Source and Accumulation of Soil Carbon along Catena Toposequences over 12,000 Years in Three Semi-Natural Miscanthus sinensis Grasslands in Japan

Miscanthus-dominated semi-natural grasslands in Japan appear to store considerable amounts of soil C. To estimate the long-term effect of Miscanthus vegetation on the accumulation of soil carbon by soil biota degradation in its native range, we measured total soil C from the surface to a 1.2 m depth along a catena toposequence in three annually burned grasslands in Japan: Kawatabi, Soni, and Aso. Soil C stock was estimated using a radiocarbon age and depth model, resulting in a net soil C accumulation rate in the soil. C4-plant contribution to soil C accumulation was further estimated by δ13C of soil C. The range of total soil C varied among the sites (i.e., Kawatabi: 379–638 Mg, Soni: 249–484, and Aso: 372–408 Mg C ha−1). Catena position was a significant factor at Kawatabi and Soni, where the toe slope soil C accumulation exceeded that of the summit. The soil C accumulation rate of the whole horizon in the grasslands, derived C mainly from C4 plant species, was 0.05 ± 0.02 (Average ± SE), 0.04 ± 0.00, and 0.24 ± 0.04 Mg C ha−1 yr−1 in Kawatabi, Soni, and Aso, respectively. Potential exists for long-term sequestration of C under M. sinensis, but the difference in the C accumulation rate can be influenced by the catena position and the amount of vegetation.

Isotopic Evidence for Sources of Dissolved Carbon and the Role of Organic Matter Respiration in the Fraser River Basin, Canada

Sources of dissolved and particulate carbon to the Fraser River system vary significantly in space and time. Tributaries in the northern interior of the basin consistently deliver higher concentrations of dissolved organic carbon (DOC) to the main stem than other tributaries. Based on samples collected near the Fraser River mouth throughout 2013, the radiocarbon age of DOC exported from the Fraser River does not change significantly across seasons despite a spike in DOC concentration during the freshet, suggesting modulation of heterogeneous upstream signals during transit through the river basin. Dissolved inorganic carbon (DIC) concentrations are highest in the Rocky Mountain headwater region where carbonate weathering is evident, but also in tributaries with high DOC concentrations, suggesting that DOC respiration may be responsible for a significant portion of DIC in this basin. Using an isotope and major ion mass balance approach to constrain the contributions of carbonate and silicate weathering and DOC respiration, we estimate that up to 29% of DIC is derived from DOC respiration in some parts of the Fraser River basin. Overall, these results indicate close coupling between the cycling of DOC and DIC, and that carbon is actively processed and transformed during transport through the river network.

MatCalib: a Matlab software package for Bayesian modeling of radiocarbon ages subject to temporal order constraints

<abstract> <p>Radiocarbon ages must be calibrated due to the remarkable fluctuations of the atmospheric radiocarbon level. The traditional method (e.g., Calib) does not make use of any constraint such as the temporal/stratigraphical ordering of the ages, thereby resulting in one or several large age ranges. Bayesian age modeling is advantageous over the traditional method in several aspects. First, it can provide precise age estimates by applying some constraints known <italic>a priori</italic>. Second, it may provide a timing of an archaeological feature or a geological event that is unable to be dated directly. Although several Bayesian age modeling frameworks have been developed, inexperienced users may need not only a more user-friendly environment for data entry and definition of their project-specific problem, but also a powerful post-processing tool for analyzing and visualizing the results. Here a hierarchical Bayesian model with a minimum level of structural complexity is presented. It provides users with a flexible and powerful framework to incorporate radiocarbon ages into a sequence along a one-dimensional continuum so that it best reveals their temporal order, thereby yielding a more precise timing. The accompanying Matlab software package not only complements the existing MatCal package designed to calibrate radiocarbon ages individually, but also serves as an alternative to the online tools of Bayesian radiocarbon age modeling such as OxCal and BCal.</p> </abstract>

Khao San Dam: The Archaeological Evidence of Burnt Rice Festival in Southern Thailand | ข้าวสารดำา: หลักฐานทางโบราณคดีเกี่ยวกับประเพณีการเผาข้าวในภาคใต้ของ ประเทศไทย

