Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Proteins unbound – how ectomycorrhizal fungi can tap a vast reservoir of mineral-associated organic nitrogen
    Keiluweit, Marco ; Kuyper, Thomas W. - \ 2020
    New Phytologist 228 (2020)2. - ISSN 0028-646X
    ectomycorrhizal fungi - enzyme-mediated mechanisms - forest soil - iron (Fe) oxyhydroxides - mineral-associated organic nitrogen - nitrogen (N) acquisition - soil organic matter
    Snow cover manipulation effects on microbial community structure and soil chemistry in a mountain bog
    Robroek, B.J.M. ; Heijboer, A. ; Jassey, V.E.J. ; Hefting, M.M. ; Rouwenhorst, T.G. ; Buttler, A. ; Bragazza, L. - \ 2013
    Plant and Soil 369 (2013). - ISSN 0032-079X - p. 151 - 164.
    freeze-thaw cycles - rv-coefficient - climate-change - tundra soils - forest soil - nitrogen - dynamics - biomass - variability - trends
    Background and Aims Alterations in snow cover driven by climate change may impact ecosystem functioning, including biogeochemistry and soil (microbial) processes. We elucidated the effects of snow cover manipulation (SCM) on above-and belowground processes in a temperate peatland. Methods In a Swiss mountain-peatland we manipulated snow cover (addition, removal and control), and assessed the effects on Andromeda polifolia root enzyme activity, soil microbial community structure, and leaf tissue and soil biogeochemistry. Results Reduced snow cover produced warmer soils in our experiment while increased snow cover kept soil temperatures close-to-freezing. SCM had a major influence on the microbial community, and prolonged ‘close-to-freezing’ temperatures caused a shift in microbial communities toward fungal dominance. Soil temperature largely explained soil microbial structure, while other descriptors such as root enzyme activity and pore-water chemistry interacted less with the soil microbial communities. Conclusions We envisage that SCM-driven changes in the microbial community composition could lead to substantial changes in trophic fluxes and associated ecosystem processes. Hence, we need to improve our understanding on the impact of frost and freeze-thaw cycles on the microbial food web and its implications for peatland ecosystem processes in a changing climate; in particular for the fate of the sequestered carbon.
    Soil invertebrate fauna affect N2O emissions from soil
    Kuiper, I. ; Deyn, G.B. de; Thakur, M.P. ; Groenigen, J.W. van - \ 2013
    Global Change Biology 19 (2013)9. - ISSN 1354-1013 - p. 2814 - 2825.
    greenhouse-gas emissions - nitrous-oxide - nutrient mineralization - n mineralization - forest soil - carbon - ecosystems - denitrification - decomposition - enchytraeids
    Nitrous oxide (N2O) emissions from soils contribute significantly to global warming. Mitigation of N2O emissions is severely hampered by a lack of understanding of its main controls. Fluxes can only partly be predicted from soil abiotic factors and microbial analyses – a possible role for soil fauna has until now largely been overlooked. We studied the effect of six groups of soil invertebrate fauna and tested the hypothesis that all of them increase N2O emissions, although to different extents. We conducted three microcosm experiments with sandy soil and hay residue. Faunal groups included in our experiments were as follows: fungal-feeding nematodes, mites, springtails, potworms, earthworms and isopods. In experiment I, involving all six faunal groups, N2O emissions declined with earthworms and potworms from 78.4 (control) to 37.0 (earthworms) or 53.5 (potworms) mg N2O-N m-2. In experiment II, with a higher soil-to-hay ratio and mites, springtails and potworms as faunal treatments, N2O emissions increased with potworms from 51.9 (control) to 123.5 mg N2O-N m-2. Experiment III studied the effect of potworm density; we found that higher densities of potworms accelerated the peak of the N2O emissions by 5 days (P <0.001), but the cumulative N2O emissions remained unaffected. We propose that increased soil aeration by the soil fauna reduced N2O emissions in experiment I, whereas in experiment II N2O emissions were driven by increased nitrogen and carbon availability. In experiment III, higher densities of potworms accelerated nitrogen and carbon availability and N2O emissions, but did not increase them. Overall, our data show that soil fauna can suppress, increase, delay or accelerate N2O emissions from soil and should therefore be an integral part of future N2O studies.
