Glossary for agroforestry

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

ecofarming

Farming land by using practices that maintain biological diversity and conserve the resource base. See also organic farming, sustainable development, sustainable land use

ecological niche

See niche

ecology

1. The study of the totality or patterns of relations between organisms and their environment.

2. The study of the interactions of living things, from ecos, the Greek word for 'living earth'. Certain plants and animals require specific conditions to live well and this is often termed the ecology of that plant or animal.

economic analysis

An analysis done using economic values. In general, economic analysis omits transfer payments (credit transfers, and so on) and values all items at their value in use or their opportunity cost to the society.

ecospecies

A sexually reproducing population, the constituents of which produce vital and fertile descendants with each other but give rise to less vital or more or less sterile descendants when crossed with individuals of any other population.

ecosystem

1. The entire system of life and its environmental and geographical factors that influence all life, including the plants, the animals and the environmental factors.

2. System that includes both living (biotic) and non-living (abiotic) units to produce an exchange between them.

3. A group of organisms interacting among themselves and with their environment. See also biocoenosis, biotope

4. Any unit that includes all the organisms (the community) in a given area interacting with the physical environment, so that a flow of energy leads to a clearly defined trophic structure, biotic diversity and cycling of materials within the system.

ecotone

1. A transition between two or more diverse communities, such as that between the grassland and the forest biomass. It is a tension zone containing overlapping communities of each community. There may be species present in the ecotone not found in either of the bordering communities.

2. A zone of transition from one major plant community to another.

ecotype

1. Products of the reaction between the genotype and the environment that are found as a result of the selective action of the predominant factors of the environment. A partial range of an ecocline. (See cline).

2. A genetic subdivision of a species resulting from the selective action of a particular environment and showing adaptation to that environment. Carries connotation of difference but not necessarily of adaptation. Ecotypes may be geographic, climatic, elevational or edaphic. See also race

ecozone

An area within which the climate conforms to a particular pattern, and hence, vegetation is generally of a particular kind, for example, rainforest, savanna (syn: ecological zone).

ectotrophic mycorrhiza

A mycorrhizal association in which the fungal hyphae form a compact mantle on the surface of the roots. Mycelial strands extend inward between cortical cells and outward from the mantle to the surrounding soil. See also endotrophic mycorrhiza

edaphic

Of or pertaining to the soil in its ecological relationships. Resulting from, or influenced by, factors inherent in the soil or other substrate rather than by climatic factors.

edge effect

The effect at the edge of a plot resulting from its proximity to a neighbouring plot with a different treatment or to a vacant area.

effect

The extent to which a measured response (such as an increase in stem diameter) is changed by an experimental treatment relative to some other treatment. See also interaction, main effect

efficiency

A ratio of output (or performance, or success) to the input(s) (or costs) involved, over a specified time and in a specified context.

electrophoresis

Separation of charged molecules in a fluid or gel by creating an electrical field that draws groups with positive charges to the cathode and those with negative charges to the anode. Molecular size and shape affect rate of migration.

elite seed

See certified seed

elite tree

A tree of proven good combining ability (genetic breeding value), proven by progeny testing. See also plus tree

eluviation

The transportation of soil material in suspension, or in solution within the soil, by the downward or lateral movement of water.

empirical model

A model based on observed quantitative relationships among variables, without any insight into the functional or causal operation of the system.

emulsifiable concentrate

A concentrated solution of a spray material (insecticide, fungicide, herbicide) and an emulsifier in an organic solvent, which will form an emulsion spontaneously when added to water and agitated.

emulsifier

A surface-acting agent, which reduces interfacial tension and which can be used to facilitate formation of an emulsion of one liquid with another. See also wettable powder

emulsion

A mixture in which very small droplets of one liquid are suspended in another liquid, for example, oil in water.

endemic

Native or confined naturally to a particular, usually restricted, area or region; biologically a relic of once-wide distribution.

endodermis

Single layer of cells between the cortex and pericycle in the root.

