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Glossary for agroforestry

Compiled and edited by Peter Huxley and Helen van Houten, International Centre for Research in Agroforestry - 1997

tannin

    An astringent substance, available naturally in the bark (and sometimes the wood) of different species of trees (for example, acacia and mangrove species); used in converting hide to leather. A polyphenol.

taper

    The decrease in thickness, generally in terms of diameter, of a tree stem or log from the base up. See also tree form

taproot

    1. Main root, leaving the collar in the opposite direction from the stem and growing more powerfully than the secondary roots. See also sink root

    2. Primary root that persists and maintains its dominance; often swollen and providing for storage.

target area

    Large priority development area in a country for which improved cropping system technologies are developed through on-farm cropping systems research conducted at sites in the area.

taungya system

    Method of raising forest trees in combination with (seasonal) agricultural crops. Used in the early stages of establishing a forest plantation. It not only provides some food but can lessen the establishment costs.

taxon

    A taxonomic unit of any size. A category in the taxonomic hierarchy.

taxonomy

    Classification of organisms, including identification and nomenclature, according to a natural (chiefly morphological) system that seeks to depict evolvement. Hence taxon, any designated group within a classification (for example, a cultivar, a species)

technology

    See practice

temporal complementarity

    See complementarity

tendril

    A slender, coiling, modified leaf or stem of climbing plants, such as peas, that supports the plant by attaching it to surrounding surfaces.

terrace

    A broad surface running along the contour. It can be a natural phenomenon or specially constructed to intercept runoff, thereby preventing erosion or conserving moisture. Terraces are sometimes built to provide adequate rooting depths for plants. See also broad-based terrace, ridge terrace

terrace cropping

    Sowing crops on terraces.

tetraploid

    See polyploid

thermal duration

    See thermal time

thermal time

    1. The time–temperature integral above a specified 'base temperature'; usually for a set of processes (for example, growth from sowing to harvest) if individual processes have the same base temperature. See also cumulative temperature

    2. The integral of time and temperature in degree-days needed for the completion of a particular development process.

thermograph

    A self-recording thermometer.

therophyte

    A self-supporting annual (or seasonal) plant whose shoot and root systems die after seed production and which completes its whole life cycle within one year (season).

thicket

    1. A number of trees or shrubs growing close together. See also brush

    2. A closed stand of bushes and climbers between 3 and 7 metres tall.

thinning

    Removal of some of the plants from a crop, or immature trees from a forest, to improve growth of the remainder. See also line thinning, mechanical thinning, selective thinning

thinning out

    A type of pruning operation in which entire shoots are removed. An extension of, or complement to, heading back.

throughfall

    The proportion of the gross precipitation that reaches the ground and is not intercepted by, or retained in, the canopy. See also intercepted rainfall, stemflow

tie ridging

    In contour furrowing or trenching, a narrow transverse strip of ground left unexcavated (or ridged).

tillage

    Soil-stirring action to loosen soils and so benefit crops by supplying a suitable soil environment for seed germination and root growth and for weed control. See also minimum tillage, no-tillage, zero tillage

tiller

    1. A branch that arises at soil level; usually restricted to the grasses.

    2. Secondary stems that arise from basal axillary or adventitious buds in grasses. See also adventitious structure

tilth

    1. The physical state of soil that determines its suitability for plant growth. It takes into account soil structure, soil texture, consistency and pore space. It is a subjective estimation, judged by experience.

    2. The physical condition of soil in terms of its ease of tillage, fitness as a seedbed and lack of impedence to seedling emergence and root penetration.

timber

    The wood product of a tree obtained by sawing and milling. Timber is a major product of forests. It differs from poles or roundwood only in that it is cut. See also lumber

timberbelt

    See windbreak

timber height

    The height of a tree to the point at which the stem breaks into branches (the 'crown spring') or to the point at which the diameter of the stem is 7 cm over bark, whichever is reached first. On a felled tree this point is called the 'timber point'.

tissue culture

    Cellular mass grown in vitro on solid medium or supported and nurtured with liquid medium; cells are in protoplasmic continuity.

top down

    Description of research strategies and methodologies in which research planners or officials make programming decisions without the participation or contribution of individuals at other levels of involvement, particularly the target population. See also bottom up

top height

    In theory, the average height of the hundred trees of largest diameter per hectare. In practice, it is the average height of a sample of the largest diameter trees.

topoclimate

    The climate at 'a place'. Usually considered to encompass larger spatial dimensions than microclimate (for example, the climate around plants), and smaller than macroclimate (for example, of regions), so would cover a 'field' or a 'slope', or similar area.

topography

    A description of the features of a place, or a landscape, especially the rise and fall of the land. On a map it is usually indicated by contour lines.

