Soil Survey and Databases in Iceland - Europa · Soil Survey and databases in Iceland. Ólafur...
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EUROPEAN SOIL BUREAU RESEARCH REPORT NO. 6 Soil Survey and databases in Iceland. Ólafur Arnalds 91 Soil Survey and Databases in Iceland Ólafur Arnalds Agricultural Research Institute, Keldnaholt, 112 Reykjavik, ICELAND Introduction Icelandic agriculture is characterized by the use of extensive rangelands for grazing and the making of hay for winter feeding. Cultivated land is of limited extent. Iceland has therefore traditionally put more emphasis on mapping vegetation resources rather than the soils. The history of soil science in Iceland is relatively young. Geologic aspects of the soils received considerable attention early on with the study of volcanic ash layers, but dating of soils by volcanic ash layers was pioneered by the Icelandic geologist Sigurdur Thorarinsson (1961). The first comprehensive map of of Icelandic soils was printed in 1959 at a scale of 1:750,000 (Nygard and Johanesson 1959). Other soil survey efforts were localized and this map together with Johannesson´s monograph on Icelandic soils (1960) remained the only complete survey of Icelandic soils until this year. In response to request made by the European Soil Bureau and other international agencies, the Agricultural Research Institute is now completing a soil map in the scale of 1:500,000. Soil Mapping in the Past The pioneer work by Johannesson (1960) established a framework for the classification of Icelandic soils that is still valid. The soil map that was included in his monograph is attributed to Ivar Nygard who started this work in 1951, but after Nygard’s death, Johannesson completed the map in co-operation with the US Soil Conservation Service. The map was printed by the U.S. Geologic Survey in 1959, but was included with both the Icelandic and English versions of Johannesson’s monograph on Icelandic soils (1960). The monograph was reprinted in Icelandic by the Agricultural Research Institute in 1988. The underlying basis for Johannesson´s and Nygard´s work was the US soil classification system (Baldwin et al., 1938). Johannesson established a classification system based on 23 mapping units, but the soils were devided into three major groups, the freely drained soils (silt loams), poorly drained soils (peat soils) and the soils of the deserts (stony alluvial, aeolian, lag gravel, etc). At the time of Johanesson´s studies, the unique properties of Andosols were only beginning to be realized, which limits the present applicability of this work. It is noteworthy, however, that Johannesson wrote in his monograph: “…is the fact that many silt loam soils have some characteristics like those of the volcanic ash soils in other countries, for instance those of Japan, and thus perhaps might be considered as close relatives to or even as members of the so-called Ando soil group..” After the work of Johannesson, emphasis was mainly on agronomic aspects of Icelandic soils, such as fertilization of hay fields and draining of wetland soils. Noteworthy is Helgason’s comprehensive account of soils of South-west Iceland (1963; 1968). Two Ph.D. dissertations added considerable knowledge on the basic characteristics of Icelandic soils in the eighties by Ólafsson (1974) and Guðmundsson (1978). The Agricultural Research Institute is still involved in soil evaluation for fertilizer recommendations, and has carried out extensive research related to soil fertility. The results have been reported both in specialized reports and as scientific papers (e.g., Palmason et al., 1996; Palmason and Helgason, 1996). Several attempts have been made to map soils in localized areas (e.g. Helgason and Gudbergsson, 1977; Gudbergsson and Olafsson, 1978), drawing much from the basis Johannesson provided. Gudbergsson (1982) made an outline for the classification of wetland soils (Histosols).
Transcript of Soil Survey and Databases in Iceland - Europa · Soil Survey and databases in Iceland. Ólafur...
EUROPEAN SOIL BUREAU RESEARCH REPORT NO. 6
Soil Survey and databases in Iceland. Ólafur Arnalds 91
Soil Survey and Databases in Iceland
Ólafur ArnaldsAgricultural Research Institute, Keldnaholt, 112 Reykjavik, ICELAND
IntroductionIcelandic agriculture is characterized by the use ofextensive rangelands for grazing and the makingof hay for winter feeding. Cultivated land is oflimited extent. Iceland has therefore traditionallyput more emphasis on mapping vegetationresources rather than the soils.
The history of soil science in Iceland is relativelyyoung. Geologic aspects of the soils receivedconsiderable attention early on with the study ofvolcanic ash layers, but dating of soils by volcanicash layers was pioneered by the Icelandicgeologist Sigurdur Thorarinsson (1961).
The first comprehensive map of of Icelandic soilswas printed in 1959 at a scale of 1:750,000(Nygard and Johanesson 1959). Other soil surveyefforts were localized and this map together withJohannesson´s monograph on Icelandic soils(1960) remained the only complete survey ofIcelandic soils until this year.
