Background: While drinking alcohol, one must choose between the immediate rewarding effects and the delayed reward of a healthier lifestyle. Individuals differ in their devaluation of a delayed reward based on the time required to receive it, i.e., delay discounting (DD). Previous studies have shown that adolescents discount more steeply than adults and that steeper DD is associated with heavier alcohol use in both groups. - Methods: In a large-scale longitudinal study, we investigated whether higher rates of DD are an antecedent or a consequence of alcohol use during adolescent development. As part of the IMAGEN project, 2220 adolescents completed the Monetary Choice Questionnaire as a DD measure, the Alcohol Use Disorders Identification Test, and the Timeline Follow Back interview at ages 14, 16, 18, and 22. Bivariate latent growth curve models were applied to investigate the relationship between DD and drinking. To explore the consequences of drinking, we computed the cumulative alcohol consumption and correlated it with the development of discounting. A subsample of 221 participants completed an intertemporal choice task (iTeCh) during functional magnetic resonance imaging at ages 14, 16, and 18. Repeated-measures ANOVA was used to differentiate between high-risk and low-risk drinkers on the development of neural processing during intertemporal choices. - Results: Overall, high rates of DD at age 14 predicted a greater increase in drinking over 8 years. In contrast, on average, moderate alcohol use did not affect DD from ages 14 to 22. Of note, we found indicators for less brain activity in top-down control areas during intertemporal choices in the participants who drank more. - Conclusions: Steep DD was shown to be a predictor rather than a consequence of alcohol use in low-level drinking adolescents. Important considerations for future longitudinal studies are the sampling strategies to be used and the reliability of the assessments.

The research of this thesis will focus on the performance of farm forestry trees in Mubende district, Uganda. In order to this, the research will help to fill the existing knowledge gap on the performance of farm forestry trees of east Africa specially Uganda. The conducted tree species are Markhamia lutea, Ficus natalensis, Mangifera indica, Artocarpus heterophyllus, Anitaris toxicaria, Persea americana, Albizia coriaria and Spathodea campanulata. The selection of the trees was mainly driven through the availability of age information. The trees were measured in height, age, DBH, length of commercial stem, diameter at specific height and visual observations e.g. occurrence and stem quality. To compare the performance of the conducted tree species a regression analysis with eight different functions was carried out for each tree species. The results are reproducible Stand- Height-Curves, height curves, DBH curves and curves for the single tree volume. The decision on the best curve was made on their biological plausibility and their statistical calculations. Additionally, the farmers of the trees were interviewed about their tree species for e.g. purposes of the tree, value of the wood and their own impressions on the growth of the tree species. The recommendation for the best applicable function is the Petterson function for the Stand-Height- Curve and the function of Richards for the height-, DBH- and single tree volume curve. Still these functions shouldn’t be used without comparison to other functions, especially because the used functions were developed for tree stand conditions and not specially for agroforestry conditions were the tree growth is in general higher. Additionally, an upscaling and prediction of the monetary tree values is made on the basis of the single tree volume curves and the interview results. The prediction of the farmers possible income through the cultivation of trees is made for Markhamia lutea, Ficus natalensis, Anitaris toxicaria and Albizia coriaria and assumes that 100 trees are planted on one hectare. Albizia coriaria 3.630 € achieves the highest possible extra income for the farmer followed by Ficus natalensis with 1.300 €, Anitaris toxicaria with 910€ and Markhamia lutea with 880 €. This thesis gives an example on the performance and possible monetary value of tree species in Mubende district, Uganda. Further investigation is needed to fill the knowledge gap in the performance of east African tree species and their values completely. Keywords: performance, tree growth, utilization, Uganda, East-Africa