    A simple and effective method to keep earthworms confined to open-top mesocosms
    Lubbers, I.M. ; Groenigen, J.W. van - \ 2013
    Applied Soil Ecology 64 (2013). - ISSN 0929-1393 - p. 190 - 193.
    nitrous-oxide - forest soil - organic-carbon - n2o emission - mineralization - decomposition - mobilization - grassland - savigny - residue
    Earthworms can have a profound effect on a myriad of soil physical, chemical and microbial parameters. To better understand their role in the soil, they are often studied under controlled conditions. However, a persistent problem in such controlled experiments is the ability of earthworms to escape from experimental units with open tops (e.g. for plant growth). Here, we tested whether adhesive hook tape applied to the inside of mesocosms is effective in confining them to their experimental units. A mesocosm study was set up with hook tape treatments (control, one layer, two layers), mesocosm material (polyvinylchloride – PVC, polypropylene – PP) and earthworm species (Lumbricus rubellus (Hoffmeister), Aporrectodea caliginosa (Savigny), Lumbricus terrestris (L.) + Aporrectodea longa (Ude)) as different factors to study the escape of earthworms during 24 h. In the treatments without hook tape, individuals of L. rubellus and A. caliginosa escaped, with highest escape rates (80%) for L. rubellus from the PP mesocosms, and lowest escape rates (20%) for A. caliginosa from the PVC mesocosms. When hook tape was applied, in either one or two layers, no individuals of those species escaped. The two anecic earthworm species, L. terrestris and A. longa did not escape from any mesocosms, irrespective of the presence of hook tape. As not a single earthworm escaped from the hook tape treatments, we conclude that applying hook tape is a simple, inexpensive and effective method to keep earthworms confined to experimental units.
    Soil organic matter chemistry changes upon secondary succession in Imperata Grasslands , Indonesia: A pyrolysis - GC/MS study
    Yassir, I. ; Buurman, P. - \ 2012
    Geoderma 173-174 (2012). - ISSN 0016-7061 - p. 94 - 103.
    chromatography-mass-spectrometry - chemical-composition - carbon pool - forest soil - humic acids - land-use - fractions - lignin - nmr - stabilization
    The chemical composition of soil organic matter (SOM) following secondary succession in Imperata grassland was investigated by Pyrolysis-Gas Chromatography/Mass Spectrometry (GC/MS). We studied 46 samples from different stages of succession using plots that last burned 3 and 9 years previously, secondary forest (= 15 years), primary forest and Acacia mangium plantation (9 years). During regeneration of Imperata grasslands the chemical composition of SOM changes considerably. Differences between litters and SOM were larger than within SOM, which is mainly due to a rapid degradation of lignin in the soil. Both litter and SOM under Imperata contain larger amounts of carbohydrates and fewer lignin moieties, aliphatics and N-compounds than those under secondary and primary forest. Nevertheless, SOM degradation under grassland is less efficient because of scarcity of N-compounds. SOM decomposition is most advanced under forest, as indicated by lower amounts of plant derived compounds and higher contribution of microbial matter. Decomposition efficiency appears to be related to SOM chemistry, but more to abundance of N-compounds than to that of potentially recalcitrant compounds. C stocks were linked to decomposition efficiency and litter production.
    Effects of fire ash on soil water retention
    Stoof, C.R. ; Wesseling, J.G. ; Ritsema, C.J. - \ 2010
    Geoderma 159 (2010)3-4. - ISSN 0016-7061 - p. 276 - 285.
    physical-properties - fly-ash - forest soil - hydrological properties - mediterranean soils - moisture retention - organic-matter - wildfire - erosion - texture
    Despite the pronounced effect of fire on soil hydrological systems, information on the direct effect of fire on soil water retention characteristics is limited and contradictory. To increase understanding in this area, the effect of fire on soil water retention was evaluated using laboratory burning and heating experiments. In addition, ash-infiltration and ash-incorporation experiments were performed to evaluate the effect of ash on soil water retention. While heating soil to 200 °C and below did not change soil properties, burning and heating to 300 °C and above increased bulk density, clay and silt content, and decreased organic matter and sand content. Burning and heating above 200 °C decreased the amount of water stored at the nine tensions considered, although the effect on soil water retention did not always increase with increasing temperature. Changes were largest for low tensions, i.e. between saturation and field capacity (10 kPa). Heating to 200 °C decreased the amount of plant available water, but despite reducing the amount of water stored at evaluated tensions, burning and heating to 300 °C and above increased the amount of plant available water. This may be caused by more complete combustion of organic matter at the higher temperatures and the production of ash. Direct incorporation of ash into soils did not alter soil texture but increased water retention from saturation to 310 kPa tension. Ash infiltration experiments interestingly had a similar effect, despite the fact that very little ash washed into the samples. Results from these experiments contribute to understanding post-fire changes in hydrological and erosion processes.
