| 1. |
- Almeida, Juan Pablo, et al.
(författare)
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Phosphorus regulates ectomycorrhizal fungi biomass production in a Norway spruce forest
- 2023
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Ingår i: Biogeosciences. - : Copernicus Publications. - 1726-4170 .- 1726-4189. ; 20:7, s. 1443-1458
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Tidskriftsartikel (refereegranskat)abstract
- Ectomycorrhizal fungi (EMF) are important components of soil microbial communities, and EMF biomass can potentially increase carbon (C) stocks by accumulating in the soils as necromass and producing recalcitrant structures. EMF growth depends on the C allocated belowground by the host trees, and the nutrient limitation on tree growth is expected to influence this allocation. Therefore, studying EMF production and understanding the factors that regulates it in natural soils are important to understand C cycling in forests.Fungal mycelium collected from ingrowth mesh bags is commonly used to estimate EMF biomass, but these measurements might not reflect the total EMF production since turnover rates of the hyphae are not considered. Here we estimated EMF production and turnover in response to P fertilization (applied as superphosphate) in a Norway spruce forest where nitrogen (N) deposition has resulted in phosphorus (P) limitation of plant production by using a combination of mesh bags with different incubation periods and with Bayesian inferences. To test how localized patches of N and P influence EMF production and turnover we amended some bags with a nitrogen source (methylene urea) or P source (apatite). Additionally, the Bayesian model tested the effect of seasonality (time of mesh-bag harvesting) on EMF production and turnover.We found that turnover of EMF was not affected by P fertilization or mesh-bag amendment. P fertilization had a negative effect on EMF production in all the mesh-bag amendments, suggesting a reduced belowground C allocation to the EMF when P limitation is alleviated. Apatite amendment significantly increased EMF biomass production in comparison with the pure quartz bags in the control plots but not in the P-fertilized plots. This indicates that P-rich patches enhance EMF production in P-limited forests, but not when P is not limiting. Urea amendment had a generally positive effect on EMF production, but this was significantly reduced by P fertilization, suggesting that a decrease in EMF production due to the alleviated P limitation will affect N foraging. Seasonality had a significant effect on EMF production, and the differences registered between the treatments were higher during the warmer months and disappeared at the end of the growing season.Many studies highlight the importance of N for regulating belowground C allocation to EMF in northern coniferous forests, but here we show that the P status of the forest can be equally important for belowground carbon allocation to EMF production in areas with high N deposition.
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| 2. |
- Bolinder, Martin, et al.
(författare)
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Ensemble modelling, uncertainty and robust predictions of organic carbon in long-term bare-fallow soils
- 2021
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 27, s. 904-928
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Tidskriftsartikel (refereegranskat)abstract
- Simulation models represent soil organic carbon (SOC) dynamics in global carbon (C) cycle scenarios to support climate-change studies. It is imperative to increase confidence in long-term predictions of SOC dynamics by reducing the uncertainty in model estimates. We evaluated SOC simulated from an ensemble of 26 process-based C models by comparing simulations to experimental data from seven long-term bare-fallow (vegetation-free) plots at six sites: Denmark (two sites), France, Russia, Sweden and the United Kingdom. The decay of SOC in these plots has been monitored for decades since the last inputs of plant material, providing the opportunity to test decomposition without the continuous input of new organic material. The models were run independently over multi-year simulation periods (from 28 to 80 years) in a blind test with no calibration (Bln) and with the following three calibration scenarios, each providing different levels of information and/or allowing different levels of model fitting: (a) calibrating decomposition parameters separately at each experimental site (Spe); (b) using a generic, knowledge-based, parameterization applicable in the Central European region (Gen); and (c) using a combination of both (a) and (b) strategies (Mix). We addressed uncertainties from different modelling approaches with or without spin-up initialization of SOC. Changes in the multi-model median (MMM) of SOC were used as descriptors of the ensemble performance. On average across sites, Gen proved adequate in describing changes in SOC, with MMM equal to average SOC (and standard deviation) of 39.2 (+/- 15.5) Mg C/ha compared to the observed mean of 36.0 (+/- 19.7) Mg C/ha (last observed year), indicating sufficiently reliable SOC estimates. Moving to Mix (37.5 +/- 16.7 Mg C/ha) and Spe (36.8 +/- 19.8 Mg C/ha) provided only marginal gains in accuracy, but modellers would need to apply more knowledge and a greater calibration effort than in Gen, thereby limiting the wider applicability of models.
