Papers by Jean-Thomas Cornelis
The spatial distribution of soil constituents at the micrometer scale is of great importance to u... more The spatial distribution of soil constituents at the micrometer scale is of great importance to understand processes controlling the formation of micro-aggregates and the stabilization of organic carbon. Here, the spatial distribution of organic and mineral constituents in Podzol horizons is studied by concerted measurements of (i) the content of various forms of Fe, Al, Si and C determined by selective extraction in the fine earth fraction of soil (f < 2 mm); (ii) the elemental composition of the clay fraction (f < 2 μm) with lateral resolution using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and with surface selectivity using X-ray photoelectron spectroscopy (XPS); (iii) the specific surface area (SSA) of fine earth and clay fractions by krypton physisorption. The SSA of the fine earth in illuvial horizons is predominantly due to finely divided Fe oxides, including goethite, characterized by an equivalent particle size of about 10 nm. Kaolinite platelets of about 2 μm size account for a large volume proportion in the clay fraction but have a minor contribution to SSA. Fe oxides and organic matter (OM) are intimately associated. Heterogeneity at the μm scale is created by local variations in the relative amounts of kaolinite and Fe-OM associations. These two kinds of physical entities are in random mixture. Moreover, variation of C/Fe atomic ratios reveals sub-μm scale heterogeneity. The latter is due to variation in the relative proportion of organic compounds and Fe oxides, indicating that aggregation of nanoparticles, and not only mere adsorption or pore filling, plays a role in these associations. In this regard, our results highlight that OM associated with Fe protects Fe oxides against physical displacement and that part of this associated OM is oxidizable by NaOCl treatment. These findings demonstrate that the concept of OM stabilization through association with Fe must be revisited when considering the sub-μm scale level because fine Fe oxide particles can be easily dispersed during oxidation of associated carbon. Combination of physical fractionation and micro-analysis (e.g. SEM-EDS, vibrational spectroscopy) offer promising perspectives to clarify the relationship between chemical composition and sub-μm scale architecture, and to better understand soil processes.
Biogenic silica (BSi) precipitates in leaves and needles of trees and contributes to the amorphou... more Biogenic silica (BSi) precipitates in leaves and needles of trees and contributes to the amorphous silica fraction (ASi) in soil through litterfall. In forest ecosystem, the ubiquitous and significant ASi pool could influence the Si mass-balance at watershed scale, which plays a major in the global biogeochemical processes. Thus, an accurate quantification of the ASi pool in forest soils is a mandatory step. Here, we examined the distribution of the ASi in an acid brown soil under various tree species (Douglas fir, Black pine and European beech) established in identical soil and climate conditions. We quantified the ASi concentration in soil with alkaline extraction (Na 2 CO 3 0.1M). The mean content of ASi in humus layer significantly decreases in the sequence (mg ASi / g): Douglas fir (14.5) > European beech (11.8) > Black pine (5.4). Tree species impacts the ASi pool in the humus layer through different uptakes of H 4 SiO 4 0 and accumulation of BSi in leaves and needles. I...
Biogeosciences, 2015
The role of eroding landscapes in organic carbon stabilization operating as C sinks or sources ha... more The role of eroding landscapes in organic carbon stabilization operating as C sinks or sources has been frequently discussed, but the underlying mechanisms are not fully understood. Our analysis aims to clarify the effects of soil redistribution on physical and biogeochemical soil organic carbon (SOC) stabilization mechanisms along a hillslope transect. The observed mineralogical differences seem partly responsible for the effectiveness of geochemical and physical SOC stabilization mechanisms as the mineral environment along the transect is highly variable and dynamic. The abundance of primary and secondary minerals and the weathering status of the investigated soils differ drastically along this transect. Extractable iron and aluminum components are generally abundant in aggregates, but show no strong correlation to SOC, indicating their importance for aggregate stability but not for SOC retention. We further show that pyrophosphate extractable soil components, especially manganese, play a role in stabilizing SOC within non-aggregated mineral fractions. The abundance of microbial residues and measured 14 C ages for aggregated and nonaggregated SOC fractions demonstrate the importance of the combined effect of geochemical and physical protection to stabilize SOC after burial at the depositional site. Mineral alteration and the breakdown of aggregates limit the protection of C by minerals and within aggregates temporally. The 14 C ages of buried soil indicate that C in aggregated fractions seems to be preserved more efficiently while C in nonaggregated fractions is released, allowing a re-sequestration of younger C with this fraction. Old 14 C ages and at the same time high contents of microbial residues in aggregates suggest either that microorganisms feed on old carbon to build up microbial biomass or that these environments consisting of considerable amounts of old C are proper habitats for microorganisms and preserve their residues. Due to continuous soil weathering and, hence, weakening of protection mechanisms, a potential C sink through soil burial is finally temporally limited.