Recently in 2021the 11th office of the Fine Arts Department, Songkhla has reported their annual excavations in Trang Province that archaeologists have found some set of rice while excavation in process namely,1) Khao Kurum Archaeological Site, Huai Yod District and 2) Napala Archaeological Site, Muang District. The artifacts which were found associated with the rice grains on the habitation layer consisted of potsherds, animal bones, grindstone, beads, etc. The grains of rice are short and brown in colour which is examined as carbonized since the beginning at its first left. The primary examination by archaeologists has classified the rice of Napala Archaeological Site as short grain of probably Orysa sativa (Indica or Aus) rice. AMS Radiocarbon dating by Beta Analytic Testing Laboratory shows the AMS standard results and calibration dating of charred material measured radiocarbon age:1440±30BP. Because of their geographical location, both sites are incredibly located on one side of the hill slope, where they were suitable for habitat and plantation, especially tiny paddy fields and farms with sufficient water supply either small stream or well. The found rice, which now still grows uphill, probably called ‘Khao rai’ needs less water or no marsh. Comparative study of ethnographic “Atong” 1 of 12 sub-tribes of the “Garos” Tibeto-Burman in Meghalaya, India which originated slash-and-burnt socio-groups, have shown an interest in growing rice activity. According to their ritual ceremony for planting of paddy, other grain, and seeds takes place. There are many ritualistic offerings of rice such as (1) flattened rice by asking for permission to cultivate the land from the first harvested paddy in May. (2) After the harvesting in September or October, the 1st ceremony of the agricultural year is a thanksgiving ceremony to mark the end of a period of toil in the fields and harvesting of bumper crops, which is probably the most important festival of the Garos locally called “Maidan syla” meant to celebrate the after-harvested festival or burnt rice festival. Their 2nd ceremony is to revive the monsoon clouds. People throw cooked rice on the floor to symbolize hailstones. Noticing the rice, were probably the assemblage of “Khao San Dam” in many activities of these ceremonies, that is the archaeological evidence found in Khao Kurum and Napala Archaeological Sites. In the Southern part of Thailand, once the crops have already cultivated, people celebrate to welcome their outcrops most probably at the end of September to October and mark their end of plantation before the monsoon come. People prepare 4 main rice desserts put together with other necessity stuffs in the “hmrub” special large containers and donate to the ancestors through Buddhist ceremony. Though archaeological evidence shows that southern peninsular was where the migrants from the west especially India origins, who shared same habitat of hillslope, might brought their different traditions through both land trans-peninsular and sea routes then settled down inner western or eastern coast since prehistoric times. The beliefs in animism might belong to some other western migrants and with having “hmrub” is one of their unique cultural characteristic material and tradition remain. Once they settled down then converged to Buddhism, the ritual ceremony may be changed due to religion, but tradition remains the same today, that is, Bun Duean Sib on the 10th of the lunar month or September-October.

Fish otolith geochemistry, environmental conditions and human occupation at Lake Mungo, Australia

Fish otoliths from the Willandra Lakes Region World Heritage Area (south-western New South Wales, Australia) have been analysed for oxygen isotopes and trace elements using in situ techniques, and dated by radiocarbon. The study focused on the lunettes of Lake Mungo, an overflow lake that only filled during flooding events and emptied by evaporation, and Lake Mulurulu, which was part of the running Willandra Creek system. Samples were collected from two different contexts: from hearths directly associated with human activity, and isolated surface finds. AMS radiocarbon dating constrains the human activity documented by five different hearths to a time span of less than 240 years around 19,350 cal. BP. These hearths were constructed in aeolian sediments with alternating clay and sand layers, indicative of fluctuating lake levels and occasional drying out. The geochemistry of the otoliths confirms this scenario, with shifts in Sr/Ca and Ba/Ca marking the entry of the fish into Lake Mungo several years before their death, and a subsequent increase in the δ18O by ∼4‰ indicating increasing evaporation of the lake. During sustained lake-full conditions there are considerably fewer traces of human presence. It seems that the evaporating Lake Mungo attracted people to harvest fish that might have become sluggish through oxygen starvation in an increasingly saline water body (easy prey hypothesis). In contrast, surface finds have a much wider range in radiocarbon age as a result of reworking, and do not necessarily indicate evaporative conditions, as shown by comparison with otoliths from upstream Lake Mulurulu.

