| 1. |
- Fransson, Ann-Mari, et al.
(författare)
-
Aluminum complexation suppresses citrate uptake by acid forest soil microorganisms
- 2004
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier. - 0038-0717 .- 1879-3428. ; 36:2, s. 353-357
-
Tidskriftsartikel (refereegranskat)abstract
- Organo-mineral interactions have been hypothesized to play a major role in biogeochemical cycling and pedogenesis in some forest soils. These processes are likely to be controlled to some extent by their persistence in soil, however, the factors regulating their bioavailability remain poorly understood. Therefore, we investigated the microbial utilization of 14C-labeled citrate in glass bead filled bioreactors containing a biofilm developed from an inoculum from an acid forest soil. The removal of Al-citrate in the bioreactors was negligible compared to the rate of citrate removal in the absence of Al. There was no evidence that in the short-term the microbial community adapted to increase the utilization of Al-citrate. In bioreactors filled with a Picea abies forest soil (Haplic Arenosol) the rates of citrate utilization were always slightly higher than that of Al-citrate. We conclude that complexation of citrate by metals such as Al may have a significant effect on their role in soil biogeochemical cycles.
|
|
| 2. |
- Fransson, Ann-Mari
(författare)
-
Evaluation of oxalate/oxalic acid for extracting plant available phosphorus in unfertilized acid soils
- 2001
-
Ingår i: Communications in Soil Science and Plant Analysis. - 0010-3624. ; 32:15-16, s. 2469-2484
-
Tidskriftsartikel (refereegranskat)abstract
- The extractability of phosphorus (P) was studied in an acid, unfertilized soil at an abandoned farm and in 40 different soils from former agricultural fields and pastures. Oxalate/Oxalic acid extraction was compared with a number of other methods in order to evaluate the suitability of oxalate/oxalic acid as a method for extracting P from soil. The extracting efficiency and a rough estimate of the origin of the extracted P was also investigated. Total and molybdate reactive P extracted with weak (I mM), acid (9.35 mM, pH 2.3). and strong (50 mM) oxalate correlated well with Na2SO4 + NaF, Olsen P, and Bray I extractable P (0.96 > r > 0.77). Total and molybdate reactive P fractions determined by different oxalate methods were also closely correlated (0.99 > r > 0.84). Only total organic P did not correlate with the other P fractions extracted. However. the large strong oxal extractable P fraction was correlated to many of the weaker extractable fractions. A large share of this fraction is probably organic. The Na2SO4 + NaF extraction, Olsen P, and Bray 1 were also closely correlated. The more loosely adsorbed fractions are possibly replenished to some extent when the soluble phosphate is consumed by plant uptake. A large share of total P extracted with acid (9.35 mM) and strong (50 mM) oxal was organic. The molybdate reactive fraction, however, was fairly constant up to 9.35 mM oxalate in the solution, neither depending on solution concentration nor on pH. Total P extracted with oxalate was related to the logarithm of the extractant concentration. The advantage of the oxal method is that the pH can be adjusted to fit a desired soil pH. and both extractant concentration and analytical method could be chosen to determine either loosely bound P or a substantial amount of total P that might be potentially available.
|
|
| 3. |
- Fransson, Ann-Mari, et al.
