A Comparative Study of the Latvian Soil Classification with WRB

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1 A Comparative Study of the Latvian Soil Classification with WRB KARKLINS Aldis Latvia University of Agriculture, 2 Liela street, LV 3001, Jelgava, Latvia karklins@latnet.lv Abstract A comparative study of three different soil classification systems: Latvian Soil Classification, World Reference Base for Soil Resources (WRB) and USDA Soil Taxonomy was performed. The objective of the study was to investigate the possibilities to make comparison of soil taxa, which has importance for international communication and information exchange. The focus was put on the comparison of Latvian system with WRB, which is supposed to be a reference base for correlation of national soil units and a tool for international information exchange. The methods used were soil pedons descriptions according to the internationally used guidelines and soil classification according to the above mentioned systems. Additionally, analysis of soil classification principles and criteria were used within each of the system. In the higher categorical level WRB consists of 30 major soil groups (Reference soil groups), Latvia are supposed to correspond to 14 of them. Similarly WRB defines 39 soil diagnostic horizons, 12 diagnostic properties and 7 diagnostic materials. For characterization of Latvian currently we found relevant 13, 8 and 6 respectively of them. For differentiation of the lower categorical level WRB uses predefined so called formative elements the total number of which is 120. For characterization of Latvian 56 presumably might be used. We should recognize that some of them are found very rarely, but the application of some needs further studies. Due to the differences within the classification approach, criteria and priorities used for soil grouping, it is very difficult or even impossible to make reasonable approximation between taxa in Latvian and to internationally used systems, which could be used for practical purposes. Therefore it is recommended in Latvia to use the internationally recognized soil diagnosis scheme and make direct soil classification according to the WRB and Soil Taxonomy rather than realize methods of taxa transformations. Keywords: soil classification units; soil classification systems; WRB Introduction Traditionally genetic approach to soil classification is used in Latvia. Quantitative morphological criteria are not yet employed to separate soil taxonomic units. Such a soil classification system is officially recognized and widely used for different purposes at the national scale. Soil types and subtypes alone or in the form of different associations are basically used as mapping units for large scale (1:10,000) soil maps. This approach fits quite well the local information need, which up to now is mainly is agriculture oriented. Unfortunately, it does not meet requirements for international communication or for domestic use when new type of information should be integrated into the national system and advanced interpretations need to be applied. For example, modeling of natural processes for environmental applications, remote sensing, indirect measurement methods of certain soil Taking into consideration, that local soil classification, first of all, should satisfy the needs of local users giving priority for information end users, e.g. farmers, advisors, there is no doubt about the keeping this system in the future. Gradual development closer to the internationally recognized systems is our goal and working area keeping in mind that international systems are not constant as well. Inventory of the parameters, which are possible to change without destroying the system itself and following the development of international systems are the main objectives to keep the national soil classification system in the line with others and not to lose the main orientation. Soil diagnosis, soil profile description and A comparative study of the Latvian Soil Classification with WRB. Karklins. 199

2 methods of testing physical and chemical parameters necessary for soil classification probably are the first prerequisites which should be accepted and harmonized with the internationally recognized systems to be able to compare soil taxonomic units. World Reference Base for Soil Resources (WRB) was selected as a base for correlation of soil units. WRB is designed for such a purpose to serve as an easy means of communication amongst scientists to identify, characterize and name major types of, to be a tool for better correlation between national systems. To act as common dominator through which national systems can be compared. This study attempts to introduce the principles of the Latvian Soil Classification and to give comparison of its soil units with WRB. The research behind this publication is focused on correlation studies between national