Descendant root volume varies as a function of root type: estimation of root biomass lost during uprooting in Pinus pinaster

Abstract

Root systems of woody plants generally display a strong relationship between the cross-sectional area or cross-sectional diameter (CSD) of a root and the dry weight of biomass (DWd) or root volume (Vd) that has grown (i.e., is descendent) from a point. Specification of this relationship allows one to quantify root architectural patterns and estimate the amount of material lost when root systems are extracted from the soil. However, specifications of this relationship generally do not account for the fact that root systems are comprised of multiple types of roots. We assessed whether the relationship between CSD and Vd varies as a function of root type. Additionally, we sought to identify a more accurate and time-efficient method for estimating missing root volume than is currently available. We used a database that described the 3D root architecture of Pinus pinaster root systems (5, 12, or 19 years) from a stand in southwest France. We determined the relationship between CSD and Vd for 10,000 root segments from intact root branches. Models were specified that did and did not account for root type. The relationships were then applied to the diameters of 11,000 broken root ends to estimate the volume of missing roots. CSD was nearly linearly related to the square root of Vd, but the slope of the curve varied greatly as a function of root type. Sinkers and deep roots tapered rapidly, as they were limited by available soil depth. Distal shallow roots tapered gradually, as they were less limited spatially. We estimated that younger trees lost an average of 17% of root volume when excavated, while older trees lost 4%. Missing volumes were smallest in the central parts of root systems and largest in distal shallow roots. The slopes of the curves for each root type are synthetic parameters that account for differentiation due to genetics, soil properties, or mechanical stimuli. Accounting for this differentiation is critical to estimating root loss accurately.

Recent advances quantifying the large wood dynamics in river basins: New methods and remaining challenges

“…In addition, root strength generally varies with root diameter, with different strength-diameter relationships apparent for different tree species [Simon and Collison, 2002;Pollen et al, 2004]. Finally, the 3-D distribution of root position, orientation, and size defines the architectural structure of the root system [Danjon et al, 2013].…”

Forest management and carbon sequestration in the Mediterranean region: A review

“…Moreover, root loss in sampling procedures can account for up to 35% in the case of Fagus sylvatica (Le Goff & Ottorini 2001), 15% in maritime pine (Danjon et al, 2013) or 23% in some tropical forests (Niiyama et al, 2010). It has been suggested that the degree of loss is dependent on tree size (the larger the tree, the greater the root biomass loss) and that losses are greater in stony soils and/or when the species shows a deeper rooting pattern (Danjon et al, 2013). Accurate estimation is necessary in order to determine belowground biomass carbon stocks.…”

Tanoak (<i>Notholithocarpus densiflorus</i>) Coarse Root Morphology: Prediction Models for Volume and Biomass of Individual Roots

“…Nielsen& Hanson (2006) found that rooting depth helped explain variations in root taper of six tree species. We did not record depth of each tanoak root segment, but our finding that taper was affected by root orientation and size could be exploited to design a sampling protocol to collect different-sized roots at different depths and examine the relationship between root depth and taper (Danjon et al, 2013).…”

“…An excavator can be used to remove the root-soil plate (a mass of woody tissue connecting the stem to the lateral roots), but hand tools or an air spade are required to excavate smaller more fragile roots (Bingham et al, 2001;Lavigne & Krasowski, 2007). Excavating large root systems is particularly laborious and loss of some root biomass is likely (Böhm, 1979;Danjon et al, 2013). Deriving total belowground biomass estimates from the excavated portions of a root system requires development of predictive models to account for the roots lost during the excavation process (Richardson & Dohna, 2003;Danjon et al, 2013).…”

“…Excavating large root systems is particularly laborious and loss of some root biomass is likely (Böhm, 1979;Danjon et al, 2013). Deriving total belowground biomass estimates from the excavated portions of a root system requires development of predictive models to account for the roots lost during the excavation process (Richardson & Dohna, 2003;Danjon et al, 2013).…”