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The functions of soils are intimately linked to their three‐dimensional pore space and the associated biogeochemical interfaces, mirrored in the complex structure that developed during pedogenesis. Under stress overload, soil disintegrates into smaller compound structures, conventionally named aggregates. Microaggregates (<250 µm) are recognized as the most stable soil structural units. They are built of mineral, organic, and biotic materials, provide habitats for a vast diversity of microorganisms, and are closely involved in the cycling of matter and energy. However, exploring the architecture of soil microaggregates and their linkage to soil functions remains a challenging but demanding scientific endeavor. With the advent of complementary spectromicroscopic and tomographic techniques, we can now assess and visualize the size, composition, and porosity of microaggregates and the spatial arrangement of their interior building units. Their combinations with advanced experimental pedology, multi‐isotope labeling experiments, and computational approaches pave the way to investigate microaggregate turnover and stability, explore their role in element cycling, and unravel the intricate linkage between structure and function. However, spectromicroscopic techniques operate at different scales and resolutions, and have specific requirements for sample preparation and microaggregate isolation; hence, special attention must be paid to both the separation of microaggregates in a reproducible manner and the synopsis of the geography of information that originates from the diverse complementary instrumental techniques. The latter calls for further development of strategies for synlocation and synscaling beyond the present state of correlative analysis. Here, we present examples of recent scientific progress and review both options and challenges of the joint application of cutting‐edge techniques to achieve a sophisticated picture of the properties and functions of soil microaggregates. [ABSTRACT FROM AUTHOR]

Background and aims: Paddy management results in frequent redox cycles of the soil and thus changes in the terrestrial iron (Fe) cycle. We intended to test that the increasing duration of paddy management and the increasing frequency of soil redox cycles leave their fingerprint on Fe isotope composition of paddy systems, which could subsequently be used to deduce the origin of rice plants as related to the extent of past soil paddy management. Methods: We sampled soil and rice plants of a paddy chronosequence in China with rice cultivation history up to 2000 years and determined the changes of soil Fe pools and Fe isotope composition of the soil and rice plants. Results: Prolonged paddy management reduced Fe concentrations in submerged topsoil leading to an enrichment of heavy Fe isotopes, with the δ56Fe values 0.12‰ heavier than the parent material after 2000 years. Particularly, Fe oxides were lost quickly, while exchangeable and organic-associated Fe continuously accumulated during paddy management and played an increasing role in the plant-available Fe pool in the topsoil. The Fe content in rice also increased with paddy age, while its Fe isotope composition did not reflect that of paddy soil but resembled that of the Fe plaques on the roots. Conclusion: Prolonged rice cropping altered the biological contribution in the terrestrial Fe cycle. However, while soil Fe pools that are closely linked with biological activities were affected rather quickly, the changes in the whole soil Fe system were detectable only after a millennium of paddy management. [ABSTRACT FROM AUTHOR]

The use of urea as nitrogen (N) fertilizer in agriculture needs to consider environmental, economic and resource conservation aspects because of low N‐use efficiency (NUE). Polymer‐coated urea (PCU) offers an effective way to improve the NUE of urea and to reduce its environmental trade‐offs. However, we lack information on the impact of climate and soil properties on N release from PCU. Therefore, this study was performed to quantify the effects of soil texture, moisture and temperature on the release kinetics of N from PCU. We designed a test system for soil incubation experiments and investigated three fertilizers with different release patterns, five topsoils, three moisture levels and two temperatures over 48 days. We analysed the concentrations of inorganic N (NH4+−N and NO3−−N) in the soil and estimated N release rates using the unified Richards model. Soil texture did not change the N release patterns, but release rates varied significantly among the investigated soils. Changes in soil moisture for a given soil had no effect on N release from PCU and urea when fertilizers were incorporated into the soil at conditions supportive of crop growth. Lowering soil temperatures, however, decreased N release rates from PCU by 16%–49% but only in silt loam and not in sandy loam. We conclude that PCU improves the N residence time in soil, but predictions on N release from PCU must be adapted to the prevailing environmental conditions and cannot be generalized across differently textured soils. [ABSTRACT FROM AUTHOR]

