Schaafsma, K. Schollmyer, A. Smith, C. Witchlaz (2004). Legacies on the landscape: Integrating ecology and archaeology to understand long-term ...
REPORT OF THE SPRING 2005 FIELD SEASON LEGACIES ON THE LANDSCAPE ARCHAEOLOGICAL AND ECOLOGICAL RESEARCH AT AGUA FRIA NATIONAL MONUMENT
Katherine A. Spielmann, John Briggs, Katie Johnson, Melissa Kruse, Leshana Leslie, Todd Passick, Angela Ruggles, Hoski Shaafsma, and Karen Schollmeyer
School of Human Evolution and Social Change and School of Life Sciences, Arizona State University, Tempe, Arizona September 2005 Submitted to the Bureau of Land Management and the National Park Service, Phoenix, Arizona
Acknowledgments This project would not have been possible without the financial and intellectual assistance of a number of individuals and organizations. We thank Wendy Hodgson, curator at the Desert Botanical Garden (DBG), for the generous contribution of her time and agave expertise to the project. Wendy gave a lecture for the Legacies class at the DBG, helped us devise a coding scheme for the agaves, visited us several times in the field, and linked us up with the University of Georgia research project on agave genetics. Jon Sandor, soil scientist at Iowa State University, visited the project in January and provided a number of insights concerning long-term impacts of prehistoric agriculture in the southwest from his extensive research on the subject. Connie Stone, archaeologist for the Bureau of Land Management in Phoenix, has contributed her expertise on Perry Mesa tradition archaeology throughout the project and facilitated our successful application for funds from the BLM. Trinkle Jones, Cultural Resources Coordinator for the Colorado Plateau Cooperative Ecosystems Studies Unit of the National Park Service, made us aware of funding opportunities in that agency and facilitated our successful application. Mr. Dale Longbrake generously made the Horseshoe Ranch guest housing available to us the last weekend of our field season. Nikol Grant of ASU’s International Institute for Sustainability and Jodi Guyot of ASU’s School of Human Evolution and Social Change have together established our accounts and kept them accurate throughout the project. We are very grateful for the assistance of all these individuals. Although they do not appear as authors on the chapters included in this report, professors Keith Kintigh and Margaret Nelson and students Joanna Iacovelli, Matt Peeples, Jason Sperinck, Nawa Sugiyama, Kristin Uurtamo, Sarah Ventre, and Caitlin Wichlacz contributed to the field research and analyses throughout the field season. The Legacies project was funded by a pilot grant from the ASU Office of the Vice President for Research, by a grant (JSA041006) from the Bureau of Land Management, and a CESU Cooperative Agreement grant (CA-H1200-04-0002) from the National Park Service. Field vehicles were provided by the Department of Anthropology and the School of Life Sciences at ASU. We very much appreciate the financial and material support of these entities.
TABLE OF CONTENTS
Chapter 1, The Legacies Project: Spring 2005 Katherine A. Spielmann …………………………………………………..1 Chapter 2, Agave Types and Distribution at La Plata, Richinbar, and Pato Pueblos, Agua Fria National Monument LeShana Leslie, Todd Passick, and Angela Ruggles……………...4 Chapter 3, Agricultural Impacts on Soil compaction and Sediment Size at Agua Fria National Monument Katie Johnson………………………………………………….....24 Chapter 4, Legacy Effects on Herbaceous Plants at Agua Fria National Monument Hoski Schaafsma and John Briggs……………………………….36 Chapter 5, Transect Survey Report, Richinbar Ruin Vicinity, Spring 2005 Melissa Kruse…………………………………………………….47 Chapter 6, Architecture Studies at Richinbar Ruin, Spring 2005 Karen Gust Schollmeyer…………………………………….........59 Chapter 7, Agricultural Site Survey Melissa Kruse …………………………………………………....65 Bibliography……………………………………………………………………………...80
CHAPTER 1 THE LEGACIES PROJECT: SPRING 2005 Katherine A. Spielmann The Legacies project is a long-term, collaborative research and teaching project between archaeology and ecology faculty and students at Arizona State University. The goal of the project is to document and understand the long-term ecological impacts of the prehistoric occupation of the semi-arid landscape of Agua Fria National Monument in central Arizona. The field research is organized through a seminar in which ecology and archaeology faculty jointly engage students in the collection and analysis of ecological and archaeological data relevant to our over-arching research theme. Our first field season occurred in the Spring of 2004 (Kruse and Spielmann 2004; Schollmeyer 2004; Schollmeyer et al. 2004). During this pilot season we collected and analyzed a variety of ecological and archaeological data in and around the site of Pueblo la Plata on Perry Mesa. Through the course of this season we archaeologists and ecologists learned how to work together and determined which kinds of data and data collection strategies would be most useful to the project. The results of this initial field season then set the stage for the spring 2005 field session, in which we focused particularly on the legacy effects of prehistoric agricultural practices. Project Objectives In planning our spring 2005 field season we identified two goals. Our primary objective was to classify the Perry Mesa landscape with respect to agricultural field types (e.g., terraces, linear borders, and rock pile fields) and geomorphic features to use in concert with aerial photos and multi-spectral satellite photos. We had hoped to be able to identify the signatures of agricultural field types on satellite imagery so that we can measure the extent of prehistoric agricultural production on the mesa. Heavy rains and new opportunities, however, caused us to alter our primary objective somewhat. Due to flooding of the Agua Fria River our primary research location at the monument, Perry Mesa, was inaccessible until mid-March. Although we attempted to collect agricultural data on Black Mesa one Friday in February, the unusually high grass cover (knee to waist-high) obscured many of the agricultural features we were endeavoring to map, making accurate data collection impossible. In March, once back on Perry Mesa we expanded our data collection on agricultural fields to include not only the locations of the fields, but also ecological data on and off a sample of fields. These data included soils and herbaceous vegetation data. We also developed a more comparative approach than had been present in the original research design for the field season, and collected agave, agricultural field, ecological and archaeological transect data, and bonding and abutting data from Richinbar Pueblo on Black Mesa to compare with similar data from Pueblo la Plata.
