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Two sequential extractions with unbuffered 0.1 m BaCl2 were done to study the release of salt-exchangeable H+ and Al from mineral horizons of five Podzols and a Cambisol. Released Al was found to have a charge close to 3+ in all horizons and in both extractions. This finding was supported by the near-equality of the titrated exchangeable acidity (EAT) and the sum of exchangeable acids (EA = He + 3Ale, calculated from the pH and Al concentration of the extract). The ratio between EA of the second and the first extraction was over 0.50 in the Bs2 and C horizons and smaller in the other horizons. H+ was assumed to be in equilibrium with weak acid groups, and the modified Henderson–Hasselbach equation, pKHH = pH ? n log (α/(1 ? α)), was used to explain pH of the extract. The degree of dissociation (α) was calculated as the ratio between effective and potential cation exchange capacity. Value of the empirical constant n was found to be near unity in most horizons. When the monoprotic acid dissociation was assumed in all horizons, pKHH had the same value in both extractions. For Al3+, two equilibrium models were evaluated, describing (i) complexation reactions of Al3+ with soil organic matter, and (ii) equilibrium with Al(OH)3. Apparent equilibrium constants were written as (i) pKo = xpH ? pAl3+, and (ii) log Qgibbs= log Al3+ ? 3log H+. The two extractions gave an average reaction stoichiometry x close to 2 in all horizons. Results suggest that an equilibrium with organic Al complexes can be used to express dissolved Al3+, aluminium being apparently bound to bidentate sites. The value of log Qgibbs was below the solubility of gibbsite (log Kgibbs = 8.04) in many horizons. In addition, log Qgibbs of the second extraction was greater than that of the first extraction in all horizons except the C horizon. This indicates that equilibrium with Al(OH)3 cannot explain dissolved Al3+ in the soils. We propose that the models of pKHH and pKo can be used to simulate exchangeable H+ and Al3+ in soil acidification models. 相似文献
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Christoph Wittmann Mika A. Kähkönen Hannu Ilvesniemi Mirja S. Salkinoja-Salonen 《Soil biology & biochemistry》2004,36(3):425-433
A novel approach allowing on-site high throughput enzyme activity measurements by fluorogenic model substrates was applied to study the functioning of enzymes involved in biochemical cycling of nutrients in boreal forest soil ecosystems. The examined enzymes comprised α-glucosidase, β-glucosidase, β-xylosidase, β-cellobiosidase, N-acetyl-glucosamidase, acetate-esterase, butyrate-esterase, phosphomonoesterase, sulphatase and aminopeptidase, whereby spatial and seasonal variation of their activity was investigated over nine seasons in 2 years. The studied sites of boreal podzolized soil of Pinus sylvestris and Picea abies forest were located in central Finland. Activity of all enzymes except sulphatase was highest in the humus layer in all seasons. Maximum sulphatase activity was located below the humus layer in the soil column. Annual activities of acetate-esterase, butyrate-esterase, β-glucosidase and phosphomonosterase calculated to in situ temperature during the year were 480-700, 690-950, 110-190 and 110-200 mol m−2 year−1, respectively. They were up to 100 fold higher than the other six measured activities. The overall turnover capacity of the enzymes was >1000 mol of ester linked carbon, >700 mols carbon from different carbohydrates, 100-200 mol of ester linked phosphate, 10-40 mol of ester linked sulphate m−2 year−1. Winter time (November-April) contributed from 7 to 32% to the annual turnover capacity indicating important enzyme activities also during a cold period of the year. Clear-cutting of the tree stand did not adversely affect enzyme activities related to the cycling of carbon, nitrogen, sulphur and phosphorus during the year. The pH optimum for hemicellulose and cellulose hydrolysing enzymes was pH 3-4 and the pH optimum of phosphomonoesterase, sulphatase, aminopeptidase and N-acetyl-glucosamidase was 4-5. This shows that the hydrolytic activities were adapted to the acid pH-values of the soils. The soil hydrolytic potential was many fold higher as compared to the actual amount of litter it received in the P. sylvestris and P. abies forests. 相似文献
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Kaisu Leppänen Peter Spetz Andrey Pranovich Kari Hartonen Veikko Kitunen Hannu Ilvesniemi 《Wood Science and Technology》2011,45(2):223-236
Norway spruce saw meal was extracted with pressurized hot water at 120–240°C using a flow-through system. Only small amounts
of hemicelluloses were extracted at 120–160°C, but dissolution was significantly enhanced when higher extraction temperatures
were applied. All hemicelluloses but only 15% of lignin were removed from wood at 220°C, and even less lignin was extracted
at lower temperatures. Partial degradation of cellulose seemed to take place only at 240°C. Of the total amount of extracted
hemicelluloses, 4–22% was hydrolyzed to monosaccharides. Although the average molar masses of extracted hemicelluloses decreased
with increasing extraction temperature, even at 240°C the extracted carbohydrates occurred, on average, as polysaccharides.
