Glossary for agroforestry

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

abiotic

Relating to things that are not alive. Used to describe the physical attributes of a land-use system (for example, soil, climate). See also biotic

abscission

Natural separation of leaves, flowers and fruits from plants. Generally associated with deterioration of a specialized layer of thin-walled cells.

absolute growth rate

The rate of change in plant material (dry weight) per unit of time. See also relative growth rate

absolute humidity

The ratio of the mass of water vapour present to the volume occupied by the mixture, that is the density of the water-vapour component. See also dew point, mixing ratio, relative humidity

accessory bud

A lateral bud occurring at the base of a terminal bud or in an axil, at the right or left of the axillary bud.

accumulated temperature

See cumulative temperature

accuracy

How near the 'true' value the estimate is. Accuracy involves both discrimination and precision.

achene

Dry, indehiscent fruit containing only one seed.

acidity exchange

Exchangeable hydrogen, aluminium and other cations that, when removed from the exchange complex, are sources of hydrogen ions in the soil solution.

acid soil

Soil with a pH of <  7.0.

active acidity

The activity of hydrogen ions in the aqueous phase of a soil. It is measured and expressed as a pH value.

active ingredient

That part of a herbicide or pesticide formulation which gives the substance its efficacy.

adaptation

1. A characteristic of survival value for plants or animals; survival in a specific environment.

2. The process by which individuals (or parts of individuals), populations or species change in form or function in such a way as to survive better under given environmental conditions (also the results of this process).

additivity

The response to treatments (and blocks, if relevant) being of the same kind and magnitude in the presence of other treatments (or blocks); that is, no interactions occur.

adjuvent

A herbicidally inactive material that when added to a herbicide formulation enhances the efficacy of that formulation.

adventitious structure

Structures arising from places other than the usual, for example, roots growing from leaves or buds developing at locations other than in leaf axils or shoot apices.

aeolian soil

Soil accumulated by wind; usually loose silt or sand deposits.

afforestation

1. Conversion of bare land into forest land by planting of forest trees.

2. The planting of a forest crop on land that has not previously, or not recently, carried a forest crop. See also reforestation

after-ripening

The processes whereby some seeds, once fallen or when collected, undergo natural biochemical or physical changes while in storage; often necessary for subsquent germination.

agglomerative classification

See clustering

aggregate

In soil. Many soil particles held in a single mass or cluster such as a clod, crumb, block or prism.

aggregate demand analysis

This type of economic analysis takes place at the level of a region or a country. It gives useful information and data of total demand for that area and of the important components that create that demand. It can be extremely useful for studying government policies. However, it does not consider differences among different groups within a society and generally presents an incomplete picture of the welfare of the population.

aggregation

The cementing or binding together of several soil particles into a secondary unit, aggregate or granule. Water-stable aggregates are particularly important to soil structure.

agrarian policy

A policy concerned with the land or landed properties.

agricultural system

A system with agricultural outputs and containing all the major components.

agroclimatic classification

The grouping of different physical areas within a country, a region or the world into broadly homogeneous zones based on climatic and edaphic factors.

agroecological zone

1. A major area of land that is broadly homogeneous in climatic and edaphic factors, but not necessarily contiguous, where a specific crop exhibits roughly the same biological expression.

2. Zones of similar agricultural performance as defined by soil and climate.

agroecosystem

The collection of physical, environmental, economic and social factors that affect a cropping enterprise.

agroforestry spatial units

See management boundary, primary land unit, total area

agroforestry system

A land-use system in which woody perennials (trees, shrubs, palms, bamboos) are deliberately used on the same land management unit as agricultural crops (woody or not), animals or both, either in some form of spatial arrangement ortemperal sequence. In agroforestry systems there are both ecological and economic interactions between the different components. 'Agroforestry' is a generic term for different types of systems, for example, agrosylvicultural system, sylvopastoral system

agronomic variety

A distinctive seedling population or clone with enough favourable characteristics to warrant cultivation. Agronomic varieties are given non-Latin names according to priority rules which vary among different crops.See also variety, cultivar

agronomy

That part of agriculture devoted to the production of crops and the management of the soil on which they are grown. The scientific utilization of agricultural land.

agropastoral system

A land-use system in which crops and livestock (but not trees) are the only components.

agrosilvicultural system

An agroforestry system for the concurrent production of agricultural crops (including woody perennial crops) and forest crops. The forest crops serve in either a productive or a service role. Woody perennial and agricultural crops are chosen first for their productive capacity.

agrosilvipastoral system

Any agroforestry system that includes trees or shrubs and herbaceous food crops and pastures and animals.

agrostology

The study of grasses.

