Soil Development in the Nordic Countries - Identification and Quantification of Factors and Processes, and Prerequisites for Biological Primary Production

2 SLU-5K0MA

Soil development in the Nordic countries - Identification and quantification of factors and processes, and prerequisites for biological primary production.

Extended abstracts from a Nordic workshop 6-9 September 1994, Asa, Sweden.

Editor: Mats Olsson

OSTfiWDON OF TW DOCUMENT IS UNLIMITED

Rapporter i skogsekologi och skoglig marklara Rapport 71 Reports in Forest Ecology and Forest Soils Report 71 Uppsala 1996 Institutionen for skoglig marklara Department of Forest Soils ISSN 0348-3398 Swedish University of Agricultural Sciences ISRN SLU-SKOMA-R—71 —SE PREFACE

This report is a compilation of abstracts from research presentations during a Nordic workshop at Asa in Sweden September 6 - 9th 1994. The main goal with the workshop was to give insight in ongoing pedological research in Denmark Finland, Norway and Sweden. Further aims were to form a basis for co-ordinated research that takes advantage of the amplitude in soils and climate, and scientific competence in the Nordic countries. The intention was also to initiate a Nordic soil data-bank to be used in research and teaching.

Focus was placed on podzolised soils. These are the predominating soils in the

DISCLAJ

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Soil carbon storage in a gradient of Swedish forest soils. 1 A Alriksson and M. T. Olsson

Do some forest ecosystems have a maximum 2 limit for litter decomposition? A synthesis of data. B. Berg and M-B. Johansson

Forest productivity on podzols along a south-north 3 gradient in Norway. J. Frank

Accumulation of imogolite-type materials in the 6 Spodic B horizons of northern Scandinavia. J. P. Gustafsson, P. Bhattacharya, D.C. Bain, A R. Fraser and W.J. McHardy

Effect of paludification on the chemical properties 8 of forest soils in eastern Finland. K. Kotoaro and H. Mannerkoski

Amount of organic carbon, horizon thicknesses and 13 trees - heterogeneity of podzolized soil within a forest stand. J. Liski

Use of the aluminium species composition in soil. 15 solution as an indicator of acidification U.S. Lunds from and R. Giesler

Factors affecting the SOM/DOC relation in a humic podzol. 16 T. Magnusson andU. Skyllberg

Clay mineralogy of Swedish podzol profiles. 19 P-A Melkerud

Effect of tree species and soil properties on nutrient 24 immobilization in the forest floor. K. Raulund-Rasmussen and H. Vejre

Podzolization in Finland. 26 M. Starr and Pekka Tamminen

Pedogenic evaluation of some sandy, weakly podzolized 27 soil in Amli, southern Norway. L. Tau Strand Accumulation of C, N and Pin the forest floor: 1. Effects 30 of thinning and soil properties. L Vester dal and Karsten Rauland-Rasmussen

Water holding capacity and water balance in 32 podzolised forest soil. CJ Westman SOIL CARBON STORAGE IN A GRADIENT OF SWEDISH FOREST SOILS by A. Alriksson and M.T. Olsson Department of Forest Soils, Swede ish Universityof Agricultural Sciences P.O. Box 7001, S-750 07Uppsala, Sweden

Data on organic carbon was collected in a project concerning organic matter influence on weathering rates at the Dep. of Forest Soils. The 18 sites were chosen to represent a gradient of site geochemistry from northern to southern Sweden. The amount of carbon stored in the soil horizons to 1 m depth reflects influence from biomass production capacity and also site history. In southern Sweden most of the present forest soils once have been cultivated and many soil profiles show influence of antropogenic disturbance (Alriksson, A. and Olsson M.T. 1994, in prep). Temperature sum largely reflects a north-south gradient of Sweden and amounts of organic carbon to 1 m depth correlated well to temperature sum (R.2= 0.64). The amount of carbon stored in the soil to 1 m depth ranged between 40 and 110 tonnes ha'l with the highest amounts in southern Sweden. There is a strong correlation (R2= 0.63) between site productivity according to Landmark and Hagglund (1982) and the amount of organic carbon to 1 m dept. In southern Sweden a larger part of the carbon was present in the O plus A horizon compared to northern Sweden. The presence of a carbon rich A-horizon reflects pedo- turbation due to agricultural activities which historically predominated in southern Sweden.

References Alriksson A. and Olsson, M.T. 1994. Soil carbon storage in a gradient of Swedish forest soils.

(in prep). Hagglund, B. and Landmark, J-E 1982. Handledning i bonitering med skogshogskolans boniteringssystem, del 1-3. Nat. Board of Forestry, Jonkoping, Sweden (in Swedish).

1 DO SOME FOREST ECOSYSTEMS HAVAE A MAXIMUM LIMIT FOR LITTER DECOMPOSITION? A SYNTHESIS OF DATA

Berg, B. and Johansson, M-B.

Department of Forest Soils, P.0. Box 7001, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden.

Long-term litter decomposition data were used to estimate final decompostion levels using an asymptotic function. The estimated final limit values for decomposition were compared with available chemical data for the different litter types.

A total of 41 limit values were estimated from as many different decompsition studies, with 20 different litter types incubated in eight different forest ecosystems. The limit values estimated varied with litter type. They ranged from about 35 percent decomposition to about 100 percent and were linearly related to the initial litter concentrations of N, M and Ca in the newly shed litter. For these three nutrients there are causal relationships to lignin degradation on the level of fungal physiology and to the lignin-degrading microbial community. Using all available data we made simple and multiple linear regressions and obtained a negative linear relationship between limit value and initial N concentration (R2adj=0.429;n=41 ;p<0.001). For needle litter alone we obtained a better relationship (R2adj=0.538;n=23;p<0.001). Manganese concentrations in litter gave a positive relationship (R2adj=0.399;n=25;p<0.001) , with a clear improvement when needle litter was tested for alone (R2atg=0.517;n=18;p<0.001). Calcium alone gave a barely significant relationship. When combining nutrients in multiple linear relationships we obtained high R2 values, indicating that the models were good. Thus for all sites and litter types N, Mn and Ca combined gave and R2ad ; value of 0.809 with n=25 (pcO.001). All needle litters combined gave and R adj of 0.873 (n=16;p<0.001).

