Assessment of certain wood quality parameters of selected genotypes of Melia dubia Cav. grown in a seedling seed orchard
Certain wood quality parameters of about 9-year-old Melia dubia Cav. trees grown in a seedling seed orchard at Yeshwanthpura Research Station of Kolar research range, Karnataka India were studied. Trees were categorized into three classes depending upon their girth at the breast height––small (<40 cm), medium (40–60 cm) and big (>60 cm). Different anatomical (gross structure), physical and mechanical properties of the wood were evaluated using standard testing procedures and Indian Standards. The results of this study showed that there was no significant difference in the heartwood percentage and specific gravity among three girth classes. High shrinkage values from green to oven-dry condition in all the classes indicate that the timber is dimensionally unstable compared to teak. The static bending strength parameters––FS at LP, MOR and MOE, compression strength parallel to grain, compressive strength perpendicular to grain at limit of proportionality and surface hardness (side and end) were evaluated and compared among all the three girth classes. The data on mechanical properties were statistically analysed using ANOVA between three girth classes. The results on wood quality parameters may be utilized in selection of suitable genotypes for raising large scale plantations.
Assessment of Root Plate Structure in Wind-Thrown Trees of Melia dubia
Root plays a significant role in tree growth and development and information pertaining to spread of the root and its depth will be useful for establishing plantations. Most of the root studies are generally carried out in trees growing in urban areas in avenues, but limited studies are carried out in plantations. Being an underground part of the tree, there are inherent difficulties in understanding root architecture. Uprooting of trees due to storm or wind damage provides an ideal opportunity to obtain critical understanding about tree roots. Such study has been carried out in an 11 year old storm ravaged Melia dubia plantation in Punjab, India. Field observations such as tree girth, root girth, root plate width and depth was recorded on uprooted trees. A large variability was recorded for all the traits. Root plate width and depth ranged from 1.42 to 5.17 m and 0.75 to 2.50 m, respectively. A strong positive relationship between tree girth and primary root girth, root plate width and depth identified in this study provides base line information which can be used while establishing M. dubia plantations.Keywords: Melia dubia, root plate, root width, root depth, wind-thrown
Brauer groups of genus zero extensions of number fields
We determine the isomorphism class of the Brauer groups of certain nonrational genus zero extensions of number fields. In particular, for all genus zero extensions E of the rational numbers Q that are split by Q(√2), Br(E) ≅ Br(Q(t)).