Root CSA-Root Biomass Prediction Models in Six Tree Species and Improvement of Models by Inclusion of Root Architectural Parameters

Abstract

Models were developed for Norway spruce, Sitka spruce, Scots pine, Pedunculate Oak and European Beech to predict the biomass of individual structural roots based on either basal root cross sectional area (rCSA) assessments (basic models) or on rCSA and additional root architectural measurements (multiple models). The material embraces 1257 roots from 337 trees derived from 33 stands. The soil types of the investigation cover sandy podzols, sandy moraine, brown earth, deep peat, and pseudogley, but all species were not represented on all soil types. The models were developed for stands in three dimension classes depending on the average diameter of the stands and for horizontal roots (angle to the surface less than 45°) and vertical roots (angle to the surface greater than or equal to 45°), respectively. Simple models using rCSA near the stump to predict coarse root biomass (logarithmic models) did not account for stand differences in Norway spruce and Sitka spruce. To eliminate these differences, it was necessary to include root taper and vertical root parameters in the models. Variation between stands concerning the regression between rCSA and root biomass was not found for Pedunculate Oak, Scots Pine or European Beech, but the number of stands of these species was also limited compared with Norway spruce and Sitka spruce.

Coarse root architecture of three boreal tree species growing in mixed stands

“…It is possible to estimate the total size of the whole root system using the equations presented in this paper. However, even better estimates might have been obtained by taking into account the variation between the stands through stand adjustments for intercept and slope, as applied by Nielsen and Hansen (2006). Unfortunately, because of the small number of observations per stand, it was not reasonable to construct regression models based on different stands.…”

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

“…Because our objective was to describe tanoak root morphology primarily for prediction of root volume and biomass, we did not attempt to describe aspects of the spatial distribution of roots, such as the angle separating the small fork ends (Kalliokoski et al, 2010) or the horizontal or vertical positioning of roots in the soil (Drexhage et al, 1999). 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).…”

“…Biomass for the severed roots can therefore be determined by applying the regression to the cross-sectional area at the end of all the roots severed during excavation. However, factors such as slope, soil, wind, climate and inter-specific competition from adjacent trees may affect the relationship between root cross-sectional area and mass (Nielsen & Hanson, 2006;Zanetti et al, 2015).…”

“…This approach allows for more accurate estimation of unexcavated root volume or mass and can form the basis of research into factors affecting biomass allocation within root systems (Nielsen & Hanson, 2006). Previous studies have included measurements of individual root segments between forks and descriptions of the root branching patterns (Fitter et al, 1991;Noordwijk et al, 1994;Oppelt et al, 2001;Vercambre et al, 2003;Kalliokoski et al, 2010).…”

“…Previous studies have included measurements of individual root segments between forks and descriptions of the root branching patterns (Fitter et al, 1991;Noordwijk et al, 1994;Oppelt et al, 2001;Vercambre et al, 2003;Kalliokoski et al, 2010). By describing morphology of individual root segments, root morphology for an entire belowground system can be more accurately modeled, and allometric models of belowground biomass derived (Nielsen & Hanson, 2006).…”