(författare)
-
Phosphorus fertilisation causes durable enhancement of phosphorus concentrations in forest soil
- 2000
-
Ingår i: Forest Ecology and Management. - 1872-7042. ; 130:1-3, s. 69-76
-
Tidskriftsartikel (refereegranskat)abstract
- The duration of P fertiliser in acid forest soil was investigated in a Norway spruce (Picea abies Karst.) forest in southcentral Sweden. The fertilisation of the soil started in 1967, but no P has been applied since 1988. The N fertilisation is still continuing. Totally, 300 kg P per hectare, as superphosphate, and/or 1090 kg N per hectare, as ammonium nitrate, was applied. Concentrations of both 0.05M Na2SO4 + 0.02M NaF extractable P and 0.5M H2SO4 extractable P in the Of, Oh, E and top B horizons of fertilised soils were elevated compared to the control. The P fractions considered to be extracted are adsorbed and some Al-bound phosphate, in the case of Na2SO4 + NaF, and Ca phosphates, in the case of H2SO4. 3-4% of the added P was recovered as Na2SO4 + NaF extractable P, and 10-22% was recovered as H2SO4 extractable P in the soil profile down through the first 5 cm of the B horizon. Still continuing ammonium nitrate fertilisation has decreased the H2SO4 extractable P concentration in this soil. Cumulative P fertiliser application of 300 kg P per hectare has counteracted this decrease. (C) 2000 Elsevier Science B.V. All rights reserved.
|
|
| 4. |
- Fransson, Ann-Mari, et al.
(författare)
-
Plantago lanceolata L. and Rumex acetosella L. differ in their utilisation of soil phosphorus fractions
- 2003
-
Ingår i: Plant and Soil. - 0032-079X. ; 248:1-2, s. 285-295
-
Tidskriftsartikel (refereegranskat)abstract
- To establish relationships between soil phosphorus (P) fractions and leaf P, a mycorrhizal species (Plantago lanceolata L.) was compared with a typically non-mycorrhizal species (Rumex acetosella L.) in a glasshouse experiment. The plants were grown in 40 soils from non-fertilised, abandoned pastures or abandoned arable fields and leaf P concentration were found to be related to various soil P fractions after six weeks of growth. The differences in the P fractions in soil can account for a large share of the variation in leaf P concentration in both species, but the two species differed in their utilisation of P fractions. Leaf P concentration of R. acetosella was more related to extractable soil P than that of P. lanceolata. Rumex acetosella showed a higher maximum P concentration. The P fractions accounting for the largest share of the variation in leaf P concentration was the Bray 1 extractable and the weak oxalate (1 mM) extractable P, and for P. lanceolata also the Na2SO4+NaF extractable P fraction. P extracted with these methods accounted for up to 80% of the variation in P concentration in leaves of R. acetosella and 65% of the variation in leaves of P. lanceolata. More P extractable with weak oxalate, Na2SO4+NaF and strong oxalate (50 mM) was released from the soil than was taken up by the plants during the experimental period. The Bray 1 extractable P fraction, however, decreased in both unplanted and planted soils. Phosphatase release was not induced in any of the plants during the experimental period, indicating that they were not mobilising soil organic P. However, some of the methods extracted a large share of the organic P and still explained much of the variation in leaf P concentration. Mycorrhizal colonisation of P. lanceolata was inversely related to the extractable soil P. The consistently fast P uptake of R. acetosella indicates that this species have a high demand for P. The differences in P utilisation between R. acetosella and P. lanceolata could be caused by their different mycorrhizal status.
|
|
| 5. |
- Fransson, Ann-Mari
(författare)
-
Soluble and Plant Available Phosphorus in Acid Soils
- 2000
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The P availability and solubility differ between soils and plants seem to have different ways of utilising the P present. The many P fractions present in soil interact and are closely related to another and transformations may easily occur. Due to this more P than the soluble fraction is available to plants. Different plant species utilise the P in soil differently; the relationship between the plant P concentration and the P content of the soil differs among species. More knowledge about plant responses to low P concentrations in soil, and on the replenishment rate of the soluble P pool is needed. Different processes and reactions might also be activated as P status changes, or if the major P pool changes. However, little is known in this field of research. To determine P solubility in a particular soil, P sorption, pH, P content, distribution of P, and organic matter composition need to be investigated. Another consequence of the close relationship between the P fractions in the soil is that added P is distributed over the soil P fractions and increases the soils overall P status including the most easily available P fractions. The effect of a P fertilisation can be detected long after fertilisation has ceased as increased easily extractable P determined with methods that is considered available to plants. In contrast addition of compounds that increase one particular P fraction of the soil, for example Ca, decreases the soluble P pool in the soil. If this build-up of Ca-phosphates decreases the potentially available fraction is however not certain, this depends on if the fraction formed is in equilibrium with the directly available, more soluble P.
|
|
| 6. |
- Fransson, Ann-Mari, et al.