The oxygen isotopic composition of phosphate (δ18OP) in soils and surface water bodies has been used to trace terrestrial P inputs into aquatic ecosystems. However, enhanced biological activity in vegetated riparian buffer strips (VBSs) may lead to an alteration of δ18OP values. The objective of this study was to assess whether enhanced biological cycling of P in VBS soils can be identified using δ18OP values. For this purpose, we sampled temperate grassland soils at various depths along a VBS to grassland transect. Here, we combined sequential P soil extracts with an analysis of δ18OP values. Soil P pool concentrations tended to decrease significantly along the transect from the VBS to the grassland soils; the strength of this relationship varied with P extract, sample depth, and inorganic or organic bonding form. For the δ18OP values of the 1 M HCl‐extractable P we observed a significant negative trend along the VBS to grassland transect, indicating a tendency for accelerated rates of biological cycling of P within the VBS soil profile compared with the upslope soils. We conclude that oxygen isotope‐based assessments of P source contributions to freshwater bodies should consider the enhanced biological turnover of P in VBS soils. Core Ideas: Vegetated riparian buffer strips accelerate biological P cycling.Phosphate oxygen isotope values decreased along a vegetated riparian buffer strip to grassland transect.Biogeochemical P cycling varies with soil depth and distance from a stream.Cycling‐related changes in isotope values complicate stream P source identification. [ABSTRACT FROM AUTHOR]

The extreme environmental conditions and lack of water on the soil surface in hyperarid deserts hamper microbial life, allowing only highly specialized microbial communities to the establish colonies and survive. Until now, the microbial communities that inhabit or have inhabited soils of hyperarid environments at greater depths have been poorly studied. We analyzed for the first time the variation in microbial communities down to a depth of 3.4 m in one of the driest places of the world, the hyperarid Yungay region in the Atacama Desert, and we related it to changes in soil physico-chemical characteristics. We found that the moisture content changed from 2 to 11% with depth and enabled the differentiation of three depth intervals: (i) surface zone A (0–60 cm), (ii) intermediate zone B (60–220 cm), and (iii) deep zone C (220–340 cm). Each zone showed further specific physicochemical and mineralogical features. Likewise, some bacterial phyla were unique in each zone, i.e., members of the taxa Deinococcota , Halobacterota , and Latescibacterota in zone A; Crenarchaeota , Fusobacteriota , and Deltaproteobacterium Sva0485 in zone B; and Fervidibacteria and Campilobacterota in zone C, which indicates taxon-specific preferences in deep soil habitats. Differences in the microbiota between the zones were rather abrupt, which is concomitant with abrupt changes in the physical-chemical parameters. Overall, moisture content, total carbon (TC), pH, and electric conductivity (EC) were most predictive of microbial richness and diversity, while total sulfur (TS) and total phosphorous (TP) contents were additionally predictive of community composition. We also found statistically significant associations between taxa and soil properties, most of which involved moisture and TC contents. Our findings show that under-explored habitats for microbial survival and existence may prevail at greater soil depths near water or within water-bearing layers, a valuable substantiation also for the ongoing search for biosignatures on other planets, such as Mars. [ABSTRACT FROM AUTHOR]

