Hydrothermal sediments associated with a relict back-arc spreading center in the Shikoku Basin, recovered from the Nankai accretionary prism, Japan

The hemipelagic mudrocks of the Nankai accretionary prism, Japan, contain hydrothermal deposits associated with a relict spreading center in the Shikoku Basin. Initial work on core samples from Ocean Drilling Program site 808 found several samples with elevated concentrations of calcium, magnesium, iron and manganese, at depths of between 1060 and 1111 m below sea floor. However, the origin of these sediments was uncertain, due to a lack of data. There was no recorded evidence of whether these elevated concentrations were present throughout this interval of core, or if they were present as discrete layers with the background hemipelagic mudrocks in between. In the present study the core was resampled, and the sediments with anomalous chemical compositions were found to be present in discrete layers. This fact, along with a detailed interpretation of their geochemistry, has allowed them to be identified as hydrothermal sediments, associated with the relict spreading center in the Shikoku Basin. The lower (older) two layers display a chemical composition typical of umbers, while the upper (younger) two layers are metalliferous mudrocks typical of deposits found further from the spreading center.     

Conserving agricultural heritage systems through tourism: Exploration of two mountainous communities in China

Community plays an important role in the preservation of agricultural heritage system （AHS）. Recently, many AHS have been valorized as interesting resources for rural tourism. The expectations are that tourism development （TD） can be supportive for the conservation of AHS while creating benefits for local communities. In this study, two mountainous pilot villages （Longxian and Xiaohuang） in a global conservation project for traditional agricutural systems - Globally Important Agricultural Heritage Systems （GIAHS） were selected to identify the relationship between AHS conservation and TD. The study undertook in-depth interviews, and questionnaires of village residents and informal discussions with local villagers. A t-test and a linear regression model were implemented to explore the comparative dimensions of the two communities with different geographical location, economic situation, and stage of TD. The research found some similarities and differences in the two mountainous communities during AHS conservation and TD. Firstly, AHS are preservaed well in both villages unconsiously, while the residents in Xiaohuang value more highly the heritage elements than the respondents in Longxian, and the villagers in Xiaohuang are more worried about their heritage system; Secondly, both villages expect lots of benefits from TD and they clearly perceive more positive than negative impact from tourism and thus approve TD, while the hugedifferent perception on transportation and accessibility in the two villages reflects the bottleneck of TD in Xiaohuang village. At the same time, the respondents from Xiaohuang perceive more positive and fewer negative impact from tourism than the respondents from Longxian. Thirdly, the respondents in the two villages all show positive attitudes towards participation in tourism mostly motivated by the high income expectation. The main factors to determine the community perception in two villages were also analyzed based on the data process. A location-based coneeputal framework of AHS conservation in partnership with TD at community scale is proposed at the end of the paper. The dynamics of tourism development, that could enhance a better understanding of the complex relationship between conservation objectives and tourism development are discussed.     

Long-term impact of the proglacial lake Jökulsárlón on the flow velocity and stability of Breiðamerkurjökull glacier,Iceland

Proglacial lakes are becoming ubiquitous at the termini of many glaciers worldwide due to continued climate warming and glacier retreat, and such lakes have important consequences for the dynamics and future stability of these glaciers. In light of this, we quantified decadal changes in glacier velocity since 1991 using satellite remote sensing for Breiðamerkurjökull, a large lake-terminating glacier in Iceland. We investigated its frontal retreat, lake area change and ice surface elevation change, combined with bed topography data, to understand its recent rapid retreat and future stability. We observed highly spatially variable velocity change from 1991 to 2015, with a substantial increase in peak velocity observed at the terminus of the lake-terminating eastern arm from ~1.00 ± 0.36 m day⁻¹ in 1991 to 3.50 ± 0.25 m day⁻¹ in 2015, with mean velocities remaining elevated from 2008 onwards. This is in stark comparison to the predominately land-terminating arms, which saw no discernible change in their velocity over the same period. We also observed a substantial increase in the area of the main proglacial lake (Jökulsárlón) since 1982 of ~20 km², equating to an annual growth rate of 0.55 km² year⁻¹. Over the same period, the eastern arm retreated by ~3.50 km, which is significantly greater than the other arms. Such discrepancies between the different arms are due to the growth and, importantly, depth increase of Jökulsárlón, as the eastern arm has retreated into its ~300 m-deep reverse-sloping subglacial trough. We suggest that this growth in lake area, forced initially by rising air temperatures, combined with the increase in lake depth, triggered an increase in flow acceleration, leading to further rapid retreat and the initiation of a positive feedback mechanism. These findings may have important implications for how increased melt and calving forced by climate change will affect the future stability of large soft-bedded, reverse-sloped, subaqueous-terminating glaciers elsewhere. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

Testing the utility of structure‐from‐motion photogrammetry reconstructions using small unmanned aerial vehicles and ground photography to estimate the extent of upland soil erosion

