Natural regeneration of broadleaved tree species in southern Sweden

The objective of the present thesis was to examine the effects of silvicultural treatments and seed dispersal from surrounding stands on the establishment of natural regeneration of broadleaved tree species in southern Sweden. Most of the broadleaved tree species that occur naturally in forests in southern Sweden were studied but birch (Betulapendula Ehrh.1 B. pi~besceizs Roth) was the most common species and present in equal numbers in all studies. The wind dispe.rsa1 of see.ds of se.ven species was studied and great variations were found. This could mainly be explained by differences in seed morphology. The effect of soil scarification was examined in all five studies and was generally found to be positive for the establishment of the studied broadleaved species. However, in some cases the scarification was not positive for the establishment. The reason for t l i s was hypothesised to be that the seed supply was limited, or an effect of large and/or animal-dispersed seeds. The effect of shelterwood w a s examined in three studies and was found to be positive for animal-dispersed species but negative for shade-intolerant species, although a sparse shelterwood can be used to rcgcncratc birch. Slash removal was included in onc study and found to be positive for thc cstnblishrncnt of birch. This thcsis showccl that regeneration trcatmcnts can be used to incrcasc the e.stablishnent of naturally regene.rated broadleaved tree seedlings, but the stand structure and species composition must be regulated with pre-commercial thinning. However, the effect of variations in seed production and seed dispersal must be closely examined from a time and a space perspective prior to any forecasts regarding the effects of regeneration trcatrn

Two extensions of Thurston's spectral theorem for surface diffeomorphisms

Thurston obtained a classification of individual surface homeomorphisms via the dynamics of the corresponding mapping class elements on Teichm\"uller space. In this paper we present certain extended versions of this, first, to random products of homeomorphisms and second, to holomorphic self-maps of Teichm\"uller spaces.Comment: 11 page

Management of wolf and lynx conflicts with human interests

In many areas viable populations of large carnivores are political goals. One of the most important factors in order to achieve viable large carnivore populations is human tolerance for presence of large carnivores. Thus, management of large carnivore populations in multi use landscapes will involve mitigating conflicts with human interests. In order to mitigate conflicts in a effective way, managers need tools for predicting likelihood of large carnivore occurrence, knowledge on which conflicts are considered as most important by humans in different areas, and the most efficient ways of mitigating the experienced problems. The aim of this thesis is to contribute to some parts of this toolbox for large carnivore managers. A habitat suitability model, with density of roads and built up areas as the most important variables, classified 79% of Scandinavia outside the reindeer husbandry area as suitable wolf habitat. Human tolerance towards wolves was lowest inside wolf territories and slowly increased amongst residents living up to 200 km from the nearest wolf territory. Human tolerance towards wolves may however be affected by mitigation measures such as subsidising electric fences in order to reduce the risk of wolf depredation on livestock. Management actions as subsidies for pro active measures or predator control should be targeting specific areas or individuals in order to be effective. It is also important to use the “right” management actions at the right time. Therefore it is, among other things, important to know if a reported bold wolf is acting in a way that most wolves would not, given the same circumstances. Wolves moved away from an approaching human on average at a distance of about 100 m. Wind velocity and wind direction influenced the distance heavily and humans may come as close to wolves as 17 meters before the wolves become aware of the human and react

Dynamics of Hilbert nonexpansive maps

In his work on the foundations of geometry, Hilbert observed that a formula which appeared in works by Beltrami, Cayley, and Klein, gives rise to a complete metric on any bounded convex domain. Some decades later, Garrett Birkhoff and Hans Samelson noted that this metric has interesting applications, when considering certain maps of convex cones that contract the metric. Such situations have since arisen in many contexts, pure and applied, and could be called nonlinear Perron-Frobenius theory. This note centers around one dynamical aspect of this theory.Comment: 10 pages. To appear in the Handbook of Hilbert Geometr

Building flat space-time from information exchange between quantum fluctuations

We consider a hypothesis in which classical space-time emerges from information exchange (interactions) between quantum fluctuations in the gravity theory. In this picture, a line element would arise as a statistical average of how frequently particles interact, through an individual rate $dt\sim 1/f_t$ and spatially interconnecting rates $dl\sim c/f$. The question is if space-time can be modelled consistently in this way. The ansatz would be opposite to the standard treatment of space-time as insensitive to altered physics at event horizons (disrupted propagation of information) but by extension relate to the connection of space-time to entanglement (interactions) through the gauge/gravity duality. We make a first, rough analysis of the implications this type of quantization would have on the classical structure of flat space-time, and of what would be required of the interactions. Seeing no obvious reason for why the origin would be unrealistic, we comment on expected effects in the presence of curvature.Comment: 22 pages. v3: extended introductio

A note on coherent orientations for exact Lagrangian cobordisms

Let $L \subset \mathbb R \times J^1(M)$ be a spin, exact Lagrangian cobordism in the symplectization of the 1-jet space of a smooth manifold $M$. Assume that $L$ has cylindrical Legendrian ends $\Lambda_\pm \subset J^1(M)$. It is well known that the Legendrian contact homology of $\Lambda_\pm$ can be defined with integer coefficients, via a signed count of pseudo-holomorphic disks in the cotangent bundle of $M$. It is also known that this count can be lifted to a mod 2 count of pseudo-holomorphic disks in the symplectization $\mathbb R \times J^1(M)$, and that $L$ induces a morphism between the $\mathbb Z_2$-valued DGA:s of the ends $\Lambda_\pm$ in a functorial way. We prove that this hold with integer coefficients as well. The proofs are built on the technique of orienting the moduli spaces of pseudo-holomorphic disks using capping operators at the Reeb chords. We give an expression for how the DGA:s change if we change the capping operators.Comment: 41 pages, final version, accepted for publication in Quantum Topology. More details have been added to some of the proof