@article{BehrensBouchezSchuessleretal.2015,
  author    = {Behrens, Ricarda and Bouchez, Julien and Schuessler, Jan A. and Dultz, Stefan and Hewawasam, Tilak and von Blanckenburg, Friedhelm},
  title     = {Mineralogical transformations set slow weathering rates in low-porosity metamorphic bedrock on mountain slopes in a tropical climate},
  series = {Chemical geology : official journal of the European Association for Geochemistry},
  volume    = {411},
  journal   = {Chemical geology : official journal of the European Association for Geochemistry},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0009-2541},
  doi       = {10.1016/j.chemgeo.2015.07.008},
  pages     = {283 -- 298},
  year      = {2015},
  abstract  = {In the Sri Lankan Highlands erosion and chemical weathering rates are among the lowest for global mountain denudation. In this tropical humid setting, highly weathered deep saprolite profiles have developed from high-grade metamorphic charnockite during spheroidal weathering of the bedrock. The spheroidal weathering produces rounded corestones and spalled rindlets at the rock-saprolite interface. We used detailed textural, mineralogical and chemical analyses to reconstruct the sequence of weathering reactions and their causes. The first mineral attacked by weathering was found to be pyroxene initiated by in situ Fe oxidation. Volumetric calculations suggest that this oxidation leads to the generation of porosity due to the formation of micro-fractures allowing for fluid transport and subsequent dissolution of biotite and plagioclase. The rapid ensuing plagioclase weathering leads to formation of high secondary porosity in the corestone over a distance of only a few cm and eventually to the final disaggregation of bedrock to saprolite. The first secondary phases are oxides or amorphous precipitates from which secondary minerals (mainly gibbsite, kaolinite and goethite) form. As oxidation is the first weathering reaction, the supply of O-2 is a rate-limiting factor for chemical weathering. Hence, the supply of O-2 and its consumption at depth connects processes at the weathering front with those at the Earth's surface in a feedback mechanism. The strength of the feedback depends on the relative weight of advective versus diffusive transport of O-2 through the weathering profile. The feedback will be stronger with dominating diffusive transport. The low weathering rate is explained by the nature of this feedback that is ultimately dependent on the transport of O-2 through the whole regolith, and on lithological factors such as low bedrock porosity and the amount of Fe-bearing primary minerals. Tectonic quiescence in this region and low pre-development erosion rate (attributed to a dense vegetation cover) minimize the rejuvenation of the thick and cohesive regolith column, finally leading to low denudation rates. (C) 2015 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{NguyenMehargCareyetal.2019,
  author    = {Nguyen, Minh N. and Meharg, Andy A. and Carey, Manus and Dultz, Stefan and Marone, Federica and Cichy, Sarah Bettina and Tran, Chinh T. and Le, Giang H. and Mai, Nga T. and Nguyen, Thinh T. H.},
  title     = {Fern, Dicranopteris linearis, derived phytoliths in soil},
  series = {European journal of soil science},
  volume    = {70},
  journal   = {European journal of soil science},
  number    = {3},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {1351-0754},
  doi       = {10.1111/ejss.12754},
  pages     = {507 -- 517},
  year      = {2019},
  abstract  = {Ferns are among the most popular groups of plants in the tropics and subtropics, and their role as carbon sequestrators has been widely recognized. However, there is little understanding of the silicaceous structures (phytoliths) of ferns, rate of phytolith turnover, the consequences for organic matter sequestered in phytoliths and consequences for other soil properties. In the study reported here, high-resolution X-ray tomographic microscopy and chemical characterization were applied to examine the traits of phytoliths of the fern Dicranopteris linearis (Burm.f.) Underw. (D. linearis), with a focus on their dissolution properties and accumulation in northern Vietnamese soils in relation to soil properties. Tomographic images revealed an inter-embedding structure of silica and organic matter, especially in leaf-derived material. We propose that organic matter and silica can preserve each other against decomposition. In batch experiments, there was a relatively small rate of dissolution of phytoliths with dry ashing and subsequent H2O2 treatment. Silicon (Si) dissolution for D. linearis phytolith samples was much less than that for rice phytoliths. Despite the fact that the aluminum (Al) content was large in D. linearis leaves, batch dissolution data did not confirm a relation between Al and the slow rate of phytolith dissolution. The soil phytolith content varied from 0.9 to 7.5 g kg(-1) in the topsoil across the mountainous areas in northern Vietnam, whereas it tended to be smaller in the subsoil. The data indicate a relation between phytolith and soil organic matter, clay content, oxalate-soluble Al and electrical conductivity, suggesting that these soil properties are among the important factors affecting the size of the soil phytolith Si pool. Highlights},
  language  = {en}
}