Nutrient relations in coniferous forests

The environment controls physiological processes in plants and thus their growth. The question how forests will respond to global environmental changes is addressed with different approaches and using two coniferous tree species: Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) I have used the relationship (nitrogen productivity) between a plant's growth rate and the amount of nitrogen in the plant to analyse the growth response to temperature. Data on needle dry matter, production, and nitrogen content in needles from a wide range of climatic conditions were collected and needle nitrogen productivities were calculated. The result is that the nitrogen productivity (net carbon gain of a canopy) of conifers is not sensitive to temperature. Growth responses to temperature in conifers are therefore mediated by changes in nitrogen availability. I have used three Swedish forest experiments to study the long-term fate of N addition. The fertilisation increased tree biomass, more strongly for spruce than pine. Once fertilisation had ceased, the growth rates in all treatments in pine and spruce stands at Lisselbo and Stråsan converged towards similar levels. Chronic fertilisation with complete nutrient solution in pine stands at Jädraås resulted in long-term increase in production. Nitrogen budgets established 12 years (pine) and 7 years (spruce) after the last N addition show that the increases in N stocks in the pine stands were mainly in the soil. In contrast, in the spruce ecosystem trees accumulated most of the added N and the increase in the soil was restricted to the humus layer. In the pine ecosystem, large losses of added N (between 254 and 738 kg ha-1 out of 1040 kg ha-1 added as fertilizer) occurred, whereas in the spruce ecosystem more N was recovered than could be accounted for by inputs (between 250 and 591 kg ha-1). I have used humus and needle nutrients and site characteristic from 37 pine and 50 spruce stands from all over Sweden to analyze forest nutrient relations. Biologically controlled nutrients (C, N, P, S) are less variable and more correlated, but the biological control is not limited to only the covalently bound elements. Stoichiometric relations are not entirely rigid but are more constrained in needles than in humus. The use of nitrogen as a basis in stoichiometric relations may give stronger relations than the use of carbon

On minimal representation-infinite algebras

Over an algebraically closed field we classify all minimal representation-infinite algebras where the lattice of two-sided ideals is not distributive. As a consequence there are only finitely many isomorphism classes of minimal representation-infinite algebras in each dimension

Model theory of special subvarieties and Schanuel-type conjectures

We use the language and tools available in model theory to redefine and clarify the rather involved notion of a {\em special subvariety} known from the theory of Shimura varieties (mixed and pure)

Voting Blocs, Coalitions and Parties

In this paper I study the strategic implications of coalition formation in an assembly. A coalition forms a voting bloc to coordinate the voting behavior of its members, acting as a single player and affecting the policy outcome. I prove that there exist stable endogenous voting bloc structures and in an assembly with two parties I show how the incentives to form a bloc depend on the types of the agents, the sizes of the parties, and the rules the blocs use to aggregate their preferences. I also provide an empirical application of the model to the US Supreme Court and I show that justices face a strategic incentive to coalesce into voting blocs

Explaining decision-making in government: the neo-Durkheimian institutional framework

In understanding styles of political judgement in government decision-making, explanatory limitations of rational choice, prospect theoretic, historical institutional, groupthink, and other approaches suggest that there is space for developing other frameworks. This article argues that the neo-Durkheimian institutional theoretical framework deserves serious consideration. It shows that it offers a powerful causally explanatory framework for generating theories of decision-making in government which can be examined using historical comparative research designs. The value of the concept of a ‘thought style’ for understanding political judgement is demonstrated, and contrasted sharply with ideology. The theory argues that informal institutions explain thought styles. Well-known cases from the Cuban missile crisis, and the Wilson and Heath governments illustrate the argument. The article rebuts criticisms offered of the neo-Durkheimian institutional framework in the literature. Finally, it identifies recent developments and innovations in the approach that make it especially suited to explaining political judgement in government decision-makingThis work was supported by the Leverhulme Trust (grant number: F01374I