| 1. |
- KAMBLE, Pramod N., et al.
(författare)
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Carbon and Nitrogen Amendments Lead to Differential Growth of Bacterial and Fungal Communities in a High-pH Soil
- 2018
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Ingår i: Pedosphere. - 1002-0160. ; 28:2, s. 255-260
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Tidskriftsartikel (refereegranskat)abstract
- Microbial growth in soil is mostly limited by lack of carbon (C). However, adding fresh, C-rich litter can induce nitrogen (N) limitation. We studied the effect of alleviating C and N limitation in high-pH (> 8) soils, soils expected to favor bacterial over fungal growth. Nitrogen limitation was induced by incubating soils amended with C-rich substrate (starch or straw) for 4 weeks. Limiting nutrients and the effects of alleviating limitation were then studied by adding C (as glucose) or N (as NH4NO3) and measuring microbial growth and respiration after 4 d. In non-amended, C-limited soils, adding C but not N increased both microbial respiration and bacterial growth. In N-limited, substrate-amended soils, adding C increased respiration, whereas adding N increased both microbial respiration and growth. Inducing N limitation by amending with straw was most easily detected in increased fungal growth after the addition of N, whereas with starch, only bacterial growth responded to alleviating N limitation. Compared to earlier results using a low-pH soil, the effect of substrate used to induce N limitation was more important than pH for inducing bacterial or fungal growth after alleviating N limitation. Furthermore, we found no evidence that alleviating N limitation resulted in decreased respiration concomitant with increased microbial growth in soil, suggesting no drastic changes in C use efficiency.
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| 2. |
- REWCASTLE, Kenna E., et al.
(författare)
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Investigating drivers of microbial activity and respiration in a forested bog
- 2020
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Ingår i: Pedosphere. - 1002-0160. ; 30:1, s. 135-145
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Tidskriftsartikel (refereegranskat)abstract
- Northern peatlands store nearly one-third of terrestrial carbon (C) stocks while covering only 3% of the global landmass; nevertheless, the drivers of C cycling in these often-waterlogged ecosystems are different from those that control C dynamics in upland forested soils. To explore how multiple abiotic and biotic characteristics of bogs interact to shape microbial activity in a northern, forested bog, we added a labile C tracer (13C-labeled starch) to in situ peat mesocosms and correlated heterotrophic respiration with natural variation in several microbial predictor variables, such as enzyme activity and microbial biomass, as well as with a suite of abiotic variables and proximity to vascular plants aboveground. We found that peat moisture content was positively correlated with respiration and microbial activity, even when moisture levels exceeded total saturation, suggesting that access to organic matter substrates in drier environments may be limiting for microbial activity. Proximity to black spruce trees decreased total and labile heterotrophic respiration. This negative relationship may reflect the influence of tree evapotranspiration and peat shading effects; i.e., microbial activity may decline as peat dries and cools near trees. Here, we isolated the response of heterotrophic respiration to explore the variation in, and interactions among, multiple abiotic and biotic drivers that influence microbial activity. This approach allowed us to reveal the relative influence of individual drivers on C respiration in these globally important C sinks.
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| 3. |
- Kirchmann, Holger
(författare)
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Wheat yield prediction by zero sink and equilibrium-type soil phosphorus tests
- 2022
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Ingår i: Pedosphere. - 1002-0160 .- 2210-5107. ; 32, s. 543-554
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Tidskriftsartikel (refereegranskat)abstract
- Diffusive gradients in thin films (DGT) measurements have been shown to outperform other phosphorus (P) tests in soils with strong P sorption, but this has not been confirmed for moderately weathered European soils. We compared the performance of DGT in predicting wheat grain yield in Swedish long-term fertility experiments with those of standard intensity (water-extractable P (P-H2O)) and quantity (ammonium lactate-extractable P (P-AL)) tests. A Mitscherlich-type model was used to fit wheat yield response to P application rates (0, 15, 30 or 35, and 45 kg P ha(-1) year in each individual trial replicate to estimate the maximum yield. For trials with clear plateau-type yield responses and the goodness of fit (R-2) > 0.75, relative yields (RYs) were calculated for each P treatment and plotted against the soil P test results (n = 143). The goodness of the Mitscherlich-type fits decreased in the following order: DGT-measured P (P-DGT) (R-2 = 0.35) > P-H2O (R-2 = 0.18) > P-AL (R-2 = 0.13). When excluding soils with P-AL:P-DGT >= 0.1 L g(-1), R-2 was considerably improved to 0.55 for P-AL, 0.46 for P-H2O, and 0.65 for P-DGT (n = 61). At 95% of maximum yield, the upper limit of P deficiency for P-DGT was 44.8 (the soils with P-AL:P-DGT < 0.1 L g(-1)) and 61.9 mu g L-1 (all soils), falling within the range reported for other European and Australian soils (6.0-142 mu g L-1). We show that in the investigated Swedish soils, DGT performed better than the quantity and intensity tests, which is attributed to its ability to capture P diffusion and resupply from the soil solid phase, similar to plant roots in the rhizosphere.
