Catena Concept: Relation with Global Environment - Dissertation Example

RUNNUNG HEAD: CATENA CONCEPT Catena Concept: In Relation with Global Environment of Soils are an important part of the world ecology as the benefits obtained from them are uncountable. The various forms of soils have developed over the years on the surface of this Earth with combinations process involving broad amalgamations of chemical, biological and physical reactions. These processed can be broadly pronounced as the pedogenic processes as a number of pedogenic factors are involved. There are a number of approaches that have enabled experts to distinguish between various forms of soil. This discrimination was necessary in order to develop the soil maps of the great lands across the world, and of these approaches the Catena concept is probably the most prominent. This paper includes a detailed elucidation of the catena concept from its introduction to origins and the challenges it faced, and its applications around the world. Other important aspects in this context such as leaching, decalcification and calcification and podzolization have also been discussed. Catena Concept: In Relation with Global Environment Soils: Introduction Soils are known to be physical bodies and their formation takes place through a series of distinguished processes. Such processes continue to take place inside the body of soil or in its contour. These processes of soil formation are generally known as “pedogenic processes” and comprise various biological, chemical, and physical reactions. The location of the particular type of soil, ecosystem, and the broad environmental background determine the intensity and character f such reactions. (Hugget, 1976) World Reference Base (WRB) Classification of Soils An international system of soil correlation was developed and adopted by the IUSS the International Union of Soil Sciences in the year 1998 under the title WRB “World Reference Base for Soil Resources”. FAO/UNESCO soil map of the world has great influence over the definitions, structure, and concepts. Following figure clearly demonstrates the WRB soil classification. (Chesworth, 2008) Table 1: WRB Classification of Soils; Adopted from Deckers et al., (2002) Pedogenic Factors of Soil Formation The impact of such general environmental background is evidenced to be segregated into a number of factors controlling soil formation: Time; Relief; Climate; Parent material; Organisms either human beings or animals and plants. (Ruhe, 1969) Development of Soil Rocks are being acted upon through various processes of weathering and as a result of these processes soil parent materials which are also known as C horizon are produced. Such processes function in solum, that is, the soil formation zone for producing a soil profile it may be A, B, E and O horizons. These weathering processes of soil formation produce four main natural mechanisms, novel sesquioxides and resultant clay minerals, a defiant scum of minerals and is hard to split, a erode suspension of soluble chemicals, and organic matters. Such horizons are at times ambiguous and every so often obvious and apparent. This is caused by the strength, force and steadiness of the complete series of rearrangement and assimilation progression. It’s a practice around the world to employ various names for soils, different classifications and notations for soil by diverse companies conducting soil surveys and research. (Wood, 1942) Environment of Soil Formation It has already been discussed that soil formation is basically dependant on five pedogenic factors-time, relief, climate, parent material and organisms. As Conacher (1977) had mentioned, the nature of relief is important for soil formation as it determines the percolation of water into the soil, besides that it also affects the amount of erosion, and the accumulation and interchange of solids. Climatic conditions such as temperature, precipitation rate also affect soil formation. Parent materials affect the nature of soil as it is directly related to the mineral content of the soil, the particle size etc. Microbial organisms, as well as dead animal and human matter constitute an important part of soil, and their content determines the organic content of the soil. Calcification, decalcification and leaching Rainfall is the reason for leaching. It has a natural pH of 5.5 and hence is slightly acidic in nature (Smithson et al. 2002). Hence, as it “passes through the surface organic horizon, it dissolves organic acids from decomposing plant residues. It is thus able to dissolve and decompose minerals and carry away cations and anions dissolved in the soil solution” (Smithson et al. 2002, p.404). Thus, basically leaching is the process in which the soil loses it mineral content as a result of their dissolution in rain. This results in a lowering