Sustainable arable cropping relies on repeated liming. Yet, the associated increase in soil pH can reduce the availability of iron (Fe) to plants. We hypothesized that repeated liming, but not pedogenic processes such as lessivage (i.e., translocation of clay particles), alters the Fe cycle in Luvisol soil, thereby affecting Fe isotope composition in soils and crops. Hence, we analysed Fe concentrations and isotope compositions in soil profiles and winter rye from the long‐term agricultural experimental site in Berlin‐Dahlem, Germany, where a controlled liming trial with three field replicates per treatment has been conducted on Albic Luvisols since 1923. Heterogeneity in subsoil was observed at this site for Fe concentration but not for Fe isotope composition. Lessivage had not affected Fe isotope composition in the soil profiles. The results also showed that almost 100 years of liming lowered the concentration of the HCl‐extractable Fe that was potentially available for plant uptake in the surface soil (0–15 cm) from 1.03 (standard error (SE) 0.03) to 0.94 (SE 0.01) g kg−1. This HCl‐extractable Fe pool contained isotopically lighter Fe (δ56Fe = −0.05 to −0.29‰) than the bulk soil (δ56Fe = −0.08 to 0.08‰). However, its Fe isotope composition was not altered by the long‐term lime application. Liming resulted in relatively lower Fe concentrations in the roots of winter rye. In addition, liming led to a heavier Fe isotope composition of the whole plants compared with those grown in the non‐limed plots (δ56FeWholePlant_ + Lime = −0.12‰, SE 0.03 vs. δ56FeWholePlant_‐Lime = −0.21‰, SE 0.01). This suggests that the elevated soil pH (increased by one unit due to liming) promoted the Fe uptake strategy through complexation of Fe(III) from the rhizosphere, which favoured heavier Fe isotopes. Overall, the present study showed that liming and a related increase in pH did not affect the Fe isotope compositions of the soil, but may influence the Fe isotope composition of plants grown in the soil if they alter their Fe uptake strategy upon the change of Fe availability. Highlights: Fe concentrations and stocks, but not Fe isotope compositions, were more heterogeneous in subsoil than in topsoil.Translocation of clay minerals did not result in Fe isotope fractionation in the soil profile of a Luvisol.Liming decreased Fe availability in topsoil, but did not affect its δ56Fe values.Uptake of heavier Fe isotopes by graminaceous crops was more pronounced at elevated pH. [ABSTRACT FROM AUTHOR]

As a consequence of their widespread use, e.g. as protective coatings for fabrics, and their resistance to thermal and biological breakdown, perfluorinated compounds are increasingly found in the environment, but little is known about their ecotoxicological properties. A 40-day microcosm experiment was carried out to examine the effects of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) on the endogeic geophagus earthworm Aporrectodea caliginosa, its survival and feeding on soil organic C and microbial biomass C. Three levels of concentration (1, 100, and 500mgkg−1) were chosen. The lowest represented the maximum found in sediments and soils and the other two are extreme concentrations that might occur in pollution hotspots and that have been shown to poison organisms. Earthworms promoted the production of CO2 and decreased microbial biomass C in soil, regardless of the presence of PFOA or PFOS. Both compounds significantly decreased the surviving numbers and dry weight of earthworms at concentrations of 100mgkg−1. No earthworms survived at PFOA and PFOS concentrations of 500mgkg−1. At concentrations of 1mgkg−1, no negative effects were observed. The δ 13C values of A. caliginosa did not differ between treatments. In contrast, the δ 15N values were significantly increased after adding 1mgkg−1 of PFOA, reflecting elevated portions of soil-derived N in the earthworm tissue. In contrast, these portions of soil-derived N were lower in the earthworms after addition of 100mgkg−1 of PFOA and PFOS. In conclusion, extreme concentrations of PFOA and PFOS negatively affected endogeic A. caliginosa, whereas a concentration of 1mgkg−1 of PFOA and PFOS was related to an increased uptake of soil N by the earthworms. [Copyright &y& Elsevier]

More than 50% of the world's population feeds on rice. Soils used for rice production are mostly managed under submerged conditions (paddy soils). This management, which favors carbon sequestration, potentially decouples surface from subsurface carbon cycling. The objective of this study was to elucidate the long-term rates of carbon accrual in surface and subsurface soil horizons relative to those of soils under nonpaddy management. We assessed changes in total soil organic as well as of inorganic carbon stocks along a 2000-year chronosequence of soils under paddy and adjacent nonpaddy management in the Yangtze delta, China. The initial organic carbon accumulation phase lasts much longer and is more intensive than previously assumed, e.g., by the Intergovernmental Panel on Climate Change ( IPCC). Paddy topsoils accumulated 170-178 kg organic carbon ha−1 a−1 in the first 300 years; subsoils lost 29-84 kg organic carbon ha−1 a−1 during this period of time. Subsoil carbon losses were largest during the first 50 years after land embankment and again large beyond 700 years of cultivation, due to inorganic carbonate weathering and the lack of organic carbon replenishment. Carbon losses in subsoils may therefore offset soil carbon gains or losses in the surface soils. We strongly recommend including subsoils into global carbon accounting schemes, particularly for paddy fields. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the association on environmental risks because of using fluoroquinolone antibiotics in animal husbandry and human therapeutics. Difloxacin was administered to pigs and used the contaminated manure to soil, and examined the sequestration and dissipation of difloxacin in soil in the presence and absence of plants. The effect of antibiotic on nitrogen turnover in soil (potential denitrification and nitrification) is also examined. The study shows that difloxacin was very persistent and hardly (bio) accessible under all conditions studied.

