17,809 research outputs found

    Oak Persistence in Mediterranean Landscapes: The Combined Role of Management, Topography, and Wildfires

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    Mediterranean ecosystems have been shaped by a history of human and ecological disturbances. Understanding the dynamics of these social-ecological systems requires an understanding of how human and ecological factors interact. In this study, we assess the combined role of management practices and biophysical variables, i.e., wildfire and topography, to explain patterns of tree persistence in a cork oak (Quercus suber L.) landscape of southern Portugal. We used face-to-face interviews with landowners to identify the management practices and the incentives that motivated them. We used aerial photographs and a Geographic Information System (GIS) to classify vegetation patch-type transitions over a period of 45 years (1958-2002) and logistic regression to explain such changes based on management and biophysical factors. The best model explaining vegetation transitions leading to cork oak persistence in the landscape included both biophysical and management variables. Tree persistence was more likely to occur on steeper slopes, in the absence of wildfires, and in the absence of understory management. We identified ecological, ideological, and economical barriers that preclude oak persistence and that are important to consider in implementing efficient environmental policies for adequate conservation and reforestation programs of Mediterranean cork oak landscape

    Unequal Impact of Conservatism on Accrual Measures and Drivers: Implications for the Specification of Accrual Models

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    This study makes two main contributions to the literature. Firstly, it tests empirically the relative timeliness of accrual measures and earnings components used as explanatory variables in accrual models (“accrual drivers”) regarding the impact of conservatism. Secondly, taking into account the empirical evidence on such a timeliness, it discusses intuitively potential implications for the specification of (traditional) accrual models and the quality of discretionary accrual estimates. It concludes that common accrual models, as Jones (1991), are misspecified. They have a dependent variable (accruals) asymmetrically affected by conservatism, and one or more explanatory variables that are not affected, inducing a non-systematic measurement error in estimating discretionary accruals.accruals; accrual models; discretionary accruals; conservatism.

    Double vector meson production in the International Linear Collider

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    In this paper we study double vector meson production in γγ\gamma \gamma interactions at high energies and, using the color dipole picture, estimate the main observables which can be probed at the International Linear Collider (ILC). The total γ(Q12)+γ(Q22)V1+V2\gamma (Q_1^2) + \gamma (Q_2^2) \rightarrow V_1 + V_2 cross-sections for Vi=ρV_i = \rho, ϕ\phi, J/ψJ/\psi and Υ\Upsilon are computed and the energy and virtuality dependencies are studied in detail. Our results demonstrate that the experimental analysis of this process is feasible at the ILC and it can be useful to constrain the QCD dynamics at high energies.Comment: 11 pages, 8 figure
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