103 research outputs found
Leaf wax <i>n</i>-alkane distributions record ecological changes during the Younger Dryas at Trzechowskie paleolake (northern Poland) without temporal delay
While of higher plant origin, a specific source assignment of
sedimentary leaf wax n-alkanes remains difficult. In addition, it is
unknown how fast a changing catchment vegetation would be reflected in
sedimentary leaf wax archives. In particular, for a quantitative
interpretation of n-alkane C and H isotope ratios in terms of
paleohydrological and paleoecological changes, a better understanding of
transfer times and dominant sedimentary sources of leaf wax n-alkanes is
required.In this study we tested to what extent compositional changes in leaf wax
n-alkanes can be linked to known vegetation changes by comparison with
high-resolution palynological data from the same archive. We analyzed leaf
wax n-alkane concentrations and distributions in decadal resolution from a
sedimentary record from Trzechowskie paleolake (TRZ, northern Poland),
covering the Late Glacial to early Holocene (13 360–9940 yr BP). As
an additional source indicator of targeted n-alkanes, compound-specific carbon
isotopic data have been generated in lower time resolution. The results
indicated rapid responses of n-alkane distribution patterns coinciding with
major climatic and paleoecological transitions. We found a shift towards
higher average chain length (ACL) values at the Allerød–Younger Dryas (YD) transition between 12 680 and 12 600 yr BP, coevaled with a decreasing
contribution of arboreal pollen (mainly Pinus and Betula) and a subsequently higher
abundance of pollen derived from herbaceous plants (Poaceae, Cyperaceae,
Artemisia), shrubs, and dwarf shrubs (Juniperus and Salix). The termination of the YD was
characterized by a successive increase in n-alkane concentrations coinciding
with a sharp decrease in ACL values between 11 580 and 11 490 yr BP,
reflecting the expansion of woodland vegetation at the YD–Holocene
transition. A gradual reversal to longer chain lengths after 11 200 yr BP,
together with decreasing n-alkane concentrations, most likely reflects the
early Holocene vegetation succession with a decline of Betula.These results show that n-alkane distributions reflect vegetation changes
and that a fast (i.e., subdecadal) signal transfer occurred. However, our
data also indicate that a standard interpretation of directional changes
in biomarker ratios remains difficult. Instead, responses such as changes in
ACL need to be discussed in the context of other proxy data. In addition, we
find that organic geochemical data integrate different ecological
information compared to pollen, since some gymnosperm genera, such as
Pinus, produce only a very low amount of n-alkanes and for this reason their
contribution may be largely absent from biomarker records. Our results
demonstrate that a combination of palynological and n-alkane data can be used
to infer the major sedimentary leaf wax sources and constrain leaf wax
transport times from the plant source to the sedimentary sink and thus pave
the way towards quantitative interpretation of compound-specific hydrogen
isotope ratios for paleohydrological reconstructions.</p
Climate change and the rise of the central Asian Silk Roads
The final centuries BCE (Before Common Era) saw the main focus of trade between the Far East and Europe switch from the so called Northern Route across the Asian steppes to the classical silk roads. The cities across central Asia flourished and grew in size and importance. While clearly there were political, economic and cultural drivers for these changes, there may also have been a role for changes in climate in this relatively arid region of Asia. Analysis of a new ensemble of snapshot global climate model simulations, run every 250 years over the last 6000 years, allows us to assess the long term climatological changes seen across the central Asian arid region through which the classical Silk Roads run. While the climate is comparatively stable through the Holocene, the fluctuations seen in these simulations match significant cultural developments in the region. From 1500 BCE the deterioration of climate from a transient precipitation peak, along with technological development and the immigration of Aryan nomads, drove a shift towards urbanization and probably irrigation, culminating in the founding of the major cities of Bukhara and Samarkand around 700–500 BCE. Between 1000 and 250 BCE the modelled precipitation in the central Asian arid region undergoes a transition towards wetter climates. The changes in the Western Disturbances, which is the key weather system for central Asian precipitation, provides 10% more precipitation and the increased hydrological resources may provide the climatological foundation for the golden era of Silk Road trade
In search of tools for the use of Country-Image (CI) in the brand
Existing country image (CI) literature tends to focus on consumer behaviour. In contrast, this paper approaches CI from the point of view of the firm. In doing so, it seeks to identify the means by which international companies associate a brand with a specific country of origin in order to build brand values. In particular, it looks at the use of CI cues in brand strategies. The
paper is based on exploratory research comprising a case study of two contrasting companies from the cosmetics industry, Natura, a domestic company, and the French-owned L’Occitane, both of which draw on images of Brazil to build their brands. Specific elements of CI used in branding are identified, and the extent to which the use of these differs depending on the
origin of the owning company is explored. The cases suggest that CI can be exploited in different contexts. Through analysis of the elements used by both companies to build strong brands associated with the Brazilian CI—Natura Cosméticos and L’Occitane au Brésil—six tools are identified that can be combined by firms to deliver brand values, derived from any country, through the use of CI
Measuring the Degree of Corporate Social Media Use.
This article aims to provide a model with which to measure the degree of corporate social media use or, in other words, the extent to which companies are exploiting the potentialities of single or multiple social media platforms. This is, however, explicitly different from using metrics to assess the success of social media activities, as it is purely measuring how intensively a pre-defined group of social media is utilized, taking into account the frequency of social media activity by the brand as well as the related user reactions. The degree of corporate social media use helps companies and market researchers analyze single brands or companies and compare them with other brands, competitors, or industry averages. The degree of corporate social media use is a useful indicator which should be combined with social media metrics in order to draw better conclusions about where to increase or intensify social media activities
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