Nutrients for energy is very important in the world. Elements and dissolved salts essential to life may be conveniently termed biogenic salts or nutrients energy and divided into two groups, the macro nutrients and the micro nutrients. The former include energy elements and their compounds that have key roles in protoplasm and that are needed in relatively large quantities, as for example, carbon, hydrogen, oxygen, nitrogen, potassium, calcium, magnesium, sulfur, and phosphorus. The micronutrients include those elements and their compounds also necessary for the operation of living systems but are required only in very minute quantities; for example, iron, manganese, copper, zinc, boron, sodium, molybdenum, chlorine, vanadium, and cobalt. It should be emphasized at this point that elements that have no known biological function also circulate between organisms and environment. These may enter biogeochemical cycles linked with essential elements by reason of chemical affinity, or they may be simply carried along in the general energy – driven stream. Likewise, poisons produced by man, such as insecticides and radioactive strontium, all too often enter vital cycles and become lodged in the tissues of animals and man (more about this later). Although organisms do develop adaptive mechanisms to exclude harmful substances, there is no way that living membranes can function efficiently in the exchange of vital materials, and, at the same time be completely selective as to what is ‘’good’’ and what is ‘’bad’’ even if harmful substances are not lethal, an energy stress is placed on the organism since it must expend extra energy to sequester or ‘’pump out’’ the poison.
Nonessential and energy elements

        Nonessential and energy elements are, therefore, of great ecological importance if they occur in quantities or forms that are toxic, if they react to bind or make unavailable essential energy elements, or if they are radioactive. Thus, the ecologist is concerned with nearly all of the natural energy elements of the periodic table as well as with the newer man – made ones, such as plutonium.  

       air pollution on the environment is a danger problem in the world. Bothe the sulfur and the nitrogen cycles are involved in urban and industrial air pollution that increasingly threatens the health of man and plants. The oxides of nitrogen (NO and NO₂) and sulfur (S₂) are rather toxic gases which are but transitory steps leading to the formation of nitrate (NO₃) and sulfate (SO₄) in their respective cycles. They are normally present in most environment in very low concentrations. The burning of fossil fuels however, has greatly increased the concentration of these volatile. oxides in the air, especially in environment urban regions, to the extent that they constitute about a third of the some 150 million tons of industrial air pollutants estimated to be released annually over the united states. Coal – burning electrical generating plants constitute a major source of SO₂, and the automobile is a major source of NO₂. Sulfur dioxide is very damaging to the photosynthetic process; the destruction of vegetation and crops around copper smelters and in the los Angeles basin is caused by this pollutant. Also, SO₂ combines with water vapor to produce airborne sulfuric acid (H₂ SO₄ ). The resulting ‘’acid rain’’ causes millions of dollars damage to metal, limestone, and other construction material, not to mention possible damage to respiratory tissues. Likensand Bormann (1974) have documented how the PH of rainwater falling over the industrialized area has decreased (that is rain has become more acid) during the past two decades.
 The oxides of nitrogen dangers for environment

        The oxides of nitrogen is very harmful problem for our environment and The oxides of nitrogen are particularly harmful to lungs and are thought to contribute to the increase in respiratory diseases  and cancer in urban populations. Furthermore, these oxides combine with hydrocarbons and other pollutants under the driving force of environment sunlight to produce a synergism (=total effect of the interaction exceeds the sum of the effects of each substance) called ‘’photochemical smog’’. Technology is available to reduce these air and environment pollutants at their sources but so far it has proved to be expensive. Air pollution may well limit the size of fuel – powered cities environment, at least for the next couple of decades and this could work out as a net benefit for man.

  When a farmer a sends a sample of soil energy to the soils laboratory of his state university for routine testing, the sample is often treated with 0.1 normal acid or alkali solution. The quantity of minerals, such as phosphorus, calcium, or potassium, removed by such gentle treatments is considered a crude measure of quantities available to plants (that is, the size of the available pools). A simple soil energy test such as this may provide a useful basis for fertilizer recommendations, but as often as not leaves much to be desired. As with energy, it is evident that the rates of movement or cycling may be more important in determining biological energy productivity than the amount present in any one place at any one time. Turnover time and turnover rate, as convenient measures of flux. It is the flux (= rate of transfer), rather than the concentration, that is of prime importance. Tracers have been a great help in determining rates of movements since tagged atoms can actually be followed as they exchange with organism and environment.

