Glossary for agroforestry

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

macroclimate

The climate of a region. See also microclimate, topoclimate

macronutrient

A chemical element necessary in large amounts (usually > 50 ppm in the plant) for the growth of plants. Includes C, H, O, N, P, K, Ca, Mg, S. 'Macro' refers to quantity and not to essentiality of the element. See also micronutrient

main effect

The response to different levels of a treatment factor, measured independently of other factors. In a balanced design such as a randomized complete block, the main effects of levels of a treatment factor are estimated by averaging the corresponding responses over all levels of every other factor.

management boundary

A basic spatial unit suggested to embrace agriculture, horticulture, forestry and agroforestry; an ecologically homogeneous area set aside for a particular use. In agriculture, the 'field'. See also block, compartment

mangroves

1. Open or closed stands of trees and bushes occurring in the tropics in intertidal zones, usually around the mouths of rivers, creeks and lagoons where soils are heavy textured and have a fluctuating salt content and soil level.

2. A name used collectively for the assemblage of plants, as well as to refer to individual genera or species, for example, woody members of the Rhizophoraceae, Combretaceae and Verbenaceae. These have knee-like roots that are 'pneumatophores' (roots with air spaces). Grown for wood and tannins.

manure

Animal excreta with or without a mixture of bedding or litter. See also farmyard manure, green manure

marcotting

See air layering

marker gene

A gene, usually dominant, with a large effect and serving to identify one parent in offspring resulting from open pollination.

mass selection

1. Phenotypic selection. Choosing trees on the basis of their phenotypic performance.

2. A form of selection in which individual plants are chosen and the next generation propagated from the aggregate of their seeds (with self-pollinated plants).

mast fruiting

A period of massive fruit production.

matric potential

See leaf water potential

matrix

1. A two-dimensional array of numbers. The meaning of each number (or element) depends on its position in the matrix, that is, on the row and the column in which it occurs.

2. The generally rigid and connected material in which other matter is retained.

maturity

A phase in the development of a plant (usually irreversible) that marks the transition from juvenility, when the plant is unable to flower, to a full capacity to form flowers that are sexually reproductive (unless the plant shows apomixis).

maximum rainfall intensity

See rainfall intensity

mean

A measure of central tendency, for example, a 'sample mean'. The 'arithmetic mean' is obtained by dividing the sum of the observations by their number; the 'geometric mean' is the arithmetic mean of the logarithms. See also median, mode

mean annual increment

In forestry, for a particular stand, the total increment of wood up to a given stand age (in years) divided by that age. The mean annual increment for a whole rotation is termed the final mean annual increment. See also current annual increment, site class, yield class

mechanical thinning

Thinning in which a predetermined proportion of the trees is removed without regard to size or quality, such as, for example, every third tree. See also line thinning, selective thinning

mechanistic model

A model based on known mechanisms that operate within the model, such as the fundamental laws of physics and chemistry. It may be a subclass of a deterministic model.

median

A measure of central tendency. The middle value in a frequency distribution, that is, as many values lie above as below it. See also mean, mode

meristem

1. A plant tissue composed of dividing cells and giving rise to organs such as leaves, flowers, xylem, phloem, roots.

2. A region of a plant in which cells are not fully differentiated and are capable of repeated mitotic divisions. See also cambium

meristem culture

Apical meristem culture; a part taken (an explant) consisting only of the apical dome of tissue above the youngest leaf primordium.

mesophyte

A plant that requires a moderate amount of water for normal growth; includes most crop plants.

metabolism

1. The biochemical processes an organism must accomplish in order to live.

2. The process by which cells or organisms utilize nutritive material to build living matter and structural components, or to break down cellular material into simple substances to perform special functions.

metabolizable energy

The usable energy in animal feeds taking into account the amounts of different constituents (carbohydrates, proteins etc,) their digestibility and their calorific value.

