NO-TILL PROVIDES THE OPPORTUNITY TO MANAGE UNDERGROUND INTERACTIONS BETWEEN ARBUSCULAR MYCORRHIZAL FUNGI, WEEDS AND CROP PLANTS UNDER MEDITERRANEAN CONDITIONS

Early colonization of crop roots by arbuscular mycorrhiza (AM) is considered beneficial but its importance likely depends on the possible stresses faced by the host plant. Manganese toxicity is one such stress that AM can alleviate. Colonization initiated by extraradical mycelium (ERM) is faster than other sources of inoculum. No-till creates the possibility of encouraging inoculation via this source. At seeding time the ERM available for colonizing plants under no-till would have developed in association with previous crops or those weeds that germinated after the first autumn rain. However, the long, hot and dry summer under Mediterranean conditions might reduce the effectiveness of the ERM to colonize the new crop. The hypothesis that an intact ERM developed by weeds can affect the earlier AM colonization of wheat and alleviate Mn toxicity was tested in a pot experiment. Two mycotrophic (Ornithopus compressus L., Lolium rigidum Gaudin), and one non-mycotrophic (Silene galica L) weed species were grown for 7 weeks before being controlled with Glyphosate (the ERM remaining intact) or by mechanical disturbance (which also disrupted the ERM). Wheat was then planted and allowed to grow for 21 days. AM colonization, plant dry weight and shoot nutrient content were evaluated for both weeds and wheat. When an intact mycelium was present at the seeding of wheat (treatments with Ornithopus compressus and Lolium rigidum controlled by Glyphosate) there was a threefold increase in the AM colonization rate and growth of the crop compared with results for all the other treatments. The enhanced growth of wheat was associated with an alleviation of Mn toxicity, consistent with the hypothesis. However, there was a significant difference of the wheat growth after Ornithopus and Lolium (1.9 times), suggesting functional diversity within mycotrophic weeds and crops

Intergradação de hábitats de pequenos mamíferos não-voadores na paisagem retalhada do bioma Cerrado

The relevant literature on the community composition, population densities, habitat preference, and interspecific relations of small mammals in the Cerrado biome of central Brazil is surveyed, and their community structure in different habitats of the open savanna as well as in forested habitats, especially gallery forests, is analyzed. Small mammal communities differ along a gradient of natural habitats in the Cerrado landscape. There are habitat generalists occurring in more than three types of habitat (pan-habitat species) and habitat specialists, showing a high degree of fidelity to habitat. Most species are of the latter kind, displaying high habitat specificity. Habitat structure is the major factor determining small mammal communities within the Cerrado landscape. Community differences appear to be a function of local mosaic factors as well as differences among river basins, between high plateau forested habitats and lowland valley forests, or between moister open areas with soft soil and abundant grass versus very dry and rocky microhabitats.Contribuições consistentes para o conhecimento dos pequenos mamíferos do bioma Cerrado do Brasil central são examinadas, especificamente sobre composição de comunidades, densidade de populações e preferência de hábitat. A estrutura de comunidade de pequenos mamíferos é analisada em hábitats diferentes do Cerrado aberto bem como em hábitats florestados das matas de galeria. As comunidades de pequenos mamíferos diferem num gradiente de hábitats da paisagem do Cerrado. Há espécies hábitat-generalistas que ocorrem em mais de três tipos de hábitats (espécies pan-habitativas) e espécies hábitat-especialistas, restritas a um tipo de hábitat, que compreendem a maioria das formas, indicando alta especificidade. Estrutura de hábitat é o fator mais importante para determinar a comunidade de pequenos mamíferos no Cerrado. Essas diferenças parecem ser função das características locais dos mosaicos, como também diferenças entre bacias hidrográficas, ou ainda, diferenças entre hábitats florestados localizados nos platôs altos comparados com matas de vales em depressão, ou diferenças detectadas em porções de solos úmidos de Cerrado com abundância de gramíneas, comparados com microhábitats de solos secos e pedregosos

Global Ageing and Macroeconomic Consequences of Demographic Uncertainty in a Multi-regional Model.

In this paper, we investigate the impact of demographic uncertainty in a multi-regional general equilibrium, overlapping generations model (INGENUE 2). Specifically, we will consider the level of uncertainty in each of the ten major regions of the world, and their correlation across regions. In order to address these issues, we produce stochastic simulations of the world population for the ten regions until 2050. Then, we will analyse the economic consequences on a path by path basis over the period 2000-2050. These simulations allow us to assess the uncertainty induced into key macro-economic variables, the GDP growth rate and the world interest rate in particular, by uncertain future demographics. We show that the assumptions regarding interregional correlations of forecast errors are important in our model: they have a large impact on the uncertainty of the macroeconomic variables, and it appears that the macroeconomic adjustments can differ substantially if we consider independence or high correlation across the regions. In particular, the macroeconomic behaviour of the agents in the current account/saving problem differs significantly across regions according to the degree of interregional correlation.Computable General Equilibrium Models ; International capital flows ; Life cycle models and saving ; Demographic trends and forecasts.