Figure 1.1. Location of Spring 2005 fieldwork.
Early in the spring semester, John Briggs initiated contact with Wendy Hodgson at the Desert Botanical Garden, which led us to develop a focus on human manipulation of agave at Agua Fria National Monument. Wendy’s interest in the degree of hybridization of agaves on the monument led us to a research focus on variability in agave species among three pueblo villages (La Plata, Richinbar, and Pato; Figure 1.1) there. Our second goal for the project had been to complete the bonding and abutting study begun in spring 2004 at Pueblo la Plata. Two-thirds of the pueblo had been mapped during that field season. By the end of the spring 2005 field season we had met and surpassed our second goal by completing the mapping at Pueblo la Plata as well as mapping the pueblo of Richinbar on Black Mesa. The total length of time we spent in the field this field season was ten days: 7 days in March and 3 days in April. This report presents the methodologies and results from our data collection and analyses of agave types and distributions, agricultural field locations, on and off-field soil and herbaceous vegetation information, ecological and archaeological data from the Richinbar transect, and bonding and abutting data for Richinbar pueblo. The complete analysis of the Pueblo la Plata bonding and abutting study is presented in Sarah Mapes’ (2005) senior honors thesis. Melissa Kruse’s forthcoming Masters paper analyzes the relationship between agricultural field locations and geomorphic features. In the future we will be able to use the insights from her analysis in concert with aerial photos and multi-spectral satellite photos to create the landscape classification that had been the original focus of the Spring 2005 field season.
CHAPTER 2 AGAVE TYPES AND DISTRIBUTION AT LA PLATA, RICHINBAR, AND PATO PUEBLOS, AGUA FRIA NATIONAL MONUMENT LeShana Leslie, Todd Passick, and Angela Ruggles
During the Spring 2005 field season we collected morphological information on over four hundred agaves near the pueblos of La Plata and Pato on Perry Mesa and Richinbar Ruin on Black Mesa. Our goal was to document the distribution and diversity of different agave species among these villages and to determine whether hybridization had occurred at any of these sites. Early in our data collection we were fortunate to be introduced to Drs. Kathleen and Alan Parker, plant geneticists from the University of Georgia who are working with Wendy Hodgson on genetic variation in Arizona agaves. They agreed to analyze some agave samples from the AFNM agave fields and showed us how to sample the agaves for genetic research. Sampling involves cutting the top 3 inches (including spine) from one leaf per plant using a serrated knife. Agave samples are labeled (site number, plant number) right on the leaf segment using a Sharpy marker. We pin-flagged each agave we measured with a number, and thus our agave genetic information can be matched with the agave measurement information. Methodology Agave fields are distributed differently among the three pueblos (Figure 2.1-2.3). At La Plata there are four discrete agave fields, three along the southern edge of the mesa and one to the northeast of the site along the northern edge of the mesa. One of the three fields on the southern mesa, Agave Field 1, appears to be a humanly created rock pile field. The other three fields, Agave Fields 2, 3, and 4, take advantage of naturally broken up, rocky terrain on the edges of the mesa. We collected leaf data on all the mature agaves in each field, as well data from many of the fluorescences (stalks). In total we have information from about 40 to over 70 individual plants per field. We took tissue samples from 24 plants in each field, emphasizing diversity in our sampling strategy. We also used the GPS to map the perimeter of each field. At Richinbar, the agave “field” is continuous rather than discrete, with a fairly dense concentration of agaves extending for quite some distance in the rocky terrain north of the pueblo. There are no obvious humanly constructed rock piles there. We measured 74 plants and collected tissue samples from 48, spreading the recording teams across the agave area to maximize spatial coverage. We again used the GPS to map the perimeter of this agave area, which ends on the south side with the end of the rocky terrain at the pueblo, and which we arbitrarily ended at the dirt road on the north due to extensive disturbance beyond this point. At Pato, agaves are relatively continuously distributed along the rocky edges of the mesa to the north and east of the site. They are no clear rock piles here; again, people took advantage of the naturally broken, rocky terrain. Agaves are not as dense at Pato as at Richinbar. Given the continuous and extensive distribution of agaves, we created ten collection areas so that our sampling would be distributed across the entire agave “field.” We collected 5 tissue samples and measured 10 agaves in each of these areas. 4
Figure 2.1. Map of La Plata agave fields.
