Impact of elevated CO2 on soil carbon reserves

Soil carbon is the solid

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

stored in global soils. This includes both

soil organic matter Soil organic matter (SOM) is the organic matter component of soil, consisting of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize. SOM provides numerou ...

and

inorganic An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inor ...

carbon as

carbonate minerals Carbonate minerals are those minerals containing the carbonate ion, . Carbonate divisions Anhydrous carbonates *Calcite group: trigonal **Calcite CaCO3 **Gaspéite (Ni,Mg,Fe2+)CO3 **Magnesite MgCO3 **Otavite CdCO3 **Rhodochrosite MnCO3 **Sider ...

. It is vital to the soil capacity in our ecosystem. Soil carbon is a

carbon sink A carbon sink is a natural or artificial carbon sequestration process that "removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere". These sinks form an important part of the natural carbon cycle. An overar ...

in regard to the global

carbon cycle The carbon cycle is a part of the biogeochemical cycle where carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycl ...

, playing a role in

biogeochemistry Biogeochemistry is the Branches of science, scientific discipline that involves the study of the chemistry, chemical, physics, physical, geology, geological, and biology, biological processes and reactions that govern the composition of the natu ...

climate change mitigation Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include energy conservation, conserving energy and Fossil fuel phase-out, repl ...

, and constructing global climate models.

Microorganisms A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...

play an important role in breaking down carbon in the soil. Changes in their activity due to rising temperatures could possibly influence and even contribute to climate change. Human activities have caused a massive loss of soil organic carbon. For example, anthropogenic fires destroy the top layer of the soil, exposing soil to excessive oxidation.

Overview

Soil carbon is present in two forms: inorganic and organic. Soil inorganic carbon consists of mineral forms of carbon, either from

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

parent material Parent material is the underlying geological material (generally bedrock or a superficial deposits, superficial or drift (geology), drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from th ...

, or from reaction of soil minerals with atmospheric CO₂.

Carbonate minerals Carbonate minerals are those minerals containing the carbonate ion, . Carbonate divisions Anhydrous carbonates *Calcite group: trigonal **Calcite CaCO3 **Gaspéite (Ni,Mg,Fe2+)CO3 **Magnesite MgCO3 **Otavite CdCO3 **Rhodochrosite MnCO3 **Sider ...

are the dominant form of soil carbon in

desert climate The desert climate or arid climate (in the Köppen climate classification ''BWh'' and ''BWk'') is a dry climate sub-type in which there is a severe excess of evaporation over precipitation. The typically bald, rocky, or sandy surfaces in desert ...

s. Soil organic carbon is present as

. It includes relatively available carbon as fresh plant remains and relatively inert carbon in materials derived from plant remains:

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

and

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ca ...

. Soil carbon is critical for terrestrial organisms and is one of the most important carbon pools, with the majority of carbon stored in forests. Biotic factors include photosynthetic assimilation of fixed carbon, decomposition of biomass, and the activities of diverse communities of soil organisms. Climate, landscape dynamics, fires, and mineralogy are some of the important abiotic factors. Anthropogenic factors have increasingly changed soil carbon distributions. Industrial nitrogen fixation, agricultural practices, and land use and other management practices are some anthropogenic activities that have altered soil carbon.

Global carbon cycle

Soil carbon distribution and accumulation arises from complex and dynamic processes influenced by biotic, abiotic, and anthropogenic factors. Although exact quantities are difficult to measure, soil carbon has been lost through land use changes, deforestation, and agricultural practices. While many environmental factors affect the total stored carbon in terrestrial ecosystems, in general, primary production and decomposition are the main drivers in balancing the total amount of stored carbon on land. Atmospheric CO₂ is taken up by photosynthetic organisms and stored as organic matter in terrestrial ecosystems. Although exact quantities are difficult to measure, human activities have caused substantial losses of soil organic carbon. Of the 2,700 Gt of carbon stored in soils worldwide, 1550 GtC is organic and 950 GtC is inorganic carbon, which is approximately three times greater than the current atmospheric carbon and 240 times higher compared with the current annual fossil fuel emission. The balance of soil carbon is held in

peat Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...

and wetlands (150 GtC), and in

plant litter Plant litter (also leaf litter, tree litter, soil litter, litterfall, or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that has fallen to the ground. This detritus or dead organic material and its constituent ...

at the soil surface (50 GtC). This compares to 780 GtC in the

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

, and 600 GtC in all living organisms. The oceanic pool of carbon accounts for 38,200 GtC. About 60 GtC/yr accumulates in the soil. This 60 GtC/yr is the balance of 120 GtC/yr contracted from the atmosphere by terrestrial plant

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

reduced by 60 GtC/yr of plant respiration. An equivalent 60 GtC/yr is respired from soil, joining the 60 GtC/yr plant respiration to return to the atmosphere.