We concider the use of this finding to be a valuable tool for estimating humus layer buildup and thus forestry practice, as well as a tool for environmental purposes.

2 FOREST PRODUCTIVITY ON PODZOLS ALONG A SOUTH-NORTH GRADIENT IN NORWAY

Jon Frank

Agricultural University of Norway, Department of Forest Sciences P.O. Box 5044, N-1432 As, Norway. E-mail: [email protected]

Key words: Needle analyses, Norway spruce, podzol, regression model, site index, soil properties.

Extended abstract

The productivity of the boreal spruce forests is a function of a great number of soil and climatic factors. An important aim of the soil-site research has been to develop methods for estimating site index (SI) in forest areas where trees are absent or where they are unsuitable for direct site index measurements, or on bare land suitable for afforestation. The main objectives of this study have been to identify relationships between site index of Norway spruce (Picea abies) and soil, topographic and climatic variables. The results will probably represent a quantitative expression of features related to site quality. The forest and soil of 23 permanent experimental plots (est 1930-79) in pure, even-aged stands (mean age 50 years) of Norway spruce {Picea abies) have been examined along a south-north gradient (1010 km). Needle samples have been collected from the seventh whorl of branches in October November (5 trees/plot). The soil analyses were mainly based on randomly distributed sample points where each horizon was sampled separately (10 to 20 subsamples, 3 replicates). The dominating plant community in the permanent plots is Eu-Piceetum dryopteridetosum, and the soils have been classified into Humo-Ferric or Ferro-Humic Podzol (18 plots), Humic

3 Gleysol (3 plots) and Dystric Brunisol (2 plots) according to the Canadian system. The climatic conditions and the atmospheric depositions are quite different within the very wide study area (Frank et al. 1995). The general pollution pattern shows that the amounts of strong acids, sulphate and nitrogen in the precipitation decrease significantly from south to north, while the pH increases from 4.3-5.1 (Norwegian State Pollution Control Authority 1993). The site index (top height at reference age 40 years at breast height, Tveite 1977) ranged from high (25.1 m) to medium (13.9 m), and decreases from south to north on the podzolic soils studied (R2=0.48). The nutrient status of the trees was sufficient for most elements, and a grouping of the plots into high (SI > 20 m) or medium site index class (SI < 20 m) led to significantly higher element values for calcium, copper, magnesium, nitrogen and sulphur in current needles from the high compared with the medium site class, but significantly lower value for boron (Frank et al. 1995). The nitrogen capital in the soil root zone is also significantly higher on the plots grouped into the high site class. Significant negative correlations exist between site index and the amount of iron in the upper part of the podzolic B-horizons (Figure 1).

Pyrophosphate - exiractahte Fa (%) Dithionite-titrate extractable Fa (%)

Figure 1. Relationships between site index of Norway spruce and pyrophosphate and dithionite-citrate extractable Fe, respectively, accumu lated in the upper part of the podzolic B horizon.

4 The accumulation of Fe compounds in these horizons increases to some extent from south to north for the podzolic soils studied. A highly signifi cant (R2=0.87) seven parameter regression model expressing site index as a function of pentatherm, precipitation in May + June and July + August, exchangeable acidity, available phosphorus, total nitrogen and organic carbon in the root zone has been found using a stepwise multiple regression procedure (Frank et al. 1995). A less precise (R2=0.67) model for field application expressing site index as a function of pentatherm, slope steep ness and precipitation in May + June has also been developed. For both models the residuals are randomly distributed around the zero line. The results indicate that the climatic conditions are the main limiting factor, and the soil properties have a minor effect on the forest productivity of the podzolic soils studied.

References

Frank, J., R. Brean, P.H. Nygaard & O.J. Kjpnaas, 1995. The importance of soil properties for forest growth. In: Stuanes, A.O. & S. Woxholtt (eds.). Final report from the research programme Forest and Environment - Growth and Vigor. Communications of the Norwe gian Forest Research Institute (in press). Norwegian State Pollution Control Authority, 1993. Overv&king av lang- transportert forurenset luft og nedbpr. [Monitoring of long-range transported polluted air and precipitation.] Annual report 1992. Report 533/93. Oslo, 296 pp. Tveite, B., 1977. Site-index curves for Norway spruce (Picea abies (L.) Karst). Communications of the Norwegian Forest Research Institute 33: 1-84.

5 ACCUMULATION OF IMOGOLITE-TYPE MATERIALS IN THE SPODIC B HORIZONS OF NORTHERN SCANDINAVIA

J.P. Gustafsson1, P. Bhattacharya*, D C. Bainb , A.R. Fraserb and WJ. McHardy b

“Division of Land and Water Resources, Royal Inst of Technology, S-100 44 STOCKHOLM, Sweden hMacaulay Land Use Research Institute, Craigiebuckler, ABERDEEN AB9 2QJ, UK

Studies in Scotland and in North America have shown that imogolite-type materials (ITM) accumulate in spodic B horizons low in organic C. The genesis of ITM is subject to fierce debate; at least three different hypotheses have been presented to explain their occurrence. Due to a high point-of zero charge and to a high specific surface area, ITM are important adsorbents for inorganic solutes and organic acids. Before our and Strand ’s study (this issue) there were no reports on the occurrence of ITM in Scandinavian Spodosols. We chose to investigate whether ITM are present in northern Scandinavia. For this purpose, B horizons were sampled from 33 typical podzolic profiles across northern Scandinavia (13 in Sweden, 16 in Finland and 4 in Norway).

Selective dissolution revealed a highly significant relationship between extractable inorganic A1 (Al0-Alp) and Si (Si,,) (Figure). The slope indicated an Al:Si ratio somewhat higher than 2, which is expected for ITM. These data, although not entirely conclusive, suggested that ITM comprised the bulk of the surface-reactive inorganic A1 in the soils. For three Bs2 horizons, this information was complemented with IR spectroscopic analyses and transmission electron microscopy (TEM)/ electron diffraction. TEM revealed that crystalline imogolite (Al2Si03(0H)4) was a common precipitate in the three samples. The IR spectra showed, however, that more amorphous proto-imogolite allophanes, rather than imogolite,

6 were the main constituent of the ITM. ITM totally dominated the acid-dispersable fine clay fraction, although small amounts of gibbsite and kaolinite were also found.

