Ecology and conservation of bryophytes and lichens on Fagus sylvatica

Environmental factors related to the occurrence of epiphytic bryophytes and lichens were examined in beech (Fagus sylvatica) forests in the Province of Halland, Sweden. Patterns in species composition and species number at different temporal and spatial scales were analyzed with emphasis on species of conservation concern (i.e. red-listed and indicator species). (I) At stand level, the availability of substrate, a high stand age and forest continuity were the most important factors explaining high species number of epiphytes of conservation concern. The difference in species number between stands with and without forest continuity was probably related to the presence of old trees and the time available for species colonization. (II) Within stands, plots containing old trees, at the base of slopes and with low recent forestry impact had the highest species number. At tree level, age, size and moss cover were primary factors in explaining both species number and species composition of all species. Red-listed lichens were associated with damaged beech trees older than 180 years, whereas the few red-listed bryophytes were also recorded on younger stems in dense stands. (III) The vertical distribution of epiphytes, recorded on newly fallen beech stems, could also be related to tree age. Some red-listed lichens were recorded only from above 2 m in height on trees older than 250 years. The presence of any species of conservation concern at 2-5 m height on standing living beech trees correlated positively to moss cover and bark structure, which in turn was dependent on tree age. (IV) The effect of bark and tree characteristics on species occurrence was studied. It was found that the combination of high bark pH, high tree age and damaged stem best explained the number of species of conservation concern. The link between old beech trees and high bark pH was partly explained by a positive effect of tree age on stemflow pH. (V) At microhabitat level, the type of stem damage rot hole was found to positively influence bark pH and the occurrence of species of conservation concern. Old and slow-growing trees with rot holes are, however, often removed from managed beech forests. A spatial separation between managed and retention areas is therefore recommended in shelterwood forestry

Adoption of Soil Conservation Practices in Olive Groves: The Case of Spanish Mountainous Areas

This paper presents some results from a survey carried out in 2004 among 223 olive tree farmers from mountainous areas in the Spanish Southern provinces of Granada and Jaen regarding the adoption of soil conservation and management practices. Olive tree groves in mountainous areas are subject to a high risk of soil erosion and have to incur in higher costs of soil conservation. This results in greater difficulties to comply with cross-compliance and to benefit from agri-environmental schemes. Our main objectives are to analyse the current level of adoption of soil conservation practices and to analyse which socio-economic and institutional factors determine such adoption. Three Probit models are estimated. Dependant variables are three different soil conservation practices, namely tillage following contour lines, maintenance of terraces with stonewalls, and non-tillage with weedicides.olive groves, soil conservation, technology adoption, Resource /Energy Economics and Policy, Q12, Q24,

Adoption of Soil Erosion Control Practices in Southern Spain Olive Groves

This paper presents results from a survey carried out in 2005 among 147 olive tree farmers from the Alto Genil River Basin in Southern Spain regarding the adoption of soil conservation and management practices. Olive tree groves in South-eastern Spain's mountainous areas are subject to a high risk of soil erosion and have to incur in high costs of soil conservation. This results in great difficulties to comply with cross-compliance and to benefit from agri-environmental schemes. Our main objectives are to analyse the current level of adoption of soil conservation practices and to analyse which socio-economic and institutional factors determine such adoption. Three Probit models are estimated. Dependant variables are three different soil conservation practices, namely tillage following contour lines, maintaining the rests of pruning on the ground, and non-tillage with weedicides.olive groves, soil erosion, soil conservation, cross compliance, Crop Production/Industries, Q12, Q24,

Assembling the Tree of Life in Europe (AToLE)

A network of scientists under the umbrella of 'Assembling the Tree of Life in Europe (AToLE)' seeks funding under the FP7-Theme: Cooperation - Environment (including Climate Change and Biodiversity Conservation) programme of the European Commission.
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Possible electric charge nonconservation and dequantization in SU(2)×U(1)SU(2) \times U(1) models with hard symmetry breaking

