Ecological restoration of forests in Fennoscandia : Defining reference stand structures and immediate effects of restoration.

The first aim of this thesis was to explore the structural characteristics of near-natural forests and to quantify how human utilization has changed them. For this, we examined the stand characteristics in Norway spruce Picea abies (L.) Karst-dominated old-growth stands in northwestern Russia and in old Scots pine Pinus sylvestris L.-dominated stands in three regions from southern Finland to northwestern Russia. In the second study, we also compared stands with different degrees of human impact, from near-natural stands and stands selectively cut in the past to managed stands. Secondly, we used an experimental approach to study the short-term effects of different restorative treatments on forest structure and regeneration in managed Picea abies stands in southern Finland. Restorative treatments consisted of a partial cut combined with three levels of coarse woody debris retention, and a fire/no-fire treatment. In addition, we examined burned and unburned reference stands without cutting treatments. Results from near-natural Picea abies forests emphasize the dynamic character of old-growth forests, the variety of late-successional forest structures, and the fact that extended time periods are needed to attain certain late-successional stages with specific structural and habitat attributes, such as large-diameter deciduous trees and a variety of deadwood. The results from old Pinus sylvestris-dominated forests showed that human impact in the form of forest utilization and fire exclusion has strongly modified and reduced the structural complexity of stands. Consequently, small protected forest fragments in Finland may not serve as valid natural reference areas for forest restoration. However, results from the restoration experiment showed that early-successional natural stand characteristics can be restored to structurally impoverished managed Picea abies stands, despite a significant portion of wood volume being harvested. A variety of restoration methods is needed, due to differences in the condition of the forest when restoration is initiated and the variety of successional stages of forest structures after anthropogenic and natural disturbances. Keywords: dead wood, disturbance dynamic, fire, near-natural stand, rehabilitation, succession

Noncommutative Gravitation as a Gauge Theory of Twisted Poincaré Symmetry

Gravitaation kvanttiteorian muotoilu on ollut teoreettisten fyysikkojen tavoitteena kvanttimekaniikan synnystä lähtien. Kvanttimekaniikan soveltaminen korkean energian ilmiöihin yleisen suhteellisuusteorian viitekehyksessä johtaa aika-avaruuden koordinaattien operatiiviseen ei-kommutoivuuteen. Ei-kommutoivia aika-avaruuden geometrioita tavataan myös avointen säikeiden säieteorioiden tietyillä matalan energian rajoilla. Ei-kommutoivan aika-avaruuden gravitaatioteoria voisi olla yhteensopiva kvanttimekaniikan kanssa ja se voisi mahdollistaa erittäin lyhyiden etäisyyksien ja korkeiden energioiden prosessien ei-lokaaliksi uskotun fysiikan kuvauksen, sekä tuottaa yleisen suhteellisuusteorian kanssa yhtenevän teorian pitkillä etäisyyksillä. Tässä työssä tarkastelen gravitaatiota Poincarén symmetrian mittakenttäteoriana ja pyrin yleistämään tämän näkemyksen ei-kommutoiviin aika-avaruuksiin. Ensin esittelen Poincarén symmetrian keskeisen roolin relativistisessa fysiikassa ja sen kuinka klassinen gravitaatioteoria johdetaan Poincarén symmetrian mittakenttäteoriana kommutoivassa aika-avaruudessa. Jatkan esittelemällä ei-kommutoivan aika-avaruuden ja kvanttikenttäteorian muotoilun ei-kommutoivassa aika-avaruudessa. Mittasymmetrioiden lokaalin luonteen vuoksi tarkastelen huolellisesti mittakenttäteorioiden muotoilua ei-kommutoivassa aika-avaruudessa. Erityistä huomiota kiinnitetään näiden teorioiden vääristyneeseen Poincarén symmetriaan, joka on ei-kommutoivan aika-avaruuden omaama uudentyyppinen kvanttisymmetria. Seuraavaksi tarkastelen ei-kommutoivan gravitaatioteorian muotoilun ongelmia ja niihin kirjallisuudessa esitettyjä ratkaisuehdotuksia. Selitän kuinka kaikissa tähänastisissa lähestymistavoissa epäonnistutaan muotoilla kovarianssi yleisten koordinaattimunnosten suhteen, joka on yleisen suhteellisuusteorian kulmakivi. Lopuksi tutkin mahdollisuutta yleistää vääristynyt Poincarén symmetria lokaaliksi mittasymmetriaksi --- gravitaation ei-kommutoivan mittakenttäteorian saavuttamisen toivossa. Osoitan, että tällaista yleistystä ei voida saavuttaa vääristämällä Poincarén symmetriaa kovariantilla twist-elementillä. Näin ollen ei-kommutoivan gravitaation ja vääristyneen Poincarén symmetrian tutkimuksessa tulee jatkossa keskittyä muihin lähestymistapoihin.