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| 4. |
- Kumpiene, Jurate, et al.
(författare)
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Assessment of Methods for Determining Bioavailability of Trace Elements in Soils : A Review
- 2017
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Ingår i: Pedosphere. - : Elsevier. - 1002-0160 .- 2210-5107. ; 27:3, s. 389-406
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Tidskriftsartikel (refereegranskat)abstract
- Trace element-contaminated soils (TECSs) are one of the consequences of the past industrial development worldwide. Excessive exposure to trace elements (TEs) represents a permanent threat to ecosystems and humans worldwide owing to the capacity of metal(loid)s to cross the cell membranes of living organisms and of human epithelia, and their interference with cell metabolism. Quantification of TE bioavailability in soils is complicated due to the polyphasic and reactive nature of soil constituents. To unravel critical factors controlling soil TE bioavailability and to quantify the ecological toxicity of TECSs, TEs are pivotal for evaluating excessive exposure or deficiencies and controlling the ecological risks. While current knowledge on TE bioavailability and related cumulative consequences is growing, the lack of an integrated use of this concept still hinders its utilization for a more holistic view of ecosystem vulnerability and risks for human health. Bioavailability is not generally included in models for decision making in the appraisal of TECS remediation options. In this review we describe the methods for determining the TE bioavailability and technological developments, gaps in current knowledge, and research needed to better understand how TE bioavailability can be controlled by sustainable TECS management altering key chemical properties, which would allow policy decisions for environmental protection and risk management
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| 5. |
- Menichetti, Lorenzo, et al.
(författare)
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Chemical Properties and Biochemical Activity of Colonized and Abandoned Litter-Feeding Termite (Macrotermes spp.) Mounds in Chromic Cambisol Area on the Borana Plateau, Ethiopia
- 2014
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Ingår i: Pedosphere. - 1002-0160 .- 2210-5107. ; 24, s. 399-407
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Tidskriftsartikel (refereegranskat)abstract
- Termite (Macrotermes spp.) mounds are complex biological habitats originated by the termite activity and possessing peculiar physical, chemical and biochemical properties. In this study we examined the concentration of nutrients and the biochemical activity of abandoned soil and mounds colonized by termites of the genera Macrotermes located in the Borana District, Ethiopia. To elucidate the magnitude and persistence of the termite-induced effects, we also studied an abandoned mound, previously colonized by termites of the same genera formed on the same soil. Results confirmed that termite-colonized mounds are 'hot spots' of nutrient concentration and microbial activity in tropical soils. This is due to the termite driven litter input and decomposition. The abandoned mounds showed higher microbial biomass and activity and displayed a nutrient redistribution and a greater microbial activity than the adjacent soils. These findings allowed us to hypothesize a model of nutrient cycling in colonized soils and a partition of the relative roles of termites and soil microorganisms in nutrient location and turnover in tropical soils. These results may be also useful for the optimal management of termite-colonized soils.
