A Syllabus on Soil geomorphology (geopedology) In the framework of Landscape Ecology ============================================================== Contrary to what is sometimes thought geopedology is not only an imageinterpretation map, with a tabulated legend wherein map units are described in geomorphologic terms, or a well organized application of geomorphology to soil survey. Geopedology is a conceptual approach, which fortifies a scientific framework for soil resource inventory and its interpretation/ evaluation for various uses. In other words, it is a science and, at the same time, an art of modelling the occurrence of soils in landscape, a process which is based on (mental) integration of knowledge on climate, geology, geomorphology, sedimentalogy, hydrology, vegetation, and pedology. A geopedologic map is a soil map, which includes much facts and understanding about the landscape (Farshad et al., 2005a). Dr. Abbas Farshad Earth Systems Analysis Dept. ITC, Enschede The Netherlands [email protected] Aug. 2006 -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 1 List of content: A Few Definitions Introduction Soils on the landscape: Soil formation and development A. forming factors B. forming processes Soil material A. Organizational levels B. Properties C. describing soil profiles D. soil classification Soil resource inventory or soil survey 1. Introduction 2. Importance of geomorphology for soil survey 3. Implementing geomorphology in soil survey 4. Structure of the taxonomic system 5. The proposed system by Zinck (1988) Geoforms systematics Application of soils to physical and environmental studies How far are we with digital soil mapping -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 2 Definitions: Soil: The naturally occurring 3-D unconsolidated material on the earth’s crust that has been influenced by parent material, climate, macro and micro organisms, and relief, all acting over a period of time to produce soil that may differ from the material from which it was derived in many physical, chemical, mineralogical, biological, and morphological properties. Atmosphere: The air surrounding the earth, thickness of which is roughly put at 200km. Biosphere: The part of the earth where living organisms are found, and with which they interact to produce a steady-state system, effectively the whole planet ecosystem. Hydrosphere: The total body of water which exists on or close to the surface of the earth. Lithosphere: The upper layer of the solid earth, comprizing all crustal rocks and the brittle part of theuppermost mantle. Pedosphere: The envelope of the earth where soils occur and where soil-forming processes are active. Landscape: All the natural features that distinguish one part of the earth’s surface from another part. Usually, it is the portion of land or territory that the eye can see in a single view, including all its natural characteristics. Ecolology: Ecology refers to the study of living (microbes, plants, animals and humans) and non-living components (the physical environment) as a whole. The word ecology is stemmed from the Greek word meaning “house”. Landscape Ecology: The study of environmental factors and interactions at a scale that encompasses more than one ecosystem at a time. Introduction Soil is a complex 3-D object, the X and Y dimensions (its surface) of which can be observed, if not covered by vegetation and/or other objects, whereas the Z dimension (its depth) is not visible, hence quite difficult to describe and/or map it, in order to know its distribution, which is often required for (land use) planning purposes, and, in some cases, -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 3 for serving the needs of geomorphologists, environmental geologists, and archaeologists working in Quaternary research (Birkland, 1999). Considering the facts: - that soil is the product of the actions of climate, flora and fauna, and topography (relief) on rocks/ sediments in spans of time, the soil variability, both in lateral as well as vertical directions, has always been (and remains) a complex issue, and - that with the introduction of the physiographic (holistic) school, which was later on also fortified by (the use of) aerial photo-interpretation, the role of geomorphology was intensified, soon it became clear that the problem of variability can be, to a great extent, solved by applying geomorphology. Through mapping landform, which are also 3-D, we have actually map soils, as soil is an integral part of the landform. With this argument soil-landform relationships become important to soil surveyors. Whether we should use the term soil geomorphology in the same way as we use the terms soil structure, soil texture, soil pH, etc, may be questionable to some people. Does the soil have geomorphology, in its strict literal sense (see the definition)? Geomorphology (geo=earth, morph=shape and logy=survey) is a branch of geology dealing with the form of the earth, the general configuration of the earth surface, and the changes which take place, that is, parallel with the evolution of landforms. Let us for a while ask ourselves, once again, the question of “what are we actually looking for?” Isn’t geomorphology a tool to help us detect the third dimension of the soil? Would the terminology then be satisfactory? Or, “the application of geomorphology to soil science” (Gerrard, 1992) is a better terminology? What about when soils data are used by geomorphologists, environmental geologists, and all others who work in Quaternary geology, and other disciplines? Aren’t we all working for landscape? What is landscape, and what are the components of landscape ecology? (see also Huggett, 1995). As it is noticed, these notes started with the title “soil (land)scape study”!! we would come back to this, preferably at the end of the course, to listen to everyone’s suggestion on an appropriate title, i.e., one of the followings: - Soil geomorphology - Geopedology - Soils and geomorphology - Applied geomorphology to soil science - Physiography and soils - Soil (land)scape study; within the landscape ecology framework (IALE= http://www.crle.uoguelph.ca/iale/) Landscape ecology is the study of spatial variation in landscapes at a variety of scales. It includes the biophysical and societal causes and consequences of landscape heterogeneity. Above all, it is broadly interdisciplinary. The conceptual and theoretical core of landscape ecology links natural sciences with related human disciplines. Landscape