We study a novel type of extensions of the Standard Model which include a hard mass term for the U(1) gauge field and, optionally, the additional scalar multiplets spontaneously violating the electric charge conservation. Contrary to the case of abelian massive electrodynamics, in these theories the massiveness of photon necessarily implies non-conservation (and also dequantization) of the electric charge (even in the absence of spontaneous breakdown of the electromagnetic symmetry). On the other hand, unexpectedly, there exist models with charge non-conservation where it is possible to keep the photon mass zero (at least, at the tree level).Comment: 10 pages, revtex, no figures, to appear in Physics Letters

Pl@ntWood: A computer-assisted identification tool for 110 species of Amazon trees based on wood anatomy

World interest in conservation of tropical forests has increased due to elevated rates of deforestation and climate change issues. Tropical forests are threatened by extensive agriculture and timber trade among other factors; thus, sustainable management and conservation of tropical tree species require reliable and user accessible identification tools. Although wood anatomical features provide a considerable amount of information, only a handful of experts are able to use it for plant species identification. Here, we propose an interactive tool, based on vector graphics, illustrating 96 states of 22 wood anatomical characters from 110 Amazonian tree species belonging to 34 families. Pl@ntWood is a graphical identification tool based on the IDAO (Identification des plantes Assistée par Ordinateur) system, a multimedia approach to plant identification. This system allows non-specialists to identify plants in a user-friendly interface while stimulating self-training in wood anatomy of tropical species. (Texte intégral

Chiral fermions and gauge-fixing in five-dimensional theories

We study in detail the issue of gauge-fixing in theories with one universal extra dimension, i.e. theories where both bosons and fermions display Kaluza-Klein (KK) excitations. The extra dimension is compactified using the standard orbifold construction for a massless chiral fermion. We carry out the gauge-fixing procedure at the level of the five-dimensional theory and determine the tree-level propagators and interaction vertices needed for performing perturbative calculations with the effective four-dimensional theory resulting after the compactification. The gauge-independence of the tree-level S-matrix involving massive KK modes is verified using specific examples. In order to obtain massive fermionic zero modes one has to enlarge the theory by introducing a set of mirror fermions, a construction which is carried out in detail. Finally, the gauge-independence of the tree-level S-matrix involving the resulting new mass-eigenstates is proved by resorting to generalized current conservation equations.Comment: 10 pages, 5 figures, revtex and axodra

Graviton-Scalar Interaction in the PP-Wave Background

We compute the graviton two scalar off-shell interaction vertex at tree level in Type IIB superstring theory on the pp-wave background using the light-cone string field theory formalism. We then show that the tree level vertex vanishes when all particles are on-shell and conservation of p_{+} and p_{-} are imposed. We reinforce our claim by calculating the same vertex starting from the corresponding SUGRA action expanded around the pp-wave background in the light-cone gauge.Comment: 26 pages, harvmac One reference added. A few comments changed in the introduction. The "cyclic perms." term removed from some equations as unnecessary and equations (2.38) and (3.19) are corrected accordingl

The management of tree genetic resources and the livelihoods of rural communities in the tropics: non-timber forest products, smallholder agroforestry practices and tree commodity crops

Products and services provided by trees in forests and farmland support the needs and promote the wellbeing of hundreds of millions of people in the tropics. Value depends on managing both the diversity of tree species present in landscapes and the genetic variation within these species. The benefits from trees and their genetic resources are, however, often not well quantified because trade is frequently outside formal markets, there is a multiplicity of species and ways in which trees are used and managed, and genetic diversity within species is frequently not given proper consideration. We review here what is known about the value of trees to rural communities through considering three production categories: non-timber products harvested from trees in natural and managed forests and woodlands; the various products and services obtained from a wide range of trees planted and/or retained in smallholders’ agroforestry systems; and the commercial products harvested from cultivated tree commodity crops. Where possible, we focus on the role of intra-specific genetic variation in providing support to livelihoods, and for each of the three production categories we also consider wider conservation and sustainability issues, including the linkages between categories in terms of management. Challenges to ‘conventional wisdom’ on tree resource use, value and management – such as in the posited links between commercialisation, cultivation and conservation – are highlighted, and constraints and opportunities to maintain and enhance value are described