soil classification and WRB (and also to Soil Taxonomy) to make possible information exchange and inclusion in the regional and global information systems. Some revision and development of the national classification is also performed where the ideas from WRB are accepted. Materials and methods Investigations include soil profile descriptions performed in Latvia and other countries, using FAO recommended soil description scheme (Guidelines, 1990; Field book, 1998). Soil analysis was performed using internationally recommended methods and procedures (Procedures for soil analysis, 1995). Using this information were classified according to the Latvian Soil classification system (Soil Science, 1999) and WRB (World Reference Base, 1998; Lecture notes, 2001) and also Soil Taxonomy (Keys to Soil Taxonomy, 1998; 1999). Soil correlation table was composed, which is periodically updated when new information is available. Correlation studies are also performed comparing definitions within the different soil classification systems. Results and discussions Rationale of Latvian Soil classification scheme differs quite significantly from WRB and also Soil Taxonomy. The Latvian system is mainly based on soil genesis while both international systems mainly on soil morphology. If genetic approach mainly uses subjective propositions about the possible soil development process, even when there is no evident proof for that, international systems strictly follow certain defined and measurable criteria and morphological features. Genetic classification seems to be more integrated with the local natural conditions (geology, landscape, climate, and vegetation) and as often as not is based on empirical competency and experience. WRB is more generalized and possibly for the purpose of unification might ignore one or other local peculiarity. Accordingly, the compared soil classification systems use different principles of taxonomy (from L. taxis, order and nomos, rule). Soil classification scheme of Latvia includes three dependent (hierarchical) levels: classes, types and subtypes (Figure 1). More detailed subdivision could be applied based on parent material, soil texture (topsoil and subsoil), technological properties (water status, stoniness, relief, degree of cultivation, erosion intensity, slope) and other relevant features that are important for land use. On the highest categorical level the main criteria is hydromorphism, on the second level different features depth of carbonates, evidence of certain processes of soil genesis (podzolization, reductomorphic and oximorphic processes), profile development. For hydromorphic composition and decomposition rate of organic soil materials. On the third level soil types are subdivided into subtypes according to additional properties they have: organic matter content in surface horizons, it thickness, development of genetic horizons. For example, the soil name "Mucky podzolic gley soil" is denotative to Podzolic gleyish soil with more than 50 % of organic matter in topsoil and having continuous layer of gleyed horizon. Therefore soil nomenclature reflects the main processes, which took part in soil formation. For example, soil unit name "Sod calcareous gleysolic soil" designates the process of sod formation (extensive grass root development in upper topsoil) and carbonates within the 60 cm from soil surface, which are the dominating features but some gleyic properties are also recognizable in the profile. 200 A comparative study of the Latvian Soil Classification with WRB. Karklins.

3 The probable advantage of such a system could is that it is simple and understandable for information users who need terminology, that expresses the main features important for soil use. The weakness of the systems - due to the not well and strictly ( hard ) defined and categorized criteria, may result in strong variation among experts involved in decision making. This system, in which the principles were set up more than 70 years ago, has very strong roots and traditions, including materials of large scale (1:10,000) soil survey, performed for all agricultural land and used this classification as a bases for soil mapping unit definitions. Major soil groups classes Separation based on water regime during the soil formation process and the main features obtained within this period Automorphic Developed on relatively highest part of landscape with a deep groundwater table 6 soil types with 22 subtypes Semihydromorphic Developed in planes or depressions on fine textured parent material. Clearly distinguished gleyic and stagnic properties 3 soil types with 22 subtypes Semihydromorphic Developed in planes or depressions on fine textured parent material. Clearly distinguished gleyic and stagnic properties 3 soil types with 10 subtypes Figure 1. The general layout of Latvia soil classification Table 1. gives an overview of occurrence of WRB defined