The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Stefan C. Dekker - One of the best experts on this subject based on the ideXlab platform.
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Modelling C and N Mineralisation in soil food webs during secondary succession on ex-arable land
Soil Biology & Biochemistry, 2011Co-Authors: Remko Holtkamp, Peter C. De Ruiter, Wim H Van Der Putten, Paul Kardol, Stefan C. DekkerAbstract:The rate of secondary succession after land abandonment depends on the interplay between aboveground and belowground processes. Changes in vegetation composition lead to altered amounts and composition of soil organic matter (SOM) with consequences for the abundance and functioning of the soil food web. In turn, soil food web structure determines the Mineralisation rate of nutrients that can be taken up by plants. This study analyses changes in the C and N Mineralisation rates along with soil food web structure during secondary succession after land abandonment. In a previous study, changes in soil food web structure and SOM quantity and quality were measured at different stages of secondary succession on abandoned arable fields (abandoned for 2, 9 and 22 years and a heathland, which is the assumed target of the secondary succession). Based on these measurements we expected the C and N Mineralisation rates to increase during secondary succession. The key hypothesis is that with a description of the soil food webs in terms of quantified biomasses, natural death rates, energy conversion efficiencies and diets enables a calculation of C and N Mineralisation rates in soils. The basic assumptions connected to this hypothesis are that on a time-scale of years the population sizes are in steady state. We also calculated Mineralisation rates per trophic level and energy channel. Based on the same measurements we expected that the contributions by the lower trophic level groups will increase as well as the Mineralisation rates by bacterial and fungal energy channels. Measured C and N Mineralisation indeed increased during the 22-year period of abandonment. The calculated C and N Mineralisation rates showed the same trend after land abandonment as the measured values. Calculated contributions to Mineralisation of organisms at trophic level 1 increase during secondary succession following land abandonment. The fungal decomposition channel contributed more to N Mineralisation than the bacterial decomposition channel, whereas both channels contributed equally to C Mineralisation rates. Direct contributions by higher trophic levels to Mineralisation decreased during secondary succession. However, higher trophic levels were direct important for N Mineralisation and indirect for both C and N Mineralisation due to their effect on biomass turnover rates of groups at lower trophic levels. The increasing total N Mineralisation rate of the soil food web, however, does not benefit plants, as during succession plant species that mainly grow under high nutrient availability are replaced by species that can grow in nutrient poor condition.
Rose Amal - One of the best experts on this subject based on the ideXlab platform.
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inter relationship between pt oxidation states on tio2 and the photocatalytic Mineralisation of organic matters
Journal of Catalysis, 2007Co-Authors: Wey Yang Teoh, Lutz Mädler, Rose AmalAbstract:Abstract The inter-relationship between Pt oxidation state dynamics and the TiO2 photocatalysis of three groups of organic compounds (carboxylic acid, alcohol and phenolics) was investigated. Repetitive photocatalytic Mineralisation of formic acid over the as-prepared Pt(II)/TiO2 produced free formate radicals which partially reduced Pt(II) to Pt(0, II)/TiO2. Further repetitive dark Mineralisation of formic acid over this pretreated catalyst was as effective as the as-prepared sample under UV-A illumination. As for the photocatalytic Mineralisation of methanol, the usually reported current doubling effect which would result in the reduction of Pt was not observed under the studied air-equilibrated condition and low organic concentration. However, the photocatalytic Mineralisation of methanol was enhanced over formic acid-pretreated catalyst compared to the as-prepared and phenol-pretreated samples, highlighting the beneficial and detrimental effects of Pt(0) and Pt(IV), respectively. The enhancement was partially attributed to the favourable intimate dark catalytic interaction between Pt(0) and methanol. The photocatalytic Mineralisation rates of phenol over as-prepared and formic acid-pretreated catalysts were found to be limited by the benzoquinone/hydroquinone short-circuit equilibrium. The photocatalytic Mineralisation of trihydroxybenzene, the immediate product after the short-circuit equilibrium, over as-prepared Pt/TiO2 was faster relative to phenol and more so over the formic acid-pretreated sample. This corroborates the rate-limiting equilibrium while also demonstrates the beneficial effect of Pt(0). The enhancement effects on these phenolic compounds were in qualitative agreement with the observed dark catalytic Mineralisation.