    Differences in chemical composition of soil organic matter in natural ecosystems from different climatic regions: a pyrolysis-GC/MS study
    Vancampenhout, K. ; Wouters, K. ; Vos, B. de; Buurman, P. ; Swennen, R. ; Deckers, J. - \ 2009
    Soil Biology and Biochemistry 41 (2009)3. - ISSN 0038-0717 - p. 568 - 579.
    rothamsted classical experiments - particle-size fractions - state c-13 nmr - humic substances - forest soil - black carbon - vertical-distribution - decomposition rates - mass-spectrometry - temperate soils
    Soil organic matter (SOM) is a key factor in ecosystem dynamics. A better understanding of the global relationship between environmental characteristics, ecosystems and SOM chemistry is vital in order to assess its specific influence on carbon cycles. This study compared the composition of extracted SOM in 18 topsoil samples taken under tundra, taiga, steppe, temperate forest and tropical forest using pyrolysis¿GC/MS. Results indicate that SOM from cold climates (tundra, taiga) still resembles the composition of litter, evidenced by high quantities of levosugars and long alkanes relative to N-compounds and a clear odd-over-even dominance of the longer alkanes. Under temperate conditions, increased microbial degradation generally results in a more altered SOM chemistry. SOM formed under temperate coniferous forests shows an accumulation of aromatic and aliphatic moieties, probably induced by substrate limitations. Tropical SOM was characterized by an SOM composition rich in N-compounds and low in lignins, without any accumulation of recalcitrant fractions (i.e. aliphatic and aromatic compounds). Lignin composition moreover varies according to vegetation type. Results were validated against 13 new samples. The humic signature of topsoil organic matter formed under different biomes indicates a dominating effect of (i) SOM input composition related to vegetation, and (ii) SOM breakdown reflecting both climate and input quality. No evidence was found for a chemically stabilized SOM fraction under favorable decomposition conditions (temperate or warm climate with broadleaved vegetation)
    NaOH-extractable organic matter of andic soils from Galicia (NW Spain) under different land use regimes: a pyrolysis GC/MS study
    Verde, J.R. ; Buurman, P. ; Martinez-Cortizas, A. ; Macias, F. ; Camps Arbestain, M. - \ 2008
    European Journal of Soil Science 59 (2008)6. - ISSN 1351-0754 - p. 1096 - 1110.
    polycyclic aromatic-hydrocarbons - ionization mass-spectrometry - volcanic ash soils - gas chromatography - humic substances - forest soil - acids - carbon - decomposition - preservation
    The objective of this study was to determine to what extent the attenuation or loss of andic soil properties caused by land use change ¿ from forest (FOR, average C content 118.2 ± 23.7 g kg¿1) to agricultural land (AGR, average C content 55.7 ± 16.7 g kg¿1) use ¿ is reflected in soil organic matter (SOM) at the molecular level. For this, NaOH-extractable SOM of A horizons from 17 soils developed on amphibolitic parent material in NW Spain was studied by pyrolysis gas chromatography spectrometry (Py-GC/MS). We also included two buried andic A horizons (PAL, 2200 cal yr BP in age) on the same parent material, as a reference for the molecular composition of SOM from soils without recent litter additions. Organic matter of PAL soils had a composition largely different from that of superficial soils (FOR and AGR), with an important relative contribution of microbial polysaccharides and N-compounds, and an absence of compounds that characterize fresh plant litter (e.g. lignins). In the superficial soils, the relative contribution of lignin-derived compounds was greater in AGR than in FOR soils. Differences were also observed in the relative contribution of aliphatic compounds, FOR soils being enriched in this type of components compared with AGR soils. The results indicated that land use change from FOR to AGR, which was accompanied by a decrease in total SOM, resulted in an enrichment in primary SOM. The smaller relative abundance of primary SOM derivatives in andic FOR soils indicates that these compounds were quickly degraded in Andisols
    Comparison of Michigan and Dutch Podzolized
    Buurman, P. ; Jongmans, A.G. ; Nierop, K.G.J. - \ 2008
    Soil Science Society of America Journal 72 (2008)5. - ISSN 0361-5995 - p. 1344 - 1356.