of the pH of the soil. Leaching is an important ecological process as this allows the mineral content to reach into the subsoil. However, this is a disadvantage for plants with short roots and hence leaching needs to be balanced by providing fertilizers. Leaching is especially important in formation of brown earth soils (such as Cambisols). They are formed by weathering of elements in the lower horizon and by leaching of elements in the upper horizon. Decalcification, as the name signifies, is the removal of “free calcium carbonate from soils by leaching” (Smithson et al. 2002, p. 405). This is common in humid areas. However, when the conditions are dry or partially dry then gypsum (CaSO4.2H2O) and calcium carbonate (CaCO3) get deposited in the soil. This process is called calcification. Pennock et al. (1987) mentioned that calcification is prominent in places where leaching is of a lower degree. Podzolization Podzol refers to a especial soil type which has “the pale surface horizon of eluviation (out-washing) overlying the blackish or orange horizon of illuviation (in-washing)” (Smithson et al. p. 406). Podzolization is basically the removal of aluminium and iron from the upper surface of soil and their percolation to deeper surface or the lower B area of soil. It is because of this percolation of iron that colour of B area is blackish or orange. Hydroquinones and polyphenols are responsible for this percolation of minerals. They are highly reactive compounds and are able to form iron complexes thus activating the iron and facilitating their downward movement. Catena Concept The concept of catena, as it is now known, was introduced by Geoffrey Milne, a Tanganyika-based soil chemist (Grunwald 2005, p. 77). Catena means chain and is a method of classification of soil based on the depth of the natural water table. Milne followed up on Martin’s idea by coining the term catena (chain) to characterize a regularly repeating soil-topography sequence. This idea was first circulated in a memo to the other soil chemists in early 1933, then published in a relatively obscure Soil Research paper. Milne proposed to two clearly distinct ideas: (1) the fasc (Latin for “bundle”) as a taxonomic grouping intermediate between the series and great soil groups, and (2) the catena concept as a “composite unit of mapping”. The catena name itself was “intended to serve as a mnemonic, the succession of different soils corresponding to the links in a hanging chain” in a progression from one hilltop to the next (Grunwald 2005, p 78). Milne later on further developed on the idea suggesting that catena can be classified into two categories. One is formed from a single type of parent rock while the other has a more complex formation, and the geology-topography relationship also affect soil-topography relationship (Grunwald, 2005). In addition, he suggested that soil variations are carried out by variations in the drainage system of the region amalgamated with some differentiating rearrangement of gnarled substance that is being amassed at the lower lands and levels of soil elements chemically leaked from higher slopes and lands (Birkeland, 1999). Milne’s new concept of catena brought a completely different dimension to soil-topography relationship which is today recognized as the landscape geochemistry, hill-slope hydrology and process geomorphology (Grunwald, 2005). He continued to discuss the impacts of deposition fluvial erosion on landscape formation, suggesting that if the addition and removal of materials was incremental and carried out simultaneously with other related soil forming progressions, the erosion should be regarded as a soil forming process rather than a geological evolution. For this he brought upon an investigational perspective to the project that was later proposed by Jenny in King (1953) with his factorial quantitative approach at the soil scale profile. While in 1930s and 1940s the soil expert didn’t acknowledge the dimensional process of catena, the work of Milne was broadly cited by Ruhe (1960) in his influential paper “Elements of the Soil Landscape” and stoutly contradicted the misrepresentation of the catena concept by the U.S. soil expert community (that is being discussed earlier). Ruhe further argued in his book, which was based on the factorial approach and soil geomorphology that it is not only the aspects that explicate the soil variations that are being integrated in the catena concept, but prominent focus has also been placed the past accounts of the pedogenic processes, surface of land, sediment transportations, geo-hydrology and erosion. (Ruhe, 1960) Milne also suggested that a catena refers to a land soil field unit similar to the perpendicular soil sketch, while the catena concept referred to a theoretical topography- soil association with the related development