BIOMASS PRODUCTION AND DISTRIBUTION OF ROOTS IN 3 STANDS OF POPULUS-DELTOIDES

Agroforestry involves matching trees and crops so that they complement one another and share the available resources effectively in order to attain maximum productivity. A knowledge of biomass production and the distribution of root systems therefore has considerable practical value. Above ground and below ground biomass production and the distribution of coarse and fine roots were studied in 9-year-old Populus deltoides, planted at a spacing of 2 m x 2 m, 4 m x 4 m and 6 m x 6 m, in the farm area of Haryana Agricultural University, Hisar. The tree densities were 2250, 531 and 208 per hectare in the stands of 2 m x 2 m, 4 m X 4 m and 6 m X 6 m spacing, respectively. The total biomass (both above and below ground) varied from 71.50 tons ha-1 to 251.50 tons ha-1, depending on the tree density. Among the different tree components, stemwood contributed the maximum biomass (66.3-71.3%), and the biomass was in the order of stem > root > branches > leaves. Patterns of root distribution showed that most of the coarse roots were distributed in the top 30 cm of soil, whereas fine roots were concentrated in the top 15 cm. Coarse root biomass decreased with an increase in spacing from 29. 8 tons ha-1 in the stand of 2 m x 2 m to 5.6 tons ha-1 in the stand of 6 m X 6 m. In contrast fine root biomass increased significantly (P > 0.05) from 13.8 to 2 3. 0 tons ha-1 in the stands of 2 m X 2 m and 6 m X 6 m, respectively. No significant difference was observed in the horizontal distribution of fine roots at different distances from the tree rows at a particular depth in any of the stands. Total below ground biomass was equal in the stands of 4 m X 4 m and 6 m X 6 m, although the former had twice as much above ground biomass than the latter. The shoot: root ratio decreased with an increase in spacing. The study indicates that the bulk of the roots of poplar are found near the surface, and hence there may be root competition with agricultural crops.