weedy plants also thrive in such locations, as well as in other naturally or humanly disturbed areas. Some trees and shrubs that are useful as fuelwood, on the other hand, are common in relatively undisturbed woodland and riparian habitats. The degree of reliance on domesticates, weedy species, and various fuelwoods—as reflected in the plant assemblage—therefore provides some measure of the extent of disturbance in the local area during the occupation of the site.

To aid in the interpretation of data, calculations of ubiquity and diversity are used throughout this chapter (see also Archaeobotanical Analysis: Principles and Methods, paragraphs 27–28). Ubiquity is the number and percentage of samples within a particular sample-type category (e.g., primary thermal features) in which a given taxon/plant part was identified. Diversity is calculated by summing the number of taxa represented within a sample-type category and dividing that number by the total number of taxa represented in all sample-type categories being compared. For the purposes of calculating taxonomic diversity, all parts of the same genus are conservatively considered to represent one taxon when they occur in the same subset of samples; for example, in the case of fuelwoods, Pinus-type bark scale, Pinus-type wood, and Pinus edulis–type cone scale have been counted as a single taxon. "Unknowns" are conservatively counted once, regardless of how many parts are recovered or how many times they occur in a sample.

Two publications pertaining to Sand Canyon Pueblo and other sites investigated by the Crow Canyon Archaeological Center support the interpretations provided here. The first is a compendium that reports historical uses of plants by native peoples in the American Southwest (Rainey and Adams 2004*1). This compendium provides a thorough examination of relevant ethnographic literature conducted to accumulate information on the range of uses for all plants and plant parts recovered from sites excavated by Crow Canyon. A second document presents identification criteria (Adams and Murray 2004*1) for the plant parts recovered. This document includes metric and nonmetric observations on all the archaeobotanical wood and nonwood plant parts that have preserved. Scientific terminology used in these documents and in this chapter conforms to A Utah Flora (Welsh et al. 1987*1) whenever possible.

Results

In the flotation and macrofossil samples from Sand Canyon Pueblo that were analyzed by Adams and Bowyer, a variety of plant parts representing at least 45 taxa of domesticates, trees, shrubs, annuals, and perennials were preserved (Table 3 and Table 4). Many plant parts found in flotation and macrofossil samples were charred and are assumed to have become so as a result of human activity during the occupation of the village; however, numerous uncharred specimens were also associated with the occupation. Many of the uncharred specimens were from the lower fill of a two-story structure, Room 1217/1205 (Database Map 4159, Database Map 4165, and Database Map 4001) that contained well-preserved, unburned roofing debris (Database Photo 3167) and other vegetal artifacts (Appendix A), and these specimens are thus assumed to have entered this room as the result of human actions. We also infer that, because of their contexts, various other uncharred items are cultural in origin. Uncharred specimens that appeared to be modern are excluded from the following discussions.

Construction Wood

Most samples of construction wood that were collected from the site were submitted for tree-ring dating. Of the 1,012 tree-ring samples collected, 936, or 92 percent, were identified as juniper (Juniperus). Forty-seven (5 percent) of the dated samples are pinyon (Pinus edulis), 11 samples were identified as spruce/fir, nine are ponderosa pine (Pinus ponderosa), three are Douglas fir (Pseudotsuga menziesii), five are of unspecified, nonconiferous taxa, and one sample is oak (Quercus). Some of these samples, particularly the pinyon pine, were recovered from primary or secondary refuse and thus might have been fuelwood rather than construction material.

Wood was also found in macrofossil and flotation samples collected from collapsed roofing material. The most frequently represented taxon in these samples is juniper, followed by—in order of decreasing frequency—big sagebrush (Artemisia tridentata), cliff-rose/bitterbrush (Purshia), pinyon pine (Pinus edulis), rabbitbrush (Chrysothamnus), and mountain mahogany (Cercocarpus). Very small amounts of chokecherry/rose (Prunus/Rosa), maple (Acer, probably locally available Acer negundo), saltbush (Atriplex), wolfberry (Lycium), and ephedra were also found. It is possible that wood of the more sparsely represented taxa originated on top of structure roofs and was associated with rooftop activities, entering roof-fall strata incidentally.

The abundance of juniper wood in the tree-ring and macrofossil specimens collected from Sand Canyon Pueblo indicate that juniper was the construction wood of choice, although timbers of other taxa were used occasionally. Wood from shrubby taxa was probably used as "closing" material, that is, to form a continuous, brushy layer on top of roofing timbers before the uppermost, sediment layer was added.

Fuel

The identification of wood charcoal and other charred, nonreproductive vegetative parts in flotation samples from Sand Canyon Pueblo reveals that numerous woody and shrubby taxa were used by the villagers (Table 5 and Table 6). These resources were clearly used for many different purposes in the village, such as in construction, as discussed above, and might have become charred in any one of several ways. However, most charred wood and charred nonreproductive vegetal parts in the flotation samples collected from primary and secondary refuse probably represent use of these resources as fuel.

Juniper (Juniperus) appears to have been by far the most frequently used fuel at the site. The ubiquity of charred juniper wood and the presence of charred juniper twigs, scale leaves, and bark in thermal features at the site provides evidence that this conifer grew in the vicinity of the pueblo and was routinely brought back to the site to be used as fuel. The presence of pine (Pinus) wood and bark scales in nearly one-half of the samples analyzed indicates that this taxon was also regularly used as fuel; pine bark is known to be good tinder.