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Photocatalytic Mineralisation of organic compounds: a comparison of flame-made TiO_2 catalysts
Topics in Catalysis, 2007Co-Authors: Wey Yang Teoh, Frans Denny, Rose Amal, Donia Friedmann, Lutz Mädler, Sotiris E. PratsinisAbstract:A comparative photocatalytic analysis was carried out on TiO_2 made in a Flame Spray Pyrolysis (FSP) process and flame-made Degussa P25. Both have similar crystallinity, phase composition, phase segregation and a non-porous surface. Hence comparison was made based on their difference in specific surface area, organic adsorption and the amount of OH• generated upon illumination. The photocatalytic activity tests were carried out using the following series of organic compounds: sucrose, glucose, fructose, maleic acid, glyoxylic acid, oxalic acid, isobutyric acid, phenol and methanol. FSP-made TiO_2 outperformed P25 for saccharides Mineralisation, while for phenol and methanol Mineralisation P25 was better than FSP-made TiO_2. Similar Mineralisation rates were observed for both FSP-made and P25 TiO_2 for the Mineralisation of carboxylic acids. This shows that the relative performance of the photocatalysts depends on the type of organic compounds to be degraded. The high surface area and possibly a more efficient interfacial charge transfer of FSP-made TiO_2 provided an efficient pathway for saccharides Mineralisation. As for phenol and methanol, the Mineralisation rates were higher when using P25 due to the greater amount of OH• radicals generated by this photocatalyst. The fast Mineralisation rates of carboxylic acids made degradation of these organic compounds to be less affected by the TiO_2 photocatalyst properties and conditions tested in this work.
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insight towards the role of platinum in the photocatalytic Mineralisation of organic compounds
Journal of Molecular Catalysis A-chemical, 2007Co-Authors: Frans Denny, Jason Scott, Ken Chiang, Wey Yang Teoh, Rose AmalAbstract:Abstract The Mineralisation of functionalised (hydroxyl and carboxylic) organic compounds by platinum deposits on titanium dioxide (Pt/TiO2) was investigated to study the catalytic and photocatalytic roles of platinum and the effect of organic molecular structure on these properties. Under dark conditions Pt/TiO2 catalysed the complete Mineralisation of formic acid and partial Mineralisation of oxalic acid and 1,2,3-trihydroxybenzene (1,2,3-THB). Under irradiated conditions, platinum deposits improved the Mineralisation rate of each organic considered. Increasing carbon chain length of aliphatic compounds decreased Mineralisation rates by both bare TiO2 and Pt/TiO2, attributed to steric hindrance effects for alcohols and the formation of rate limiting intermediates for carboxylic acids. Increasing the number of hydroxyl groups in aliphatic compounds increased Mineralisation rates only by Pt/TiO2. This effect was not evident for hydroxylated aromatics. The findings suggest the degree of catalysis invoked by platinum deposits during photocatalysis is governed by the structural and functional characteristics of the target organic.
Peter C. De Ruiter - One of the best experts on this subject based on the ideXlab platform.
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Modelling C and N Mineralisation in soil food webs during secondary succession on ex-arable land
Soil Biology & Biochemistry, 2011Co-Authors: Remko Holtkamp, Peter C. De Ruiter, Wim H Van Der Putten, Paul Kardol, Stefan C. DekkerAbstract:The rate of secondary succession after land abandonment depends on the interplay between aboveground and belowground processes. Changes in vegetation composition lead to altered amounts and composition of soil organic matter (SOM) with consequences for the abundance and functioning of the soil food web. In turn, soil food web structure determines the Mineralisation rate of nutrients that can be taken up by plants. This study analyses changes in the C and N Mineralisation rates along with soil food web structure during secondary succession after land abandonment. In a previous study, changes in soil food web structure and SOM quantity and quality were measured at different stages of secondary succession on abandoned arable fields (abandoned for 2, 9 and 22 years and a heathland, which is the assumed target of the secondary succession). Based on these measurements we expected the C and N Mineralisation rates to increase during secondary succession. The key hypothesis is that with a description of the soil food webs in terms of quantified biomasses, natural death rates, energy conversion efficiencies and diets enables a calculation of C and N Mineralisation rates in soils. The basic assumptions connected to this hypothesis are that on a time-scale of years the population sizes are in steady state. We also calculated Mineralisation rates per trophic level and energy channel. Based on the same measurements we expected that the contributions by the lower trophic level groups will increase as well as the Mineralisation rates by bacterial and fungal energy channels. Measured C and N Mineralisation indeed increased during the 22-year period of abandonment. The calculated C and N Mineralisation rates showed the same trend after land abandonment as the measured values. Calculated contributions to Mineralisation of organisms at trophic level 1 increase during secondary succession following land abandonment. The fungal decomposition channel contributed more to N Mineralisation than the bacterial decomposition channel, whereas both channels contributed equally to C Mineralisation rates. Direct contributions by higher trophic levels to Mineralisation decreased during secondary succession. However, higher trophic levels were direct important for N Mineralisation and indirect for both C and N Mineralisation due to their effect on biomass turnover rates of groups at lower trophic levels. The increasing total N Mineralisation rate of the soil food web, however, does not benefit plants, as during succession plant species that mainly grow under high nutrient availability are replaced by species that can grow in nutrient poor condition.
