Precise Prediction for M_W in the MSSM

We present the currently most accurate evaluation of the W boson mass, M_W, in the Minimal Supersymmetric Standard Model (MSSM). The full complex phase dependence at the one-loop level, all available MSSM two-loop corrections as well as the full Standard Model result have been included. We analyse the impact of the different sectors of the MSSM at the one-loop level with a particular emphasis on the effect of the complex phases. We discuss the prediction for M_W based on all known higher-order contributions in representative MSSM scenarios. Furthermore we obtain an estimate of the remaining theoretical uncertainty from unknown higher-order corrections.Comment: 38 pages, 25 figures. Minor corrections, additional reference

Scaling ozone responses of forest trees to the ecosystem level in a changing climate

Many uncertainties remain regarding how climate change will alter the structure and function of forest ecosystems. At the Aspen FACE experiment in northern Wisconsin, we are attempting to understand how an aspen/birch/maple forest ecosystem responds to long-term exposure to elevated carbon dioxide (CO 2 ) and ozone (O 3 ), alone and in combination, from establishment onward. We examine how O 3 affects the flow of carbon through the ecosystem from the leaf level through to the roots and into the soil micro-organisms in present and future atmospheric CO 2 conditions. We provide evidence of adverse effects of O 3 , with or without co-occurring elevated CO 2 , that cascade through the entire ecosystem impacting complex trophic interactions and food webs on all three species in the study: trembling aspen ( Populus tremuloides Michx . ), paper birch ( Betula papyrifera Marsh), and sugar maple ( Acer saccharum Marsh). Interestingly, the negative effect of O 3 on the growth of sugar maple did not become evident until 3 years into the study. The negative effect of O 3 effect was most noticeable on paper birch trees growing under elevated CO 2 . Our results demonstrate the importance of long-term studies to detect subtle effects of atmospheric change and of the need for studies of interacting stresses whose responses could not be predicted by studies of single factors. In biologically complex forest ecosystems, effects at one scale can be very different from those at another scale. For scaling purposes, then, linking process with canopy level models is essential if O 3 impacts are to be accurately predicted. Finally, we describe how outputs from our long-term multispecies Aspen FACE experiment are being used to develop simple, coupled models to estimate productivity gain/loss from changing O 3 .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72464/1/j.1365-3040.2005.01362.x.pd

Assessing the future global impacts of ozone on vegetation.

Ozone is a major secondary air pollutant, the current concentrations of which have been shown to have significant adverse effects on crop yields, forest growth and species composition. In North America and Europe, emissions of ozone precursors are decreasing but in other regions of the world, especially Asia, where much less is known about its impacts, they are increasing rapidly. There is also evidence of an increase in global background ozone concentrations, which will lead to significant changes in global ozone exposure over this century, during which direct and indirect effects of other changes in the global atmosphere will also modify plant responses to ozone. This paper considers how far our current understanding of the mechanisms of ozone impacts, and the tools currently used for ozone risk assessment, are capable of evaluating the consequences of these changing global patterns of exposure to ozone. Risk assessment based on relationships between external concentration and plant response is inadequate for these new challenges. New models linking stomatal flux, and detoxification and repair processes, to carbon assimilation and allocation provide a more mechanistic basis for future risk assessments. However, there are a range of more complex secondary effects of ozone that are not considered in current risk assessment, and there is an urgent need to develop more holistic approaches linking the effects of ozone, climate, and nutrient and water availability, on individual plants, species interactions and ecosystem function