Figure 2.2. Map of Richinbar agave field.
Figure 2.3. Map of Pato agave area, with collection sites noted.
Figure 2.4. Coding sheet used for collecting agave data. Agua Fria Agave Morphometric Analysis Site _______
N _____________ E ____________ Elev __________
Arch. Features ___________________________
Leaf w/1 (mm)
Spine 1 (mm)
Soil characteristics _____________________________________________________
Associated Vegetation ______________________________
Teeth midway pt?
Dist from arch
Wendy Hodgson, of the Desert Botanical Garden in Phoenix, helped us to create a coding system for the agave data (Figure 2.4) which we used at all three sites. It is important to note that our data collection took place before the flowering season, and thus our variables focused either on leaf attributes of live plants or stalk attributes of dead ones. For each live plant we noted whether the plant was an individual or suckering, and if suckering, the number of pups present. Then five leaves were measured for leaf length and width, terminal spine length, whether interstitial teeth were present or absent, distance from archaeological sites, and whether or not the teeth began at the base of the leaf or midway along its length. In some cases the interstitial teeth variable was marked as a “yes/no,” indicating that teeth were present on some but not all leaves on an individual plant. Partway through the data collection we also noted the location of the widest point of the leaf. Table 2.1. The number of agave measured at each site. Site Pueblo la Plata Field 1 (Perry Mesa) Pueblo la Plata Field 2 Pueblo la Plata Field 3 Pueblo la Plata Field 4 Pueblo Pato (Perry Mesa) Richinbar (Black Mesa) Total number of plants
Count 71 29 60 75 100 75 410
Agave tissue samples were sent to the geneticists in mid-March. Given that they could only accommodate samples from four sites in their current research, it was suggested that they analyze the La Plata samples from field 1 (the rock pile field to the southwest of the pueblo) and field 4 (the field on the north side) along with the samples from Pato and Richinbar. Wendy Hodgson is curating the samples from fields 2 and 3 at la Plata. This report presents three preliminary analyses of the morphological data that we collected on the agaves. The first discusses whether there are distinct types of agave represented in our samples, and whether hybridization has occurred. The second then evaluates the intrasite variability in agave across the field areas associated with each pueblo village, and the third is an inter-site analysis of similarities and differences in agave morphology. The agave analyses are on-going. Updated versions will be presented in a paper at the 2006 Annual Meeting of the Society for American Archaeology. Agave Types In this analysis, morphological similarities are used to identify distinct types of agave at the three pueblo sites. These types are then compared to the known species that are present in the Agua Fria area, A. chrysantha and A. parryi.
Of the 410 agave that were measured last spring, 292 were live and 118 were dead. Live plant data are the focus of this analysis. Although the fluorescence of an agave, live or dead, can help determine the species, other measurements such and leaf length and width cannot be accurately taken from dead plants because the leaves are withered. The variables chosen for this analysis included ratio of the leaf width to length, terminal spine length, presence of interstitial teeth, and whether the teeth began midway up the leaf. The ratio of the leaf width to length is used to factor out the impact of gross size (related to age) in the morphological analysis. In order to identify agave types, we first created groups based on occurrence of interstitial teeth (none, always occurring, sometimes occurring). Given each of these groups, an average linkage hierarchical cluster using Euclidean distance (Figure 2.5 a-d) was used to create further subdivisions using the leaf length-width ratio, terminal spine length and whether or not the first teeth occurred at or above the midpoint of the leaf. Table 2 displays the summary statistics for each cluster. Clusters 11 and 12 represent A. chrysantha and A. parryi respectively. Cluster Analysis Results Group A includes clusters with no interstitial teeth. Even though they are similar, the three clusters show some differences (Table 2.2). For instance, the mean terminal spine length in cluster two, at 4.1 cm, is half again as long as the terminal spine mean of cluster one, at 2.8 cm, although the leaf width/length ratio of the two clusters is similar (0.214 for cluster one and 0.209 for cluster two). (Cluster six has only one plant, which seems to be an outlier.) The terminal spine, at 6.60 cm, is more than twice that in cluster one and half again as much as that of cluster two, while the leaf width/length ratio is much lower, at 0.144. Group B, which includes clusters five, seven, and nine, represents clusters that exhibit interstitial teeth (Table 2.2). Clusters five and seven of this group are similar to clusters one and two of group A in their leaf width/length ratios 0.194 (Cluster 5), and 0.205 (Cluster 7). The terminal spine mean length of cluster five at 4.0 cm is similar to that of cluster 2, and that of cluster seven at 2.6 cm is similar to cluster 1. The only agaves in this group exhibiting teeth that begin at the midpoint of the leaves are those in cluster nine. The leaves of this cluster appear to be wider and shorter than those of clusters five and seven, and the terminal spine mean of cluster nine falls between those of clusters five and seven. The final group, C, includes clusters three, four, eight and ten. The individual agaves in this group have leaves that exhibit interstitial teeth and leaves where interstitial teeth are absent (Table 2.2). Similar to the previous two groups, the clusters in this group, with the exception of cluster 8, have leaf length/width ratios that are alike. Only the terminal spine length varies among these three clusters. The terminal spine means of cluster four, at 3.7 cm, and cluster ten, at 3.6 cm, are the most similar and these two clusters may be a single type. The terminal spine mean of cluster three, at 2.5 cm, is much shorter than that of clusters four and ten. Similar to cluster six of Table 2 A, cluster eight appears to be comprised of two outliers. The terminal spine mean is much longer at 5.4 cm than any other agaves in this group and the ratio of width/length is much lower at 0.133.
