2 research outputs found
Biogeochemical Proxies of Anthropic Impact in Mediterranean Forest Soils
12 páginas, 7 tablas y 3 figurasQuantitative changes in soil organic matter (SOM) from undisturbed Mediterranean forests and
neighbouring deforested sites were assessed by analysing soil lipids and humic acids (HAs), in total
studying 80 variables. Changes in the composition of free lipids reflected vegetation types, whereas HAs
analysed by visible and 13C NMR spectroscopy, sodium perborate degradation and Curie-point
pyrolysis indicated the extent of structural alteration of lignin in soil. The molecular fractions released
by degradation techniques applied to HAs showed that demethoxylation and oxidation were associated
with the removal of forest vegetation, and the aromatic compounds consisted mainly of
methoxyphenols and benzenecarboxylic acids. Decreased concentration of alkanes and increased
amounts of alcohols were observed after removal of forests. The chain lengths of alkyl compounds also
tended to decrease. In forest soil, there was a series of diterpene resin acids, whereas in pasture soil
steroids from animal origin and a root-derived triterpenoids with friedelan structure were found. In
relation to the total quantity and quality of soil C, the overall chemical descriptors indicated that
clearing and cultivation (semiarid cereal fields) lead to intense mineralization of SOM (mainly
particulate, free organic matter) but the residual humic substances have enhanced maturity in terms of
structural condensation and potential resilience. Conversely, the cleared forest soil under pasture had a
comparatively higher potential for C sequestration, but the HA characteristics suggested selective
preservation of plant biomacromolecules directly incorporated as underground biomass.The authors thank the Spanish Ministry of Science and
Innovation (MICINN) for the Project CGL2008-04296 ⁄ BTE.
Dr. Ana Piedra Buena was contracted under the I3P Program
at CCMA-CSIC, with financial support from European
Social FundPeer reviewe