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  • Glossary
| Last Updated:27/12/2023



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Antagonistic effect

A biologic response to exposure to multiple substances that is less than would be expected if the known effects of the individual substances were added together [compare with additive effect and synergistic effect].


A substance measured in the laboratory. A chemical for which a sample (such as water, air, or blood) is tested in a laboratory. For example, if the analyte is mercury, the laboratory test will determine the amount of mercury in the sample.

Acid Rain

The precipitation of dilute solutions of strong mineral acids, formed by the mixing in the atmosphere of various industrial pollutants - primarily sulfur dioxide and nitrogen oxides with naturally occurring oxygen and water vapor.


Grouping, following establishment of scattered colonizing invaders as a result of propagation.

Advance Growth

Seedlings, saplings and poles of species of the overwood that have become established naturally in a forest before regeneration fellings are started.

Autotrophic Plants

Plants which obtain their food exclusively from the inorganic materials of soil, air and water.

Autogenic Factors

Dominating factors of change which are due only to the individuals in a plant community, e.g., shade, root competition, etc.


The ecology of an individual organism or taxonomic group as opposed to syn-ecology which is the ecology of a community.

Assortment Table

A volume table giving the volumes in the round down to various thin-end diameters.


The art of cultivating trees primarily for shade or landscape effects.


A place for cultivating and displaying trees.

Annual Ring

A layer of wood produced by the growth of one year

Anemophilous Plants

Plants pollinated by wind.


A term applied to the zone of vegetation where winter is severe, snowfall heavy, the mean annual temperature is under 450 F. and the mean January temperature below 300 F. In India, alpine zone occurs in the Himalayas at altitudes above 3,030.3 m.

Allogenic Factors

Factors which operate, independently of the plants themselves, to alter the habitat gradually and thus cause changes in the vegetation.


Grouping, following establishment of scattered colonizing invaders as a result of propagation

Age Gradation

An age class with one year as the interval. Loosely used sometimes as synonymous with age class.

Age Classification

The division of a crop according to differences in age or the allotment of woods to age classes.

Age Class

One of the intervals into which the range of age of trees growing in a forest is divided for classification or use also the trees falling into such an interval.


Biochemical or physical changes occurring in seeds, bulbs, tubers and fruits after harvesting when ripe in the ordinary way often necessary for subsequent germination or growth.


To establish a forest by artificial means on an area from which forest vegetation has always or long been absent.

Aesthetic Forestry

The practice of forestry with the object of developing or maintaining a forest of high scenic value.

Adventitious Bud

A bud from any part of the stem, leaves or roots that is not connected with the strands of bud-bearing tissue arising from the axils of the leaves.

Advance Thinning

Thinning done in a regular crop in anticipation of suppression a method developed by Craib and O’Connor for wattle and pine plantations in S. Africa.


Regions where precipitation is insufficient in quantity for most crops and where agriculture is impractical without irrigation.


A porous, water-saturated layer of sediment and bedrock under the Earth's surface; also described as artesian (confined) or water table (unconfined).


Pesticides and fertilizers developed artificially for agricultural use.

Aquatic environment

The combination of physical, chemical, and biological conditions present in lakes, reservoirs, wetlands, rivers and oceans.


Artificial cultivation or growth of fish, crayfish and other organisms for use as food, particularly in fishpondsand similar structures .


Small, often microscopic, aquatic plants in a water body .


Anion-cation interaction (anion-cation attraction; cation-anion interaction; ionic bond): A noncovalent (van der Waals) attractive force caused by electrostatic .


Anaerobic organisms use substances other than oxygen as electron acceptors when degradating organic compounds.


Amictic lakes are "perennially sealed off by ice from most of the annual seasonal variations in temperature.


Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms


Acidity is such a common problem that occurs due to consumption of spicy and fried foods. It also occurs because of less intake of water, not taking meals on time or due to overeating.


Abiotic  or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems.


Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid. It can exist in various allotropes, although only the gray form has important use in industry.


An enzyme that cleaves acetylcholine.


Giving atropine until it reaches a sufficiently high blood concentration to suppress cholinergic signs clinically.


Esterases   (such   as   acetylcholinesterase   and  neuropathy  target  esterase)   are  inhibited   by  organophosphorus compounds  through  phosphorylation.  Inhibited  acetylcholinesterase  reactivates  spontaneously  at  very  slow  rates; oximes   speed   up   this  reaction.  However,   phosphorylated   acetylcholinesterase   may   lose   an  alkyl  side  chain non-enzymatically, leaving a hydroxyl group in its place ("ageing"). Regeneration is then no longer possible. The half-life of ageing  is  as  fast  as  8  minutes  with  the  nerve  gas  soman but as slow as 33 hours for diethyl pesticides such as chlorpyrifos.


The capacity of water for neutralizing an acid solution.

Algal blooms

Sudden spurts of algal growth that can affect water quality adversely and that indicate potentially hazardous changes in local water chemistry.


A community of microorganisms, plants and animals, together with their abiotic environment, that occurs on farmed land, and including the crop species.


The mass of air surrounding the Earth.

Air pollution

Air is made up of a number of gases, mostly nitrogen and oxygen and, in smaller amounts, water vapour, carbon dioxide and argon and other trace gases. Air pollution occurs when harmful chemicals and particles are emitted to the air – due to human activity or natural forces – at a concentration that interferes with human health or welfare or that harms the environment in other ways.


The ability of a body of water to purify itself of pollutants.

Activated sludge

Residue that results when primary effluent is mixed with bacteria-laden sludge and then agitated and aerated to promote biological treatment. This speeds breakdown of organic matter in raw sewage undergoing secondary wastewater treatment.

Air quality

A measure of the level of pollution in the air.

Alternative energy sources

Energy that does not come from fossil fuels (such as coal, oil, gas), for example wind, flowing water, solar energy and biomass.

Ambient Air

Outside air in the environment.

Absorption of radiation

The uptake of radiation by a solid body, liquid or gas.  The absorbed energy may be transferred or re-emitted.

Acid deposition

A complex chemical and atmospheric process whereby recombined emissions of sulfur and nitrogen compounds are redeposited on earth in wet or dry form.  

Acid solution

Any water solution that has more hydrogen ions (H+) than hydroxide ions (OH-); any water solution with a pH less than 7.

Adiabatic process

 A thermodynamic change of state of a system such that no heat or mass is transferred across the boundaries of the system. In an adiabatic process, expansion always results in cooling, and compression in warming.



Particulate matter, solid or liquid, larger than a molecule but small enough to remain suspended in the atmosphere. Natural sources include salt particles from sea spray, dust and clay particles as a result of weathering of rocks, both of which are carried upward by the wind. Aerosols can also originate as a result of human activities and are often considered pollutants. Aerosols are important in the atmosphere as nuclei for the condensation of water droplets and ice crystals, as participants in various chemical cycles, and as absorbers and scatters of solar radiation, thereby influencing the radiation budget of the Earth’s climate system

Air carrier

An operator (e.g., airline) in the commercial system of air transportation consisting of aircraft that hold certificates of, Public Convenience and Necessity, issued by the Department of Transportation, to conduct scheduled or non-scheduled flights within the country or abroad.


 The fraction of the total solar radiation incident on a body that is reflected by it.