progressions (fig 1). Fig 1: Adopted from Grunwald (2006) The figure above describes the two dimensional model of a catena as per Geoffrey Milne’s approach, with various forms of soils that are being found at the various land points labeled by numbers from 1 to 7. Challenging the Zonal Soil Tradition The notion that spatial variability and soil formation could be associated to relief or topography was barely a unique aspect in 1930. In the late 19th century Dokuchaev and Sibirtsev presented the topography relationships. It was the case by the end of the 19th century that the Russian soil experts were using these relationships for the development of soil maps. Gilbert W. Robinson the British pedologist pointed out in his book that there are certain regions in Britain where comparatively uncomplicated topography and geology that result in far-reaching tracts of soil under homogeneous climatic conditions, if not essentially invariable in character demonstrate discrepancy which can be simply interrelated to topographical circumstances. It was by 1930s that it was broadly accepted that due to topographic changes soil also varies. And probably the most validating reason for the widespread acceptance of the catena concept was partly that the Milne introduced a very fascinating name for this fact. However, catena concept by Milne was also challenged by current notions regarding the soil-topography combinations. Milne’s catena concept has been also used to classify Scottish soil. The following table provides the classification of Scottish soil. Division Major Soil Group Major Soil Sub-Group Immature soils 1.1 Lithosols 1.1 undifferentiated lithosols 1.2 Regosols 1.2.1 calcareous regosols 1.2.2 non-calcareous regosols 1.3 Alluvial soils 1.3.1 saline alluvial soils 1.3.2 mineral alluvial soils 1.3.3 peaty alluvial soils 1.4 Rankers 1.4.1 brown rankers 1.4.2 podzolic rankers 1.4.3 gley rankers 1.4.4 peaty rankers Non-leached soils 2.1 Rendzinas 2.1.1 brown rendinzas 2.2 Calcareous soils 2.2.1 brown calcareous soils Leached soils 3.1 Magnesian soils 3.1.1 brown magnesian soils 3.2 Brown earths 3.2.1 brown earths 3.2.2 brown earths with gleying 3.3 Podzols 3.3.1 humus podzol 3.3.2 humus-iron podzol 3.3.3 iron podzol 3.3.4 peaty podzol 3.4 Montane soils 3.4.1 subalpine soils 3.4.2 alpine soils Gleys 4.1 Surface-water gleys 4.1.1 saline gleys 4.1.2 calcareous gleys 4.1.3 magnesian gleys 4.1.4 non-calcareous gleys 4.1.5 humic gleys 4.1.6 peaty gleys 4.2 Ground-water gleys 4.2.1 calcareous gleys 4.2.2 non-calcareous gleys 4.2.3 humic gleys 4.2.4 peaty gleys 4.2.5 subalpine gleys 4.2.6 alpine gleys Organic Soils 5.1 Peats 5.1.1 eutrophic flushed peat 5.1.2 mesotrophic flushed peat 5.1.3 dystrophic flushed peat 5.1.4 dystrophic peat Table 2. The Scottish Soil Classification; Adopted from Commissioned Report No. 111 by Scottish Natural Heritage (2005). The report (2005) mentions that alpine and subalpine soils are associated with the montane environment. Cambisols are found in the coastal areas of South-West Scotland. Podzols are common in the agricultural land of North-East Scotland. Non-calcareous gleys are widely distributed in Scotland. “Histosols are over-represented withing Scotland” (Commissioned Report No. 111, 2005 p. 14). Thus, the distribution of soil in Scotland has made use of the catena concept. Fig 2. The soil map of East Africa presented by Geoffrey Milne. It is important to note that the investigations that were left unfinished or were absent are being marked with blank or partially blank stripping. Adopted from Grunwald (2006) Soil Association vs. the Catena Concept According to Ruhe (1956) W.S. Martin partly contradicted the idea when the new term catena was proposed by Milne. It was because Martin thought that G.W. Robinson’s suite would do. What was proposed by Robinson referred to an amalgamated mapping and classification for a group of dissimilar soils that were formed from a single parent material. But Milne discarded the use of suite to be used in the East African mapping plan this was because he thought the use of the word may lead to ambiguity and confusion, moreover he believed that types of soils within a suite could differ due to a number of other reasons than topography only and also that the similar parent condition wasn’t met always in East Africa for a valid relationship between soil and topography. By 1938 was completely re-characterized in the U.S. as they described it as that all of the soils in a region originate from a same parent but they varied in terms of character of profile progression and relief, which was referred to as association in US. Unfortunately, the utility of catena as mappin concept was limited by this elucidation, as instead of relief it depended on other factors. Thus it can be said that the landscape formation and soil formation model given by Milne