Polysaccharides with an average molar mass of 31 kDa were obtained at 170°C. The molecular-mass characteristics and yield
of carbohydrates depend on the extraction temperature, which should be chosen based on the end use of the isolated hemicelluloses. 相似文献
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Markus Hartman Tanja Oksala Hannu Ilvesniemi 《Scandinavian Journal of Forest Research》2019,34(4):282-288
We studied the soil carbon dioxide respiration (Rs) at three clear-cut mesic forest sites in south, central and north central Finland, which had been treated with different intensities of stump lifting and slash removal and then patch mounded and planted with spruce. The follow-up period after the initial calibration lasted for five consecutive years. Throughout the study the Rs remained at fairly steady levels according to the study site and soil disturbance level. Based on a split-plot test using the general linear model there were no significant differences in the Rs between the different stump and slash removal treatments at the three study sites, but unaffected and moderately affected soil surfaces had significantly higher Rs than mounds and wheel ruts. We conclude that the removal of stumps and slash have minor direct effects on Rs, but large indirect effects through soil disturbance. 相似文献
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Nissinen A. Kareinen T. Tanskanen N. Ilvesniemi H. 《Water, air, and soil pollution》2000,119(1-4):23-43
Apparent cation–exchange equilibria and solubility of aluminium were analysed in two acidic forest soils: a Cambisol and a Cambic Podzol. Soil solution was obtained by a centrifuge drainage method from fresh soil samples and with suction lysimeters. The total positive charge of the measured cations as well as the concentrations of the cations were generally much larger in the centrifugates than in the lysimeter solutions, which implies that total charge of soil solution is larger in small pores than in large pores. Hydrogen ion in particular was concentrated in some of the centrifugates, the ratio centrifugate:lysimeter solution being over 10. The total positive charge of the measured cationsdecreased with increasing depth with both methods. Theapparent cation–exchange coefficients K H-Ca, K Al-Ca, and K K-Ca had different values in the methods, and the variation in the cation exchange coefficients was larger in the lysimeter method than in the centrifuging method. The coefficient K Mg-Ca had similar values in both methods. The results imply that mobile solution could not have cation–exchange equilibria with bulk exchangeable cations in the soils, although solution in small pores seemed to have equilibria. Solubility of Al did not follow the solubility of an Al(OH)3 phase in the centrifugates, and the centrifugates with a H+ activity larger than 60 μmol were undersaturated with respect to the gibbsite. Solubility of Al was between gibbsite and amorphousAl(OH)3 in the lysimeter solutions. Differencesbetween the centrifugates and the lysimeter solutionsin the ion concentrations and in the apparent chemicalequilibria were similar for both soils studied. 相似文献
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Soil temperature is proposed to affect the photosynthetic rate and carbon allocation in boreal trees through sink limitation. The aim of this study was to investigate the effect of temperature on CO(2) exchange, biomass partitioning and ectomycorrhizal (ECM) fungi of boreal tree species. We measured carbon allocation, above- and below-ground CO(2) exchange and the species composition of associated ECM fungi in the rhizosphere of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies K.) and silver birch (Betula pendula Roth) seedlings grown in soil maintained at 7-12, 12-15 and 16-22 °C. We found increased root biomass and photosynthetic rate at higher soil temperatures, but simultaneously with photosynthesis rate, higher temperature generally increased soil respiration as well as shoot, and root and rhizosphere respiration. The net CO(2) exchange and seedling biomass did not increase significantly with increasing temperature due to a concomitant increase in carbon assimilation and respiration rates. The 2-month-long growth period in different soil temperatures did not alter the ECM fungi species composition and the below-ground carbon sink strength did not seem to be directly related to ECM biomass and species composition in any of the tree species. Ectomycorrhizal species composition and number of mycorrhiza did not explain the CO(2) exchange results at different temperatures. 相似文献
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de Chantal Michelle Leinonen Kari Ilvesniemi Hannu Westman Carl Johan 《New Forests》2004,27(2):159-173
The aims of the study are to find out the effects of site preparation on soil properties and on the morphology of three-year-old Pinus sylvestris L. and Picea abies (L.) Karst. seedlings sown at different dates along a slope with variation in soil texture, water, and fertility. Based on the hypothesis that soil texture affects soil water content, water retention capacity, and nutrient content, we studied site preparation of varying intensities: exposed C horizon, mounds (broken O/E/B horizons piled over undisturbed ground), and exposed E/B horizon. Though the growing time difference between sowings was about one month, after three growing seasons, spring-sown seedlings were larger than summer-sown seedlings. P. sylvestris seedlings were largest with mounds and smallest with exposed C horizon, but site preparation did not affect the morphology of P. abies seedlings. 相似文献
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The Gaines–Thomas selectivity coefficient, K, was used to express the relation between the cations in solution and the cations in exchange sites in podzolic forest soils. Soil solution was obtained by centrifuging a fresh bulked soil sample. Exchangeable cations HX, AlX, CaX, MgX and KX and effective cation-exchange capacity, CECe, were determined with 0.1 m BaCl2. Apparent values of K indicated a preference of Ca2+ over Mg2+ and over Al3+ in O, A and B horizons (log KAl–Ca < 0 and log KMg–Ca < 0), whereas log KK–Ca and log KH–Ca exceeded zero. The horizons were similar with respect to log KH–Ca, and the differences in log KMg–Ca were small. Log KK–Ca and log KAl–Ca increased in the horizons in the order O < A < B. Log KAl–Ca was not significantly correlated with the fraction AlX/CECe. Log KMg–Ca was positively correlated with the fractions HX/CECe and AlX/CECe, and negatively correlated with log (CaX/MgX). The selectivity coefficient of binary cation exchange seemed to be applicable to in situ soil solutions. However, the fraction of each cation on exchange sites should be based on the CECe rather than on the sum of the two cations. The latter, also, seemed to be acceptable in cases of exchangeable cations with a large relative content in soil, e.g. in Al3+–Ca2+ exchange in A and B horizons, and in H+–Ca2+ exchange in O and A horizons. 相似文献