Late Pleistocene-Recent Atmospheric delta-13C Record in C4 Grasses
Brewster County Texas
El Paso County Texas
Otero County New Mexico
Pima County Arizona
Puerto de Ventanillas Mexico
C 13 C 12
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CitationToolin, L. J., & Eastoe, C. J. (1993). Late Pleistocene-recent atmospheric delta-13C record in C4 grasses. Radiocarbon, 35(2), 263-269.
AbstractSamples of Setaria species from packrat middens, herbarium specimens and modern plants preserve a record of delta-13C of atmospheric CO2 from 12,600 BP to the present. No secular trend is detected between 12,600 and 1800 BP, when the mean value of delta-13C during that period was -6.5 +/- 0.1 per mil (the error is the standard deviation of the mean). Our value agrees with delta-13C averages of pre-industrial CO2 from polar ice cores, and differs significantly from modern regional (-8.2 +/- 0.1 per mil) and global (-7.7 per mil) values, which are higher because of fossil fuel burning.
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The Record of Native People on Gulf of California Islands [No. 201]Bowen, Thomas (Arizona State Museum, The University of Arizona (Tucson, AZ), 2009)A century ago it was common knowledge among historians and anthropologists with research interests in northwestern Mexico that Indians had inhabited four large islands in the Gulf of California. Three of these islands—Cerralvo, Espíritu Santo, and San José—are in the far southern Gulf off the coast of Baja California. The fourth island, Isla Tiburón, is located on the mainland side more than 400 km to the northwest, in the constricted region of the Gulf known as the Midriff. At the turn of the twentieth century, Isla Tiburón was well known as the homeland of the Seri Indians and was the only Gulf island still inhabited by native people. Since 1900, ethnohistorical and archaeological research has greatly expanded our knowledge of Indians on both sides of the Gulf. Much of that information, however, pertains to the people living on the peninsula and mainland, and touches on the islands only incidentally. Consequently, few historians or anthropologists are aware that Indians made use of many islands in addition to Cerralvo, Espíritu Santo, San José, and Tiburón. Scholars in other fi elds may not even know that there were Indians on the Gulf islands other than Tiburón. This is particularly unfortunate for ecologists because native people have been in the region for thousands of years and may have played a signifi cant role in shaping the island ecosystems we see today. Although indigenous humans were by far the largest native terrestrial mammal on all but two islands, and the most voracious omnivore on all of them, Homo sapiens does not appear on island species lists, and the potential effects of native people on insular ecosystems have seldom been considered. Discoveries made just in the past decade show that researchers in all fi elds have seriously underestimated the extent to which native people made use of the islands. Reports of early Spanish navigators have established the presence of Indians on many islands in addition to the four listed above. Recent archaeological research on several islands, along with fortuitous observations on others, have revealed evidence of native people on islands with no known documentary record of Indians. Chronological data from the southern Gulf establishes a time depth for indigenous people spanning at least ten millennia. New information from Seri oral history alludes to Seri voyages far beyond Isla Tiburón and greatly expands the picture of indigenous people in the Midriff region. Collectively, these results show that the traditional assumption, that most islands were beyond the range of native people, is dead wrong. It is now clear that Indians knew and exploited nearly every signifi cant island in the Gulf. This study reviews the evidence of native people on each of 32 major Gulf islands. The list includes all 22 islands larger than 2 km2 and 10 smaller islands for which some data exist (summarized in Table 3.2). The data are drawn from historical documents, oral history, and the archaeological record. To the extent possible these data are given as quotations from the original sources. Collectively, the evidence suggests that native people were familiar with at least 29 of the 32 islands. For 19 of the islands the evidence can be considered unequivocal, consisting of unambiguous historical documentation, credible oral history, and/or a clear archaeological record. For ten islands there is some evidence of human use, but it is limited, weak, or equivocal, and therefore, in need of corroboration. There are no data of any kind for two islands, and one small island has produced no evidence of native people despite a comprehensive archaeological survey (these data are summarized in Table 4.1). Of course, Indians made greater use of some islands than others. In general, large islands, with a greater diversity of resources (including fresh water), were exploited more than small islands, and several supported permanent or seasonal communities of people. However, native visitors may have been drawn seasonally or intermittently to even very small islands with special resources, such as nesting seabirds, sea lion colonies, concentrations of cactus fruit, and abundant seed crops that appear after a rain. Historic and ethnographic sources show that islands did not need permanent water to sustain native visitors, who were quite capable of bringing water with them, subsisting on temporary water in tinajas, or utilizing water substitutes. Distance was apparently no barrier to native use of islands. The cane balsa was the universal watercraft, and historic sources suggest that balsa traffi c was extensive throughout the Gulf. In the hands of the Indians, the balsa was a swift and seaworthy craft, and navigation was no doubt facilitated by expert knowledge of winds and currents. All but two islands were within a day’s paddle, and in most cases the overwater distance to the more remote islands could have been reduced by island hopping. Although we now know that native people exploited nearly every signifi cant island, we need much more information about the time span over which those visits took place. Indians were certainly making use of