Browsing by Author "Reid, Rachel E. B."
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- Climate and vegetation and their impact on stable C and N isotope ratios in bat guanoReid, Rachel E. B.; Waples, James T.; Jensen, David A.; Edwards, Christine E.; Liu, Xinyi (Frontiers, 2022-09)Cave guano deposits represent a relatively untapped paleoecological archive that can provide information about past vegetation, climate, and bat diet over several millennia. Recent research suggests that carbon isotope values (delta C-13) measured in guano accumulations from insectivorous bats reflect the relative abundance of C-3 and C-4 plants on the landscape while nitrogen isotope values (delta N-15) may reflect precipitation amount. Together, these proxies can provide useful information for restoration practitioners seeking to understand how plant species composition has changed over time in relation to climate and land use. To better calibrate these proxies for use in restoration, we compared instrumental records of precipitation and satellite imagery of vegetation with isotope values measured in modern bat guano from Mary Lawson Cave, a large limestone cavern located in central Missouri. Mary Lawson Cave hosts a maternity colony of insectivorous gray bats (Myotis grisescens), and as such, contains significant guano accumulations. In the fall of 2018, we collected a 60 cm long guano core that dates to 1999 cal AD at its base. Guano core delta C-13 values decrease from the base toward the surface (from similar to-26 to -27 parts per thousand) whereas delta N-15 values increase toward the surface even after accounting for ammonia volatilization (from similar to 3 to 5 parts per thousand). Presently, the landscape around Mary Lawson Cave is dominated by a deciduous forest and pasture. Given that the land cover has changed very little over this period, the decline in delta C-13 values toward the present likely reflects a shift in land management on farms and/or increases in invasive C-3 species. Rainfall amounts from nearby Lebanon, Missouri, are significantly positively correlated with guano delta N-15 values, a relationship that is notably opposite that observed previously in soil and plants. We argue that heavy fertilizer application and significant grazing intensity could lead to the accumulation of large pools of excess labile nitrogen which would be vulnerable to leaching during precipitation events. The relationship between guano delta N-15 values and precipitation may differ for materials from less agriculturally impacted locations or periods and should be extended into the past with caution.
- A comprehensive investigation of Bronze Age human dietary strategies from different altitudinal environments in the Inner Asian Mountain CorridorWang, Wei; Liu, Yi; Duan, Futao; Zhang, Jie; Liu, Xinyi; Reid, Rachel E. B.; Zhang, Man; Dong, Weimiao; Wang, Yongqiang; Ruan, Qiurong; Li, Wenying; An, Cheng-Bang (2020-09)The early presence of crops from East Asia and Southwest Asia in the Inner Asian Mountain Corridor (IAMC) has drawn attention to the Bronze Age mountain archaeology of Central Asia. Namely, the Bronze Age diffusion and utilization of grains in this region remains unknown as contrasts and extremes characterize the territory in environmental terms, especially elevation. Researchers continue to reflect on how, during the second millennium BC, Bronze Age populations used new crops and local animal resources to adapt to different elevation environments of the IAMC. In this study, we analyzed the 41 latest stable carbon and nitrogen isotopic results from human and faunal bones from six Bronze Age sites in the IAMC, 261 previously published stable isotopic datasets, and 12 archaeobotanical and four zooarchaeological results to investigate the dietary strategies of populations from different elevation environments in the Bronze Age IAMC. The results show an altitudinal gradient in dietary choices among Bronze Age populations in the IAMC, with mixed C-4 and C-3 consumption at the low-mid elevations and notable C-3 consumption at the high elevations. Archaeobotanical and faunal remains also support these isotopic results. Our study further highlights that the differentiated dietary strategies adopted by the Bronze Age population in IAMC may have been the product of adaptation to local geographic environments. Social interaction may have also played a role in certain types of special dietary consumption.
- Evidence for a change in Milankovitch forcing caused by extraterrestrial events at Massignano, Italy, Eocene-Oligocene boundary GSSPReid, Rachel E. B.; Koeberl, Christian; Montanari, Alessandro; Bice, David (2009-04-01)High-resolution spectral analyses of four climate proxies from Massignano, Italy (Eocene-Oligocene boundary global stratotype section and point [GSSP]) indicate that the deposition of this rhythmically bedded sedimentary sequence was controlled by Milankovitch orbital cycles. An inverse relationship between the magnetic susceptibility record and the co-varied calcium carbonate, δ18O, and δ13C records is indicative of a climate model in which limestones represent dry/cold periods, while marly limestones represent warm/wet periods. Through pattern matching of band-pass fi ltered signals with the La2004 eccentricity curve, we propose an astrochronological calibration for this important time period. Constrained by three radioisotopically dated volcanic ashes and based on a band-pass version of eccentricity that exhibits expected amplitude modulations, our astrochronology yields a refi ned age for the Eocene-Oligocene boundary of 33.91 ± 0.05 Ma. Orbital forcing is less pronounced in the lower portion of the Massignano section (meter levels 0–15), which contains evidence of several impact events and a 2.2-m.y.-long comet/asteroid shower. We propose that substantial, nonperiodic climate alterations caused by this period of enhanced extraterrestrial activity mask the Milankovitch climate cycles. Possible mechanisms for the exaggeration of impact-related climatic changes include the ice-albedo feedback or the combined effect of impact-related atmospheric alterations with ongoing dust-particle loading associated with the comet/asteroid shower.