    lake-michigan - vegetation succession - incipient podzols - forest soil - c-13 nmr - gc-ms - horizons - fractions - dunes - sand
    Soil organic matter in a chronosequence of Michigan soils (Spodic Udipsamments and precursors) was studied in thin section and by pyrolysis-gas chromatography/mass spectrometry (GC/MS). The Michigan soils were compared with a well-drained Dutch Typic Haplorthod that was studied with the same methods. Both techniques indicate that most B-horizon organic matter in the Michigan sequence is root- and char-derived and not due to illuviation. Microbial matter contributes significantly to B-horizon chemistry. Although charcoal is common in A horizons, it hardly contributes to soil organic matter (SOM) chemistry in this horizon, while it constitutes a significant part of B-horizon C. This suggests that silt-size particulate charcoal is transported downward. Nitrogen-containing pyrolysis fragments are abundant, which, together with significant amounts of aromatic components, points to contribution of proteins. The Michigan soils are far less rich in alkyl C than the Dutch counterpart. This suggests a much lower residual accumulation of recalcitrant compounds in the former, probably due to a larger contribution of root litter and a more efficient decomposition. Faster decomposition (shorter mean residence time) in the Michigan soils is also suggested by the low accumulation of SOM in the B horizon. Thus we can conclude that in the Michigan soils, dissolved organic matter contributes significantly to transport of Al and Fe, but essentially without illuviation of organic matter in the B. In the Dutch Spodosol, on the other hand, both transport of dissolved organic C to the B horizon and accumulation of SOM through decomposition of roots play important roles. Pyrolysis-GC/MS is a powerful tool in deciphering organic-matter-related aspects of soil genesis. The formation of many soils is organic matter driven, and this aspect is still poorly understood.
    A detailed pyrolysis-GC/MS analysis of a black carbon-rich acidic colluvial soil (Atlantic ranker) from NW Spain
    Kaal, J. ; Martinez-Cortizas, A. ; Nierop, K.G.J. ; Buurman, P. - \ 2008
    Applied Geochemistry 23 (2008)8. - ISSN 0883-2927 - p. 2395 - 2405.
    c-13 nmr-spectroscopy - volcanic ash soils - solid-state c-13 - organic-matter - forest soil - chemical-composition - mass-spectrometry - humic acids - gc-ms - biomass
    Despite the potentially large contribution of black carbon (BC) to the recalcitrant soil organic matter pool, the molecular-level composition of aged BC has hardly been investigated. Pyrolysis-GC/MS, which provides structural information on complex mixtures of organic matter, was applied to the NaOH-extractable organic matter of an acidic colluvial soil (Atlantic ranker) sampled with high resolution (5 cm) that harbours a fire record of at least 8.5 ka. Additionally, 5 charcoal samples from selected soil layers were characterised using pyrolysis-GC/MS for comparison. Pyrolysis-GC/MS allowed distinguishing between BC and non-charred organic matter. It is argued that a large proportion of the polycyclic aromatic hydrocarbons (PAHs), benzenes and benzonitrile in the pyrolysates of the extractable organic matter, together accounting for 21¿54% of total identified peak area, derived from BC. In charcoal samples, these compounds accounted for 60¿98% of the pyrolysis products. The large quantity of BC in almost all samples suggested a key role of fire in Holocene soil evolution. The high C content of the soil (up to 136 g C kg¿1 soil) may be attributed to the presence of recalcitrant organic C as BC, in addition to the sorptive preservation processes traditionally held responsible for long-term C storage in acid soils. Interactions between reactive Al hydroxides and BC could explain the longevity of BC in the soil. This work is the first thorough pyrolysis-GC/MS based study on ancient fire-affected organic matter.
    Rock-eating mycorrhizas: their role in plant nutrition and biogeochemical cycles
    Schöll, L. van; Kuyper, T.W. ; Smits, M.M. ; Landeweert, R. ; Hoffland, E. ; Breemen, N. van - \ 2008
    Plant and Soil 303 (2008)1-2. - ISSN 0032-079X - p. 35 - 47.
    fungus paxillus-involutus - norway-spruce seedlings - organic anion exudation - ectomycorrhizal fungi - pinus-sylvestris - forest soil - boreal forest - extramatrical mycelium - aluminum tolerance - carbon allocation
    A decade ago, tunnels inside mineral grains were found that were likely formed by hyphae of ectomycorrhizal (EcM) fungi. This observation implied that EcM fungi can dissolve mineral grains. The observation raised several questions on the ecology of these ¿rock-eating¿ fungi. This review addresses the roles of these rock-eating EcM associations in plant nutrition, biogeochemical cycles and pedogenesis. Research approaches ranged from molecular to ecosystem level scales. Nutrient deficiencies change EcM seedling exudation patterns of organic anions and thus their potential to mobilise base cations from minerals. This response was fungal species-specific. Some EcM fungi accelerated mineral weathering. While mineral weathering could also increase the concentrations of phytotoxic aluminium in the soil solution, some EcM fungi increase Al tolerance through an enhanced exudation of oxalate. Through their contribution to Al transport, EcM hyphae could be agents in pedogenesis, especially podzolisation. A modelling study indicated that mineral tunnelling is less important than surface weathering by EcM fungi. With both processes taken together, the contribution of EcM fungi to weathering may be significant. In the field vertical niche differentiation of EcM fungi was shown for EcM root tips and extraradical mycelium. In the field EcM fungi and tunnel densities were correlated. Our results support a role of rock-eating EcM fungi in plant nutrition and biogeochemical cycles. EcM fungal species-specific differences indicate the need for further research with regard to this variation in functional traits.