Impacts of climate change on soil

Climate change is a leading factor in

soil formation Soil formation, also known as pedogenesis, is the process of soil genesis as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order ( anisotropy) within soils. These alteration ...

as well as in its development of chemical and physical properties. Therefore, changes in climate will impact the soil in many ways that are still are not fully understood, but changes in fertility,

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Moisture is defined as water in the adsorbed or absorbed phase. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some comme ...

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

, SOC, sequestration, aggregation etc. are predicted. In 1996, Least-Limiting Water Range (LLWR) was created to quantify the physical changes in soil. This indicator measures changes in

available water capacity Available water capacity is the amount of water that can be stored in a soil profile and be available for growing crops. It is also known as available water content (AWC), profile available water (PAW) or total available water (TAW). The concept, p ...

soil structure In geotechnical engineering, soil structure describes the arrangement of the solid parts of the soil and of the Pore space in soil, pore space located between them. It is determined by how individual soil granules clump, bind together, and Soil a ...

, air filed porosity, soil strength, and oxygen diffusion rate. Changes in LLWR are known to alter ecosystems but it's to a different capacity in each region. For example, in polar regions where temperatures are more susceptible to drastic changes, melting permafrost can expose more land which leads to higher rates of

plant growth Important structures in plant development are buds, Shoot (botany), shoots, roots, leaf, leaves, and flowers; plants produce these tissues and structures throughout their life from meristems located at the tips of organs, or between mature tissues. ...

and eventually, higher carbon absorption. In contrast, tropical environments experience worsening soil quality because soil aggregation levels decrease with higher temperatures. Soil also has carbon sequestration abilities where

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

is fixed in the soil by plant uptakes. This accounts for the majority of the

(SOM) in the ground, and creates a large storage pool (around 1500 Pg) for carbon in just the first few meters of soil and 20-40% of that organic carbon has a residence life exceeding 100 years.

Organic carbon

Soil carbon cycle through the microbial loop

Soil organic carbon is divided between living

soil biota Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by restri ...

and dead

biotic material Biotic material or biological derived material is any material that originates from living organisms. Most such materials contain carbon and are capable of decay. The earliest form of life on Earth arose at least 3.5 billion years ago.Schopf, ...

derived from biomass. Together these comprise the

soil food web The soil food web is the community of organisms living all or part of their lives in the soil. It describes a complex living system in the soil and how it interacts with the environment, plants, and animals. Food webs describe the transfer of e ...

, with the living component sustained by the biotic material component. Soil biota includes

earthworms An earthworm is a soil-dwelling terrestrial animal, terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (biology), class (or subclass (biology), subclass, depending on ...

nematodes The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (he ...

protozoa Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

and different

arthropods Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

Detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

resulting from plant senescence is the major source of soil organic carbon. Plant materials, with

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

s high in

cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...

and

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...

, are decomposed and the not- respired carbon is retained as

. Cellulose and starches readily degrade, resulting in short residence times. More persistent forms of organic C include lignin, humus, organic matter encapsulated in soil aggregates, and charcoal. These resist alteration and have long residence times. Soil organic carbon tends to be concentrated in the topsoil.

Topsoil Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Description Topsoil is composed of mineral particles and organic mat ...

ranges from 0.5% to 3.0% organic carbon for most upland soils. Soils with less than 0.5% organic C are mostly limited to

desert A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...

areas. Soils containing greater than 12–18% organic carbon are generally classified as organic soils. High levels of organic C develop in soils supporting wetland ecology, flood deposition,

fire ecology Fire ecology is a scientific discipline concerned with the effects of fire on natural ecosystems. Many ecosystems, particularly prairie, savanna, chaparral and coniferous forests, have evolved with fire as an essential contributor to habitat vit ...

, and human activity. Fire derived forms of carbon are present in most soils as unweathered

and weathered

black carbon Black carbon (BC) is the light-absorbing refractory form of Chemical_element, elemental carbon remaining after pyrolysis (e.g., charcoal) or produced by incomplete combustion (e.g., soot). Tihomir Novakov originated the term black carbon in ...

