Soil of the Year

Red grapes on a vineyard.Click to enlarge
Grapes on sun-drenched vineyard. The vineyards's soil characterizes their taste.
Source: S. Marahrens / Umweltbundesamt

Germany is blessed with many different types of soil. In the interest of shedding greater light on the world beneath our feet, each December 5th, on World Soil Day, the Soil of the Year is presented. A panel of experts selects the soil in question. In announcing the Soil of the Year, the panel indicatesamong other things its characteristics, origin and significance for today’s society.

Table of Contents

 

2013 Soil of the Year: plaggic anthrosol

The 2013 Soil of the Year, plaggic anthrosol, is testimony to an historical process involving removal of the upper layer of low-fertility soils, which were then mixed with manure and spread on fields – thus allowing for the creation of fertile topsoil on depleted soil. However, this process left behind large heathland or dune areas off Germany’s coasts.

What does plaggic anthrosol look like?

Plaggic anthrosol is an anywhere from 41 to 150 centimeter deep humus soil layer resulting from centuries-long spreading of slurry-soaked sods on farmland. Its traces are still visible in many areas by virtue of specific vegetation and typical field edges that this type of soil produced.

The coloration of plaggic anthrosol strata bears testimony to its origins. For example, grey plaggic anthrosol mainly stems from heath sods, while brown plaggic anthrosol mainly stems from pasture sods. As these layers are the result of human activity, residues of charcoal, bricks and other signs of daily use are often found.

How was plaggic anthrosol created?

The existence of plaggic anthrosol is attributable to so-called plaggen cultivation, which began in around the 10th century and coincided with continuous cultivation of rye. The introduction of this technique was as revolutionary an event in the annals of agriculture as the advent of mineral fertilizer was centuries later.

The term “plaggen” can refer to grass, weed and straw sod, as well as root systems and the soil that clings to roots. Sod is a section of earth that is removed using a tool. Sod was used as litter in animal stalls, was mixed with manure or composted, and was then used as fertilizer. This increased soil fertility, to which the higher soil value figures in these areas still testify today. However, the areas from which the soil was removed were deprived of humus and nutrients, to which heath vegetation and dune formation still bear testimony today.

Where is plaggic anthrosol found?

Grey plaggic anthrosol is mainly found in northwestern Germany, a mainly low-nutrient region that bears many geological traces of the Saale ice age. Brown plaggic anthrosol is mainly found to the south, in the areas extending from the Osnabruck to Munster regions. Isolated plaggic anthrosol areas are also found in the North Frisian region on the islands of Amrum, Föhr and Sylt. Plaggic anthrosol mainly occurs in small areas near towns or farms and thus cannot be readily depicted on maps.

Plaggic anthrosol use, yesterday and today

Plaggic anthrosol was at one time mainly used for rye cultivation, but is today used for all types of grain, as well as for potatoes and other root crops – although these crops are increasingly being displaced by corn. In northwestern Germany, plaggic anthrosol is also used for special crops at tree nurseries and the like.

Which functions does plaggic anthrosol perform for humans and the environment?

Plaggic anthrosol is an important artifact of our agricultural heritage. It bears testimony to all types of plaggen cultivation that were carried out using plaggic anthrosol soil and of which traces are still visible in today’s terrain. Plaggic anthrosol also contains archaeological artifacts that were dispersed via plaggic anthrosol creation and that are found in plaggic anthrosol layers. These layers also protect ancient archaeological artifacts.

What threats are plaggic anthrosol areas subject to?

Many plaggic anthrosol areas are currently threatened by their proximity to built-up areas and the like, and many such areas have already fallen victim to urban sprawl. But even using such areas for tree nurseries is problematic, because the trees are usually removed along with substantial amounts of the surrounding earth, resulting in major function loss.

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2012 Soil of the Year: fen soil

What are fen soils and what do they look like?

Fen soils are composed of more than 30 per cent organic substances, in the guise of peat ranging in color from dark brown to black. The plant elements that form fen peat are visible to the naked eye to a greater or lesser degree depending how well preserved the original plant is.

Fen soil substrates can be composed of sand, silt, loam, and/or clay – or mud composed of materials that accumulate in lakes. Depending on the starting material, this mud can be white in color (lime mud), olive in color (mud from algae) or dark brown in color (clay mud).

Fen soil is a histosol.

How are fens formed and where are they found?

Fens mainly form either in low lying areas owing to the effects of groundwater, or along rivers or lakes, and are mainly found in the cool and temperate climates of the northern hemisphere, which always have water surpluses due to the fact that the amount of precipitation exceeds the amount of water that evaporates.