microclimate

The climate as found in small areas, for example, around plants. See also macroclimate, topoclimate

microfauna

The small animals that can be seen only with a microscope, such as protozoa, nematodes.

microflora

The small plants that can be seen only with a microscope, such as algae, fungi.

micronutrient

A chemical element necessary in only extremely small amounts (< 50 ppm in the plant) for the growth of plants. Examples are B, Cl, Cu, Fe, N, Zn. 'Micro' refers to the amount used rather than to essentiality. Also called 'trace elements'.

microorganism

A member of the microflora or microfauna that can be seen only with a microscope.

micropropagation

Various procedures by which small pieces of plant tissue are taken, surface sterilized and then grown on, or in, an appropriate medium under carefully controlled environmental conditions and provided with appropriate nutrients, growth hormones, and supplementary components, to allow cells to differentiate into small plantlets (explants). These are then transplanted (perhaps several times) and eventually hardened off before being planted out. See also meristem culture

micro water catchment

A modification to the soil surface on a slope that traps and conveys runoff water to a small pit, adjacent to which a tree is planted. Part of water harvesting.

mimosine

An alkaloid toxic to animals, which is contained in some members of the legume family (Mimosaceae) including Leucaena leucocephala. Its toxicity minimizes the amounts of leafy material that can be fed, although ruminants can detoxify mimosine through bacterial action in the rumen provided they have the right microflora (either naturally or by inoculation).

mineralization

The conversion of an element from an organic form to an inorganic state as a result of microbial decomposition.

mineral soil

A soil containing lessthan 20% organic matter or having a surface organic layer less than 30 cm deep. See organic soil

minimum tillage

Crop production where soil cultivation is kept to the minimum necessary for crop establishment and growth. Weed control, where necessary, is by using herbicides, by pulling or scraping, or by mulching. See also no-tillage, zero tillage

miombo

A form of woodland found in southern Africa in hot, semi-arid regions with a monomodal rainfall (for example, in Tanzania, Zimbabwe, Malawi, Zambia). Rainfall is high (> 1000 mm) and soils are poor in nutrients and acid. The vegetation is dominated by slow-growing, mainly deciduous, caesalpiniaceous trees (for example, Brachystegia, Julbernardia).

mixed bud

See compound bud

mixed cropping

Growing more than one species on the same piece of land at the same time, or with only a short interval between. See also intercropping, multiple cropping, relay cropping

mixed farming

Farming involving crop and animal production.

mixed garden

A land-use form on private lands outside the village, dominated by planted perennial crops, mostly trees, under which annual (seasonal) crops are cultivated. When spices are grown they are called 'spice gardens'. See also homegarden

mixed stand

A stand in which less than 80% of the trees in the main canopy are of a single species.

mixing ratio

For moist air, the ratio of the mass of water vapour to the mass of dry air.

mode

1. A measure of central tendency, the value around which there is the greatest concentration in a frequency distribution. See also mean, median

2. The most common value (that is, the value with the highest frequency) in a frequency distribution.

model

1. A quantitative representation, which, if complex, may require algebraic and arithmetic manipulation. Such models are essential elements of systems analysis, statistical analysis and many forms of computer simulation.

2. A simplified representation of a system expressed in words, diagrammatically or by mathematical symbols.

3. A simplification of the real world that reveals the key processes necessary for prediction. Models may be verbal, graphic, mechanical or mathematical, depending on their purpose and the need for them; some can be used for quantification. See also analytical model, continuous model, deterministic model, dynamic model, empirical model, mechanistic model, numerical model, simulation model, stochastic model

monoculture

Growing a crop consisting of a single species (monocropping). See also sole cropping

monoecious

1. Bearing separate male and female flowers on the same plant. See also dioecious

2. Plants bearing unisexual flowers, both staminate and pistillate, on the same individual.

montmorillonite

A hydrous aluminosilicate clay with 2 : 1 expanding crystal lattice. Expansion on wetting is caused by water moving between silica layers of contiguous units.

mor

An accumulation of acid organic matter at the soil surface beneath a forest. See also mor humus

moraine

Any type of constructional topographic form consisting of till (stiff clay with boulders and sand, and the like) and resulting from glacial deposition.

mor humus

1. Leafy fibrous humus, often associated with heath and conifers. Mor humus is acid and forms a separate layer with slow mineralization. A slightly more modified state than peat.