many islands during the seventeenth century when European navigators began keeping careful records. Seri oral history fi rmly places Seri ancestors on several Midriff Islands during the nineteenth century and conceivably earlier. Archaeology is potentially capable of extending island chronologies into the prehistoric past, but there has been only limited progress on this front. Fewer than half of the 32 islands considered in this study have been systematically surveyed, and controlled excavations have been conducted on only three islands. Unfortunately, the archaeological record for many islands consists only of surface remains, and includes few or no time-sensitive artifacts or structures, and little or no organic material suitable for radiocarbon analysis. Clovis projectile points from both the Sonora mainland and the Baja California peninsula indicate that humans were present in the Gulf region by 13,000 years ago, which means that native people have been potential island visitors since that time. So far, radiocarbon dates have been secured for only five islands, and for four of these islands the few dates that are currently available all post-date AD 700. However, a series of 179 radiocarbon dates from 40 sites on Isla Espíritu Santo have clearly established this island’s long occupational sequence, which extends from about 9000 BC to the fi fteenth century AD. Although one site on this island produced spectacular radiocarbon ages on shells from approximately 36,550 to greater than 47,500 BP, these shells were probably already ancient when people collected them. During the late Pleistocene and early Holocene it is likely that not all of today’s islands existed, or existed as islands. Some small volcanic islands may not yet have emerged from the sea, while some of today’s islands were connected to the shore by land bridges because sea level was much lower than it is today. Any island without a landbridge connection at that time would have been accessible only by watercraft. These non-landbridge islands should be considered prime places to search for early evidence of navigation. This in turn raises the question of whether initial human entry into the Americas took place by boat along a Pacifi c coastal route, and whether subsequent dispersal involved the Gulf. In most coastal entry and dispersal scenarios, it is assumed that coastally-adapted boat people arriving at the southern tip of Baja California crossed the mouth of the Gulf to the Mexican mainland, making landfall in Sinaloa or even farther south. However, as R. James Hills has pointed out, this is highly unlikely. People arriving at the southern tip of the peninsula would have seen seemingly endless ocean in all directions except along the peninsular coast leading into the Gulf. There would have been no reason for people adapted to coastal resources to set out into an apparently empty sea. Instead, they would have followed the coastline into the Gulf, presumably exploring the islands along the way. The fi rst reasonable place to cross the Gulf would have been the Midriff, where they could have island-hopped to the mainland with no overwater distance exceeding 17 km. In Hills’ scenario, the Gulf would occupy a pivotal position in human dispersal in the Americas, and it is possible that evidence of this process has been preserved on some of the Gulf islands.
Radial Growth Losses in Douglas-Fir and White Fir Caused by Western Spruce Budworm in Northern New Mexico: 1700-1983Swetnam, Thomas W.; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1985-10-31)Regional outbreaks of western spruce budworms (Choristoneura occidentalis Freeman) have recurred at least three times in northern New Mexico since the early 1920's when the U. S. Forest Service first began systematic forest-pest surveys and documentation (Lessard 1975, U. S. Forest Service documents). The current outbreak was first noticed in a small area on the Taos Indian Reservation in 1974, and since then the defoliated areas have increased in New Mexico and Arizona to more than 370,000 acres of Federal, Indian, State and private lands (Linnane 1984). Losses in timber values can generally be ascribed to radial growth loss, height growth loss, topkilling, reduced regeneration, and mortality (Carlson et al. 1983, Fellin et al. 1983). A damage assessment project was initiated in 1978 and was aimed at obtaining measurements of some of these losses in budworm infested stands on the Carson National Forest, New Mexico (Holland and Lessard 1979). A large data base has subsequently been developed, including yearly measurements on topkilling, mortality, defoliation, and insect population changes (Stein 1980, 1981, Stein and McDonnell 1982, Rogers 1984). A growth assessment study was undertaken in 1982 to determine the feasibility of using dendrochronological methods to identify the timing of past outbreaks and to quantify radial growth losses associated with budworm defoliation (Swetnam 1984). Results of this work showed that three major outbreaks during the twentieth century were clearly visible in the tree-ring samples obtained from currently infested trees. The radial growth of host trees was corrected for age, climate and other non-budworm environmental effects, and then growth losses were computed as a percentage of expected growth (Swetnam 1984). Additional collections were obtained in 1984 in order to expand the scope of the radial growth study. The objectives included 1) assessment of a larger number of tree -ring samples, 2) comparison of radial growth losses between the two primary host species - Douglas-fir (Pseudotsuga menziesii) and white fir (Abies concolor), 3) comparison of radial growth losses between age classes, and 4) analysis of the relationship between yearly measurements of defoliation, insect populations and radial growth. This report summarizes the findings of the above analyses. Increment core samples from the 1982 collections are included here, therefore this report supersedes the earlier report (Swetnam 1984). Information is also presented on observations derived from the dated tree-ring series on the timing of occurrence of known and inferred spruce budworm outbreaks for the past 284 years (1700- 1983). This is the longest record of spruce budworm occurrence yet developed for western North America.