Abstract: Field studies in Acre, Brazil assessed logging impacts of a certified community timber management project. The main objectives of the study were: (1) to determine if damage incidence to future crop trees (FCTs; >= 20 cm diameter at breast height (dbh)) differs between (a) forest with and without bamboo (Guadua spp.), and (b) trees with and without lianas; (2) to what extent harvesting can be conducted more intensely (m(3)ha(-1)), without incurring greater FCT damage; and (3) to what extent marking diminishes FCT damage. Full inventories of FCTs of 50 commercial species complexes were conducted before and after logging in 50 m-radius zones of impact around each designated harvest tree in three 10 ha (200 m x 500 m) logging blocks. We also mapped all forested areas potentially influenced by logging, including skid trails, log landings and felling gaps, throughout the 30 ha logged. More than 28% of the forest area was disturbed by logging, with 12.1% in skid trails and 16.8% in gap clearings, indicating that the forest gap mosaic can be significantly altered even when reduced-impact logging guidelines are followed. Overall, 15% of FCTs inventoried were damaged. Damage rates were not significantly reduced by marking treatment, location in bamboo-dominated forest, or liana load on FCT damage. Harvest intensity did not influence the probability of FCT damage. For future studies, it would be prudent to address impacts of timber extraction on other livelihood activities, such as non-timber forest product collection, particularly in such regions as the Brazilian Amazon, where many communities are attempting to integrate a suite of income-generating activities. (C) 2007 Elsevier B.V. All rights reserved.

Abstract: This article presents a theoretical verification of the reinforced-matrix hypothesis derived from tensor equations, σ W = σ f + σ m and ε W = ε f = ε m (Wood Sci Technol 32:171–182, 1998; Wood Sci Technol 33:311–325, 1999; J Biomech Eng 124:432–440, 2002), using classical Mori-Tanaka theory on the micromechanics of fiber-reinforced materials (Acta Metall 21:571–574, 1973; Micromechanics — dislcation and inclusions (in Japanese), pp 141–147, 1976). The Mori-Tanaka theory was applied to a small fragment of the cell wall undergoing changes in its physical state, such as those arising from sorption of moisture, maturation of wall components, or action of an external force, to obtain ⟨σ A⟩D = ϕ·⟨σ F⟩I + (1−ϕ)·⟨σ M⟩D−I. When the constitutive equation of each constituent material was applied to the equation ⟨σ A⟩D = ϕ·⟨σ F⟩I + (1−ϕ)·⟨σ M⟩D−I, the equations σ W = σ f + σ m and ε W = ε f = ε m were derived to lend support to the concept that two main phases, the reinforcing cellulose microfibril and the lignin-hemicellulose matrix, coexist in the same domain. The constitutive equations for the cell wall fragment were obtained without recourse to additional parameters such as Eshelby’s tensor S and Hill’s averaged concentration tensors AF and AM. In our previous articles, the coexistence of two main phases and σ W = σ f + σ m and ε W = ε f =ε m had been taken as our starting point to formulate the behavior of wood fiber with multilayered cell walls. The present article provides a rational explanation for both concepts.

Abstract: Plant ants generally provide their host myrmecophytes (i.e. plants that shelter a limited number of ant species in hollow structures) protection from defoliating insects, but the exact nature of this protection is poorly known. It was with this in mind that we studied the association between Tetraponera aethiops F. Smith (Pseudomyrmecinae) and its specific host myrmecophyte Barteria fistulosa Mast. (Passifloraceae). Workers bore entrances into the horizontal hollow branches (domatia) of their host B. fistulosa, near the base of the petiole of the alternate horizontal leaves. They then ambush intruders from the domatia, close to these entrances. After perceiving the vibrations caused when an insect lands on a leaf, they rush to it and sting and generally spreadeagle the insect (only small caterpillars are mastered by single workers). Among the insects likely to defoliate B. fistulosa, adult leaf beetles and large katydids were taken as prey and cut up; single workers then retrieved some pieces, whereas other workers imbibed the prey's haemolymph. Other insects known to defoliate this plant, if unable to escape, were killed and discarded. Small Acrea zetes L. caterpillars were stung and then discarded by single workers; whereas locusts of different sizes were mastered by groups of workers that stung and spreadeagled them before discarding them (although a part of their haemolymph was imbibed). More workers were involved and more time was necessary to master insects taken as prey than those attacked and discarded. Consequently, the protection T. aethiops workers provide to their host B. fistulosa from defoliating insects results from predation, but more often from a type of aggressiveness wherein insects are killed and then discarded. (c) 2008 The Linnean Society of London.

Abstract: Background and Aims Plastic tree-shelters are increasingly used to protect tree seedlings against browsing animals and herbicide drifts. The biomass allocation in young seedlings of deciduous trees is highly disturbed by common plastic tree-shelters, resulting in poor root systems and reduced diameter growth of the trunk. The shelters have been improved by creating chimney-effect ventilation with holes drilled at the bottom, resulting in stimulated trunk diameter growth, but the root deficit has remained unchanged. An experiment was set up to elucidate the mechanisms behind the poor root growth of sheltered Prunus avium trees. Methods Tree seedlings were grown either in natural windy conditions or in tree-shelters. Mechanical wind stimuli were suppressed in ten unsheltered trees by staking. Mechanical stimuli (bending) of the stem were applied in ten sheltered trees using an original mechanical device. Key Results Sheltered trees suffered from poor root growth, but sheltered bent trees largely recovered, showing that mechano-sensing is an important mechanism governing C allocation and the shoot-root balance. The use of a few artificial mechanical stimuli increased the biomass allocation towards the roots, as did natural wind sway. It was demonstrated that there was an acclimation of plants to the imposed strain. Conclusions This study suggests that if mechanical stimuli are used to control plant growth, they should be applied at low frequency in order to be most effective. The impact on the functional equilibrium hypothesis that is used in many tree growth models is discussed. The consequence of the lack of mechanical stimuli should be incorporated in tree growth models when applied to environments protected from the wind (e.g. greenhouses, dense forests).

Abstract: It is well known that arboreal ants, both territorially dominant species and plant ants (e.g., species associated with myrmecophytes or plants housing them in hollow structures), protect their host trees from defoliators. Nevertheless, the presence of an induced defense, suggested by the fact that the workers discovering a leaf wound recruit nestmates, is only known for plant ants. Based on the results from a field study, we show here (1) that colonies of Azteca chartifex, a territorially dominant, neotropical arboreal ant species, mostly selected Goupia glabra (Goupiaceae) trees in which to build their principal carton nests and (2) that plant signals induced workers to recruit nestmates, which patrol the leaves, likely providing the plant with a biotic defense. Furthermore, the number of recruited workers was clearly higher on G. glabra, their most frequently selected host tree species, than on other tree species. These results show that contrary to what was previously believed, induced responses are also found in territorially dominant arboreal ants and so are not limited to the specific associations between myrmecophytes and plant ants.