THE ROOTING BEHAVIOUR OF FOUR AGROFORESTRY SPECIES IN THE WESTERN HIMALAYAN VALLEY REGION

Abstract

The rooting behaviour of four agroforestry species in the northwestern hills of India, viz. Bauhinia purpurea, Grewia optiva, Eucalyptus tereticornis and Leucama leucocephala, was investigated. Polybag-raised seedlings planted at 3 x 3 m on silty clay loam soil at Dehra Dun were excavated by the skeleton method periodically up to 90 months during the winter season. Along with the shoot growth patterns, rooting characteristics of these species were recorded in terms of changes in root length density, root weight, root system sorption zone and vertical and lateral expansions of roots with time. Aboveground biomass was closely related to root length and root biomass. The fast-growing species E. tereticornis and L. leucocephala had relatively more aggressive root systems
than the slow-growing native spp. G. optiva and B. purpurea. At 90 months of age, more than one third of the root length of all the four species was positioned beyond 1 m depth. Bauhinia purpurea and G. optiva show much less root length density at l m depth compared to L. leucocephala and E. tereticornis. Therefore the former two indigenous species are likely to be less competitive with crops in agroforestry systems than the latter two fast-growing species. Bauhinia purpurea with a deep root system and high root:shoot ratio may be a suitable species for slope stabilisation while G. optiva with a shallow root system may be effective for erosion control particularly on terrace risers.