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community food web decomposition and nitrogen Mineralisation in a stratified scots pine forest soil
Oikos, 2001Co-Authors: Matty P Berg, Peter C. De Ruiter, Wim Didden, Martien Janssen, Ton Schouten, H A VerhoefAbstract:A soil community food web model was used to improve the understanding of what factors govern the Mineralisation of nutrients and carbon and the decay of dead organic matter. The model derives the rates of C and N Mineralisation by organisms by splitting their uptake rate of food resources into a rate at which faeces or prey remains are added to detritus, a rate at which elements are incorporated into biomass, and a rate at which elements are released by organisms as inorganic compounds. The functioning of soil organisms in the Mineralisation of C and N was modelled in the soil horizon of a Scots pine forest. The organic horizon was divided into three distinct layers, representing successive stages of decay, i.e. litter, fragmented litter, and humus. Each of the layers had a different, quantitative, biota composition. For each layer the annual C and N Mineralisation rates were simulated and compared to observed C and N Mineralisation rates from organic matter in stratified litterbags. Simulated C and N Mineralisation was relatively close to measured losses of C and N, but the fit was not perfect. Discrepancies between the observed and predicted Mineralisation rates are discussed in terms of variation in model parameter values of those organisms that showed the highest contribution to Mineralisation rates. The measured, and by the model predicted, significant decrease in Mineralisation rates down the profile was not explained by the biomass of the primary decomposers and only partly by the total food web biomass. Modelling results indicated that indirect effects of soil fauna, due to trophic interactions with their resources, are an important explanatory factor. In addition, the analyses suggest that community food web structure is an important factor in the regulation of nutrient Mineralisation. The model provided the means to evaluate the contribution of functionally defined groups of organisms, structured in a detrital food web, to losses of C and N from successive decay stages.
Imkyun Lee - One of the best experts on this subject based on the ideXlab platform.
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soil nitrogen mineralization in adjacent stands of larch pine and oak in central korea
Annals of Forest Science, 1997Co-Authors: Yowhan Son, Imkyun LeeAbstract:Afin d'examiner les effets de trois especes forestieres sur la Mineralisation de l'azote du sol, nous avons mesure la vitesse de Mineralisation de l'azote et de la nitrification dans les sols par la technique des sacs in situ dans des peuplements de meleze du Japon (Larix leptolepis Gordon), de pitchpin (Pinus rigida Mill) et de chene (Quercus serrata Thunb), âges de 37 ans et situes sur des sols similaires de Coree centrale. Litiere et sol mineral (0-15 cm) ont ete incubes pendant des periodes de 45 jours du 1 er septembre 1994 au 31 aout 1995. Les moyennes journalieres de Mineralisation de l'azote etaient significativement differentes entre les trois especes forestieres. La Mineralisation azotee annuelle a ete estimee a 44 kg/ha/an pour P rigida, a 92 pour L leptolepis et a 112 pour Q serrata. Le pourcentage de nitrification varie de 45 % pour P rigida a 90 % pour L leptolepis. La quantite d'azote apportee par la chute des litieres semble influencer la Mineralisation de l'azote au sol. Cette etude montre que, dans des conditions stationnelles equivalentes, la Mineralisation de l'azote peut varier, dans des rapports superieurs a un, sous l'effet de l'espece.
Remko Holtkamp - One of the best experts on this subject based on the ideXlab platform.
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Modelling C and N Mineralisation in soil food webs during secondary succession on ex-arable land
Soil Biology & Biochemistry, 2011Co-Authors: Remko Holtkamp, Peter C. De Ruiter, Wim H Van Der Putten, Paul Kardol, Stefan C. DekkerAbstract:The rate of secondary succession after land abandonment depends on the interplay between aboveground and belowground processes. Changes in vegetation composition lead to altered amounts and composition of soil organic matter (SOM) with consequences for the abundance and functioning of the soil food web. In turn, soil food web structure determines the Mineralisation rate of nutrients that can be taken up by plants. This study analyses changes in the C and N Mineralisation rates along with soil food web structure during secondary succession after land abandonment. In a previous study, changes in soil food web structure and SOM quantity and quality were measured at different stages of secondary succession on abandoned arable fields (abandoned for 2, 9 and 22 years and a heathland, which is the assumed target of the secondary succession). Based on these measurements we expected the C and N Mineralisation rates to increase during secondary succession. The key hypothesis is that with a description of the soil food webs in terms of quantified biomasses, natural death rates, energy conversion efficiencies and diets enables a calculation of C and N Mineralisation rates in soils. The basic assumptions connected to this hypothesis are that on a time-scale of years the population sizes are in steady state. We also calculated Mineralisation rates per trophic level and energy channel. Based on the same measurements we expected that the contributions by the lower trophic level groups will increase as well as the Mineralisation rates by bacterial and fungal energy channels. Measured C and N Mineralisation indeed increased during the 22-year period of abandonment. The calculated C and N Mineralisation rates showed the same trend after land abandonment as the measured values. Calculated contributions to Mineralisation of organisms at trophic level 1 increase during secondary succession following land abandonment. The fungal decomposition channel contributed more to N Mineralisation than the bacterial decomposition channel, whereas both channels contributed equally to C Mineralisation rates. Direct contributions by higher trophic levels to Mineralisation decreased during secondary succession. However, higher trophic levels were direct important for N Mineralisation and indirect for both C and N Mineralisation due to their effect on biomass turnover rates of groups at lower trophic levels. The increasing total N Mineralisation rate of the soil food web, however, does not benefit plants, as during succession plant species that mainly grow under high nutrient availability are replaced by species that can grow in nutrient poor condition.