The presence of charred maize (Zea mays) cupules and cobs in numerous thermal features and in material suspected of having been cleaned out of hearths suggests use of cobs as tinder or fuel after the kernels were removed. Cupules (pockets that each hold two kernels) are the most durable parts of the cob and remain firmly attached to the cob when the kernels are removed; they often remain after burning. Maize cobs are also known to have been eaten in times of famine (see Plant Use by Native Peoples of the American Southwest: Ethnographic Documentation).

Several shrubby taxa were also used as fuel at Sand Canyon Pueblo, although these taxa are much less ubiquitous in flotation samples than are the woody taxa. Mountain mahogany (Cercocarpus), chokecherry/rose (Prunus/Rosa), big sagebrush (Artemisia tridentata), and serviceberry/peraphyllum (Amelanchier/Peraphyllum) were the top-ranking shrubby taxa present in samples from thermal features. Wolfberry (Lycium), hackberry (Celtis), and rose (Rosaceae), which were recovered only in macrofossil samples (Table 3), add to the diversity of shrubby taxa used as fuel in the village. It is possible that certain woods were preferred fuels in specific types of structures, such as kivas, or in particular types of thermal features. For example, mountain mahogany (Cercocarpus) was not identified in samples collected from burned spots, and chokecherry/rose (Prunus/Rosa), which is well represented at the site level, was not found in flotation samples from hearths (Table 6). However, among shrubby wood, no other indications of possible fuel preference could be detected in the Sand Canyon assemblage.

Foods

Domesticates and Wild Resources

The inhabitants of Sand Canyon Pueblo exploited a large suite of plants for food, including both domesticated and wild resources. Table 7 presents the ubiquity and diversity of reproductive parts in flotation samples from the different contexts sampled at the site. Maize (Zea mays) kernels were the most ubiquitous of the domesticates in the primary and secondary refuse samples. Reproductive parts from squash (Cucurbita) and common beans (Phaseolus vulgaris) were present in only a few samples. The low ubiquity of these domesticates in the archaeological record probably indicates that they formed a less substantial portion of the subsistence base than did maize. However, these items generally tend to preserve poorly in the archaeological record (Hunter 1997*1:233), and it is therefore difficult to determine precisely what portions of the subsistence base these domesticates composed. Studies of the contents of ancestral Pueblo coprolites from this region (e.g., Minnis 1989*1; Stiger 1979*1) indicate that squash and beans were consumed more frequently than is indicated by the flotation data from Sand Canyon Pueblo.

Reproductive parts from numerous wild plants were also found in many flotation samples from Sand Canyon Pueblo (Table 7). In fact, cheno-am seeds (from plants in either the chenopod [goosefoot] or amaranth [pigweed] families) were even more ubiquitous than maize kernels in all three categories of contexts. Groundcherry (Physalis), prickly pear (Opuntia), and purslane (Portulaca retusa) were also fairly ubiquitous. In addition, several other wild-plant taxa were identified in the flotation samples from this site—bulrush (Scirpus), common sunflower (Helianthus annuus), Indian ricegrass (Stipa hymenoides), and grasses (Gramineae)—and thus apparently were consumed or used occasionally. A few seeds from winged pigweed (Cycloloma atriplicifolium) and woolly wheat (Plantago) were also found in the Sand Canyon flotation samples; these taxa are rarely represented in archaeological assemblages from the Sand Canyon locality or elsewhere in the Mesa Verde region.

Foods in Secondary Refuse

The plant remains found in secondary refuse accumulated over the decades-long occupation of the village and thus form a more comprehensive record of plant use than do the remains from primary refuse (Table 7). Not surprisingly, many of the same taxa are represented in both types of contexts; however, unlike the plant remains found in primary refuse from thermal features, samples from secondary refuse also contain reproductive parts of sunflower (Helianthus), Indian ricegrass (Stipa hymenoides), grass (Graminae), common bean (Phaseolus vulgaris), and pea (Leguminosae). Therefore, these taxa might have been exploited more heavily during the occupation of the village than they were near the end of village occupation.

Foods in Primary Refuse

The primary refuse in the thermal features at Sand Canyon Pueblo contains the remains of some of the last foods prepared in those features (Table 7, Table 8, and Table 9), although some of these features were abandoned well before village depopulation. The most ubiquitous plant taxa and reproductive parts in primary refuse are cheno-am seeds, followed by groundcherry (Physalis) seeds, prickly pear (Opuntia) seeds, maize (Zea mays) kernels, and purslane (Portulaca) seeds.

A comparison of plant materials found in the three types of thermal features at Sand Canyon reveals some differences in the composition of the plant assemblages from each (Table 8). Of the 39 samples of primary refuse from thermal features, those from burned spots contained the greatest diversity of taxa, followed by those from firepits. Samples from hearths contained the least diversity of taxa. Cheno-am and groundcherry (Physalis) seeds are well represented in samples from burned spots and firepits. These taxa are less ubiquitous in hearths; furthermore, purslane (Portulaca) seeds and maize (Zea mays) kernels are conspicuously absent from the hearth samples. More samples were examined from hearths (N = 19) than from burned spots (N = 8) or firepits (N = 12), so it is unlikely that this disparity is the result of sampling.