Assumptions for long-term stochastic population forecasts in 18 European countries: Hypothèses de projections stochastiquesàlong terme des populations de 18 pays européens

The aim of the ‘Uncertain Population of Europe’(UPE) project was to compute long-term stochastic (probabilistic) population forecasts for 18 European countries. We developed a general methodology for constructing predictive distributions for fertility, mortality and migration. The assumptions underlying stochastic population forecasts can be assessed by analysing errors in past forecasts or model-based estimates of forecast errors, or by expert judgement. All three approaches have been used in the project. This article summarizes and discusses the results of the three approaches. It demonstrates how the—sometimes conflicting—results can be synthesized into a consistent set of assumptions about the expected levels and the uncertainty of total fertility rate, life expectancy at birth of men and women, and net migration for 18 European countries

Contaminação por mercúrio em sedimento e moluscos da Bacia do rio Bento Gomes, MT.

Os níveis de mercúrio total detectados no sedimento e tecidos moles de moluscos gastrópodos provenientes da bacia hidrográfica do rio Bento Gomes, embora baixos, mostraram indícios de contaminação. De um total de 69 amostras de sedimento analisadas, 26% apresentaram níveis de mercúrio total variando de 0,01 a 0,25 µg.g-1 de mercúrio (peso úmido). Os níveis de mercúrio obtidos em 54 amostras dos moluscos Ampullaria scalaris; A. canaliculata e Marisa planogira evidenciaram que 39% estavam contaminadas com níveis variando de 0,02 a 1,6 µg.g-1 de peso úmido. Estes resultados indicam que o mercúrio utilizado na extração de ouro de aluvião está atingindo o ambiente aquático e contaminado o sedimento e os organismos bentônicos desta área do Pantanal.bitstream/item/37304/1/BP58.pd

Ageing of a giant: a stochastic population forecast for China, 2006-2060

This paper presents a stochastic population forecast for China with a special emphasis on population ageing. The so-called scaled model for error was used to quantify the uncertainty attached to the population predictions. Data scarcity was a major problem in the specification of the expected error of the population forecast. Therefore, the error structures estimated for European countries were used with some modifications, taking into account the large size and heterogeneity of the Chinese population. The stochastic forecast confirms the expectation of extremely rapid population ageing during the first half of the twenty-first century in China. The old age dependency ratio (OADR) will certainly increase. Simply maintaining the current demographic rates (no international migration) would drive the OADR to 0.42 in 2060, four times the current level. Including expected declines in mortality and net outmigration in the projection would increase the median OADR in 2060 to 0.59, with a 80% prediction interval of [0.47, 0.75]. In particular, the oldest-old population will grow much faster than any other age group. This development has major implications for policy-making in China. Keywords: Stochastic population forecast Predictive distribution Uncertainty Scaled model for error China Population ageing Low fertility Mortality decline

Managing arbuscular mycorrhizal fungi for bioprotection: Mn toxicity

We investigated whether an intact extraradical mycelium (ERM) is more effective than other forms of propagule from indigenous arbuscular mycorrhizal fungi (AMF) in providing protection against stress to a host plant. The response of wheat (Triticum aestivum L.) to Mn toxicity was studied in a two-phase greenhouse experiment. In Phase 1, four Mn tolerant species from the natural vegetation, ranging from strongly mycotrophic to non- or weakly mycotrophic, were grown to develop different amounts of ERM. Wheat was then planted (Phase 2) with the ERM fragmented by sieving (Disturbed Treatment) or kept intact with no prior soil disturbance (Undisturbed Treatment). The growth of wheat was doubled by earlier and faster mycorrhizal colonization (AC) in the presence of an intact ERM at planting. There was a positive correlation between plant growth and the reduction of Mn and enhancement of P and S uptake into shoots. However, the growth of plants in undisturbed soil was significantly affected by the ERM developer species, which was not explained by differences in AC. Colonization starting from an intact ERM greatly enhanced the potential of AMF for protection against Mn toxicity. However, the degree of protection depended on the plant previously grown to develop the ERM, suggesting that there may be functional diversity within the ERM developed by mycotrophic plants of the natural vegetation

Interaction between Arbuscular Mycorrhizal Fungi and rhizobia on the growth of subclover under Mn toxicity: The role of Extraradical Mycelium.

When Arbuscular Mycorrhizal (AM) colonization started from an intact extraradical mycelium (ERM) its bioprotective effect on subclover was enhanced in comparison with other sources of inoculum. The presence in the soil of an intact ERM, developed previously on mycotrophic plants tolerant to Mn toxicity, resulted in the earlier colonization of subclover, reduced Mn concentration in the roots, improved development and activity of root nodules, and enhanced N acquisition