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Glossary for agroforestry

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

backcross

    1. A cross of a hybrid to either of its parents. In genetics, a cross of a heterozygote to a homozygous recessive.

    2. The cross of a hybrid to one of its parental types; a method of incorporating traits into otherwise adapted cultivars. May include multiple crosses to a recurring parental cycle.

backcross breeding method

    A breeding method of improving plant characteristics in a stepwise fashion where previous gains are not lost. It is rapid, requires a small number of plants, and is predictable. Its major limitation is that it does not permit the achievement of unusual combinations of genes from two or more varieties.

badlands

    Steep, barren land, usually broken by narrow channels, sharp crests and pinnacles resulting from serious and rapid erosion. Most common in dry areas.

balled roots

    Lifted seedlings with a ball of earth attached to the roots. See also bare-rooted planting, undercut seedling

bamboo

    A vegetation type consisting of woody graminaceous species from the subfamily Bambusoideae. Found as dense thickets or forestin the high-altitude tropics that have only a sparse ground cover of herbs, grasses, mosses and ferns. Sometimes also in the lowlands.

band application

    Application of a fertilizer, herbicide, or similar treatment as a strip, normally straddling or adjacent to the crop row (as opposed to overall application).

bare-rooted planting

    Planting of seedlings without soil on roots (syn: open-rooted seedlings). See also balled roots, undercut seedling

bark

    The stem tissue outside the vascular cambium.

bark storage factor

    See stemflow

barrier hedge

    A hedge planted so as to prevent runoff. See also contour hedge

basal area

    The area of the cross-section of a stem at breast height (1.3 m above ground level). The basal area of a wood is the sum of the basal areas of the trees composing it.

basal burl

    A woody organ with a proliferation of dormant buds, formed by the uniform expansion of the base of a stem because of increased cambial activity.

base exchange capacity

    See cation exchange capacity

base saturation

    1. Ratio of base (Ca, Mg, K, Na) extracted from the soil by an extraction agent to the capacity of the soil to hold extractable bases; expressed as a percentage.

    2. The extent to which the exchange sites of a material are occupied by exchangeable basic cations; expressed as a percentage of the cation exchange capacity.

    3. The extent to which the adsorption complex of a soil is saturated with exchangeable cations other than hydrogen and aluminium; it is expressed as a percentage of the total cation-exchange capacity.

base temperature

    The temperature from which the rate of development of a plant organ increases more or less linearly as temperature increases up to an optimum temperature, above which the rate of development decreases. Base temperatures need to be determined by experiment. See also cumulative temperature, thermal time

beating up

    Restocking failed areas in a crop or stand by further sowings or plantings. Many other terms are also used for this, for example, 'blanking', 'filling', 'gapping', 'infilling', 'recruiting', 'reinforcement planting'

bench terrace

    A shelflike embankment of earth with a level top and a steep or vertical downhill face, constructed along the contour of sloping land to control run-off and erosion. Types are the horizontal bench terrace, which has no measurable slope from the back to the front of the bench, and the sloping bench terrace, which has a significant slope from the back to the front of the bench. Contrast with ridge terrace. See also gradoni bench

benefit–cost ratio benefit

    The present value of benefits divided by the present value of costs. In economics, goods or a  service (outputs) that increases the income of families or firms or that increases the national income of the society.

B horizon

    A soil horizon usually beneath the A horizon that is characterized by one or more of the following: (1) a concentration of silicate clays, iron and aluminium oxides, and humus, alone or in combination; (2) a blocky or prismatic structure, and (3) coatings of iron and aluminium oxides that give darker, stronger or redder colour.

bias

    1. Any operation that allows a particular treatment or replication to be favoured or handicapped by some extraneous source of variation. An unwanted property of the sampling procedure.

    2. A systematic discrepancy between an estimate of any quantity (from measurements) and its true value.

biennial

    1. A plant that ordinarily requires two years, or at least part of two seasons, with a dormant period between growth stages, to complete its life cycle.