Maize at Sand Canyon Pueblo

The following discussion summarizes the results of two analyses carried out on the maize (Zea mays) parts present in the macrofossil and flotation samples from Sand Canyon Pueblo (Adams 1989*3; Bowyer 1995*1). Standard measurements were taken on cobs, cob segments, kernels, and shank segments. Although the majority of the specimens are charred, a few uncharred cob fragments and cupules were found in an exceptionally well preserved structure, Room 1205 (Database Map 4159 and Database Map 4165).

Maize Cobs and Cob Segments

Only one complete maize cob was recovered at the site. Cob segments were collected from a variety of contexts, including secondary refuse and other types of fill from rooms, kivas (including the great kiva), the D-shaped building (Architectural Block 1500), and extramural locations. A cob "segment" is a fragment that has a complete circumference for at least a portion of the cob. In all, the complete cob and 445 cob segments were measured for length, cob rachis diameter (as defined by Wellhausen et al. [1952*1]), and cupule width (as defined by Nickerson [1953*1]), when possible. The cob and all cob segments lacked kernels. The complete charred cob and many charred cob segments were recovered from Midden 1214 (Database Map 4179 and Database Map 4159). Ten uncharred segments were recovered from refuse in Room 1205 (Database Map 4159 and Database Map 4165).

The characteristics of the cob segments vary considerably. Most segments taper gradually from the base to the apex, although a few are cigar shaped (tapered at both top and apex). The number of rows on cobs ranges from eight to 16, although the majority of cobs have eight, 10, or 12 (number of specimens for which rows could be counted = 441). The mean number of rows is 9.7, and the median is 10 rows. Cob segments and cob fragments (portions of cobs not complete around the circumference) range in length from 0.5 to 8.0 cm, with a mean of 2.6 cm (number of specimens for which length was measured = 442). Sixty percent of the cobs are round in cross section, but many are elliptical. Rachis diameters of round cobs range from 2 to 8 mm, with an average of 4 mm. In the assemblage of elliptical cobs, the shortest axis is 2 mm, whereas the longest is 8 mm. Cupules range from 2 to 8 mm in width; the mean width is 5 mm (number of specimens on which cupules could be measured = 442). The small dimensions are probably due in large part to burning, which is known to significantly shrink cobs (Brugge 1965*1; Stewart and Robertson 1971*1).

Maize Kernels

In the excavated areas at Sand Canyon Pueblo, maize kernels were not as abundant as cob segments and cupules. Kernels are fragile and break easily when subjected to archaeological processing. Their sparse representation at the site might be, in part, the result of poor preservation but might also reflect great care taken by occupants of the village to not waste kernels. Only 20 maize kernels, all of which were charred, were complete enough for measurement (Table 10). Several kernels appear to have the dense, fine-grained endosperm characteristic of flint types of maize, i.e., composed primarily of hard starch endosperm and relatively little soft starch (flour) endosperm. However, it is likely that both types were being grown by Sand Canyon Pueblo farmers.

Maize Shanks

A maize shank is the stem below the ear that attaches the ear to the plant. Thirty-eight shanks and 44 shank segments were recovered at Sand Canyon Pueblo—most were from Midden 1214. Although relatively short, ranging from 7 to 35 mm in length, most shanks contained more than one node (a node is the place where individual husks were formerly attached). On cobs and cob segments on which the butt of the ear was attached to the shank, the shank is only slightly smaller than the base of the ear. The presence of shanks in Sand Canyon Pueblo deposits suggests that agricultural fields were near enough that secondary waste products were occasionally carried into the village.

Maize Type

It is difficult to determine which varieties of ancient maize are present in the Sand Canyon Pueblo assemblage. Numerous traits of maize ears, cobs, and kernels have been shown to be affected by the environment (Adams et al. 1999*1) and by charring (Goette et al. 1994*1). Shorter cob length results from reduced moisture (Adams et al. 1999*1) and from burning (Brugge 1965*1; Stewart and Robertson 1971*1). Rachis segment length is affected by the amount and timing of moisture available to a maize plant during development, and rachis diameter may be as well. Maize kernel dimensions, especially length and width, are affected by access to water during growth (Adams et al. 1999*1), and kernel thickness is increased by charring (Goette et al. 1994*1). Cupule width is moderately responsive to moisture (Adams et al. 1999*1); cupules tend to shrink when charred (Goette et al. 1994*1). One of the most stable traits is the number of kernel rows, which is relatively unaffected by moisture (Adams et al. 1999*1) and not affected by burning. In addition, the lack of complete descriptions of Native American varieties of maize grown in the United States prevents any evaluation of the overlap of traits among the types, giving us no comparative basis for clearly recognizing ancient races.

The traits of the Sand Canyon maize are, however, generally within the range of variability of Pima/Papago/Basketmaker/Hohokam varieties (Adams 1994*1:296) and of ancient maize previously reported from southwestern Colorado (Adams 1994*1:291). The maize from Sand Canyon Pueblo also bears similarities to that from the Duckfoot site, a late Pueblo I hamlet excavated by Crow Canyon (see Adams 1993*1:197–199).

