The variations of [X.sub.lf], [X.sub.fd] and [X.sub.fd]% and their correlations demonstrate that: (i) the pedogenetic
evolution of the top soil is the fundamental process responsible of the susceptibility enhancement, and (ii) the MS enhancement is fostered especially in preserved reforested areas and lesser in pasture and cultivated land; it seems to decreases with increasing human activity.
Soil development is connected with different types of specific pedogenetic
The development of these highs is further supported by the presence of pedogenetic
profiles (laterites: Marini, 1984) in areas where the Genna Selole Fm is almost absent, while the first Middle Jurassic deposits are impure carbonates of the Ussassai-Perdasdefogu lithofacies; these are interpreted as the areas where the continental conditions persisted for a longer timespan.
(2007), who reported distinctive patterns of pedogenetic
carbonate values related to depth in Vertisols on the coastal prairies of Texas and established that climate is a determining factor for Vertisol formation in the Texas Gulf Coast, evidence that is in keeping with the features of the Vertisols of the present study.
From the pedogenetics
processes specific to the area, with high intensity there are manifested the bioaccumulation and the alteration; that is proved by the soil cover where cernisols are preponderant and only on restricted areas we may talk about eluviation-iluviation, gleization-pseudogleization, as well as salinization-alkalization.
It is possible that pedogenetic
factors are responsible for this rejuvenating effect, a phenomenon already addressed by Pessenda et al.
After biological rehabilitation, it can develop into a soil as a result of contemporary pedogenetic
processes that take place under direct human observation.
At the end of the 1990s we carried out recurrent studies in some areas of the International Biological Programme to establish contemporary pedogenetic
changes in several soil types (Reintam 1999, 2000, 2001a).
The limitation of this technique lies in the fact that variation to the depth of a restrictive horizon can be caused by several pedogenetic
factors other than soil erosion; e.g., position along the toposequence.
Soil-forming factors, terrain covariates and pedogcnctic importance NDVI, normalised difference vegetation index; DEM, digital elevation model Soil-forming Terrain covariates Pedogenetic
importance factors Organisms NDVI Vegetation, water and organic contents Relief DKM, slope, curvature, Weathering, microclimate compound topographic characteristics, index, Euclidean moisture and other distance from stream soil properties networks, Landform map Parental Geology map, clay Mineralogy, erosion material minerals index, iron susceptibility, soil and time oxide index fertility (^) Adapted from McKenzie and Ryan (1999) and Chagas (2006).
The study method of chronosequences has been efficient to describe the pedogenetic
evolution of the soil in time scales from a few to thousands of years.
Formation of high IS and smectite in the Upper Cretaceous and younger sediments can be explained by their pedogenetic
detrital formation in the shallow sediments.