View source for Decomposition

{{Short description|Process in which organic substances are broken down into simpler organic matter}}
{{Other uses}}
{{Signs of death}}
[[File:Strawberries time-lapse.ogv|thumb|Decomposition of [[strawberries]], reverse time lapse]]
[[File:005 Decomposing African buffalo skull in the Serengeti National Park (edit) Photo by Giles Laurent.jpg|alt=African buffalo skull decomposing in the Serengeti National Park, Tanzania|thumb|[[African buffalo]] skull decomposing in the [[Serengeti National Park]], Tanzania]]
[[File:Rotten apple under the tree.jpg|thumb|A rotten [[apple]] after it fell from a tree]]
[[File:Berge naturreservat omkullfallet liten tall.jpg|thumb|Decomposing fallen [[nurse log]] in a forest]]

'''Decomposition''' is the process by which dead [[organic substance]]s are broken down into simpler organic or inorganic matter such as [[carbon dioxide]], [[water]], [[simple sugars]] and [[mineral salt]]s. 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 [[organism]]s begin to decompose shortly after [[death]]. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. Decomposition can be a gradual process for organisms that have extended periods of [[dormancy]].<ref>{{cite journal |last1=Lynch |first1=Michael D. J. |last2=Neufeld |first2=Josh D. |year=2015 |title=Ecology and exploration of the rare biosphere |url=https://drive.google.com/file/d/1nSnl6GG2hZg96PZHqLD4hxdMThwfu-ND/view |journal=[[Nature Reviews Microbiology]] |volume=13 |issue=4 |pages=217–29 |doi=10.1038/nrmicro3400 |pmid=25730701 |s2cid=23683614 |access-date=1 January 2024|url-access=subscription }}</ref>

One can differentiate ''abiotic'' decomposition from ''biotic'' decomposition ([[biodegradation]]); the former means "the degradation of a substance by [[Chemical decomposition|chemical]] or physical processes", e.g., [[hydrolysis]]; the latter means "the metabolic breakdown of materials into simpler components by living organisms", typically by [[microorganism]]s. Animals, such as [[earthworm]]s, also help decompose the organic materials on and in soil through their activities. Organisms that do this are known as [[decomposer]]s or [[detritivore]]s.

The science which studies decomposition is generally referred to as ''[[taphonomy]]'' from the [[Greek language|Greek]] word '''''taphos''''', meaning tomb.

== In animals ==
{{For|human remains|corpse decomposition}}
[[Image:Ants cleaning dead snake.jpg|right|thumb|[[Ant]]s eating a dead [[snake]]]]

Decomposition begins at the moment of death, caused by two factors: [[Autolysis (biology)|autolysis]], the breaking down of [[tissue (biology)|tissue]]s by the body's own internal chemicals and [[enzyme]]s, and [[putrefaction]], the breakdown of tissues by [[bacteria]]. These processes release compounds such as [[cadaverine]] and [[putrescine]], that are the chief source of the unmistakably putrid [[odor]] of decaying animal tissue.<ref>{{cite book |year=2009 |title=Microbiology and aging |editor-last=Percival |editor-first=Steven L. |pages=313–34 |chapter=Decomposition of human remains |last1=Janaway |first1=Robert C. |last2=Percival |first2=Steven L. |last3=Wilson |first3=Andrew S. |doi=10.1007/978-1-59745-327-1_14 |isbn=978-1-59745-327-1 |publisher=[[Springer Science+Business Media|Springer]] |location=Dordrecht, The Netherlands |url=http://ndl.ethernet.edu.et/bitstream/123456789/25225/1/338.pdf#page=318 |access-date=7 January 2024 }}</ref>