ecology can be portrayed by several of its core themes: . the spatial pattern or structure of landscapes, ranging from wilderness to cities, -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 4 . the relationship between pattern and processes in landscapes, . the relationship of human activity to landscape pattern, process and change, . the effect of scale and disturbance on the landscape. Soils on the landscape Soils are dynamic, natural bodies in the landscape and evolve over time. The first stage of development is weathering (physical, chemical and biological) of bedrock to form unconsolidated rock fragments, the parent material. This is the bed where soil will form in, that is, the formation of horizons (known as horizonation). Horizonation is taken care of by pedogenic processes, whereas geogenic processes (e.g., sedimentation) are responsible for lateral variation. If, instead of rock, a thick layer of sediments is the parent material, soil formation is one step ahead, as there will be no need that the consolidated rock is first fragmented/weathered, converting into unconsolidated material (regolith/ saprolite). However, mineral stability (that is resistance to weathering) is the issue here (e.g., zircon> garnet> quartz> muscovite> feldspar> augite> biotite> volcanic glass>olivine). The concept of soil as a natural body integrating the accumulated effects of climate and vegetation acting on surficial materials was first introduced by Dokuchaev, in Russia, around 1870. The further development of the concept was followed by other Russian scietists and later on by Europeans such as Glinka (1914) and soon after used by Americans, who were involved in the development of soil classification (e.g., the one published in 1938). Knowing that soils cover the uppermost of the earth’s surface (composed of various types of rocks, sediments, etc), grading, with depth, into parent material (or rock) and into other soils laterally, a large diversity of soils can be expected on earth, which to a great extent, are controlled by landforms, considering the fact that the same forming factors (climate, vegetation, parent rock, etc) responsible in the formation of landforms, control also the formation of soils. Therefore, in order to solve a number of ecological, environmental, agricultural and forestry problems, an approach of using the relationships between pedons and landscapes (units) is highly desirable and effective. It would be appropriate to briefly look into what the soil, being composed of solid, liquid, air and water, does for us : • Soil provides a physical matrix, chemical environment, and biological setting for water, nutrient, air, and heat exchange for living organisms. • Soil controls the distribution of rainfall or irrigation water to runoff, infiltration, storage, or deep drainage. Its regulation of water flow affects the movement of soluble materials, such as nitrate, nitrogen or pesticides. • Soil regulates biological activity and molecular exchanges among solid, liquid, and gaseous phases. This affects nutrient cycling, plant growth, and decomposition of organic materials. -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 5 • • • Soil acts as a filter to protect the quality of water, air, and other resources. Soil provides mechanical support for living organisms and their structures. People and wildlife depend on this function. Soil is the history book of the landscape (see the attached article on climate change) Soil formation and development A. Soil forming factors: In an undisturbed ecosystem, the following factors play a role in the formation of soils: climate ( C ), vegetation (V), topography or relief (R), parent material (P), and organisms (O), over a period of time (T) This is what Jenny (1941) stated in the following equation, already in 1941: S= f (C,V, O, R, P, T,…) (This section will be explained in detail, consulting the text on http://www. pedosphere.com) B. Soil forming processes: A soil forming process is a complex or sequence of reactions and recognization of matter occurring under the control of a contination of soil forming factors and leading to a given arrangement of soil material in a profile (Zinck, 1988). In a simplified soil forming model, a soil is considered as an open system on which four main types of processes act: a. Additions to a soil body: - heat from solar radiation - water from rainfall and/or groundwater - organic matter from vegetation of fertilization - sediments from flooding - soluble compounds from flooding or fertilization b. - Losses from a soil body: heat to the atmosphere water by runoff, hypodermic flow and/or deep percolation to groundwater organic and mineral materials by erosion soluble compounds by erosion and deep leeching c. - Transformation of material within a soil body: decomposition of organic matter weathering of primary minerals neoformation of clay minerals formation of clay compounds, concentrations and cementations -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 6 - formation of soil structure by biological construction or physico- chemical partition d. Translocation within a soil body: - downwards migration (illuviation) of clay, salts, carbonates, organic matter, sesquioxides - upwards migration of salts - lateral migration of soluble compounds. Buol et al (1980) give a list of processes, a few of which are copied here: - Eluviation: Movement of material out of a portion of a soil profle as in an albic (e.g., in Spodosols) horizon - Illuviation: Movement of material into a portion of soil profile as in an argillic (e.g., in Alfisols) horizon - Salinization: The accumulation of soluble salts such as sulfates and chlorides of calcium, magnesium, sodium, and potassium in salty (salic) horizons - Podzolization: The chemical migration of aluminium and iron and/or organic matter, resulting in the concentration of silica in the layer eluviated - Etc (please refer to Buol et al, 1980) In short, once the soil material (regolith) is settled, soil forming processes (additions, losses, translocation, and transformation) will start acting. Though, very difficult to say about the type of the process, which would act, depending on the intensity and on the dominant role of the soil forming factor (e.g., lithofunctional, topofunctional, etc) one or several process(es) will act to further develop the soil. Soil material A- Organizational levels (Zinck, 1988): 1.Nanolevel.… (elements, molecules, particles) 2.Microlevel… (soil aggregates) 3.Mesolevel... .