Root and shoot interactions in a tropical integrated crop–livestock–forest system

Integrated crop–livestock–forest systems (ICLFS) have potential advantages compared to monoculture, but most studies quantifying plant biomass in integrated production systems, have quantified only the aboveground component rather than the total biomass. The objective of this study was to investigate the ecological interactions of Eucalyptus trees intercropped with palisade grass in a tropical region. The study was conducted in an 8-year-old ICLFS in which Eucalyptus trees were introduced into a palisade grass pasture [Urochloa brizantha (Hochst. Ex A. Rich.) R. Webster ‘Marandu’]. Samples were collected at four locations from the Eucalyptus trees: 0.0 (planting line), 2.0, 4.0, and 6.0 m (middle of the plots). A monoculture palisade grass pasture was included for comparison. The addition of Eucalyptus in the pasture reduced the forage yield, root length density, root density and root diameter of palisade grass close to the Eucalyptus trees. Eucalyptus roots were more abundant near the trees, and decreased with distance from the tree at soil depths up to 1.0 m. The total amount of roots decreased by 36 % with the addition of the forest component compared with the monoculture pasture, i.e., 11.6 Mg ha−1 in the ICLFS compared with 18.4 Mg ha−1 in the pasture. In the ICLFS, the proportion of palisade grass roots in the soil profile increased with distance from the tree line. However, the high degree of competition in root development in the ICLFS resulted in 20% lower root length and fine roots densities compared with monoculture pasture in the upper 0–0.20 m soil layer.