topophysis

    The long persistence of non-genetic, position or age effects after grafting or rooting. Examples are the horizontal growth of grafted trees produced with scions taken from plagiotropic branches and the early flowering of grafted trees produced from flower-producing branches. See also plagiotropic branching

toposequence

    A sequence of related soils that differ from one another, primarily because of topography as a soil formation factor. See also catena

topsoil

    The upper layer of soil rich in organic matter. It forms naturally but is easily lost through disturbance. See also subsoil

total area

    A spatial unit suggested to embrace agriculture, horticulture, forestry and agroforestry. The complete land area being managed by a single land user (or cooperating group). In agriculture, it is 'the farm'.

total exchange capacity

    See cation exchange capacity

total factor productivity

    See production function

trace element

    See micronutrient

trait

    A characteristic of a plant, a group of plants, or part of a plant. Traits may be attributes (quantitative values such as alive/dead or diseased/healthy) or variables (quantitative values such as 'diameter at breast height' or 'basal area').

transhumance

    A situation in which farmers with a permanent place of residence send their herds, tended by herdsmen, for long periods of time to distant grazing areas. See also nomadism, pastoralism

transition zone

    Of a dicotyledenous stem, the part of the main stem where the anatomy changes from that of a root (vascular strands  with internal primary xylem) to that of a stem (with external primary xylem).

translocated herbicide

    A herbicide that, after uptake, is moved within the plant and can affect parts of the plant remote from the point of application. See also systemic, contact herbicide

transpiration efficiency

    See dry matter to transpiration ratio

transpiration ratio

    See water-use ratio

transplant

    1.  A plant that has undergone the process of transplanting, as differentiated from a seedling or cutting, which has not. In a forest nursery, seedlings are normally transplanted after one or two years in the seedbed so as to develop a better root system and a sturdier plant.

    2.  To take a tree or plant from one location and plant it in another. Transplanting happens in many forms: with seedlings in pots, with open-rooted seedlings, balled-root seedlings and with stumps. See also balled roots, open rooted, pricking out

transplant lines

    Juvenile shrubs and trees planted in nurseries from seedlings or rooted cuttings, to reach acceptable size for planting elsewhere.

trap crop

    A plant species that provides favourable conditions for certain pests and so is grown before or concurrently with but adjacent to the main crop to attract the pests so that they can be suitably eliminated (for example, with insecticides).

treatment

    Any method, procedure, or regime that is applied to some of the experimental units (plots) to compare its effects with those of other treatments. The term includes control and control treatment.

tree

    1. A woody plant that produces one main trunk or bole and a more or less distinct and elevated head.

    2. A woody plant having one well-defined stem and a more or less definitely formed crown and roots, usually attaining a height of at least 2½ metres. See also bush, shrub

tree–crop interface

    The spatial extent, above and below ground, over which some form of competition and or facilitation occurs between the tree and the crop components in an agroforestry system. See also intimacy

tree farming

    Any agroforestry practice that incorporates trees into farmland. See also farm forestry

tree form

    The degree and mode of taper in a tree or log. Also loosely applied to the general shape of the bole and its desirability for use.

tree garden

    A multistoreyed agroforestry system in which a mixture of several fruit and other useful trees is cultivated (that is, for a mixture of products), sometimes with the inclusion of annual crops. See also homegarden, mixed garden, village forest garden

tree height

    The vertical distance between the extreme top of a standing tree (even if this is a lateral shoot) and ground level, using the upper side on slopes.

tree temperament

    The set of growth and development reactions shown towards its environment by a tree species during its whole life cycle. See, for example, climax species and pioneer.

trial

    1. Another word for 'experiment'. Often used in applied adaptive field research.

    2. An action, method or treatment adopted to ascertain a result. It may be part of a larger 'investigation', and is usually of a shorter or less significant involvement than an 'experiment'.

trickle irrigation

    The process of supplying water to plants using equipment that drips small quantities at a slow rate. Water is usually applied at positions determined by the location of the nozzles although, in some systems (for example, 'seep hose'), it comes from all along the feeder line. Can be above ground or subsurface. Also called drip irrigation.

triploid

    See polyploid

truncate

    To cut off at the end.

trunk

    The main stem of a tree. See also bole

tuber

    1. A greatly swollen underground shoot or stem, generally irregular in shape, which acts as a store of nutrients.

    2. A specialized stem; the enlarged fleshy tip of an underground stem.

turf

    The leafy shoot sytem together with the upper part of the roots cut and lifted (for relaying) from a grassy sward. Hence a 'turfed' area. See also sod

turgor pressure

    See leaf water potential

twig

    Stem one year old or less. Usually applied to a stem not including the leaves

twiner

    Plants that climb by having stem apices that nutate (oscillate and wind) around slender supports. See also root climber, scrambler

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College of Agricultural and Environmental Sciences and Warnell School of Forest Resources
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