Growth and productivity assessment of Casuarina glauca Sieb. ex. Spreng on sodic soil sites

Casuarina glauca is an introduced tree species to India. It is one the few species that can grow successfully in salt effected sites. C. glauca was investigated for biomass production at highly sodic soil sites (pH 8.6-10.5); it was found to be promising in terms of growth and productivity. Average height of plants in an 8-yr-old trial of Casuarina glauca was 1033.3 ± 270 cm, however diameter at breast height (dbh) remained at 8.59 ± 2.0 cm with a basal area of 6.68 ± 1.6 cm2 per plant. High plant survival and establishment (75%) indicate its potential for afforestation of degraded soil sites. Linear regression equations (Y = a + bx) were developed to predict biomass of standing stocks defining relationships between growth parameters (x) as independent variable and productivity (Y) as dependent variable. Both uni-factor equations based on one independent variable (height or diameter alone), and multifactors involving both height and diameter together (d2h) were derived to predict biomass of different plant components. Coefficient of correlation and regression coefficients were found to be highly significant (p < 0.001) in all the equations irrespective of independent variable such as plant height, diameter or both (d2h). There were marginal differences in r2 value (0.78-0.8) among equations derived by using d2 or d2h as independent variables. Height alone had relatively poor functional correlation with yield (r2 = 0.45). Accordingly, uni-factor linear equations with diameter (d2) were used for computing stand biomass with reasonably good accuracy. At the age of 8 years, stand productivity was 68.2 t ha−1 (oven dry biomass) out of which relatively a very high proportion (80.3%) of biomass was allocated to stem wood (54.8 t ha−1). Both branch wood (8.4 t ha−1) and leaves (5 t ha−1) contributed marginally. Casuarina glauca can be recommended as a promising species for biomass production on sodic soil sites as is evident from its performance.