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Stocks and annual fluxes of organic carbon in the mineral soil cover of Estonia/Orgaanilise susiniku varud ja aastavood Eesti mineraalmuldades.

INTRODUCTION

Data on the annual cycling of soil organic carbon (SOC) in certain soil types and land use conditions form a good basis for understanding the peculiarities of soil formation, development, and functioning (Kern et al., 1998; Katterer et al., 2004). Systematized parameters of mean annual turnover of SOC according to soils and land use are needed for the introduction of sustainable management and ecologically sound protection of soil cover (Korchens et al., 1998; Lal et al., 1998; Halvorson et al., 2002).

Soil cover (solum), which forms an inseparable functional part of terrestrial ecosystems, determines in natural areas the floristic composition of plant cover (site type), mean annual productivity, and annual litter fall intensity onto the soil (Kolli, 1988). According to the peculiarities of soil mineral composition, actual humus status, and organic matter influx, the specific to soil-type associations organisms destructing soil organic matter are formed.

Besides the direct influence of soil cover on an ecosystem and on its plant cover, a clearly visible feedback of plant cover and soil fauna on soil properties exists. However, this feedback influence is concentrated mainly in the epipedon, in which the annual litter fall is accumulated, most soil organisms are acting, and most soil processes are initiated. In connection with this, the established epipedon type serves as a good indicator in evaluating the material cycling characteristics of ecosystems (Kolli et al., 2009). Therefore, natural ecosystems specific to certain soil types with optimal (sustainable on a long-time scale) floristic and faunal richness also serve as good biodiversity examples (models) for particular pedo-ecological conditions.

Certain epipedon properties that exist in natural conditions also persist after land use change (cultivation). Only high-input land management (drainage, fertilization, liming) completely overshadows the soil-type specific relationships and characteristics formed in natural conditions. As a result of this, an anthric epipedon is formed.

The main task of this study is to analyse the annual cycling and balance of SOC (Mg SOC [ha.sup.-1] [yr.sup.-1]) in the main Estonian mineral soil groups in natural (or weakly influenced) and cultivated conditions. As annual phytoproductivity and therefore annual SOC cycling largely depend on soil humus status and soil-plant system functioning (Paustian et al., 1997; Smith et al., 1998), our analysis was realized on the basis of data on soil SOC stocks and productivity parameters. Data on the same areas are presented in detail in a previous publication (Kolli, 1992).

MATERIALS AND METHODS

The quantitative characteristics of humus status of soils and annual phytomass fluxes of plant cover originate from the soil profile horizons database (DB) 'Pedon' and humus status research transect DB 'Catena'. These DBs (formed since 1967) were created by us for the characterization of the main Estonian soil types at ecosystem level and for studying their functioning in typical areas of their distribution (Kolli, 1988).

In these DBs, SOC stocks (Mg [ha.sup.-1]) were calculated according to soil horizons on the basis of SOC content (g [kg.sup.-1]) and soil bulk density. The SOC content in fine-earth soil samples (particle diameter <1.0 mm) was determined by the Tyurin method, that is by wet digestion of organic carbon with acid dichromate (Vorobyova, 1998). In 358 soil profiles, the SOC content was determined for each horizon, but for 322 profiles (erosion-affected soils) the subsoil SOC content was determined in only 10-15% of cases.

Bulk density was determined for mineral soil horizons with 50 [cm.sup.3] metallic cylinders, and for forest floor and thin histic horizons using a 25 cm x 40 cm (0.1 [m.sup.2]) metallic frame. Bulk density samples were taken from ~10% of the profiles. The content of the coarse soil fraction (by volume) was determined during fieldwork.

Stocks of SOC were estimated for two soil layers: (1) the epipedon (EP, topsoil or humus cover), which consists of the forest floor and/or humus, raw humus, and peat (histic) horizons, and (2) soil cover (SC, or solum) as a whole, whose depth extends from the surface to the unchanged parent material or the C horizon. In the presence of the BC horizon, the thickness of soil cover was measured to the middle of the BC horizon. Therefore SC consists of EP and subsoil (SS, eluvial and illuvial horizons).