(soil horizon) 4.Macrolevel... (pedon) 5.Megalevel….(polypedon) A.Farshad,ITC 1. Nanolevel: -units of measurement: nm, µm (and mm) -nature of material : elements, molecules, particles -means of observation : electron microscope, X-ray diffraction -nanolevel is the level of basic soil material reactions, which can be either : -chemical, -Physico-chemical, or -micro-mechanical • Chemical reaction can be by solubility, where chemical compounds change: -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 7 -Solution (salts) : -Carbonation (carbonates): -Hydrolysis (silicates): NaCl + H 2 O --- H 2 O + Na + Cl CO 2 + H 2 O --- H CO 3 + H Ca CO 3 + (H CO 3 + H)--- Ca (HCO 3 ) 2 KAl Si 3 O 8 + HOH--- HAl Si 3 O 8 + KOH Chemical reaction can also lead to changes of the structure of minerals (oxides), such as in the following processes: -Hydration -Oxidation and reduction • Physico-chemical reactions: when clay and organic matter take care of forming good soil aggregation (resistance to erosion); or different cations exchanging at the clay particle edge, that is, cation exchange capacity (fertility) Farshad,ITC • Micro-mechanics - Packing types (for sand and coarse silt grains) - Fabric types (for clay and fine silt) * Defloculated (risk of mudflow) * Dispersed (risk of solifluction) * Aggregated (risk of landslide) * Flocculated (soil stability) 2. Microlevel : That is at the aggregate level, where micromorphologic (by means of petrographic microscope) study are involved (Brewer, 1994; Bullock et al., 1985). - S- matrix . Solid material : structural stability resistance to erosion . Pore space : porosity water + air * microporosity WHC * macroporosity -infiltration * runoff * percolation - Pedologic features: soil genesis 3. Mesolevel: At the level of horizon, formed by aggregates coming together. For horizon designation and further explanation on the description of horizons we will use the FAO guidelines (see describing soil profiles). 4. Macrolevel: That is the level of pedon, the smallest soil unit that we study. The best references to refer to are: Buol et al., 1980; USDA, 1975, and the pedosphere on line (Juma, 1999: pedosphere on line). 5. Megalevel: -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 8 That is the polypedon level, with the units of measurement of meter to kilometers. We make use of Buol et al., 1980, and the pedoshere on line, for further explanation. Normally, a soil is born with the formation of a A-horizon (that is an AC profile, one of the members of the Entisols). Further development, leads to the formation of a B-horizon (that is then an ABC profile, which may corrspond with the formation of a Cambic diagnostic horizon, the simplest classification name may be one of the members of the Inceptisols). Further development will lead to the formation of argillic (Bt), Spodic (Bsh), Oxic horizons, etc, meaning Alfisols, Ultisols, Spodosols, Oxisols, respectively. B. Soil properties (http://www.pedosphere.com; USDA Soil Survey Manual; FAO Guidelines for Soil Profile Description; also under http://nesoil.com/properties/index.htm and www.nrcs.usda.gov/programs Physically, a mineral soil is a porous mixture of inorganic particles (fine and coarse fractions), decaying organic matter, air, and water. The larger mineral fragments usually are embedded in and coated over with colloidal and other materials. Organic matter acts as a binding agent, taking care of aggregating. This complex is the source of many physical characteristics, which may be explained in two sections, namely texture and structure. Other related properties, such as consistency, porosity, bulk density, permeability, infiltration, moisture content, and many others can be explained within the frame of, and relating to, the above sections: Texture: concerned with the size and the proportionality of mineral particles of various sizes (sand, silt and clay) in a given soil. Many ( physical and/or physico- chemical) soil properties and characteristics, such as water holding capacity, fertility, and workability can be explained referring to the soil texture (also referred to as particle size distribution; see the above mentioned sources ; among others “pedosphere” online). Structure: concerned with a bonding together into aggregates of individual soil particles. Individual soil aggregates (peds) are classified into several types (see pedosphere on line). The role of structure is very vital in many soil-oriented issues, such as water movement (infiltration, permeability, run- off) erosion, sedimentation, etc. C. Describing soil profiles: Soil survey is associated with a laborious fieldwork. Many soil observations (mini-pits, pits and augerings) are made and studied. Soil profile description is explained in Soil Survey Manual (USDA, 1990), but the pocket size guidelines we normally have with us in the field is the one of FAO (1990). The pit is first carefully studied for its different horizons and layers (H, A, E, B, C, R) and then described horizon by horizon, for colour, texture, structure, etc. The description card is filled out and kept in a file for later processing (the procedure will be demonstrated in a field excursion) -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 9 Texture: Soil texture is determined in the field, simply by making paste and testing it for stickiness (presence of clay), grittiness (presence of sand), and being or not soapy (presence of a certain amount of silt). Obviously, all soil samples contain sand, silt and clay. The question to ask yourself in the field is whether the sample in your hand is loamy sand; loam; clay loam; or clay. If the sample is sticky and that you can manipulate it to form long ribbon (by rubbing between your fore-finger and thumb of, preferably, your left hand, in order to have your right hand clean for writing, etc), it is clay. Ribbons are also formed if the sample is clay loam, with the difference that here the ribbon is bending down around your fore-finger. In addition the soil is not so sticky as in the case of clay. With loam one cannot form ribbon. A very striking characteristic of loam is that the soil paste feels very soft and smooth. Any of these textures (clay, clay loam, loam) can have more than a given amount of sand (see the USDA Textural Triangle) in which case the adjective “sandy” will be added to the name, that is, sandy clay, sandy clay loam, and sandy loam, respectively. If there is too much sand in “loam” so far that no ball can be formed, then