In response to request made by the European SoilBureau and other international agencies, theAgricultural Research Institute is now completinga soil map in the scale of 1:500,000.
Soil Mapping in the PastThe pioneer work by Johannesson (1960)established a framework for the classification ofIcelandic soils that is still valid. The soil map thatwas included in his monograph is attributed to IvarNygard who started this work in 1951, but afterNygard’s death, Johannesson completed the mapin co-operation with the US Soil ConservationService. The map was printed by the U.S.Geologic Survey in 1959, but was included withboth the Icelandic and English versions ofJohannesson’s monograph on Icelandic soils(1960). The monograph was reprinted in Icelandicby the Agricultural Research Institute in 1988.
The underlying basis for Johannesson´s andNygard´s work was the US soil classificationsystem (Baldwin et al., 1938).
Johannesson established a classification systembased on 23 mapping units, but the soils weredevided into three major groups, the freely drainedsoils (silt loams), poorly drained soils (peat soils)and the soils of the deserts (stony alluvial, aeolian,lag gravel, etc). At the time of Johanesson´sstudies, the unique properties of Andosols wereonly beginning to be realized, which limits thepresent applicability of this work. It is noteworthy,however, that Johannesson wrote in hismonograph: “…is the fact that many silt loam soilshave some characteristics like those of thevolcanic ash soils in other countries, for instancethose of Japan, and thus perhaps might beconsidered as close relatives to or even asmembers of the so-called Ando soil group..”
After the work of Johannesson, emphasis wasmainly on agronomic aspects of Icelandic soils,such as fertilization of hay fields and draining ofwetland soils. Noteworthy is Helgason’scomprehensive account of soils of South-westIceland (1963; 1968). Two Ph.D. dissertationsadded considerable knowledge on the basiccharacteristics of Icelandic soils in the eighties byÓlafsson (1974) and Guðmundsson (1978). TheAgricultural Research Institute is still involved insoil evaluation for fertilizer recommendations, andhas carried out extensive research related to soilfertility. The results have been reported both inspecialized reports and as scientific papers (e.g.,Palmason et al., 1996; Palmason and Helgason,1996).
Several attempts have been made to map soils inlocalized areas (e.g. Helgason and Gudbergsson,1977; Gudbergsson and Olafsson, 1978), drawingmuch from the basis Johannesson provided.Gudbergsson (1982) made an outline for theclassification of wetland soils (Histosols).
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Current Soil MappingActivities
Soil Taxonomy and FAO WorldReference BaseSoil mapping needs to be based on a suitable soilclassification system. The Agricultural ResearchInstitute collaborated with Texas A&M Universityand the USDA-NRCS to provide a newperspective on Icelandic soils for this purpose,with detailed analyses of several representativesoil pedons (Arnalds, 1990; Arnalds et al., 1995;Arnalds and Kimble, unpublished data; Wada etal., 1992). These studies show that Icelandic soilsare Andosols and Andic integrates of other soilgroups to a large extent. More recent overview ofIcelandic soils was published by Arnalds (1999a).
The soils of the barren areas in Iceland are quitedifferent from the typical Andosols and Histosolthat cover other parts of the country. Arnalds(1988; 1990) and Gudmundsson (1991) havepublished studies on these soils. Arnalds andKimble conducted a detailed analysis of tenrepresentative pedons of Icelandic desert soils butthe results are still being analyzed.
A steady input of eolian materials and occasionaltephra additions cause the organic carbon contentto be lower than 25% in many of the wetland soils,resulting in Andisol (US-Soil Survey Staff, 1998)rather than Histosol classification (Arnalds et al.,1999). The desert soils are also often classified asAndisol because of their high volcanic glasscontent.
The current edition of the US Soil Taxonomy (USSoil Survey Staff, 1998) has therefore thedisadvantage in relation to the classification ofIcelandic soils that it fails to distinguish betweensome of the major soil types at the highest levelbecause of dominating andic influences.
This can also be judged as a benefit, demonstratingthe dominating influence of andic soil propertiesof Icelandic soils.
Applying the FAO soil classification (FAO, 1998)system involves similar problems as for the USsystem in that many contrasting soils are classifiedthe same at the highest level as Andosols. Thewetland soils often do not meet the cryterion forHistosols because of relatively low organic contentand the dominance of volcanic glass in desert soilsoften excludes Arenosols, Fluvisols, Cambisolsand Regosols as soil groups. However, ThorsteinnGudmundsson (1994) found that the FAO legend(FAO-UNESCO, 1988) provided a good framworkfor mapping soils in Iceland. He translated andadapted the FAO system for use in Iceland.
