Pedogenesis by clay dissolution on acid, low-grade metamorphic rocks under mediterranean forests in southern Tuscany (Italy)

Abstract

Pedogenesis by clay dissolution on acid, low-grade metamorphic rocks under mediterranean forests in southern Tuscany (Italy) van Wesemael, B.; Verstraten, J.M.; Sevink, J. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractPedogenesis on acid, low-grade metamorphic rocks under well-developed forests was studied in the meso-mediterranean climatic zone. To that purpose three representative soil profiles on phyllite and sandstone under sclerophyllous oak, pine and heathland were selected. The major soil forming processes consisted of transformation of part of the K-mica (muscovite) to (hydroxy-interlayered) vermiculite and smectite, impoverishment both in major elements (A1, K, Mg and Fe) and fine particles, and redistribution of sesquioxides as organic complexes. These processes indicate clay hydrolysis under acid conditions and subsequent removal of solutes by lateral subsurface flow. The resulting impoverishment of the soil profiles could be mainly attributed to hydrolysis under acid conditions brought about by slow decomposition of organic matter. The proposed mode of pedogenesis deviates strongly from the current concept of fersiallitisation, and is probably restricted to acid parent materials in mediterranean climates where lateral removal of soluble weathering products is ensured throughout the largest part of the year.

Microbial dynamics in Mediterranean Moder humus

“…Moder humus forms are associated to reduced zoological richness (Ponge 2003) and faunal activity limited to the ectorganic horizons, and both, according to Ponge (2003) and Northup et al (1998), represent a strategy of nutrient conservation. Limited incorporation of organic matter in mineral horizons induces a spatial decoupling of mineralisation, in the ectorganic horizons, and root uptake, in the endorganic horizon (van Wesemael et al 1995). This separation of proton production and consumption has been suggested as a major process in mineral soil acidification (Nilsson et al 1982;Ulrich 1983); it leads to a highly specific distribution of nutrient sources for microorganisms and is likely a major control on activities and composition of microbial populations.…”

Alteration, Formation, and Occurrence of Minerals in Soils

“…The resulting smectites are generally Al-rich and hence beidellitic (Ross and Mortland, 1966;Churchman, 1980;Borchardt, 1989), but may also be montmorillonitic (Aragoneses and García-González, 1991). Strong weathering without podzolization can also transform micas to smectites (Stoch and Sikora, 1976;Egashira and Tsuda, 1983;Senkayi et al, 1983;Singh and Gilkes, 1991;van Wesemael et al, 1995), even in Antarctic soils, where smectites were among the transformation products of micas (Boyer, 1975). Smectites formed this way have generally been identified as beidellites.…”

Perspectives in dryland restoration: approaches for climate change adaptation

“…Moderate rock contents positively affect the moisture regime and soil temperature. The presence of rock fragments in the soil can act as preferential water pathways (Van Wesemael et al 1995). A soil surface stone layer can also act as mulch by reducing soil temperature and evapotranspiration, thereby leading to increased water availability, and protect the soil against compaction, runoff, and desiccation (Casals et al 2000;Katra et al 2008;Maestre et al 2003).…”

“…Relative increase in 123 rock fragments in the soil profile may also facilitate the penetration of the wetting front down the soil profile by decreasing the density of fine earth and increasing macropores (Van Wesemael et al 1995); this may also reduce evaporation losses and enhance ground water recharge (Li 2003). A dry well filled with stones (Dry Well), 20-25 cm deep and close to the planted seedling promotes infiltration around the root system before collected water evaporates (Bainbridge 2007).…”