The genesis of ITM will largely remain a matter of speculation until more detailed studies focusing on both the soil solution and the solid phase are performed. Probably the migration of Al-organic complexes from upper horizons, their subsequent degradation in lower horizons, followed by the formation of proto-imogolite, is one (but perhaps not the only) important mechanism. This is because (i) soil solution studies from within the study region show that A1 primarily migrates as Al-organic complexes, and (ii) that the solid phase of the B horizon, in spite of this, often contained only small amounts of organically bound A1 as compared to inorganic Al. To some extent, carbonic acid weathering within the B horizon may also have led to the precipitation of ITM. The importance of this latter mechanism is impossible to assess with our data, but we hypothesize that it is less important as the soils were developed in tills with base-poor mineralogy.

> B1 horizons (Alo-Alp) = 2.60‘ Sio - 9.6 r2 = 0.974; n = 33

' B2 horizons (Alo-Alp) = 2.33*Sio +2.6 r2 = 0.982; n = 31

These results will be discussed in greater length in:

Gustafsson, J.P., Bhattacharya, P., Bain, D.C., Fraser, A.R. and McHardy, WJ. 1995. Podzolisationmechanisms and the synthesis of imogolite in soils of northern Scandinavia. Geoderma, under revision.

7 EFFECT OF PALUDIFICATION ON THE CHEMICAL PROPER TIES OF FOREST SOILS IN EASTERN FINLAND

Katri Kotoaro and Hannu Mannerkoski

University of Joensuu, Faculty of Forestry, P.O.Box 111, FIN-80101 JOENSUU, Finland

Podsolization is the most common soil formation process in Finland and on large areas in other Nordic countries. Paludification will affect certain characteristics on podsol profiles because of different decomposition conditions in the humus layer and wetness of the mineral soil.

In this study fourteen soil profile pairs have been compared (paludified/well-drained). Each pair has been described from a gently sloping terrain. At the lower end of the slope on weakly paludified area there were growing some Sphagnum-mosses and other mire plants without any real peat formation (humus layer <15 cm thick). The other sampling point was higher on the slope in well-drained conditions. Soil samples (100 cm3) were taken from every different profile layer from two opposite walls of the pit. Soil texture, bulk density and loss on ignition were deter mined from all samples. Different forms of Fe and A1 were separated using sodium pyrophosphate (pyr, 0.1 M Na4P207, pH 10), acid am- moniumoxalate (ox, 0.2 M (NH4)2(COO)2, pH 3), and sodium citrate-dithionate-bicarbonate (cdb, Na3C6 H5 07 - Na2S204 - NaHC03) extractions, each starting from a separate subsample. The fractions (organic , amorphous and crystalline) of Fe and A1 were calculated by subtraction. The results were calculated as percentages from dry mass.

8 In well-drained conditions there was less Fecdb in sorted soils than in till soils but in Al^ contents there were no clear difference. The reason could be minerological differences through sorting of soil material. In paludified conditions this difference cannot be seen in the iron contents, obviously because of the precipitation of iron into the B-horizon from subsurface flow water coming from higher lying areas, especially on sorted soils.

Under paludified conditions in B-horizon the proportion of crystallized iron (Fecd,-Fe

Although there were some differences between paludified and well-drained conditions in Fe and A1 fractions, the range of variation caused by variati on in soil forming factors and conditions was wide. It can be seen for instance in soil classification. By using the Canadian system, Bf horizons were more common on well-drained (57 %) than on paludified conditions (36 %). Bh or Bw horizons occured inversely. Much clearer difference would have been expected.

9 Table 1. The contents (% of dry mass) of iron and aluminium fractions in B horizon of well-drained and paludified till or sorted soils. Concerning iron also proportions (%) of other fractions from Fecdb are presented.

Ele- Frac- Till soils Sorted soils

ment tion Well- drained Paludified Well- drained Paludi fied

*) Content Prop. Content Prop. Content Prop. Content Prop.

Fe Org. 0.69 39 0.33 48 0.22 23 0.33 46

Fe Am. 0.34 19 0.08 12 0.48 51 0.35 49

Fe Cr. 0.74 42 0.28 41 0.25 26 0.04 5

A1 Pyr. 0.71 • • 0.46 • • 0.62 »• 0.87 • •

A1 Ox. 0.95 • • 0.85 • • 1.26 * • 1.18 • •

A1 Cbd. 0.98 • • 0.58 ** 0.62 • • 0.73 • •

*) Org. - organic; Am. - amorphous; Cr. - crystalline; Pyr. - sodium pyrophosphate-extractable; Ox. - acid amm.oxalate-extr.; Cbd. - sodium citrate-dithionate-bicarbonate-extr.

10 Table 1. The contents (% of dry mass) of iron and aluminium fractions in B horizon of well-drained and paludified till or sorted soils. Concerning iron also proportions (%) of other fractions from Fe^ are presented.

Ele- Frac- Till soils Sorted soils

ment tion Well- drained Paludified Well- drained Paludi fied

*) Content Prop. Content Prop. Content Prop. Content Prop.

Fe Org. 0.69 39 0.33 48 0.22 23 0.33 46 Fe Am. 0.34 19 0.08 12 0.48 51 0.35 49

Fe Cr. 0.74 42 0.28 41 0.25 26 0.04 5

A1 Pyr. 0.71 0.46 0.62 0.87 A1 Ox. 0.95 0.85 1.26 1.18

A1 Cbd. 0.98 • • 0.58 "" 0.62 • • 0.73 ••

*) Org. - organic; Am. - amorphous; Cr. - crystalline; Pyr. - sodium pyrophosphate-extractable; Ox. - acid amm.oxalate-extr. ; Cbd. - sodium citrate-dithionate-bicarbonate-extr.

ll Table 1. The contents (% of dry mass) of iron and aluminium fractions in B horizon of well-drained and paludified till or sorted soils. Concerning iron also proportions (%) of other fractions from Fecdb are presented.

Ele- Frac- Till soils Sorted soils

ment don Well- drained Paludified Well- drained Paludi fied

*) Content Prop. Content Prop. Content Prop. Content Prop.