       During the past ten years what has come to be known as mineral cycling has received increasing attention in ecological research. One – at – a – time study of single elements has been superseded by studies of the behavior of groups of linked elements and compounds as related to energy flow and stability. These newer approaches have been made possible by improved techniques of systems modeling. Major breakthroughs have been made in our understanding of the role of energy as the driving force for cycling, and the role played by microorganisms in releases of releases of essential elements from other wise unavailable pools.

      The world distribution of primary production is shown schematically in figure 3 -7. Values represent the average gross production rate per square meter of area to be expected in an annual cycle. As previously indicated, as much as 90 percent of gross production may be available to heterotrophy, but usually only about 50 percent is actually is actually utilized. It should be remembered that man or any other single species cannot assimilate all of the net production. For example, cornstalks and wheat stubble and roots would be unclouded in the total production of these crops, but only the grain is currently consumed by man.

potential biological fertility

      As may be seen from figure 3 -7, there are about three orders of magnitude in potential biological fertility of the world: (1) large parts of the open oceans and land deserts ranging around 1000 kcal/m²/ year or less; these are the solar – powered ecosystems that are nutrient or water limited. (2) potential biological fertility many grasslands, coastal seas, shallow lakes, and ordinary agriculture range between 1000 and 10,000; these are the energy subsidized solar – powered system. (3) potential biological fertility certain shallow water system such as estuaries, coral reefs, and mineral springs together with moist forests, intensive agriculture (such as year – round culture of sugar cane or cropping on irrigated deserts), and natural communities on alluvial plains may range from10,000 to 20,000. Production rates higher than 20,000 have been reported for experimental crops, polluted waters, and limited natural communities. A probable upper limit of 40,000 – 50,000 has already been noted.

tentative

       Two tentative generalizations may be made from the data at hand. First, basic primary productivity is not necessarily a function of the kind of producer organism or the kind of medium (whether air, fresh water, or salt water), but is controlled by local supply of raw material, sun energy, supplemental energy, and the ability of local communities as a whole (and including man) to utilize and regenerate materials for continuous reuse. Terrestrial systems are not inherently different from aquatic situations if light, water, and nutrient conditions are similar. However, large bodies of water are at a disadvantage because a large portion of light energy may be absorbed by the water before it reaches the site of maximum mineral supply in the deep water. Secondly, a very large portion of the earth’s surface is open ocean or arid and semiarid land and thus in the low production category, because of lack nutrients in the former and lacky of water in the latter. Many deserts can be irrigated successfully, and it is theoretically possible and perhaps feasible in the future to bring up ‘’lost’’ nutrients from the bottom of the sea and thus greatly increase production at, of course, the expenditure of some form of energy. Such an ‘’upwelling’’ occurs naturally in some coastal areas, and these have a productivity many times that of the average ocean. A famous example of the effect of upwelling on productivity is found along the coast of peru. Currents are such that nutrient – rich bottom waters are constantly being brought to the surface so that phytoplankton does not suffer the usual nutrient limitations of the sea. The area supports very large populations of fish and fish – eating birds; so much guano is produced by the birds as they nest along shore man is able to harvest it for fertilizer on a continuous – yied basis. Ryther (1969) has called the Peruvian upwelling area the world’s most productive natural fishery. Some 10⁷ metric tons of anchovies are harvested annually from 60 . 10³ km² which comes to about 300 kcal/ m^2, a very secondary production. Because the fleets of all fishing nations fish this area, even this bonanza is now in danger of being overfished.

distribution of primary production

The world distribution of primary production is displayed in more detail in table 3 – 1, which also includes an estimate of the global area occupied by major ecosystems, and also an estimate of total gross production of the biosphere. The word ‘’estimate’’ should be emphasized since there is yet no accurate inventory of productivity on a global basis, although the beginning of such an inventory is underway as part of an ‘’international biological program’’ which is being funded by governmental agencies of many of the nations of the world. For the most recent survey see the symposium entitled ‘’ the primary production of the biosphere,’’ edited by whittaker and likens (1973).

When the first estimates of global productivity were made in the 1940s it was assumed that the productivity of the ocean was greater than that of the land because it was larger. Then it was discovered that much of the ocean was ‘’desert,’’ so the consen us now is that the land areas contribute more than half of the total. The estimate of 10¹⁸ kcal/ year for global productivity is less than 1 percent of the solar energy entering the biosphere, as we have already noted. But this does not mean that it will be easy to increase world productivity or divert a larger share to food for man.