Role of orbital symmetry in transition metal promoted ring opening reactions of methylenecyclopropanes and cyclobutenes

Transition metals catalyse a variety of organic reactions, of which the ring opening of strained ring organic molecules generated a lot of interest. Theoreticians predicted a metal orbital catalysed pathway, which involved concerted bond breaking and bond forming. On the other hand experimentalists were able to show that the reaction was not proceeding through a concerted pathway by intercepting the intermediates involved. There remained, however, two ring systems methylenecyclopropanes and cyclobutenes—whose reactions with metal complexes seemed to be of a concerted nature. An analysis of the reactions of different metal complexes with these ring systems and the theoretical predictions provide a rationale for understanding these reactions.

Evaluation of restoration of vegetation infested with cat's claw creeper vine (Dolichandra unguis-cati): soil seed bank response to herbicide and physical removal

Cat’s claw creeper vine, Dolichandra unguis-cati (L.) L.G.Lohmann (formerly known as Macfadyena unguis-cati (L.) A.H.Gentry), a Weed of National Significance (WoNS), is a structural woody parasite that is highly invasive along sensitive riparian corridors and native forests of coastal and inland eastern Australia. As part of evaluation of the impact of herbicide and mechanical/physical control techniques on the long-term reduction of biomass of the weed and expected return of native flora, we have set-up permanent vegetation plots in: (a) infested and now chemically/physically treated, (b) infested but untreated and (c) un-infested patches. The treatments were set up in both riparian and non-riparian habitats to document changes that occur in seed bank flora over a two-year post-treatment period. Response to treatment varied spatially and temporally. However, following chemical and physical removal treatments, treated patches exhibited lower seed bank abundance and diversity than infested and patches lacking the weed, but differences were not statistically significant. Thus it will be safe to say that spraying herbicides using the recommended rate does not undermine restoration efforts.

Fauna community trends during early restoration of alluvial open forest/woodland ecosystems on former agricultural land

Vertebrate fauna was studied over 10 years following revegetation of a Eucalyptus tereticornis ecosystem on former agricultural land. We compared four vegetation types: remnant forest, plantings of a mix of native tree species on cleared land, natural regeneration of partially cleared land after livestock removal, and cleared pasture land with scattered paddock trees managed for livestock production. Pasture differed significantly from remnant in both bird and nonbird fauna. Although 10 years of ecosystem restoration is relatively short term in the restoration process, in this time bird assemblages in plantings and natural regeneration had diverged significantly from pasture, but still differed significantly from remnant. After 10 years, 70 and 66% of the total vertebrate species found in remnant had been recorded in plantings and natural regeneration, respectively. Although the fauna assemblages within plantings and natural regeneration were tracking toward those of remnant, significant differences in fauna between plantings and natural regeneration indicated community development along different restoration pathways. Because natural regeneration contained more mature trees (dbh > 30 cm), native shrub species, and coarse woody debris than plantings from the beginning of the study, these features possibly encouraged different fauna to the revegetation areas from the outset. The ability of plantings and natural regeneration to transition to the remnant state will be governed by a number of factors that were significant in the analyses, including shrub cover, herbaceous biomass, tree hollows, time since fire, and landscape condition. Both active and passive restoration produced significant change from the cleared state in the short term.

