Contrasting rooting patterns of some arid-zone fruit tree species from Botswana – II. Coarse root distribution

Abstract

Spatial coarse root distribution of the in situ grown species Strychnos cocculoides BAK., Strychnos spinosa LAM. (Loganiaceae), Vangueria infausta BURCH. (Rubiaceae) and Grewia flava DC. (Tiliaceae) was investigated. The woody roots provide the scaffolding for fine roots, and thus underpin potential competition with fine roots of other species. We developed a method for quantitative description of spatial patterns of coarse roots and correlated fine root distribution with the spatial arrangement of the coarse root systems. In order to estimate different exploration and exploitation strategies, we used the spatial distribution of structural roots within the 'individual soil volumes' (ISV) of each root system, and compared the results with other published parameters. We defined a new parameter, ''generalized efficiency of exploitation'' GEE(/), unifying different notions from the literature. Among all the investigated species and dependent on the considered parameter, either Vangueria infausta or Grewia flava had the highest mean values of exploration, hence they could clearly be separated from both Strychnos species. For the exploitation indices, no significant differences were found. However, the generalized efficiency of exploitation GEE(/) was again different between the species. For correlations between coarse and fine roots, the restriction to the ISV was useful to increase the strength of correlations.

Assessing and analyzing 3D architecture of woody root systems, a review of methods and applications in tree and soil stability, resource acquisition and allocation

“…However, as for Fitter's topology, current models may not be adapted to large and complex root systems which are composed of different root types (Oppelt et al 2005;Danjon et al 2005). In current fractal branching models only the parameter variation by branching order (Salas et al 2004), or in two root classes (horizontal and vertical -WanFBA -van Noordwijk and Mulia 2002) is taken into account, not the root type.…”

“…As they are branching from the coarse roots, the relationship between the spatial distributions of both types of roots can be assessed. This was done on an individual tree basis on isolated trees by Oppelt et al (2005), by a combination of full coarse root architecture 3D digitizing and the sampling of 75 soil cores per tree on a grid for fine root measurements. The spatial distribution relative to the depth and the distance to the tree can also be obtained at the stand level by comparing the fine root content in cores and the spatial distribution of the coarse roots obtained by 3D digitizing (see the 2D plot in Danjon et al 1999a, b).…”

“…Oppelt et al (2000Oppelt et al ( , 2001Oppelt et al ( , 2005 compared root architecture for four tropical fruit tree species grown under arid conditions using 3D digitising data. Root length and volume, mean inter-lateral length, topological, fractal dimension and fractal branching parameters were computed for each root system.…”

“…It includes growth of the shoots and dynamic assimilate allocation to roots and shoots. The spatial distribution of structural root systems was assessed by Oppelt et al (2005) from 3D coarse root architecture data. They computed an "exploration index" which is the proportion of 1 dm 3 voxels occupied by any root and an "exploitation index" which is the proportion of voxels occupied by an amount of roots larger than a given threshold.…”

Tree roots in a changing world

“…To obtain coarse root data, either trees are excavated (e.g., Soethe et al 2006;Oppelt et al 2005) or the roots investigated by ground penetrating radar (e.g., Barton and Montagu 2004;Butnor et al 2003). While radar imaging can mainly be used for biomass estimation in specifi c types Table 3.…”