The Icelandic adoption of the FAO scheme for thesoil groups (Gudmundsson, 1994) does not fullycorrelate with the FAO World Reference Base(FAO 1998) for reasons stated above. Its use maytherefore cause problems in relating Icelandic soilinformation at an international level although, withmodifications, it is well suited for domestic use.
Current soil mapping effortThe Agricultural Research Institute is currentlymaking an effort to produce a soil map in1:500,000. Soil classification issues have not beenresolved yet. A preliminary version of this map ispublished with this paper (Figure 1). The soilinformation underlying the map is drawn frompublished and unpublished literature on Icelandicsoils, which currently is being compiled for adatabank and an overview publication. Somegeneral characteristics are presented in Table 1.
Soil analysis generally follows standard methodsdesigned for Andosols such as described byBlakemore et al., 1987. Soil descriptions generallyfollow US methods (eg., USDA-NRCS 1998).
Table 1. General characteristics of major soil classes in Iceland. Common ranges.
Soil Classkm2
Depthm
OC%
pHin H2O
OxalateAl+1/2Fe%
Clay%
CECMeq/100g
H2O15 bar
Brown Andosols 43 770 0.5-1.5 2-10 5.5-6.5 3-8 15-40 10-40 30-60Organic Andosols 8 600 0.5-5 5-30 4.5-5.5 >2 ? 30-60 60-120Vitric Andosols 1 8600 0.2-0.5 0.5-1.5 6.5-7.0 1-2 5-15 5-15 5-15Leptosols� 4 540Sandy Andosols� 15 090 0-2 0.2-2 6.5-7.0 0.3-0.8 1-5 2-10 1-10
�������� No data available � Area (km2) includes both Sandy Andosols and Sandy Andosols/Leptosol complex.
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Figure 1: Soil map of Iceland at 1:500,000 scale.
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The geographic information is mainly drawn fromthree sources:1. Vegetation maps. Vegetation reflects soil
conditions, especially the distinction betweenwetlands (organic soils), freely drainedvegetated Andosols and the deserts.
2. Soil Erosion digital databases (see later in thepaper). This information gives a goodgeomorphological overview of the desertsurfaces, and is the primary source for theirgeographic information.
3. Infrared satellite images (LANDSAT TM).They are used where there is a lack ofvegetation information. The images alsoprovide the base map, correlated withIceland´s current map projection system.
The map was constructed using Arc/Info GISsoftware. The soil classes used in the map are asfollows (note the class names are only suggestiveat this stage and are subject to furtherdevelopment):1. Brown Andosols. These represent the typical
Andosols of Iceland. They are usually freelydrained and have developed in eolian andtephra materials that typically form a 80-200cm mantle that has accumulated over an oldersurface (usually glacial till or lava). They arerich in allophane clay minerals, andferrihydrate, but volcanic glass is also inabundance near the most active volanoes.Distinctive volcanic ash layers are common.
2. Organic Andosols. These soils are found atpoorly drained sites (bogs and myres), andoften grade into Histosols. They most likelyclassify as Histosols in areas furthest awayfrom eolian sources. The Organic Andosolsare typically 50-500 cm thick with 5-30% Ccontent. Volcanic ash layers are common.
3. Vitric Andosols (or Gravelly Andosols).These soils are desert soils poor in organicmatter compared to the classes above. Theymeet the criterion for Andosols (and Andisols)because of abundance of volcanic glassmaterials and other andic characteristics. TheVitric Andosols grade into Regosols (awayfrom eolian tephra sources) and Leptosols.
4. Leptosols. These soils are found on screeslopes, recent lava surfaces, and on lavasurfaces where erosion processes haveremoved Brown or Organic Andosols fromthe top.
5. Sandy Andosols. Sandy surfaces are commonin Iceland near glacial margins and on glacio-fluvial floodplains. Eolian processes haveoften carried sandy materials long distancesfrom their sources, increasing the size ofsandy areas. The sand is largely composed ofvolcanic glass.
6. Leptosol/Sandy Andosol complex. This is aspecial class as this combination is verycommon in Iceland. It occurs where there isan abundance of sand on lava surfaces (due toeolian processes and volcanic ash fall). Thesand covers the depressions while bedrock(lava surface) sticks out where the surfacerises.
Two other soil classes can readily be applied intothis system, but can not be included on a map atsuch a coarse scale. These are Gleysols and FluvicAndosols (which grade into Fluvisols, Gleysolsand Regosols).