Mechanistic Aspects of Shape Selection and Symmetry Breaking during Nanostructure Growth by Wet Chemical Methods

The control of shapes of nanocrystals is crucial for using them as building blocks for various applications. In this paper, we present a critical overview of the issues involved in shape-controlled synthesis of nanostructures. In particular, we focus on the mechanisms by which anisotropic structures of high-symmetry materials (fcc crystals, for instance) could be realized. Such structures require a symmetry-breaking mechanism to be operative that typically leads to selection of one of the facets/directions for growth over all the other symmetry-equivalent crystallographic facets. We show how this selection could arise for the growth of one-dimensional structures leading to ultrafine metal nanowires and for the case of two-dimensional nanostructures where the layer-by-layer growth takes place at low driving forces leading to plate-shaped structures. We illustrate morphology diagrams to predict the formation of two-dimensional structures during wet chemical synthesis. We show the generality of the method by extending it to predict the growth of plate-shaped inorganics produced by a precipitation reaction. Finally, we present the growth of crystals under high driving forces that can lead to the formation of porous structures with large surface areas.

Sterochemical studies on cyclic peptides-VIII. Conformational analysis of hydrogen bonded cyclohexaglycyl molecule with a centre of inversion symmetry

A study on the conformational aspects of cyclo-hexaglycyl having inversion symmetry has been made. The cyclic backbone has been assumed to have two internal 4→1 types of NH... O hydrogen bonds. This molecule has been found to take up two types of conformations designated asA* andB* having nearly the same energy values. The theoretical conformations have been compared with the conformations of cyclohexaglycyl hemihydrate observed in the crystal structure. Two molecules with an approximate inversion symmetry are close to the conformation of the typeB* and two other molecules with exact inversino symmetry correspond nearly to the typesB* andA*. comparison with the theoretically possible conformations of cyclohexaglycyl molecule with 2-fold symmetry has been made. The preference of inversion symmetry and preferred ranges ofψ for glycyl molecules is discussed.

An algebraic approach to the restoration of images

Two different matrix algorithms are described for the restoration of blurred pictures. These are illustrated by numerical examples.

Line removal and restoration of handwritten strokes

In document images, we often find printed lines over-lapping with hand written elements especially in case of signatures. Typical examples of such images are bank cheques and payment slips. Although the detection and removal of the horizontal lines has been addressed, the restoration of the handwritten area after removal of lines, persists to be a problem of interest. lit this paper, we propose a method for line removal and restoration of the erased areas of the handwritten elements. Subjective evaluation of the results have been conducted to analyze the effectiveness of the proposed method. The results are promising with an accuracy of 86.33%. The entire Process takes less than half a second for completion on a 2.4 GHz 512 MB RAM Pentium IV PC for a document image.

Possible high-temperature superconducting state with a d plus id pairing symmetry in doped graphene

Motivated by a suggestion in our earlier work [G. Baskaran, Phys. Rev. B 65, 212505 (2002)], we study electron correlation driven superconductivity in doped graphene where on-site correlations are believed to be of intermediate strength. Using an extensive variational Monte Carlo study of the repulsive Hubbard model and a correlated ground state wave function, we show that doped graphene supports a superconducting ground state with a d+id pairing symmetry. We estimate superconductivity reaching room temperatures at an optimal doping of about 15%-20%. Our work suggests that correlations can stabilize superconductivity even in systems with intermediate coupling.