Prime decomposers are [[bacteria]] or [[fungi]], though larger [[scavenger]]s also play an important role in decomposition if the body is accessible to [[insect]]s, [[Acari|mites]] and other animals. Additionally,<ref>{{cite journal |doi=10.1111/j.1365-2486.2008.01672.x |title=Global decomposition experiment shows soil animal impacts on decomposition are climate-dependent |year=2008 |last1=Wall |first1=Diana H. |last2=Bradford |first2=Mark A. |last3=St. John |first3=Mark G. |last4=Trofymow |first4=John A. |last5=Behan-Pelletier |first5=Valerie |last6=Bignell | first6=David E. |last7=Dangerfield |first7=J. Mark |last8=Parton |first8=William J. |last9=Rusek |first9=Josef |last10=Voigt |first10=Winfried |last11=Wolters |first11=Volkmar |last12=Gardel |first12=Holley Zadeh |last13=Ayuke |first13=Fred O. |last14=Bashford |first14=Richard |last15=Beljakova |first15=Olga I. |last16=Bohlen |first16=Patrick J. |last17=Brauman |first17=Alain |last18=Flemming |first18=Stephen |last19=Henschel |first19=Joh R. |last20=Johnson |first20=Dan L. |last21=Jones |first21=T. Hefin |last22=Kovarova |first22=Marcela |last23=Kranabetter |first23=J. Marty |last24=Kutny |first24=Les |last25=Lin |first25=Kuo-Chuan |last26=Maryati |first26=Mohamed |last27=Masse |first27=Dominique |last28=Pokarzhevskii |first28=Andrei |last29=Rahman |first29=Homathevi |last30=Sabará |first30=Millor G. |last31=Salamon |first31=Jörg-Alfred |last32=Swift |first32=Michael J. |last33=Varela |first33=Amanda |last34=Vasconcelos |first34=Heraldo |last35=White |first35=Don |last36=Zou |first36=Xiaoming |journal=[[Global Change Biology]] |volume=14 |issue=11 |pages=2661–77 |bibcode=2008GCBio..14.2661W |s2cid=18613932 |pmc=3597247 |url=https://www.researchgate.net/publication/227657300 |access-date=7 January 2024 }}</ref> soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. The most important arthropods that are involved in the process include [[carrion beetle]]s, mites,<ref>{{cite journal |last1=González Medina |first1=Alejandro |last2=González Herrera |first2=Lucas |last3=Perotti |first3=M. Alejandra |last4=Jiménez Ríos |first4=Gilberto |title=Occurrence of ''Poecilochirus austroasiaticus'' (Acari: Parasitidae) in forensic autopsies and its application on postmortem interval estimation |journal=[[Experimental and Applied Acarology]] |year=2013 |volume=59 |issue=3 |pages=297–305 |doi=10.1007/s10493-012-9606-1 |pmid=22914911 |s2cid=16228053 |url=https://www.researchgate.net/publication/230722630 |access-date=7 January 2024 }}</ref><ref>{{cite journal |last1=Braig |first1=Henk R. |last2=Perotti |first2=M. Alejandra |title=Carcases and mites |journal=[[Experimental and Applied Acarology]] |year=2009 |volume=49 |issue=1–2 |pages=45–84 |doi=10.1007/s10493-009-9287-6 |pmid=19629724 |s2cid=8377711 |url=https://www.researchgate.net/publication/26692932 |access-date=7 January 2024 }}</ref> the [[flesh flies]] (Sarcophagidae) and blowflies ([[Calliphoridae]]), such as the [[Lucilia (fly)|green bottle flies]] seen in the summer. In North America, the most important non-insect animals that are typically involved in the process include mammal and bird scavengers, such as [[coyote]]s, [[dog]]s, [[wolves]], [[fox]]es, [[rat]]s, [[crow]]s and [[vulture]]s.<ref>{{cite book |last1=Beasley |first1=James C. |last2=Olson |first2=Zach H. |last3=DeVault |first3=Travis L. |year=2015 |chapter=Ecological role of vertebrate scavengers |title=Carrion ecology, evolution, and their applications |pages=107–27 |editor-last1=Benbow |editor-first1=M. Eric |editor-last2=Tomberlin |editor-first2=Jeffery K. |editor-last3=Tarone |editor-first3=Aaron M. |publisher=[[CRC Press]] |location=Boca Raton, Florida |isbn=978-1138893849 |chapter-url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2743&context=icwdm_usdanwrc |access-date=14 January 2024 }}</ref> Some of these scavengers also remove and scatter bones, which they ingest at a later time. Aquatic and marine environments have break-down agents that include bacteria, fish, crustaceans, [[Diptera|fly]] larvae<ref>{{cite journal |last1=González Medina |first1=Alejandro |last2=Soriano Hernando |first2=Óscar |last3=Jiménez Ríos |first3=Gilberto |title=The use of the developmental rate of the aquatic midge ''Chironomus riparius'' (Diptera, Chironomidae) in the assessment of the postsubmersion interval |journal=[[Journal of Forensic Sciences]] |year=2015 |volume=60 |issue=3 |pages=822–26 |doi=10.1111/1556-4029.12707 |pmid=25613586 |s2cid=7167656 |url=https://fr.zlib-articles.se/book/45079197/f0cebc |access-date=14 January 2024 |url-access=subscription |archive-date=14 January 2024 |archive-url=https://web.archive.org/web/20240114092231/https://fr.zlib-articles.se/book/45079197/f0cebc |url-status=dead }}</ref> and other carrion scavengers.