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| 3. |
- Bolinder, Martin, et al.
(författare)
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Implementing a new version of ICBM in NIR
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the sector Land Use, Land-Use Change and Forestry (LULUCF, CRF sector 4) within the national greenhouse gas inventory (NIR), Sweden is applying a Tier 3 method for estimating the loss or gain of soil organic carbon (SOC) stocks for cropland on mineral soils to a depth of 0.25 m. The Introductory Carbon Balance Model (ICBM) is used for calculating stock change rates in eight agricultural production regions and results are aggregated to the national level. Calculations involves yearly agricultural census data and daily weather records, as well as results from a national soil-monitoring program (SMP) on soil carbon contents. Initially, only data from the first sampling of the national SMP were used for initializing ICBM. Since the first soil inventory, two additional samplings within the SMP have become available. Simultaneously, we have also gained more knowledge about SOC dynamics. In a development project last year, we were re-analyzing the complete records of data from the last two decades of the SMP confirming that SOC stocks are increasing, and we were starting to calibrate a new version of ICBM. The purpose of the project this year was to implement the new ICBM version in the NIR system.The results show that the new version of ICBM simulates increasing SOC stocks for the period 1990 to 2018, which is thereby more consistent with estimates from the national SMP data than results obtained using the previous ICBM version. The ICBM and SMP assessment methods of SOC stock changes are complementing each other, and both have their inherent limitations. Our analysis with both methodologies are still not fully completed. There remain some fine-tuning in the new ICBM version. Furthermore, we are continuously working on improving the interpretation regarding SOC stocks in the current database from the national SMP. Maintaining the latter and repeating the sampling at least once more would also substantially improve the value of this database.
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| 4. |
- Bolinder, Martin, et al.
(författare)
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New calibration of the ICBM model & analysis of soil organic carbon concentration from Swedish soil monitoring programs
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We are using the Introductory Carbon Balance Model (ICBM) within the national inventory reporting (NIR) system for estimating changes in soil organic carbon (SOC) stocks in Swedish arable land for mineral soils. The first version of ICBM was developing from a long-term experiment (LTE) in Ultuna Sweden, with a time-series of data from 1956 to 1991. The model is initialized using data from a soil database and information from Swedish soil monitoring programs (SMPs). For that purpose, it specifically uses data from the first inventory of the Swedish Environmental Protection Agency (SEPA) SMP conducted in the early 1990s. Since the 1990s, the SEPA SMP has conducted two further inventories in a 10-year cycles, with the last inventory completed in 2017. In complement to this SEPA SMP, the Swedish Board of Agriculture (SJV) was completing a spatially more detailed SMP in 2011 and 2012. In an earlier study, when the third inventory of SEPA was still not fully completed, we showed that SOC concentrations are increasing in Swedish arable mineral soils during the past two decades. Simulations with the current version of ICBM are not reproducing this long-term increasing trend.The main purposes of this project were to (i) calibrate a second version of ICBM by incorporating new knowledge gained from LTEs, (ii) evaluate the trends in SOC concentrations with the complete inventories (I, II and III) of SEPA, (iii) compare results from SEPAs last inventory (III) with that of SJV SMP conducted at approximately the same time period. A Bayesian approach was selected for calibrating the second version of ICBM, using an updated time series of data from Ultuna ending in 2017, and by also including experimental data (1996-2017) from a new sister experiment at Lanna in southern Sweden. For adequately comparing the SEPA and SJV SMPs, we were correcting data from the SJV samples so that we could express all results for SOC concentrations on a basis equivalent to dry combustion. Our analysis on the complete SEPA inventories are generally confirming