         2. A plant that flowers only in the year following that in which it germinates from seed.

biocoenosis

    An association of organisms forming a community. Their relationship.

biodiversity

    The level of abundance of life forms co-existing in a given environment.

biogas

    Gas generated by the anaerobic fermentation of organic matter (dung, plant residues, and so on). It consists of some 60–70% methane. As a renewable energy source, it can be used for heating, lighting and, with suitable adaptation, as fuel for internal combustion engines.

biological control

    1. Using living organisms to reduce populations of pest organisms.

    2. Any of a wide variety of substances or methods used in pest control that emphasize the use of living organisms or products derived directly from them.

biological determinant

    A biological factor such as crop species, variety, weeds, insect pests or disease that determines the crop configuration and performance of a cropping pattern at a given site.

biomass

    Strictly, the quantity of biological matter present on a unit area; may be 'total' or often only 'above-ground'. May be separated into plant and animal mass, or further divided into the mass of standing crop, or the tree portion of a stand, and then into foliage, branch, stem, flowers, and so on.

biota

    The flora and fauna of a defined area or volume (for example, soil biota in the topsoil).

biotic

    The influence of animals and plants on associated plant or animal life as contrasted with climatic influences and edaphic (soil) influences. See also abiotic

biotope

    1. Non-living components that support the biocoenosis of an ecosystem (more or less equivalent to habitat).

    2. The area of relatively uniform environmental conditions and biotypes (living organisms) that are adapted to them.

biotype

    1. A group of individuals in nature, all with essentially the same genetic constitution. A species consists of several biotypes.

    2. A group of individuals with the same genotype. Biotypes may be homozygous or heterozygous.

blanking

    See beating up

block

    1. A set of experimental units under treatment or observation, which have been grouped to minimize environmental effects or initial differences between units in respect of the variables being studied, for example, a set of contiguous or non-contiguous experimental plots initially giving the same experimental response.

    2. In forestry, the primary subdivision and major territorial unit of a forest estate, generally bounded by natural features. It is divided into compartments.

bole

    1. Tree stem once it has grown to substantial thickness, capable of yielding timber or large poles.

    2. The trunk of a tree. It may extend to the top of the tree as in some conifers, or it may be lost in the ramification of the crown, as in deciduous species (syn: stem, trunk).

bolting

    1. Developmental process in which rosetted plants (biennials) produce a flower stalk and seed and then die before the end of the season.

    2. Colloquial term in English for premature flowering; when biennial plants come into flower early or when not required to do so.

bottom-up

    In contrast to the top-down approach to research and development. A bottom-up approach emphasizes the participation of the targeted groups and populations in making programming and research decisions. See also top-down

Bowen ratio

    At a water surface, the ratio of the energy flux upwards as sensible heat to the energy flux used in evaporation.

bract

    A much-reduced leaf, particularly the small or scalelike leaves in a flower cluster or associated with flowers; morphologically a foliar organ.

branch

    Lateral portion of the shoot that originates from the trunk or from another branch and gives rise to shoots, twigs and leaves.

branching

    See dimorphic branching, orthotropic branching, plagiotropic branching

breast height

    1. The standard height at which the diameter of the stem of a standing tree is measured: 1.3 metres above ground level.

    2. By international agreement (through the International Union of Forest Research Organizations), 1.3 m from ground level, at which height the girth or diameter of trees are commonly measured. (Note: l.37 m is used in some parts of the world.)

breeding

    The selection and propagation of particular genotypes, to achieve certain objectives (higher yield, disease resistance, and so forth). May be the result of manipulation (crossing) or through artificially induced mutation. Plant species or varieties may be strictly or mainly inbreeding or outbreeding in their natural environment.