Germany has around one million hectares of fens. The lion’s share of fens and the largest contiguous fen areas ranging up to 30,000 hectares in size are found in Schleswig-Holstein, Lower Saxony, Mecklenburg-West Pomerania, Brandenburg, Bavaria and Baden-Württemberg. The 211,000 hectares of fen in Brandenburg are mainly used as cultivated grassland.

The fen formation process usually begins with (a) bog formation resulting from a high water table; or (b) lake silting.

In fens resulting from bog formation, plant detritus accumulates in conditions characterized by water saturation and airlessness beneath the mineral subsoil.

In fens formed by lake silting, the peat forms on the muddy lake bottom comprising accumulations of organic or mineral sediment.

Fen peat arises from the detritus of bog flora roots, branches and leaves.

The process of breaking down the continuous influx of new materials unfolds very slowly and incompletely, owing to air deprivation, and requires the presence of microorganisms. The peat mass grows (upward) only a few millimeters per year on the water’s surface or in the middle of a lake. Peat that is more than 30 centimeters thick is referred to as fen soil.

What are the functions of fen soil and where is it used?

Natural fens are ecologically invaluable. Only very few specialized species of flora and fauna thrive under the complex conditions of fen ecosystems, which are characterized by high water content and very specific types of nutrients, including large copper, cotton grass and sedge.

Fens can contain up to 2,000 tons of carbon per acre, and are thus the world’s largest carbon sequestration areas per area unit.

The composition of peat provides insight into past vegetation and climate conditions; traces of previous uses and settlements are often found as well. Thus fens are an important repository of knowledge about nature and agricultural history.

In order for fens to be used for agriculture, forestry or human settlements, they must be drained – a process that occasions major and often irreversible changes in their properties. Most of Germany’s fens are currently used as grassland to varying degrees.

Fen peat has been used as a fuel, medicine and fertilizer for more than a thousand years, and industrial peat excavation continued into the middle of the 20th century. Bog iron, a type of iron-containing rock found in fens with iron-rich groundwater inflows, as well as lime mud, were excavated until the early 20th century. Today, Germany’s fen peat is used in very small areas, for medicinal purposes.

Owing to their rarity, intact, quasi-natural fens are protected under nature conservation laws in Germany.

What threats are fens subject to?

The main threat to which fens are subject is dewatering, which sets in motion the following processes, among others: peat shrinkage; fen surface contraction; oxygen influx into previously water saturated soil; peat mineralization; nutrient release; carbon emissions. These processes transform what was once a carbon sink into a diffuse carbon source. Moreover, global warming can result in the desiccation and destruction of fens

 

2011 Soil of the Year: vega (fluvisol)

What is vega and what does it look like?

Vega (also known as fluvisol) is brown, fertile soil that is found in river floodplains and that takes the form of brown alluvial soil. The term “vega” comes from the Spanish term for “fertile plain.”

Characteristics properties: dark, humus-rich topsoil with greyish brown, fine-grained subsoil that is clearly striated and that also often contains humus. Gravel layers from previous river deposits or topsoils from previous alluvial soil are often found below vegas. Vegas are flooded only sporadically and exhibit little groundwater influence on their surface. Thus they exhibit neither rust-colored iron oxide accumulations nor greyish-bluish coloration. 

How are vegas formed and where are they found?

Vegas (brown alluvial soils) are found worldwide along large rivers, and along small and medium sized rivers as well, particularly in hilly regions whose soil has been translocated by erosion. Loess regions, which are prone to erosion, are the main sources of the soil material constituting today’s vegas. Due to forest clear-cutting and subsequent farming (which dates back to the Neolithic period), large amounts of soil have been eroded.

Changing sedimentation environments and varying groundwater levels have produced a small-scale spatial pattern of diverse soils on the alluvial plains. Apart from vegas, gleysols and fens also occur in areas where groundwater is a major ambient factor. In areas where groundwater is less of a factor and no flooding occurs, cambisols and luvisols develop.

A distinction is made between two types of vegas, according to how they develop. The characteristic brownish color of allochthonous vegas is attributable to the previously weathered brown soil in alluvial sediments. Allochthonous vegas are referred to as such if they acquire their characteristic brownish coloration at their deposition site.

What are the functions of vegas and how are they used?

Vega soil properties vary according to their source area. Underneath a loose crumbly topsoil with active soil fauna is in most cases subsoil that is conducive to root penetration. As vegas exhibit high chemical bonding capacity, nutrients are stored in a readily phytoavailable form and pollutant leaching into groundwater is prevented. Apart from this purification effect during groundwater renewal, vegas make a major contribution to flood prevention by virtue of their high water retention capacity.