Tracing back the N use efficiency of long-term fertilizer trials is important for future management recommendations. Here we tested the changes in natural N-isotope composition as an indicator for N- management within a long-term fertilization lysimeter experiment in a low mountain range pasture ecosystem at Rengen (Eifel Mountains), Germany. Cattle slurry (δ15N = 8.9 ± 0.5‰) and mineral fertilizers (calcium ammonium nitrate; δ15N = −1.0 ± 0.2‰) were applied at a rate between 0 and 480 kg N ha−1 yr−1 throughout 20 years from 1985 onwards. In 2006, samples were taken from different grass species, coarse and fine particulate soil organic matter, bulk soil and leachates. Total soil N content hardly changed during fertilization experiment. As also N leaching has been small within the stagnant water regime, most N was lost through the gaseous phase beside plant uptake and cutting. Unlike N uptake by plants, the process of N volatilization resulted in strong discrimination against the 15N isotope. As a consequence, the δ15N values of top soil samples increased from 1.8 ± 0.4‰ to 6.0 ± 0.4‰ and that of the plants from −1.2 ± 1.3‰ to 4.8 ± 1.2‰ with increasing N fertilizer rate. Samples receiving organic fertilizer were most enriched in δ15N. The results suggest that parts of the fertilizer N signal was preserved in soils and even discovered in soil organic matter pools with slow N turnover. However, a 15N/14N isotope fractionation of up to 1.5‰ added to the δ15N values recovered in soils and plants, rendering the increase in δ15N value a powerful indicator to long-term inefficient N usage and past N management in the terrestrial environment. [ABSTRACT FROM AUTHOR]

The article presents a study which determines the influence on biogeochemical dynamics and molecular-level speciation of soil sulfur. It cites that main component of the global biogeochemical sulfur cycle is soil environment. The soil environment acts as source and sink of several sulfur species and mediates oxidation state changes. The study uses elemental analysis and X-ray absorption near-edge structure (XANES) to investigate the long-term influences anthropogenically mediated transitions coming from natural to managed ecosystems.

The article reports on the results of a multiresidue determination of pesticides in acid-clay soils from Thailand. A description of the experimental set-up and measurement method is presented. The study showed that the recoveries of all pesticides from soil ranged from 68.6 to 104 percent. Also the loss of internal standards compensated for the losses of most pesticides during workup.

• Organic matter accumulation depends on pedogenic soil differentiation. • Pedogenic processes lead to soil-group-specific organic matter accrual in subsoil. • Reference Soil Groups have unique process combinations of organic matter accrual. Soil organic matter (SOM) accumulation is different in certain soil groups with differences in parent material, degree of weathering and mineral composition. These differences are modulated by climatic factors, but also by pedogenesis, in particular by the formation of reactive mineral surfaces, by soil aggregation, as well as by translocation processes such as eluviation and illuviation and different types of turbation. However, there is still a lack of conceptualization of how such processes and thus important Reference Soil Groups influence the composition and properties of OM. Here we summarize the basic processes of OM storage as they differ from soil group to soil group, in order to present a first overview of the processes of OM formation in the different terrestrial soils of the world. We distinguish between soils of different climatic zones, i.e. Cryosols in permafrost regions, soils of limited development (Cambisols), Podzols, Phaeozems, Chernozems, Kastanozems, and Luvisols in temperate climate zones, as well as Acrisols, Ferralsols, Plinthosols and Nitisols in the subtropics and tropics. We also include soils derived from a specific parent material (Andosols, Vertisols), as well as Anthrosols (paddy soils, Terra Preta, plaggen soils) as examples for human-made SOM accumulations. The compilation of the literature shows that research on OM is clearly focused on specific Reference Soil Groups in temperate climate zones and some man-made soils, while other soils such as Nitisols and Acrisols are clearly underrepresented. The contribution of the different soil groups to global organic carbon (OC) stocks varies, with large amounts of OC found for the first metre in Cryosols, Cambisols, and Podzols, due to the large land area they cover, followed by Acrisols and Ferralsols. In part, these differences can be attributed to differences in the formation of SOM, which we ascribe to three main mechanisms. We emphasize that in all major Reference Soil Groups, both the mechanism of sorptive conservation as well as the protection within the aggregates contribute to the storage of OM. However, the reactant partners and aggregate forming agents and therewith the intensity of these stabilisation processes vary among the Reference Soil Groups. As a result, there are differences in the SOM composition in the topsoil. Within the entire soil profile, however, pedogenic processes lead as third mechanism to soil-group-specific accrual of SOM in the subsoil, e.g. by means of illuviation, by cryo-/bio-, and peloturbation, as well as by management. We conclude that the specific pedogenic environment must be considered in the assessment of global SOM storage potentials and thus also in future global C models. [ABSTRACT FROM AUTHOR]

