Ghost crab burrow density at Watamu Marine National Park: An indicator of the impact of urbanisation and associated disturbance?     

HFR Hereward  LK Gentle  ND Ray  RD Sluka 《African Journal of Marine Science》2017,39(1):129-133

Ghost crab (Ocypode species) burrow densities have previously been used as an indicator of anthropogenic impact. This study aimed to assess the burrow density of Ocypode species (O. ryderi and O. cordimanus) at four sites across Watamu Marine National Park, Kenya. Two sites were in front of hotel complexes (denoting a high degree of urbanisation), and two were in front of residential housing among coastal scrub (denoting a low degree of urbanisation). The findings reveal significantly higher burrow densities at sites in front of residential housing, which was the less developed area. This provides further evidence that Ocypode burrow densities can be used, where other methods would be impractical, to estimate the impact of some human activities along beach fronts, such as at Watamu Marine National Park.  相似文献   

A burst of outflows from the Serpens cloud core: wide-field submillimetre continuum, CO J=2–1 and optical observations     

C. J. Davis  H. E. Matthews  T. P. Ray  W. R. F. Dent  J. S. Richer 《Monthly notices of the Royal Astronomical Society》1999,309(1):141-152

Wide-field mapping of Serpens in submillimetre continuum emission and CO J =2–1 line emission is here complemented by optical imaging in [S  ii ] λλ 6716, 6731 line emission. Analysis of the 450- and 850-μm continuum data shows at least 10 separate sources, along with fainter diffuse background emission and filaments extending to the south and east of the core. These filaments describe 'cavity-like' structures that may have been shaped by the numerous outflows in the region. The dust opacity index, β , derived for the identifiable compact sources is of the order of 1.0±0.2, with dust temperatures in excess of 20 K. This value of β is somewhat lower than for typical class I YSOs; we suggest that the Serpens sources may be 'warm', late class 0 or early class I objects.
With the combined CO and optical data we also examine, on large scales, the outflows driven by the embedded sources in Serpens. In addition to a number of new Herbig–Haro flows (here denoted HH 455–460), a number of high-velocity CO lobes are observed; these extend radially outwards from the cluster of submillimetre sources in the core. A close association between the optical and molecular flows is also identified. The data suggest that many of the submillimetre sources power outflows. Collectively, the outflows traced in CO support the widely recognized correlation between source bolometric luminosity and outflow power, and imply a dynamical age for the whole protostellar cluster of ∼3×10⁴ yr. Notably, this is roughly equal to the proposed duration of the 'class 0' stage in protostellar evolution.  相似文献   

How important is groundwater availability and stream perenniality to riparian and floodplain tree growth?   总被引：1，自引：0，他引：1       下载免费PDF全文

Neil E. Pettit  Ray H. Froend 《水文研究》2018,32(10):1502-1514

Riparian vegetation is important for stream functioning and as a major landscape feature. For many riparian plants, shallow groundwater is an important source of water, particularly in areas where rainfall is low, either annually or seasonally, and when extended dry conditions prevail for all or part of the year. The nature of tree water relationships is highly complex. Therefore, we used multiple lines of evidence to determine the water sources used by the dominant tree species Eucalyptus camaldulensis (river red gum), growing in riparian and floodplain areas with varying depth to groundwater and stream perenniality. Dendrometer bands were used to measure diel, seasonal, and annual patterns of tree water use and growth. Water stable isotopes (δ²H and δ¹⁸O) in plant xylem, soil water, and groundwater were measured to determine spatial and temporal patterns in plant water source use. Our results indicated riparian trees located on relatively shallow groundwater had greater growth rates, larger diel responses in stem diameter, and were less reactive to extended dry periods, than trees in areas of deep groundwater. These results were supported by isotope analysis that suggested all trees used groundwater when soil water stores were depleted at the end of the dry season, and this was most pronounced for trees with shallow groundwater. Trees may experience more frequent periods of water deficit stress and undergo reduced productivity in scenarios where water table accessibility is reduced, such as drawdown from groundwater pumping activities or periods of reduced rainfall recharge. The ability of trees to adapt to changing groundwater conditions may depend on the speed of change, the local hydrologic and soil conditions as well as the species involved. Our results suggest that E. camaldulesis growing at our study site is capable of utilizing groundwater even to depths >10 m, and stream perenniality is likely to be a useful indicator of riparian tree use of groundwater.  相似文献   

Watershed systems science—A new paradigm to understand and govern the impact of human activities on the earth's surface in the Anthropocene     