we would have “loamy sand”. If one hesitates between the two (sandy loam and loamy sand) make then a ball from the paste and throw it up for about 50cm and catch it back in the hand. If soil sample stays as a ball it is sandy loam but if it collapses it is “loamy sand”. The texture classes loam, clay loam, and clay may be silty, that is, when silt percentage is more that a certain amount (see the USDA Textural Triangle). Then we will have silt loam, silty clay loam, and silty clay, respectively. In field, a few drops of water is added to the soil sample and gently rubbed with the thumb in order to check whether the soil feels soapy or not. If soapy, it is then silty. The tests mentioned above are some general hints which help determining texture, but it is very important to check these feelings with the laboratory, and/or with a senior soil surveyor. This is specially important when you go to a new study area. Obviously, one cannot expect that young soils, old soils, volcanic soils, soils with kaolinite clay type will react similarly when manipulating for texture. Structure: When a soil (in the profile pit) does not show rock structure, we say there is soil structure. One of the requirements of the Cambic horizon (a diagnostic horizon defined in soil classification systems, USDA , FAO, or WRB) is to show more than 50% of soil structure. A very weathered gneiss (saprolite) will still show bands of the weathered felsic and mafic minerals, in which case decision should be taken whether rock structure is more or less than 50%. Once we agree that we do not see rock structure we then have to do with soil structure. Soils may be structured or without structure (structureless). The term structureless is rather confusing. If there is no clear aggregate to recognize and the soil material is coherent we speak of massive, but if non-coherent we speak of single grained. These are considered soil structure, although we used the term “structureless” (USAD Soil Survey Manual). On the other hand, if aggregates have been formed they may be of plate-like, block-like, and prism-like forms. Hereunder, we will have granular; crumb; fine through course, weak to strongly developed subangular to angular blocky (subdivisions of the block-like); fine through course, weak to strongly developed prismatic; or columnar, which occurs -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 10 only in Natric horizons( both prismatic and columnar are different types of the prismlike); and thin through thick, fine through course platy structure type. As you probably noticed, structure is described according to its form, size and the degree of development. There is not any difficulty to learn about the form and the size, but to determine the degree of development one needs to see how a senior soil surveyor is doing. Use the hand-grip of you knife to gently hit a clod of soil that you hold in the hand and watch how the clod breaks into smaller pieces (aggregates). The easier the clod breaks into smaller peds the better the structure is. The clod breaks along the developed planes of weakness (between structural elements). A strongly developed structure won’t leave behind any wastes, that is, all broken pieces will be smaller structural elements. In massive soils, no planes of weakness are developed. Breaking of the clod, in this case, would only be possible by force. D. Soil Classification: As in many other disciplines, in soil science too, classifiaction is to help communication. Similar soils are tried to put in given groups so that their correlation (of soils occurring in the different parts of the world) become possible. Among the many classification systems, the USDA Soil Taxonomy (USDA, 1975 and the later issues) is considered as the most comprehensive, although many scientists look for an easier and more simple system. The FAO-Unesco (in the 1970s) system and the more developed version of it, the World Soil Reference Base (FAO-ISRIC reports 66 rev. 1, 1993 and 84 in 1998) are some attempts to present a more simple soil classification. Personally, I am inclined to work with a real organized and comprehensive system of soil classification, through which well qualified useful interpretations can be done. I strongly believe that not all users of soil maps are not supposed with the sophisticated classification anmes. There, we have soil scientists for!! In the USDA Soil Taxonomy, several categorical levels, such as ‘orders’, ‘suborders’, ‘great groups’, ‘subgroup’, ‘family’, and phases of family take care of the classification. Example: All soils belonging to Alfisols (order name) will end with ‘alf’. Alfisols are defined, using several criteria, for instance, having an argillic horizon, characterized by a base saturation (BS%), at the depth of almost 2m from soil surface, of 35%, etc. Xeralfs (suborder name) are those alfisols which, in first place, occur in the areas with Xeric moisture regime (e.g., in a country like a great part of Spain, or Portugal, with mediterranean type of climate). Palexeralfs (a ‘great group’ name) are the Xeralfs with a thick argillic horizon, sign of development and age. Calcic Palexeralfs (a subgroup name) are those palexeralfs which also have a calcic horizon. After subgroup, appears the family name, which is formulated on the basis of family differentiae, such as particle size class, mineralogy class, soil temperature classes, etc. An example to be given here is: Clayey skeletal, illitic, hyperthermic. -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 11 We recommend to continue the classification, at least in surveys at semi-detailed level, to the phase of family, that is, to use terms such as very gravelly topsoil, strongly sloping, etc (see Soil Survey Manual; USDA, 1990). Soil resource inventory or simply soil survey 1. Introduction: As already mentioned, soil is a complex 3-D object, the X and Y dimensions (its surface) of which can be observed, if not covered by vegetation and/or other objects, whereas the Z dimension (its depth) is not visible, hence quite difficult to describe and/or map it, in order to know its distribution, which is often required for (land use) planning and other purposes. Soil survey is a complex operation, including a number of tasks in categorical levels (Zinck, 1988). The strict domain of soil survey includes the phase of basic soil data collection, synthesis of soil information, characterization of soils and environment, and the multiple purpose soil interpretation. Zinck (1988) also considers two more levels, where soil survey is employed in planning, at regional and local levels. An obvious question in soil survey is how to map an object which owes its extent to the variations of its forming factors in space and time, as the soil is the product of the actions of climate, biota, and topography (relief) on rocks/ sediments in spans of time? What tool should we use to extract information about the 3rd dimension, the depth? After rather a long time of trying various ways such as grid survey, overlaying (synthetic approach), etc. geomorphology proved to be the best tool. 2. Importance of geomorphology for soil survey In order to discuss the importance of geomorphology for soil survey, it is sufficient to check whether we agree with the following statements: - Pedology and geomorphology are two of the fundamental disciplines within the landscape ecology (IALE concept= http://www.Crle.uoguelph.ca.iale). - Pedons and geoforms are the study objects of these disciplines, respectively. - Both pedons (USDA, 1975) and geoforms (Zinck, 1988) are natural bodies, occurring between lithosphere and atmosphere, including the biosphere, mainly above the lithosphere. - Both geoforms and soils share the same forming factors, originated from endogeneous or internal (material and energy) and exogeneous or external ( through climate, biosphere, erosion and sedimentation) sources: Internal geodynamics (energy), through faulting, folding (in general, tectonics) and volcanism govern the formation of material on which geoforms are formed. -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 12 In its turn, the material, depending on its lithology (texture, structure, mineralogy), tectonic layout, and age, controls the formation of the geoforms. On the other hand, external sources, through climate, biosphere, erosion, sedimentation, largely contribute to the formation, transformation and/or destruction of the geoforms and soils. - Geomorphology contributes to two activities within the complex process of soil survey, namely to 1. soil mapping, and 2. soil formation In soil mapping, two questions are to be answered, namely: 1- who they are? meaning that their address (site selection) should be known, their characteristics, and the category where they fall under (soil classification), and 2- where they are? meaning that their distribution and extension should be known. On top of all what is said above, geomorphologic processes and environment are used as factors and framework of soil formation and evolution: 1- geomorpic process associated with lateral movement is not useful only on sloping areas where catena formation, truncated/buried sequence are resulted, but also on flat areas, for instance, in the case of levee-basin sequence, in fluvial landscapes, 2- geomorphic process also indicates the time factor (morpho-chronology), through which the degree of soil development is estimated. In summary, incorporating geomorphology in various steps of the soil survey operation adds useful information. 3. Iimplementing geomorphology in soil survey Different ways of using geomorphology for soil survey have been tried out, a few examples of which can be given here (Zinck, 1988): - Terrain analysis (ITC approach explained in van Zuidam, 1985) - Physiographic approach of CIAF-ITC (in Colombia), and of CSIRO (Autralia) - Landtype approach (ITC Soil Division approach, which started under Buringh, further developed under Vink, Bennema and Goosen) - SOTER legend (FAO, 1993): developed at ISRIC, Wageningen, The Netherlands (in the time of W. Sombroek, as the director). This is an universal legend for a world soils and terrain digital database, to be used at scale 1000.000. These and many other approaches (explained in Zinck, 1988) aim mainly at the establishment of mapping legends adapted to local or regional conditions. In general, a solid structure is lacking. This holds true even in those of the approaches which are called to be categorical. The lack of structure is sometimes so large that ‘mountain’ and ‘basin’ are put in one and the same categorical level. Obviously, all authors have tried to follow a sort of structure, but it does not seem that they were successful. The problem is that geomorphology is quite a controversial subject and that a real taxonomic classification is lacking, whereas some other disciplines such as botany and soils have succeeded to establish one. -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 13 4. Structure of a taxonomic system Geomorphologists have always been concerned by classification. In a few examples given (Zinck, 1988), one can see that different authors have used different criteria, which have been changing over time. Examples of geomorphic classification: a. Tricart-Cailleux , the authors of ‘morphometric classification’ used size and structural geomorphology to classify geoforms, b. In genetic classification, the authors used structural geomorphology (types of relief such as cuesta, folded relief), climatic geomorphology (types of molding such as glacial molding, aeolian molding), and azonal geomorphology (alluvial forms, lacustrine forms, coastal forms), c. In genetic-choronologic classification, on the basis of a subdivision of the earth’s surface into broad climatic zones, a set of morpho-climatic domains and associated geoforms was resulted and used to do the classification. Considering that our knowledge on how to establish a taxonomic system has considerably improved (USDA, 1975), the above classification systems look far from satisfactory. By now, we have learnt that: -dimension can not be considered as a diagnostic criterion, -geographical distribution of geoforms should not be taken as a criterion, -choronology of geoforms should be included in the legend, not as a criterion, -the genesis of geoforms should be taken only at lower levels of the system, that is to say that a taxonomic system starts with simple criteria and ending with more complicated ones. The criteria, for which much data are needed might be used but only at lower categories. Obviously, lack of clear definitions and the conflicting views amongst the geomorphologists, regarding terminology, genesis, and so on are a few of the limitations to name here. The objective of a taxonomic system in geomorphology would be to taxonomically classify the geomorphic unit, that is, the geoforms. Such a system should aim at classifying geoforms by the characteristics and not by forming factors. To establish a taxonomic system, 5 main steps will have to be followed: 1. selection of the most appropriate system structure. A selection can be made out of a)hierarchical; b) relational; c) network; and d) lineal system structure. In the system of Zinck (1988), following the USDA Soil Taxonomy (1975), hierarchical structure is considered as the most appropriate one for the multi-categorical system, as the geoform is. 2. Definition and number of categories (these are further subdivisions of the system). A category is a level of abstration. Each category may have one or more class(es). Further, come the taxa. Each taxon is a member of an established class. 