Andosols in Iceland cover all together about80,000 km2 and therefore make up a substantialproportion of the Andosols in the world. The arealextent of Brown Andosols represents anoverestimate for two reasons. One is that desertareas /patches are common within areas dominatedby the Brown Andosols. The second is that theland classification system used includes someareas within this class where the soils are tooshallow to meet the criteria for Andisol/Andosol.At this point, it is not possible to account for thiserror.
The three desert soil classes dominate about38,000 km2, (actual extent is somewhat larger forthe reason given above). They have vast potentialfor carbon sequestration associated with ecosystemrestoration (Arnalds et al. 1999). No data isavailable for the Leptosols yet.
National Soil ErosionDatabaseSoil erosion and degradation has been a majorproblem in Iceland since the arrival of man about1100 years ago. The extent and severity of soilerosion in Iceland has been mapped at a scale of1:100,000, by the Agricultural Research Instituteand the Icelandic Soil Conservation Service.Erosion processes in Iceland are extremely variedand conventional methods designed for estimatingerosion in cultivated areas are of little use.
The erosion assessment is based on classificationof erosion forms that can be identified in thelandscape (Arnalds et al., 1997). The ARI-SCSerosion database is made of about 18,000polygons. Each polygon is characterized by one ormore erosion forms. Erosion severity for each ofthe erosion forms was estimated on a scale fromzero to five, five being considered extremelysevere erosion (Table 2).
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Table 2. Overview of soil erosion in Iceland.
Erosion severity/map units Km2 % Iceland %$
0 No erosion 4 148 4 5.21 Slight erosion 7 466 7 9.42 Moderate erosion 26 698 26 33.73 Considerable erosion 23 106 23 29.24 Severe erosion 11 332 11 14.35 Very severe erosion 6 375 6 8.1 High mountains 9 794 10 Glaciers 11 361 11 Waters 1 436 1.4 Other 1 010 1TOTAL 102 721 100
$: High mountains, glaciers, waters and ‘other’ excluded.
The overall results indicate the severity of erosionin Iceland, the scale of which is comparable onlyto very degraded, arid areas of the world. Thecombined total of considerable to very severeerosion is >50% of the country when highmountains and glaciers have been excluded. Muchof this severe erosion occurs within the deserts, butsevere erosion is also degrading large tracts of theremaining vegetated areas (see Arnalds et al.,1997; Arnalds, 1999b).
Soil erosion continues to be monitored andmapped by the Icelandic SCS, in areas where it ismost severe, but now at a larger scale (1:5,000 to1:25,000).
Vegetation MappingAlthough detailed soil maps have not been madefor Iceland, much effort has been made to makevegetation maps. It was concluded around 1960that vegetation maps would give more informationabout Icelandic nature than would soil maps,bearing in mind the major use of the land forgrazing. It was expected that each of thevegetation mapping elements reveal informationon the underlying soils.
Mapping of the vegetation was conducted by theAgricultural Research Institute but the programmehas recently been relocated at the Institute ofNatural History. Vegetation mapping has beencompleted for about 2/3 of the country at a scale of1:40,000 in the highlands and 1:25,000 in lowlandareas. Icelandic vegetation was split up into fivemajor categories where drainage is the mostinfluential factor.
These categories are divided into 14 associationsand about 100 mapping elements. Deserts aremapped separately. The methods were described in
detail in a special issue of the Journal ofAgricultural Research in Iceland (Thorsteinsson,1982). Much of this data has been digitized and theInstitute of Natural History has recently publisheda new vegetation map for all of Iceland in the scaleof 1:500,000.
OutlookA central database for Icelandic soils is beingestablished. The main use for soil data is related tosoil fertility for hay production. Detailed soilresearch has also provided fundamentalunderstanding to explain why the soils areextremely vulnerable to erosion. The nationalerosion database is used for various purposes suchas land use planning, reclamation strategies, andpolicy-making.
Soil science is still a young science in Iceland.Few Icelandic scientists have higher degrees insoil science. This is reflected in all too sparseresearch efforts. The Agricultural ResearchInstitute has plans to increase its current researchon the formation and basic properties of Icelandicsoils.
Currently, there is no systematic monitoring of soilfertility and quality, but plans have been made forsuch activities. Mapping of soil resources willbecome more important with increased emphasison GIS databases for land capability assessmentand land use planning in Iceland. Improved basicunderstanding of soil behaviour will also becomeimportant in the near future for maintaining soilquality and for monitoring pollution.
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