Nutrient+cycles

back to Ecosystems Soil Ecosystems Carbon Cycle Nitrogen Cycle Phosphorus Cycle Sulfur Cycle Unbalancing the Nitrogen Cycle Water Cycle

The Earth is essentially a closed system for matter. With the exception of a few meteorites, all the matter that exists on Earth was here when the planet formed billions of years ago. Matter continually cycles over short and long term time scales. The oxygen we breathe was once breathed by dinosaurs many eons ago. Natural processes continually cycle molecules from the atmosphere, biosphere, hydrosphere, and lithosphere. Human activities have an affect on the cycling of matter through Earth's systems. For example, the extraction and combustion of hydrocarbon fuels, such as coal, natural gas , and petroleum , release stores of carbon into the atmosphere over a much accelerated time scale than would have occurred through natural processes. Humans have also synthesized an enormous quantity of nitrogen, an element that is essential for plant growth, adding more of that nutrient to biogeochemical cycles than would have occurred naturally. Excess nitrogen has entered many fresh water and coastal ecosystems, resulting in eutrophication of these waters. The composition of the greenhouse gas layer in the atmosphere, which moderates global climate, has been altered by emissions of carbon, methane, and other substances from human activities, raising concerns of detrimental global climate changes .The long term effect of these changes to natural cycles is not fully understood. In discussions of environmental issues, a distinction is often made between natural and synthetic materials. However, all materials are ultimately made with the same fundamental building blocks - the elements - and made through the same reactions and processes that exist in nature. Even some of the most sophisticated new technologies attempt to mimic natural processes. Nanotechnology researchers, for example, study the self-assembly capacity of organic modules to find ways to replicate it. Many synthetic substances and materials have been found to have toxic or carcinogenic effects ; however, natural substances present the same dangers. Humans have made many dangerous materials and in many cases, the full degree of harm was unknown until later, sometimes many years after the materials were produced. Yet the environmental advantages and disadvantages of materials depend more upon the characteristics of the material, its byproducts, and its use, than how it was produced.  Homework Help for Students The Mineral Information Institute website includes examples of what products contain which minerals and a photo gallery. []

=Biogeochemical Cycles = The Earth is a closed system for matter, except for small amounts of cosmic debris that enter the Earth's atmosphere. This means that all the elements needed for the structure and chemical processes of life come from the elements that were present in the Earth's crust when it was formed billions of years ago. This matter, the building blocks of life, continually cycle through Earth's systems, the atmosphere, hydrosphere, biosphere, and lithosphere, on time scales that range from a few days to millions of years. These cycles are called biogeochemical cycles, because they include a variety of biological, geological, and chemical processes. Many elements cycle through ecosystems, organisms, air, water, and soil. Many of these are trace elements. Other elements, including carbon, nitrogen, oxygen, hydrogen, sulfur, and phosphorus are critical components of all biological life. Together, oxygen and carbon account for 80 percent of the weight of human beings. Because these elements are key components of life, they must be available for biological processes. Carbon, however, is relatively rare in the Earth's crust, and nitrogen, though abundant in the atmosphere, is in a form that is not useable by living organisms. The biogeochemical cycles transport and store these important elements so that they can be used by living organisms. Each cycle takes many different pathways and has various reservoirs, or storage places, where elements may reside for short or long periods of time. Each of the chemical, biological, and geological processes varies in their rates of cycling. Some molecules may cycle very quickly depending on the pathway. Carbon atoms in deep ocean sediments may take hundreds to millions of years to cycle completely through the system. An average water molecule resides in the atmosphere for about ten days, although it may be transported many miles before it falls back to the Earth as rain. How fast substances cycle depends on its chemical reactivity and whether or not it can be found in a gaseous state. A gaseous phase allows molecules to be transported quickly. Phosphorous has no gaseous phase and is relatively unreactive, so it moves very slowly through its cycle. Phosphorus is stored in large amounts in sediment in the oceans or in the Earth's crust and is recycled back to the surface only over very long periods of time through upwelling of ocean waters or weathering of rocks. Biogeochemical cycles are subject to disturbance by human activities. Humans accelerate natural biogeochemical cycles when elements are extracted from their reservoirs, or sources, and deposited back into the environment (sinks). For example, humans have significantly altered the carbon cycle by extracting and combusting billions of tons of hydrocarbons in fossil that were buried deep in the Earth's crust, in addition to clearing vegetation that stores carbon. Global release of carbon through human activities has increased from 1 billion tons per year in 1940 to 6.5 billion tons per year in 2000. About half of this extra carbon is taken up by plants and the oceans, while the other half remains in the atmosphere. In addition to carbon cycle, humans have altered the nitrogen and phosphorus cycles by adding these elements to croplands as fertilizers, which has contributed to over-fertilization of aquatic ecosystems when excess amounts are carried by runoff into local waterways. Researchers are trying to understand all of the various pathways and flows of each of the biogeochemical cycles in order to understand how human activities affect these cycles. While many important processes have been understood for more than century, there are many phenomena that scientists are just beginning to investigate. Satellite technology, among other tools, has revealed new information about interactions between the oceans and atmosphere that contribute to knowledge about the carbon cycle, but there remain many unanswered questions.  Global Biogeochemical Cycles and the Physical Climate System

