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An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.
In soil science, humus denominates the fraction of soil organic matter that is amorphous and without the "cellular cake structure characteristic of plants, micro-organisms or animals". Humus significantly affects the bulk density of soil and contributes to its retention of moisture and nutrients. Although the terms humus and compost are informally used interchangeably, they are distinct soil components with different origins; humus is created through anaerobic fermentation, while compost is the result of aerobic decomposition.
A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply one or more plant nutrients essential to the growth of plants. Many sources of fertilizer exist, both natural and industrially produced.
Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth's body of soil, called the pedosphere, has four important functions:
Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode according to the sources of energy and carbon, needed for living, growth and reproduction. The sources of energy can be light or chemical compounds; the sources of carbon can be of organic or inorganic origin.
Metalloprotein is a generic term for a protein that contains a metal ion cofactor. A large proportion of all proteins are part of this category. For instance, at least 1000 human proteins contain zinc-binding protein domains although there may be up to 3000 human zinc metalloproteins.
Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere. Bodies of living organisms begin to decompose shortly after death. Animals, such as worms, also help decompose the organic materials. Organisms that do this are known as decomposers. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy from the Greek word taphos, meaning tomb. Decomposition can also be a gradual process for organisms that have extended periods of dormancy.
Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial and aquatic environments. It is matter composed of organic compounds that have come from the remains of organisms such as plants and animals and their waste products in the environment. Organic molecules can also be made by chemical reactions that don't involve life. Basic structures are created from cellulose, tannin, cutin, and lignin, along with other various proteins, lipids, and carbohydrates. Organic matter is very important in the movement of nutrients in the environment and plays a role in water retention on the surface of the planet.
An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of metabolism, and generally low population density. Oligotrophic environments are those that offer little to sustain life. These environments include deep oceanic sediments, caves, glacial and polar ice, deep subsurface soil, aquifers, ocean waters, and leached soils.
The rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. The rhizosphere involving the soil pores contains many bacteria and other microorganisms that feed on sloughed-off plant cells, termed rhizodeposition, and the proteins and sugars released by roots, termed root exudates. This symbiosis leads to more complex interactions, influencing plant growth and competition for resources. Much of the nutrient cycling and disease suppression by antibiotics required by plants, occurs immediately adjacent to roots due to root exudates and metabolic products of symbiotic and pathogenic communities of microorganisms. The rhizosphere also provides space to produce allelochemicals to control neighbours and relatives. The plant-soil feedback loop and other physical factors occurring at the plant-root soil interface are important selective pressures for the communities and growth in the rhizosphere and rhizoplane.
Lithotrophs are a diverse group of organisms using an inorganic substrate to obtain reducing equivalents for use in biosynthesis or energy conservation via aerobic or anaerobic respiration. While lithotrophs in the broader sense include photolithotrophs like plants, chemolithotrophs are exclusively microorganisms; no known macrofauna possesses the ability to use inorganic compounds as electron sources. Macrofauna and lithotrophs can form symbiotic relationships, in which case the lithotrophs are called "prokaryotic symbionts". An example of this is chemolithotrophic bacteria in giant tube worms or plastids, which are organelles within plant cells that may have evolved from photolithotrophic cyanobacteria-like organisms. Chemolithotrophs belong to the domains Bacteria and Archaea. The term "lithotroph" was created from the Greek terms 'lithos' (rock) and 'troph' (consumer), meaning "eaters of rock". Many but not all lithoautotrophs are extremophiles.
Dissolved organic carbon (DOC) is the fraction of organic carbon operationally defined as that which can pass through a filter with a pore size typically between 0.22 and 0.7 micrometers. The fraction remaining on the filter is called particulate organic carbon (POC).
The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth. The production of phosphine gas occurs in only specialized, local conditions. Therefore, the phosphorus cycle should be viewed from whole Earth system and then specifically focused on the cycle in terrestrial and aquatic systems.
Soil organic matter (SOM) is the organic matter component of soil, consisting of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize. SOM provides numerous benefits to the physical and chemical properties of soil and its capacity to provide regulatory ecosystem services. SOM is especially critical for soil functions and quality.