The individual profile data were generalized by land use and soil types. The total SOC stocks in mineral soils were calculated on the basis of the distribution area of each soil type and its SOC stock per hectare. The data on the distribution of mineral soils are based on a large-scale (1 : 10 000) soil map (Kokk, 1995). The area covered by mineral soils is about 32 351 k[m.sup.2] (Kolli et al., 2009). The distribution of mineral soil cover according to soil groups and land use is presented in Fig. 1. The names and codes of soil groups (Table 1) are given according to the World Reference Base for Soil Resources (WRB; FAO, 2006). To process the collected data, two-way Analysis of Variance followed by Student's test of homogeneous groups was used.

[FIGURE 1 OMITTED]

RESULTS AND DISCUSSION

Stocks of SOC by soil groups

The mean SOC stock densities (Mg [ha.sup.-1]) in the SC of 16 soil groups are given in Fig. 2. In automorphic soils EP SOC stocks varied between 16 and 80 Mg [ha.sup.-1]. Significantly lower SOC stocks were observed in the EP of automorphic Haplic Podzols (group V) and in that of arable soils degraded by erosion (XII). Soils with higher carbonate and clay contents had larger EP SOC stocks. In hydromorphic soils the EP SOC stocks were significantly larger compared with automorphic soils (exceptions were strongly podzolized epigleyic and coastal soils). The largest stocks were characteristic of Histic Gleysols (EP composed of sapric peat).

The retention of SOC in the SC of mineral soils depends to a great extent also on SS thickness and its capacity to retain SOC. The largest SOC stocks in the SS (58-70 Mg [ha.sup.-1]) are characteristic of the humus-illuvial horizon of strongly podzolized epigleyic soils. The smallest SS SOC stocks (5-8 Mg [ha.sup.-1]) are characteristic of thin Leptosols and coastal and eroded soils.

Data selection for analysing differences in SOC sequestration was based on the one hand on land use (i.e. forest and arable soils) and, on the other hand, on soil properties (i.e. automorphic and hydromorphic, and calcareous and non-calcareous soils) (Table 2). In most cases (the only exception is the thickness of automorphic soils) the differences between forest and arable SC parameters (thickness and SOC stocks) are not significant (p > 0.05). The thicknesses of SC of calcareous soils are significantly lower, but SOC stocks are significantly higher compared with non-calcareous soils. The main cause of higher SOC stocks in SC is a higher SOC concentration in the EP of calcareous soils. Higher SOC stocks are observed also in hydromorphic soils compared with automorphic soils, but automorphic soils are usually deeper.

[FIGURE 2 OMITTED]

Pedo-ecological causal regularities of SOC sequestration

In Estonian mineral soils a total of 323 [+ or -] 46 Tg ([10.sup.12] g) SOC is retained (Kolli et al., 2009). The distribution of total SOC stocks in mineral soil cover by land use, SOC quality, soil calcareousness, and vertical distribution is given in Fig. 3.

The SOC retention capacity (Mg SOC [ha.sup.-1]) is the amount of SOC that a specific soil can retain or capture in equilibrated conditions of soil functioning. The actual SOC stocks may coincide with theoretical retention capacity or may be very different from it. By selecting for analyses only soils with typical for an area plant covers, we may obtain results that are very close to the theoretical (benchmark) SOC retention capacity of a soil. The SOC retention capacity of a soil depends, besides SOC concentration, very much on peculiarities of soil type (thickness of EP and SC, moisture regime, texture, and carbonate content) and soil management (Robert, 2001; Rusco et al., 2001).

The SC thickness of mineral soils varied between 15 and 93 cm (Table 1). The greatest SC thickness was characteristic of Albeluvisols and some deluvial soils. Thinner SC was found in Leptosols and soils formed in coastal and severely eroded areas. In most cases, the EP of arable soils of the same type was significantly thicker than that of forest soils. No substantial differences between the thicknesses of the same type of natural and cultivated SC were established.

The influence of soil moisture conditions on soil SOC stocks is clearly visible (DeBusk et al., 2001). In mineral soils the SOC stocks increase in the following sequence of soil moisture conditions: dry < normal moisture < gleyed or endogleyic < gley- or epigleyic < histic gleysoils. The area-weighted average SC SOC density of hydromorphic soils exceeded that of automorphic soils in both calcareous and non-calcareous soil groups (Table 3). Although SOC densities in hydromorphic soils are quite high, their humus quality is low. The humus of hydromorphic soils is unstable, chemically unsaturated, and weakly condensed (Kolli, 1992; Reintam, 1993).