endogenous

Development within (endogenesis), that is, forming new tissue within the plant. Originating from internal tissues; forming inside another organ of a plant.

endogenous mechanism

A mechanism arising from within. In phenology, refers to control of plant development through internal factors.

endogenous substance

A naturally produced substance; one produced within the organism on which it is acting. Arising from within. See also exogenous

endogenous variable

Dependent, output variable in simulation modelling. Generated by the effect of the exogenous variables on the system's state variables. See also variable

endotrophic mycorrhiza

A mycorrhizal association in which the fungal hyphae are present on root surfaces as individual threads that may penetrate directly into root hairs, other epidermal cells and occasionally into cortical cells. Threads extend into the surrounding soil. See also ectotrophic mycorrhiza

energy balance

Accounts for the disposition of radiation at the earth's surface. Vertical energy balance can be expressed as net radiation = evaporation + heat flux density into the air + heat flux density into the ground (+ other minor heat flux densities). Net radiation and heat flux densities can be directly measured and evaporation then determined by the difference; evapotranspiration can be measured directly with a lysimeter.

energy farming

The process of using land to grow crops, woody or otherwise, that provide fuel, for example, close-planted, fast-growing tree species such as poplar (temperate) or leucaena (tropical). These may be harvested by hand or mechanically. Hydrocarbon fuels can be extracted from other kinds of plants, for example, from some Euphorbia species.

energy plantation

See energy farming

enriched fallow

A form of agroforestry in which useful, mainly woody species are sown or planted before cultivation ceases, or at the time it does, so that during the fallow period, or when the land is next cleared for cultivation, products are available for household use or market that would not otherwise have been there (for example, fruits, bamboos, rattans, medicinals). See also fallow

ensilage

See silage

entomophilous

Insect pollinated.

enumerator

Participatory researcher in field studies.

environment

The totality of external conditions affecting a living organism or a community (biocoenosis) of organisms in their habitat (biotope).

environmental factor

Factors over which farmers often have little direct control, including the physical, biological and socioeconomic aspects of their setting. See also exogenous variable

environmental resource capture

See resource capture

epicormic

Originating from the trunk, such as an epicormic shoot developing from a latent meristem.

epicormic shoot

1. A shoot arising spontaneously from an adventitious or dormant bud on the stem or branch of a woody plant. Also called coppice shoot, 'water shoot', 'water sprout'.

2. A fast-growing shoot arising from a dormant bud on an old stem or branch, often in response to stimulus such as removal of part of the canopy or tree thinning.

epidemic

A widespread and severe outbreak of a disease. A disease increase in a population.

epidemiology

Of pests, the study of the conditions that favour or hinder their prevalence.

epinasty

The more rapid growth or elongation of the upper side of a plant organ, for example, a leaf, which then results in downward curling.

epiphyte

1. A plant growing on but not nourished by another plant.

2. Plants that grow by supporting themselves on others, germinating (and rooting, if higher plants) there.

episodic growth

See rhythmic growth

equilibrium

A state of natural balance. An ecosystem that is in equilibrium is self-perpetuating.

equitability

In agroecosystem analysis, a property of distribution within a system in which the results of productivity are shared among the human population.

eradication

Control of plant disease by eliminating the pathogen after it is established or by eliminating the plants that carry the pathogen. Applies to all pests.

erodibility

Strictly, the propensity of a soil to be eroded; that is, soils are more erodible or less erodible. See also erosivity

erosion

The detachment and movement of the solid material of the land surface by wind, moving water or ice, and by such processes as landslides and soil creep.

erosive

Tending to cause erosion. The term should apply to the eroding agents, such as wind or water, but it has also been used interchangeably with 'erodible', although the word 'erosive' is preferred when referring to the agent causing erosion and 'erodible' when referring to the material eroded.

erosivity

Power of water or wind to cause erosion. Not to be confused with erodibility.

