There are significant differences in root anatomy, caused by different kinds of erosive processes. Taking into account that root structure also differs according to the distance to the surface, the study of roots is not limited to determining the date of their initial exposure. A combination of the variations and additional features present in root structures, such as the appearance of reaction wood, enables the reconstruction of the changing conditions over time that resulted in root exposure.
In general, specific anatomical features can be related to (i) sudden erosive events causing an immediate and complete change of the size and shape of EW and LW cells, and (ii) continuous denudation causing a gradual change of LW cells first. Although the causal factors are still in part uncertain, these changes are not randomly distributed in the growth rings. We are even able to discern the type of exposure from the root structure.
At about 5 cm beneath the soil surface, growth rings appear "stem like". This implies that a stem-like shape of the growth rings in roots can no longer be interpreted as a sign of exposure. Furthermore, the notion that light is the main factor causing anatomical changes in roots has become questionable.
Many uncertainties still exist concerning the degree of influence of some environmental factors on the growth of roots. However, the analysis of root structure in relation to the distance to the soil surface offers new and exiting possibilities for the reconstruction of e.g. soil erosion.