Fe Org. 0.69 39 0.33 48 0.22 23 0.33 46 Fe Am. 0.34 19 0.08 12 0.48 51 0.35 49

Fe Cr. 0.74 42 0.28 41 0.25 26 0.04 5 A1 Pyr. 0.71 0.46 0.62 0.87

A1 Ox. 0.95 0.85 1.26 1.18

A1 Cbd. 0.98 • * 0.58 • ■ 0.62 • • 0.73 • *

*) Org. - organic; Am. - amorphous; Cr. - crystalline; Pyr. - sodium pyrophosphate-extractable; Ox. - acid amm.oxalate-extr. ; Cbd. - sodium citrate-dithionate-bicarbonate-extr.

12 AMOUNT OF ORGANIC CARBON, HORIZON THICKNESSES AND TREES - HETEROGENEITY OF PODZOLIZED SOIL WITHIN A FOREST STAND

Jari Liski

University of Helsinki, Department of Forest Ecology P.O. Box 24, FIN-00014 University of Helsinki, Finland

Soil properties, both physical and chemical, vary considerably even within distances of a few meters. In forests, besides the geological factors, trees are important causes for the variation. In addition to the importance for designing effective soil sampling, a thorough description of the variation can provide useful information on the processes that generate the variation.

For studying the variation in the amount of organic carbon (kg C/m2) in different soil layers and thicknesses of the soil horizons (F/H, E, B), a total of 99 soil cores (50 cm deep) were taken from a 4 x 8 m grid in a 130 years old Scots pine (Pinus sylvestris L.) stand on a glaciofluvial sand deposit in southern Finland. One 4 x 4 m half of the grid was placed under tree canopies and the other in a small within-stand opening. In order to study the effect of trees in more detail, 27 additional cores were taken around three trees. The horizon thicknesses were measured on the cores. Then, the cores were divided into the organic F/H and 0-10 cm (E and top of B horizon), 10-20 cm (middle layer of B horizon) and 20-40 cm (bottom of B horizon and top of C layer) mineral soil layers for analyzing the amount of carbon.

The amount of carbon varied 4-8 fold within the soil layers and the coefficients of variation ranged from 21 % to 41 %. Calculated on the basis of the observed standard deviations, 8-9 samples result in a mean estimate that differs less than 0.5 kg/m 2 from the true mean by the probability of 95% both in the F/H and 0-40 cm layers. Sample numbers in excess of 10 do not

13 substantially increase the accuracy of estimating the mean. On the basis of semivariograms, the carbon amounts were spatially dependent at the distances of less than 1-4 m and the spatial dependence accounted for 43-86 % of the total variance, depending on the soil layer. Therefore, to fulfill the criteria of the statistical independence, samples should be taken further from each other than that range of spatial dependence. Conversely, to utilize the dependence when interpolating (kriging), samples should be taken closer than the range.

The F/H horizon was 15 % thicker and contained 33 % more carbon in the canopy half than in the opening. These differences, due to changes in litter deposition and decomposition rates, had developed over a period of some tens of years which was, on the basis of the stumps, the age of the opening. In the 0-10 cm layer the amount of carbon was patchy and not associated with the trees. On the other hand, the 10-20 cm and 20-40 cm layers contained more carbon near the trees than elsewhere and the largest quantities were found in the immediate vicinities of the stems. The spatial patterning of the E horizon thickness was similar. The exceptionally thick E horizon near the stems was most probably caused by stemflow and the large amount of carbon in the B horizon below was, in turn, due to the organic compounds transported into soil by the stemflow. Owing to the podzolic properties, the organic compounds may have remained dissolved in water in the conditions of the E horizon and precipitated first in the B horizon. It seems, that even if the volume of stemflow is not more than 1-2% of precipitation in Scots pine stands, it still induces remarkable variation in soil properties. This is most probably due to concentrated routes of stemflow into the soil and high carbon concentration in the stemflow. According to these results, trees induce heterogeneity in soil properties and clearly observable alterations may develop fairly quickly considering the time scale of soil formation, namely in less than hundred years.

14 U se of the aluminium species composition in soil solution as an INDICATOR OF ACIDIFICATION.

U. S. Lundstrom and R. Giesier

Department of Forest Ecology, Swedish University of Agricultural Sciences, 901 83

Umea, Sweden.

Abstract, Soil solution chemistry was investigated for 3-4 years at two Swedish sites, i.e.

Svartberget (N Sweden) and Gardsjon (SW Sweden) with different acid loads and also at

Tisa in the north of the Czech Republic. At Svartberget the aluminium concentrations were highest in the eluvial horizon (30 uM) and 75% of the aluminium was organically bound. The concentrations of aluminium were low below the illuvial horizon. At

Gardsjon. the concentration of inorganic aluminium was high in the the illuvial horizon

(60 uM) and constituted 80%, but decreased with depth. At Tisa. inorganic aluminium in high concentrations (1000 uM) leached throughout the whole profile. When the process of podzolization is occurring,, organic acids form complexes with aluminium, whereby the weathering rate is enhanced and the eluvial horizon forms. In the illuvial horizon aluminium and iron are immobilized. Once inorganic aluminium leaching to the extent that it constitutes the largest proportion of the aluminium species, the process of podzolization is perturbed. The equilibria of AP"r with solid phases were evaluated, of which none of the tested phases seemed possible. It was concluded that the concentration

and distribution of aluminium species, sulfate and pH in a soil solution profile indicate the

degree of acidification and should be used in monitoring. Free drainage centrifugation and

aluminium speciation were found to be useful tools.

15 FACTORS AFFECTING THE SOM/DOC RELATION IN A HUMIC PODZOL

TORD MAGNUSSON and ULF SKYLLBERG

Swedish University of Agricultural Sciences, Department of Forest Ecology, Soil Science Section, 90183 Umea, Sweden.

The incorporation of organic matter in the soil (SOM) and its subsequent turnover rate, determines soil developement and soil properties. SOM may be consumed, accumulated, or lost from the soil column by leaching. The site hydrology, the chemical environment and the properties of SOM affects its mobilization and translocation. The fate of SOM is of consequence not only for the vegetation-soil ecosystem itself, but also for the aquatic ecosystems, where DOC greatly affects water quality. We have investigated the relation between SOM and soil solution DOC in different horizons of a humic podzol (Swedish soil class, terminology; Tamm, 1931). The aim was to explain the solubility relation between SOM and DOC, as a function of the cation species neutralizing the negative charge of organic matter functional groups. Effects of counter ions (H+, Na+, Ca2+, Al3+) on the solubility of SOM, were compared at constant ionic strength in solution. Soils were initially If-saturated with dilute HCL solutions, whereafter excess HC1 was leached (Bloom and McBride, 1979; Skyllberg, 1993). Predetermined amounts of the cations, balanced by hydroxyl ions (OH ), were added to suspensions of the protonated soils. DOC was measured after centrifugation.

