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Posts Tagged ‘June 2018’

The Science of Terroir

Terroir involves the complex interplay of climate, soil, geology, and viticulture, all of which influence the character and quality of a wine from a given grape variety, rootstock, and viticultural practice. Contrary to the assertions of some wine writers, the minerals and character of the soil cannot be tasted in the wine. Rather, it is their effect on the grape ripening process that gives certain wines a “sense of place”. Most important is water availability, which is a function of climate (rainfall and humidity) and soil water-holding capacity. The soil structure reflects the geologic history of a region and may have evolved over millions of years as influenced by faulting, weathering, and bedrock mineralogy. Far-field effects such as glaciation and resultant sea-level change can affect landscapes that are thousands of kilometers apart.

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The Chemical Precipitates of Henry Sorby

Henry Clifton Sorby (1826–1908) is best known to geologists for his pioneering use of the petrological microscope and for instigating the systematic study of fluid inclusions. He also introduced microscopy to many other areas of science. Sorby belongs to that great tradition of amateurs who have made substantial contributions to science. Being unhindered by the needs of funding bodies, Sorby’s research ranged widely and touched on many topics that are still current today.

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v14n3 People in the News

Barbara L. Dutrow, Adolphe G. Gueymard Professor of Geology at the Louisiana State University (USA), was elected to the Board of Governors of the Gemological Institute of America (GIA). Frank C. Hawthorne, Distinguished Professor at the University of Manitoba (Canada) was appointed a Companion of the Order of Canada on 29 December 2017.

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The Enduring Mystery of Australasian Tektites

Molten glass rained down from the sky over parts of Southeast Asia, Australia, Antarctica, and into the neighbouring ocean basins during the Pleistocene, about 790,000 years ago. These glass occurrences, long recognized to be remnants of melt formed during meteorite impact, are known as the Australasian tektites. Their distribution defines the largest of at least four known strewn fields across the globe, strewn fields being regions over which tektite glass are scattered from what are thought to be single-impact events. The three other big tektite strewn fields are associated with known source craters, including the Bosumtwi (1.07 Ma, Ghana), Ries (15 Ma, Germany), and Chesapeake Bay (35.5 Ma, USA) impact structures. At only 790,000 years old, the Australasian tektite strewn field is both the youngest and the largest known. Despite much effort, the source crater has yet to be discovered. The search to locate it represents something akin to a “holy grail” in impact cratering studies.

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v14n3 From the Editors

Geologists love their beer and wine. There is abundant proof of this statement if you have ever attended an international geoscience conference. Typically, included with an attendee’s registration packet received upon arrival at the conference are beer/wine tickets. Scientists may disperse through the day to attend talks, workshops, and poster sessions, but, late in the afternoons, kegs of beer and bottles of wine are rolled out and the scientists will quickly converge on the beer/wine stations. As the topic of this thematic issue of Elements is on wine, the question begs to be asked, where does all that wine originate?

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Remote Sensing Applications for Viticultural Terroir Analysis

With the rise of remotely piloted aircraft systems, increasing computing power and advances in image processing software, the opportunities for vineyard observations through remote sensing are increasing. Remote sensing and image analysis techniques that are becoming more available include object-based image analysis, spatiotemporal analysis, hyperspectral analysis, and topoclimatology. Each of these techniques are described and discussed as potential for development within a viticulture and terroir context. While remote sensing applications are well established at the smaller precision viticulture scale, the larger spatial scale of terroir analysis requires adaptation and new models of analysis.

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The Scale Dependence of Wine and Terroir: Examples from Coastal California and the Napa Valley (USA)

The physical parameters of terroir are scale dependent. At the regional scale, climate is paramount and relates to the grape varietals most suited to the setting. Intermediate factors include geologic setting, sun exposure, and topography, all of which influence grape quality and character. At the smaller scale, soil character and local climatic variation shape grape flavor and aroma. These notions are discussed in relation to four California (USA) wine regions: Sonoma County, Paso Robles, Santa Barbara County, and Napa Valley.

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Environmental and Viticultural Effects on Grape Composition and Wine Sensory Properties

The most important characteristics upon which wines are evaluated are the intensity and complexity of their flavors. Flavor describes the combined impression created by both the volatile compounds, which are responsible for wine aroma, and the nonvolatile components, which determine the taste sensation. Environmental factors (topography, soil, climate), termed terroir, influence the levels of grape metabolites related to wine organoleptic properties, i.e. properties that can be detected by the sense organs, such as taste, color, odor, and feel. However, modern vineyard management practices have the potential to modify a vine’s response to natural site influences and so modify the flavor of the resultant wine.

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The Climate Component of Terroir

The choice of a given winegrape variety planted in its ideal climate, together with favorable topography and physical soil characteristics, combine to create the potential to produce fine wine. The French term terroir embodies this potential as a holistic concept that relates to both environmental and cultural factors that together influence the grape growing to wine production continuum. While the landscape, geology, and soil strongly interact to influence a vine’s balance of nutrients and water, it is the climate that is critical because it is this that limits where winegrapes can be grown at both the global and local scale. Whereas winegrape varieties are grown in numerous climates worldwide, they ultimately have relatively narrow climate zones for optimum growth, productivity and quality. In many regions a changing climate has already altered some aspects of winegrape production with earlier and more rapid plant growth and changes to ripening profiles and wine styles. As such the connections between varieties and their ideal terroirs are bound to be altered even further in the future. Research on grapevine and rootstock genetics, alterations in vineyard management, and adjustments in winemaking are addressing these issues to hopefully reduce the wine industry’s vulnerability and increase its adaptive capacity to future changes in climate.

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Major Soil-Related Factors in Terroir Expression and Vineyard Siting

A “terroir” is a cultivated ecosystem in which the vine interacts with the soil and the climate. The soil influences vine phenology and grape ripening through soil temperature, water supply and mineral supply. Limited water supply to the vines is critical for reaching a suitable grape composition in order to produce high quality red wines. Soil nitrogen availability also plays a key role in terroir expression. Ideally, vineyards should be established in areas where soil temperature (relative to air temperature), soil water-holding capacity (relative to rainfall and potential evapotranspiration) and soil nitrogen availability are optimum for the type of wine to be produced. Terroir expression can also be optimized by choosing appropriate plant material and via vineyard floor management techniques.

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