Figure 2.5a. Boxplot of presence or absence of interstitial teeth of each cluster where cluster 11 is A. parryi and cluster 12 is A.chrysantha. Absent interstitial teeth is denoted as 0, present as 1, yes/no as 2.
Figure 2.5c. Boxplot of terminal spine length of each cluster where cluster 11 is A. parryi and cluster 12 is A.chrysantha.
8 7 6 5
-0.5 0.0 0.5 1.0 1.5 2.0 INTERSTITIALS (Presence/Absence)
Figure 2.5b. Boxplot of the width/length ratio of agave leaves, where cluster 11 is A. parryi and cluster 12 i 13
1 2 3 4 5 SPINE LENGTH (centimeters)
Figure 2.5d. Boxplot indicating if teeth begin at midway point on leaves for each cluster. Cluster 11 is A. parryi and cluster 12 is A.chrysantha. Teeth beginning below midway is denoted as 0, at or above midway as 1.
6 5 4
8 7 6 5
0.1 0.2 0.3 0.4 0.5 RATIO (Leaf Width/Leaf Length)
0.0 0.5 1.0 TEETH MIDWAY
An outlier from Cluster 9 (PA4_43) has been omitted to form a clearer picture of the remaining clusters.
Table 2.2. Summary Statistics for Average Linkage Hierarchal Cluster Analyses using Euclidean Distance. The clusters have been grouped together according to interstitial presence or absence for easier analysis. Measurements represent mean values in cm. Group A) No Interstitials B) Interstitials C) Mixed
Cluster 1 2 6 5 7 9 3 4 8 10
Number of Agave 65 41 1 15 36 30 62 24 2 16
Width/length Ratio .21 .21 .14 .19 .21 .27 .21 .20 .13 .23
2.8 4.1 6.6 4.0 2.6 3.1 2.5 3.7 5.4 3.6
0 0 0 0 0 1 .05 0 0 1
Overall, this analysis suggests that the agave on Perry Mesa commonly have a range of width/length ratios for their leaves from about .10 to .35 with a mean of about .20, with spine lengths that vary from about 2 to about 5 cm with a mean between 3 and 4 cm. They may or may not have interstitial teeth, or interstitial teeth may occur on some leaves but not others. There seem to be a few isolated individuals with comparatively narrow leaves and comparatively long terminal spines (clusters 6 and 8). In addition to clustering the plants into types, I compared the plant clusters to the species of agave found at Perry Mesa and Black Mesa. The two species are A. parryi and A. chrysantha (Wendy Hodgson, personal communication). A. parryi has a large range of variability with broader leaves, shorter spines, and no interstitials, while A. chrysantha has a more narrow range of variability with longer, narrower leaves that exhibit longer terminal spines and interstitial teeth. (Table 2.4). In order to convey a clearer picture of the association between A. parryi and A. chrysantha I used boxplot graphs for each of the four variables that were used in the cluster analysis. Table 2.3. The measurement range of variables for A. parryi and A. chrysantha (Hodgson 1999; Flora 2002) A. parryi
Terminal Spine Length
Min: 4.5 cm Max: 20 cm A. chrysantha Min: 4.1 cm
10 cm 65 cm 40 cm
1.50 cm 3.0 cm 2.5 cm
0 (no) 0 (no) 1 (yes)
0 (no) 0 (no) 0 (no)
Max: 11 cm
Table 2.4. Site variable means Site Pato Richinbar La Plata
Ratio 0.194 0.206 0.225
Spine 2.89 3.03 3.30
Midpoint 0.00 0.00 0.34
Conclusion Although this analysis is intended as a baseline for future research on the agave of Agua Fria, the preliminary results suggest that the agave found in the vicinity of archaeological sites do not fit the standard definition of either species well. Rather there seems to be a range of spine lengths evidently similar to A. chrysantha and width/length ratios close to those of known A parryi that does not seem well-separated by the presence or absence of interstitial teeth as the species definitions would suggest. A. parryi is known to hybridize with A. chrysantha (Flora, 2002) and hybridized A. chrysantha have been found on Perry Mesa (Wendy Hodgson, personal communication). These clusters may also represent different species that have yet to be identified or varieties of A. parryi and A. chrysantha.
