Master Degree of European Forestry
This study investigates if Tectona grandis, Casuarina montana and Eucalyptus camaldulensis
planted in mixture with Acacia mangium would send their roots toward Acacia in attempt
to benefit from its symbiotic nitrogen fixation ability and also to investigate if the roots of
mixed tree species would occupy different vertical soil layers for better utilization of site
resources. A soil core method was used for root and soil sampling in a 22 months old mixed
stand of E. camaldulensis (E), C. montana (C), T. grandis (T) and A. mangium (A) in a 1A:8A;
1A:8E; 1A:8T; 1A:8C; 1E: 8A; 1T:8A and 1C: 8A species combination replicated at three
sites. Lateral distribution showed a decreasing root biomass with increasing distance from
the tree stem. The highest total root biomass was obtained at 20 cm distance reaching
306.05 g m -2 for Acacia, 229.19 g m -2 for Eucalyptus 156.5 g m -2 for Tectona and 127.0 g m -2
for Casuarina. The lowest total root biomass was observed at 180 cm distance reaching
5.44 g m -2 for Acacia and 0.01 g m -2 for Eucalyptus, Casuarina and Tectona. Lateral spread of
other species was higher in the upper layer (0-10 cm) with high density of A. mangium and
high in the lower layer (10-20 cm) with low density of A. mangium in the species
combination. Vertical distribution revealed a decrease in root biomass with increasing soil
depth for all species except T. grandis. Mean root biomass decreased from 162.41 (acacia)
to 4.58 g m -2 (teak) in the 0-10 cm layer to 90.26 (acacia) to 5.40 (casuarina) g m -2 in the
10-20 cm layer. Also fine root biomass was high in the upper layer and coarse root biomass
was high in the lower layer. It is concluded that, there was not sufficient evidence of other
species sending their roots toward A. mangium but there was clear vertical niche
separation between A. mangium and other species, particularly with T. grandis