hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...

, stemflow is the flow of intercepted

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

down the trunk or stem of a

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

. Stemflow, along with

throughfall In Hydrology, throughfall is the process which describes how wet leaves shed excess water onto the ground surface. These drops have greater erosive power because they are heavier than rain drops. Furthermore, where there is a high canopy, falling ...

, is responsible for the transferral of

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

and

nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s from the

canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an ...

to the

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

. In

tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...

s, where this kind of flow can be substantial, erosion

gullies A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble lar ...

can form at the base of the trunk. However, in more

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

climates stemflow levels are low and have little erosional power.

Measurement

There are a variety of ways stemflow volume is measured in the field. The most common direct measurement currently used is the bonding of bisected PVC or other

plastic tubing Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...

around the

circumference In geometry, the circumference (from Latin ''circumferens'', meaning "carrying around") is the perimeter of a circle or ellipse. That is, the circumference would be the arc length of the circle, as if it were opened up and straightened out to ...

of the tree trunk, connected and funneled into a

graduated cylinder A graduated cylinder, also known as a measuring cylinder or mixing cylinder, is a common piece of laboratory equipment used to measure the volume of a liquid. It has a narrow cylindrical shape. Each marked line on the graduated cylinder represent ...

for manual or a

tipping bucket rain gauge A rain gauge (also known as udometer, pluvia metior, pluviometer, ombrometer, and hyetometer) is an instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a predefined area, over a period ...

for automatic collection. At times the tubing is wrapped multiple times around the trunk is order to ensure more complete collection.

Determining factors

Precipitation The primary meteorological characteristics of a

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

fall event that influence stemflow are: * ''Rainfall continuity'' – the more frequent and extended are the gaps during the event where no rainfall occurs, the higher the likelihood that potential stemflow volume is lost to

evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpi ...

; this is also governed by

air temperature Atmospheric temperature is a measure of temperature at different levels of the Earth's atmosphere. It is governed by many factors, including insolation, incoming solar radiation, humidity and altitude. When discussing surface air temperature, the ...

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

and most significantly,

wind speed In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer. Wind speed ...

* ''Rainfall intensity'' – the amount of total stemflow is diminished when the amount of rain in a given period surpasses the capacity of the flow paths * ''Rain angle'' – stemflow generally starts earlier when rainfall is more horizontal; this is more of a determinant in an open forest with a lesser degree of

crown closure Crown closure, in forestry, is a measure of forest canopy coverage. Crown closure and crown cover are two slightly different measures of the forest canopy and that determine the amount of light able to penetrate to the forest floor. Crown closu ...

Species

The species of the tree affects the amount of timing and stemflow. The particular morphological characteristics that are key factors are: * ''Crown size'' – stemflow potential is greater as crown size relative to the

diameter at breast height Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements. Tree trunks are measured at the height of an adult's breast, ...

increases. However, the greater the DBH, the more incident rainfall is needed to start stemflow. * ''Leaf shape/orientation'' –

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

which are

concave Concave or concavity may refer to: Science and technology * Concave lens * Concave mirror Mathematics * Concave function, the negative of a convex function * Concave polygon, a polygon which is not convex * Concave set * The concavity In ca ...

and elevated horizontally above the petiole are able to contribute to stemflow * ''Branch angle'' – stemflow potential heightens as the angle of the

branch A branch, sometimes called a ramus in botany, is a woody structural member connected to the central trunk (botany), trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term '' ...

es and

twig A twig is a thin, often short, branch of a tree or bush. The buds on the twig are an important diagnostic characteristic, as are the abscission scars where the leaves have fallen away. The color, texture, and patterning of the twig bark are ...

s in relation to the trunk decreases. * ''Flow path obstructions'' – abnormalities on the flow path, such as detached pieces of bark or scars, on the underside of the branch can divert water from stemflow and become a component in

* ''Bark'' – stemflow is affected by the degree of absorptive ability and smoothness of the bark alongside the branch and stem. This is measured by using the Bark Relief Index, or BRI, which is the difference between the circumfrence of the tree and what the circumfrence would be if the tree had no bark. Stand characteristics In addition to the effects of individual tree species, the overall structure of the forest stand also influences the amount of stemflow that will ultimately occur, these factors are: * ''Species composition'' – the total stemflow for the stand is determined by the contributions of individuals and their species-specific traits * ''Stand density'' – morphological characteristics such as branch angle and thickness are largely determined by the amount of density of competing trees in the stand * ''Canopy structure'' – individuals located in the

understory In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abov ...

in a stand with multiple vertically-stratified stories will have a lessened amount of total stemflow due to the interception of dominant and codominant individuals Other * ''Seasonality'' – in the case of

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

mixed forests Temperate broadleaf and mixed forest is a temperate climate terrestrial habitat type defined by the World Wide Fund for Nature, with broadleaf tree ecoregions, and with conifer and broadleaf tree mixed coniferous forest ecoregions. These fo ...

, stemflow rates are ''slightly'' higher in the dormant season when no leaves are present and evapotranspiration is reduced; this effect becomes more pronounced as the stem diameter increases * ''Diurnality'' – variations in branch weight influence the amount of stemflow; branches are heavier in the morning (with

dew Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation. As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at wh ...

) and lighter in the afternoon

Influence on soil

Chemistry

Nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s that have accumulated on the canopy from dry deposition or animal

feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

are able to directly enter the

through stemflow. When precipitation occurs, canopy nutrients are leached into the water because of the differences in nutrient

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...

between the tree and the rainfall. Conversely, nutrients are taken up by the tree when concentration is lower in the canopy than the rainfall, the presence of epiphytes or

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.industrialized Industrialisation ( alternatively spelled industrialization) is the period of social and economic change that transforms a human group from an agrarian society into an industrial society. This involves an extensive re-organisation of an econo ...

areas exhibit higher rates of

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

and

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

(from

air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...

), whereas those located near the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

s have higher rates of

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

(from

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...

Soil acidification Soil acidification is the buildup of hydrogen cations, which reduces the soil pH. Chemically, this happens when a proton donor gets added to the soil. The donor can be an acid, such as nitric acid, sulfuric acid, or carbonic acid. It can also be a ...

can be seen around some stems, for example beech trees from dry deposition. Deposition and soil leaching in stands of Norway spruce and European Beech: Results from the Höglwald research in comparison with other European case studies
/ref> Precipitation and morphological factors that influence stemflow timing and volume also affect the chemical composition; in general, stemflow water becomes more dilute during the course of a storm event, and rough-barked species contain more nutrients than smooth-barked species. Water distribution In

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

ed areas, water is more able to effectively penetrate past the

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 matt ...

into deeper layers of the

soil horizon A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...

along tree

root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...

s and their subsequent creation of

macropore In soil, macropores are defined as cavities that are larger than 75 μm. Functionally, pores of this size host preferential soil solution flow and rapid transport of solutes and colloids. Macropores increase the hydraulic conductivity of soil ...

s (termed ''preferential flow''). The loosening of the soil can result in minor

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...

References

{{reflist Hydrology Forest ecology

Measurement

Determining factors

Influence on soil

See also

References