Root distribution, orientation and root length density modelling in Eucalyptus and evaluation of associated water use efficiency

A mathematical model was used in this study to simulate the root architecture comprising of both structural and geometric components, to reproduce the morphogenetic behaviour of the commercially important Eucalyptus genotypic root distribution pattern over time. Profile trench wall method was used to map the root intersection density of six genotypes over a period of 2 years and subsequently root length density was modelled from the root impact data, along with actual measurements from soil cores. Clones of vegetative origin showed higher penetration and proliferation capacity than those of seedling origin. Eucalyptus tereticornis and Eucalyptus camaldulensis showed greater horizontal and vertical spread than reciprocal hybrids. A major portion of the root system was confined in the 0–0.3 m depth and all the genotypes showed decreasing root length density with increasing depth. The estimated depth at which 50% of the roots were concentrated varied between 10 and 30 cm. Water use efficiency of the plants showed a positive correlation with penetration capability thereby suggesting the possible reclamation strategies by identifying potentially deep-rooted genotypes. The modelled root distribution patterns from the present study could be incorporated into agroforestry systems for better tree-crop compatibility as well as for site-specific selection of genotypes.