Unfortunately the author's the name was misspelt throughout this article and also on the contents page of issue 23 (2). The correct name should have read ‘Masaharu Arakawa’.

Cambridge University Press apologises unreservedly for any inconvenience or embarrassment caused by this error.

From the inception of its military campaign into Central Asia via the Gansu corridor, the Tang dynasty had to ensure the shipment of extensive military supplies to support the activities of its occupying armies north and south of the Tianshan Mountains. Since the government paid soldiers’ salaries and bought supplies using silk, the timely delivery of silk from central China was critical. Most of the silk was collected in the central provinces under the zuyongdiao 租庸調 tax system, whether as stipulated payments of tax textiles or cloth-paid-in-place-of-annual-corvée tax. All this silk had to be shipped to the Western Regions. This article examines where this silk was made, how it was shipped to the north-west and how the system changed over time.

The idea for this project was Helen Wang's. At the International Symposium of Ancient Coins and the Culture of the Silk Road, organised by the Shanghai Museum, in December 2006, she asked Rong Xinjiang and Valerie Hansen if they would be interested in working together on the theme of textiles as money on the Silk Road. Too often, money is assumed to mean metal coins, and the abstract concept of the Silk Road is used to evoke a somewhat ethereal east-meets-west context. While the idea of silk as money is not new to those who know Chinese history, it seemed that few people had really explored the mechanics of how textiles were used in this way.

Most economists and historians today conceive of money in narrow terms – probably because they have grown up in the modern world and are used to our system of coins, paper notes, cheques and credit cards. Although economic historians are generally aware that some earlier societies (in Africa, Scandinavia and elsewhere) used other items as money, they do not usually pay much attention to these examples. Few realise that the government of China, governing an empire of some 60 million people during the Tang dynasty (618–907), implemented a complex financial system that recognised grain, coins and textiles as money. The government received taxes in coin and in kind, produced to specific standards (specific widths and lengths of textiles) that would then be redistributed, being used for official salaries and military expenses among other expenditures. Although some of the surviving evidence comes from the Silk Road sites of Turfan, Dunhuang and Khotan in northwest China (where the dry climate has preserved many documents and some actual examples of tax textiles), this multicurrency system was in use throughout the entire empire during the seventh to tenth centuries. At the time, Tang China was possibly the largest economy in the world, rivalled only by the Abbasid Empire (751–1258).

Textiles, grain, coins; people living in the Silk Road oasis of Turfan, 160 km south-east of Urumqi in today's Xinjiang, used all three items as money between 273 and 769. The city of Gaochang (some 40 km east of today's Turfan) was one of the most important cities on the northern route around the Taklamakan Desert, and many of its inhabitants were buried in the adjacent Astana and Karakhoja graveyards. The region's dry climate has preserved an extensive group of paper documents dating to before, and after, the Tang conquest of the city in 640. The residents of Turfan buried their dead with shoes, belts, hats and clothing made from recycled paper with writing on it. These records offer an unparalleled glimpse of how people living along the Silk Road used textiles as currency.

Forest loss and degradation in the tropics contribute 6–17% of all greenhouse gas emissions. Protected areas cover 217.2 million ha (19.6%) of the world’s humid tropical forests and contain c. 70.3 petagrams of carbon (Pg C) in biomass and soil to 1 m depth. Between 2000 and 2005, we estimate that 1.75 million ha of forest were lost from protected areas in humid tropical forests, causing the emission of 0.25–0.33 Pg C. Protected areas lost about half as much carbon as the same area of unprotected forest. We estimate that the reduction of these carbon emissions from ongoing deforestation in protected sites in humid tropical forests could be valued at USD 6,200–7,400 million depending on the land use after clearance. This is > 1.5 times the estimated spending on protected area management in these regions. Improving management of protected areas to retain forest cover better may be an important, although certainly not sufficient, component of an overall strategy for reducing emissions from deforestation and forest degradation (REDD).

Embedded vortices in turbulent wall-bounded flow over a flat plate, generated by a passive rectangular vane-type vortex generator with variable angle β to the incoming flow in a low-Reynolds-number flow (Re = 2600 based on the inlet grid mesh size L = 0.039 m and free stream velocity U∞ = 1.0 ms−1), have been studied with respect to helical symmetry. The studies were carried out in a low-speed closed-circuit wind tunnel utilizing stereoscopic particle image velocimetry (SPIV). The vortices have been shown to possess helical symmetry, allowing the flow to be described in a simple fashion. Iso-contour maps of axial vorticity revealed a dominant primary vortex and a weaker secondary one for 20° ≤ β ≤ 40°. For angles outside this range, the helical symmetry was impaired due to the emergence of additional flow effects. A model describing the flow has been utilized, showing strong concurrence with the measurements, even though the model is decoupled from external flow processes that could perturb the helical symmetry. The pitch, the vortex core size, the circulation and the advection velocity of the vortex all vary linearly with the device angle β. This is important for flow control, since one thereby can determine the axial velocity induced by the helical vortex as well as the swirl redistributing the axial velocity component for a given device angle β. This also simplifies theoretical studies, e.g. to understand and predict the stability of the vortex and to model the flow numerically.

The West Antarctic Peninsula region is an important source of Antarctic krill (Euphausia superba) in the Southern Ocean. From 1980–2004 abundance and concentration of phytoplankton and zooplankton, krill reproductive and recruitment success and seasonal sea ice extent here were significantly correlated with the atmospheric Southern Oscillation Index and exhibited three- to five-year frequencies characteristic of El Niño–Southern Oscillation (ENSO) variability. This linkage was associated with movements of the Southern Antarctic Circumpolar Current Front and Boundary, a changing influence of Antarctic Circumpolar Current and Weddell Sea waters, and eastward versus westward flow and mixing processes that are consistent with forcing by the Antarctic Dipole high-latitude climate mode. Identification of hydrographic processes underlying ecosystem variability presented here were derived primarily from multi-disciplinary data collected during 1990–2004, a period with relatively stable year-to-year sea ice conditions. These results differ from the overwhelming importance of seasonal sea ice development previously established using 1980–1996 data, a period marked by a major decrease in sea ice from the Antarctic Peninsula region in the late 1980s. These newer results reveal the more subtle consequences of ENSO variability on biological responses. They highlight the necessity of internally consistent long-term multidisciplinary datasets for understanding ecosystem variability and ultimately for establishing well-founded ecosystem management. Furthermore, natural environmental variability associated with interannual- and decadal-scale changes in ENSO forcing must be considered when assessing impacts of climate warming in the Antarctic Peninsula–Weddell Sea region.

Historians of China agree that the Chinese economy underwent a period of dramatic growth—some call it a commercial revolution—between AD 600 and 1400. As is so often the case, they have located all the causes within China: improved strains of rice, new technologies of water control, and the expansion of the market system. This book challenges the received wisdom by highlighting an important, but neglected, dimension of these economic changes: the effects of foreign trade on the city of Ch'üan-chou (also spelled Quanzhou).