Responses of arbuscular mycorrhizal fungi to long-term inorganic and organic nutrient addition in a lowland tropical forest

Improved understanding of the nutritional ecology of arbuscular mycorrhizal (AM) fungi is important in understanding how tropical forests maintain high productivity on low-fertility soils. Relatively little is known about how AM fungi will respond to changes in nutrient inputs in tropical forests, which hampers our ability to assess how forest productivity will be influenced by anthropogenic change. Here we assessed the influence of long-term inorganic and organic nutrient additions and nutrient depletion on AM fungi, using two adjacent experiments in a lowland tropical forest in Panama. We characterised AM fungal communities in soil and roots using 454-pyrosequencing, and quantified AM fungal abundance using microscopy and a lipid biomarker. Phosphorus and nitrogen addition reduced the abundance of AM fungi to a similar extent, but affected community composition in different ways. Nutrient depletion (removal of leaf litter) had a pronounced effect on AM fungal community composition, affecting nearly as many OTUs as phosphorus addition. The addition of nutrients in organic form (leaf litter) had little effect on any AM fungal parameter. Soil AM fungal communities responded more strongly to changes in nutrient availability than communities in roots. This suggests that the 'dual niches' of AM fungi in soil versus roots are structured to different degrees by abiotic environmental filters, and biotic filters imposed by the plant host. Our findings indicate that AM fungal communities are fine-tuned to nutrient regimes, and support future studies aiming to link AM fungal community dynamics with ecosystem function

Bit-rate-variable and order-switchable optical multiplexing of high-speed pseudorandom bit sequence using optical delays

We experimentally demonstrate high-speed optical pseudorandom bit sequence (PRBS) multiplexing with coarse and fine bit-rate tuning capability and a switchable order using optical delays. Data multiplexing of 80 Gbit/s and 160 Gbit/s is shown, each with a tunable rate using a conversion/dispersion-based continuously tunable optical delay and tunable PRBS order with large switchable fiber delays. A 7% bit-rate tunability, i.e., 80-85.6 Gbit/s and 160-171.2 Gbit/s, is shown for both 27 - 1 and 215 - 1 PRBS. The rf spectra before and after multiplexing are measured in each case and show a suppression ratio of >30 dB, exhibiting the expected PRBS spectral characteristics. © 2010 Optical Society of America

What does a cultural district actually do? Critically reappraising 15 years of cultural district policy in Italy

Culture-driven urban and regional strategies have grown since the 1980s in Europe and beyond. Countless initiatives for creative clusters, cultural quarters and culture-led urban policies have mushroomed since the mid-1990s. Being exceptionally rich and dense in cultural amenities and institutions, creative production and cultural consumption, Italy seemed to be the natural ground for such a cultural turn in policymaking. In fact, Italy has been the cradle for cultural districts (CDs) since the early 2000s, fostering both analytical and normative speculations and experiments. Despite this richness, a systematic study of CD policy implementation is lacking and several questions are still pending, in Italy as well as in other countries. For example, how diverse are the CD experiences being developed; and what are the aims and core activities, the urban and regional settings and development effects? This paper presents an original survey of 68 experimentations that were officially labelled as ‘cultural districts’ over the last 15 years in Italy: as such it constitutes the first attempt at a nation-wide comprehensive analysis of CD policy. Even though the major importance of CDs as an analytical tool is acknowledged, the evidence gathered in this study shows the fuzziness and inconsistencies in the implementation of CD policy in Italy. The analysis shows the uneven regional geography of CDs, stresses the large variety of contents and promoters and high rate of failure, and the limited degree of specialization and integration with cultural industries. The paper reconsiders critically the policy notion and practice of CDs in Italy and calls for further international scholarly and policy debates

Music consumption at the dawn of the music industry: the rise of a cultural fad

This paper discusses the extent to which sociodemographic characteristics of consumers and their past consumption are less effective in explaining the decision of purchasing a cultural good than the characteristics of the product itself, which allow for imitative behaviors and are at the basis of distinction. While the former approaches are well documented in the literature, the latter refers to Bourdieu’s idea of objectified cultural capital, which has been revisited and empirically explored. Because the various causal effects interact with each other, this paper tests a theoretical model which matches individual characteristics of the consumer with the properties of the cultural product. Specifically, we discussed the emergence of a new version of a cultural good, which is able to broaden the dimension of the market by gaining rapid success in its audience. This diffusion pattern is a quite rare event, but disruptive for the market and extremely profitable for the producer. The authors label this occurrence a disruptive cultural fad and try to understand the determinants of its adoption. The hypotheses of the model are tested on a unique dataset of microdata of purchasing transactions in Milan in the early nineteenth century, when the music by Gioachino Rossini emerged as a disruptive cultural fad at the dawn of the music industry. Results show that key features of a successful disruptive cultural fad are the role of some specific patterns of personal past consumption, the capabilities of generating positive network externalities in the consumption, and, surprisingly, the lack of negative ones due to any possible hip or snob effect