A horizon

The surface soil horizon of a mineral soil having maximum organic matter accumulation, maximum biological activity or eluviation of materials such as iron, aluminium oxides and silicate clays. See also B horizon, C horizon

air-dry soil

Soil that has been spread out to dry, usually in thin layers in the shade, until it reaches a constant weight. Final water content may vary somewhat with environmental conditions. Applies also to plant materials that often can be sun dried. See also oven-dry soil

air layering

A technique of propagating using an undetached stem to which the rooting medium is applied by securing it in an appropriate container, for example, a polythene bag (syn: marcotting).

albedo

The ratio of reflected to incoming radiation, usually given in percentage (of vegetation or bare soil).

algorithm

A series of steps or rules to be followed to calculate some quantity or reach a decision. See also heuristic

alkali soil

1. A soil having a high degree of alkalinity (pH of 8.5 or higher) or having a high exchangeable sodium content (15% or more of the exchange capacity) or both. When saline soils are leached, and if calcium levels are low, exchangeable calcium is replaced by sodium and the soils become highly alkaline and deflocculate.

2. A soil that has such a high a degree of alkalinity or percentage of exchangeable sodium, or both, that the growth of most crop plants is reduced. This is true if the pH is 8.5 or higher, or if the percentage of exchangeable sodium is 15% or more. Such soils are highly dispersed so that air and water movements are very slow. In popular usage, saline soils have been called 'white alkali' soils. True alkali soils, because of dispersion of the organic matter, have been called 'black alkali' soils.

alkaline soil

Specifically a soil with a pH value > 7.0, caused by the presence of carbonates of calcium, magnesium, potassium and, more specifically, sodium. Usually refers to soils with pH values > 8.5.

alkalinity

Amount of cations balanced by weak acids expressed as milliequivalents of neutralized hydrogen ions in one litre of water. See also salinity

all-aged

Applied to a stand in which, theoretically, trees of all ages are found, including those of felling age. See even-aged, uneven-aged

allele

One of a pair (in a diploid individual) or series (in a population or a polyploid individual) of genes located at the same locus on homozygous chromosomes and controlling the same character.

allelopathy

1. An interaction between different plants or between plants and microorganisms in which substances (allelochemicals) produced by one organism affect the growth of another (usually adversely).

2. The suppression of germination or growth or the limiting of the occurrence of plants, as a result of the release of chemical inhibitors by some plants.

3. The influence of plants (other than micro organisms) upon each other arising from the products of their metabolism.

alley cropping

An agroforestry intercropping system in which species of shrubs or trees are planted at spacings relatively close within row and wide between row, to leave room for herbaceous cropping between, that is, in the 'alleys' (syn: hedgerow intercropping).

allometric relationships

The changes in the ratio between two dimensions of an organism, such as root weight : shoot weight or total dry weight : stem diameter. Can be expressed over time or, better, with reference to changes in a particular growth factor (for example, specific root or shoot activity). Important in defining partitioning of dry matter in plants.

allopolyploid

A polyploid containing genetically different sets of chromosomes. For example, sets from two or more species.

alluvial soil

Soil developed from transported and relatively recently deposited material (alluvium) characterized by little or no modification of the orginal material by soil-forming processes.

alluvium

1. Clay, silt, sand, gravel, pebble or other detrital materials deposited by water.

2. A sediment deposited by streams and varying widely in particle size. The stones and boulders, when present, are usually rounded or subrounded. Some of the most fertile soils are derived from alluvium of medium or fine texture.

alpha design

One of a class of incomplete block designs that cater for a wider range of numbers of entries than 'square' or 'rectangular' lattices. Both design and data analysis may require the help of a statistician.

alternative farming

Farming not in the current, conventional manner; for example, not using fertilizers and pesticides, or by using intermediate technology and renewable energy sources. See also organic farming

amenity horticulture

The application of horticultural practices for leisure-oriented or aesthetic purposes.

ammonification

The biochemical process in which ammonical nitrogen is released from organic compounds containing nitrogen.

amphidiploid

A polyploid whose chromosome complement is made up of the entire somatic complements of two species.

anaerobic

The absence of molecular oxygen.

analytical model

A model in which all functional relationships can be expressed in closed form and the parameters fixed, so that the equations can be solved by classical methods of analytical mathematics.

anemophilous

Wind pollinated.

