Search

Context Poplars (Populus species and hybrids) are fastgrowing trees used to make various products. In north European countries, they are mainly grown on agricultural land, but interest in planting poplars on forest land has increased. Aims Plant damage and mortality problems occur on forest land, probably due to soil conditions and competing vegetation. It is therefore of interest to investigate whether combinations of soil preparation methods and plant materials can improve establishment. Methods At three sites in southern Sweden, the effects of four soil preparation treatments (no soil preparation, patch scarification, mounding, soil inversion) in combination with three plant types (short cuttings, long cuttings, rooted plants) were studied. Results Survival and growth were significantly influenced by site, soil preparation method, plant type, and their interactions. Mounding resulted in the best overall performance on all sites. Interactions between site and plant type revealed differences in growth dependent on site conditions, but rooted plants and long cuttings were in general most successful. Patch scarification and short cuttings were associated with lower survival and growth. Conclusion Soil preparation is needed to support survival and early growth, but the combination of method and plant type must be adapted to site conditions. The choice of clones should also be considered. [ABSTRACT FROM AUTHOR]

GenusPopuluscomprises about 25–35 species of deciduous flowering plants in the family Salicaceae which are widely distributed in temperate climates of the Northern Hemisphere.Populusspecies are important resources in certain branches of industry and have a special role for the scientific study of biological and agricultural systems. The poplar is known for its remarkable significance among the commercially propagated tree species such as teak, eucalyptus, wild cherry, red wood, and radiata pine.In vitroregeneration refers to growing and multiplications of cells, tissues and organs on defined liquid/solid media under aseptic and controlled environments.In vitroclonal propagation of forest trees, due to the high multiplication rate, is an attractive alternative for rapid propagation of elite genotypes of those species that could not easily be propagated through conventional methods. Owing to their widespread uses at the industrial level and for meeting the ever-increasing global demand for biomass production and wood industry, tissue culture techniques can be exploited for rapid cloning and large-scale production of planting material of various poplar species. Recent progress in the field of plant tissue culture determined this area to be one of the most dynamic and promising for experimental biology. Much work has been carried out onin vitroplant regeneration studies inPopulusspp. including direct organogenesis, indirect organogenesis and somatic embryogenesis. These reviews provide an insight forin vitroplant regeneration studies in poplar species and their potential in its improvement. [ABSTRACT FROM AUTHOR]

Abstract: Postfire tree species compositions are predicted to be the same prior to fire according to the direct regeneration hypothesis (DRH). We studied 94 upland boreal forest stands between 5 and 18 years after fire in Ontario, Canada. Postfire species-specific regeneration density was positively related to prefire stand basal area for Pinus banksiana, Populus spp., Betula papyrifera and Picea mariana, but not for Picea glauca and Abies balsamea. In addition, seedling density of Populus spp., B. papyrifera, P. mariana, P. glauca and A. balsamea were positively affected by build up index and, except Populus spp., their density increased with age of burn. To facilitate testing the DRH, we introduced a term called compositional difference (CD) that is the difference in a species relative percentage between the postfire and prefire stand. The testable null hypothesis is CD=0 for a given species. CD was not different from 0 for P. banksiana, was 19.8% for Populus spp., 10.4% for B. papyrifera, −17.9% for P. mariana, −14.6% for P. glauca, and −14.9% for A. balsamea, indicating fire increases broadleaves at the expenses of mid- and late-successional coniferous species. Compositional increases of Populus spp. and B. papyrifera in postfire stands occurred mostly where these species were a minor component prior to fire. In conclusion, the DRH was supported by the specific positive relationships between postfire regeneration densities and prefire basal area for P. banksiana, Populus spp., B. papyrifera and P. mariana. However, if the DRH is used for predicting postfire composition, P. banksiana is the only species that had the same composition between postfire and prefire stands. Nevertheless, CD for P. banksiana was negatively related to its prefire composition. Similarly, CD for other species was negatively related to their prefire compositions with varying effects of build up index and age of burn. Our results suggest, if fire occurrences increase with global change, the boreal landscape will be more dominated by hardwoods and mixtures of conifers and hardwoods. [Copyright &y& Elsevier]

We have compared biomass-allocation patterns and frequency of sprouting among saplings of four tree species ( Larix kaempferi, Betula platyphylla var. japonica, Populus maximowiczii, and Populus sieboldii) growing on a volcanic mountain in Hokkaido, northern Japan. Growing conditions were very harsh on the mountainside. Leaf mass and fine root mass relative to root mass were larger in L. kaempferi, and L. kaempferi root mass was less than for the other species. Sprouting ratios were high for the broadleaved species. Different allometries and sprouting ratios among species suggest that survival strategies for L. kaempferi were different from those for the broadleaved species. L. kaempferi has greater ability to increase leaf mass under harsh growing conditions; this probably results in large photosynthetic production by L. kaempferi on the volcano. In contrast, the two Populus species and Betula platyphylla seem to maintain populations through their ability to produce sprouts from large root systems. [ABSTRACT FROM AUTHOR]

Four Populus clones were grown at three spacings (0.5, 1.0, and 1.5 m) in monoclonal plots and in polyclonal plots with all clones in intimate mixture. After the third year, many individual tree and stand traits differed significantly by clone, spacing, deployment method, and their interactions. Differences among clones in growth and stem form were greater in polyclonal than in monoclonal plots, and differences in performance between deployment methods were greater in the denser spacings. Monoclonal stands had greater uniformity in tree size than polyclonal stands. Total aboveground oven-dry woody yield averaged 48.0 Mg.ha-1 in the 0.5-m spacing and decreased as spacingincreased. Some clones differed in yield from other clones in both monoclonal and polyclonal plots. Assuming that equal numbers of plantsfrom the same clones were planted, the manner of deployment did not affect productivity; that is, although there were clonal differences in yield, mean yield of the four clones in monoclonal plots (44.3 Mg.ha-1) did not differ from the yield of polyclonal plots (43.1 Mg.ha-1). Comparative yields (yield in polyclonal plots/yield in monoclonal plots) differed substantially, however, and theincreases or decreases in comparative yield differed with spacing and clone. Production and inventory were less evenly balanced among clones with polyclonal than with monoclonal deployment. [ABSTRACT FROM AUTHOR]