Two elementary proofs of the Wigner theorem on symmetry in quantum mechanics

In quantum theory, symmetry has to be defined necessarily in terms of the family of unit rays, the state space. The theorem of Wigner asserts that a symmetry so defined at the level of rays can always be lifted into a linear unitary or an antilinear antiunitary operator acting on the underlying Hilbert space. We present two proofs of this theorem which are both elementary and economical. Central to our proofs is the recognition that a given Wigner symmetry can, by post-multiplication by a unitary symmetry, be taken into either the identity or complex conjugation. Our analysis often focuses on the behaviour of certain two-dimensional subspaces of the Hilbert space under the action of a given Wigner symmetry, but the relevance of this behaviour to the larger picture of the whole Hilbert space is made transparent at every stage.

Regeneration ecology and woody species diversity in the remnant natural forest at Wondo Genet, Ethiopia – Potential for landscape restoration

Regeneration ecology, diversity of native woody species and its potential for landscape restoration was studied in the remnant natural forest at the College of Forestry and Natural Resources at Wondo Genet, Ethiopia. The type of forest is Afromontane rainforest , with many valuable tree species like Aningeria adolfi-friederici, and it is an important provider of ecological, social and economical services for the population that lives in this area. The study contains two parts, natural regeneration studies (at the natural forest) and interviews with farmers in the nearby village of the remnant patch. The objective of the first part was to investigate the floristic composition, densitiy and regeneration profiles of native woody species in the forest, paying special attention to woody species that are considered the most relevant (socio-economic). The second part provided information on woody species preferred by the farmers and on multiple uses of the adjacent natural forest, it also provided information and analysed perceptions on forest degradation. Systematic plot sampling was used in the forest inventory. Twenty square plots of 20 x 20 m were assessed, with 38 identified woody species (the total number of species was 45), representing 26 families. Of these species 61% were trees, 13% shrubs, 11% lianas and 16% species that could have both life forms. An analysis of natural regeneration of five important tree species in the natural forest showed that Aningeria adolfi-friederici had the best regeneration results. An analysis of population structure (as determined by height classes) of two commercially important woody species in the forest, Aningeria adolfi-friederici and Podocarpus falcatus, showed a marked difference: Aningeria had a typical “reversed J” frequency distribution, while Podocarpus showed very low values in all height classes. Multi dimensional scaling (MDS) was used to map the sample plots according to their similarity in species composition, using the Sørensen quantitative index, coupled with indicator species analysis .Three groups were identified with respective indicator species: Group 1 – Adhatoda schimperiana, Group 2 – Olea hochstetteri , Group 3 – Acacia senegal and Aningeria adolfi-friederici. Thirty questionnaire interviews were conducted with farmers in the village of Gotu Onoma that use the nearby remant forest patch. Their tree preferences were exotic species such as Eucalyptus globulus for construction and fuelwood and Grevillea robusta for shade and fertility. Considering forest land degradation farmers were aware of the problem and suggested that the governmental institutions address the problem by planting more Eucalyptus globulus. The natural forest seemed to have moderate levels of disturbance and it was still floristically diverse. However, the low rate of natural regeneration of Podocarpus falcatus suggested that this species is threatened and must be a priority in conservation actions. Plantations and agroforestry seem to be possible solutions for rehabilitation of the surrounding degraded lands, thereby decreasing the existent pressure in the remnant natural forest.

Cubic and ultimate groups of complete symmetry

It is shown that the systems of definite actions described by polar and axial tensors of the second rank and their combinations during the superposition of their elements of complete symmetry with the elements of complete symmetry of the "grey" cube, result in 11 cubic crystallographical groups of complete symmetry. There are 35 ultimate groups (i.e., the groups having the axes of symmetry of infinite order) in complete symmetry of finite figures. 14 out of these groups are ultimate groups of symmetry of polar and axial tensors of the second rank and 24 are new groups. All these 24 ultimate groups are conventional groups since they cannot be presented by certain finite figures possessing the axes of symmetry {Mathematical expression}. Geometrical interpretation for some of the groups of complete symmetry is given. The connection between complete symmetry and physical properties of the crystals (electrical, magnetic and optical) is shown.