Vertical distribution and radial growth of coarse roots in pure and mixed stands of Fagus sylvatica and Picea abies

Abstract

The vertical distribution of roots greater than 2 mm diameter was determined from digital images covering 116-m2 profile walls in soil pits in pure stands of European beech (Fagus sylvatica L.) and of Norway spruce (Picea abies (L.) Karst.) and in a mixed stand of both species. Radial root growth was assessed for roots greater than 5 mm diameter by growth ring analysis. Beech roots showed maximum density at the 10- to 20-cm depth, whereas the density of spruce roots decreased exponentially with increasing soil depth. Roots of both species reached the maximum excavation depth (1 m) in their monospecific stands. However, the root system of spruce was shallower in the mixture with beech, where large roots (diameter (d) >20 mm) were limited to the upper 10 cm. Beech roots reached the same rooting depth as in the pure stand but showed higher root densities in deeper soil layers. Neither root diameter nor root growth of any species was correlated with soil depth. Radial root growth of beech exceeded that of spruce significantly in both pure and mixed stands. Radial growth rate of beech roots further increased when mixed with spruce. The enhancement of beech root growth in the mixed stand suggests a higher belowground competitive ability of beech compared with spruce; as a result the spruce root system developed even shallower in the mixed versus in the pure stand.

Non-Destructive Analysis of the Root System and Tree Growth Parameters

“…Several authors could show correlations between root size and aboveground growth parameters. Drexhage and Colin (2001) estimated root system biomass from the diameter at breast height, while Schmid and Kazda (2001) also found a correlation between vertical distribution of roots and tree growth. The relationship between crown size and root expansion in this study is not as strong, but indicates that there is a relationship between both variables.…”

Analysis of Spatial Point Patterns in Microscopic and Macroscopic Biological Image Data

“…Trench soil profile walls can be used for the assessment of two-dimensional root distributions, regarding the roots on the wall as points of different diameter. A new method provided (x,y)-coordinates of each root greater than 2 mm ( [41]). Using this method, small roots with a diameter between 2 mm and 5 mm were examined in 19 pits on altogether 72 m 2 of soil profiles on monospecific stands of European Beech and of Norway Spruce.…”

“…For details of site description, pit excavation and root mapping and already attained results, see [41]. Our investigations are based upon this article and thus only a short summary of the most important facts is given.…”

“…From [41] it was already known that the depth densities of the roots of Norwegian Spruce and European Beech can be approximated by exponential and gamma distributions respectively. The data has been homogenized with respect to the vertical axis in oder to allow the assumptions of stationarity and isotropy for models of generating point processes.…”

“…While the point patterns regarded in the first application are three dimensional, the second application reveals planar point patterns having a vertically inhomogeneous structure. For a more extensive description of the studied cases, the reader is referred to [4], [5], and [16], [41], [42], respectively.…”