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ThesisItem Open Access Impact of variable spacing on the pattern of genetic variability and heritability on growth, yield and specific gravity in five year old trees of dalbergia sissoo roxb.(JNKVV, 2014) Choudhary, Neha; Pathak, N.N.In India, it was realised that there was an increasing demand for wood, and forests resources had been over-used, fast growing tree plantations as wood crops were considered as the best alternative by various governmental and non- governmental agencies. Dalbergia sissoo fetch a better price for their wood, in addition to various intangible products such as fodder and ash which are commonly used by locals. The study of genetic variability, heritability and genetic advance, as well as character assocition is a prerequisite for any systematic and sound tree improvement program. Although, variability in growth traits and flexibility of wood (modulus of elasticity, modulus of rupture, maximum crushing strength parallel to the grain, etc.) makes it useful for many kinds of products such as door and window shutters and frames, flooring and paneling, and also for cabinet making, vehicle bodies, boat building, handles, implements such as shoe lasts, turnery, carving, veneer and plywood, etc. giving it greater utility. Many factors are responsible for the variability (wood quality) in wood and specific gravity is one of them. Spacing of plants is an important aspect that needs to be carefully conducted and properly arranged for successful plantation. In the present investigation, attempts may be made to achieve the following objectives: 1. To estimate the pattern of genetic variation and heritability in growth, yield and wood quality trait (specific gravity) within and between trees of Dalbergia sissoo under variable spacing. 2. Inter-relationship between growth, yield and wood quality trait (specific gravity) under variable spacing. The present investigation entitled “Impact of Variable Spacing on the Pattern of Genetic Variability and Heritability on Growth, Yield and Specific Gravity in Five-Year-Old Trees of Dalbergia sissoo Roxb.” was carried out at Forestry Research Farm, Imalia, Department of Forestry, Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur (M.P.) during the year 2013-14 in five years old D.sissoo plantation. This was the fifth year of experimentation on the same site without changing the treatment and layout plan. The assessment of growth, yield and specific gravity was done on the basis of dbh, total tree height, basal diameter, etc. under variable spacing. A set of four treatments (Spacing/Planting density) 1 m X 1 m (10,000 trees/ha), 2 m X 1 m (5,000 trees/ha), 2 m X 1.5 m (3,333 trees/ha) and 2 m X 2 m (2,500 trees/ha) was laid out in Randomized Block Design and replicated six times. Results revealed that the basal diameter, dbh, cylindrical volume, mean specific gravity, specific gravity at the bottom (0.30 m), dbh (1.37 m) and top of tree (4.00 m), and tree weight having maximum value in the spacing of 2 m X 2 m i.e. 9.18 cm, 9.06 cm, 0.050 m3, 0.785, 0.794, 0.795, 0.770 and 30.0 kg respectively indicated the suitability of 2 m X 2 m spacing i.e., 2500 tree /ha for better growth and yield. The present data demonstrate the pattern and magnitude of specific gravity under variable spacing within and between trees. The specific gravity at wider spacing (2 m X 2 m) was significantly higher than that of trees grown at narrower spacing (1 m X 1 m). Mean specific gravity was found significant with different density, as trees at the wider spacing (2 m X 2 m) have higher specific gravity (0.785) than those at closer spacing (1 m X 1 m). Within tree variation in specific gravity was recorded at three different heights and found statistically different with respect to different height levels. Within tree variation of specific gravity at base i.e., old growth was more compared to top growth (juvenile growth). It showed increase in specific gravity with decreasing age of the tree is seen in a negative relationship between specific gravity and tree height. Current Annual Increment (C.A.I.) was found significant for tree height, basal diameter, diameter at breast height (dbh) and weight of pruning material. Mean Annual Increment (M.A.I.) found significant for weight of pruning material, basal area and cylindrical volume showed that these are statistically different among population. Analysis of variance for different characters under study revealed that the treatment effects were highly significant suggesting existence of high genetic variability in the population under study. Such variability is desirable and can be utilized for developing new genotypes in D.sissoo. This variability provides many avenues for genetic improvement in the Sissoo High heritability with high genetic advance as per cent of mean was manifested by basal area, basal diameter and dbh revealed predominance of additive gene action and indicated strong genetic control of these variables. Pooled analysis of growth traits from 2010-2013 showed significant year and spacing interaction for all growth traits except for tree height. A correlation matrix of various growth attributes revealed strong and positive association among these attributes. The linear regression equation between cylindrical volume and basal diameter, dbh, diameter at 2 m height of tree, mean specific gravity, specific gravity at bottom, specific gravity at dbh, specific gravity at top, tree weight and basal area characters showed a unit increase with values of 0.0103, 0.0104, 0.0415, 0.556, 0.0064, 0.6934, 0.368, 0.0025 and 8.418, respectively.