breeding system

    The natural processes by which sexual union occurs, including cytogenetic, morphological and physiological structures and processes. It includes the pollination system (wind, insects, self-pollination, and so forth). See also inbreeding and outbreeding

broad-based terrace

    A ridge-type terrace 25–50 cm high and 4–10 m wide with gently sloping sides, a rounded crown and a dish-shaped channel along the upper side, constructed to control erosion by diverting runoff along the contour at a non-scouring velocity. It may be level or have a grade towards one or both ends. See also terrace, ridge terrace

broadleaved

    Trees other than conifers that have (usually but not always) flat, broad leaves. Ovules are found in an ovary, and all reproductive organs appear in flowers. They belong to the angiosperm group of plants.

brown forest soils

    Intrazonal and calcimorphic; formed on calcium-rich parent materials under deciduous forest and possessing a high base status but lacking a pronounced illuvial horizon.

browse

    Leaves, small twigs and shoots of shrubs, seedling and sapling trees, and vines available for forage for livestock and wildlife.

browsing

    The feeding on the above-ground parts of trees and shrubs (buds, shoots and leaves) by livestock or wild animals.

brush

    1. Undergrowth, often of a thicket and including the small trees and shrubs.

    2. Material such as twigs cut from undergrowth.

brushing

    The removal of lower branches on a tree to facilitate access, for example in closely spaced coniferous plantations.

bud

    Dormant and unelongated stem composed of a short axis of meristem cells from which embryonic leaves, lateral buds, flower parts or all three arise.

budding

    1. The use of a bud for grafting.

    2. A technique used to obtain new fruit trees with the same characteristics as those already producing good quality fruit in quantity. A bud is cut from a mother tree scion and spliced into the bark of a young seedling or clonnaly produced rootstock.

    3. A method of vegetative propagation of plants by implantation of buds from the mother plant into a rootstock.

    4. Grafting by inserting a bud with a small amount of attached bark or stem tissue into a cut in the bark of the rootstock.

budwood

    See scion

buffer

    1. In biological systems, to regulate against changes.

    2. A substance that prevents a rapid change in pH when acids or alkalis are added to the soil; these include clay, humus and carbonates.

buffer action

    The action of ionizable molecules in equilibrum with ions in solution in reducing pH variations that result from additions of acids, N bases, changes of concentration of a solution, and so on. The effect is to stabilize pH.

buffer zone

    An area around a forest, national park, or any other conserved place that provides the local community with products that they would otherwise take from the forest, or that provides an opportunity to produce alternative products.

bulk breeding

    The growing of genetically diverse populations of self-pollinated crops in a bulk plot, with or without mass selection, followed by single-plant selection.

bulk density

    1. Mass of dry soil per unit volume. Bulk volume determined before drying to constant weight at 105°C. Usually expressed in g ml –1.

    2. Of soil weight per unit volume.

bulk population breeding method

    A breeding method in which two known plants are crossed and the resulting seeds are sown together so that natural selection can then weed out weaker combinations while new combinations are created in the original stand.

bulk progeny test

    A test of the offspring of parents that have been grouped according to phenotypic similarity and in which the identity of the offspring is maintained only for groups of parents.

bund

    1. A barrier on the surface of the soil on sloping land to prevent runoff and soil erosion.

    2. The arrangement of organic material, for example, agricultural waste or soil, in lines along the contours of a slope, to control runoff or erosion.

burn

    Setting fire ('firing') forest, woodland or rangeland (1) in forestry, to dispose of the slash left after forest clearing or, (2) in rangeland, to burn off old, inedible plant materials and to encourage a flush of new grass for animals to graze. It is important in which part of the dry season the burning is done, as it influences the amount to be burned and its condition, as does, for the latter, the time of day and the weather. See also fire

bush

    1. A general term for low tree–high grass vegetation occurring in semi-arid or seasonally arid regions. Can be further described by the dominant species present, for example, 'acacia bush', 'combretum bush'.

    2. A low, well-branched shrub.

bush fallow

    The natural vegetation that arises when land is left uncultivated for some time. Composed of small trees, shrubs, grasses (and sedges) and herbaceous plants. Bush fallow may be grazed or browsed and firewood collected from it before it is returned to cultivation. See also enriched fallow, shifting cultivation

bushland

    An open stand of bushes, 3–7 m high, with a canopy cover > 40%.

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