aneuploid

An organism whose somatic chromosome number is not an even multiple of the haploid number. See also polyploid

angle of repose

Angle between the horizontal and the maximum slope that a soil may assume. Also applicable to rock fragments and depends on size, shape and cohesiveness of particles.

anion

Negatively charged ion. See also cation

anisotropic

Describing a process or quantity that is different in different directions; for example, in wood, strength and shrinkage properties vary in the radial, tangential and transverse directions.

annual plant

A plant that completes its life cycle within one year. Syn: annual. See also seasonal plant

anthesis

The opening of a flower bud; the exposure of stamens and stigmas to pollinating agents; the span of life of a flower.

apical control

The control of tree crown development in which interactions between shoots determine branch elongation.

apical dominance

The control over lateral bud or shoot development exerted by plant growth regulators from a shoot apex in the current year of growth (syn: correlative inhibition).

apical meristem

The growing point of the plant. The tissue at the tip of the stem or root in which cells undergo division.

apiculture

Beekeeping.

apomixis

Reproduction in which sexual organs or related structures develop as seeds but fertilization does not occur, so that the resulting seed is vegetatively produced.

aquaculture

Fish farming. In a broad sense, producing any product under water, for example, algae (seaweed), Crustaceae (shrimp).

aquasilvicultural system

An agroforestry system that combines trees with the raising of aquatic animals. See also aquaculture

arable farming

See arable land

arable land

Refers to land under crops, land under temporary meadows for mowing or pasture, land under market and kitchen gardens (including cultivation under glass) and land temporarily fallow or lying idle. Hence 'arable farming'. See also ley farming

arboretum

A collection of specimen trees, preferably growing close to a nursery, from which seeds and cuttings can easily be gathered.

arboriculture

A general term for the cultivation of trees.

architectural model

Of trees, one of 24 different branching patterns describing the way tree form comes about. See also reiteration

aridity index

According to Thornthwaite, the degree of water deficiency below water need at any given station. The aridity index = 1000 d/n, where d = water deficit, the sum of the monthly differences of precipitation (P) and evapotranspiration (Eo) when P < Eo, and where n is the sum of the monthly values of Eo for deficient months.

articulated growth

Rhythmic growth that results in shoot units separated by morphological discontinuities, for example, bud-scale scars. Hence articulated shoots can be contrasted with those undergoing continuous growth.

asexual reproduction

Propagation of plants from vegetative parts, such as stems, leaves or roots; or from modified stems such as bulbs, tubers, rhizomes and stolons. This is accomplished without union of gametes (syn: asexual regeneration).

aspect

Direction towards which land slope faces for example, east, west, and so on.

attenuate

In plant morphology: growing narrower toward the base, or sometimes toward the tip.

attribute

A quality possessed, or not possessed, by an individual. In pattern analysis, it is used to cover 'variables', 'attributes' (sensu stricto) and any other forms of information. See also variable, variate

auger

An instrument for drilling holes, used for taking soil samples.

autecology

The study of the individual organism, or an individual species, with emphasis on life histories and behaviour. See also genecology, synecology

autogamy

Self-fertilization.

autopolyploid

1. A polyploid arising through multiplication of the complete haploid set of a species.

2. An organism having more than two homologous (matched) sets of chromosomes derived from a single species.

autotroph

An organism capable of utilizing carbon dioxide or carbonates as the sole source of carbon and obtaining energy for its life processes from the oxidation of inorganic elements or compounds such as iron, sulphur, hydrogen, ammonium and nitrites, or from radiant energy.

auxin

A phytohormone involved in many physiological processes including root and stem elongation, fruit set, cambium activity and sex determination. Indoleacetic acid (IAA) is the major naturally occurring auxin.

available nutrient

That portion of the total of any element or compound in soil that can be readily absorbed and assimilated by growing plants. Not to be confused with 'exchangeable'.

available water

The water in soil that can be absorbed by plant roots. Usually considered to be that water held in soil against a tension of up to 15 bars.

available water-holding capacity

1. A measure of the ability of the soil to supply water to plants; the difference between field capacity and wilting point.

2. Of a soil, the capacity to store water for plant use. Usually expressed in linear depths of water per unit depth of soil and commonly defined as the difference between the percentage soil water at field capacity and at wilting point.

aviculture

A general term for the production of birds.

axillary

Growing in the axil, which is the angle between the upper side of the leaf and the stem.

axillary bud

A bud borne laterally on the stem in the axil of a leaf.