    Occurrence and distribution of tetraether membrane lipids in soils: implications for the use of the TEX86 proxy and the BIT index
    Weijers, J.W.H. ; Schouten, S. ; Spaargaren, O.C. ; Sinnige Damsté, J.S. - \ 2006
    Organic Geochemistry 37 (2006)12. - ISSN 0146-6380 - p. 1680 - 1693.
    peat bog - kingdom crenarchaeota - phylogenetic analysis - lake-sediments - forest soil - archaea - abundance - diversity - identification - temperatures
    A diverse collection of globally distributed soil samples was analyzed for its glycerol dialkyl glycerol tetraether (GDGT) membrane lipid content. Branched GDGTs, derived from anaerobic soil bacteria, were the most dominant and were found in all soils. Isoprenoid GDGTs, membrane lipids of Archaea, were also present, although in considerably lower concentration. Crenarchaeol, a specific isoprenoid membrane lipid of the non-thermophilic Crenarchaeota, was also regularly detected and its abundance might be related to soil pH. The detection of crenarchaeol in nearly all of the samples is the first report of this type of GDGT membrane lipid in soils and is in agreement with molecular ecological studies, confirming the widespread occurrence of non-thermophilic Crenarchaeota in the terrestrial realm. The fluvial transport of crenarchaeol and other isoprenoid GDGTs to marine and lacustrine environments could possibly bias the BIT index, a ratio between branched GDGTs and crenarchaeol used to determine relative terrestrial organic matter (TOM) input. However, as crenarchaeol in soils is only present in low concentration compared to branched GDGTs, no large effect is expected for the BIT index. The fluvial input of terrestrially derived isoprenoid GDGTs could also bias the TEX86, a proxy used to determine palaeo surface temperatures in marine and lacustrine settings and based on the ratio of cyclopentane-containing isoprenoid GDGTs in marine and lacustrine Crenarchaeota. Indeed, it is shown that a substantial bias in TEX86-reconstructed sea and lake surface temperatures can occur if TOM input is high, e.g. near large river outflows. (c) 2006 Elsevier Ltd. All rights reserved.
    The straight-chain lipid biomarker composition of plant species responsible for the dominant biomass production along two altitudinal transects in the Ecuadorian Andes
    Jansen, B. ; Nierop, K.G.J. ; Hageman, J.A. ; Cleef, A.M. ; Verstraten, J.M. - \ 2006
    Organic Geochemistry 37 (2006)11. - ISSN 0146-6380 - p. 1514 - 1536.
    extractable lipids - forest soil - lake - stratigraphy - alkanes - carbon
    For a detailed reconstruction of historic upper forest line (UFL) positions, new proxies in addition to traditional pollen and vegetation analyses are needed. If the straight-chain lipid composition in plant leaves and roots is specific enough to allow distinction, their records in soils and peat bogs might be used for this purpose. We tested for such distinctiveness by analyzing the n-alkane, n-alcohol, n-aldehyde and wax ester composition in lipid extracts from the leaves and roots of the 19 plant species responsible for the dominant biomass input into soils and peat bogs along two altitudinal transects in the Ecuadorian Andes. We found the combined n-alkane and n-alcohol composition of the leaves of the studied plants to be unique enough in theory to allow for a distinction of the various plant species. The extractable straight-chain lipid concentrations in the roots were generally much lower than in the leaves of the same species, and were in many cases less specific. The n-fatty acids, n-aldehydes and wax ester compositions in leaves as well as roots appeared to be less suited as biomarkers, due to a lower specificity of the n-fatty acids and the absence of the n-aldehydes and wax ester from a significant number of plant species. Furthermore, using cluster analysis we found the combination of n-alkanes and n-alcohols from leaves to give the most meaningful clustering from the point of view of an UFL reconstruction, with all but one páramo grassland species and all but one peat bog species clustering separately from forest species. In addition, a large C31/C27 n-alkane ratio as well as a large C26/C30 n-alcohol ratio were found to be indicative of páramo vegetation (grasses). Both clustering and ratios can help reconstruct past UFL positions if discerning individual species from soil or peat records proves unfeasible. The preservation of the straight-chain lipid signal was tested in soil and peat samples from the study area predating 4910 ± 40 14C years B.P. and 2110 ± 40 14C years B.P., respectively, and found to be excellent.