Owing to the great natural fertility of vegas and the fact that they generally contain sufficient amounts of water, they are highly desirable for farming. Sediment layers of alluvial soil provide valuable insight into terrain use and history. The impact of Germany’s industrial and mining activities are reflected by locally elevated levels of heavy metals and other organic pollutants in alluvial soils.

Under natural conditions, vegas develop a species-rich riparian forest comprising ash, elm, linden, British oak, hornbeam, as well as a biodiverse herbaceous vegetation layer. As alluvial soils are unique fauna habitats, the population density of earthworms and the like is as a rule extremely high, and river bank break-off events create ideal hatchery sites for kingfishers.

What threats are alluvial soils subject to?

Owing to their locations, vegas are very strongly affected by land use in for the most part densely populated river valleys. Moreover, levees and water table drawdown resulting from river regulation, gravel mining, water extraction and intensive farming destroy natural alluvial dynamics, thus endangering the natural state of the soil in alluvial plain ecosystems. Projects along all major rivers such as the Integrated Rhine Program (IRP) represent attempts to find a viable way to balance the various demands entailed by water users, flood prevention and flood plain restoration

 

2010 Soil of the Year: urban soil

What is urban soil?

Like the soils found in fields, meadows and forests, anthrosols are part of the soil environmental compartment that is essential for life. The term urban soil encompasses the many different types of soil that are found in urban industrial areas. The main factors that contribute to their genesis such as parent material, relief, climate, water flow, and flora and fauna vegetation are strongly affected by human activities – so strongly in fact that urban soils differ greatly from the soils found in rural areas.

Urban-soil usage for businesses, factories, homes, yards, green areas and fallow land strongly affects the development of urban soil in highly characteristic fashions. Soils in green areas often exhibit humus topsoil and a quasi-natural structure, while soils paved over by streets undergo drastic change. This patchwork of soils that have evolved naturally, soils with translocated components, and soils composed of construction, demolition and other waste, as well as slag and sludge, is a characteristic feature of urban landscapes.

The international (WRB) term for urban soils is technosols.

Cities have many different types of soil

Urban soils fulfill a great number of functions, most of which are not discernible at first glance. Most noticeable for urban dwellers are undoubtedly parks, yards and other green areas, where soil is used not only for recreational purposes, but also serves as a flora and fauna habitat. In conjunction with flora, soil also helps to temper urban climates in both summer and winter, and is an indispensable and irreplaceable source of oxygen for the world’s cities

The to some extent extreme properties of urban soils and the environs thereof often make for extremely biodiverse habitats, many of which serve as safe havens for rare flora and fauna. Most important of all, however, is that urban soils serve as construction sites for every imaginable kind of urban building, between which soils constitute the site for infrastructure elements of every description. Countless utility lines crisscross the ground beneath our feet, and without them urban life would be unthinkable. Rainwater can percolate into the ground in unpaved areas; and thus the soil helps to take strain off our sewage systems, helps prevent flooding, and provides us with clean groundwater and drinking water thanks to its filtering capabilities. The soil, as well as the flora that grow in urban soils, provide us with fresh air by filtering out and permanently binding particulate matter.

Urban soils bear testimony to the past

The ground underneath our feet has many stories to tell, in that each era of human settlement leaves behind traces. Thus many urban soils can potentially contain thousand year old construction waste or the remains of medieval town fires. Many European cities still have buried World War II rubble, and bombs from that war are uncovered on a regular basis in cities such as Budapest. Buried settlement structures, old waste, and ancient burial sites bear testimony to what are often very distant eras. Such findings provide archaeologists with insight into the lives of our forefathers. Commercial, mining and industrial activities also leave traces in the ground. In past eras, when waste disposal was unregulated, some soils were so heavily loaded that their filter and stabilization functions failed. Today, such areas need to be extensively cleaned up.

The problematic ecology of urban soil

One of the main soil protection challenges faced by Germany today is that some 12 per cent of our country’s surface area is occupied by human settlement and transport infrastructure elements. The soils in such paved over areas can carry out their vital functions such as water absorption and pollutant filtering to a limited extent only, and in some cases not at all; this in turn renders them inhospitable to flora and fauna.

Against this backdrop, it is essential that the government’s goal of limiting land use to 30 hectares per day by 2020 be reached. It is also crucially important that areas occupied by abandoned human settlement and transport infrastructure elements be reconverted to open space.

Urban soils are all around us

Endless opportunities await us to discover the urban ground beneath our feet and experience it at first hand, for such areas are all around us, in the form of playgrounds, parks, zoos, botanical gardens, unpaved bicycle paths, and set-asides – not to mention our own front and back yards.

 

Soils of the Year, 2005-2009

  • 2009: Lime marshes
  • 2008: Brown earth
  • 2007: Podsol
  • 2006: Albeluvisol
  • 2005: Black earth