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This paper reports soil development over time in different climates, on time-scales ranging from a few thousand to several hundred thousand years. Changes in soil properties over time, underlying soil-forming processes and their rates are presented. The paper is based on six soil chronosequences, i.e. sequences of soils of different age that are supposed to have developed under the similar conditions with regard to climate, vegetation and other living organisms, relief and parent material. The six soil chronosequences are from humid-temperate, Mediterranean and semi-arid climates. They are compared with regard to soil thickness increase, changes in soil pH, formation of pedogenic iron oxides (expressed as Fed/Fet ratios), clay formation, dust influx (both reflected in clay/silt ratios), and silicate weathering and leaching of base cations (expressed as (Ca+Mg+K+Na)/Al molar ratios) over time. This comparison reveals that the increase of solum thickness with time can be best described by logarithmic equations in all three types of climates. Fed/Fet ratios (proportion of pedogenic iron Fed compared to total iron Fet) reflects the transformation of iron in primary minerals into pedogenic iron. This ratio usually increases with time, except for regions, where the influx of dust (having low Fed/Fet ratios) prevails over the process of pedogenic iron oxide formation, which is the case in the Patagonian chronosequences. Dust influx has also a substantial influence on the time courses of clay/silt ratios and on element indices of silicate weathering. Using the example of a 730 ka soil chronosequence from southern Italy, the fact that soils of long chronosequences inevitably experienced major environmental changes is demonstrated, and, consequentially a modified definition of requirements for soil chronosequences is suggested. Moreover, pedogenic thresholds, feedback systems and progressive versus regressive processes identified in the soil chronosequences are discussed.

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The first results of modeling soil development in marine sediments in S Norway using the model SoilGen are compared to measured properties of two soil chronosequences, on the western and eastern side of Oslofjord, respectively. The aim of this work is to test how well soil development under well-defined environmental conditions can be modeled. Such testing reveals to what degree soil-forming processes are understood, allowing formulation of adequate calculations reflecting these processes. The model predicts particle size distribution reasonably well, although clay depletion in the upper parts of the soils as a result of clay migration is overestimated. The model tends to underestimate contents of organic carbon and CEC in the A horizons: below, modeled CEC matches well with measured CEC. Base saturation is overestimated in the upper 40 cm and underestimated below. Apparently, leaching of bases proceeds less rapidly in reality than is predicted by the model, due to strong soil structure of the B horizons, causing preferential flow and base leaching around the aggregates, whereas bases inside the aggregates are only slightly affected by leaching. Difficulties and possibilities for improvements are identified, some related to model input data and some to the model itself. Input data could be improved by determining the amounts of organic carbon in organic surface horizons and by quantifying effects of bioturbation. A big challenge is the implementation of soil structure formation in the model. Quantitative data on the development of soil structure with time that can be included in a model are required. Amounts, distribution and connectivity of macro pores need to be defined for each stage of soil development, and zones of low and high base leaching need to be distinguished in the model for each time step. The long-term aim of this work is to model soil development with different sets of soil-forming factors, e.g. different climatic conditions in order to reliably predict soil development under different climate scenarios and related sets of soil-forming factors. The results of the first model runs and the identified possible improvements suggest that this aim is generally achievable.

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This paper reports a study on soil development in loamy marine sediments on both sides of the Oslofjord (Vestfold, Ostfold). This region has been subject to steady glacio-isostatic uplift during the whole Holocene. Hence, land surface age continuously increases from the coast inland. Several sea level curves, based on radiocarbon datings, enable estimation of land surface age for all locations. Clay illuviation starts in less than 1650 years. E horizons become lighter with age, but their lower boundary stays around 40 cm for more than 10 000 years. Albeluvic tongues develop between 4600 and 6200 years. Initially, they form along intersections of cracks. As preferential flow and leaching along the cracks continues, the tongues increase in length and width, progressively consuming the prisms between the cracks in the upper Bt horizon. The Fe-d/Fe-t ratios (weighted means of the upper meter) show a clear linear increase with soil age and may be used for "pedo-dating", i.e. for estimating the ages of non-dated land surfaces covered with similar sediments. In contrast, the logarithmic decrease of base saturation and pH, with rapid changes in the first time but only very slight changes between 2000 and 10 000 years, makes these parameters unsuitable for "pedo-dating". (c) 2008 Elsevier Ltd and INQUA. All rights reserved.

Sammendrag

Klassifisering av jordsmonn er nødvendig for å forstå likheter, forskjeller og slektskap mellom jordtyper. Dette gjør at man kan forutsi jordas egenskaper, forutsi produktiviteten, identifisere problemer med å forvalte jorda og foreslå tiltak. I Norge er det til nå kartlagt 270 jordsmonnenheter (WRB-enheter) fordelt på 13 jordsmonngrupper (WRB-grupper). Dette heftet gir en oversikt over de jordsmonngruppene som er kartlagt på dyrka mark i Norge til nå. I tillegg er de 50 mest utbredte jordsmonnenhetene på dyrka mark beskrevet. Hver jordsmonngruppe og -enhet er beskrevet med karakteristikk, agronomiske egenskaper, beliggenhet og utbredelse. Det er det internasjonale jordklassifikasjonssystemet World Reference Base (WRB) som i dag brukes ved Norsk institutt for skog og landskap (heretter Skog og landskap).