Microbiology of decomposition is the study of all microorganisms involved in decomposition, the chemical and physical processes during which organic matter is broken down and reduced to its original elements.
A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cyclic. Mineral cycles include the carbon cycle, sulfur cycle, nitrogen cycle, water cycle, phosphorus cycle, oxygen cycle, among others that continually recycle along with other mineral nutrients into productive ecological nutrition.
Soil mesofauna are invertebrates between 0.1mm and 2mm in size, which live in the soil or in a leaf litter layer on the soil surface. Members of this group include nematodes, mites, springtails (collembola), proturans, pauropods, rotifers, tardigrades, small araneidae(spiders), pseudoscorpions, opiliones(harvestmen), enchytraeidae such as potworms, insect larvae, small isopods and myriapods They play an important part in the carbon cycle and are likely to be adversely affected by climate change.
Extracellular enzymes or exoenzymes are synthesized inside the cell and then secreted outside the cell, where their function is to break down complex macromolecules into smaller units to be taken up by the cell for growth and assimilation. These enzymes degrade complex organic matter such as cellulose and hemicellulose into simple sugars that enzyme-producing organisms use as a source of carbon, energy, and nutrients. Grouped as hydrolases, lyases, oxidoreductases and transferases, these extracellular enzymes control soil enzyme activity through efficient degradation of biopolymers.
A mycoparasite is an organism with the ability to be a parasite to fungi. A variety of fungicolous fungi have been found in nature, either as parasites, commensals or saprobes. Biotrophic mycoparasites get nutrients from living host cells. Necrotrophic mycoparasites rely on decayed matter.
Seventeen elements or nutrients are essential for plant growth and reproduction. They are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), nickel (Ni) and chlorine (Cl). Nutrients required for plants to complete their life cycle are considered essential nutrients. Nutrients that enhance the growth of plants but are not necessary to complete the plant's life cycle are considered non-essential. With the exception of carbon, hydrogen and oxygen, which are supplied by carbon dioxide and water, and nitrogen, provided through nitrogen fixation, the nutrients derive originally from the mineral component of the soil. The Law of the Minimum expresses that when the available form of a nutrient is not in enough proportion in the soil solution, then other nutrients cannot be taken up at an optimum rate by a plant. A particular nutrient ratio of the soil solution is thus mandatory for optimizing plant growth, a value which might differ from nutrient ratios calculated from plant composition.
References
- ↑ Ladd JN (1985). "Soil enzymes". In Vaughan D, Malcolm RE (eds.). Soil Organic Matter and Biological Activity. Developments in Plant and Soil Sciences. 16. Dordrecht: Springer. doi:10.1007/978-94-009-5105-1_6. ISBN 978-94-010-8757-5.
- ↑ Tabatabai MA (1994). "Chapter 37: Soil Enzymes". Methods of Soil Analysis: Part 2 Microbiological and Biochemical Properties. doi:10.2136/sssabookser5.2.c37. ISBN 9780891188100.
- ↑ Das SK, Varma A (2010). "Role of Enzymes in Maintaining Soil Health.". In Shukla G, Varma A (eds.). Soil Enzymology. Soil Biology. 22. Berlin, Heidelberg: Springer. doi:10.1007/978-3-642-14225-3_2. ISBN 978-3-642-14224-6.
- ↑ Burns RG, DeForest JL, Marxsen J, Sinsabaugh RL, Stromberger ME, Wallenstein MD, Weintraub MN, Zoppini A (March 2013). "Soil enzymes in a changing environment: current knowledge and future directions". Soil Biology and Biochemistry. 58: 216–34. doi:10.1016/j.soilbio.2012.11.009.
- ↑ Dotaniya ML (2019). "Chapter 33: Role of Soil Enzymes in Sustainable Crop Production.". Enzymes in Food Biotechnology. Academic Press. pp. 569–589. doi:10.1016/B978-0-12-813280-7.00033-5. ISBN 9780128132807.