Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species' relative abundance will more rapidly advance our understanding of invasions.

Herbivores and nutrients control grassland plant diversity via light limitation

Human alterations to nutrient cycles1, 2 and herbivore communities3, 4, 5, 6, 7 are affecting global biodiversity dramatically2. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems8, 9. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.

Plant diversity predicts beta but not alpha diversity of soil microbes across grasslands worldwide

Aboveground–belowground interactions exert critical controls on the composition and function of terrestrial ecosystems, yet the fundamental relationships between plant diversity and soil microbial diversity remain elusive. Theory predicts predominantly positive associations but tests within single sites have shown variable relationships, and associations between plant and microbial diversity across broad spatial scales remain largely unexplored. We compared the diversity of plant, bacterial, archaeal and fungal communities in one hundred and forty-five 1 m2 plots across 25 temperate grassland sites from four continents. Across sites, the plant alpha diversity patterns were poorly related to those observed for any soil microbial group. However, plant beta diversity (compositional dissimilarity between sites) was significantly correlated with the beta diversity of bacterial and fungal communities, even after controlling for environmental factors. Thus, across a global range of temperate grasslands, plant diversity can predict patterns in the composition of soil microbial communities, but not patterns in alpha diversity.

Permanent shift: the topology of Didier Vermeiren's Cariatide à la Pierre

Photographic documentation of sculpture produces significant consequences for the way in which sculptural space is conceived. When viewed as discrete mediums the interaction of the photograph and its sculptural subject is always framed by notions of loss. However, when taken as a composite system, the sculpture-photograph proposes a new ontology of space. In place of the fixity of medium, we can observe a topology at play: a theory drawn from mathematics in which space is understood not as a static field but in terms of properties of connectedness, movement and differentiation. Refracted through the photographic medium, sculpture becomes not a field of fixed points in space, but rather as a fluid set of relations - a continuous sequence of multiple ‘surfaces’, a network of shifting views. This paper will develop a topological account of studio practice through an examination of the work of the contemporary Belgian sculptor Didier Vermeiren (b. 1951). Since the 1980s, Vermeiren has made extensive use of photography in his sculptural practice. By analysing a series of iterations of his work Cariatide à la Pierre (1997-1998), this paper proposes that Vermeiren’s use of photography reveals patterns of connection that expand and complicate the language of sculpture, while also emphasising the broader topology of the artist’s practice as a network of ‘backward glances’ to previous works from the artist’s oeuvre and the art-historical canon. In this context, photography is not simply a method of documentation, but rather a means of revealing the intrinsic condition of sculpture as medium shaped by dynamic patterns of connection and change. In Vermeiren’s work the sculpture-photograph, has a composite identity that exceeds straightforward categories of medium. In their place, we can observe a practice based upon the complex interactions of objects whose ontology is always underpinned by a certain contingency. It is in this fundamental mobility, that the topology of Vermeiren’s practice can be said to rest.

Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Exotic species dominate many communities; however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.

Francine and Jean-Pierre Durand at Aenny Catzenstein's 80th birthday; London Portraits Family

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Jean-Pierre Durand, Patrick Matthiesen, unidentified woman and Serge Donabedian working on a puzzle at Aenny's 80th birthday; London.

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Francine and Jean-Pierre Durand at Aenny Catzenstein's 80th birthday; London Portraits Family

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Jean-Pierre Durand, Patrick Matthiesen, unidentified woman and Serge Donabedian working on a puzzle at Aenny's 80th birthday; London.

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Conflits de norms de justice distributive dans les fusions entre égaux Le cas de BioM.rieux-Pierre Fabre

Les strictes fusions entre égaux constituent un phénomène très rare. Pourtant, de nombreux dirigeants communiquent sur l’aspect égalitaire des fusions et acquisitions qu’ils conçoivent. Dans cet article, les auteurs expliquent pourquoi les dirigeants <> leurs F&A en <> ; montrent en quoi le postulat égalitaire initial accroît la probabilité de conflits entre deux normes de justice distributive pourtant compl.mentaires : l’égalité et l’équité ; et illustrent leurs propos avec un cas spectaculaire : la fusion égalitaire, puis la separation des entreprises BioMérieux et Pierre Fabre. Paradoxalement, la simple formulation en termes égalitaire des F&A favorise la diffusion de sentiments d’injustice distributive, qui nuit in fine à la performance de l’opération.

