PRODUCTIVITY DYNAMICS OF <em>POPULUS</em> <em>DELTOIDES</em> CLONES ON A DEGRADED GANGETIC-ALLUVIUM IN NORTH INDIA

Abstract

Dry matter dynamics of 6-y-old Populus deltoides clones (G3, G48 and D121) were studied in a degraded site of the Gangetic plains in north India. Whilst absolute biomass increased with tree growth, there was a big reduction (95-27%) in corresponding increase in proportional biomass. Biomass profile and crown architecture were developed along the vertical axis of the trees with increasing tree size. Stand structure consisted of 3.03 (D121) to 8.25 (G3) m² ha^-1 basal area. Leaf area index of 2.8 m² m^-2 was greatest in clone G3 which had maximum stand biomass of 29.18 t ha^-1, though net production (6.91 t ha^-1 y¹) was slightly greater in clone G48. Production efficiency varied from 2.64 to 3.46 kg kg^-1 of leaf biomass in decreasing order of G48, G3 and D121 clones. Litterfall was 0.8 (D121) to 1.92 (G48) t ha^-1 y¹, of which 80% decomposed within a year. Among the interrelationship derived with girth, height and girth increment relations were best fitted by a logarithmic curve. Stand density and biomass were simulated by a polynomial curve of different shape, with increasing tree size. The dependence of stand biomass on the collective effects of basal area and leaf area index was deduced through a multiple regression model. A linear increase in production efficiency was associated with the positive effect of net production and negative effect of leaf production. The study revealed a marginal potential for commercial production unless the long term benefit of soil conservation/land rehabilitation is taken into account.