Ray Ison  YongPing Wei 《中国科学:地球科学(英文版)》2017,60(12):2225-2227

正Recent scholars’work in Vol 58 Issue 1(2015)and Cheng and Li’s paper in Vol 58 Issue 7(2015)in Science China Earth Sciences propose development of"Watershed science"by"Bridging new advances in hydrological science with good management of river basins".An analysis of the language and key concepts used in the abstracts,titles and keywords of this set of 8 papers and an editorial reveals that‘Watershed’,‘River’,‘Science’and‘System’are the main  相似文献   

The rise of corporate retailing and the impacts on small-scale retailing: the survival strategies of Kirana stores and informal street vendors in Durgapur,India     

Nabati Ray  Graham Clarke  Paul Waley 《Singapore journal of tropical geography》2020,41(2):269-283

In many developing world economies in recent years, the state has been seen to encourage neoliberal economic expansion policies. This has involved both large-scale foreign corporations and sometimes large-scale domestic corporations. Many studies have discussed the new landscapes of economic hardship and the impacts on small businesses. The aim of this paper is to argue that the impacts on small traders are in fact more complex and varied than usually appears in the literature. The research was conducted in the industrial city of Durgapur in the Bardhaman district of West Bengal, India. First it is argued that the impact has been greatest on the ‘kirana’ owners, operating small convenience type stores with legalized trading arrangements and fixed premises. On the other hand, the street vendors (often unlicensed and having no fixed premises) seem not to be affected in terms of customer loss and indeed could be seen to be doing well against the backcloth of neoliberal expansion. In fact we argue that the growth in the number of street vendors provides as much of a threat to future livelihoods for traditional kirana owners as the growth of large corporations itself.  相似文献   

Noble gases and nitrogen in Raghunathpura (IIAB) and Nyaung (IIIAB) iron meteorites     

S. V. S. Murty  S. Ghosh  Dwijesh Ray 《Meteoritics & planetary science》2019,54(1):90-103

Noble gases and nitrogen were measured in two adjacent samples each from the Raghunathpura (IIAB) and the Nyaung (IIIAB) iron meteorite falls. Light noble gases in both the meteorites were of pure cosmogenic origin. Using (³He/⁴He)_c ratios and the production systematic of Ammon et al. ( 2009 ), we estimated the sample depth and meteoroid size for Nyaung (~8 cm depth in a ~15 cm radius object) and Raghunathpura (~12–14 cm depth in a ~25 cm object). We derived cosmic ray exposure ages of 1710 ± 256 Ma (for Nyaung, the highest reported so far for the IIIAB group) and 224 ± 34 Ma (for Raghunathpura). Variable amounts of trapped Kr and Xe were found in both meteorites. The phase Q‐like elemental ratio (⁸⁴Kr/¹³²Xe) suggests that the trapped component is of indigenous origin, and most likely hosted in the heterogeneously distributed micro‐inclusions of troilite/schreibersite. Trapped phase Q component is being reported for the first time, for a IIAB iron meteorite. Both meteorites showed light isotopic composition for nitrogen, and need at least two N components to explain the observed N isotopic systematic. Variable amounts of trapped noble gases and the presence of more than one N component suggest that the magmatic process that formed the parent body of these meteorites either could not completely homogenize or completely degas all the phases.  相似文献   

One centimeter-level observations of diurnal ocean tides from global monthly mean time-variable gravity fields     

Shin-Chan Han  Richard D. Ray  Scott B. Luthcke 《Journal of Geodesy》2010,84(12):715-729

A method of analyzing GRACE satellite-to-satellite ranging data is presented which accentuates signals from diurnal ocean tides and dampens signals from long-period non-tidal phenomena. We form a time series of differences between two independent monthly mean gravity solutions, one set computed from range-rate data along strictly ascending arcs and the other set computed from data along descending arcs. The solar and lunisolar diurnal tides having alias periods longer than a few months, such as K ₁, P ₁, and S ₁, present noticeable variations in the monthly ascending and descending ‘difference’ solutions, while the climate-related signals are largely cancelled. By computing tidal arguments evaluated along the actual GRACE orbits, we decompose and estimate residual tidal signals with respect to our adopted prior model GOT4.7. The adjustment in the tidal height is small yet significant, yielding maximum amplitudes of 4 cm mostly under the Antarctic ice shelves and ~1 cm in general at spatial scales of several hundred kilometer. Moreover, the results suggest there are possible 1-cm errors in the tide model even over oceans well-covered by decades of radar altimetry missions. Independent validation of such small adjustments covering wide areas, however, is difficult, particularly with limited point measurements such as tide gauge.  相似文献