In times of global change biomass calculations and the carbon cycle is 
gaining in importance. Forests act as carbon sinks and hence, play a crucial 
role in worlds and forests carbon budgets. Unfortunately, growth models and 
biomass calculations existing so far mainly concentrate on the above-ground 
part of trees. For this reason, the aim of the present study is to develop an 
annually resolved 3D growth model for tree roots, which allows for reliable 
biomass calculations and can later be combined with above-ground models. A 
FARO scan arm was used to measure the surface of a tree-root segment. In 
addition, ring-width measurements were performed manually on sampled cross 
sections using WinDENDRO. The main goal of this study is to model root growth 
on an annual scale by combining these data sets. In particular, a laser scan 
arm was tested as a device for the realistic reproduction of tree-root 
architecture, although the first evaluation has been performed for a root 
segment rather than for an entire root system. Deviations in volume 
calculations differed between 5% and 7% from the actual volume and varied 
depending on the used modeling technique. The model with the smallest 
deviations represented the structure of the root segment in a realistic way 
and distances and diameter of cross sections were acceptable approximations of 
the real values. However, the volume calculations varied depending on object 
complexity, modeling technique and order of modeling steps. In addition, it 
was possible to merge tree-ring borders as coordinates into the surface model 
and receive age information in connection with the spatial allocation. The 
scan arm was evaluated as an innovative and applicable device with high 
potential for root modeling. Nevertheless, there are still many problems 
connected with the scanning technique which have an influence on the accuracy 
of the model but are expected to improve with technical progress.