Analysis of Agave Intra-Site Variability Given the marked difference in leaf width/length ratios between Agave parryi and Agave chrysantha, we chose to use this variable in a preliminary investigation of intrasite variation in agaves at the three pueblos. Figure 2.1 shows the locations of the four discrete agave fields at La Plata and Figure 2.6 illustrates the variation among the discrete agave fields at that site. Most noticeable is the greater degree of variation within the spatially separate field 4. Field 4 was also distinct in being the only one at the site to have interstitial teeth begin above the leaf’s midway point. Figure 2.2 shows the locations of the ten separate collection areas at Pato Pueblo, and Figure 2.7 illustrates the variation in leaf width/length ratio among them. Two fields closest to the pueblo, 8 and 9, exhibit the smallest ratios, while one furthest away exhibits the largest ratio. Whether this variation is due to cultural factors, such as different families bringing different agave stock with them, or microenvironmental variables is not clear at this point. Figure 2.3 illustrates the extent of the agave north of Richinbar Ruin. We divided this area into three sub-areas for data collection. Figure 2.8 illustrates the variation in leaf lengthwidth ratio among them. As with Pato pueblo, plants with the largest width/length ratio (broader leaves) are furthest from the pueblo. Overall, the analysis of this single variable identified spatially discrete concentrations of morphologically distinct agave only in two fields at Pueblo Pato. Nonetheless there is enough spatial variation in plant morphology to warrant further data collection, particularly with regard to microenvironmental variables that might affect agave growth patterns.
Agave Field 1
Agave Field 2
Agave Field 3
Agave Field 4
Figure 2.6. Boxplot of leaf width/length ratios among the four fields at Pueblo La Plata.
.1 .15 .2 .25
Width/length ratio Figure 2.7. Boxplot of leaf width/length ratios across the ten agave data collection areas at Pueblo Pato.
Width/length ratio Figure 2.8. Boxplot of leaf width/length ratios across agave data collection areas at Richinbar Ruin.
Intersite Analysis of Agave Morphology Four variables were used to compare the live plants among the La Plata, Pato, and Richinbar Pueblos. These variables were the ratios of leaf width to length, the terminal spine lengths, the presence or absence of interstitial teeth, and whether or not interstitial teeth started above the midway point. The means of each of the plant’s leaf lengths, widths, and terminal spine lengths were determined for each data collection area, followed by the calculation of each plant’s average leaf width/length ratio. The averages of these four variables were then calculated for each field in each of the three sites. As the values of all of these variables fall between 0.0 and 2.0, these data were not standardized prior to analysis. The initial analysis shows that Richinbar Ruin and Pueblo Pato are more similar to each other than either is to La Plata. The technique employed here was an average linkage hierarchical cluster analysis, based on the Euclidean distance of the variables, at the field level. The sites are designated as PA (Pueblo La Plata), PO (Pueblo Pato) and RI (Richinbar Ruin), followed by the field number when used. Figure 2.9 shows the dendrogram resulting from this cluster analysis.
Figure 2.9: Dendrogram of field relationships. PA= LaPlata, RI= Richinbar Ruin, and PO=Pato. This initial cluster analysis was performed at the field level, rather than the site level because one field at La Plata, field 4, is unique in that it contains plants whose interstitial teeth begin above the leaf’s midway point. La Plata’s field 4 provided 75 of the 231 plants measured at this site, or 32.5%. Running a cluster analysis using the means from each individual field prevents La Plata’s field 4 from representing La Plata agaves as more dissimilar from the other sites than they actually are. When cluster analysis was applied to the variable means from each site, with the midway variable excluded from the cluster analysis (to minimize the effect that La Plata’s field 4 has on the measure of overall similarity), Pato and Richinbar are joined at a distance of 0.12, and are in turn joined to La Plata at a distance of 0.31, further supporting the conclusion that Pato and Richinbar are different from La Plata. The next step in the analysis was to examine whether a particular variable, or ratio of variables, contributed the most to intersite variation. As shown in some of the stacked boxplots below, Pato and Richinbar tend to be more similar to each other than either is to La Plata. The first variable to be analyzed was the width/length ratio. The boxplot shown in Figure 2.10a illustrates that this ratio is relatively consistent across the sites. There is one extreme outlier, plant 43 from La Plata’s field 4, whose ratio is 1.15. For the purposes of this analysis, this case was excluded and the analysis rerun. The boxplot for this second analysis is shown in Figure 2.10b. With the omission of plant 43, it is seen that there is still very little difference in ratios across all sites, except that ratios at La Plata are generally slightly larger. This overall 17
similarity in ratios indicates that the results of the preceding cluster analyses were more dependent upon the variables of terminal spine length and interstitial teeth, than they were on the ratios of the leaves’ widths to lengths.
