In hydrology

Hydrology

Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

, stemflow is the flow of intercepted

Interception (water)

Interception refers to precipitation that does not reach the soil, but is instead intercepted by the leaves and branches of plants and the forest floor. It occurs in the canopy , and in the forest floor or litter layer...

 water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 down the trunk

Trunk (botany)

In botany, trunk refers to the main wooden axis of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the...

 or stem of a plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

. Stemflow, along with throughfall

Throughfall

In Hydrology, throughfall is the process which describes how wet leaves shed excess water onto the ground surface. These drops have an erosive power because they are larger than rain drops, however, if they travel a shorter distance their erosive power is reduced...

, are responsible for the transferral of precipitation

Precipitation (meteorology)

In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 and nutrient

Nutrient

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s from the canopy to the soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

. In tropical rainforest

Tropical rainforest

A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

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

Gully

A gully is a landform created by running water, eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width...

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

Temperate

In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 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

Bisection

In geometry, bisection is the division of something into two equal or congruent parts, usually by a line, which is then called a bisector. The most often considered types of bisectors are the segment bisector and the angle bisector In geometry, bisection is the division of something into two equal...

 PVC

Polyvinyl chloride

Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...

 or other plastic tubing

Pipe (material)

A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...

 around the circumference

Circumference

The circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....

 of the tree trunk, connected and funneled into a graduated cylinder

Graduated cylinder

A graduated cylinder, measuring cylinder or graduate is a piece of laboratory equipment used to accurately measure the volume of a liquid. Water displacement can be used to find out the volume of a solid. Graduated cylinders are generally more accurate and precise for this purpose than flasks and...

 for manual or a tipping bucket rain gauge 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

Meteorology

Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

 characteristics of a rain

Rain

Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

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
  Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...
  
  ; this is also governed by air temperature, relative humidity
  Relative humidity
  Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
  
   and most significantly, wind speed
  Wind speed
  Wind speed, or wind velocity, is a fundamental atmospheric rate.Wind speed affects weather forecasting, aircraft and maritime operations, construction projects, growth and metabolism rate of many plant species, and countless other implications....
  
  
• 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
  Crown closure is a term used in forestry.Crown closure, also known as canopy cover, crown cover, or canopy closure, is defined as the percent of canopy overlying the forest floor...
  
  

Species

The species of the tree affects the amount of timing and stemflow. The particular morphological

Plant morphology

Plant morphology or phytomorphology is the study of the physical form and external structure of plants. This is usually considered distinct from plant anatomy, which is the study of the internal structure of plants, especially at the microscopic level...

 characteristics that are key factors are:

• Crown size – stemflow potential is greater as crown size
  Crown (botany)
  The crown of a plant refers to the totality of the plant's aboveground parts, including stems, leaves, and reproductive structures. A plant canopy consists of one or more plant crowns growing in a given area....
  
   relative to the diameter at breast height
  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....
  
   increases
• Leaf shape/orientation – leaves
  Leaf
  A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
  
   which are concave and elevated horizontally above the petiole
  Petiole (botany)
  In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
  
   are able to contribute to stemflow
• Branch angle – stemflow potential heightens as the angle of the branch
  Branch
  A branch or tree branch is a woody structural member connected to but not part of the central trunk of a tree...
  
  es and twig
  Twig
  A twig is a small thin terminal branch of a woody plant. Twigs are critically important in identification of trees, shrubs and vines, especially in wintertime. The buds on the twig are an important diagnostic characteristic, as are the abscission scars where the leaves have fallen away...
  
  s increases
• Flow path obstructions – abnormalities on the flow path, such as detached pieces of bark
  Bark
  Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
  
   or scars, on the underside of the branch can divert water from stemflow and become a component in throughfall
  Throughfall
  In Hydrology, throughfall is the process which describes how wet leaves shed excess water onto the ground surface. These drops have an erosive power because they are larger than rain drops, however, if they travel a shorter distance their erosive power is reduced...
  
  
• Bark – stemflow is affected by the degree of absorptive ability and smoothness of the bark
  Bark
  Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
  
   alongside the branch and stem

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
  Understory
  Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
  
   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
  Deciduous
  Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
  
   or mixed forests
  Temperate broadleaf and mixed forests
  Mixed forests are a temperate and humid biome. The typical structure of these forests includes four layers. The uppermost layer is the canopy composed of tall mature trees ranging from 33 to 66 m high. Below the canopy is the three-layered, shade-tolerant understory that is roughly 9 to...
  
  , 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
  [Image:Dew on a flower.jpg|right|220px|thumb|Some dew on an iris in Sequoia National Park]]Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening...
  
  ) and lighter in the afternoon

Influence on soil

Chemistry

Nutrient

Nutrient

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s that have accumulated on the canopy from dry deposition

Deposition (Aerosol physics)

In aerosol physics, Deposition is the process by which aerosol particles collect or deposit themselves on solid surfaces, decreasing the concentration of the particles in the air. It can be divided into two sub-processes: dry and wet deposition. The rate of deposition, or the deposition velocity,...

 or animal feces

Feces

Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

 are able to directly enter the soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 through stemflow. When precipitation occurs, canopy nutrients are leached

Leaching (chemical science)

Leaching is the process of extracting minerals from a solid by dissolving them in a liquid, either in nature or through an industrial process. In the chemical processing industry, leaching has a variety of commercial applications, including separation of metal from ore using acid, and sugar from...

 into the water because of the differences in nutrient concentration 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 epiphyte

Epiphyte

An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...

s or lichen

Lichen

Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...

s also contributes to uptake. The nutrients that enter the soil can also reflect the particular environmental conditions around them, for example, plants located in industrialized

Industrialisation

Industrialization is the process of social and economic change that transforms a human group from an agrarian society into an industrial one...

 areas exhibit higher rates of sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 and nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 (from air pollution

Air pollution

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

), whereas those located near the ocean

Ocean

An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

s have higher rates of sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 (from seawater

Seawater

Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

).

Precipitation and morphological factors that influence stemflow timing and volume also affect the chemical composition; in general, stemflow water becomes more dilute

Concentration

In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...

 during the course of a storm event, and rough-barked species contain more nutrients than smooth-barked species.

Water distribution

In forest

Forest

A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

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

Topsoil

Topsoil is the upper, outermost layer of soil, usually the top to . It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.-Importance:...

 into deeper layers of the soil horizon

Soil horizon

A soil horizon is a specific layer in the land area that is parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath. Horizon formation is a function of a range of geological, chemical, and biological processes and occurs over long time...

 along tree root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s and their subsequent creation of macropore

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, allowing water to infiltrate and drain quickly,...

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

Landslide

A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

s.

See also

• Throughfall
  Throughfall
  In Hydrology, throughfall is the process which describes how wet leaves shed excess water onto the ground surface. These drops have an erosive power because they are larger than rain drops, however, if they travel a shorter distance their erosive power is reduced...
  
  
• Canopy interception
  Interception (water)
  Interception refers to precipitation that does not reach the soil, but is instead intercepted by the leaves and branches of plants and the forest floor. It occurs in the canopy , and in the forest floor or litter layer...