Gehiago Pierre Urteren gramatikaren iturriez: Lilyren gramatika

[EN] Pierre Urte wrote Grammaire cantabrique circa 1714, when he was exiled in England. In this article we want to prove that the main source for Urte’s work was the socalled “Lily’s grammar”, which was the oficial grammar to learn Latin language in England from the 16th to the 19th century. The indentification of that source allows us to support the claim that Urte’s grammar must be included in the tradition of language teaching, as was already pointed out by Oyharçabal (1989). In this article, we first offer a brief history of Lily’s grammar. Then, we provide some clues in order to identify the exact edition used by Urte. Finally, in the main section of the article, we confront the two grammatical works; our aim is to ensure Urte’s debt to Lily’s grammar, and to show in detail the principal parts which Urte took from his source (mainly grammatical clasifications and examples).

El Musteriense de la cueva de Harregi en Aussurucq, Soule (Excavaciones: Pierre Roucher, 1954-1960)

[ES] La cueva de Harregi (Aussurucq, Pays de Soule), excavada por P. Boucher entre 1954 y 1960, contiene testimonios prehistóricos del Paleolítico medio, superior y Postpaleolítico. En este artículo se analizan las evidencias de fauna e industria lítica asimiladas al Paleolítico medio. Importantes alteraciones estratigráficas postdeposicionales modificaron la original posición topográfica de la mayor parte de los depósitos musterienses. La composición global del lote industrial y de la serie faunística recuerdan intensamente a los controlados en los niveles musterienses Cj y Cjr de la muy cercana cueva de Gatzarria. Ello hace, bien plantear la posibilidad de una antigua organización estratigráfica y arqueológica de los depósitos musterienses como la de Gatzarria, lamentablemente perturbada por serios procesos hídricos erosivos, bien contemplar el hecho de una secuencia diferente, propia y, en cierta forma, contradictoria con la dinámica reconocida en Gatzarria.

A função e natureza das convenções e hipóteses segundo o convencionalismo francês da virada do século XIX para o XX: relações entre ciência e metafísica nas obras de Henri Poincaré, Pierre Duhem e Édouard Le Roy

Nesse trabalho apresentamos a função e determinamos a natureza das convenções e hipóteses para os fundamentos científicos segundo a corrente convencionalista que surgiu na França na virada do século XIX para o XX, composta por Henri Poincaré, Pierre Duhem e Édouard Le Roy. Além disso, analisamos a relação que as convenções e hipóteses podem estabelecer com teses metafísicas através dos critérios utilizados pelos cientistas para determinar a preferência por certas teorias. Para isso, promovemos uma interpretação imanente das obras publicadas entre 1891 e 1905. Como resultado, revelamos que os autores, apesar de serem classificados como pertencentes a uma mesma corrente, não possuem apenas posições comuns, mas também divergências. Poincaré e Le Roy concordam que as convenções geométricas são escolhidas de acordo com o critério de conveniência. Contudo, eles discordam sobre o valor que a conveniência agrega ao conhecimento científico. Em relação aos fenômenos naturais, os três autores concordam que a realidade não pode ser descrita univocamente por um mesmo conjunto de convenções e hipóteses. Porém, Poincaré e Duhem acreditam que há critérios que tornam umas teorias mais satisfatórias que outras. Analisamos os critérios experimentais, racionais e axiológicos que justificam a satisfação dos cientistas com certas teorias e apontamos como estes critérios se relacionam com a metafísica. Concluímos que os convencionalistas, mesmo que cautelosamente e de modo implícito, buscaram se aproximar da metafísica com o intuito de justificar a própria atividade científica.

A mercantilização do meio ambiente na cidade de Cabo Frio a partir dos fundamentos de Pierre George

A presente pesquisa mostra a teoria de Pierre George, geógrafo francês que viveu e analisou o século XX. O autor produziu uma leitura crítica da realidade, a partir de um contexto com várias transformações espaciais, guerras, expansão da industrialização, desenvolvimento das políticas do meio ambiente, questões sociais, entre outros pontos. Pierre George analisa o meio ambiente relacionando com o sistema econômico e os fatores políticos, indicando a função importante do espaço o conceito geográfico central. A partir das décadas de 1960 e 1970, há no capitalismo o novo sistema verde, que promete cuidar da degradação ambiental, mas estrategicamente pretende continuar o modelo de desenvolvimento. Esta realidade será incorporada por várias cidades em países desenvolvidos e em países subdesenvolvidos, que usarão o meio ambiente como uma mercadoria. Nesta pesquisa veremos o exemplo de Cabo Frio, Rj, uma cidade turística desde a década de 1950, que utiliza o meio ambiente como uma mercadoria, explorando a praia, os espaços verdes e a lagoa. Então a cidade será um exemplo excelente para confirmar a análise de George