- Localized management of non-indigenous animal domesticates in Northwestern China during the Bronze AgeVaiglova, Petra; Reid, Rachel E. B.; Lightfoot, Emma; Birch, Suzanne E. Pilaar; Wang, Hui; Chen, Guoke; Li, Shuicheng; Jones, Martin; Liu, Xinyi (Springer, 2021-08-26)The movements of ancient crop and animal domesticates across prehistoric Eurasia are well-documented in the archaeological record. What is less well understood are the precise mechanisms that farmers and herders employed to incorporate newly introduced domesticates into their long-standing husbandry and culinary traditions. This paper presents stable isotope values (δ13C, δ15N) of humans, animals, and a small number of plants from the Hexi Corridor, a key region that facilitated the movement of ancient crops between Central and East Asia. The data show that the role of animal products in human diets was more significant than previously thought. In addition, the diets of domestic herbivores (sheep/goat, and cattle) suggest that these two groups of domesticates were managed in distinct ways in the two main ecozones of the Hexi Corridor: the drier Northwestern region and the wetter Southeastern region. Whereas sheep and goat diets are consistent with consumption of naturally available vegetation, cattle exhibit a higher input of C4 plants in places where these plants contributed little to the natural vegetation. This suggests that cattle consumed diets that were more influenced by human provisioning, and may therefore have been reared closer to the human settlements, than sheep and goats.
- Nitrate limitation in early Neoproterozoic oceans delayed the ecological rise of eukaryotesKang, Junyao; Gill, Benjamin C.; Reid, Rachel E. B.; Zhang, Feifei; Xiao, Shuhai (American Association for the Advancement of Science, 2023-03-23)The early Neoproterozoic Era witnessed the initial ecological rise of eukaryotes at ca. 800 Ma. To assess whether nitrate availability played an important role in this evolutionary event, we measured nitrogen isotope compositions (δ15N) of marine carbonates from the early Tonian (ca. 1000 Ma to ca. 800 Ma) Huaibei Group in North China. The data reported here fill a critical gap in the δ15N record and indicate nitrate limitation in early Neoproterozoic oceans. A compilation of Proterozoic sedimentary δ15N data reveals a stepwise increase in δ15N values at ~800 Ma. Box model simulations indicate that this stepwise increase likely represents a ~50% increase in marine nitrate availability. Limited nitrate availability in early Neoproterozoic oceans may have delayed the ecological rise of eukaryotes until ~800 Ma when increased nitrate supply, together with other environmental and ecological factors, may have contributed to the transition from prokaryote-dominant to eukaryote-dominant marine ecosystems.
- The prospects of poop: a review of past achievements and future possibilities in faecal isotope analysisReid, Rachel E. B.; Crowley, Brooke Erin; Haupt, Ryan J. (Wiley, 2023-12)What can the stable isotope values of human and animal faeces tell us? This often under-appreciated waste product is gaining recognition across a variety of disciplines. Faecal isotopes provide a means of monitoring diet, resource partitioning, landscape use, tracking nutrient inputs and cycling, and reconstructing past climate and environment. Here, we review what faeces are composed of, their temporal resolution, and how these factors may be impacted by digestive physiology and efficiency. As faeces are often used to explore diet, we clarify how isotopic offsets between diet and faeces can be calculated, as well as some differences among commonly used calculations that can lead to confusion. Generally, faecal carbon isotope (δ13C) values are lower than those of the diet, while faecal nitrogen isotope values (δ15N) values are higher than in the diet. However, there is considerable variability both within and among species. We explore the role of study design and how limitations stemming from a variety of factors can affect both the reliability and interpretability of faecal isotope data sets. Finally, we summarise the various ways in which faecal isotopes have been applied to date and provide some suggestions for future research. Despite remaining challenges, faecal isotope data are poised to continue to contribute meaningfully to a variety of fields.
- Review of ESA SYMP 7: A Dynamic Perspective on Ecosystem Restoration–Establishing Temporal Connectivity at the Intersection Between Paleoecology and Restoration EcologyReid, Rachel E. B.; McGuire, Jenny L.; Svenning, Jens‐Christian; Wingard, G. Lynn; Moreno‐Mateos, David (Wiley)