Seed Caches

Three seed caches were identified in the Sand Canyon Pueblo plant assemblage. Two of the caches appear to have been created by rodents. The third seed cache is inferred to be the result of human activity.

Rodent Seed Caches

Rodent seed caches were identified in two structures: Kiva 1004 and Tower 1008 (Table 11; also see Database Map 4121). One macrofossil and one flotation sample were collected from a rodent cache in the collapsed roofing debris in a corner bin located on the surface of the southern recess in Kiva 1004 (see Point Location 4 in Feature 15 on Database Map 4132). A rodent likely cached the seeds in the roofing timbers after the kiva was abandoned but before the roof was burned. Its identification as a rodent cache was based on the diversity of plant material, the abundance of fecal pellets, and the systematic degradation (dull, uniform, shovel-shaped marks suggestive of rodent gnawing) on some of the reproductive plant material. The taxa represented in this cache (Table 11) are also present in samples from cultural contexts across the site; the contents of the cache were probably gleaned from human food stores and refuse, as well as from materials in the natural environment.

The rodent cache in Tower 1008 (see Point Location 28 on Database Map 4147) consists of a concentration of bitterbrush (Purshia) seeds that was collected as a macrofossil sample (Table 11). Although this cache does not include plant debris or fecal pellets, the seeds contained within it exhibit systematic degradation similar to that observed in the cache from Kiva 1004. Gnaw marks are present in the center of each seed, and the distal and proximal seed ends have been split into two pieces. It is probable that rodents were extracting the embryo portion of the seeds.

Human Seed Cache

One seed cache was collected as a macrofossil sample from Nonstructure 1218, the scattered, burned roofing debris that was found near the top of the upper lining wall of Kiva 1206 (see Database Map 4159). This cache (Point Location 9 on Database Map 4183) is probably the result of human behavior, rather than of rodent activity, because there are no rodent fecal remains and there is no evidence of nesting material. Also, there is no systematic degradation; many of the seeds are complete. The contents of this cache are charred and include thousands of bitterbrush (Purshia tridentata) seeds and seeds that resemble mustard (Cruciferae) seeds, along with hundreds of penstemon (Penstemon) seeds. It is possible that these seeds were food stores or ceremonial or ritual offerings.

Intentionally Modified Plant Materials

Intentionally modified plant materials from Sand Canyon Pueblo are fully reported in Appendix A. Most of the items were found in Midden 1214 (Database Map 4179 and Database Map 4159) and Room 1205 (Database Map 4166). The modified plant specimens from Midden 1214 are charred; either they were discarded in charred condition or they burned after being discarded. A variety of uncharred modified plant materials were found in Room 1205, a lower-story room that was exceptionally well preserved. The materials preserved on the floor of this room could have been either stored items or refuse dumped through the hatchway in the southeast corner of the roof (Database Map 4166). Modified plant materials were also preserved in numerous other locations at the site; most of these items are charred (Appendix A).

The modified plant materials from this site include worked or split sticks, wooden slabs or slats, possible bow fragments, fiber cordage, twilled sandal fragments, fragments of a willow mat, coiled basketry fragments, a basketry plaque, cigarettes fashioned from reedgrass (Phragmites australis), and a vessel fashioned from a domesticated gourd (Lagenaria siceraria). The taxon Lagenaria siceraria is represented by few remains in the archaeobotanical record from Sand Canyon Pueblo; therefore, it is probable that this domesticate was not grown by the residents but was instead obtained through trade or by some other means.

Discussion

Paleoenvironment

The archaeobotanical record indicates that the inhabitants of Sand Canyon Pueblo exploited plants in a variety of habitats, including pinyon-juniper woodland and well-established sagebrush parklands, along with anthropogenically created habitats such as agricultural fields. The villagers obtained construction wood and fuel from the surrounding pinyon-juniper woodland. The woods of several additional trees and shrubs were also exploited by the residents: Cercocarpus, Prunus/Rosa, Amelanchier/Peraphyllum, Ephedra, and Purshia grow in stable habitats; Artemisia tridentata, Atriplex, and Chrysothamnus grow in formerly disturbed habitats; and Populus/Salix and Fraxinus grow in riparian habitats. All these trees and shrubs are assumed to have been growing in the area around Sand Canyon Pueblo.

Juniper was the construction timber of choice at Sand Canyon Pueblo, although a small number of pinyon pine, Douglas fir, and ponderosa pine beams were also used (see "Tree-Ring Dating Results" in The Sand Canyon Pueblo Database). In a study of the supply and use of construction timbers, Hovezak (1992*1) concluded that, when supplemented with timbers reused from nearby farmsteads, the number of juniper trees growing in the vicinity of the village should have been adequate for constructing the buildings in Sand Canyon Pueblo. The villagers might have obtained the ponderosa pine and Douglas fir beams from upland areas such as Ute Mountain, or they might have salvaged these timbers from earlier habitations in the community.

