Complementary resource use by tree species in a rain forest tree plantation

Mixed-species tree plantations, composed of high-value native rain forest timbers, are potential forestry systems for the subtropics and tropics that can provide ecological and production benefits. Choices of rain forest tree species for mixtures are generally based on the concept that assemblages of fast-growing and light-demanding species are less productive than assemblages of species with different shade tolerances. We examined the hypothesis that mixtures of two fast-growing species compete for resources, while mixtures of shade-tolerant and shade-intolerant species are complementary. Ecophysiological characteristics of young trees were determined and analyzed with a physiology-based canopy model (MAESTRA) to test species interactions. Contrary to predictions, there was evidence for complementary interactions between two fast-growing species with respect to nutrient uptake, nutrient use efficiency, and nutrient cycling. Fast-growing Elaeocarpus angustifolius had maximum demand for soil nutrients in summer, the most efficient internal recycling of N, and low P use efficiency at the leaf and whole-plant level and produced a large amount of nutrient-rich litter. In contrast, fast-growing Grevillea robusta had maximum demand for soil nutrients in spring and highest leaf nutrient use efficiency for N and P and produced low-nutrient litter. Thus, mixtures of fast-growing G. robusta and E. angustifolius or G. robusta and slow-growing, shade-tolerant Castanospermum australe may have similar or even greater productivity than monocultures, as light requirement is just one of several factors affecting performance of mixed-species plantations. We conclude that the knowledge gained here will be useful for designing large-scale experimental mixtures and commercial forestry systems in subtropical Australia and elsewhere

The relationship between dark triad personality traits and sexting behaviors among adolescents and young adults across 11 countries

Background: Sexting is an increasingly common phenomenon among adolescents and young adults. Some studies have investigated the role of personality traits in different sexting behaviors within mainstream personality taxonomies like Big Five and HEXACO. However, very few studies have investigated the role of maladaptive personality factors in sexting. Therefore, the present study investigated the relationship between Dark Triad Personality Traits and experimental (i.e., sharing own sexts), risky (i.e., sexting under substance use and with strangers), and aggravated sexting (i.e., non-consensual sexting and sexting under pressure) across 11 countries. Methods: An online survey was completed by 6093 participants (Mage = 20.35; SDage = 3.63) from 11 different countries which covered four continents (Europe, Asia, Africa, and America). Participants completed the Sexting Behaviors Questionnaire and the 12-item Dark Triad Dirty Dozen scale. Results: Hierarchical regression analyses showed that sharing own sexts was positively predicted by Machiavellianism and Narcissism. Both risky and aggravated sexting were positively predicted by Machiavellianism and Psychopathy. Conclusions: The present study provided empirical evidence that different sexting behaviors were predicted by Dark Triad Personality Traits, showing a relevant role of Machiavellian-ism in all kinds of investigated sexting behaviors. Research, clinical, and education implications for prevention programs are discussed

VEGF and Angiopoietin-1 Exert Opposing Effects on Cell Junctions by Regulating the Rho GEF Syx

Vascular endothelial growth factor (VEGF) and Ang1 (Angiopoietin-1) have opposing effects on vascular permeability, but the molecular basis of these effects is not fully known. We report in this paper that VEGF and Ang1 regulate endothelial cell (EC) junctions by determining the localization of the RhoA-specific guanine nucleotide exchange factor Syx. Syx was recruited to junctions by members of the Crumbs polarity complex and promoted junction integrity by activating Diaphanous. VEGF caused translocation of Syx from cell junctions, promoting junction disassembly, whereas Ang1 maintained Syx at the junctions, inducing junction stabilization. The VEGF-induced translocation of Syx from EC junctions was caused by PKD1 (protein kinase D1)-mediated phosphorylation of Syx at Ser806, which reduced Syx association to its junctional anchors. In support of the pivotal role of Syx in regulating EC junctions, syx−/− mice had defective junctions, resulting in vascular leakiness, edema, and impaired heart function

Stable Vascular Connections and Remodeling Require Full Expression of VE-Cadherin in Zebrafish Embryos

BACKGROUND: VE-cadherin is an endothelial specific, transmembrane protein, that clusters at adherens junctions where it promotes homotypic cell-cell adhesion. VE-cadherin null mutation in the mouse results in early fetal lethality due to altered vascular development. However, the mechanism of action of VE-cadherin is complex and, in the mouse embryo, it is difficult to define the specific steps of vascular development in which this protein is involved. METHODOLOGY AND PRINCIPAL FINDINGS: In order to study the role VE-cadherin in the development of the vascular system in a more suitable model, we knocked down the expression of the coding gene in zebrafish. The novel findings reported here are: 1) partial reduction of VE-cadherin expression using low doses of morpholinos causes vascular fragility, head hemorrhages and increase in permeability; this has not been described before and suggests that the total amount of the protein expressed is an important determinant of vascular stability; 2) concentrations of morpholinos which abrogate VE-cadherin expression prevent vessels to establish successful reciprocal contacts and, as a consequence, vascular sprouting activity is not inhibited. This likely explains the observed vascular hyper-sprouting and the presence of several small, collapsing vessels; 3) the common cardinal vein lacks a correct connection with the endocardium leaving the heart separated from the rest of the circulatory system. The lack of closure of the circulatory loop has never been described before and may explain some downstream defects of the phenotype such as the lack of a correct vascular remodeling. CONCLUSIONS AND SIGNIFICANCE: Our observations identify several steps of vascular development in which VE-cadherin plays an essential role. While it does not appear to regulate vascular patterning it is implicated in vascular connection and inhibition of sprouting activity. These processes require stable cell-cell junctions which are defective in absence of VE-cadherin. Notably, also partial modifications in VE-cadherin expression prevent the formation of a stable vasculature. This suggests that partial internalization or change of function of this protein may strongly affect vascular stability and organization

Temporal dynamics of ectomycorrhizal populations and seedling characteristics on red pine (Pinus resinosa)

To assess temporal dynamics of ectomycorrhizae (ECM) on red pine seedlings, numbers of ECM per gram of dry root were compared with temporal changes in seedling height, basalt diameter, above- and below-ground (coarse root) biomass, shoot:root ratio, and leaf water potentials. Three morphological types of ECM were observed. Temporal changes in numbers of total and brown-type ECM were significantly correlated with all seedling characteristics. The highest correlation (negative) occurred between field age of red pine seedlings and numbers of both total and brown-type ECM per gram dry root; high negative correlations also existed between basal diameter, total height of red pine seedlings, and numbers of total and brown-type ECM per gram dry root. Decreased average leaf water potential was observed to relate to increases in numbers of total and brown-type ECM. -from Author