Litter mixture effects on tropical tree seedling growth - a greenhouse experiment

Decomposing litter provides critical nutrients for plants, particularly in nutrient-poor ecosystems such as tropical forests. We hypothesised that decomposing litter improves the performance of a variety of tropical tree seedlings, and that this litter effect varies depending on the species of litter present in litter mixtures. We addressed these hypotheses with a large pot experiment manipulating a range of different litter mixtures of contrasting quality and using seedlings of four tree species from the Amazonian forest of French Guiana. In contrast to our initial hypothesis, decomposing litter had either neutral or negative impacts on seedling growth, despite strongly different growth rates, biomass allocation patterns and leaf and root traits among tree species. Tree species varied in their responses to litter additions, which were further modified by species identity of the added litter. Our data show litter species-specific effects on growth, biomass allocation and leaf and root traits of tropical tree seedlings. These results suggest that a net nutrient release from decomposing litter does not necessarily improve tree seedling growth, even under nutrient-limiting conditions. In conclusion, litter layer composition may affect seedling establishment and recruitment success beyond litter-derived plant nutrient availability, which may contribute to tree species composition and dynamics in the studied tropical forest

The economic burden of depression in Switzerland

BACKGROUND: Despite the high prevalence of depression, information about the burden of this disease in Switzerland is scarce. A better knowledge of the costs of depression may provide important information for future national preventive programmes, optimizing cost-effective budgeting. The estimates of national costs may improve the public's awareness of depression and depression-related costs, breaking down the taboo of depression as an illness. OBJECTIVES: The aims of this study were to analyse the annual cost for different levels of depression and to investigate the annual economic burden of depression in Switzerland. METHODS: A retrospective, multicentre, non-interventional study in psychiatrist practices was carried out. Outpatients who had been diagnosed with depression in the last 3 years were included. Patient demographics and information on clinical characteristics and resource utilization in the first 12 months after diagnosis were collected. Costs analysis, subdivided into direct and indirect costs, was performed for three depression severity classes (mild, moderate and severe), according to the 17-item Hamilton Depression Rating Scale (HDRS-17). Costs were also extrapolated to a national level. Regression analysis was performed to control for factors that may have an impact on the cost of depression. RESULTS: A total of 556 patients were included. Hospitalization and hospitalization days were directly correlated with disease severity (p 3,561 for mild, 9,744 for moderate and 16,240 for severe depression. The mean indirect costs per person per year, mainly due to workdays lost, were 8,730 for mild, 12,675 for moderate and 16,669 for severe depression (year 2007/2008 values). Regression analysis showed that hospitalization days, psychiatrist visits in hospital, disability insurance, workdays lost and the HDRS-17 score were significantly correlated to the total costs. Extrapolation at a national level resulted in a total burden of about 8.1-8.3 billion per year. CONCLUSIONS: The burden of depression in Switzerland was estimated to be about 8 billion per year. The costs of depression were directly related to disease severity. However, since many cases of depression remain unreported and since this analysis only included individuals between 18 and 65 years of age, it is reasonable to suppose that the total burden of depression may be even higher