16 The results clearly showed that the counter ion composition strongly affects the solubility, and that the organic matter of different horizons reacts very differently to protonation (Table 1). DOC values for protonated soils may be regarded as reflections of intrinsic organic matter properties (carbon structure, type and density of functional groups). Data from an ordinary iron podzol (acc. to Tamm, 1931) are included for comparison.

Tabell 1. Soil organic matter properties before and after protonation

IP-F IP-H HP-F HP-H HP-E, Homogenized soil: NacuCi2-exch> cmolcNa+/kg o.m. 0,19 0,19 0,18 0,19 0,19 Kcuciz-exctv cmolcK7kg o.m. 3,1 1,9 2,0 0,9 «1 Mgcucn-exch. cmolcMg27kg o.m. 2,54 2,27 3,10 2,00 0,70 Cacuc,2-exch, cmolcCa27kg o.m. 20,96 14,84 15,72 6,73 4,18 Alcuciz-exch. cmolcAl37kg o.m. 2,20 6,64 4,32 29,42 87,36 FeCuci2-exciv cmolcFe37kg o.m. 0,67 1,72 1,27 5,20 1,64 DOC, mg/1 65 35 30 16 9 Protonated soil: DOC, mg/1 34 31 25 46 68

The batch titrations, which exchanged H+ for Na+, Ca2+ or Al3+, showed that each ion has its unique effect on DOC. For example, substitution of H+ with Na+, Ca2+ and Al3+, equivalent to 50 % of the CECX of the F- layer organic matter, resulted in DOC values of 200, 115 and 23 mg/1, respectively. Effects differed, however, considerably between different intrinsic organic matter properties. Hence, the same manipulations applied to the Eh-layer material resulted in DOC values of 575, 110 and 14 mg/1, for Na,Ca and Al. These figures should be compared with each other and with DOC values for the fully protonated materials (tab. 1), i.e. 25 (HP-F) and 68 (HP-Eh) mg/1. All manipulations were replicated and results were consistent throughout.

Some implications of the study: - The prevalent organic matter solubility and mobility in soils is very much a result of a dynamic equilibrium between the exchange complex and its cationic solution environment. - Major changes of the cation composition in the soil solution, brought about by e.g. anthropogenic soil acidification or liming, may cause major changes in the equilibrium soil solution DOC. This will directly affect the export of organic matter from terrestrial systems. Directions and magnitudes of changes are predictable, provided that the pre-change composition of exchangeable cations is known. - The stability of SOM in this humic podzol, typically located in a hydrological discharge area, is almost entirely due to its high degree of A1 -saturation.

References

Bloom P R. & McBride M.B., 1979. Metal ion binding and exchange with hydrogen ions in acid-washed peat. Soil Sci. Soc. Am. J. 43, 687-692. Skyllberg U., 1993. Acid-base properties of humus layers in northern coniferous forests. Dissertation. SLU, Dept, of Forest Ecology. Tamm O., 1931. Studier over jordmanstyper och deras forhallande till markens hydrologi i nordsvenska skogsterranger. Medd. fran Statens Skogsforsoksanstalt, Hafte 26, N:r 2.

18 CLAY MINERALOGY OF SWEDISH PODZOL PROFILES.

Per-Arne Melkerud Swedish University of Agricultural sciences Department of Forest Soils Box 7001 S-750 07 UPPSALA

Clay mineralogy of soil profiles is proposed to have great influence upon the geochemical processes in our environment. However clay mineralogy is a very comprehensive theme and it is very much handled in relation to a special subject or question.

Soil-forming processes and nutrient release in forest ecosystems are very much dependent on the prevalent weathering processes (Bache 1983). Since weathering processes are favoured by fine textured soils (a large, chemically active surface area), the knowledge of clay mineral distribution and mineralogy of the finest fractions in soils is of utmost importance (Kodama 1979; Loveland 1984; Wilson & Nadeau 1984).

The minerals in the clay fraction will probably be among the constituents in the soil which will first give eveidence of a change in the weathering intensity. Weathering has been going on for several thousands of years in Swedish soils, resulting in the development of specific soil profiles which would presumably maintain a steady state unless the environment changed.

Presently, a wider definition of clay is quite difficult to give in precise terms. However, clay is a material which under normal conditions and moist has the ability to show plasticity together with such properties as adsorption, hydration, solvation, ion exchange and in addition also hardening at burning. Clay is mainly built up from fine-grained crystalline inorganic material comprising hydrous phyllosilicates with the major chemical elements. The components have a space order mainly as layers of Si02-tetrahedrons and Al(OH)3-octahedrons. Beside these there are non-crystalline material composed mainly from the components Si02, A1203, Fe203, FeO, MnO and H20.

In this context clay mineralogy concerns minerals in the clay fraction of

19 Swedish podzol profiles and firstly concentrated on phyllosilicates. For our environment, a question of crucial importance is whether or not clay minerals have any importance for mobilization of aluminium. Especially as these phyllosilicates are mainly built up from alumina and silica with a variation of spatial lattices.

The origin of clay mineral distribution in Swedish soils can be explained by three major sources. Firstly, the clay minerals have been inherited from earlier populations or deposits of clays. Such an example is kaolinite which has been formed by chemical weathering during pre- Quatemary times. During the glaciation saprolites have been mixed with fresh comminuted bedrock material and later on deposited as till. In this case kaolinite could be found in all horizons of the soil profile.

The second source in the Quaternary deposits is made up from primary or secondary minerals which have been transformed into more stable secondary minerals. Example of this kind is vermiculite which could be transformed from homblend, chlorite or biotite. In this case the transformation into vermiculite is very closely connected to soil formation processes.

