Productivity and forage quality of a phytodiverse semi-natural grassland under various management regimes

Grassland management experiment (GrassMan) was set up in 2008 on a permanent semi-natural grassland in the Solling uplands, Germany. The main research focus is on the ecosystem functioning of the phytodiverse grassland (e.g. productivity and forage quality, water and nutrient fluxes). The aim of our study was to analyse the effects of vegetation composition and functional diversity on productivity and forage quality of the semi-natural permanent grassland. Variation in sward composition was achieved by herbicide application and resulted in three sward types: control sward type (without herbicide application), monocot-reduced and dicot-reduced. Further management factors included different nutrient input levels (without fertilizer and 180-30-100 kg/ha of N-P-K per year) and use intensity (cut once or three times a year). Functional diversity was determined by estimation of the yield shares for each species in the species composition and their specific functional characteristics. Forage quality was analysed by near infrared spectroscopy (NIRS). While sward type influenced the forage quality, yield variation was explained mainly by the management regime

Counting Complexity for Reasoning in Abstract Argumentation

In this paper, we consider counting and projected model counting of extensions in abstract argumentation for various semantics. When asking for projected counts we are interested in counting the number of extensions of a given argumentation framework while multiple extensions that are identical when restricted to the projected arguments count as only one projected extension. We establish classical complexity results and parameterized complexity results when the problems are parameterized by treewidth of the undirected argumentation graph. To obtain upper bounds for counting projected extensions, we introduce novel algorithms that exploit small treewidth of the undirected argumentation graph of the input instance by dynamic programming (DP). Our algorithms run in time double or triple exponential in the treewidth depending on the considered semantics. Finally, we take the exponential time hypothesis (ETH) into account and establish lower bounds of bounded treewidth algorithms for counting extensions and projected extension.Comment: Extended version of a paper published at AAAI-1

Validation of Simulation: Patterns in the Social and Natural Sciences

In most cases, the meaning of computer simulation is strongly connected to the idea numerical calculations. A computer simulation is a numerical solution of a complex mathematical problem. Therefore, the problem of validation of its results should be only a problem of judging the underlying computational methods. However, it will be argued, that this is not the case. It is consensus in literature that validation constitutes one of the central epistemological problems of computer simulation methods. Especially in the case of simulations in the social sciences the answers given by many authors are not satisfactory. The following paper attempts to show how the characteristics of simulation, i.e. the imitation of a dynamic, constitute the problem of validation even in the case of the natural sciences and what consequences arise. Differences as well as common grounds between social and natural sciences will be discussed.Generative Mechanism, Imitation, Patterns, Simulation, Validation