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.
Plantation technology for selected indigenous trees in the Indian peninsula
Les techniques a utiliser en pepiniere et en plantations pour cinq essences a usages multiples, endemiques de l'Inde - Calophyllum polyanthum Wall. (Clusiacees), Dysoxylum malabaricum Bedd. (Meliacees), Garcinia gummi-gutta (L.) Robson (Clusiacees), Melia dubia Cav. (Meliacees) et Vateria indica L. (Dipterocarpacees) - sont issues de travaux (1999-2002) fondes sur des essais en laboratoire, pepiniere et sur le terrain. Ces essences produisent du bois d'œuvre, sauf G. gummi-gutta utilisee pour le bois de feu. Peu d'informations sont disponibles sur la regeneration artificielle de ces essences, qui sont en voie de disparition rapide dans leurs milieux naturels. Les aspects lies aux semences, a la croissance en pepiniere et a la plantation ont ainsi ete definis pour regenerer ces essences. Ils incluent les donnees sur la collecte, le traitement et le stockage des fruits et graines ainsi que sur la germination, les aspects phytosanitaires, les facteurs agissant sur les taux de survie et de croissance des plants au champ. Ces donnees originales peuvent faciliter la regeneration artificielle de ces essences en Inde, pour valoriser les ressources ou dans des programmes de rehabilitation de sites forestiers, necessaires sous les tropiques, afin de maintenir les ecosystemes et leurs ressources.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.