Understanding Root Uptake of Nutrients, Toxic and Polluting Elements in Hydroponic Culture
Hydroponics - A Standard Methodology for Plant Biological Researches, 2012
High concentrations of amorphous, biogenic Si (BSi) in the sediment of a small high-latitude lake: implications for biogeochemical Si cycling and for the use of BSi as a paleoproxy
Aquatic Sciences, 2014
Volcanic Soils
The Encyclopedia of Volcanoes, 2015
Environmental science & technology, 2015
Organochlorine molecules (Clorg) are surprisingly abundant in soils and frequently exceed chlorid... more Organochlorine molecules (Clorg) are surprisingly abundant in soils and frequently exceed chloride (Cl(-)) levels. Despite the widespread abundance of Clorg and the common ability of microorganisms to produce Clorg, we lack fundamental knowledge about how overall chlorine cycling is regulated in forested ecosystems. Here we present data from a long-term reforestation experiment where native forest was cleared and replaced with five different tree species. Our results show that the abundance and residence times of Cl(-) and Clorg after 30 years were highly dependent on which tree species were planted on the nearby plots. Average Cl(-) and Clorg content in soil humus were higher, at experimental plots with coniferous trees than in those with deciduous trees. Plots with Norway spruce had the highest net accumulation of Cl(-) and Clorg over the experiment period, and showed a 10 and 4 times higher Cl(-) and Clorg storage (kg ha(-1)) in the biomass, respectively, and 7 and 9 times higher...
Frontiers in plant science, 2014
The continental bio-cycling of silicon (Si) plays a key role in global Si cycle and as such partl... more The continental bio-cycling of silicon (Si) plays a key role in global Si cycle and as such partly controls global carbon (C) budget through nutrition of marine and terrestrial biota, accumulation of phytolith-occluded organic carbon (PhytOC) and weathering of silicate minerals. Despite the key role of elemental composition of phytoliths on their solubility in soils, the impact of plant cultivar and organ on the elemental composition of phytoliths in Si high-accumulator plants, such as rice (Oryza sativa) is not yet fully understood. Here we show that rice cultivar significantly impacts the elemental composition of phytoliths (Si, Al, Fe, and C) in different organs of the shoot system (grains, sheath, leaf and stem). The amount of occluded OC within phytoliths is affected by contents of Si, Al, and Fe in plants, while independent of the element composition of phytoliths. Our data document, for different cultivars, higher bio-available Si release from phytoliths of leaves and sheaths...
Evaluation of silicon stocks and uptake in five forest stands on an acid brown soil
Public debate, collective learning process and soil-plant system expertise: when scientific knowledge becomes socially distributed
Forest tree species impacts plant uptake of Si
On the origin of Planosols–the process of ferrolysis revisited
Impact of tree species on the distribution of alkaliextractable Si in a Cambisol
The future soil capacity of Podzols to stabilize soil organic carbon through formation of imogolite
Space-time dynamics of soil respiration link to the C pool distribution at the hillslope scale
ABSTRACT A crucial issue in soil C dynamics modelling is to develop models suitable for regional ... more ABSTRACT A crucial issue in soil C dynamics modelling is to develop models suitable for regional scale, but based on local and short-time scale observations. Recent research has illustrated the strong linkage between SOC dynamics and landscape processes. There is increasing evidence that lateral fluxes of SOC, sediment and water will further enhance the variability of SOC dynamics, especially on agricultural land. Hence, in this study, we aim to improve our understanding of soil C dynamics by quantifying the soil respiration response of carbon pools at different positions along a slope catena, characterized by different soil moisture and temperature conditions and by different SOC stock and C pool distributions. The study was performed on a hillslope in the belgian loamy belt. Time series of soil moisture, temperature and surface CO2 fluxes were monitored on a regular basis (at least once a week, during spring and autumn 2011) along the hillsope, at the soil surface. At the same positions, soil cores (1 to 1.5 m depth) were collected and analyzed for SOC, C distribution (using a chemical fractionation), mineral oxides (oxalate extractions), pH, and texture. Our results show that substantial lateral transport of soil materials takes place along this hillslope, with a continuous burying of surface C and minerals at the bottom of the slope. This results in the development of a colluvial soil with an increasing SOC stock. This colluvial C stock mainly consists of labile C (66%), and this labile C stock in the colluvium is 3.5 higher than the labile C stock at the other slope positions. This stock is thus poorly stabilized and has a higher potential for mineralization. The other part of this C stock is stabilized by organo-mineral associations (19%) or is recalcitrant C (15%). Compared to the other slope positions, this colluvial stable C stock is significant, as it is 1.5 to 2 times higher. The spatial gradient of the measured soil respiration is consistent with the previous C pool distribution observations along the hillslope, since there is a significant higher respiration at the bottom of the slope (colluvial area) than at the other slope positions. The measured temporal dynamics of the soil respiration is explained by moisture and temperature variations. This measured space-time dynamics, completed with further additional field measurement campaigns, will be the basis for calibrating and validating hillslope scale soil C turn-over models.
The hillslope as elementary unit to access the soil C balance by studying the impact of soil erosion on organic carbon sequestration and soil respiration
The key role of Fe oxide coatings on pedogenic clay minerals in the formation of organo-mineral associations in Podzol
The interdependent relationship between C dynamics and soil-forming processes in a podzolic chronosequence under a temperate rainforest
ABSTRACT The interdependent relationship between C dynamics and soil-forming processes in a podzo... more ABSTRACT The interdependent relationship between C dynamics and soil-forming processes in a podzolic chronosequence under a temperate rainforest
Evolution of C dynamics, microorganism populations and soil-forming processes in a podzolic chronosequence
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Papers by Jean-Thomas Cornelis