3. Definition and number of classes -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 14 4. selection and hierarchization of attributes (these are characteristics used for defining limits of classes) 5. Nomenclature for naming categories and classes Example -- Principles and mechanism of classification: Figure 1: showing the population of objects, in two different colours and 2 sizes Table 1: showing 3 critera and a few varieties of each one Attributes Attributes states Colour Red Green Size Large Small Form Square Triangle Circle Square Yel. Small Triangle Circle Large Green Small Figure 2: showing one way of classifying the objects. You will realize that there six possibilities -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 15 Examples from the USDA Soil Taxonomy: At order level: Ultisols | 0 Alfisols 35% 100% BS At suborder level: Dystropepts 0 | Eutropepets 50 100% BS Examples of categories in the USDA Soil Taxonomy: • • • • • Order (e.g., Inceptisols, Alfisols, Ultisols) Suborder (e.g., Eutropepts, Dystropepts) Great group Subgroup Family A few questions/remarks: will you answer the first question (write your answers down): Ouestion 1: At what level (in a multi-categorical classification system, like the one of the above exampl) would you think the following geomorphic forms should be placed? - Mountain; - Hill; - Alluvial fan; - Levee; - Summit Question 2: What do we see from ?: (answers are given in between the brackets) Satellite? (Large portion of a continent), Airplane? (Mountain range) Helicopter? (Structural/ erosional environment) Car? (Terrace) While walking ? (Levee/ basin) Question 3: What do you think about the following geomorphic terms to use to answer the above questions (of question 2): -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 16 Satellite? Geostructure Airplane? Morphogenetic environment Helicopter? Landscape Car? Relief-type While walking? Landform 5. The proposed system by Zinck (1988) Six categorical levels are considered as follows: 6- geostructure (order) 5- morphogenetic environment (suborder) 4- landscape (group) 3- relief/molding (subgroup) 2- lithology/facies (family) 1- landform (subfamily) Geostructure: Definition: Large continental portion characterized by a specific geological structure Taxa: - Cordillera: system of young mountain ranges - Shield: relatively stable continental block - Geosyncline: large sedimentary basin Morphogenetic environment: Definition: Broad type of biophysical medium Taxa (on the basis of various environments): - Structural : controlled by internal geodynamics; - Depositional (carried by water, ice, wind) ; - Erosional (denudatioanl); - Dissolutional (e.g., karst); - Residual(e.g., inselberg) - Mixed (e.g., structural dissected by erosion) Landscape: Definition: Large portion of land characterized either by a repetition of similar relief-types or an association of dissimilar types. Taxa: Valley; Plain; Peneplain; Plateau; Piedmont; Hilland and Mountain. Be aware that in some cases the concept of landscape is quite ambiguous, for instance, when we talk about valley!! -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 17 Relief-type/molding: Definition: Relief-type: geoform determined by a given combination of topography and geological structure (e.g., cuesta relief-type), Molding: geoform determined by specific morphoclimatic conditions or morphogenetic processes (e.g., glacis, fan, terrace, delta) Taxa: Structural Depression Mesa Cuesta Creston Hogback Bar Flatiron Escarpment Graben Horst Anticline Etc. Erosional Depression Vale Canyon Glacis Mesa Hill Crest Etc. Depositional Depression Swale Floodplain Flat Terrace Mesa Etc. Dissolutional Depression Dome Tower Hill Polje Canyon Dry vale Etc. Residual Planation surface Dome Inselberg Tors Etc. Lithology (See also Farshad, 2005. A Syllabus on “Introduction to applied geomorphology for soil scientistd (geopedologists): Definition: Lithology refers to the petrographic nature of the hard rock and the facies of the soft cover formations. Taxa: -Rock classes -Material facies, such as glacial, periglacial, alluvial, colluvial, litoral or coastal, mass movement, volcanic, mixed, anthropic, etc. Landform: Definition: Landform is considered here as the generic concept for the lowest level of the proposed hierarchical system. Landform=topographic form+geomorphic position+geoch-ronologic unit= soil formation frame. Taxa: See next chapter (e.g., summit, shoulder, overflow basin) -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 18 Attributes for determining geomorphic taxa: Attributes are characteristics used for description, identification and classification of geoforms. To establish a system we will have to decide on: - what attributes to be used for describing and identifying geoforms? and - what attributes for each categorical level? Classes of attributes 1- Morphographic: for describing the geometry of geoforms 2- Morphometric : for measuring the geoforms (DEM is useful) 3- Morphogenetic: for determining the origin and evolution of geoforms 4- Morphochronologic: circumscribing time context 1. Morphographic attributes a. Topography (transverse section of a portion of land): *Shape (e.g., flat, undulating, rolling, hilly, steeply dissected, mountainous) *Form (e.g., level, concave, convex,irregular) *Exposure (e.g., S., N.) b. Planimetry (vertical projection of geoform boundaries on a horizontal plane) *Configuration (e.g., elongated, narrow, rounded) *Contour design (e.g., arched, lobulate, irregular) *Drainage pattern(dendritic, annular, radial) *Surrounding conditions (e.g., overtopped by…..) *Bordering unit (e.g., plain overtopped by a plateau) 2. Morphometric attributes Morphometry refers to quantitative features of geoforms: a. relative altitude (e.g., high, medium, low) b. valley density (drainage density) c. slope gradient (in %) These are no-diagnostic attributes, which can be used at any categorical level with variable weight. DEM is an useful instrument. 