Native habitats would have been disturbed by clearing for agricultural fields and smaller gardens, building construction, long-term village occupation, and fuel collection. The relative proportions of weedy and nonweedy species in a plant assemblage can reflect the general level of environmental disturbance in an ancient community (Table 12) and the proximity of agricultural fields to the village. Three of the most ubiquitous food taxa represented at Sand Canyon Pueblo—cheno-ams, groundcherry (Physalis longifolia), and purslane (Portulaca retusa)—grow in disturbed habitats and agricultural fields. Also ubiquitous is prickly pear (Opuntia), which, although a perennial, can represent a somewhat disturbed habitat (Minnis 1989*1:543). The ubiquity of these disturbance species indicates that fields were probably located near the village. The presence of maize (Zea mays) cobs and shanks at the site also indicates that agricultural fields were nearby—it is unlikely that maize plant debris would have been transported long distances. In sum, the evidence suggests that the environment around Sand Canyon Pueblo was at least moderately disturbed during the occupation of the village and that agricultural fields were located nearby.

Subsistence at Sand Canyon Pueblo

The patterns of plant use as reflected in the overall assemblage of plant remains from Sand Canyon Pueblo are generally similar to those documented for other ancestral Pueblo sites in the region, and the archaeobotanical data reported are roughly consistent with data from other sites in the Sand Canyon locality (Adams 1999*3). In the following sections, we present interpretations about the plant remains found at Sand Canyon Pueblo. We discuss plants used for food and for fuel, and we examine the distributions and functions of thermal features across the site. The plant remains are also examined for possible insights into the uses of both kivas and public architecture.

Plant Foods

The plant remains found in middens and other preabandonment contexts at Sand Canyon Pueblo indicate that villagers grew domesticated crops and exploited numerous wild foods. Maize (Zea mays), common beans (Phaseolus vulgaris), two species of squash (Cucurbita moschata and C. pepo), and gourd (Lagenaria siceraria) are the domesticated plants present in the plant assemblage. Many wild plants were also gathered. The presence of the reproductive parts of maize (Zea mays), cheno-ams, and groundcherry (Physalis) in many contexts and in a variety of settings across the site suggests that these three resources were consumed regularly by numerous households and probably composed a substantial portion of the diet during most of the occupation of the pueblo. Cheno-ams and groundcherry are also the two most ubiquitous wild plant foods in the archaeobotanical record for Woods Canyon Pueblo (Rainey and Jezik 2002*1) and Yellow Jacket Pueblo (Murray and Jackman-Craig 2003*1), two other late villages in the general vicinity of Sand Canyon Pueblo.

Several lines of evidence indicate the dominance of maize (Zea mays) in the subsistence of the ancestral Pueblo people. The dietary importance of maize in the Mesa Verde region during Pueblo III times is demonstrated by several isotopic studies on bone and coprolites (Decker and Tieszen 1989*1; Minnis 1989*1; Scott 1979*1; Stiger 1979*1). Bone-chemistry analyses on the skeletal remains of 20 individuals from Sand Canyon Pueblo (Katzenberg 1995*1) indicate that the diets of the tested individuals were heavily reliant on maize. In an isotopic study of 35 individuals in burial populations dating from about A.D. 470 (Basketmaker III) to A.D. 1250 (Pueblo III) at Mesa Verde National Park and the Ute Mountain Ute Tribal Park, Decker and Tieszen (1989*1) found that maize constituted as much as 80 percent of the total diet. One study of human coprolites from Pueblo III sites in the Mesa Verde region and the larger Four Corners area indicates that maize composed 96 percent of the food materials in fecal remains (Stiger 1979*1). Although maize may be overrepresented in feces because of its tough pericarp, this bias is offset by the fact that various techniques used to prepare maize for consumption (for example, grinding and parching) would not be conducive to the preservation of macroplant remains in coprolites (Minnis 1989*1). It is thus likely that the subsistence base of the villagers at Sand Canyon Pueblo was heavily maize dependent.

It is possible that the residents of the village encouraged the growth and proliferation of some economically important wild plants. Edible weedy plants such as cheno-ams, groundcherry, and purslane were probably allowed to grow in and around cultivated areas, and some plants might have been allowed to reseed themselves. Weeding, tending, and collecting might have also encouraged plant growth. Burning, which promotes the growth of certain annual herbs, is another way that plants might have been encouraged. The ubiquity of weedy taxa might reflect considerable reliance on crops and agricultural by-products.

It should be noted that some wild plants in the Southwest (e.g., some species of Amaranthus and Portulaca, Atriplex canescens, and members of the grass family) have metabolic similarities to maize and thus yield similar isotopic ratios. Some of these wild plants and others, including Opuntia, Echinocereus, and Yucca, may be contributing to the bone isotopic analysis results. Isotopic analyses of materials from sites in the Southwest are much harder to interpret because of these overlapping signatures.

Fuels

Wood from juniper and pine trees was the main fuel used at the pueblo (Table 5 and Table 13), although maize cobs were also used regularly. These three resources were also the fuels used most widely in the region during the century before depopulation (Adams and Bowyer 2002*2). Used less often at Sand Canyon was the wood of shrubby taxa such as chokecherry/rose (Prunus/Rosa), serviceberry/peraphyllum (Amelanchier/Peraphyllum), mountain mahogany (Cercocarpus), and big sagebrush (Artemisia tridentata).

