Publication: Sheet erosion rates determined by using
dendrogeomorphological analysis of exposed tree
roots: Two examples from Central Spain
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Publication Date
2005
Authors
Bodoque del Pozo, José María
Díez Herrero, Andrés
Rubiales Jiménez, Juan Manuel
Godfrey, Andrew E.
Pedraza Gilsanz, Javier de
Carrasco González, Rosa María
Sanz Santos, Miguel Angel
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Publisher
Elsevier B.V.
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Abstract
This paper describes the determination of sheet erosion rates by using dendrogeomorphological
methods on exposed tree roots. Two sites on the northern slope of the Guadarrama Mountains,
Central Spain, were studied: a popular trail in a Scots pine forest (Senda Schmidt, Valsaı´n) growing
on granites and gneisses, and an open holm-oak forest on granitic slopes (Monterrubio). These sites
were selected because they showed high denudation morphologies due to accelerated soil-erosion
processes caused by human influence (trampling by continuous trekking and overgrazing), resulting
in exposed roots. The method applied is based on the morphological pattern of roots, defined by the
growth-ring series of the sampled roots. In order to confirm the validity of the criteria used and to
make the estimations of erosion more accurate, several anatomical indicators of exposed and nonexposed
Pinus sylvestris roots were characterized.
The study entailed a statistical analysis of exposure time and erosion depth. The influence of
environmental factors affecting the variation in velocity of the erosion processes was also examined.
With a significance level of 95%, the mean erosion rates were in the range of 1.7–2.6 mm/year (29–
44 t/ha/year) on Senda Schmidt over the last 101 years, and 1.1–1.8 mm/year (19–31 t/ha/year) in
Monterrubio over the last 42 years. Using a multifactor analysis of variance, we observed a change in
the erosion rates as a function of position on the path along Senda Schmidt. In Monterrubio,
however, we reached no significant conclusions, apart from an inverse relationship between erosion
and slope gradient that was difficult to interpret.
Climate conditions in Senda Schmidt and the accuracy of dating Scots pine indicate that the
evaluation on P. sylvestris roots is fairly reliable, which is not the case for oak roots. Although this
paper is based on the application of an existing method, its novelty lies in being the first attempt in
Spain to estimate dacceleratedT sheet erosion rates (due to recreational activities and overgrazing)
using dendrogeomorphological techniques, supplemented by anatomical indicators for P. sylvestris.