that go through the regional soil paradigm was manipulated as a limited drainage based, field classification procedure like the ones that were already used, leading am expert to term catena as macrocatena as the U.S term aptly . (Ruhe, 1956) Fig 3. The legend for the Soil Map of East Africa 1935, illustrating the graphical depiction for composite map elements. Adopted from Grunwald (2006) Applications of the Catena concept Soils and Men, the USDA yearbook 1938, incorporated an insignificant soil association map in representation of Milne’s catena. However, in map unit illustrations, the relations between soil and landscape were defined incompletely and were gathered from the current county soil inspection details in which soil associations weren’t included. One of the initial association diagrams analogous to the current ones was presented in the report published in 1954 at the Taylor Country, IA. The association ideology aided to direct field sampling, but increased instead of replacing the conventional detailed survey procedures. Fig 4. The 3D soil association block diagram, presented in the report published in 1954 at the Taylor Country, IA. Adopted from Grunwald (2006) The Australian soil experts, in the 1940s used the catena concept as an alternate to the detailed soil mapping, which enabled them to study large landscapes with inadequate funds. As the term association had been redefined by the U.S survey , the Australian soil experts used the term association instead of catena, the sense in which it was used it was quite similar. It was in 1950 that Kellogg suggested that tropical soils should be mapped as associations according to these lines. (Dan & Yaalon, 1964) In the year 1946, the very first ‘land systems’ study was conducted by Stewart and Christian simultaneously, with the maturity of soil association mapping in the Australian soil investigation. These examinations involved groups of scientists comprising of ecologists/botanists, pedologists and geologist. The investigations were meant to map up the joint vegetation, geological and soil relationships of the far reaching remote lands. The region that was intended was divided in smaller chunks with comparatively similar vegetation-soil-geology-topography relationships, and a graphical representation was developed to illustrate the associated relationships for the respective land systems. (Dan & Yaalon, 1964) Fig 5. Mullaman land systems diagram from the study of Darwin-Katherin in Australia. Adopted from Grunwald (2006) Clearly, these diagrams were similar Milne’s catena figures; however, the intention was to cover all of the physical pr topographical features i.e. geology, soils and vegetation not only the use of topography, vegetation and geology for illustrating soil maps. References Birkeland, P. W. (1999). Soils and Geomorphology. Oxford: Oxford University Press, p. 428-431. Chesworth, W. (2008). Encyclopedia of Soil Science. Springer, p. 122. Conacher, A. J., & Dalrymple, J. B. (1977). The Nine Unit Landscape Model: An Approach to Pedogeomorphic Research, Geoderma, Vol. 1, 1-154. Dan, J. & Yaalon, D. H. (1964). The Application of Catena Concept in Studies of Pedogenesis in Mediterranean and desert Fringe Regions. Trans., 8th International Congress, Soil Science, Vol. 5, 751-758. Deckers, J., Driessen, P., Nachtergaele, F., & Spaargaren, O. (2002). World Reference Base for Soil Resources-in a Nutshell. In Micheli, E. et al., eds. Soil Classification 2001. Luxemberg: Office for the Official Publications of the European Communities. European Soil Bureau. FAO. (1988). FAO/UNESCO Soil Map of the World. World Soil Resources Reports # 60. Grunwald, S. (2006). Environmental Soil-Landscape Modeling: Geographic Information. technologies and pedometrics. CRC Press, p. 77-79. Hugget, R. J. (1975). Soil Landscape Systems: A Model of Soil Genesis, Geoderma, Vol. 13, 1-22. King, L. C. (1953). Canons of Landscape Evolution. Geological Society of America Bulletin, Vol. 64, 721-752. Milne, G. (1936). Normal Erosion as a factor in Soil Profile Development. Nature, 138, 548. Pennock, D. J., Zebarth, F. J. 7 DeJong, E. (1987). Landform Classification and Soil distribution in Hummocky Terrain, Saskatchewan, Canada. Geoderma, Vol. 40, 297-315. Roth, C. B. (1997). Glossary of Soil Science Terms. Soil Science Society of America, p. 130-133. Ruhe, R. V. (1956). Geomorphic Surfaces and the Nature of Soils, Soil, Science, Vol. 82, 441-455. Ruhe, R. V. (1960). Elements of the Soil Landscape. Trans., 7th International Congress, Soil Science, Vol. 4, 165-170 Ruhe, R. V. (1969). Quarterly Landscapes in Iowa. Iowa State University Press, p. 250-54. Smithson, P. et al. (2002). Fundamentals of the Physical Environment. Taylor & Francis Ltd. Wood, A. (1942). The Development of Hillside Slopes. Geologists’ Association Proc, 53, 128-138. Read More