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Østfold er ett av landets minste fylker, men har størst jordbruksareal i drift i forhold til landarealet. Fra naturens side har fylket gode forutsetninger for en allsidig mat- og fôrproduksjon, både med hensyn på jordsmonn, klima og topografi. Selv om over 80% av jordbruksarealet brukes til korn og oljevekster, står områdene på Raet for en svært viktig produksjon av poteter og grønnsaker. Ved jordsmonnklassifikasjon samles jordsmonnet i grupper eller enheter basert på likheter og slektskap. Jordsmonn som tilhører samme gruppe eller enhet, vil derfor ha en rekke felles egenskaper. Klassifikasjonen av jordsmonnet på dyrka mark i Østfold er basert på World Reference Base for Soil Resources (WRB). Det er en tydelig sammenheng mellom klassifikasjon, geologisk opphavsmateriale og terrengforhold. Dette har gitt grunnlag for å dele fylket inn i 9 jordsmonnregioner med hver sin unike fordeling av jordsmonn. På fylkesbasis utgjør WRB-gruppene Albeluvisols, Stagnosols og Gleysols tre fjerdedeler av jordbruksarealet. I tillegg utgjør planerte arealer vel 11%. Men ser en på de enkelte jordsmonnregionene, er det store avvik fra dette generelle bildet. I region 2, Raet og Jeløya, representerer disse tre WRB-gruppene litt over fjerdedelen av jordbruksarealet, mens WRB-gruppene Arenosols og Cambisols utgjør 50%. Den store andelen med Stagnosols, Gleysols og Albeluvisols viser at en svært stor del av jordbruksarealet i fylket har behov for grøfting. Men det er store regionale forskjeller. Mens bare 4% av jordbruksarealet i region 4 (leirjordsområdene i indre deler av Østfold) er selvdrenert, består hele 71% av jordbruksarealet i region 2 (Raet og Jeløya) av selvdrenert jordsmonn.

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The coastal areas of SE Norway provide suitable conditions for studying soil development with time, because unweathered land surfaces have continuously been raised above sea level by glacio-isostatic uplift since the termination of the last ice age. We investigated Podzol development in a chronosequence of six soils on sandy beach deposits with ages ranging from 2,300 to 9,650 y at the W coast of the Oslofjord. The climate in this area is rather mild with a mean annual temperature of 6 degrees C and an annual precipitation of 975mm (Sandefjord). The youngest soil showed no evidence of pocizolization, while slight lightening of the A horizon of the second soil (3,800 years) indicated initial leaching of organic matter (OM). In the 4,300 y-old soil also Fe and humus accumulation in the B horizon were perceptible, but only the 6,600 y-old and older soils exhibited spodic horizons. Accumulation of OM in the A horizons reached a steady state in <2,300 y, while in the B horizons OM accumulated at increasing rates. pH dropped from 6.6 (H2O)/5-9 (KCI) in the recent beach sand to 4.5 (H2O)/3.8 (KCl) within approx. 4,500 y (pH(H2O))/2,500 y (pH(KCl)) and stayed constant thereafter, which was attributed to sesquioxide buffering. Base saturation showed an exponential decrease with time. Progressive weathering was reflected by increasing Fe-d and Al-d contents, and proceeding podzolization by increasing amounts of pyrophophate- and oxalate-soluble Fe and Al with soil age. These increases could be best described for most Fe and Al fractions by exponential models. Only the increasing amounts of Fe-p could be better described by a power function and those of Fe-o by a linear model.

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Podzol development was investigated in a chronosequence on sandy beach sediments, the ages of the soils ranging from 2,400 to 8,500 years. All soil properties investigated-the organic matter content of the B horizons, clay content, Fe-o, Al-o, Si-o, Fe-o/Fe-d and Fe-d/Fe-t - tend to increase with advancing podzolization, and are strongly correlated with soil age. Topsoil pH values decrease with age. The characteristic Bh and Bs horizons had developed after approximately 4,000 years.

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Vestfold er landets nest minste fylke, men har størst andel jordbruksareal i drift i forhold til totalarealet. Ved jordsmonnklassifi kasjon samles jordsmonnet i grupper eller enheter basert på forskjeller og likheter. Jordsmonn som tilhører samme gruppe eller enhet, vil derfor ha en rekke felles egenskaper. Klassifi kasjonen av jordsmonnet på dyrka mark i Vestfold er basert på World Reference Base for Soil Resources (WRB). Det er en tydelig sammenheng mellom klassifi kasjon, geologisk opphavsmateriale og terrengforhold. Dette har gitt grunnlag for å dele fylket inn i 4 jordsmonnregioner med hver sin unike fordeling av jordsmonn. 3/4 av jordbruksarealet utgjøres av WRB-gruppene Albeluvisols, Stagnosols og Cambisols, mens den siste fjerdedelen utgjøres av hele 9 andre grupper. Utbredelsen av de ulike WRB-gruppene framgår av oversiktskart i målestokk 1:400 000, samt regionvise kart i målestokk 1:50 000.

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Dette heftet inneholder retningslinjer for å utføre en fullstendig profilbeskrivelse i overensstemmelse med “Soil Survey Manual” med de unntak norsk tradisjon og arbeidsrutiner som NIJOS krever. Disse retningslinjene er basis for undersøkelser for kartleggere av jordsmonn, pedologer, agronomer, økologer og studenter.