Figure 2.10 a and b. Boxplots of leaf width to length ratios at each site. RI= Richinbar, PO=Pato and PA= La Plata. A comparison of terminal spine lengths, shown in Figure 2.11, demonstrates that Pato and Richinbar are more similar, and La Plata’s spines longer. La Plata’s median spine length is 3.20 cm, while those at the other two sites are identical at 2.80 cm.
3 4 5 Terminal Spine (cm)
Figure 2.11: Boxplots of terminal spine length at each site. RI= Richinbar, PO=Pato and PA= La Plata. 18
Comparison of Dead Plant Variables Across Sites Although the results of the live plant variable analyses support the inference that Pato and Richinbar are more alike, a similar examination of the dead plant variables suggests that Pato and La Plata are more similar to each other than either is to Richinbar. This discrepancy is explained by contemporary agave harvest practices. The inflorescences of Richinbar agaves are cut by local ranchers to be used as fodder for their cattle. In fact, while in the field collecting data at Richinbar, it was noticed that there were very few fallen inflorescences, and that most of the agave showed signs of having had their inflorescences cut. The boxplots for these variables indicate that the longest and widest inflorescences are preferred for cattle fodder, resulting in smaller inflorescences left for us to measure. The median inflorescence heights, shown in Figure 2.12 are identical at Pato and La Plata, and the difference in their means is only 4.23 cm. The median inflorescence widths at Pato and La Plata are also identical, as shown below in Figure 2.13. Inflorescence depth was measured as the proportion of the inflorescence from which laterals protruded, and was recorded as an estimated fraction. The boxplots in Figure 2.14 show that all sites are identical in having a median inflorescence depth of 0.33. The only real difference among the sites in terms of this variable is that the range of Richinbar’s inflorescence depths only varies by a value of 0.08, while Pato’s varies by 0.25, and La Plata’s by 0.33.
Figure 2.12. Boxplots of inflorescence heights at each site. RI= Richinbar, PO=Pato and PA= La Plata.
4 6 8 10 Inflorescence Width (cm)
Figure 2.13. Boxplots of inflorescence widths at each site. RI= Richinbar, PO=Pato and PA= La Plata.
0.25 0.50 Inflorescence Depth
Figure 2.14. Boxplots of inflorescence depth at each site. RI= Richinbar, PO=Pato and PA= La Plata. When the dead plant variables are examined individually they indicate that Pato and La Plata are more similar to each other than either is to Richinbar. However, the fact that the Richinbar inflorescences have been affected by modern human intervention must be taken into account. This selective process appears to have resulted in the remaining inflorescences being smaller and less varied. Another factor to consider is the differences in sample sizes taken at each site. While data for eighty-two inflorescences were collected at La Plata, Pato’s data only includes twenty, and Richinbar’s only eleven. The only variable that may be said to represent
undisturbed dead plant variability among these sites is the number of laterals, which would most likely not be a selective factor. This variable alone supports the findings of the live plant data analyses, that Pato and Richinbar are more similar to each other than either is to La Plata. When the dead plant variables are examined individually they indicate that Pato and La Plata are more similar to each other than either is to Richinbar. However, the fact that the Richinbar inflorescences have been affected by modern human intervention must be taken into account. This selective process appears to have resulted in the remaining inflorescences being smaller and less varied. Another factor to consider is the differences in sample sizes taken at each site. While data for eighty-two inflorescences were collected at La Plata, Pato’s data only includes twenty, and Richinbar’s only eleven. The only variable that may be said to represent undisturbed dead plant variability among these sites is the number of laterals, which would most likely not be a selective factor. This variable alone supports the findings of the live plant data analyses, that Pato and Richinbar are more similar to each other than either is to La Plata.
10 20 Number of Laterals
Figure 2.15: Boxplots of number of laterals at each site. RI= Richinbar, PO=Pato and PA= La Plata.
Implications While it is clear that La Plata is different from the other sites in terms of live agave morphology, the question remains as to why this is the case. One possibility is that the spatial proximity of Pato and Richinbar accounts for their similarity, and La Plata’s distance from both of these sites explains its dissimilarity (see Figure 2.16). While both La Plata and Pato are situated on Perry Mesa, and Richinbar is situated on Black Mesa, Richinbar and Pato are much closer to each other, and are inter-visible. Prehistoric occupants at the latter two pueblos sites may have been able to interact with each other much more easily than they could with the occupants of La Plata. Another potential explanation is environmental variability. Factors such as soil composition, precipitation levels, and slope gradient, cannot be ruled out as an explanation for intersite variability until we have collected and analyzed data on these environmental variables.
Figure 2.16: Locations of sites discussed in analysis.
