1,360 research outputs found

    Functional ecology of the biological soil crust in semiarid SE Spain: sun and shade populations of Diploschistes diacapsis (Ach.) Lumbsch

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    The Tabernas badlands in semiarid south-east Spain is one of the driest regions in Europe with a mean annual precipitation of c. 240 mm. The landscape is deeply dissected, with canyons, ramblas and sparsely vegetated eroded badland slopes. The vegetation is predominantly a biological soil crust consisting of different types of lichen-rich communities, one of the more conspicuous being dominated by Diploschistes diacapsis (Ach.) Lumbsch. This lichen is mainly restricted to the north- facing slopes, where it forms extensive whitish carpets and probably plays an important role in preventing erosion of the slopes and allowing plant colonization. South-facing slopes are much more eroded and generally lack vegetation. %The photosynthetic performance of north (shade) and south-facing (sun) populations of D. diacapsis was studied to determine if these different populations showed any adaptations to the microclimatic conditions of their individual habitats. The response of CO2 exchange to light intensity, temperature and water content was measured under controlled conditions in the laboratory. Dry weight-based net photosynthetic rates were higher in the southern-exposed population but quantum efficiency, and light compensation points were similar. Thallus weight per unit area (LMA) was considerably higher for shade specimens but maximum water content and optimal water content were very similar and chlorophyll content on a dry weight basis was also similar. Chlorophyll content on an area basis was higher in the northern-exposed population and always much larger than those reported in other studies on the same species (up to 8 times larger) with the result that NP values on a chlorophyll basis were relatively low. The larger LMA meant that shade thalli stored more water per unit area which should ensure longer active periods than sun thalli. The results support a strategy pair of high NP and short active time versus low NP and long active time, both having been reported for other soil crust species. However, the visibly larger biomass of the shade D. diacapsis suggests that the lichen is at the limit of its adaptability in these habitats

    MSM/RD: Coupling Markov state models of molecular kinetics with reaction-diffusion simulations

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    Molecular dynamics (MD) simulations can model the interactions between macromolecules with high spatiotemporal resolution but at a high computational cost. By combining high-throughput MD with Markov state models (MSMs), it is now possible to obtain long-timescale behavior of small to intermediate biomolecules and complexes. To model the interactions of many molecules at large lengthscales, particle-based reaction-diffusion (RD) simulations are more suitable but lack molecular detail. Thus, coupling MSMs and RD simulations (MSM/RD) would be highly desirable, as they could efficiently produce simulations at large time- and lengthscales, while still conserving the characteristic features of the interactions observed at atomic detail. While such a coupling seems straightforward, fundamental questions are still open: Which definition of MSM states is suitable? Which protocol to merge and split RD particles in an association/dissociation reaction will conserve the correct bimolecular kinetics and thermodynamics? In this paper, we make the first step towards MSM/RD by laying out a general theory of coupling and proposing a first implementation for association/dissociation of a protein with a small ligand (A + B C). Applications on a toy model and CO diffusion into the heme cavity of myoglobin are reported

    Identification and Characterization of White Grape Varieties Autochthonous of aWarm Climate Region (Andalusia, Spain)

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    The high sensitivity of one of the most important crops in the world, such as vine (Vitis vinifera L.), to particular changes caused by the phenomena associated with global warming, is encouraging the wine industry to place value on grape varieties that are autochthonous to each production area. These are generally conserved in germplasm banks and may pose a useful tool to counteract the effects of climate change. In order to determine the actual resource that such varieties constitute, this research has carried out a genetic identification, a morphological characterization, and an analysis of the grape musts obtained from four autochthonous varieties (Cañocazo, Castellano, MantĂșo de Pilas, and Palomino Fino). This genetic analysis has allowed the identification of autochthonous varieties with different genotypes. However, all of them had similar phenotypic characteristics in terms of high hair density in adult leaves. With respect to the physicochemical composition of the musts, significant differences have been observed between the autochthonous varieties, with respect to the control variety of Palomino Fino. Nevertheless, all of them have exhibited an adequate physicochemical composition to produce quality white wines. For all of the above reasons, these local varieties should be considered suitable for cultivation in areas with warmer and drier climates, such as Andalusia (Spain)

    Elucidating General Equilibrium Multiplier Effects: A Differential Perspective

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    Expenditure multipliers are routinely used to evaluate the effectiveness of government spending. When interested in disaggregated effects, interindustry models provide the necessary tools to be able to look at very detailed sectorial results. These models are theoretically simple and empirically operational, which makes them easily implementable and therefore popular with policy makers. They miss, however, quite a bit of the interaction that takes place at the micro level. On the one hand, they ignore the role exerted by supply constraints in primary factors; on the other hand, they look at the world as though it is fully linear. We overcome these limitations by using an opposite Walrasian general equilibrium model to compute marginal multipliers. By using differential calculus, we also offer some insights regarding the “under-the-hood” circuits of influence

    Reverse Impact Assessment Using a Regional SAM

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    Unlike traditional impact analysis, that measures the influence of a sector, or a set of like sectors, on the overall economy, we present in this note a simple reverse procedure that attempts to quantify the impact of activity changes in the overall regional economy over a specific subset of firms. We apply the procedure to a specific enclave of the chemical and basic industry sectors, which has been and still is of special significance for the development of the region. Because we feel that interdependency effects should be adequately captured, we rely on a 1995 regional social accounting matrix (SAM) of Andalusia, Spain, to establish the empirical structural support for the analysis. We proceed by setting up a linear SAM model to obtain extended multipliers, then we decompose them in three categories of effects (direct, indirect, and induced) under different hypotheses about the classification of endogenous and exogenous sectors. The decomposed multipliers are then apportioned to measure and distinguish the effects on the economic enclave. The results are seen to be quite robust to the exogeneity assumptions

    Sensitivity of Simulation Results to Competing SAM Updates

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    Recently there has been a renewed research interest in the properties of non survey updates of input-output tables and social accounting matrices (SAM). Along with the venerable and well known scaling RAS method, several alternative new procedures related to entropy minimization and other metrics have been suggested, tested and used in the literature. Whether these procedures will eventually substitute or merely complement the RAS approach is still an open question without a definite answer. The performance of many of the updating procedures has been tested using some kind of proximity or closeness measure to a reference input-output table or SAM. The first goal of this paper, in contrast, is the proposal of checking the operational performance of updating mechanisms by way of comparing the simulation results that ensue from adopting alternative databases for calibration of a reference applied general equilibrium model. The second goal is to introduce a new updating procedure based on information retrieval principles. This new procedure is then compared as far as performance is concerned to two well-known updating approaches: RAS and cross-entropy. The rationale for the suggested cross validation is that the driving force for having more up to date databases is to be able to conduct more current, and hopefully more credible, policy analyses

    The Price Effects of Indirect Taxation in the Regional Economy of Andalusia

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    The goal of this paper is to use a regional social accounting matrix (SAM) to empirically study the price burden of indirect taxes in the regional economy of Andalusia, Spain, a developing region located in the south of the Iberian peninsula. The methodology we use is that of the well-known input-output subset of a SAM model. Adopting this approach we are able to capture the existent structural interdependence among productive sectors and we are able to evaluate the implicit weights and price elasticities of the different indirect taxes, as well as indicators of consumer’s welfare variations. The database used in the analysis is the SAMAND95 (Social Accounting Matrix of Andalusia, Spain, for 1995) developed by the authors. The main result of the paper is that taxes on labour use by firms carry the largest price burden of all indirect taxes, hence exerting a constraining role on the regions’ competitiveness
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