our previous assessment. However, a more detailed exploration using data only from inventories II and III having identical sampling coordinates, clearly indicates that the increases in SOC concentrations were less in the last decade than in the previous one. Furthermore, when comparing SOC concentrations at different spatial scales, the positive trend in SOC concentrations is much more obvious on the scale of Swedish agricultural production regions (eight regions). Indeed, at the scale of the twenty-one Swedish counties, there are few significant differences and the increasing trend is unclear for many of the counties. This is reflecting difficulties related to the density of sampling points in the SEPA SMP; each of them roughly represents 1500 ha of arable land. Besides, only two decades or even only one decade since SEPA was regarding inventory II as a restart of their SMP, remain a short time period in detecting changes in SOC and highlight the importance of maintaining continuous SMPs.We found the comparisons between the SJV and SEPA SMPs useful but further work is necessary to refine the linkage. The overall changes in parameter values related to SOC dynamics for the calibrated second version of ICBM, will give simulations towards higher SOC stocks, compared to the current version. The main parameter explaining this differences is the increased contribution of below ground (i.e., roots) annual C inputs to soil contributing to the formation of more stable SOC. The approach we used here also offers the advantage of making a multi-site calibration and we could in the future, further refine parameter values by including other Swedish LTEs. Additionally, it allows us to include an estimate for uncertainty in the predictions of SOC stocks, which we could also develop for inclusion in the NIR system.
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| 5. |
- Börjesson, Gunnar, et al.
(författare)
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Markbiologisk uppföljning i åkermark : en undersökning av fosfolipidfettsyror (PLFA) som möjlig mikrobiologisk indikator
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Monitoring and assessment of agricultural soils has become requested as means to detect changes in soil quality. Among possible microbial indicators for monitoring soil quality, the most common methods include microbial biomass, respiration, N mineralization and a community profiling method. Among the latter, the most used seem to be DGGE (denaturing gradient gel electrophoresis), PLFA (phospholipid fatty acids), and CLPP (community level physiology profile) analyses. Here we report results from an investigation of the PLFA analysis for the possible use as an indicator for monitoring soil quality. Soil samples were taken 2009 in the Ultuna soil organic matter field experi-ment, which was started in 1956 for investigating the long-term effect of mineral N fertilizers and different organic amendments on crop yields, soil organic matter changes and soil physical properties. PLFAs were extracted from top- and subsoils in ten treatments. PLFA concentrations were compared to other variables, such as total carbon, total nitrogen, pH and respiration, but also to other results reported earlier from the same experiment. Total PLFAs in topsoil samples (0-20 cm) were highest in the sewage sludge (O) treatment, which was almost reflected in subsoil samples, although the highest mean value among those samples was found for the farmyard manure (J) treatment. A good correlation was observed between total PLFAs in topsoil samples and total carbon, but total PLFAs were even better correlated with total nitrogen (r=0.81; p<0.0001). Subsoil samples (27-40 cm depth) reflected topsoil samples for total PLFAs, but the individual PLFAs revealed that the composition of the microbial communities were entirely different. The presence of cyclic fatty acids in the sewage sludge treatment indicated some kind of stress for gram-negative bacteria, probably caused by heavy metals, although a negative effect of the sewage sludge application could not be seen in other ways, e.g. crop yield. In conclusion, the PLFA analysis can give valuable information about the microbial community in soil samples. It can be used in a monitoring programme, although the recommendation is that it would be preferable to combine the PLFA analysis with other methods, for example CLPP, in order to determine trends and changes of microbial communities and activities in soils
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| 6. |
- Börjesson, Gunnar, et al.