In the SS of non-calcareous soils, the SOC stocks were relatively higher than in calcareous soils. Low soil calcareousness is connected with soil profile development (forming of illuvial and eluvial horizons). The SOC density of the SS increased from Leptosols to Podzols and from Eutric Gleysols to Dystric Gleysols. The influence of soil texture on the SOC retaining capacity has been well described in many works (e.g. Reintam, 1997; Percival et al., 2000; Callesen et al., 2003).

Land use change from forest to arable land causes a decrease in the exogenic SOC stocks and homogenization of SOC concentration (Rosell & Galantini, 1998; Pulleman et al., 2000). Although the epipedon thickness of forest soils is noticeably smaller than in arable soils, another factor, the SOC concentration of forest soils, is generally higher, and, consequently, the SOC stocks in the epipedon and soil cover as a whole may be approximately similar in forest and arable soils. Land use change does not cause substantial changes in the SS fabric and humus status, since the thickness of SC and the level of SOC stocks in the SC remain approximately the same. Compared with SS, EP is always more sensitive to external influences. The functional value of differently sequestrated SOC or of different kinds of soil organic matter can be very different (Table 4). This has to be taken into account in the sustainable management of SOC.

Annual fluxes of SOC

Long-term periodical means of the annual fluxes of SOC input and output in equilibrated natural ecosystems formed in concordance with soil peculiarities are presented in Fig. 4. In most equilibrated ecosystems the annual input and output fluxes of SOC vary cyclically from year to year (Paustian et al., 1997; Korchens et al., 1998; Kleja et al., 2008). If on a long-term scale the SOC stocks of soil cover remain practically unchanged, then the periodical input and output balance should also be equal (input = output), or in actual circumstances no additional SOC sequestration nor SOC discharging should occur. Major differences in annual cycling levels exist between different soil types and regions (Chertov et al., 2002; West & Post, 2002; Sitaula et al., 2004).

[FIGURE 4 OMITTED]

In Estonia the annual SOC balance is highest (> 3.5 Mg [ha.sup.-1]) in high productivity forests formed on automorphic Luvisols, Cambisols, and Albeluvisols. In most cases the productivity and therefore the annual litter fall on hydromorphic soils is lower compared with their automorphic analogues. In Norwegian spruce ecosystems the annual input rates are in the range from 1.9 to 2.3 Mg C [ha.sup.-1] [yr.sup.-1] (Kleja et al., 2008). The lowest productivity and therefore lowest annual SOC cycling is characteristic of very young coastal soils (input and output < 0.5 Mg [ha.sup.-1]). A positive SOC balance (input > output) over a long-time scale is characteristic for deluvial and alluvial soils, but a negative one for soils influenced by erosion (input < output; Fig. 4).

During changes in land use the annual balance of SOC is transformed considerably (Yakimenko, 1998; Pulleman et al., 2000; Kurganova et al., 2007). Besides the hereditary soil fertility, the annual SOC balance depends much on the agrotechnology used (i.e. crops and their rotation, level of subsidies, needs for soil amelioration). The SOC balance is clearly negative in the cultivation of potato and other inter-tilled crops (Fig. 5). Following good agricultural practice, the excessive annual expenses of SOC should be compensated with organic manure or with grown in situ green manure (phytomass). The annual output exceeds input also in the cultivation of cereals, and in case of higher yields the input into the soil is usually higher. For restoring SOC losses when growing cereals, perennial field grasses should be taken into crop rotation. On natural and semi-natural grasslands, the annual SOC in relation to soil cover tends to be positive, but the annual balances are lower compared with forest and arable lands. The only exceptions are alluvial soils and submerged delta soils. Of course, on arable lands with different subsidy levels of agro-technology (from low to high input) may be used. In cases of soil water stagnation (in gleysoils and especially in acidic peaty wet soils) the annual input decreases considerably.

[FIGURE 5 OMITTED]

The main purpose of ecologically sound management is to reach equilibrated cycling of substances which accords with soil cover capability and its main properties. The goal of sustainable SOC management is attaining the theoretically optimal SOC stock density for the soil type, using as a preliminary benchmark the mean weighted SOC-retaining capacity estimated according to the soil group.

