Spatial distribution of the soil carbon pool in a Holm oak dehesa in Spain

Abstract

Aims Dehesas are agroforestry systems characterized
by scattered trees among pastures, crops and/or fallows.
A study at a Spanish dehesa has been carried out
to estimate the spatial distribution of the soil organic
carbon stock and to assess the influence of the tree
cover.
Methods The soil organic carbon stock was estimated
from the five uppermost cm of themineral soil with high
spatial resolution at two plots with different grazing
intensities. The Universal Kriging technique was used
to assess the spatial distribution of the soil organic
carbon stocks, using tree coverage within a buffering
area as an auxiliary variable.
Results A significant positive correlation between tree
presence and soil organic carbon stocks up to distances
of around 8 m from the trees was found. The tree
crown cover within a buffer up to a distance similar to
the crown radius around the point absorbed 30 % of
the variance in the model for both grazing intensities,
but residual variance showed stronger spatial autocorrelation
under regular grazing conditions.
Conclusions Tree cover increases soil organic carbon
stocks, and can be satisfactorily estimated by means of
crown parameters. However, other factors are involved
in the spatial pattern of the soil organic carbon distribution.
Livestock plays an interactive role together with
tree presence in soil organic carbon distribution.