(författare)
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Seasonal dynamics of the soil microbial community: assimilation of old and young carbon sources in a long-term field experiment as revealed by natural C-13 abundance
- 2016
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Ingår i: European Journal of Soil Science. - : Wiley. - 1351-0754 .- 1365-2389. ; 67, s. 79-89
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Tidskriftsartikel (refereegranskat)abstract
- Microbial biomass is a small part of the total soil organic carbon (SOC) pool, but plays a major role in its turnover. A field experiment in Sweden, amended with different mineral and organic materials since 1956, was changed from continuous C3 plants to C4 vegetation (silage maize) in 2000. In 2012, soil samples from three fertilizer treatments (calcium nitrate, calcium nitrate plus straw and sewage sludge) and two controls (bare fallow and cropped unfertilized) were taken on three occasions (before, during and after cropping). Phospholipid fatty acids (PLFAs) were extracted from all soil samples and analysed for C-12 and C-13 contents in individual PLFAs. Seasonal variation in total PLFAs was small except for the most SOC-rich treatment (sewage sludge). Weighted means of C-13 in PLFAs showed that the plots fertilized with calcium nitrate only had the largest C-13 values in PLFAs before (-20.24 parts per thousand) and after the vegetation period (-20.37 parts per thousand). However, during the vegetation period the values were much smaller (-21.85 parts per thousand). This coincided with a strong increase in the PLFA 18:26,9, indicating the use of old organic matter by fungi. Monounsaturated PLFAs indicative of Gram-negative bacteria were more frequent before and after the growing season. This observed rebound' effect of the C-13 PLFA values during the vegetation period indicates that seasonal turnover of the microbial biomass can be substantial.
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| 7. |
- Börjesson, Gunnar, et al.
(författare)
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Soil microbial community structure affected by 53 years of nitrogen fertilisation and different organic amendments
- 2012
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Ingår i: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 48, s. 245-257
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Tidskriftsartikel (refereegranskat)abstract
- The Ultuna long-term soil organic matter experiment in Sweden (59'82A degrees N, 17'65A degrees E) was started in 1956 to study the effects of different N fertilisers and organic amendments on soil properties. In this study, samples were taken from 11 of the treatments, including unfertilised bare fallow and cropped fallow, straw with and without N addition, green manure, peat, farmyard manure, sawdust, sewage sludge, calcium nitrate and ammonium sulphate, with n = 4 for each treatment. Samples were taken from topsoil (0-20 cm) and subsoil (27-40 cm depth) and analysed for concentrations of phospholipid fatty acids (PLFAs), organic C, total N and pH. The results showed that the subsoil samples reflected the total PLFA content of the topsoil, but not the microbial community structure. Total PLFA content was well correlated with total organic C and total N in both topsoil and subsoil. Total PLFA content in topsoil samples was highest in the sewage sludge treatment (89 A +/- 22 nmol PLFA g dw(-1)). This contradicts earlier findings on microbial biomass in this sewage sludge-treated soil, which indicated inhibition of microorganisms, probably by heavy metals added with sludge. A switch towards microbial growth and faster decomposition of organic matter occurred around 2000, coinciding with lowered heavy metal content in the sludge. According to the PLFA data, the microbial community in the sewage sludge treatment is now dominated by Gram-positive bacteria. A lack of Gram-negative bacteria was also observed for the ammonium sulphate treatment, obviously caused by a drop in pH to 4.2.
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| 8. |
- Ekblad, Alf, et al.
(författare)
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Determination of Soil Respiration rates and d13C in situ using a spectroscopic Picarro G1101-i instrument
- 2010
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Ingår i: Geophysical Research Abstracts. - 1607-7962. ; 12
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Konferensbidrag (refereegranskat)abstract
- Variation in the d13C-signature of soil respiration can be used as a tracer in ecological research. Up until now, isotopic determinations have mainly been performed by gas sampling and expensive and complex laboratory IRMS analyses. Recently, user friendly, portable and less expensive spectroscopic instruments have become available on the market. However, if these instruments give reliable data in dynamic systems under highly variable temperatures and air humidity conditions is unknown. In this talk we will present results from the first summer of tests of the use of a Picarro G1101-i cavity ringdown spectroscopy instrument (size 43 x 25 x 59 cm; 26.3 kg) to determine the d13C of soil respiration in various systems.