The accumulation of SOC in soil in a stable form is a slow process. According to Kolchugina & Vinson (1998), the implementation of ecologically sound soil management practice results in an increase of SOC stocks in forest soils by 0.5% and in arable soils by 0.1% per year. With directed soil management, the annual SOC storage increase may be between 0.1 and 0.7 Mg SOC [ha.sup.-1] (Paustian et al., 1997). The results of Romanovskaya (2006) show that the average loss of SOC from abandoned arable land reaches 0.46 Mg C [ha.sup.-1] [yr.sup.-1], but an increase in SOC storage after a couple of years can be expected. Great SOC stock losses in the first years after a change from forest to arable land use are also reported by other researchers (Percival et al., 2000; Semenov et al., 2008). One of the possible reasons is the greater share of potentially mineralizable organic matter in forest soils. According to Semenov et al. (2008), the share of easily mineralizable organic matter in sod-podzolic forest and arable soils forms, respectively, 6.0% and 3.2% of total soil organic matter.

The turnover period of SOC in EP is much shorter than in SS and it is controllable (primarily on arable lands) with soil management. The main constraints (limiting SOC turnover and the level of productivity) of arable EP may be high acidity, low humus content, low biological activity, unsuitable mineral composition, the raw-humus fabric, and unfavourable moisture conditions. These constraints may be regulated by improving SOC management (e.g. by soil drainage, liming, equilibrated fertilization, and periodic inputs of fresh organic matter).

One way for embedding additional carbon into the soil is to increase soil productivity, which subsequently causes SOC stock increases in soil horizons (Rosell & Galantini, 1998; Halvorson et al., 2002). The optimization of soil humus status should be soil-type specific and arranged with a step-by-step approach to increase both soil productivity and the annual inflow of new organic matter into the soil. For ecologically-based soil management the identification of soil EP type is essential, as it reflects the intensity of SOC cycling (Kolli et al., 2009).

Gleysols should be managed very carefully as there is a risk of losing a large part of SC SOC, which is weakly bound to the mineral soil particles. The reversion of low-fertility arable lands to forests may lead to additional sequestration of atmospheric C[O.sub.2] (Kurganova et al., 2007).

CONCLUSIONS

1. Organic carbon stocks in soil cover and its epipedon are soil-type specific. The weighted mean humus status indices of soil types may be used as benchmarks in the arrangement of sustainable land use from the soil-based (pedocentric) perspective.

2. The aggregate of SOC retained in the mineral soils of Estonia (32 351 k[m.sup.2]) amounts to 323 [+ or -] 46 Tg. Of this (1) 42% is in stabilized humus, 40% in unstable raw humus material, and 18% in forest floor and shallow peats, and (2) 75% of it is situated in the biologically active epipedon and 25% in the subsoil.

3. The mean periodical annual inputs and outputs of soil organic carbon on natural soils vary from 0.2 to 3.6 Mg [ha.sup.-1] [yr.sup.-1] depending on the soil and ecosystem type. In the cultivation of natural soils the hereditary soil humus status and fertility may persist only in low input management conditions. The main goal of sustainable management of soil organic carbon on arable land is the attainment of the cycling of substances equilibrated with soil capability.

doi: 10.3176/eco.2011.4.01

REFERENCES

Callesen, I., Liski, J., Raulund-Rasmussen, K., Olsson, M. T., Tau-Strand, L., Vesterdal, L. & Westman, C. J. 2003. Soil carbon stores in Nordic well-drained forest soils--relationships with climate and texture class. Glob. Change Biol., 9, 358-370.

Chertov, O. G., Komarov, A. S., Bykhovets, S. S. & Kobak, K. I. 2002. Simulated soil organic matter dynamics in forests of the Leningrad administrative area, northwestern Russia. Forest Ecol. Manag., 169, 29-44.

DeBusk, W. F., White, J. R. & Reddy, K. R. 2001. Carbon and nitrogen dynamics in wetland soils. In Modeling Carbon and Nitrogen Dynamics for Soil Management (Shaffer, M. J., Ma, L. & Hansen, S., eds), pp. 27-53. Lewis Publishers, Boca Raton.

FAO 2006. World Reference Base for Soil Resources. World Soil Resources Reports 103, Rome.

Halvorson, A. D., Wienhold, B. J. & Black, A. 2002. Tillage, nitrogen, and cropping system effects on soil carbon sequestration. Soil Sci. Soc. Am. J., 66, 906-912.