When the remains of fuels at Sand Canyon are grouped by study unit type, it is evident that samples from thermal features in rooms contained the greatest diversity of taxa, even though fewer flotation samples were analyzed from these contexts than from kivas (Table 13). The fuel taxa represented in thermal features in kivas are also quite diverse. The lower diversity in features in towers and extramural areas might be a result of sampling. It is not possible from the available data to detect meaningful patterns of fuel use by study unit type.

Use of Thermal Features

In searching for significant patterns of plant distribution in samples collected from thermal features (Table 13), it is important to consider the different characteristics of these features. The evidence indicates that, during most of the occupation of the village, nearly all cooking was done over hearths, all but one of which are located inside kivas. Cooking would have been a daily occurrence in each kiva suite, and the hearth is the only type of thermal feature that is present in every kiva suite. All the hearths at Sand Canyon Pueblo are deep, formally constructed features that were subjected to repeated use. Firepits are, by definition, expedient features used only briefly. Unlike hearths, these expedient features are very unevenly distributed across the site. There are 12 such features in Kiva Suite 1004, but none in suites 1206, 306, or 208, for example; most are located in rooms. Burned spots reflect a single burn event, and most are found on room floors or in fills just above floors; in addition, several were found on ephemeral use surfaces just outside the village-enclosing wall.

Thus, the three types of thermal features at Sand Canyon Pueblo can be characterized as follows. Hearths were the primary cooking features and also would have provided warmth and lighting in the kivas. The abundance and spatial distribution of hearths suggests that food processing, such as parching and boiling, was also associated with these features, especially during the winter months when many activities took place indoors. Firepits might have been used similarly, but would not have been used as extensively. The characteristics of burned spots suggest that they were campfires, many of which were used near the time of village depopulation. However, the dating of several burned spots on extramural surfaces outside the village-enclosing wall is unclear. The presence of reproductive plant parts in the residue from burned spots indicates that at least some of these features were used for cooking.

Plant Evidence for Kiva Use

The use of ancient kivas has been debated in the archaeological literature of the Southwest. Some researchers (Cater and Chenault 1988*1; Lekson 1988*1, 1989*1; Lipe 1989*1; Varien and Lightfoot 1989*1) have suggested that precontact kivas (i.e., kivas dating from before Spanish contact) were used primarily for domestic purposes, whereas others (Fewkes 1911*1:48; Powell 1875*1:68; Simpson 1964*1:37) have assumed that, like their historic counterparts, ancient kivas were used primarily for ceremonies and rituals and as men's meeting houses. The plant record from Sand Canyon Pueblo offers insights into activities that might have occurred in kivas during Pueblo III times in the Mesa Verde region.

Plant remains in flotation samples collected from kivas at Sand Canyon Pueblo, including such staples as cheno-ams and groundcherry (Physalis), indicate that foods were processed and meals were prepared in these structures. These activities are indicative of domestic use. Some evidence in the pollen record for this site, particularly the presence of maize (Zea mays) pollen, has been cited as evidence of the use of these kivas for rituals (Gish 1988*2:16; Scott and Aasen 1985*1). However, maize pollen was found in five of six structures sampled, including two structures that were not kivas (Scott and Aasen 1985*1:Figure 1). Thus, although it is likely that maize pollen was used in rituals in ancient times, as it is today, it should not be assumed that the presence of maize pollen in any particular context resulted from ritual placement.

Plant Evidence for Use of Public Architecture

Evidence suggests that two of the buildings tested at Sand Canyon Pueblo were designed for ritual use: the D-shaped building (Block 1500) and Great Kiva 800 (with its associated peripheral rooms) (Kuckelman 2007*1; see also Chapter 4, this volume). Although we searched the plant-remains data for indications of differential uses of these structures as compared with structures used largely for domestic purposes, no such evidence could be detected. We were hampered in these efforts because, at the time of village depopulation, neither building was being used for the purpose for which it was originally designed. Later in the history of the D-shaped block, use appears to have become more heavily domestic. Sometime during the occupation of the pueblo, the structures in Block 1500 apparently changed to domestic use. Use of Great Kiva 800 and its peripheral rooms ended sometime before village depopulation. Thus, the only remains from the original uses of these special structures would have been contained in the secondary refuse associated with these structures; no significant patterns of differential plant use could be detected in the few samples collected from these contexts.

Subsistence Change Through Time

More flotation samples were collected from Sand Canyon Pueblo than from the smaller sites in the Sand Canyon locality, and the occupational history of this large village is more finely dated than those of the other sites that were tested. For these reasons, the plant data for Sand Canyon Pueblo provide an important opportunity to compare patterns of plant use during much of the occupation of the village (about A.D. 1250–1275) with strategies that were adopted later in the occupation of the village (after A.D. 1275) and with those indicated by the very latest deposits of plant remains (materials deposited right around the time of village depopulation, no later than about A.D. 1280).

The probable time of deposition was determined for numerous deposits from which flotation samples were collected and analyzed. Four temporal groups were thus defined to further interpret plant use at Sand Canyon Pueblo. The "Earliest" samples are from plant remains that were clearly deposited early in the occupation of the village; that is, other cultural deposits are located stratigraphically much later than (above) the samples in question. Most of the samples from secondary refuse were categorized as "Early" deposits—these materials were probably deposited during the early or middle portion of the occupation of the village. "Late" samples were from the uppermost layers of secondary refuse and the fills of most thermal features; these materials were deposited near the time of village depopulation. The "Latest" samples include material on ephemeral reuse surfaces just above the floors of kivas and rooms, as well as materials from features located within kiva suites known to have been inhabited until one or more violent events ended the occupation of the village (kiva suites 102, 107, 108, and 1004). These four time periods were used to examine the materials from flotation samples for temporal trends in both nonreproductive (Table 14) and reproductive (Table 15) plant part use, which reflects the use of plants for fuel and food, respectively.