The third type could be made up through neoformation of secondary minerals in equilibrium with the present physicochemical environment and basal components. Such newly formed minerals in the clay fraction could be ferrihydrite or goethite, the major cause behind the rustred colour of the Bs horizon of podzols. Probably also kaolinite is neoformed in the eluvial horizon on behalf of decomposition of other phyllosilicates or transformation from amorphous aluminosilicates.

The mineralogical composition of the clay fraction of tills has been studied within the Swedish acidification programme (Melkerud 1983; 1984; 1986; 1989) and projects about soil formation on tills (Olsson & Melkerud 1989). Today more than 20 profiles have been examined throughout Sweden, from Nunasvaara close to Vittangi in Lapland to Soderasen in Skane, the southernmost part of Sweden.

The results of the mineralogical analyses have revealed that there is a specific concistency in the of clay minerals in podzol profiles. Beginning with the parent material for soil formation, the clay minerals in the C horizon are often characterized by a dominance from illites (10 A, 5 A and 3.3 A peaks in XRD diagrams). The ratio between dioctahedral and trioctahedral illites could be dicemed by the ratio of the 001/002 XRD-

20 peaks at 10 A and 5 A, respectively. A low ratio, about 2-3 indicate presence of dioctahedral ilite.

The second most abundant mineral could be chlorite but the distribution of chlorite is often closely related to mafic minerals in the surrounding bedrock. In areas characterized of deep weathering and kaolinization of the bedrock, kaolinite could be mixed into the parent till material. Depending on the similarity of the XRD peaks when kaolinite occurs together with chlorite it is difficult to decide whether the 7 A and 3.5 A peaks are coming from kaolinite or chlorite. Methods to reveal the existence are either pretreatment with hot hydrochloric acid, heat treatment or slow XRD scanning over the 3.5 A peak. Acid treatment will result in the dissolution of chlorite and kaolinite will withstand the treatment. On the other hand chlorite will resist heat treatment and also the 14 A peak will be enhanced while the kaolinite is disintegrated. Slow scanning over the peak at 3.5 A will reveal existence of either chlorite or kaolinite or both of them. Also if chlorite is present a prominent peak will appear at 4.7 A.

Complementary to clay minerals in the clay fraction also primary rock forming minerals like quartz, potassium feldspars, plagioclases and amphiboles are mostly present.

In the Bs horizon, the results of soil-forming processes are often revealed by the characteristic peaks from vermiculites at 14 A. Mostly this mineral appearing in the enrichment horizon shows properties of interlayering the lattice by hydroxy aluminium polymers. This property is often revealed by withstanding contraction of the lattice when the specimen is saturated with potassium and analysed by XRD. The 14 A peak will remain at 14 A insted of changing the position to 10 A, which is characteristic for true vermiculite which is not interlayered by hydroxy A1 polymers. This complex of aluminium hydroxy compounds could be a potential source for aluminium mobilization.

Earlier experiences from podzol profiles in Sweden (Gjems 1967; Melkerud 1983; 1986) showed that the most dominant XRD peak at 14 A came from smectite (Mg-saturated) with the ability to swell when treated with glycerol or ethylene glycol. Another property which is correlated to soil smectite (Thorez 1975, 1976) is the contraction of the lattice to 12.4 A at potassium saturation and XRD analysis at room temperature.

21 However recent investigations have shown that the mineralogy in the E horizon can be more complex and include mixed layer minerals together with smectite. Sometimes the determination of the mineral character is very much influenced by the treatment of the specimen at the laboratory and also the humidity when the specimen is analysed.

In E horizons of Swedish podzols also kaolinite could occur. Sometimes explained as neoformation of kaolinite. hi the case of comparably high amounts and distributed through the whole soil profile it could be inherited from earlier weathering which has little to do with the quite recent postglacial soil forming prosesses.

The content of primary minerals will often be suppressed by the high amounts of phyllosilicates in the E horizon and this is shown by decrease in content of quartz, microcline and plagioclases. Tendencies of actual changes of clay minerals in a soil profile could always be difficult to verify unless real amounts were measured in relation to an internal weathering resistent standard. Other disturbances while calculating budgets about the distribution of minerals in the clay fraction is the contribution from larger grain sizes which are disintegrated by e g physical weathering. References.

Bache, B. 1983. The implications of rock weathering for acid neutralization. In Ecological Effects of Acid Deposition. National Swedish Environmental Protection Board - Report PM 1636. 175-187 pp. Gjems, 0.1967. Studies on clay minerals and clay-mineral transformation in soil profiles in Scandinavia. Meddelelser fra Det Norske Skogforsdksvesen nr 81. Bind XXI. 303-415 pp. Loveland, 1984. The soil clays of Great Britain: n. England and Wales. Clay Minerals 19:5. 681-707 pp. Melkerud, P.-A. 1983. Quaternary deposits and bedrock outcrops in an area around Lake Gardsjon, south-western Sweden, with physical, mineralogical and geochemical investigations. Reports in Forest Ecology and Forest Soils 44. Department of Forest Soils, Swedish University of Agricultural Sciences. 87 pp. Melkerud, P.-A. 1984. Distribution of clay minerals in soil profiles - a tool in chronostratigraphical and lithostratigraphical investigation of till. Striae 20. 31-37 pp. Melkerud, P.-A. 1986. Smectite formation below stands of 1st, 2nd and 3rd generations of coniferous forests. In Proceedings of the Nordic Symposium CLAY MINERALS - MODERN SOCIETY, in Uppsala, Sweden, Nov. 20-21, 1985. (Eds. N-A Shaikh & N.-G. Wik). Grafiska Tryckeriet AB, Uppsala. Melkerud, P.-A. 1989. Impact on geochemistry and mineralogy by artificial acidification of an orthic podzol. In Weathering; its Products and Deposits. VOLUME I. Processes. (S.S. Augustithis ed.). Theophrastus Publications, S.A. Athens, Greece. Olsson, M.T. & Melkerud, P.-A. 1989. Chemical and mineralogical changes during genesis of a podzol from till in S. Sweden. Geoderma 45, 267-287 pp. Thorez, J. 1975. Phyllosilicates and clay minerals. Lelotte, Dison. 579 pp. Thorez, J. 1976. Practical identification of clay minerals. Lelotte, Dison. 90 pp. Wilson, MJ. & Nadeau, P.H. 1984. Interstratified clay minerals and weathering processes. In The Chemistry of Weathering (J.E. Drever ed.) D. Reidel Publishing Company, Dordrecht, Holland.