• Nanocolloids dominated soil colloids in Acrisols. • Fine and medium-sized colloids dominated soil colloids in Terra Preta soils (TP). • Elevated pH and Ca2+ conc. correlated with SOM involvement in colloid formation in TP. • Enriched water-extractable and colloidal P in TP. Amazonian Dark Earths (or terra preta de índico) are known as highly fertile soils that can maintain elevated crop yields for centuries. While this fertility was frequently ascribed to the presence of black carbon, the availability and colloidal binding of major nutrients received limited attention. We examined the size distribution and the elemental compositions of water-dispersible colloids (WDC) in both forested and cultivated Terra Preta topsoils (0–10 cm, Anthrosols), as well as in their adjacent non-Terra Preta controls (Acrisols) via asymmetric flow field-flow fractionation (FFF). Liquid-state 31P-nuclear magnetic resonance (NMR) spectra, black carbon content, and scanning electron microscope (SEM) images were also obtained. We found that WDC in Terra Preta soils contained a significant proportion of organo-mineral associations in the size range 30–300 nm, whereas, in contrast, water-dispersible nanoparticles with a diameter < 30 nm were dominant in the adjacent Acrisols. The shifts to larger WDC sizes in the Terra Preta soils went along with elevated pH values, as well as with elevated contents of Si, Al, Fe, Ca and organic matter-containing particles. Also P concentrations were enriched in both the water-extractable phase (WEP) and WDC extracts of Terra Preta soils relative to the adjacent Acrisols. We assume that the higher pH values and Ca ion concentrations promoted the involvement of soil organic matter (SOM) into the formation of larger-sized colloids consisting of kaolinite-like clay minerals, iron oxides and Ca ions in the Terra Preta soils. The elevated content of Ca in Terra Preta soil colloids may also contribute to the retention of P, likely via bridging of anionic P like orthophosphate to SOM. Preventing soil acidification is thus not only to be recommended for Acrisols, but also for maintaining colloidal structures and related fertility in Terra Preta soils. [ABSTRACT FROM AUTHOR]

Agricultural management is a key force affecting soil processes and functions. Triggered by biophysical constraints as well as rapid structural and technological developments, new management practices are emerging with largely unknown impacts on soil processes and functions. This impedes assessments of the potential of such emerging practices for sustainable intensification, a paradigm coined to address the growing demand for food and nonfood products. In terms of soil management, sustainable intensification means that soil productivity is increased while other soil functions and services, such as carbon storage and habitat for organisms, are simultaneously maintained or even improved. In this paper we provide an overview of research challenges to better understand how emerging soil management practices affect soil processes and functions. We distinguish four categories of soil management practices: spatial arrangements of cropping systems, crops and rotations, mechanical pressures, and inputs into the soil. Key research needs identified for each include nutrient efficiency in agroforestry versus conventional cropping systems, soil-rhizosphere microbiome elucidation to understand the interacting roles of crops and rotations, the effects of soil compaction on soil-plant-atmosphere interactions, and the ecotoxicity of plastics, pharmaceuticals and other pollutants that are introduced into the soil. We establish an interdisciplinary, systemic approach to soil science and include cross-cutting research activities related to process modeling, data management, stakeholder interaction, sustainability assessment and governance. The identification of soil research challenges from the perspective of agricultural management facilitates cooperation between different scientific disciplines in the field of sustainable agricultural production. [ABSTRACT FROM AUTHOR]