Fuels

Fuel use through time in this village can be compared with that at other post–A.D. 1240 habitations in the Sand Canyon locality. Sites investigated by Crow Canyon as part of the Site Testing Program (Varien 1999*7) include five habitations occupied from A.D. 1140 to 1250 and six others that were roughly contemporaneous with Sand Canyon Pueblo. Across this group of sites, the use of juniper and pine as fuel decreased and the use of shrubs increased as the landscape within the locality became more heavily impacted by humans (Adams 1999*3; Adams and Bowyer 2002*2).

At Sand Canyon Pueblo, the use of pine as fuel appears to have decreased through time, while the use of juniper seems to have remained steady throughout the occupation (Table 5 and Table 14). Also, the use, as tinder, of juniper twigs, juniper scale leaves, and pine bark scales decreased at the end of village occupation, as indicated by a decrease in the ubiquity of these remains from secondary refuse as compared with primary refuse left in thermal features (Table 5). Shrubby taxa—for example, big sagebrush (Artemisia tridentata), bitterbrush (Purshia tridentata), and serviceberry/peraphyllum (Amelanchier/Peraphyllum)—were used less frequently as fuel than at the tested sites (Adams and Bowyer 2002*2). Perhaps the juniper wood being burned near the end of occupation was salvaged from the roofs of structures abandoned by residents migrating from the region; because it was more convenient and abundant than shrubby plants, it became a preferred fuel source by the late A.D.1200s.

Plant Foods

With regard to plant foods, the differences in the ubiquity of reproductive parts from taxa in the samples grouped by time suggest that the plant exploitation strategy changed late in the occupation of the village (Table 15). Strategies to cope with food shortages appear to have been operating when the last fires were built (Adams and Bowyer 2002*2). Just before the village was depopulated, the use of cheno-am, sunflower (Helianthus), prickly pear (Opuntia), groundcherry (Physalis), yucca, and maize (Zea mays) appears to have dropped. The drop in the ubiquity of maize is quite marked—from 50 percent in the samples from the earliest contexts to 8 percent in those from the latest contexts. These results indicate that not only were maize kernels not being prepared widely in the village just before the village and region were depopulated, but also that fewer seeds of cheno-am and groundcherry, plants that are associated with cultivated fields, were being harvested.

Also striking are the increases in the ubiquity of the reproductive parts of numerous wild plants—purslane (Portulaca), lemonade berry (Rhus aromatica var. trilobata), bindweed (Polygonum), and bulrush (Scirpus)—near the end of village occupation. In addition, woolly wheat (Plantago) and winged pigweed (Cycloloma atriplicifolium) seeds were found in only a "Latest" context. Woolly wheat is seldom represented in assemblages in this region. Winged pigweed is not known to have grown near Sand Canyon Pueblo and has not been found at sites in the Sand Canyon locality by Crow Canyon researchers or in the Dolores River valley (Benz 1984*1:Table 46). It is rarely represented in plant remains from sites in the central Mesa Verde region and does not grow at Mesa Verde today (Erdman et al. 1969*1:Table 2). However, it was found in the plant remains from Salmon Ruin (Bohrer 1980*1:347) and has been reported to grow in San Juan County, Utah, today (Welsh et al. 1987*1:127).

Also found almost exclusively in samples from "Latest" contexts were reproductive parts from beeplant (Cleome), pincushion cactus (Mammilaria), and stickleaf (Mentzelia); these samples were analyzed by Scott and Aasen (1985*1) and thus are not included in the tabulations of materials from samples analyzed by Adams and Bowyer presented here. The remains of these wild plants are present in only a few assemblages from sites in the Sand Canyon locality and in the region in general. Beeplant currently grows in arroyo bottoms in the McElmo drainage (Adams 1999*3), although this taxon is not represented in flotation and macrofossil assemblages from the sites located in the McElmo drainage that were tested by Crow Canyon archaeologists (Adams 1999*3).

Although they have rarely been recovered at sites in the Sand Canyon locality, winged pigweed (Cycloloma atriplicifolium), stickleaf (Mentzelia), and woolly wheat (Plantago) seeds were also present in flotation samples from a hearth at Troy's Tower (Adams 1999*3), a tower-kiva complex near Sand Canyon Pueblo that was abandoned after A.D. 1271, just before the regional depopulation (Varien 1999*10). Seeds from plants of these same three taxa were also found in abandonment contexts at Castle Rock Pueblo, a medium-size village near the mouth of Sand Canyon that was abandoned after A.D. 1274 (Kuckelman 2000*1).

A concentration of more than 2,000 unidentified seeds (Scott and Aasen 1985*1:5) was found on the floor of Kiva 107, a "Latest" context at Sand Canyon Pueblo. These seeds resembled sagebrush (Artemisia) seeds (achenes), which were once used by Great Basin groups to make mush (Ebeling 1986*1). Also, three types of seeds that analysts could not identify—possibly from nonlocal habitats—were found in samples from "Late" contexts (Table 15).