    Ectomycorrhizal weathering of the soil minerals muscovite and hornblende
    Schöll, L. van; Smits, M.M. ; Hoffland, E. - \ 2006
    New Phytologist 171 (2006)4. - ISSN 0028-646X - p. 805 - 814.
    pinus-sylvestris seedlings - forest soil - in-vitro - mg2+ deficiency - organic-acids - picea-abies - fungi - roots - mobilization - dissolution
    Ectomycorrhizal fungi are hypothesized to enhance mineral weathering in forest soils. Several studies have shown an increased uptake of mineral-derived nutrients by trees when in symbiosis with ectomycorrhizal fungi. However, it is difficult to determine from these studies if the improved nutrient uptake is the result of increased weathering or better exploitation of the substrate by the ectomycorrhizal fungi. In a pot experiment, Pinus sylvestris (Scots pine) seedlings were grown with or without ectomycorrhizal fungi, and with or without the mineral muscovite as the only potassium (K) source or the mineral hornblende as the only magnesium (Mg) source. After 27 wk, all pools of non-mineral-bound K or Mg were determined. The ectomycorrhizal fungus Paxillus involutus increased weathering of muscovite but not hornblende. The other ectomycorrhizal fungi tested, Piloderma croceum and Suillus bovinus, did not increase weathering of either muscovite or hornblende compared with the nonmycorrhizal trees. The P. involutus-mediated mobilization of K from muscovite resulted in increased K content of root plus adhering hyphae, but not of shoots. In conclusion, ectomycorrhizal fungi may increase weathering of minerals in response to nutrient deficiencies, but this response is species specific
    Organic anion exudation by ectomycorrhizal fungi and Pinus sylvestris in response to nutrient deficiences
    Schöll, L. van; Hoffland, E. ; Breemen, N. van - \ 2006
    New Phytologist 170 (2006)1. - ISSN 0028-646X - p. 153 - 163.
    in-vitro - paxillus-involutus - soil solution - forest soil - mg2+ deficiency - oxalic-acid - oxalate - roots - mycorrhizal - seedlings
    Low molecular weight organic anions (LMWOA) can enhance weathering of mineral grains. We tested the hypothesis that ectomycorrhizal (EcM) fungi and tree seedlings increase their exudation of LMWOA when supply of magnesium, potassium and phosphorus is low to enhance the mobilization of Mg, K and P from mineral grains. ¿ Ectomycorrhizal fungi and Pinus sylvestris seedlings were cultured in symbiosis and in isolation on glass beads with nutrient solution or with sand as a rooting medium, with a complete nutrient supply or with Mg, K, P or N in low supply. Concentrations of all dicarboxylic LMWOA in the rooting medium were measured. ¿ Nonmycorrhizal seedlings released predominantly malonate. Colonization with Hebeloma longicaudum decreased the amount of organic anions exuded, whereas Paxillus involutus and Piloderma croceum increased the concentration of oxalate but not the total amount of LMWOA. Phosphorus deficiency increased the concentration of LMWOA by nonmycorrhizal and EcM seedlings. Magnesium deficiency increased the concentration of oxalate by nonmycorrhizal and EcM seedlings, but not the concentration of total LMWOA. Paxillus involutus grown in pure culture responded differently to low nutrient supply compared with symbiotic growth. ¿ Ectomycorrhizal fungi did not increase the total concentration of LMWOA compared with nonmycorrhizal seedlings but, depending on the fungal species, they affected the type of LMWOA found.
    The use of earthworms in ecological soil classification and assessment concepts
    Rombke, J. ; Jansch, S. ; Didden, W.A.M. - \ 2005
    Ecotoxicology and Environmental Safety 62 (2005)2 sp. iss.. - ISSN 0147-6513 - p. 249 - 265.
    ecosystem engineers - southern sweden - heavy-metals - forest soil - populations - lumbricidae - oligochaeta - organisms - profiles - invertebrates
    Without doubt, earthworms are the most important soil invertebrates in most soils worldwide, in terms of both biomass and activity. Several species are even considered to be ecosystem engineers. Earthworms are also known to influence soil structure, soil chemistry, and, in particular, processes like organic matter decomposition. In addition, standardized sampling methods are available and their taxonomy is well known (even the first PC-aided keys have been developed). For these reasons, earthworms were recognized as a part of ecological classification and assessment schemes early on. However, due to the relatively small number at many sites, they have to be part of a battery approach. By use of examples from The Netherlands (biological indicator of soil quality) and Germany (soil biological site classification), the practicability of the use of earthworms is demonstrated in determining the influence of different anthropogenic land use forms. In these cases, the structure of the earthworm community, as well as their abundance and biomass, were used as endpoints.