• Soil microaggregates revealed highly heterogenous compound composition. • Organic C accumulated at several sites in aggregates and at surfaces. • Spatial co-abundance of plant and microbial matter correlated with C accrual. • No spatial correlation between organics and minerals was found. The physical arrangement of compounds in soil microaggregates is controlling many ecosystem functions such as soil stability and C sequestration. However, little is known about the spatial arrangement of organic and inorganic compounds in soil microaggregates, due to the lack of in-situ analyses of undisturbed material. We hypothesized that microaggregates are spatially organized due to interactions between organic matter and mineral phases. To test this, we separated the water stable, occluded, large and small microaggregate fractions (250–53 and 53–20 µm, 60 J ml−1 dispersion energy) from Ap horizons of a toposequence of sandy to loamy Luvisols (Germany) with increasing clay contents (19 to 35% clay), and subjected in total 60 individual aggregates to elemental mapping by electron probe micro analysis (EPMA), which recorded C, N, P, Al, Fe, Ca, K, Cl, and Si contents at 1 × 1 µm resolution. Stoichiometric element ratios characteristic for organic and inorganic matter were used to define discrete components of the aggregates and analyze their spatial arrangement. We found a pronounced heterogeneity in content and arrangement of discrete aggregate components, which was not reproducible for different specimens from the same soil microaggregate fraction, and thus largely independent of clay content in soil. However, nearest neighbor analyses revealed close spatial correlations between plant detritus (C:N app. 100:10) and microbial organic matter (C:N app. 10:1) indicating a spatial relationship between source and consumer. There was no systematic relationship between soil minerals and organic matter, suggesting that well-established macroscale correlations between contents of pedogenic oxides and clay minerals with soil organic matter storage do not apply to soil microaggregates. [ABSTRACT FROM AUTHOR]

• Apple replant disease is reflected in a huge in-field variability of tree growth. • Plants showing most stunted shoot growth revealed lowest δ 15N values in the rhizosphere. • Apple replant disease severity is correlated to a reduced micronutrient supply of Mn and Co for infected plants up to 100 cm shoot length. Orchards affected by apple replant disease may show a distinct in-field variability of the severity of apple replant disease (ARD) symptoms. As abiotic soil properties can affect pathogen survival but show considerable variability at the scale of a few meters, we hypothesized that the variability of abiotic soil properties may be used to explain parts of the in-field variability of ARD. We sampled soil and rhizosphere of 32 apple trees with different degree of ARD symptoms after two years of growth at the horticultural research station Heidgraben, Germany. The sandy soils correspond to Entic Podzols. Soil analyses comprised soil aggregate-size fractionations, the assessment of the stocks of nitrogen and essential macro- and micronutrients, as well as a tracing of stable δ 15N natural abundance both in rhizosphere and non-rhizosphere soil. The results showed that there was indeed a huge in-field variability of tree growth, following a Gaussian distribution, but classified here in shoot heights of < 40, 40–80, 80–120, and >120 cm, respectively. An effect of soil aggregation on ARD or vice versa was not detected. Elevated tree growth, however, went along with a consumption of soil macronutrients (R2: = 0.3 – 0.8 for the n = 4 ARD classes; significant only for K on individual plant basis). Intriguingly, opposite correlations were observed for micronutrients, where reduced tree growth occurred at subsites short in micronutrient supply (R2 = 0.9 for Mn and Co, significant for Mn and Co for ARD infected plants up to 100 cm shoot length on individual plant basis). Moreover, the plants showing most stunted shoot growth revealed lowest δ 15N values in the rhizosphere, as typical for reduced N cycling. Our data therefore confirm that at least parts of the in-field variability of ARD severity is correlated to reduced micronutrient supply and N cycling, possibly via effects on habitat properties of pathogenic soil microbiota. [ABSTRACT FROM AUTHOR]