<span style="background-color: #ffffff; color: #333333; font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 12px;">This module, written by Fred T. Mackenzie of the University of Hawaii, is a part of the Global Change Instruction Program. Presented by the University Corporation for Atmospheric Research, this module describes biogeochemical cycles and their role in climate. <span style="background-color: #ffffff; color: #55aa00; font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 13px; text-decoration: none;">Life and Biogeochemical Cycles

<span style="background-color: #ffffff; color: #333333; font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 12px;">This article, part of the California State University Monteray Bay's Ecosystem Service's website, offers an overview of biogeochemical cycles and highlights their relationship to climate, agricultural productivity, and acid precipitation. <span style="background-color: #ffffff; color: #55aa00; font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 13px; text-decoration: none;">Utah Education Network: Cycles

<span style="background-color: #ffffff; color: #333333; font-family: Verdana,Arial,Helvetica,sans-serif; font-size: 12px;">The UT Education Network Themepark website includes a section on biogeochemical cycles. The cycles page includes links to information on various cycles, including water, energy, seasonal, planetary cycles and animal and plant lifecycles. Each cycle page provides a list of online resources for additional information as well as links to teacher resources. [] = = =The Soil Cycle=

//by Hideki Inoue//
Organic agriculture is, in essence, how we nurture healthy soil. How can we help soil be fertile and vigorous? For the answer to this question, let me take you on a walk through a forest. We are walking along a forest trail. Stand under this big tree and pick up a twig. Dig lightly in the soil under the tree. What do you find? We can see decayed leaves, twigs, and flowers piled loosely in the soil. As we continue to dig, we find millions of insects and other tiny creatures living there together with plants. Their excrement and their carcasses combine with fallen leaves, decaying and enriching the soil. Leaves fall and decay. Twigs of trees are broken off by a strong wind. The trunks of trees are blown down and lie on the earth. Gradually, animals and plants begin to eat this organic matter. In due time, these tiny animals and plants also die and decay, and they become part of the soil, along with other organic wastes. Soon earthworms and ants eat these piles of rotting matter and they themselves return to the earth. It is this very process of decay which is the beginning of birth, an essential part of the natural circle of life. In my view, the word "nature" can be equated with this circle. I see this same principle in the Buddhist teaching of reincarnation. The meaning of the word "ecology" is, in essence, this natural circulation. Fertile and healthy soil can be made in the long, slow process of the natural life circle. In other words, the circle represents continuity as well as sustenance.

//Translated from Japanese by Tomomi Shugakuin. Hideki Inoue founded the Chikyujin Club, which supports the growing of agricultural products in harmony with nature and connects people who love and appreciate nature with their own health. (For more information about organic agriculture in Japan, see// CSA Roots in Japan //in this issue.)//