23 EFFECT OF TREE SPECIES AND SOIL PROPERTIES ON NUTRIENT IMMOBILIZATION IN THE FOREST FLOOR

Karsten Raulund-Rasmussen and Henrik Vejre

Unit of Forestry Royal Veterinary and Agricultural University Thorvaldsensvej 57 DK-1871 Frederiksberg C Denmark.

The forest floor, ie organic matter above the mineral soil, is a critical link in the nutrient cycle of forest ecosystems. Nutrients supplied in dead organic matter are made available for tree roots after mineralization by saprophytic microorganisms. To investigate the effect of tree species and soil properties on organic matter accumulation, an area-based sampling of the forest floor was carried out in a 28 years old tree species trial including Norway spruce (Picea abies), Douglas fir (Pseudotsuga mensiezii), beech (Fagus sylvatica) and oak (Querqus robuf) on a poor, sandy soil in western Jutland and a fertile, loamy soil on the island of Lolland. The litter samples were analyzed as follows; the soil solutions were filtered, and acidity, content of Ca, Mg, K, Al, N03", SO/, Cl", PO/', along with DOC were measured. The organic matter were analyzed for exchangeable cations, extractable acidity, total C, N and P. The accumulation of C, N and P in the forest floor was significantly higher at the sandy site than at the loamy site under all tree species. At the loamy site, oak was characterized by lesser accumulation of C, N and P than all the other species. Remarkably, the C/N ratios showed no substantial differences, whereas the C/P ratios were significantly higher at the sandy site for all species. pH was significantly lower at the sandy site for all

24 species, and among the species, pH was lower in the conifer forest floors than in the broadleave forest floors. The concentration of ammonium, nitrate and phosphate in the soil solution was much higher at the loamy site under all species showing a stronger microbial activity. It is therefore hypothesized that the differences in accumulation rates were partly caused by differences in the mineralization regimes. Strong root infiltration in the forest floors at the sandy site compared to almost none at the loamy site, is probably responsible for the differences in mineralization rate due to competition between the organic matter decomposers and the tree-roots and associated mycorrhiza for nutrients.

25 Podzolization in Finland

Michael Starr and Pekka Tamminen

Department of Forest Ecology, The Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland (tel. +358-0-557 051, fax: +358-0-857 2575)

Abstract

The podzolization of forty "iron podzols" located throughout Finland was studied. Samples of the E, upper B (Bl), remaining B, and C horizons were sampled and profile descriptions made. Morphological properties, such as horizon thickness and colour, and dithionite and pyrophoshate extractable Fe and A1 concentrations were used to describe the degree of podzolization. The clearest minima in the E horizon and maxima in the Bl horizon was shown by the dithionite extraction compared to the pyrophosphate extraction, and by A1 compared to Fe. Bl horizon Munsell Color value was found to be significantly negatively correlated with Bl horizon organic matter content, and concentrations of pyrophosphate extractable Fe and Al. B1 horizon hue was significantly negatively correlated with dithionite and pyrophosphate Fe. Of a number of environmental factors (geographic, climatic and topographic variables), elevation, which is related to both time since emergence from post-glacial waters and climate, was the most important variable explaining dithionite and pyrophoshate extractable Fe and Al concentrations. There was a tendency for podzols in the south and low lying areas to be weakly developed (weaker colour horizonation and Fe, Al and organic matter illuviation) and for the most developed podzols to be at higher elevations in eastern and northern Finland.

02.09.94 PEDOGENIC EVALUATION OF SOME SANDY, WEAKLY PODZOLIZED SOILS IN AMLI, SOUTHERN NORWAY.

Line Tau Strand

Agricultural University of Norway,Department of Soil and Water Sciences, P.O. Box 5028, N-1432 As, Norway.

The vertical distribution of carbon, iron and aluminium was used to evaluate the pedogenesis in seven sandy, weakly podzolized soils in Amli, southern Norway. Carbon was measured as total carbon. Iron and aluminium were determined by selective extraction, in this case the extractants were pyrophosphate, oxalate and dithionite. Emphasis was put on the two B-horizons recognized in these podzols. The upper, thin Bhs- horizon qualified as a podzol horizon according to most classification systems while the lower Bs-horizon generally did not. Two alternatives were investigated 1: The Bhs-horizon was the only true podzol horizon, the properties of the Bs-horizon were due to either in situ weathering or precipitation of iron oxides and proto-imogolite due to biodegradation of organometallic complexes in the overlying Bhs-horizon, 2: Both the Bhs- and the Bs-horizons are podzol horizons, as podzolization includes the inorganic precipitation of aluminium and iron, and then subsequent precipitation of organic compounds on the aluminosilicate and iron oxide surfaces. The vertical distribution regardless of extraction method suggested that migration of C, Fe and A1 has taken place (Figure 1.). Based on the Bhs-/E-horizon ratios aluminium appeared in general to be the element that was most sensitive to podzolization. Correlation analyses suggested that carbon was connected to A1 both through organometallic complexes and

27 through inorganic amorphous Al.

9/1009 9/100g

cm 0 . 0 E Bhs 10 •

30 ■

*0 "

BC 50 ■

6 0 •

Figure 1. Example of vertical distribution of Fe and Al determined by selective extraction Fep, Alp = pyrophosphate, Fe0, Al0 - oxalate, Fed , Ald - dithionite.