Drained peatlands are hotspots of carbon dioxide (CO 2) emissions from agricultural soils. As a consequence of both drainage-induced mineralisation and anthropogenic mixing with mineral soils, large areas of former peatlands under agricultural use underwent a secondary transformation of the peat (e.g. formation of aggregates). These soils show contents of soil organic carbon (SOC) at the boundary between mineral and organic soils. However, the carbon (C) dynamics of such soils have rarely been studied so far. The aim of the present study was to evaluate the vulnerability of soil organic matter (SOM) to decomposition over the whole range of peat-derived soils under agriculture including very carbon rich mineral soils (76–526 g kg−1 SOC). A total of 62 soil samples covering a broad range of soil and site characteristics were selected from the sample set of the German Agricultural Soil Inventory. Potential CO 2 production was measured by aerobic incubation. Fen and bog peat samples were grouped into disturbance classes according to their soil properties. Specific basal respiration rates (SBR), i.e. CO 2 fluxes per unit SOC, showed the highest values for the most disturbed samples for both fen peat (13.9 ± 6.0 μg CO 2 -C g SOC−1 h−1) and bog peat (10.9 ± 4.7 μg CO 2 -C g SOC−1 h−1). Respiration rates of bog peat increased more strongly with an increasing degree of disturbance than those of fen peat. Perhaps counterintuitively, SOM vulnerability to decomposition thus increased with an increasing degree of disturbance and a decreasing SOC content, indicating positive feedback mechanisms as soon as peat soils are disturbed by drainage. Furthermore, the variability of the SBR increased drastically with increasing degree of disturbance. The turnover of SOM in less disturbed peat samples tended to be higher in samples with higher nitrogen (N) content, higher pH value and lower C:N ratio, while plant-available phosphorus was important for the mineralisation of more severely disturbed peat. However, clear correlations between a single soil property and SBR could not be identified. The high potential of CO 2 emissions from organic soils with a low SOC content implies that mixing organic soil with mineral soil does not seem to be a promising option for mitigating greenhouse emissions. • Specific basal respiration (SBR) determined by aerobic incubation as a measure of vulnerability. • Higher and more variable SBR rates for stronger degraded organic soils. • Bog peat seems to be more vulnerable than fen peat. • High plant-available phosphorus contents increase SBR rates. • SBR rates of heavily disturbed samples remain unpredictable. [ABSTRACT FROM AUTHOR]

Despite numerous studies about the change of soil biogeochemical properties by climate alternation driven by elevation, latitude, etc. in arid to hype-arid regions, little is known about soil colloids (1-1000 nm) and nanoparticles (1-100 nm) as nutrient carriers and which events are driving this in such environments. We investigated the size and composition of water dispersible colloids (WDCs) to quantify colloidal bound C and P from three depth profiles in an altitudinal transect in the Atacama Desert (Paposo region) using asymmetric field flow field fractionation (A-FFFF) coupled online to various detectors (ICP-MS, organic carbon detector (OCD) and UV). One of the profiles (A; 200 cm) was located in a semi-arid part and the two others (70 cm depth) in an arid area in the vicinity of each other (B on an abandoned alluvial fan, and C on the more active part of the fan). Three size categories of WDCs were detected based on the FFF results, including nanoparticles from 0.6 to 24 nm, fine colloids from 24 to 210 nm, and medium colloids from 210 to 500 nm. Nanoparticles and soil colloids accounted for up to 60% of the bioavailable P concentration (Olsen P) at the surface layer of profile C. Moreover, the contribution of colloidal Corg to total Corg was 5% at the surface of profile A, with a maximum of 11% at depth of 115 cm, and maximum 1% at the surface layer of both profiles B and C. The size distribution of colloids and their elemental content was significantly different between B and C especially at upper 20 cm. Our results, showing pronounced local differences in soil colloidal properties, suggest that colloidal matter (here mainly C and P) preserved in the Atacama deserts is terrestrial proxy record of both local (e.g. intermittent drainage events) and larger scale (periods of dust input) of environmental changes which have occurred in this part of South America. [ABSTRACT FROM AUTHOR]