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| 6. |
- Meurer, Katharina
(författare)
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Evaluating Emissions of Nitrous Oxide from Cropland Soils Under Different Rotations in Mato Grosso, Brazil: A Scenario Simulation Study
- 2019
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Ingår i: Pedosphere. - 1002-0160 .- 2210-5107. ; 29, s. 432-443
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Tidskriftsartikel (refereegranskat)abstract
- Expansion of cropland involves immense land use changes, and the resulting intensified management practices have a strong influence on the functioning of the underlying soil. For instance, increased application of nitrogen (N) fertilizer is known to enhance fluxes of nitrous oxide (N2O) from the soil to the atmosphere. The emission factor (EF) proposed by the Intergovernmental Panel on Climate Change (IPCC) assumes a linear relationship between added N and N2O-N fluxes, but it does not account for environmental factors, such as soil properties or climate. Due to the high spatial and temporal variability of N2O-N fluxes, mechanistic models are preferable in terms of extrapolation to larger scales. In this study, we evaluated simulated N2O-N fluxes from soils under agricultural use in the Brazilian state, Mato Grosso, using the CANDY (Carbon and Nitrogen Dynamics) model. A control tool was developed in order to enable the simulation of 1 650 scenarios covering different sites (soil + climate) and management regimes (crop rotation + amount of applied fertilizer + sowing and harvesting dates). Results suggested that the sites had a very strong influence on calculated emissions, which is not accounted for by static EF. Furthermore, most fertilizer-induced N2O-N fluxes derived from the scenario simulations were best described by a non-linear function. For sounder budgeting on the federal and national scale, there is still a strong need for long-term observations of continuous crop rotations and spatial distribution of soil types and their specific characteristics. The presented results provide a valuable starting point for developing further scenario simulations and adapting experimental campaigns for N2O emission study.
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| 7. |
- Wu, Mousong, et al.
(författare)
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Water, Salt and Heat Influences on Carbon and Nitrogen Dynamics in Seasonally Frozen Soils in Hetao Irrigation District, Inner Mongolia, China
- 2019
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Ingår i: Pedosphere. - : SCIENCE PRESS. - 1002-0160 .- 2210-5107. ; 29:5, s. 632-641
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Tidskriftsartikel (refereegranskat)abstract
- To investigate carbon soils under saline and shallow groundwater supply conditions, in-situ lysimeter experiments with different groundwater table depths (WTD = 1.8 and 2.2 m) were conducted in Inner Mongolia, China during the wintertime of 2012-2013. Changes in soil organic C and total N in multiple layers during various periods, as well as their relationships with soil water, salt, and heat dynamics were analyzed. Accumulation of soil organic C and total N during freezing periods was strongly related to water and salt accumulation under temperature and water potential gradients. Water and salt showed direct influences on soil C and N dynamics by transporting them to upper layer and changing soil microbial activity. Salt accumulation in the upper layer during freezing and thawing of soil affected microbial activity by lowering osmotic potential, resulting in lower C/N ratio. Nitrogen in soil tended to be more mobile with water during freezing and thawing than organic C, and the groundwater table also served as a water source for consecutive upward transport of dissolved N and C. The changes in C and N in the upper 10 cm soil layer served as a good sign for identification of water and salt influences on soil microbial activity during freezing/thawing.
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| 8. |
- LI, Jian, et al.
(författare)
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Comparative analysis of planted and unplanted controls for assessment of rhizosphere priming effect
- 2022
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Ingår i: Pedosphere. - : Elsevier BV. - 1002-0160. ; 32:6, s. 884-892
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Tidskriftsartikel (refereegranskat)abstract
- The rhizosphere priming effect (RPE) is increasingly being considered to be an important regulator of soil organic matter (SOM) decomposition and nutrient turnover, with potential importance for the global CO2 budget. As a result, studies on the RPE have rapidly increased in number over the last few years. Most of these experiments have been performed using unplanted soil as the control, which could potentially lead to incorrect assessment of the RPE. Therefore, we performed a greenhouse experiment to investigate how the choice of control (i.e., unplanted control and planted control) influenced the quantification of RPE on SOM decomposition and gross nitrogen (N) mineralization, and to link this to differences in microbial and abiotic soil properties between the two controls. In the planted control, planted seedlings were cut at soil surface 5 d before measurement of the RPE. The RPE on SOM decomposition was positive in pine soil and almost 2-fold higher when calculated from the planted control than from the unplanted control. In spruce soil, a negative RPE on SOM decomposition was found when calculated from the planted control, while the RPE was positive when calculated from the unplanted control. No RPE on gross N mineralization was found when calculated from the planted control, while a positive RPE of more than 100% was found when calculated from the unplanted control. The microbial biomass and growth rate were lower, while the inorganic N content was higher in the unplanted control than in the planted control. The microbial community composition and potential enzyme activity in the planted treatment and planted control were similar, but they differed significantly from those in the unplanted control. The results showed that the RPE varied widely depending on the choice of control; thus, we suggest that a planted control, in which the aboveground plant parts are removed only a few days before the measurement of RPE, should be used as the control when elucidating the RPE on belowground C and N cycling responses to environmental change.
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