soil classification categories in Latvia. They are separated into three groups. Quite common, occurrence found and identified easily. Some Reference groups in Latvia such as Phaeozems, are slightly different from the central concept of the soil unit, but because of the strong criteria in WRB they should be classified as of Phaeozems. Some of WRB criteria are based on very local conditions, e.g. Leptosols on limestone deposits on riverbanks. Some of WRB defined criteria seem might be relevant and found in some special cases, but still we are not sure about that. Further investigations and soil studies are necessary for verification or deleting from the current list. On the higher categorical level WRB is designed to distribute all diversity of the World s among 30 major soil groups (Reference soil groups). Latvia are supposed correspond to 14 of them. Similarly WRB recognizes 39 soil diagnostic horizons, 12 diagnostic properties and 7 diagnostic materials. For characterization of the Latvia currently we found relevant 13, 8 and 6 respectively of them. For differentiation of the lower categorical level WRB uses predefined formative elements the total number of which are 120. For characterization of the Latvia 56 presumably might be used. Table 2. gives an overview of the Latvian soil types (2 nd classification level) in terms of locally used parameters for its definition and relevance with WRB criteria and subsequently for selecting WRB soil names. A comparative study of the Latvian Soil Classification with WRB. Karklins. 201

4 Because a different approach was used for defining soil units in one and another system, great variation was obtained. It means that probably it is not possible to find out some common dominator or algorithm for direct comparison of Latvia soil taxa with WRB soil units. Even where similar features are recognized to be important for their partition on the higher classification level in both systems (water saturation and redoximorphic features) give significant distribution. It is because in Latvian classification these are divided between two types: Gleyish and Podzolic gleyish. The last one includes with features obtained by two processes going on parallel podzolization and gleization. As distinct criteria are not introduced in terms of depth limits and also expression of gleyic and stagnic features, Latvia gleysols include also other (Planosols, Phaeozems, Luvisols, Cambisols) of WRB, if they have gleyic or stagnic modifier. More homogenous group in terms of comparison is Podzols where both systems use similar criteria for its definition. The only distribution is within the soil type, on the 3 rd level of classification. Table 1. Compliance of Latvia with criteria, defined by WRB WRB classification category Reference soil groups Diagnostic horizons Diagnostic properties Diagnostic materials Formative elements for lower level units Possible occurrence in Latvia quite common in some special cases Histosols, Anthrosols, Fluvisols, Gleysols, Leptosols, Podzols, Planosols, Phaeozems, Albeluvisols, Umbrisols. Luvisols, Cambisols, Arenosols, Regosols. Albic, Argic, Cambic, Histic, Mollic, Ochric, Hortic, Chernic, Spodic, Umbric Abrupt textural change, Albeluvic tonguing, Gleyic, Stagnic. Anthropogeomorphic (aric, garbic, spolic, urbic), Calcaric, Fluvic. Albic (hyper, gloss ), Anthric, Anthropic, Aric, Arenic, Calcaric, Carbic, Cutanic, Densic, Dystric (epi, hyper, orthi ), Entic, Eutric (endo, hyper, orthi ), Fibric, Fluvic, Garbic, Gleyic (endo, epi ), Glossic (molli, umbri ), Haplic, Histic (fibri, sapri, thapto ), Humic (molli, umbri ), Lamellic, Luvic (hypo ), Mollic, Ochric, Ombric, Placic, Planic, Profondic, Protic, Regic, Rheic, Rustic, Sapric, Spodic, Spolic, Stagnic (endo ), Umbric, Urbic. Folic, Fragic. Continous hard rock, Secondary carbonates. Gypsiric, Organic. Calcic (hypo ), Folic, Fragic, Gypsiric, Hortic, Leptic (endo, epi ), Pachic, Petric, Rendzic, Ruptic, Skeletic (endo, epi ), Vermic. Ferric. might be Ferralic properties, Strongly humid Reductic, Sulfidic. Hyperskeletic, Lithic, Reductic, Thionic (proto ), Toxic, Vertic. Some approximation of Latvia Soil classification units and Soil Taxonomy is presented in Table 3. Soil types (Latvia system) are compared with Soil Taxonomy orders, suborders and in some cases with great groups. Similar to WRB there was also observed significant distribution, which do not allow direct comparison of soil units between classification systems. Some approximation of Latvia Soil classification units and Soil Taxonomy is presented in Table 3. Soil types (Latvia system) are compared with Soil Taxonomy orders, suborders and in some cases with great groups. Similar to WRB there was also observed significant distribution, which do not allow direct comparison of soil units between classification systems. 202 A comparative study of the Latvian Soil Classification with WRB. Karklins.

