Productivity and Biomass Properties of Poplar Clones Managed in Short-Rotation Culture as a Potential Fuelwood Source in Georgia

Georgian forests are very valuable natural resources, but due to the lack of affordable alternatives to firewood, people are forced to use forest resources illegally and unsustainably. The aim of this study was to determine the productivity and biomass properties of four poplar clones from Aigeiros and Tacamahaca and one control clone, considering their wood and bark characteristics and their proportion in the stems. Short-rotation woody crops with these clones represent a potential source of commercial fuelwood production in Georgia as an alternative to natural forests. These tree characteristics were evaluated after three years of growth. The survival of the clones was generally high. No significant differences in biomass production (dry matter, DM) were found among the four clones tested (DM of approximately 4 Mg ha−1 yr−1), while the control clone achieved significantly lower values for DM. The biomass specific density was exceptionally high, at 481–588 kg m−3, which was a result of the high proportion of bark mass in the stem (23.3–37.7%), with a density almost twice that of wood. On the other hand, the tested clones had a very high ash content in the biomass (2.6–4.5%), which negatively affected their energy potential expressed as a lower heating value (17,642–17,849 J g−1). Our preliminary results indicated that both the quantity and quality of biomass are important factors to justify the investment in an intensive poplar culture. The four clones should be further considered for commercial biomass production and tested at different sites in Georgia to evaluate the genotype-by-environment interactions and identify the site conditions required to justify such an investment.

Reelin transiently promotes N-cadherin–dependent neuronal adhesion during mouse cortical development

Reelin is an essential glycoprotein for the establishment of the highly organized six-layered structure of neurons of the mammalian neocortex. Although the role of Reelin in the control of neuronal migration has been extensively studied at the molecular level, the mechanisms underlying Reelin-dependent neuronal layer organization are not yet fully understood. In this study, we directly showed that Reelin promotes adhesion among dissociated neocortical neurons in culture. The Reelin-mediated neuronal aggregation occurs in an N-cadherin–dependent manner, both in vivo and in vitro. Unexpectedly, however, in a rotation culture of dissociated neocortical cells that gradually reaggregated over time, we found that it was the neural progenitor cells [radial glial cells (RGCs)], rather than the neurons, that tended to form clusters in the presence of Reelin. Mathematical modeling suggested that this clustering of RGCs could be recapitulated if the Reelin-dependent promotion of neuronal adhesion were to occur only transiently. Thus, we directly measured the adhesive force between neurons and N-cadherin by atomic force microscopy, and found that Reelin indeed enhanced the adhesiveness of neurons to N-cadherin; this enhanced adhesiveness began to be observed at 30 min after Reelin stimulation, but declined by 3 h. These results suggest that Reelin transiently (and not persistently) promotes N-cadherin–mediated neuronal aggregation. When N-cadherin and stabilized β-catenin were overexpressed in the migrating neurons, the transfected neurons were abnormally distributed in the superficial region of the neocortex, suggesting that appropriate regulation of N-cadherin–mediated adhesion is important for correct positioning of the neurons during neocortical development.

SUBSTANTIATION OF EVALUATION CRITERIA FOR OVERALL FUNCTIONING EFFICIENCY OF UKRAINIAN DANUBE RICE IRRIGATION SYSTEMS

The paper presents the results of studies the efficiency of the Danube rice irrigation systems south of Ukraine on the basis of appropriate analysis of productivity leading rice rotation culture - the culture of rice. Substantiated a set of indicators covering different aspects of the complex process of formation of a crop of rice crop, with the aim of improving and optimizing the management of rice irrigation system in compliance with the modern ecological and economic requirements.

Mycoflora as a factor of protection of wheat against of diseases caused by fungi, depending of ecological conditions

Researchs were made on simplificated monoculture of wheat in comparison with culture with crop rotation. Culture with rotation was more positive against to 2 main pathogens: <i>Fusarium culmorum</i> and <i>Rhizoctonia cerealis</i>.

Fonction puits de carbone des taillis d'eucalyptus à Madagascar

Les écosystèmes forestiers jouent un grand rôle face au réchauffement climatique grâce aux réservoirs importants de carbone organique (C) de leurs compartiments (aérien, racinaire, litière et sol). En ce qui concerne l'utilisation des terres, les changements d'affectation des terres et la foresterie, des mesures précises des stocks de C dans ces compartiments sont recommandées. Dans ce sens, la capacité de fixation de C des taillis d'eucalyptus (20 à 111 ans) des Hautes Terres centrales malgaches dans ces compartiments a été étudiée, en comparaison avec d'autres modes d'usage des terres (pseudo-steppe, rotation culture/jachère). Des mesures destructives de biomasses et des prélèvements de sols ont été effectués, suivis par le développement d'équations allométriques et des analyses en laboratoire (détermination de la teneur en carbone, étude isotopique). Tous âges confondus, la pratique de taillis d'eucalyptus présente le plus grand stock de C (150,8 ± 25,3 Mg C/ha face à 112 ± 15 et 72,3 ± 9,9 Mg C/hapour la pseudo-steppe et la rotation culture/jachère respectivement). Pour tous les modes d'usage, c'est le compartiment sol qui constitue le principal réservoir de C avec 56% pour l'eucalyptus et plus de 96 % pour les autres modes. Mais ce sont essentiellement la souche et les racines lignifiées qui rendent ces plantations d'eucalyptus plus efficaces que les autres modes d'usage (44 Mg C/ha pour l'eucalyptus face à 2 Mg C/ha) en termes de stockage de C. D'après l'étude isotopique, le C dérivé de l'eucalyptus dans le sol ne domine toutefois qu'en surface, probablement en raison de la gestion en taillis. Cependant, d'autres facteurs, à part la durée de plantation, comme l'altitude et la morphopédologie sont à considérer pour comprendre la dynamique des stocks de C mesurés. (Résumé d'auteur)