=== Stages of decomposition ===
Five general stages are typically used to describe the process of decomposition in vertebrate animals: fresh, bloat, active decay, advanced decay, and dry/remains.<ref name=Payne>{{cite journal |doi=10.2307/1934999 |last=Payne |first=Jerry A. |title=A summer carrion study of the baby pig ''Sus scrofa'' Linnaeus |journal=Ecology |volume=46 |issue=5 |pages=592–602 |year=1965 |jstor=1934999 |bibcode=1965Ecol...46..592P |url=https://esajournals.onlinelibrary.wiley.com/doi/10.2307/1934999 |access-date=21 January 2024 |url-access=subscription }}</ref> The general stages of decomposition are coupled with two stages of chemical decomposition: [[Autolysis (biology)|autolysis]] and [[putrefaction]].<ref name=Forbes>{{cite book |last=Forbes |first=Shari L. |editor-last1=Tibbett |editor-first1=Mark |editor-last2=Carter |editor-first2=David O. |title=Soil analysis in forensic taphonomy: chemical and biological effects of buried human remains |url=https://www.researchgate.net/publication/279954445_Decomposition_Chemistry_in_a_Burial_Environment |publisher=[[CRC Press]] |location=Boca Raton, Florida |year=2008 |pages=203–23 |chapter=Decomposition chemistry in a burial environment |isbn=978-1-4200-6991-4 |access-date=21 January 2024 |url-access=subscription}}</ref> These two stages contribute to the [[chemical process of decomposition]], which breaks down the main components of the body. With death the [[microbiome]] of the living organism collapses and is followed by the [[necrobiome]] that undergoes predictable changes over time.<ref>{{cite journal |last1=Lawrence |first1=Kelsey E. |last2=Lam |first2=Khiem C. |last3=Morgun |first3=Andrey |last4=Shulzhenko |first4=Natalia |last5=Löhr |first5=Christiane V. |title=Effect of temperature and time on the thanatomicrobiome of the cecum, ileum, kidney, and lung of domestic rabbits |journal=[[Journal of Veterinary Diagnostic Investigation]] |year=2019 |volume=31 |issue=2 |pages=155–63 |doi=10.1177/1040638719828412 |doi-access=free |pmid=30741115 |pmc=6838823 }}</ref>

==== Fresh ====
Among those animals that have a heart, the ''fresh'' stage begins immediately after the heart stops beating. From the moment of death, the body begins cooling or warming to match the temperature of the ambient environment, during a stage called [[algor mortis]]. Shortly after death, within three to six hours, the muscular tissues become rigid and incapable of relaxing, during a stage called [[rigor mortis]]. Since blood is no longer being pumped through the body, [[gravity]] causes it to drain to the dependent portions of the body, creating an overall bluish-purple discoloration termed [[livor mortis]] or, more commonly, lividity. Depending on the position of the body, these parts would vary. For instance, if the person was flat on their back when they died, the blood would collect in the parts that are touching the ground. If the person was hanging, it would collect in their fingertips, toes and earlobes.<ref>{{cite journal |last=Goff |first=M. Lee |title=Early post-mortem changes and stages of decomposition in exposed cadavers |journal=[[Experimental and Applied Acarology]] |year=2009 |volume=49 |issue=1–2 |pages=21–36 |doi=10.1007/s10493-009-9284-9 |pmid=19554461 |url=https://fr.zlib-articles.se/book/7859934/d5a083 |access-date=24 March 2024 |url-access=subscription |archive-date=24 March 2024 |archive-url=https://web.archive.org/web/20240324091324/https://fr.zlib-articles.se/book/7859934/d5a083 |url-status=dead }}</ref>