Katterer, T., Andren, O. & Persson, J. 2004. The impact of altered management on long-term agricultural carbon stocks - a Swedish case study. Nutr. Cycl. Agroecosys., 70, 179-187.

Kern, J. S., Turner, D. P. & Dodson, R. F. 1998. Spatial patterns of soil organic carbon pool size in the Northwestern United States. In Soil Processes and the Carbon Cycle (Lal, R., Kimble, J. M., Follett, R. F. & Stewart, B. A., eds), pp. 29-43. CRC Press, Boca Raton.

Kleja, D. B., Svensson, M., Majdi, H., Jansson, P.-E., Landvall, O., Bergkvist, B., Johansson, M.-B., Weslien, P., Truus, L., Lindroth, A. & Agren, G. I. 2008. Pools and fluxes of carbon in three Norway spruce ecosystems along a climate gradient in Sweden. Biogeochemistry, 89, 7-25.

Kokk, R. 1995. Muldade jaotumus ja omadused. In Eesti. Loodus (Raukas, A., ed.), pp. 430-439. Valgus, Tallinn.

Kolchugina, T. P. & Vinson, T. S. 1998. Carbon cycle of terrestrial ecosystems of the former Soviet Union. Environmental Science and Policy, 1, 115-128.

Kolli, R. 1988. Pedoecological analysis of phytoproductivity, biogeochemical fluxes of substances and humus status in natural and cultivated ecosystems. Doctoral thesis, Novosibirsk (in Russian).

Kolli, R. 1992. Production and ecological characteristics of organic matter of forest soils. Eurasian Soil Sci., 24(6), 78-91.

Kolli, R., Ellermae, O., Koster, T., Lemetti, I., Asi, E. & Kauer, K. 2009. Stocks of organic carbon in Estonian soils. Estonian J. Earth Sci., 58, 95-108.

Kolli, R., Koster, T., Rannik, K. & Tonutare, T. 2009. Complex indicators reflecting soil functioning activity. J. Plant Nutr. Soil Sci., 172, 630-632.

Korchens, M., Weigel, A. & Schulz, E. 1998. Turnover of soil organic matter (SOM) and long-term balances--tools for evaluating sustainable productivity of soils. Z. Pflanzenernahr. Bodenk., 161, 409-424.

Kurganova, I. N., Yermolaev, A. M., Lopes de Gerenyu, V. O., Larionova, A. A., Kuzyakov, Ya., Keller, T. & Lange, S. 2007. Carbon balance in the soils of abandoned lands in Moscow region. Eurasian Soil Sci., 40(1), 51-58.

Lal, R., Kimble, J. & Follett, R. 1998. Land use and soil C pools in terrestrial ecosystems. In Management of Carbon Sequestration in Soil (Lal, R., Kimble, J., Follett, R. & Stewart, B. A., eds), pp. 1-10. CRC Press, Boca Raton.

Paustian, K., Collins, H. P. & Paul, E. A. 1997. Management controls on soil carbon. In Soil Organic Matter in Temperate Agroecosystems. Long-term Experiments in North America (Paul, E. A., Paustian, K., Elliot, E. T. & Cole, C. V., eds), pp. 15-49. CRC Press, Boca Raton.

Percival, H. J., Parfitt, R. L. & Scott, N. A. 2000. Factors controlling soil carbon levels in New Zealand grasslands: Is clay content important? Soil Sci. Soc. Am. J., 64, 1623-1630.

Pulleman, M. M., Bouma, J., van Essen, E. A. & Meijles, E. W. 2000. Soil organic matter content as a function of different land use history. Soil Sci. Soc. Am. J., 64, 689-693.

Reintam, L. 1993. Humus relationship as a representation of soil resilience in extensive agriculture. In Energy, Environment and Natural Resources Management in the Baltic Sea Region. 4th International Conference on System Analysis, Tallinn, Estonia, May 18-21, 1993, pp. 409-415. Copenhagen.

Reintam, L. 1997. Soil formation. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumae, A., eds), pp. 298-306. Estonian Academy Publishers, Tallinn.

Robert, M. 2001. Soil Carbon Sequestration for Improved Land Management. World Soil Resources Reports 96. FAO, Rome.

Romanovskaya, A. A. 2006. Organic carbon in long-fallow lands of Russia. Eurasian Soil Sci., 39(1), 44-52.