In another look at the changes in subsistence through time, Table 16 compares the ubiquity of various weedy and nonweedy wild plants in "Earliest" contexts to those in "Latest" contexts. The ubiquity of both types of plants is greater in the latter contexts.

Lastly, the diversity of taxa in the samples grouped by time is also revealing. The overall diversity of taxa increases from 54 percent for the samples from occupation-era deposits ("Earliest plus Early") to 80 percent for the abandonment-era deposits ("Late plus Latest") (Table 15). The increase in the overall diversity of wild plants, some of which are present in only a few assemblages of plant remains from the Sand Canyon locality, strongly suggests that, near the end of occupation of Sand Canyon Pueblo, the variety of wild plants being exploited for food had increased significantly.

The seasons of availability of the wild plant foods found at Sand Canyon Pueblo are listed in Table 17. Reproductive parts that are available in summer and parts that are available in the fall were both found in "Latest" contexts at the site. The presence of seeds that are available in the fall could be interpreted as indicating that the violent event or events that ended the occupation of the village occurred in the fall.

In sum, there was a decrease in the use of wild plant foods known (on the basis of their ubiquity in samples from numerous other sites in the locality) to have been dietary staples. Also, the use of wild plants that were less widely exploited—and therefore probably less preferred—increased in the final days of village occupation. Thus, near the end of the occupation of Sand Canyon Pueblo, some wild plants were being consumed that were probably growing in the Sand Canyon locality but that had not been used previously. Also, some wild plants that appear to have been obtainable only outside the area were being exploited for the first time near the end of village occupation.

Summary and Conclusions

The archaeobotanical data set for Sand Canyon Pueblo provides significant information on plant resources used in the village both during its occupation and just before the depopulation of the pueblo and the region in the late thirteenth century. The data on weedy plants, fuels, and construction materials indicate that the natural environment in and around Sand Canyon Pueblo was altered significantly during the occupation of the village. A broad suite of domesticated and wild plants were used to meet numerous economic and technological needs of the residents. Main plant foodstuffs used during the occupation included the domesticate maize (Zea mays) and the wild plants goosefoot-pigweed (cheno-am) and groundcherry (Physalis). Several lines of evidence indicate that the villagers were heavily dependent on domesticates, particularly maize, during most of the occupation of the pueblo.

A variety of plant materials were used at Sand Canyon Pueblo for construction material, fuels, tools, and other useful items. Juniper was the wood most commonly used for roof construction in the village. Juniper (Juniperus) and pine (Pinus) were the woods gathered most frequently for fuel and were probably procured in local stands of pinyon-juniper. Maize cobs and shrubby taxa such as chokecherry/rose (Prunus/Rosa), mountain mahogany (Cercocarpus), and big sagebrush (Artemisia tridentata) were also commonly used as fuel. The use of pine declined at the end of the occupation, possibly indicating a depletion of this resource. The use of juniper wood remained relatively high near the time of village depopulation; however, some of the juniper wood used in the latest fires might have been scavenged from the roofs of abandoned buildings, rather than freshly gathered as firewood. The residents of the village fashioned artifacts from numerous local plant resources, including juniper (Juniperus), pine (Pinus), mountain mahogany (Cercocarpus), yucca (Yucca), willow (Salix), and lemonade berry (Rhus aromatica var. trilobata), as well as from gourd (Lagenaria siceraria), which they probably acquired through trade.

The depopulation of the Mesa Verde region in the late A.D. 1200s has been discussed extensively in the archaeological literature. Drought, environmental degradation, population pressures, and conflict are among the causes commonly cited for the depopulation of the region (Dean and Van West 2002*1; Kuckelman 2002*1; Kuckelman et al. 2002*2; Lipe 1995*1; Lipe and Varien 1999*1; Petersen and Matthews 1987*1). Several lines of evidence in the plant data set provide insights into resource availability and use near the time of village and regional depopulation.

There is evidence to suggest a shift in subsistence strategies just before the occupation of the village ended. Late in the occupation, much less maize was prepared and a wider diversity of wild plant foods was procured. In some of the latest contexts at the site, wild plant foods were prepared that were probably not preferred; some of these might have been obtained outside the central Mesa Verde region. The reasons for the changes in subsistence strategies near the end of village and regional occupation cannot be stated with certainty. However, the timing of these changes seems to correlate with a known episode of environmental deterioration. Dean and Van West (2002*1) state that there were several periods of unfavorable conditions in the Mesa Verde region between A.D. 900 and 1500; they state, however, that the conditions during the late thirteenth century were probably the most severe, characterized by low groundwater levels, low crop-yield potential, disrupted seasonal precipitation patterns, a reduced dry-farming belt, and, beginning in 1276, the Great Drought. A shift to a cooler (Petersen 1988*1), drier climate could have drastically lowered, or even destroyed, crop yields and diminished the supply of wild plant foods, including the weedy annuals associated with the crops. To survive, the villagers of Sand Canyon Pueblo and the residents of other sites in the region could have been forced to exploit nonpreferred plants within—and possibly outside—their usual resource catchment areas.

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