2. A type of forest humus layer of unincorporated organic material, usually matted or compacted, or both. Distinctly delimited from the mineral soil, unless the latter has been blackened by washing in organic matter (syn: 'raw humus'). See also mull humus

morphology

Science of form and structural shape.

mulch

1. A natural or artificially applied layer of plant residues or other materials such as stones, sand, paper or brush on the surface of the soil.

2. A covering of plant material put on the soil to improve its fertility, moisture retention capacity and organic content.

3. A loose surface horizon that forms naturally or may be produced by cultivation and consists of either inorganic or organic materials.

mulch tillage

Tillage or preparation of soil in such a way that plant residues are left on the surface.

mull

A crumbly, intimate mixture of organic and mineral material formed mainly by worms, particularly earthworms.

mull humus

1. A type of forest humus layer consisting of organic and mineral matter so mixed that the transition to the underlying mineral layer is not sharp.

2. Associated with conditions of rapid mineralization and organo-mineral complexes of the clay fraction. Mixed microflora, bacteria and actinomycetes predominate. Dark in colour. See also mor humus

multilocational experiment

Experiment (or trial) conducted at more than one place with a view to including a larger range of edaphic (soil) and microclimatic conditions.

multiple cropping

Growing more than one crop on the same piece of land. See also intercropping, mixed cropping, simultaneous cropping and sequential cropping

multiple regression

The relationship between specified values of two or more variables (independent variables x1 and x2) and the expected value of a random variable (dependent variable b) of the form E(y) = b0 + b1x1 + b2x2.

multiple-use forestry

Any practice of forestry that fulfils two or more objectives of management, whether products, services or other benefits. Also called 'multipurpose forestry'.

multiple-use management

Of forests, where a forest is divided up and the various parts of it have different functions or provide different products. See also integrated resource management

multipurpose tree

1. A woody perennial that is purposefully grown to provide more than one significant contribution to the production or service functions (for example, shelter, shade, land sustainability) of the land-use system that it occupies. Also called 'agroforestry tree'.

multistage random sample

Sample selective scheme with more than one level of random selection; for example, the random selection of villages within a district, then of famers within each selected village. See also representative sample

multistorey cropping

Multispecies crop combinations involving both annuals and perennials with an existing stand of perennials. An association of tall perennials with shorter statured crop species.

multistorey system

An agroforestry system, such as a homegarden, that has a number of plant components of differing stature so that several layers of canopy are formed.

multivariate analysis

A loose term denoting the analysis of data that are multivariate in the sense that the value of each of k variables has been measured on each individual. Examples are canonical coordinate analysis and principal components analysis. See also pattern analysis

multivariate factor analysis

A mathematical method of analysing sets of data to discover which variables are statistically linked, by causative or other factors.

mutant

An individual possessing a new, heritable characteristic as a result of a mutation.

mutation

1. A sudden, heritable variation in a gene or in a chromosome structure.

2. A sudden change in genotype. Usually a gene mutation (change in a single gene) is meant, but the term is sometimes used in a broader sense to include changes from polyploidy, chromosome deletions, chromosome inversions, and so on.

mutualism

A relationship between two living beings A and B, where interaction is obligatory and favourable to both A and B, for example, as with mycorrhizae and Rhizobium bacteria.

mycorrhiza

An association that is probably symbiotic (or at least not parasitic) between the root or rhizome of a green plant and a fungus. See also ectotrophic mycorrhiza, endotrophic mycorrhiza