Quantifying the extent of soil erosion at a fine spatial resolution can be time consuming and costly; however, proximal remote sensing approaches to collect topographic data present an emerging alternative for quantifying soil volumes lost via erosion. Herein we compare terrestrial laser scanning (TLS), and both unmanned aerial vehicle (UAV) and ground photography (GP) structure‐from‐motion (SfM) derived topography. We compare the cost‐effectiveness and accuracy of both SfM techniques to TLS for erosion gully surveying in upland landscapes, treating TLS as a benchmark. Further, we quantify volumetric soil loss estimates from upland gullies using digital surface models derived by each technique and subtracted from an interpolated pre‐erosion surface. Soil loss estimates from UAV and GP SfM reconstructions were comparable to those from TLS, whereby the slopes of the relationship between all three techniques were not significantly different from 1:1 line. Only for the TLS to GP comparison was the intercept significantly different from zero, showing that GP is more capable of measuring the volumes of very small erosion features. In terms of cost‐effectiveness in data collection and processing time, both UAV and GP were comparable with the TLS on a per‐site basis (13.4 and 8.2 person‐hours versus 13.4 for TLS); however, GP was less suitable for surveying larger areas (127 person‐hours per ha^?1 versus 4.5 for UAV and 3.9 for TLS). Annual repeat surveys using GP were capable of detecting mean vertical erosion change on peaty soils. These first published estimates of whole gully erosion rates (0.077 m a^?1) suggest that combined erosion rates on gully floors and walls are around three times the value of previous estimates, which largely characterize wind and rainsplash erosion of gully walls. Copyright © 2017 John Wiley & Sons, Ltd.     

全球重要农业文化遗产(GIAHS)保护与适应性管理(英文)

世界各地世代居住的农牧民,以多样化的自然资源为基础,通过因地制宜的生产实践活动,创造、形成并保持着许多独具特色的农业系统和景观。这些在本土知识和传统经验基础上所建立起来的农业文化遗产巧夺天工,充分反映了人类及其文化多样性和与自然环境之间深刻关系的演进历程。这些系统不仅维持并适应了具有全球重要意义的农业生物多样性,形成了丰富的本土知识体系,而且更为重要的是,还为人类持续提供了多样化的产品和服务,保障了食物安全和生计安全,提高了人们的生活质量。但是,许多这样的农业生产系统正面临着包括全球化在内的多种影响因素的威胁。2002年,联合国粮农组织发起了一个国际合作计划"全球重要农业文化遗产(GIAHS)保护与适应性管理"。这一全球性倡议旨在建立这些农业文化遗产及其有关的生物多样性、食物与生计安全、景观与文化的保护体系,并在世界范围内得到认可,实现动态保护和可持续管理。     

Quantification of Metals and Semimetals in Carbon‐Rich Rocks: A New Sequential Protocol Including Extraction from Humic Substances

We have developed a new sequential extraction technique that does not require complex procedures and is efficient in determining metal and semimetal contents of carbon‐rich rocks. Six geological reference materials (SBC‐1, SCHS‐1, SCo‐1, SDO‐1, SGR‐1b and SLg‐1) and an in‐house black shale (SH‐1) were selected to test the method, which consists of four main digestion steps involving: (a) dilute HCl acid; (b) NaOH; (c) aqua regia; and (d) hydrofluoric acid. Compared with traditional aqua regia + hydrofluoric acid attack, this new protocol recovers more of the moderately volatile elements during early extraction of humic substances. In addition when compared with reference values, those for most elements are in agreement within uncertainty. Furthermore, this new protocol reveals important information on the partitioning of elements; for instance, steps one and two indicate which elements are associated with carbonates and organic phases from fulvic and humic acid extractions, whereas step three provides results for which elements are associated with sulfide minerals and step four indicates which elements remained in the silicate and oxide phases.     

Oxygen sites in hydrous aluminosilicate glasses: the role of Al-O-Al and H2O

We describe here high-field ¹⁷O magic-angle-spinning (MAS) and triple-quantum MAS (3QMAS) NMR spectra for several alkali silicate and Na, K, and Ca aluminosilicate glasses containing up to 10 wt.% water. The H₂O site appears to have a large quadrupolar coupling constant, and its chemical shift increases from Na- to K- glasses, suggesting significant cation-H₂O interactions. In ¹⁷O one-pulse MAS and 3QMAS and ²⁷Al one-pulse NMR experiments, major differences were seen between spectra for anhydrous and hydrous calcium aluminosilicate glasses. The changes in the ¹⁷O MAS spectra can be explained by the addition of an H₂O peak and to the disappearance of an Al-O-Al peak from the ¹⁷O NMR spectrum for the hydrous glass. The ²⁷Al results are consistent with this interpretation.     

Direct application of compound-specific radiocarbon analysis of leaf waxes to establish lacustrine sediment chronology

This study demonstrates use of compound-specific radiocarbon analysis (CSRA) for dating Holocene lacustrine sediments from carbonate-hosted Ordy Pond, O‘ahu, Hawai‘i. Long-chain odd-numbered normal alkanes (n-alkanes), biomarkers characteristic of terrestrial higher plants, were ubiquitous in Ordy Pond sediments. The δ¹³C of individual n-alkanes ranged from −29.9 to −25.5‰, within the expected range for n-alkanes synthesized by land plants using the C₃ or C₄ carbon fixation pathway. The ¹⁴C ages of n-alkanes determined by CSRA showed remarkably good agreement with ¹⁴C dates of rare plant macrofossils obtained from nearby sedimentary horizons. In general, CSRA of n-alkanes successfully refined the age-control of the sediments. The sum of n-alkanes in each sample produced 70–170 μg of carbon (C), however, greater age errors were confirmed for samples containing less than 80 μg of C. The ¹⁴C age of n-alkanes from one particular sedimentary horizon was 4,155 years older than the value expected from the refined age-control, resulting in an apparent and arguable age discrepancy. Several lines of evidence suggest that this particular sample was contaminated by introduction of ¹⁴C-free C during preparative capillary gas chromatography. This study simultaneously highlighted the promising potential of CSRA for paleo-applications and the risks of contamination associated with micro-scale ¹⁴C measurement of individual organic compounds.