. Soil organic carbon is typically 5–50% derived from char, with levels above 50% encountered in mollisol, chernozem, and

terra preta ''Terra preta'' (, literally "black soil" in Portuguese language, Portuguese), also known as Amazonian dark earth or Indian black earth, is a type of very dark, fertile human impact on the environment, anthropogenic soil (anthrosol) found in the ...

soils. Root exudates are another source of soil carbon. 5–20% of the total plant carbon fixed during photosynthesis is supplied as root exudates in support of rhizospheric mutualistic biota. Microbial populations are typically higher in the rhizosphere than in adjacent bulk soil.

SOC and other soil properties

Soil organic carbon (SOC) concentrations in sandy soils influence soil bulk density which decreases with an increase in SOC. Bulk density is important for calculating SOC stocks and higher SOC concentrations increase SOC stocks but the effect will be somewhat reduced by the decrease in bulk density. Soil organic carbon increased the cation exchange capacity (CEC), a measure of

soil fertility Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality.

, in sandy soils. SOC was higher in sandy soils with higher pH. found that up to 76% of the variation in CEC was caused by SOC, and up to 95% of variation in CEC was attributed to SOC and pH. Soil organic matter and specific surface area has been shown to account for 97% of variation in CEC whereas

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

content accounts for 58%. Soil organic carbon increased with an increase in silt and clay content. The silt and clay size fractions have the ability to protect SOC in soil aggregates. When organic matter decomposes, the organic matter binds with silt and clay forming aggregates. Soil organic carbon is higher in silt and clay sized fractions than in sand sized fractions, and is generally highest in the clay sized fractions.

Soil health

Organic carbon is vital to soil capacity to provide edaphic

ecosystem services Ecosystem services are the various benefits that humans derive from Ecosystem, ecosystems. The interconnected Biotic_material, living and Abiotic, non-living components of the natural environment offer benefits such as pollination of crops, clean ...

. The condition of this capacity is termed

soil health Soil health is a state of a soil meeting its range of ecosystem functions as appropriate to its environment. In more colloquial terms, the health of soil arises from favorable interactions of all soil components (living and non-living) that belong ...

, a term that communicates the value of understanding soil as a living system as opposed to an

abiotic component In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them und ...

. Specific carbon related benchmarks used to evaluate soil health include CO₂ release, humus levels, and microbial metabolic activity.

Losses

The exchange of carbon between soils and the atmosphere is a significant part of the world carbon cycle. Carbon, as it relates to the organic matter of soils, is a major component of soil and catchment health. Several factors affect the variation that exists in soil organic matter and soil carbon; the most significant has, in contemporary times, been the influence of humans and agricultural systems. Although exact quantities are difficult to measure, human activities have caused massive losses of soil organic carbon. First was the use of

fire Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. Flames, the most visible portion of the fire, are produced in the combustion re ...

, which removes soil cover and leads to immediate and continuing losses of soil organic carbon.

Tillage Tillage is the agriculture, agricultural preparation of soil by mechanical wikt:agitation#Noun, agitation of various types, such as digging, stirring, and overturning. Examples of manual labour, human-powered tilling methods using hand tools inc ...

and

drainage Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess water. The internal drainage of most agricultural soils can prevent severe waterlogging (anaerobic conditions that harm root gro ...

both expose soil organic matter to oxygen and oxidation. In the

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

East Anglia East Anglia is an area of the East of England, often defined as including the counties of Norfolk, Suffolk and Cambridgeshire, with parts of Essex sometimes also included. The name derives from the Anglo-Saxon kingdom of the East Angles, ...

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

, and the California Delta, subsidence of

lands from oxidation has been severe as a result of tillage and drainage.

Grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...

management that exposes soil (through either excessive or insufficient recovery periods) can also cause losses of soil organic carbon.

Managing soil carbon

Natural variations in soil carbon occur as a result of

climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

, time, and relief. The greatest contemporary influence has been that of humans; for example, carbon in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

agricultural Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created f ...

soils may historically have been twice the present range that is typically 1.6–4.6%. It has long been encouraged that farmers adjust practices to maintain or increase the organic component in the soil. On one hand, practices that hasten oxidation of carbon (such as burning crop stubbles or over-cultivation) are discouraged; on the other hand, incorporation of organic material (such as in manuring) has been encouraged. Increasing soil carbon is not a straightforward matter; it is made complex by the relative activity of soil biota, which can consume and release carbon and are made more active by the addition of

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

fertilizer A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...