    The role of fungi in weathering
    Hoffland, E. ; Kuyper, T.W. ; Wallander, H. ; Plassard, C. ; Gorbushina, A.A. ; Haselwandter, K. ; Holmstrom, S. ; Landeweert, R. ; Lundstrom, U.S. ; Rosling, A. ; Sen, R. ; Smits, M.M. ; Hees, P.A.W. van; Breemen, N. van - \ 2004
    Frontiers in Ecology and the Environment 2 (2004)5. - ISSN 1540-9295 - p. 258 - 264.
    pinus-sylvestris seedlings - ectomycorrhizal fungi - organic-acids - forest soil - hydroxamate siderophores - lichen colonization - mg2+ deficiency - minerals - dissolution - rhizosphere
    No rock at the Earth's surface escapes weathering. This process is the primary source of all the essential elements for organisms, except nitrogen and carbon. Since the onset of terrestrial life, weathering has been accelerated under the influence of biota. The study of biological weathering started at the end of the 19th century. Although the role of bacteria (Eubacteria, Archaea) has attracted a lot of interest, until recently the role of fungi has largely been neglected. More recently, however, fungal weathering has become an increasingly important focus of biogeochemical research.
    Aluminium fractionation of European volcanic soils by selective dissolution techniques
    Garcia-Rodeja, E. ; Novoa, J.C. ; Pontevedra, X. ; Martinez-Cortizas, A. ; Buurman, P. - \ 2004
    Catena 56 (2004). - ISSN 0341-8162 - p. 155 - 183.
    organic-matter - acid soils - humus complexes - extractable aluminum - northeastern japan - variable charge - release rates - forest soil - solubility - horizons
    Several selective dissolution methods were used to differentiate Al forms in 12 soils formed from volcanic materials (64 andic, vitric and organic horizons) in Iceland, Azores (Portugal), Tenerife (Spain) and Italy. The soils differ in many properties because of differences in parent materials, climatic conditions, soil age and history of land use. 'Inorganic' fractions of Al were characterized using pyrophosphate (Al-p), acid oxalate (Al-o) and cold NaOH (Al-n) extractions. The difference in Al-o-Al-p, and Si extracted using acid oxalate, shows important differences among soils from different sources: allophane is richer in alumina in the Andosols from Azores and Tenerife than in those from Iceland and Italy. Cold NaOH generally extracted the same quantity of Al as acid oxalate, but in the soils from Tenerife Al-n exceeds Al-o, indicating the presence of gibbsite or poorly ordered halloysite. To characterize the Al bonded to the organic matter fraction, extractions with pyrophosphate, CuCl2 and LaCl3 were used. Except in one soil from Tenerife (N10), CuCl2 extracted less Al than pyrophosphate. In organic-rich mineral horizons, Al-LA, Al-Cu and Al-p increase with organic carbon content. Using unbuffered KCl and LaCl3, the amount of Al extracted increased with decreasing soil pH, but there was no similar relationship with unbuffered CuCl2. The general sequence of efficiency of the extractants was Al-p>Al-Cu>Al(La)greater than or equal toAl(K) in organic matter-rich horizons. Al-Cu constituted 30% of Al-p in all soils, indicating that CuCl2 extracts a very specific Al fraction. Al-p and Al-Cu are positively related to organic C. Al-p/Al-o, and Al-p-Al-Cu in andic horizons also increase with organic C. Phosphate retention and pH in NaF were related to Al-o and Al-n. The soils of Iceland have larger P retention than the others, and vitric horizons from Tenerife have higher pH in NaF and smaller Al pools than the other soils. For many horizons, there is a strong relationship between Al-Cu and components that determine soil CEC (organic matter and allophane), suggesting a possible action of CuCl2 on noncrystalline alummosilicates. This should be taken into account if CuCl2 is used to estimate Al in humus complexes. (C) 2003 Elsevier B.V. All rights reserved.