3. Morphogenetic attributes a. Particle size distribution; very important attribute, because it: *allows inference of other material properties (e.g., bulk density) *reflects geo- and pedodynamic features b. structure (geogenetic structure, pedogenetic structure) c. consistence (mechanical behaviour) -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 19 d. mineralogy (origin of depositional material, morphoclimatic conditions, catena model, morphoscopy) 4. Morphochronologic attributes Properties used to study the history of geoforms: a. Degree of activity (sand dunes, solifluction, coastal bar) b. Age of geoforms: *absolute dating (e.g., radiometric techniques) *relative dating c. quaternary geology; use of reference systems (e.g., European and American glaciation-dating: Riss, Illinois, etc) d. pedostratigraphy: where soil properties (e.g., colour, pH, CEC, leaching indices) are used to estimate the relative age. Differential importance of the attributes; weight and level: Concerning the importance of the attributes for classifying geoforms, 3 classes are distinguished: 1. differentiating attributes: A slope facet must be concave to be classified as footslope. The topographic profile (concavity) is a differentiating attribute, 2. Accessory attributes reinforce the differentiating ones, such as the occurrence of depositional lens in footslope deposites, 3. Accidental attributes are used to create phases of taxonomic units, such as height and slope. At the same time, there are a few rules applied to the use of the attributes in the different levels in such a hierarchical system: - Less attributes are needed at higher levels, - Attributes at higher levels are descriptive, - Attributes at higher levels have an aggregating function - Implementation of attributes at higher levels is by means of API or visual interpretation of satellite image, whereas at the lower levels field and laboratory data are needed Geoforms systematics (see also Farshad, 2005b) A. Geoforms mainly controlled by geological structure: 1. Structural geoforms 2. Volcanic geoforms Relief types Landform types Depression Crater Caldera Maar Lake Ash Cone Slope facet complex Cinder Cone Crater -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 20 Spatter Cone Shield Volcano (Hawaian) Strato Volcano Cumulo Volcano Flat Mesa Cuesta Hogback Bar Dyke Escarpment Flanks Lava flow Block (aa) lava Ropy (Pahoehoe) lava Fluvio-volcanic flow (Lahar) Cinder field Ash mantle Planeze Hanging lava flow Sill Longitudinal dyke Annular dyke (ring dyke) Volcano scarp Neck Volcanic plug 3. Karstic geoforms B. Geoforms mainly controlled by morphogenetic agants: The six main families of landforms falling under this group are: 1. Nival, glacial and preglacial; 2. Eolian; 3. Alluvial and colluvial Erosional: Depositional: Ablation surface Load excess facies: Rill Point bar complex Gully River levee Gully complex (badlands) Distributary levee Deltaic levee Splay axis Splay mantle Crevasse splay Splay fan Splay glacis Overflow facies: Overflow mantle Overflow basin Decantation facies: Decantation basin Backswamp Ox-bow lake Infilled channel Colluvial facies: Colluvial fan Colluvial glacis -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 21 2. Lacustrine 3. Gravity and mass movement 4. Coastal C. Banal geoforms (dissected hills and ridges) D. Fluvial landforms and depositional systems Application of soils to physical and environmental studies Birkeland (1999) in his book titled “Soils nd Geomorphology” has a chapter on application of soils to geomorphological, sedimentalogical, and environmental studies, where he refers to many case studies where soils have been, as a basic science, applied to other disciplines. Examples are; use of soils in Quternary stratigraphic studies, using soils to date tectonic activity (e.g., dating faults and folds), using soils in archaeological studies, using soils in environmental studies, etc. This chapter of the above book supports the statement that soil is the history book of landscape, on the basis of which I have published a few papers. The two enclosed papers show examples of the use of soil in other disciplines: How far are we with digital soil mapping A digital terrain model is a mathematical (or digital) model of the terrain surface (Li et al, 2005). The mathematics takes care of the interpolation process, which has been advanced with increasingly efficient and cheap computation power and storage, availability of digital contour, stream, and orthophotographic data (http:\\ www.ffp.csiro.au/nfm/mdp/softdem.htm). Li et al. (2005) classify the surface modeling approaches as: 1. point-based modeling, 2. triangle-based modeling, 3. grid-based modeling and 4. a hybrid approach combining any of two of the three approaches. The required data for the digital terrain modeling may come either from field survey (eg., use of conventional surveying instrument or GPS), from stereo pairs of aerial (or space) images using photogrammetric techniques, or from digitization of the existing topographic maps. The latter source is the most commonly used technique, although more and more people make use of the freely available DEM’s, downable from SRTM (Shuttle Radar Topography Mission) at http://srtm.usgs.gov/. However, this product won’t satisfy those who need high resolution data (Farshad et al., 2005). Almost all well known commercial GIS packages are equipped with a submodule taking care of generating DTM. ARCINFO, for instance, is equipped with ANUDEM, a program developed in the Centre of Resource and Environmental Sciences of the Australian National University in Canberra, which supports production of grid-based DEMs using contourline map. Or in ENVI software, the submodule “topography” supports generating DTM using ASTER images. GRASS GIS software is also equipped with a number of terrain analysis procedures, especially for hydrological modeling and erosion mapping. There are also a few freely available packages, such as TARDEM and -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 22 TauDEM developed at the Utah Water Research Laboratory http://www.itc.nl/personal/shrestha/DTA/DTA_in_ILWIS.pdf. The process of inventory/ mapping includes collecting data (usually from points) and storing them with their geographic (spatial) properties, which can be used to track down distribution (map presentation). The advances