Once the heart stops, the [[blood]] can no longer supply [[oxygen]] or remove [[carbon dioxide]] from the tissues. The resulting decrease in pH and other chemical changes cause cells to lose their [[structural integrity]], bringing about the release of cellular enzymes capable of initiating the breakdown of surrounding cells and tissues. This process is known as [[Autolysis (biology)|autolysis]].<ref>{{cite journal |last1=Laiho |first1=Kauno |last2=Penttilä |first2=Antti |title=Autolytic changes in blood cells and other tissue cells of human cadavers. I. Viability and ion studies |journal=[[Forensic Science International]] |year=1981 |volume=17 |issue=2 |pages=109–20 |doi=10.1016/0379-0738(81)90003-7 |pmid=7239364 |url=https://fr.zlib-articles.se/book/13178726/c77250 |access-date=24 March 2024 |url-access=subscription |archive-date=28 March 2024 |archive-url=https://web.archive.org/web/20240328122355/https://fr.zlib-articles.se/book/13178726/c77250 |url-status=dead }}</ref>

Visible changes caused by decomposition are limited during the fresh stage, although autolysis may cause [[blister]]s to appear at the surface of the skin.<ref>{{cite book |last1=Saukko |first1=Pekka |last2=Knight |first2=Bernard |title=Knight's forensic pathology |edition=3rd |publisher=[[CRC Press]] |location=Boca Raton, Florida |year=2013 |isbn=978-0340760444 |url=https://z-library.se/book/1245298/52efce |access-date=21 January 2024 }}</ref>

The small amount of oxygen remaining in the body is quickly depleted by cellular [[metabolism]] and [[aerobic microbe]]s naturally present in [[respiratory tract|respiratory]] and [[gastrointestinal tract|gastrointestinal]] tracts, creating an ideal environment for the proliferation of [[anaerobic organism]]s. These multiply, consuming the body's [[carbohydrate]]s, [[lipid]]s and [[protein]]s, to produce a variety of substances including [[propionic acid]], [[lactic acid]], [[methane]], [[hydrogen sulfide]] and [[ammonia]]. The process of microbial proliferation within a body is referred to as [[putrefaction]] and leads to the second stage of decomposition known as bloat.<ref name=Carterjournal>{{cite journal |last1=Carter |first1=David O. |last2= Yellowlees |first2=David |last3=Tibbett |first3=Mark |title=Cadaver decomposition in terrestrial ecosystems |journal=[[Naturwissenschaften]] |volume=94 |issue=1 |pages=12–24 |year=2007 |pmid=17091303 |doi=10.1007/s00114-006-0159-1 |url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1256&context=entomologyfacpub |bibcode=2007NW.....94...12C |s2cid=13518728 |access-date=28 January 2024 }}</ref>

[[Blowflies]] and [[flesh flies]] are the first carrion insects to arrive and they seek a suitable [[oviposition]] site.<ref name=Payne/>

==== {{anchor|Bloat|bloat|Bloat stage|Bloated|bloated|bloating|Bloating}} Bloat ====
The [[Bloating|bloat]] stage provides the first clear visual sign that microbial proliferation is underway. In this stage, [[Anaerobic respiration|anaerobic metabolism]] takes place, leading to the accumulation of gases, such as [[hydrogen sulphide|hydrogen sulfide]], [[carbon dioxide]], [[methane]] and [[nitrogen]]. The accumulation of gases within the bodily cavity causes the distention of the abdomen and gives a cadaver its overall bloated appearance.<ref name=Carterbook>{{cite book |last1=Carter |first1=David O. |last2=Tibbett |first2=Mark |editor-last1=Tibbett |editor-first1=Mark |editor-last2=Carter |editor-first2=David O. |title=Soil analysis in forensic taphonomy: chemical and biological effects of buried human remains |chapter-url=https://zlib-articles.se/book/62451636/37bb53 |publisher=[[CRC Press]] |location=Boca Raton, Florida |year=2008 |pages=29–51 |chapter=Cadaver decomposition and soil: processes |isbn=978-1-4200-6991-4 |access-date=28 January 2024 |archive-date=28 January 2024 |archive-url=https://web.archive.org/web/20240128090636/https://zlib-articles.se/book/62451636/37bb53 |url-status=dead }}</ref> The gases produced also cause natural liquids and liquefying tissues to become frothy.<ref name="Janaway">{{cite book |last1=Janaway |first1=Robert C. |last2=Percival |first2=Stephen L. |last3=Wilson |first3=Andrew S. |title=Microbiology and aging: clinical manifestations |publisher=[[Springer Science+Business Media|Springer Science + Business]] |year=2009 |isbn=978-1-58829-640-5 |editor-last=Percival |editor-first=Steven L. |pages=313–34 |chapter=Decomposition of human remains |chapter-url=https://www.researchgate.net/publication/225914421 |access-date=28 January 2024 |doi=10.1007/978-1-59745-327-1_14 }}</ref> As the pressure of the gases within the body increases, fluids are forced to escape from natural orifices, such as the nose, mouth and anus, and enter the surrounding environment. The buildup of pressure combined with the loss of integrity of the skin may also cause the body to rupture.<ref name=Carterbook/>