(författare)
-
The wood-decaying fungus Hygrophoropsis aurantiaca increases P availability in acid forest humus soil, while N addition hampers this effect
- 2004
-
Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 36:11, s. 1699-1705
-
Tidskriftsartikel (refereegranskat)abstract
- We evaluated the influence of the brown rot fungus Hygrophoropsis aurantiaca on P solubility in the humus layer of a podzolic forest soil. This fungus is known to exude large amounts of oxalic acid that may stimulate weathering of minerals and increase dissolution of humus, which in turn may increase P availability in the soil surrounding the fungus. Humus was inoculated using small wooden pieces colonised by the fungus. The presence of the fungus resulted in elevated concentration of PO4- in the humus solution. In a second experiment birch 4 seedlings grown in the same humus were able to utilise the PO4- mobilised by the fungus to increase their internal P content. The factor 4 determining this increased P uptake and the increased available P might be oxalate produced by fungus. The acid may directly dissolve P or change organic forms of P making it more susceptible to reaction with phosphatases. This fungal effect on P solubility diminished when N was added to the soil in the form of a slow release N fertilizer (methyl urea), or when a soil with a higher soil N concentration was used. We found a strong correlation between NH4+ concentration and total organic carbon in the soil solution at high NH4+ concentrations, suggesting the dissolution of humus as a result of the high NH4+ content in the solution. This study demonstrates that the wood-decaying fungus H. aurantiaca influences nutrient turnover in forest soil, and thereby nutrient uptake by forest trees. An intensified harvest of forest products such as whole tree harvesting may decrease the active biomass of the wood decomposers and may thereby change the availability of P and the leaching of N.
|
|
| 7. |
- Mahmood, Shahid, et al.
(författare)
-
Effects of hardened wood ash on microbial activity, plant growth and nutrient uptake by ectomycorrhizal spruce seedlings
- 2003
-
Ingår i: FEMS Microbiology Ecology. - 1574-6941. ; 43:1, s. 121-131
-
Tidskriftsartikel (refereegranskat)abstract
- Plant growth, nutrient uptake, microbial biomass and activity were studied in pot systems containing spruce seedlings colonised with different ectomycorrhizal fungi from an ash-fertilised forest. The seedling root systems were enclosed in mesh bags inside an outer compartment containing crushed, hardened wood ash. Three different species of mycorrhizal fungi and a non-mycorrhizal control were exposed to factorial combinations of ash and N addition. Ash treatment had a highly significant, positive effect on plant growth and on shoot and root concentrations of K, Ca and P, irrespective of mycorrhizal status. Mycorrhizal inoculation had a significant effect on plant growth, which was proportionally greater in the absence of ash. N addition had a significant positive effect on plant biomass in mycorrhizal treatments with ash, but no effect in non-mycorrhizal treatments or most of the mycorrhizal treatments without ash. Piloderma sp. 1, which was earlier found to colonise wood ash granules in field studies, appeared to accumulate Ca from ash in the mycorrhizal roots. 5-6.7% of the total P in the ash was solubilised, with 0.9-1.5% in solution, 3.6-4.6% in the plants and 0.5-1.5% in microbial biomass. Bacterial activity as determined by [H-3]-thymidine and [C-14]-leucine incorporation was significantly greater in ash treatments than in controls with no ash addition. Principal component analysis (PCA) of phospholipid fatty acids (PLFAs) showed a clear difference in bacterial community structure between samples collected from ash-treated pots and controls without ash. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
|
|