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| 9. |
- Ekblad, Alf, et al.
(författare)
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Production and turnover of ectomycorrhizal extramatrical mycelial biomass and necromass under elevated CO2 and nitrogen fertilization
- 2016
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Ingår i: New Phytologist. - Hoboken, USA : Wiley. - 0028-646X .- 1469-8137. ; 211:3, s. 874-885
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Tidskriftsartikel (refereegranskat)abstract
- Extramatrical mycelia (EMM) of ectomycorrhizal fungi are important in carbon (C) and nitrogen (N) cycling in forests, but poor knowledge about EMM biomass and necromass turnovers makes the quantification of their role problematic. We studied the impacts of elevated CO2 and N fertilization on EMM production and turnover in a Pinus taeda forest. EMM C was determined by the analysis of ergosterol (biomass), chitin (total bio- and necromass) and total organic C (TOC) of sand-filled mycelium in-growth bags. The production and turnover of EMM bio- and necromass and total C were estimated by modelling. N fertilization reduced the standing EMM biomass C to 57% and its production to 51% of the control (from 238 to 122 kg C ha-1 yr-1), whereas elevated CO2 had no detectable effects. Biomass turnover was high (~13 yr-1) and unchanged by the treatments. Necromass turnover was slow and was reduced from 1.5 yr-1 in the control to 0.65 yr-1 in the N-fertilized treatment. However, TOC data did not support an N effect on necromass turnover. An estimated EMM production ranging from 2.5 to 6% of net primary production stresses the importance of its inclusion in C models. A slow EMM necromass turnover indicates an importance in building up forest humus.
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| 10. |
- Hagenbo, Andreas, et al.
(författare)
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Ectomycorrhizal necromass turnover is one-third of biomass turnover in hemiboreal Pinus sylvestris forests
- 2024
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Ingår i: Plants, People, Planet. - : John Wiley & Sons. - 2572-2611.
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Tidskriftsartikel (refereegranskat)abstract
- Societal Impact Statement:Efficient mitigation of climate change requires predictive models of forest ecosystems as sinks for atmospheric carbon. Mycorrhizal fungi are drivers of soil carbon storage in boreal forests, yet they are typically excluded from ecosystem models, because of a lack of information about their growth and turnover. Closing this knowledge gap could help us better predict future responses to climate change and guide policy decisions for sustainable management of forest ecosystems. This study provides new estimates of the production and turnover of mycorrhizal mycelial biomass and necromass. This information can facilitate the integration of mycorrhizal fungi into new predictive models of boreal forest soils.Summary:In boreal forests, turnover of biomass and necromass of ectomycorrhizal extraradical mycelia (ERM) are important for mediating long-term carbon storage. However, ectomycorrhizal fungi are usually not considered in ecosystem models, because data for parameterization of ERM dynamics is lacking.Here, we estimated the production and turnover of ERM biomass and necromass across a hemiboreal Pinus sylvestris chronosequence aged 12 to 100 years. Biomass and necromass were quantified in sequentially harvested in-growth bags, and incubated in the soil for 1-24 month, and Bayesian calibration of mathematical models was applied to arrive at parametric estimates of ERM production and turnover rates of biomass and necromass.Steady states were predicted to be nearly reached after 160 and 390 growing season days, respectively, for biomass and necromass. The related turnover rates varied with 95% credible intervals of 1.7-6.5 and 0.3-2.5 times yr-1, with mode values of 2.9 and 0.9 times yr-1, corresponding to mean residence times of 62 and 205 growing season days.Our results highlight that turnover of necromass is one-third of biomass. This together with the variability in the estimates can be used to parameterize ecosystem models, to explicitly include ERM dynamics and its impact on mycorrhizal-derived soil carbon accumulation in boreal forests.
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