in the world of remote sensing are considerable. Combined use of both remote sensing and GPS enormously facilitate the process of data collection/ fieldwork. However, remotely sensed data, whatsoever the sensor, usually depict the land surface. This means that much information can be extracted from the remotely sensed data if flora, and to a certain extent, fauna are the study subject. In the same way, the advancement in the domain of data base management system (DBMS), both spatial and non-spatial, in a GIS environment is striking. Data are easily stored and are retrievable in point, vector and/or raster, when required. Comparing these, which have been developed in the last couple of decades, with the ink-on-paper approach shows the extent of advancement. The once well formulated set of soil survey procedures, which, to many people, looked as if soil survey was a routine activity, is agitated. The newly developed technology in the field of data acquisition and management is taking over the once known conventional approaches, though still in a shaky conditions. The tendency is to go digital, quantification should overcome qualification. While still soil surveys are being carried out, though not as often as it used to be, several questions are asked by many people involved, simply because soil survey has become too expensive. Some of the questions are: What about the soil surveyors who have been trained to document their mental models in maps and reports. Didn’t this group do a good job? And was the soil map a good communication tool (Hudson, 1992)? Should this group continue what they did for decades? On the other hand, we should confess that it is a fact that soil mapping has benefited from the newly developed technology in the fields of exert system, decision support system, etc (Hengl et al, 2002, Bui and Moran, 2001 and 2003; Moran and Bui, 2002; Bui, 2004). However, the field has not sufficiently used the advances in remote sensing and mathematical modeling. The latter tools have been used, often at research level. References: Birkland, P.W. 1990. Soils and geomorphology (3rd edition). Oxford University Press, Inc., New York (http://www.oup-usa.org.). Brewer, R. 1964. Fabric and mineral analysis of soils. John Willey& Sons, New York, 407p. Bullock, P., Federoff, N, Jongerius, A., Stoops, G., and U. Babel. 1985. handbook for soil thin section description. Waine Research Publ., Wolver Hampton, England, 152p. -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 23 Bui, E.N. 2004. Soil survey as a knowledge system. Geoderma 120. p 17-26. Available online at www.sciencedirect.com. Bui, E.N. and C. J. Moran. 2001. Disaggregation of polygons of surficial geology and soil maps using spatial modeling and legacy data. Geoderma 103, 79-94. www.elsevier.com/locate/geoderma. Bui, E.N. and C. J. Moran. 2003. A strategy to fill gaps in soil survey over large spatial extents: an example from the Murray-Darling basin of Australia. Geoderma 111, 21-44. Available on line at www. sciencedirect.com. Buol, S.W., Hole, F.D. and R.J. Mc Cracken. 1980. Soil genesis and classification. Iowa State University Press, Ames, 404p. FAO, 1990. Guidelines for soil profile description. FAO, Rome, Italy FAO-ISRIC, 1993. Global and National Soils and Terrain Digital Databases (SOTER). World Soil Resources Report No. 74. FAO, Rome, Italy. 122p. FAO. 1998. World Reference Base for Soil Resources, Reports, FAO, Rome, Italy. Farshad, A., Udomsri, S., Yadav, R.D., Shrestha, D. P. and S. Sukchan. 2005a. Understanding geopedologic setting is a clue for improving the management of salt-affected soils in Non Suang district, Nakhon Ratchasima, Thailand. Presented in HinHua, Thailand, in wrap up seminar of the LDD-ITC funded research project. Farshad, A. 2005. An introduction to applied geomorphology for soil scientists (geopedologists). Lecturenotes (unpublished), ESA, ITC, Enschede, The Netherlands. Farshad, A., Shrestha, D.P., Munchun, R. and A. Suchinai. 2005b. An Attempt to Apply Digital Terrain Modeling to Soil Mapping, with special attention to sloping areas; Advances and Limitations. Presented in HinHua, Thailand, in wrap up seminar of the LDD-ITC funded research project. Farshad, A., Udomsri, S., Hansakdi, E. and D.P. Shrestha. 2006. GIS-based geopedology, a way to predictive soil mapping. IUSS, Philadelphia, Pennsylvania, USA. Gerrard, A.J., 1981. Soils and landforms, an integration of geomorphology and pedology. George Allen and Unwin, London, 219p. Goosen, D. 1967. Aerial photo-interpretation in soil survey. FAO Soils Bult. No. 6, FAO, Rome, 55p. ; and also ITC, Enschede, The Netherlands. Hengl, T., Rossiter, D.G., and S. Husnjak. 2002. mapping soil properties from an existing national soil data set using freely available ancillary data. 17th WCSS, BKK, Thailand. Paper No. 1140. Hudson, B.D. 1992. The soil survey as a paradigm-based science. Soil Science Society of America Journal 56, 836- 841. -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 24 Huggett, Richard John. 199. Geoecology, An evolutionary approach. Routledge. London and New York. Jenny, H. 1941. Factors of soil formation. McGraw-Hill, New York, 281p. Jenny, H., 1980. The soil resource. Origin and behaviour. Ecological stidies, v. 37. SpringerVerlag, New York, 377p. Juma, N. 1999. The pedosphere and its dynamics. A system approach to soil science. Salmon Productions, Canada.(http://www. Pedosphere.com) Li, Zhilin, Qing Zhu, and Christopher Gold. 2005. Digital terrain modeling: principles and methodology. CRC Press. Boca Raton, London, New York, Washington DC. Moran, C.J. and E.N. Bui. 2002. Spatial data mining for enhanced soil map modeling. Int. J. Geographical Information Ecience. Vol. 16, No. 6, p. 533-549. McBratney, A.B., Mendonca Santos, M.L. and B. Minasny. 2003. On digital soil mapping. Geoderma 117, 3-52. Available on line. Available on www.sciencedirect.com USDA, 1975. Soil Taxonomy. Handbook No. 436, 754p. USDA, 1993. Soil Survey Manual. Handbook No. 18, 437p. Zinck, J.A. 1988/89. Physiography and soils; soil survey courses; subject matter K6 (SOL41, lecture-notes), ITC, Enschede, The Netherlands. Zonneveld, I.S. 1979. Land evaluation and Land(scape) science. ITC, Enschede, The Netherlands, 134p. Zuidam, R.A. van. 1985. Aerial photo-interpretation in terrain analysis and geomorphological mapping. ITC, Enschede, The Netherlands. -------------------------------------------------------------------------------A.Farshad, DESA, ITC, Enschede, The Netherlands 25