Rosell, R. A. & Galantini, J. A. 1998. Soil organic carbon dynamics in native and cultivated ecosystems of South America. In Management of Carbon Sequestration in Soil (Lal, R.,

Kimble, J., Follett, R. & Stewart, B. A., eds), pp. 11-33. CRC Press, Boca Raton.

Rusco, E., Jones, R. & Bidoglio, G. 2001. Organic Matter in the Soils of Europe: Present Status and Future Trends. ESB, IES, JRC, Ispra.

Semenov, V. M., Ivannikova, L. A., Kuznetsova, T. V., Semenova, N. A. & Tulina, A. S. 2008. Mineralization of organic matter and the carbon sequestration capacity of zonal soils. Eurasian Soil Sci., 41(7), 717-730.

Sitaula, B. K., Bajracharya, R. M., Singh, B. R. & Solberg, B. 2004. Factors affecting organic carbon dynamics in soils of Nepal/Himalayan region - a review and analysis. Nutr. Cycl. Agroecosys., 70, 215-229.

Smith, P., Powlson, D. S., Glendining, M. J. & Smith, J. U. 1998. Opportunities and limitations for C sequestration in European agricultural soils through changes in management. In Management of Carbon Sequestration in Soil (Lal, R., Kimble, J., Follett, R. & Stewart, B. A., eds), pp. 143-152. CRC Press, Boca Raton.

Vorobyova, L. A. 1998. Chemical Analysis of Soils. Moscow University Press, Moscow (in Russian).

West, T. O. & Post, W. M. 2002. Soil organic carbon sequestration rates by tillage and crop rotation: a global data analysis. Soil Sci. Soc. Am. J., 66, 1930-1946.

Yakimenko, E. Y. 1998. Soil comparative evolution under grasslands and woodlands in the forest zone of Russia. In Management of Carbon Sequestration in Soil (Lal, R., Kimble, J., Follett, R. & Stewart, B. A., eds), pp. 391-404. CRC Press, Boca Raton.

Raimo Kolli ([mail]), Indrek Tamm, and Alar Astover

Estonian University of Life Sciences, Kreutzwaldi 1A, 51014 Tartu, Estonia

([mail]) Corresponding author, raimo.kolli@emu.ee

Received 17 June 2011, revised 8 August 2011
Table 1. Studied mineral soil groups, their distribution percentage,
and mean soil cover thickness

Group No.   Soil or soil association after WRB                n (a)

I           Gleyic & Rendzic & Lithic Leptosols (skeletic)   8/12/8
II          Endogleyic & Mollic Cambisols (calcaric)         22/46/10
III         Endogleyic & Cutanic Luvisols (humic)            12/8/-
IV          Fragic & Endostagnic Albeluvisols (umbric)       19/13/-
V           Endogleyic & Albic & Umbric Podzols              28/21/8
VI          Endogleyic & Carbic & Haplic Podzols             31/-/-
VII         Calcic & Mollic Gleysols (calcaric)              15/6/17
VIII        Luvic Gleysols (humic, epidystric)               16/4/3
IX          Umbric & Spodic Gleysols (dystric)               7/2/-
X           Saprihistic Gleysols (eutric)                    5/1/-
XI          Epigleyic & Fibrihistic Podzols                  13/-/-
XII         Eroded Haplic Cambisols & Aric Regosols          -/168/-
XIII        Deluvial Cambisols & Luvisols (colluvic)         -/154/-
XIV         Umbric & Histic & Epigleyic Fluvisols (eutric)   -/-/14
XV          Subaquatic & Salic Fluvisols & Salic Gleysols    -/-/8
XVI         Spolic Technosols & Protic Arenosols             1/-/-

               %      Thickness
Group No.   of area    (b), cm

I            1.6      23.3a
II          18.1      47.8c
III          8.4      74.2fg
IV          12.4      92.6h
V            6.5      74.3f
VI           3.3      64.1e
VII         19.0      39.8b
VIII        10.6      55.2cde
IX           6.7      76.0fg
X            6.2      46.9bcd
XI           2.1      75.8fg
XII          1.6      54.2d
XIII         1.2      79.6g
XIV          1.2      37.2b
XV           0.9      15.3a
XVI          0.2      25.0

(a) n--number of studied profiles of forest/arable/grassland.

