Spatial distribution of coarse roots biomass and carbon in an olive intensive orchards: effect of mechanical harvesting method

Coarse roots, the skeleton of the root system, are of primary importance for soil exploration and plant anchorage and only recently have ] been recognized as playing a major role in “long-term” carbon sequestration. Despite this role, the 3D architecture of coarse roots represents a gap in knowledge on the biomass and carbon allocation within the root system and, consequently, below-ground carbon sequestration capacity. Using a semi-automatic 3D digitizing approach (3 Space Fastrak plus Long Ranger), the 3D distribution in the soil environment of coarse root biomass and C content and how these parameters were affected by manual and mechanical (trunk shaker) harvesting methods were quantified in a high-density olive orchard. The below-ground C content at the stand level was estimated to be 11.93 Mg C ha-1 and distributed at deeper soil layers (45-60 cm) in the form of 1st- and 2nd-order branching roots. The present study also revealed that the mechanical harvesting method significantly increased both the angle of growth (0◦ = vertically downwards) of 1st-order lateral roots and the stump biomass, but neither the biomass allocation nor the C content was increased within the first three branching orders .