Conclusion Agave data collection and analysis has resulted in preliminary findings that stand as hypotheses for evaluation with further data. In particular, DNA data from the genetic analyses planned at the University of Georgia will assist in understanding the nature and degree of hybridization, as well as intra and inter-site variability identified in the studies discussed here. Future agave flower collecting for chromosome analysis will similarly be helpful in evaluating the distinctions made on the basis of our morphological data. Finally, moving away from the agricultural to the ceramic, the hypothesis that there was greater interaction between Richinbar and Pato than with La Plata can be evaluated with ceramic provenience data currently being collected and analyzed by David Abbott and Caitlin Wichlacz.
CHAPTER 3 AGRICULTURAL IMPACTS ON SOIL COMPACTION AND SEDIMENT SIZE AT AGUA FRIA NATIONAL MONUMENT Katie Johnson Many factors affect soil composition, including the parent rock, wind, rain, volcanic activity, time, rodent burrowing, and human activities (Sandor et al. 2005). Human actions that impact soil properties range from agricultural practices to building and mining. This paper focuses on understanding the long-term effects of prehistoric agricultural production on soil compaction and sediment size around La Plata, Pato, and Richinbar pueblos. The purposed of this study was to determine if there were differences in soil characteristics due to prehistoric agriculture. Methods Samples were collected from on and off prehistoric agricultural fields in order to determine if there were significant differences in soil characteristics due to the legacy effects of agriculture. Controls were placed in areas adjacent to the agricultural fields and every effort was made to locate the control plots in areas that were topographically similar to the agricultural terraces but that had no physical indications (e.g., rock piles or linear alignments) of prior farming. I also collected data around the room blocks at these sites from within the relatively unvegetated ring that is apparent around all three pueblos. It is not known if this cleared area is the product of agricultural processes or simply the result of being in a high traffic area. For the compaction analysis, the method consisted of using an open-ended soup can (450ml), placing it about 2-5 cm into the ground so that a seal is created, and pouring 300 ml of water into the can. The amount of time that it takes for the water to be absorbed by the soil is then recorded and is expressed as a ratio of ml/sec. The longer it takes for the water to infiltrate, the more compact the soil is. This ratio can then be compared across samples to evaluate whether there are differences in soil compaction. Our sampling regime was originally designed so that we would establish transects across the terraces at the three sites, and take ten compaction samples from each terrace along these transects. After the first sample was taken, however, it became clear that the plan would have to be changed. The water had not been absorbed after 20 minutes had passed, and there was not enough time to take that many samples in the time available to us. We decided to alter our collection method to two to three samples per terrace, and instead of a transect through the center of the terrace we simply took a sample from the front (lower slope) and the back (upper slope). When a third sample was taken, it was taken from the center of the terrace between the other two. We also decided that if the absorption time exceeded 20 minutes we would measure the water remaining, and use it to determine the amount of water that had already been absorbed to calculate the infiltration rate in ml/sec. This timing was later reduced to 10 minutes. By measuring the
height of the water in the can after ten minutes, we were able to calculate the amount of water (volume of a cylinder) left in the can. Thus, we were able to estimate the amount of water that was absorbed. Samples were also taken outside of the agricultural features to use as controls in order to determine if there was a significant difference between agricultural and nonagricultural areas. In addition, because each pueblo is clearly ringed by an unvegetated area, we decided to sample these rings as an exploratory investigation into why the vegetation was so sparse. For the collection of the sediment we took one to two samples from terraces, as well as control samples and pueblo ring samples. After air-drying, 500 g of each sample were sifted for 15 minutes through soil screens of size 10=2 mm, 18=1 mm, 35=.5 mm, 60=.25 mm, and 230=.063 mm; data were also collected from the pan for sediment under .063 mm in size. The amount of soil from each screen was then weighed and the percentage of the total was recorded. Samples were collected from terraces A, B, C and H at La Plata for soil compaction and A, C, and H for sediment analysis (Figure 3.1). Six controls and four samples from the pueblo ring were also collected for soil analysis, and two controls and two samples were taken from the pueblo ring for sediment size analysis. Very few samples were taken from Pato, and thus it should probably be excluded from the analysis. One sediment sample was taken from each of the terraces there, as well as one control (Figure 3.2). Samples were taken from terraces A, C, and D and two controls for compaction; however no pueblo ring samples were taken. The most samples were taken from Richinbar. Three compaction samples were taken from each terrace A, B, and C (Figure 3.3), and eleven controls were taken on the slope across the wash from the terraces; four samples were taken from within the pueblo ring. Two sediment samples were also taken from each terrace, as well as nine controls in the same areas as the compaction controls, and four samples from within the pueblo ring.
Figure 3.1. Map of terraces south of Pueblo la Plata.
Figure 3.2. Map of sample locations at Pueblo Pato.
Figure 3.3. Map of terraces at Richinbar Ruin.