5 Table 2. Approximation of Latvia soil taxa with WRB Soil type Main classification features used in Latvia Automorphic Sod Well developed A horizon calcareous and carbonates in soil profile within 0 60 cm from surface. Brown Clay accumulation in situ in B horizon, carbonates deeper than 60 cm. Podzolic Podzols Anthrosols Weakly developed Soils with some features of podzolization (bleached E horizon). Soils with distinct features of podzolization (well expressed E and Bs/Bhs horizons). Soils development of which is considerably influenced by Man. Includes strongly altered by cultivation, recultivated, technogenic and also buried Young and eroded with week developed or truncated genetic horizons. Soil type Main features for classification used in Latvia Semihydromorphic G7leyish Sod calcareous or Brown with distinct gleyic or stagnic Podzolic gleyish Alluvial Podzolic with gleyic or stagnic Soils developed on alluvial sediments. Hydromorphic Lowland Organic from highly bog decomposed grass Transitional bog Upland bog vegetation. Intermediate stage between lowland and upland bog development. Organic having considerable amounts of recognizable plant tissue. Features, which might be presented (using WRB terminology) Ochric or mollic surface horizons. Cambic subsurface horizon, secondary carbonates, stagnic Ochric or mollic surface horizons. Argic or cambic subsurface horizons, abrupt textural change. Ochric, mollic or umbric surface horizons. Albic, argic, cambic subsurface horizons, albeluvic tonguing, organic soil material. Histic, umbric or ochric surface horizons. Albic, spodic, fragic subsurface horizons. Mollic, chernic, hortic or ochric surface horizons. Argic, cambic subsurface horizons. Organic and anthropogeo morphic (aric, garbic, spolic, urbic) soil materials. Ochric surface horizon. Argic or cambic subsurface horizons. Features, which might be presented (using WRB terminology) Ochric, mollic or histic surface horizons. Argic or cambic subsurface horizons, abrupt textural change, secondary carbonates, gleyic or stagnic properties, calcaric and organic soil material. Ochric, mollic, umbric or histic surface horizons. Albic, argic or cambic, spodic subsurface horizons, abrupt textural change, albeluvic tonguing, gleyic or stagnic properties, organic soil material. Ochric, mollic, umbric or histic surface horizons. Gleyic or stagnic properties, fluvic and organic soil material. Histic surface horizon. Gleyic Histic surface horizon. Gleyic Histic surface horizon. Gleyic Soil type approximation with WRB soil units Luvisols (arenic, stagnic, haplic), Cambisols (stagnic, mollic, calcaric, skeletic, eutric), Leptosols (calcaric, eutric), Phaeozems (stagnic, calcaric). Luvisols (arenic, lamellic, cutanic, dystric, haplic), Cambisols (mollic, dystric, eutric, haplic), Phaeozems (luvic, abruptic, haplic). Albeluvisols (histic, umbric, arenic, abruptic, haplic), Cambisols (mollic, dystric, haplic), Arenosols (hypoluvic, albic, lamellic, dystric). Podzols (densic, carbic, rustic, histic, umbric, entic, placic, fragic, anthric, haplic). Anthrosols (hortic, spodic, luvic, arenic, regic), Phaeozems (luvic, pachic, calcaric, vermic), Regosols (anthropic, garbic, spolic, urbic, humic). Cambisols (calcaric, eutric, haplic), Arenosols (calcaric, protic, eutric, haplic), Regosols (arenic, aric, calcaric, eutric, haplic). Soil type approximation with WRB soil units Gleysols (histic, mollic, calcic, mollihumic, abruptic, calcaric, eutric), Planosols (histic, gleyic, mollic, luvic, arenic, albic, calcaric, eutric), Phaeozems (gleyic, stagnic, glossic), Luvisols (gleyic, stagnic), Cambisols (stagnic, gleyic), Gleyic Arenosols, Regosols (gleyic, stagnic). Gleysols (histic, mollic, umbric, humic, abruptic, dystric, haplic), Planosols (histic, gleyic, mollic, luvic, umbric, arenic, albic, dystric, haplic), Phaeozems (gleyic, stagnic, glossic), Umbrisols (gleyic, stagnic), Luvisols (gleyic, stagnic), Podzols (gleyic, stagnic), Cambisols (stagnic, gleyic), Gleyic Arenosols, Regosols (gleyic, stagnic). Fluvisols (histic, gleyic, mollic, umbric, arenic, stagnic, humic, dystric, eutric, haplic), Fluvic Cambisols. Histosols (sapric, ombric, rheic, dystric, eutric). Histosols (fibric, sapric, ombric, rheic, dystric). Histosols (fibric, ombric, rheic, dystric). A comparative study of the Latvian Soil Classification with WRB. Karklins. 203