(b) The letters following the mean indicate significant differences
at p < 0.05.

- Not studied.

Table 2. Comparative analysis of soil cover thicknesses and SOC
stocks according to soil moisture conditions, calcareousness, and
management

                                             Automorphic soils

                                               Thick    SOC
                                               ness,    stocks,
Soil group, characteristic   Parameter    n    cm       Mg [ha.sup.-1]

Forest soils                 Mwp (a)     79    72.4     76.4
Arable soils                 Mwp (a)     88    63.2     84.6
Difference                   d                  9.2      8.2
Significance of difference   p                  0.015    0.167
Calcareous soils             Mwp (a)     121   46.7     89.4
Non-calcareous soils         Mwp (a)     120   77.1     63.1
Difference                   d                 30.4     26.3
Significance of difference   p (a)             <0.001   <0.001
Automorphic soils            Mwp (a)     241   61.9     76.3
Hydromorphic soils           Mwp (a)             --     --
Difference                   d
Significance of difference   p

Soil group, characteristic      Hydromorphic soils

                             n    Thick   SOC
                                  ness,   stocks,
                                  cm      Mg [ha.sup.-1]

Forest soils                 39   63.2    134.0
Arable soils                 13   52.2    104.6
Difference                        11.0     29.4
Significance of difference         0.063    0.112
Calcareous soils             50   43.4    133.6
Non-calcareous soils         48   66.8    111.4
Difference                        23.4     22.2
Significance of difference        <0.001    0.050
Automorphic soils            --    --      --
Hydromorphic soils           98   54.9    122.7
Difference                         7.0     46.4
Significance of difference         0.023   <0.001

(a) Mwp--weighted (by profile number) mean; d--difference between
Mwp-s.

n--Number of studied profiles.

Table 3. Mean (weighted by area) humus status characteristics of
large soil groups

                           Thickness (b)           SOC stocks

                                           SC,
                % of   SC,  EP,   SS,       Mg       EP,   SS,
Soil group (a)  area   cm    %     %    [ha.sup.-1]   %     %

AM CAL          29.5  54.8  49.2  50.8     88.6      76.6  23.4
AM NCL          23.9  81.4  24.9  75.1     65.4      62.5  37.5
HM CAL          36.8  44.8  56.0  44.0    134.0      88.2  11.8
HM NCL           9.8  71.7  23.8  76.2    101.7      43.5  56.5
Mineral soils  100.0  59.1  43.4  56.6    101.0      74.2  25.8

(a) Soil groups: AM CAL--Automorphic calcareous, AM NCL--Automorphic
non-calcareous, HM CAL--Hydromorphic calcareous, HM NCL--
Hydromorphic non-calcareous.

(b) Soil layers: SC--soil cover, EP--epipedon, SS--subsoil.

Table 4. Different kinds of SOC functioning efficiency (a)

                                           Debris and   Stabilized
Kind of functioning                         prehumus       humus

Source of nutrition elements                  +++           (+)
Source of energy for soil biota               +++            +
Initiating soil processes                     +++            +
Regulation of soil exchangeable capacity      (+)           +++
Amelioration of soil physical properties       +            +++
Regulating self-purification capacity          ++           ++
Increasing soil water retention capacity      (+)           ++

(a) Functioning efficiency: +++--high, ++--average, +--low,
and (+)--very low.

Fig. 3. Distribution of total organic carbon stocks (323 [+ or -] 46
Tg) of Estonian mineral soil cover. Features influencing SOC
distribution: A--land use: a--forest land, b--arable land,
c--grassland, and d--other land; B--kind of soil organic matter:
a--stabilized humus, b--raw humus material, and c--forest floor and
shallow peat; C--location in soil cover: a--in epipedon and b--in
subsoil; D--large soil groups: a--automorphic calcareous,
b--automorphic non-calcareous, c--hydromorphic calcareous, and
d--hydromorphic non-calcareous.

A

a      43%
b      28%
c       9%
d      20%

B

a      42%
b      40%
c      18%

C

a      75%
b      25%

D

a      27%
b      15%
c      49%
d       9%

Note: Table made from pie chart.
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Author:Kolli, Raimo; Tamm, Indrek; Astover, Alar
Publication:Estonian Journal of Ecology
Article Type:Report
Geographic Code:4EXES
Date:Dec 1, 2011
Words:4639
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