ABSORPTION RATE IN ML/SEC
(1) LA PLATA
FRONT BACK FRONT BACK
0.106 0.09 0.234 0.154
FRONT MID BACK FRONT BACK
0.234 0.176 0.09 1.667 0.154 0.434
TERRACE B TERRACE C
AVERAGE PUEBLO RING
AVERAGE AVERAGE WITHOUT TERRACE A BETWEEN TERRACE AND PUEBLO
0.357 0.169 0.106 0.122 0.188 0.714 0.714 0.869 1 1.429 0.106 0.805 3.333 5 5 2 6.667 2.5 0.667 0.294 0.122 0.138 0.556 2.389 0.355 1.25 1.25 1.25 0.147
MID BACK FRONT MID
0.115 0.115 0.115 0.436
AVERAGE BELOW TERRACE H BETWEEN TERRACE AND PUEBLO
N SLOPE BELOW AGAVE FIELD 4
AVERAGE (2) PATO
MID BACK TERRACE C
FRONT MID BACK FRONT BACK
AVERAGE (3) RICHENBAR TERRACE B
BACK FRONT MID BACK AVERAGE LOWER EDGE OF SE SLOPE LOWER SLOPE ACROSS WASH FROM TERRACE UPPER SLOPE ACROSS WASH FROM TERRACE
0.307 0.211 0.952 0.372 0.308 0.276 0.372 0.5 0.372
0.243 0.275 0.339
AVERAGE OUTSIDE OF AG. AND PUEBLO #1 #2 #3 #4 #5 AVERAGE
0.211 0.147 0.625 0.404 0.347 0.307 0.404 0.307 0.275 0.275 0.314
NEAR PUEBLO MID MID OUTER EDGE OF RING
Table 3.1. Raw data for soil compaction analysis. Soil Compaction Using an average of all the infiltration data on the terraces, pueblo-ring and controls at La Plata (Table 3.1), it was found that on average the controls had the highest infiltration rate while the pueblo ring had the lowest; the rate for the terraces was intermediate between the two (Figure 3.4).
Infiltration Rate (ml/sec)
Terraces Pueblo Ring Controls
Figure 3.4. Infiltration rates for Pueblo la Plata
At Pato, in contrast, the terraces had a much higher infiltration rate than the controls (pueblo-ring was not sampled; Figure 3.5). Terrace A’s infiltration rates, however, were much higher than those of all other samples. If the data from that terrace are excluded, then the pattern at Pato is similar to La Plata with the terraces exhibiting higher compaction than the controls. Terrace A’s extremely high infiltration rate could be due to many different factors, and it is possible that it was not a terrace.
Pato With out Terrace A 1.4
Pato fields Pato control
Infiltration Rate (ml/sec)
Infiltration Rate (ml/sec)
Pato fields -A Pato control
Figure 3.5. Infiltration rates for Pueblo Pato.
Richinbar’s data from the terraces and controls show the same trend as those from La Plata and Pato, but the differences between the sampling loci are so small that they are not significant (Figure 3.6). At Richinbar, in contrast to La Plata, the pueblo ring is less compact than the controls and the terraces. This could indicate that the area around Richinbar Ruin was not as intensely used or that it was used for a different purpose. Current data are insufficient to identify the use of this area.
Infiltration Rate (ml/sec)
Terraces Pueblo Ring Controls
Figure 3.6. Infiltration data for Richinbar Ruin.
Sediment Size In general, the sediment size analysis mirrors the compaction data, with the terraces having smaller sediment sizes than the controls (Table 3.2). This was expected since sediment size affects infiltration. At La Plata, the pueblo ring had the largest percentage of smaller sediments, while the controls had the largest percentage of larger sediment sizes. Likewise, at Pato large sediment sizes comprise a larger percentage of the sediments in the control areas than on the terraces. Pato’s terrace A sediment size for screen 10 is somewhat of an outlier, paralleling the compaction data.
LA PLATA TERRACE A (N) BACK SIDE TERRACE A (S) FRONT SIDE TERRACE C (N) BACK SIDE TERRACE C (S) FRONT SIDE TERRACE H (N) BACK SIDE TERRACE H (S)FRONT SIDE
x>2mm 335.8 176.5 275.3 136.1 119.1 239.6
%of Total 2mm>x>1mm 0.6767432 64 0.3541332 109 0.5537007 83.7 0.2745058 136.8 0.2399758 135.1 0.4807384 98
%of total 1mm>x>.5mm 0.12898 34.6 0.2187 73.9 0.168343 43.9 0.275918 90.4 0.272214 92.9 0.196629 73.8
%of total .5mm>x>.25mm 0.06973 20.6 0.148274 61.8 0.088294 24.9 0.182332 61.3 0.187185 59.7 0.148074 49.1
% of total .25mm>x>.063mm 0.0415155 23.1 0.1239968 48.6 0.0500805 38.9 0.1236386 67.2 0.1202901 78.6 0.0985152 31.6
%of total x2mm 2-1mm 1-.5mm 0.5-.25mm
% of Sediment Sizes
% Of Sediment Size