6 Table 3. Approximation of Latvia soil taxa with USDA classification system Soil Taxonomy Soil type Approximation to Soil Taxonomy, 1998 Automorphic Sod calcareous Inceptisols (Udepts: Eutrudepts) Mollisols (Rendolls: Haprendolls, Udolls: Argiudolls, Hapludolls) Brown Alfisols (Udalfs: Hapludalfs), Mollisols (Albolls: Argialbolls, Udolls: Paleudolls) Podzolic Entisols (Psamments: Quartzipsamments, Udipsamments), Inceptisols (Udepts: Dystrudepts), Alfisols (Udalfs: Glossudalfs, Hapludalfs), Mollisols (Albolls: Argialbolls) Podzols Spodosols (Humods: Orthods), Entisols (Psamments: Spodic Udipsamment), Inceptisols (Udepts: Spodic Dystrudept) Weakly developed Entisols (Psamments: Udipsamments, Orthents: Udorthents) Anthrosols Semihydromorphic Gleyish Podzolic gleyish Alluvial Hydromorphic Lowland bog Transitional bog Upland bog Conclusion Entisols (Arents: Udarents), Inceptisols (Anthrepts: Haplanthrepts) Entisols (Aquents: Hydraquents, Psammaquents, Epiaquents, Endoaquents), Inceptisols (Aquepts: Humaquepts, Epiaquepts, Endoaquepts), Alfisols (Aqualfs: Albaqualfs, Epiaqualfs, Endoaqualfs), Mollisols (Aquolls: Argiaquolls, Epiaquolls, Endoaquolls) Alfisols (Aqualfs: Glossaqualfs), Spodosols (Aquods) Entisols (Fluvents: Udifluvents, Aquents: Fluvaquents) Histosols (Saprists: Haplosaprists) Histosols (Hemists: Luvihemists, Haplohemists) Histosols (Fibrists: Sphagnofibrists, Haplofibrists) Investigations show that due to the different approach used for soil grouping, there is not possible direct comparison of soil units between Latvia Soil classification system and WRB as well as Soil Taxonomy. For information harmonization, unification of diagnostic methods and soil profile description should be applied (introduction of FAO recommended methods in soil research and survey in Latvia) This will provide potential for direct definition of soil units according WRB or Soil Taxonomy and also ensure adequate information exchange. References Guidelines for soil description 3 rd edition / FAO. Rome, pp. Field book for describing and sampling / P.J. Schoeneberger, D.A. Wysocki., E.C. Benham, W.D. Broderson. Natural Resources Conservation Service, USDA, National Soil Survey Center, pp. Procedures for soil analysis // L.P. van Reeuwijk (ed) / 5 th ed. Wageningen: ISRIC, Soil Science // Ed by A. Karklins. Jelgava: LLU, pp. (In Latvian). World Reference Base for Soil Resources / World Soil Resources Reports No. 84. (1998). Rome: FAO. 88 pp. Lecture notes on the major of the world // Ed. by P. Driessen, J. Deckers, O. Spaargaren, F. Nachtergaele / World Soil Resources Reports No. 94. Rome: FAO. (2001). 334 pp. Keys to Soil Taxonomy / 8 th edition. United States Department of Agriculture, Natural Resources Conservation Service, pp. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys / 2 nd edition. United States Department of Agriculture, Natural Resources Conservation Service, pp. 204 A comparative study of the Latvian Soil Classification with WRB. Karklins.

Soil Reference Groups of WRB (and related diagnostic criteria)

Soil Reference Groups of WRB (and related diagnostic criteria) Discussion of Reference Groups will be based on the FAO World Soil Resources Report # 94 LECTURE NOTES ON THE MAJOR SOILS OF THE WORLD available