error variance

A measure of the variation between experimental units arising from unrecognized or uncontrolled factors in an experiment. See also residual variation

establishment

The successful growth of young plants, brought about by providing them with the right site and favourable conditions.

ethnobotany

That branch of botany that seeks an understanding of what plants people use and how they use them. Hence an 'ethnobotanical survey'.

eugenic

Favourable to the genetic quality of a population. Practices that improve the hereditary qualities of future generations. See also dysgenic

eutrophication

Enrichment of water bodies with plant nutrients, resulting in growth of algae, other plants and (eventually) animals in the water.

evaporation pan

Evaporimeter composed of a fairly deep tank or pan with a rather large surface in which lowering of the water level caused by evaporation can be measured. See also pan coefficient

evapotranspiration

The loss of soil water to the atmosphere by plant transpiration and evaporation from the soil surface.

evapotranspirometer

An instrument used for measuring evapotranspiration, consisting of a soil tank in which vegetation (a crop) is planted; the tank is designed so that all the water added to it and all the water left after evapotranspiration can be measured. See also lysimeter

even-aged

1. A tree crop in which the trees are, or appear to be, all of the same age. It can result from plantings or from natural seedlings arising after felling or seeding.

2. Applied to a stand in which relatively small age differences exist between individual trees. The maximum difference in age permitted in an even-aged stand is usually 10–20 years, although where the stand will not be harvested until it is 100–200 years old, larger differences of up to 25% of the rotation age may be allowed. See also uneven-aged

even-aged forest

Forest composed of trees of the same age.

evergreen

A plant remaining green in its dormant season and so applied to plants that are green throughout the year. Properly applied to plants and not to leaves, as it is due to the persistence of leaves. A better term is leaf retaining. See also deciduous

evolution

Long-term changes in gene frequency and phenotypic characteristics of a population or group of populations.

ex ante

In economics, drawing conclusions about what will happen in the future by analysing what has gone before. See also ex post

exchange acidity

The titratable hydrogen and aluminium that can be replaced from the adsorbtion complex by a neutral salt solution.

exchange capacity

The total ionic charge of the adsorption complex active in the adsorption of ions. See also cation exchange capacity

exogenous

1. External. Descriptive of a substance applied to a plant to alter its growth or other processes or to climatic factors that can influence phenology. See also endogenous

2. Produced on the outside of another body. Produced externally, as spores on the tips of fungal hyphae. Growing by outer additions of annual layers, as the wood in dicotyledons.

exogenous mechanism

Arising from without. In plant phenology, the control of plant development by external factors, as distinct from an endogenous mechanism.

exogenous variable

Input variable in simulation modelling independent of the internal state of the system. These variables represent external factors imposed upon the system and acting on it to induce changes within it; that is, they are 'forcing' or 'driving' functions. See also variable

exotic

Commonly used to refer to a plant or other organism introduced from a foreign country. For example, Grevillea robusta, which comes from Australia, is an exotic tree species in Kenya. Strictly, however, the term refers to a plant grown anywhere outside its natural range (syn: non-native). See also indigenous

experiment

An action or operation undertaken to discover something unknown, to test a hypothesis or to establish or illustrate some known trends. May be part of a major investigation or study and is of more significance than a trial.

experimental design

A method of arranging sample or experimental units to minimize the effects of uncontrolled variation caused by natural factors, for example, soil fertility, and to make it possible to estimate the magnitude of such effects with reference to those caused by experimental treatments.

explant

The excised fragment of a plant tissue or organ used to start a tissue culture. See also micropropagation, meristem culture

ex post

Actually realized. See also ex ante

exposure

The degree to which a site is exposed to wind. It may be judged by the position of the site relative to the visible horizon. If the site is above the horizon it is exposed; if below, it is sheltered.

expressivity

The degree to which a gene expresses itself in the phenotype.

ex situ

From outside. When applied to tree plantations, refers to a planting site distant from the seed collection site. See also in situ

extraction

The operation of removing felled timber from a wood or forest to a road accessible by transport.