Imogolite was detected by transmission electron microscopy in all Bs- horizons, suggesting that Al may have migrated inorganically. The distribution of silicon extracted by oxalate supported the findings of imogolite, though the ratios between inorganic amorphous Al and Si suggested that inorganic amorphous Al may have other Al-sources than allophanes and imogolite. If the formation and precipitation of imogolite is considered a main process in podzolization then the Bs-horizon most definitely should be considered a podzol horizon. Iron-extractions in the Bhs-horizons were poorly correlated with total carbon. The presence of ferrihydrite and the use of total carbon were thought to explain the poor

28 correlation between iron and carbon. Iron was if anything negatively correlated to inorganic A1 and Si in both the Bhs- and the Bs-horizon implying that inorganic migration of Fe as Fe-Al hydroxy polymers or as Fe-Al-Si sols was not important. This suggested that the most reasonable explanation for the redistribution of Fe was migration of Fe as organometallic complexes. The iron in the Bs-horizon may then be due to release of iron caused by biodegradation of the iron organometallic complexes this may also be the case for the A1 connected to organometallic complexes. This iron and aluminium released by biodegradation could be translocated and precipitated in the Bs-horizon. In this case the Bs-horizon would be a secondary result of the podzolization process but not a podzol horizon as the Bhs-horizon. An other possibility may be that the iron oxides and the imogolite present in the Bs-horizon is due to in situ weathering and have not been translocated far at all. The present study focuses on the difficulties of using selective extraction in interpreting the pedogenesis of podzols. Selective extractions may indicate possible pedogenesis but additional analysis such as: hydro-chemical budgets, total chemistry, various mineralogical techniques, and micromorphological analyses must be carried out in order to establish the pedogenesis more precisely.

29 ACCUMULATION OF C, N AND P IN THE FOREST FLOOR: 1. EFFECTS OF THINNING AND SOIL PROPERTIES

Lars Vesterdal and Karsten Raulund-Rasmussen. Department of Economics and Natural Resources, Unit of Forestry, Royal Veterinary and Agricultural University, Thorvaldsensvej 57, DK-1871 Frederiksberg C, Denmark.

In order to investigate the effect of thinning and soil properties on accumulation of carbon, nitrogen and phosphorus in the forest floor of even aged Norway spruce stands, an area-based sampling was carried out. Four thinning intensities (unthinned, 83%, 67% and 50%, respectively, of unthinned basal area) were investigated on three soil types in Denmark. The soil at Senderskov (Mollic Hapludalf) was of relatively high nutritional status and developed from calcareous parent material with a texture of sandy loam/loam. The soils at listed Nerskov (Mollic Hapludalf) and Store Dyrehave (Typic Dystrochrept) were of low to intermediate nutritional status and had textures of sandy loam and loamy sand, respectively. The climate is approximately identical at the three sites.

The effect of thinning on accumulated carbon and nitrogen was significant at the relatively nutrient rich soil at Sonderskov and at the nutritionally intermediate soil at Tisted Norskov. Accumulated phosphorus was significantly affected by thinning at Sonderskov and at the nutritionally poorestsoil at Store Dyrehave. The accumulated amounts were linearly correlated with thinning intensity. pH tended to be highest in the heaviest thinned stands, while C/N and C/P ratios tended to increase by thinning

30 intensity. It is hypothesized that the differences in accumulation may be due to a more favorable microclimate and substrate quality for saprophytic organisms in the heaviest thinned stands. However, the differences between sites were greater than differences between thinning intensities. The accumulation of carbon, nitrogen and phosphorus in the forest floors were much higher at the two less fertile sites with loamy sand and sandy loam (Store Dyrehave and Tisted Norskov) than at the relatively fertile site with sandy loam/loam (Sonderskov). Significant differences in pH and in C/N and C/P ratios at the three sites indicate that the amount of available nutrients influences the mineralization pattern. In addition, at Store Dyrehave where the forest floor had the greatest root density, competition for nutrients and moisture between mycorrhiza-infected roots and free- living saprophytic decomposers may be at least partly responsible for the extremely large amounts of accumulated carbon, nitrogen and phosphorus.

It is concluded that the amounts of carbon, nitrogen and phosphorus in the forest floor of Norway spruce stands may be managed to some extent by means of thinning intensity. However, the effect of site-specific soil properties is much more pronounced. The full paper is submitted to Forest Ecology and Management.

31 WATER HOLDING CAPACITY AND WATER BALANCE IN PODZOLISED FOREST SOIL.

Carl Johan Westman

University of Helsinki, Department of forest ecology P.O.Box 24, FIN 00014 University of Helsinki, Finland

Soil cores were taken from the podzolic mineral soil horizons (E, B1 and B2 ) and parent matter soil (C ) in three pits on each of four forested sites (61° 48’ N, 24° 19’ E) representing a site fertility continuum. The soils of the sites have developed on glaciofluvial deposits or shallow silty till over a 9 500 year period. Annual mean precipitation amounts to 709 mm and mean temperature is 2.9 °C. Elevation above sea level is 160 m. Density of soil and water content along a pressure head gradient (1-1500 kPa) were determined from the core samples, and particle size distribution and loss on ignition from bulk samples. On each of the site five sets of rain gauges and soil water tension meters were installed, and througfall and water tension at 5,25, 50 and 75 cm depth in soil has been recorded daily during the non-frozen period. Water holding capacity of the soil was described by fitting a Van Genuchten equation to the experimental data, in most cases the fit was very good (r2 > 0.95). The podzolic E, B1 and B2 horizons at sites on the coarse glaciofluvial sediments retain 3-4 times more water than the parent material (C horizon) at 100 mbar tension when gravitional water movement in soil tends to sease. At the site on silty till E and B horizons have developed towards looser structure, and thus drain more easily than the more compacted bottom soil. At the site where a silty soil layer is covered by a sandy top soil

32 the water holding properties of the E and B horizons resemblences those of the sites at poorer end of the continuum, while the properties of the bottom soil (C) are those of the site at silty till. It is obvious that soil formation processes like weathering, transportation and formation of organic compounds and precipitates in the profile has changed the composition of the soil matrix and, consecutively changed its water holding capacity. In the upper soil horizons the amount of the coarser particle fractions has decreased while the amount of fine material has increased. In the coarse grained soils the neo-formed fine material is particularly associated with the silt fraction. By substituting the pressure head value in the equations with measured soil water tension values daily layervise estimates of mineral soil water content was obtained. On the coarse sandy sediments the amout of water hold by the top soil is high in comparison to that hold by the corresponding parent material soil layer. It is also obvious that upon rain events exess water percolates fast through these soils. During periods with low rain frequency water uptake by trees thus takes place mainly in the top soil layer. On the silty till soil the water balance of the studied soil layer is almost double that of the glaciofluvial soils. On these sites summer rain events have only minor influence upon deeper soil layers while water uptake by trees clearly influences the amount of water in deeper soil layers. Within limits set by precipitation and evapotranspiration the properties of the soil profile determines the soil water holding capacity the water balance of the site. Changes in soil formation factors like climate thus impingue upon site productivity.