    NIR and DRIFT-MIR spectrometry of soils for predicting soil and crop parameters in a flooded field
    Groenigen, J.W. van; Mutters, C.S. ; Horwath, W.R. ; Kessel, C. van - \ 2003
    Plant and Soil 250 (2003)1. - ISSN 0032-079X - p. 155 - 165.
    infrared reflectance spectroscopy - diffuse reflectance - nitrogen analysis - organic-carbon - forest soil - decomposition - components - fractions - litter - acids
    The increasing popularity of site-specific management (SSM) calls for fast, inexpensive, simultaneous analyses of large numbers of soil variables. The objective of this study was to assess the potential of near infrared (NIR) and diffuse reflectance Fourier transformed in the mid-infrared range (DRIFT-MIR) spectrometry for predicting crop and soil parameters in a flooded California rice field. Two transects of 400 m each were left unfertilized, and 100 sample locations were established. Soil samples were taken in spring, and crop and weed samples at harvest. IR spectra were linked to total soil C and N, mineralizable N, P Olsen, effective cation exchange capacity (eCEC) and exchangeable cations (Ca, Mg, Na and K), as well as yield, N uptake, biomass and weed biomass using partial least squares regression (PLSr). The PLSr models were calibrated using 50 random observations, and validated using the remaining 50 observations. For soil, predictions for eCEC, Ca and Mg were the most accurate, with r 2 values of 0.83, 0.80 and 0.90 for NIR and 0.56, 0.60 and 0.61 for DRIFT-MIR. Correlations for P Olsen were 0.71 and 0.55, and for mineralizable N 0.46 and 0.21, respectively. No significant correlations were found for total soil C or N. For crop parameters, only weed pressure (r 2 of 0.55 and 0.44) and straw biomass (0.30 and 0.34) yielded significant correlations. The correlation with weed pressure was an indirect effect due to better competition by weeds compared to rice under low soil fertility levels. For most parameters, standard errors of prediction were lower than reported in the literature. This indicates that the small range of variability within a field might be the limiting factor in predicting these parameters. It also illustrates the limited use of correlation coefficients in PLSr model validations. We concluded that NIR spectrometry shows promise for SSM, although its predictive power for parameters may vary from site to site. Moreover, predictive models remain unique for specific agroecosystems, and therefore have to be calibrated for every area. The fast and accurate predictions for Ca and Mg concentrations in the soil could be especially important in diagnosing and combating grass tetany, which strongly depends upon Ca and Mg concentrations in the soil.
    Feldspar weathering as the key to understanding soil acidification monitoring data; a study of acid sandy soils in the Netherlands
    Mol, G. ; Vriend, S.P. ; Gaans, P.F.M. van - \ 2003
    Chemical Geology 202 (2003)39541. - ISSN 0009-2541 - p. 417 - 441.
    atmospheric deposition - woodland soils - forest soil - compositional variation - geochemical record - aluminum - water - ecosystem - rates - neutralization
    Monitoring activities pose special demands on the type of survey results needed. In the early 1990s a soil acidification monitoring methodology was adopted in the Netherlands that leaned heavily on methods developed in more fundamental research, most notably the use of proton budgets. Consequently, various controversies still not resolved in the scientific debate reflect on the current practice of soil acidity monitoring and complicate interpretation of the monitoring results. In a pilot study we address the most pressing issues: capacity versus intensity parameters, choice of monitoring objective, and natural variation in the compartment to be monitored. Focus is on the major source of buffering, the possible usefulness of the historic approach, and the regional patterns present in the sandy soils of the Netherlands. In a field campaign 92 locations in sandy regions all over the country were sampled at two depths. The solid phase, the displaced soil solution, and solid phase extractions with 0.01 M CaCl2 and 0.43 M HNO3, for the 184 samples were analyzed by a variety of methods. Aluminum release is the major source of buffering and is shown to contribute substantially to acid buffering already under natural conditions. The predominant Al bearing phases in Dutch sandy soils are feldspars and secondary Al minerals; feldspars are found to be the determinative phase in acid buffering. Application of the historic approach using the subsoil as a proxy for the initial composition of the topsoil proved feasible for this regional dataset. The average depletion of the ANC(s) of 230 mmolc kg¿1 in the topsoil matches well with estimates of the total proton load since the last ice age, with the anthropogenic contribution being between 20% and 50%. Fuzzy c-means cluster analyses of the solid phase and soil solution data show a distinct regionality that was also reflected in the parameters generally used to indicate the acidity status of soils, ¿ANC(s) and Al/BC ratios. A combined insight into both solid phase and soil solution, based on a comprehensive set of parameters, proves essential for interpreting soil acidity monitoring data.
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