Data available on soil organic carbon

SRS1000 being used to measure soil respiration in the field

=Europe

= The most homogeneous and comprehensive data on the organic carbon/matter content of

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

an soils remain those that can be extracted and/or derived from the European Soil Database in combination with associated databases on land cover, climate, and

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

. The modelled data refer t
carbon content (%) in the surface horizon
of soils in Europe. In an inventory on available national datasets, seven

member states of the European Union The European Union (EU) is a political and economic union of 27 member states that are party to the EU's founding treaties, and thereby subject to the privileges and obligations of membership. They have agreed by the treaties to share their o ...

have available datasets on organic carbon. In the article "Estimating soil organic carbon in Europe based on data collected through a European network" (''Ecological Indicators'' 24, pp. 439–450), a comparison of national data with modelled data is performed. The LUCAS soil organic carbon data are measured surveyed points and the aggregated results at regional level show important findings. Finally, a new proposed model for estimation of soil organic carbon in agricultural soils has estimated current to
SOC stock of 17.63 Gt
in EU agricultural soils. This modelling framework has been updated by integrating the soil erosion component to estimate the lateral carbon fluxes. Currently, the EU-ORCaSA project is developing a multi-ecosystem framework for measuring, reporting and verification of soil organic carbon changes to support policy making.

Managing for catchment health

Much of the contemporary literature on soil carbon relates to its role, or potential, as an atmospheric

to offset

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

. Despite this emphasis, a much wider range of soil and catchment health aspects are improved as soil carbon is increased. These benefits are difficult to quantify, due to the complexity of

natural resource Natural resources are resources that are drawn from nature and used with few modifications. This includes the sources of valued characteristics such as commercial and industrial use, aesthetic value, scientific interest, and cultural value. ...

systems and the interpretation of what constitutes soil health; nonetheless, several benefits are proposed in the following points: *Reduced

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to th ...

: increased soil aggregate stability means greater resistance to erosion; mass movement is less likely when soils are able to retain structural strength under greater moisture levels. *Greater productivity: healthier and more productive soils can contribute to positive socio-economic circumstances. *Cleaner

waterway A waterway is any Navigability, navigable body of water. Broad distinctions are useful to avoid ambiguity, and disambiguation will be of varying importance depending on the nuance of the equivalent word in other ways. A first distinction is ...

s, nutrients and

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and wa ...

: nutrients and sediment tend to be retained by the soil rather than leach or wash off, and are so kept from waterways. *

Water balance The law of water balance states that the inflows to any water system or area is equal to its outflows plus change in storage during a time interval. In hydrology, a water balance equation can be used to describe the flow of water in and out of ...

: greater soil water holding capacity reduces overland flow and recharge to

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

; the water saved and held by the soil remains available for use by plants. *Climate change: Soils have the ability to retain carbon that may otherwise exist as atmospheric CO₂ and contribute to

global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

. *Greater

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

: soil organic matter contributes to the health of soil flora and, accordingly, the natural links with biodiversity in the greater

biosphere The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...

Forest soils

Forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

soils constitute a large pool of carbon. Anthropogenic activities such as

deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...

cause releases of carbon from this pool, which may significantly increase the concentration of

greenhouse gas Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...

(GHG) in the

. Under the

United Nations Framework Convention on Climate Change The United Nations Framework Convention on Climate Change (UNFCCC) is the UN process for negotiating an agreement to limit dangerous climate change. It is an international treaty among countries to combat "dangerous human interference with th ...

(UNFCCC), countries must estimate and report GHG emissions and removals, including changes in carbon stocks in all five pools (above- and below-ground biomass, dead wood, litter, and soil carbon) and associated emissions and removals from land use, land-use change and forestry activities, according to the

Intergovernmental Panel on Climate Change The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to "provide governments at all levels with scientific information that they can use to develop climate policies". The World Met ...

's good practice guidance. Tropical deforestation represents nearly 25% of total anthropogenic GHG emissions worldwide. Deforestation, forest degradation, and changes in land management practices can cause releases of carbon from soil to the atmosphere. For these reasons, reliable estimates of soil organic carbon stock and stock changes are needed for Reducing emissions from deforestation and forest degradation and GHG reporting under the UNFCCC. The government of

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

—together with the

Food and Agriculture Organization of the United Nations The Food and Agriculture Organization of the United Nations; . (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition and food security. Its Latin motto, , translates t ...

and the financial support of the government of

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

—have implemented a forest soil carbon monitoring program to estimate soil carbon stock, using both survey and modelling-based methods. West Africa has experienced significant loss of forest that contains high levels of soil organic carbon. This is mostly due to expansion of small scale, non-mechanized agriculture using burning as a form of land clearance

References

{{DEFAULTSORT:Soil Carbon Carbon Land management

Carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

Soil science