Palaeobiological evidence for Southern Hemisphere Younger Dryas and volcanogenic cold periods

Current consensus places a Southern Hemisphere post-glacial cooling episode earlier than the Younger Dryas in the Northern Hemisphere. New Zealand sequences of glacial moraines and speleothem isotopic data are generally interpreted as supporting the absence of a Southern Hemisphere Younger Dryas. Radiocarbon age series of habitat specialist moa (Aves: Dinornithiformes) show, however, that a sudden return to glacial climate in central New Zealand contemporary with the Younger Dryas. The cooling followed significant warming, not cooling, during the period of the Antarctic Cold Reversal. In addition, the moa sequence chronology also shows that the Oruanui (New Zealand) and Mt Takahe (Antarctica) volcanic eruptions were contemporary with abrupt cooling events in New Zealand. The independent high spatial and temporal resolution climate chronology reported here is contrary to an inter-hemispheric post-glacial climate see-saw model.

Deep in the Sierra Nevada critical zone: Saprock represents a large terrestrial organic carbon stock

Large uncertainty remains in the spatial distribution of deep soil organic carbon (OC) storage and how climate controls belowground OC. This research aims to quantify OC stocks, characterize soil OC age and chemical composition, and evaluate climatic impacts on OC storage from the soil surface through the deep critical zone to bedrock. These objectives were carried out at four sites along a bio-climosequence in the Sierra Nevada, California. On average, 74% of OC was stored below the A horizon, and up to 30% of OC was stored in saprock (friable weakly weathered bedrock). Radiocarbon, spectroscopic, and isotopic analyses revealed the coexistence of very old organic matter (OM) (mean radiocarbon age = 20,300 y BP) with relatively recent OM (mean radiocarbon age = 4,800 y BP) and highly decomposed organic compounds with relatively less decomposed material in deep soil and saprock. This co-mingling of OM suggests OC is prone to both active cycling and long-term protection from degradation. In addition to having direct effects on OC cycling, climate indirectly controls deep OC storage through its impact on the degree of regolith weathering (e.g. thickening). Although deep OC concentrations are low relative to soil, thick saprock represents a large, previously unrealized OC pool.

In situ cosmogenic ¹⁰Be in pyroxene with an application to surface exposure dating

<p>Cosmogenic nuclides are an important tool in quantifying many Earth-surface processes. Beryllium-10 (¹⁰Be) is commonly extracted out of the mineral quartz; however many landscapes lack quartz bearing rocks. In order to establish a new chronometer based on ¹⁰Be in pyroxene for use in New Zealand and Antarctica, it is necessary to verify cleaning protocols and determine a local production rate. In this study, I have tested and modified an existing pyroxene decontamination procedure in order to further develop the use of ¹⁰Be in pyroxene as a chronometer. This method successfully removes the meteoric component of ¹⁰Be in pyroxene, allowing only the concentration of in situ produced ¹⁰Be to be measured. Additionally, production rates for ¹⁰Be in pyroxene have been determined empirically for New Zealand using cross-calibration with measured ³He concentrations and an independent radiocarbon age of the Murimotu debris avalanche in the central North Island, New Zealand of 10.6 ± 1.1 ka. Theoretical ¹⁰Be pyroxene production rates were also determined, based on the composition of the Murimotu pyroxene. The best estimate for the 10Be pyroxene production rate is 3.4 ± 0.8 atoms g⁻¹ yr⁻¹ at sea-level high latitude, which was determined via cross-calibration with the radiocarbon age for the deposit. This work shows that production rates for ¹⁰Be in pyroxene are both empirically and theoretically 8-27% lower than in quartz. The ³He/¹⁰Be ratio in the Murimotu pyroxene is 34.5 ± 9.9; this is indistinguishable from global ³He-pyroxene/¹⁰Be-quartz production ratios. In a case study surface exposure ages were determined for bedrock samples and cobble erratics collected in a vertical transect on Mount Gran, Antarctica, by applying the aforementioned ¹⁰Be pyroxene decontamination procedure and radiocarbon derived production rates. A chronology for ice surface lowering was obtained for the adjacent Mackay Glacier, indicating the ice surface lowered approximately 60 m during a relatively rapid episode of thinning which occurred between ~13.5 ka and 11 ka. This thesis presents a successful test of decontamination procedures, new production rates, and an example application, showing the promise of ¹⁰Be in pyroxene as a chronometer. The development of ¹⁰Be in pyroxene allows environments without quartz-bearing rocks to be dated using this widely used nuclide. The pairing of ¹⁰Be with ³He in pyroxene would allow complex exposure histories to be determined, expanding the application.</p>