Tree Growth, Biomass and Productivity of Wheat Under Five Promising Clones of Populus deltoides in Agrisilviculture System

摘要

Variations in growth and above- and below-ground biomass of five promising clones (G3, G48, 65/27, D121 and S7C1) of Populus deltoides and their effect on productivity of wheat under agrisilviculture system were evaluated. Monoclonal plantations were established in a randomized block design with three replications. Diameter at breast height (dbh) and tree height were consistently higher in clone 65/2 7 and lowest in clone S7C1. Total biomass varied from 48.5 to 62.2 Mg ha1 in 6-year old clones; it followed the order 65/27 > D121 > G48 > G3 > S7C1. Stem wood accounted for 60.4-68.9% of total biomass, followed by coarse roots (12.2-18.9%), branches (12.3-15%), leaves (3.02-6.9%) and fine roots (1.5-2.7%). Grain yield of wheat was highest (3.66 Mg ha~(-1)) in sole crop and decreased by 15-30.3% under different clones. The straw yield also showed similar trend. The reduction of grain and straw yield of wheat in clones was in order: S7C1 < G3 < D121< 65/27 < G48. Available N, P and K in the soil improved significantly after 6 years of poplar planting. N was highest under clone S7C1 and lowest under clone G48, while P was lowest under clone 65/27 and higher under clone G3. K was higher in clone S7C1 and lower in clone 65/27. At 0-20 cm depth, N increased from 14.9 to 24.1 %, P from 17.2 to 23.3% and K from 3.1 to 5.1% under different clones after 6 years of planting.