Dataset Information

Carbon starvation in glacial trees recovered from the La Brea tar pits, southern California.

ABSTRACT: The Rancho La Brea tar pit fossil collection includes Juniperus (C3) wood specimens that 14C date between 7.7 and 55 thousand years (kyr) B.P., providing a constrained record of plant response for southern California during the last glacial period. Atmospheric CO2 concentration ([CO2]) ranged between 180 and 220 ppm during glacial periods, rose to approximately 280 ppm before the industrial period, and is currently approaching 380 ppm in the modern atmosphere. Here we report on delta13C of Juniperus wood cellulose, and show that glacial and modern trees were operating at similar leaf-intercellular [CO2](ci)/atmospheric [CO2](ca) values. As a result, glacial trees were operating at ci values much closer to the CO2-compensation point for C3 photosynthesis than modern trees, indicating that glacial trees were undergoing carbon starvation. In addition, we modeled relative humidity by using delta18O of cellulose from the same Juniperus specimens and found that glacial humidity was approximately 10% higher than that in modern times, indicating that differences in vapor-pressure deficits did not impose additional constrictions on ci/ca in the past. By scaling ancient ci values to plant growth by using modern relationships, we found evidence that C3 primary productivity was greatly diminished in southern California during the last glacial period.

SUBMITTER: Ward JK

PROVIDER: S-EPMC544040 | biostudies-literature | 2005 Jan

REPOSITORIES: biostudies-literature

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Carbon starvation in glacial trees recovered from the La Brea tar pits, southern California.

Ward Joy K JK Harris John M JM Cerling Thure E TE Wiedenhoeft Alex A Lott Michael J MJ Dearing Maria-Denise MD Coltrain Joan B JB Ehleringer James R JR

Proceedings of the National Academy of Sciences of the United States of America 20050110 3

The Rancho La Brea tar pit fossil collection includes Juniperus (C3) wood specimens that 14C date between 7.7 and 55 thousand years (kyr) B.P., providing a constrained record of plant response for southern California during the last glacial period. Atmospheric CO2 concentration ([CO2]) ranged between 180 and 220 ppm during glacial periods, rose to approximately 280 ppm before the industrial period, and is currently approaching 380 ppm in the modern atmosphere. Here we report on delta13C of Junip ...[more]

PMID: 15642948

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Project description:The Rancho La Brea Tar Pits is the world's richest and most important Late Pleistocene fossil locality and best renowned for numerous fossil mammals and birds excavated over the past century. Less researched are insects, even though these specimens frequently serve as the most valuable paleoenvironemental indicators due to their narrow climate restrictions and life cycles. Our goal was to examine fossil material that included insect-plant associations, and thus an even higher potential for significant paleoenviromental data. Micro-CT scans of two exceptionally preserved leafcutter bee nest cells from the Rancho La Brea Tar Pits in Los Angeles, California reveal intact pupae dated between ?23,000-40,000 radiocarbon years BP. Here identified as best matched to Megachile (Litomegachile) gentilis Cresson (Hymenoptera: Megachilidae) based on environmental niche models as well as morphometrics, the nest cells (LACMRLP 388E) document rare preservation and life-stage. The result of complex plant-insect interactions, they offer new insights into the environment of the Late Pleistocene in southern California. The remarkable preservation of the nest cells suggests they were assembled and nested in the ground where they were excavated. The four different types of dicotyledonous leaves used to construct the cells were likely collected in close proximity to the nest and infer a wooded or riparian habitat with sufficient pollen sources for larval provisions. LACMRLP 388E is the first record of fossil Megachile Latreille cells with pupae. Consequently, it provides a pre-modern age location for a Nearctic group, whose phylogenetic relationships and biogeographic history remain poorly understood. Megachile gentilis appears to respond to climate change as it has expanded its distribution across elevation gradients over time as estimated by habitat suitability comparisons between low and high elevations; it currently inhabits mesic habitats which occurred at a lower elevation during the Last Glacial Maximum ?21,000 years ago. Nevertheless, the broad ecological niche of M. gentilis appears to have remained stable.

Project description:Colorectal cancer (CRC) screening can reduce cancer deaths. However, screening and abnormal test follow-up rates are low among underserved populations. The screening rates of 19-58%, and rates of colonoscopy completion after abnormal stool tests of 18-57% in community health centers (CHC) systems are low. This highlights an opportunity to improve early detection and decrease burden of CRC in our region. Mailed outreach and navigation programs have been shown to increase colonoscopy completion rate. The next step is to understand how to best implement these programs in the community on a larger scale. To achieve this goal, the investigators propose a Hub-and-Spoke intervention combining centralized strategies to maximize CRC screening, follow-up, and referral-to-care. The investigators hypothesize that this intervention will be superior to usual care for increasing CRC screening, abnormal test follow-up, and referral-to-care. The investigators will conduct a randomized trial to determine effectiveness in: 1) improvement in proportion of individuals up-to-date with screening 3 years post implementation; 2) proportion with abnormal FIT who complete diagnostic colonoscopy within 6 months; and 3) proportion with CRC completing first treatment evaluation. The investigators will also evaluate the implementation, scalability, and sustainability of the multi-level implementation strategy. The intervention consists of: Mailed FIT and Reminders. Eligible individuals will receive an introductory letter describing the importance of CRC screening and noting that follow-up mail will include a FIT Kit. It will also be offered to patients who completed prior mailed FIT with normal test results. All materials will be in English and Spanish. Two weeks later, participants will receive a packet via mail containing the FIT kit, a one-page invitation inviting FIT completion and FIT instructions, a postage-paid envelope for return to the patient’s CHC, and COVID-19 message. For non-compliant individuals not returning the kit, a reminder phone call and text message will be delivered 2 weeks later. The investigators will track returned letters, individuals who are later found to be up-to date with screening, and those who decline screening. The CHC will provide care coordination for patients with an abnormal FIT result.

Dataset Information

Carbon starvation in glacial trees recovered from the La Brea tar pits, southern California.

Publications

Carbon starvation in glacial trees recovered from the La Brea tar pits, southern California.

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