Intestinal anaerobic bacteria transform [[haemoglobin]] into [[sulfhemoglobin]] and other colored pigments. The associated gases which accumulate within the body at this time aid in the transport of sulfhemoglobin throughout the body via the [[Circulatory system|circulatory]] and [[lymphatic system]]s, giving the body an overall marbled appearance.<ref name=Pinheiro>{{cite book |last=Pinheiro |first=João |editor-last1=Schmidt |editor-first1=Aurore |editor-last2=Cunha |editor-first2=Eugénia |editor-last3=Pinheiro |editor-first3=João |title=Forensic anthropology and medicine: complementary sciences from recovery to cause of death |chapter-url=https://zlib-articles.se/book/28457377/a6837e |publisher=[[Humana Press]] |year=2006 |pages=85–116 |chapter=Decay process of a cadaver |isbn=978-1-58829-824-9 |doi=10.1007/978-1-59745-099-7_5 |location=Totowa, New Jersey |access-date=28 January 2024 |archive-date=28 January 2024 |archive-url=https://web.archive.org/web/20240128090637/https://zlib-articles.se/book/28457377/a6837e |url-status=dead }}</ref>

If insects have access, [[maggot]]s hatch and begin to feed on the body's tissues.<ref name= Payne/> Maggot activity, typically confined to natural orifices, and masses under the skin, causes the skin to slip, and hair to detach from the skin.<ref name= Janaway/> Maggot feeding, and the accumulation of gases within the body, eventually leads to post-mortem skin ruptures which will then further allow purging of gases and fluids into the surrounding environment.<ref name=Carterjournal/> Ruptures in the skin allow oxygen to re-enter the body and provide more surface area for the development of fly larvae and the activity of aerobic microorganisms.<ref name=Carterbook/> The purging of gases and fluids results in the strong distinctive odors associated with decay.<ref name=Payne/>

==== Active decay ====
Active decay is characterized by the period of greatest mass loss. This loss occurs as a result of both the voracious feeding of maggots and the purging of decomposition fluids into the surrounding environment.<ref name= Carterbook/> The purged fluids accumulate around the body and create a cadaver decomposition island (CDI).<ref>{{cite journal |last1=Fancher |first1=James P. |last2=Aitkenhead-Peterson |first2=Jacqueline A. |last3=Farris |first3=Travis |last4=Mix |first4=Ken |last5=Schwab |first5=Arthur Paul |last6=Wescott |first6=Daniel J. |last7=Hamilton |first7=Michelle D. |title=An evaluation of soil chemistry in human cadaver decomposition islands: potential for estimating postmortem interval (PMI) |journal=[[Forensic Science International]] |year=2017 |volume=279 |issue=1 |pages=130–139 |doi=10.1016/j.forsciint.2017.08.002 |pmid=28866239 |url=https://zlib-articles.se/book/66742635/803f8f |access-date=4 February 2024 |url-access=subscription |archive-date=4 February 2024 |archive-url=https://web.archive.org/web/20240204092049/https://zlib-articles.se/book/66742635/803f8f |url-status=dead }}</ref> Liquefaction of tissues and disintegration become apparent during this time and strong odors persist.<ref name= Payne/> The end of active decay is signaled by the migration of maggots away from the body to pupate.<ref name= Carterjournal/>

==== Advanced decay ====
Decomposition is largely inhibited during advanced decay due to the loss of readily available cadaveric material.<ref name= Carterbook/> Insect activity is also reduced during this stage.<ref name=Janaway/> When the carcass is located on soil, the area surrounding it will show evidence of [[vegetation]] death.<ref name=Carterbook/> The CDI surrounding the carcass will display an increase in [[soil carbon]] and nutrients such as [[phosphorus]], [[potassium]], [[calcium]] and [[magnesium]];<ref name=Carterjournal/> changes in pH; and a significant increase in soil [[nitrogen]].<ref name=Vass>{{cite journal |last1=Vass |first1=Arpad A. |last2=Bass |first2=William M. |last3=Volt |first3=Jeffrey D. |last4=Foss |first4=John E. |last5=Ammons |first5=John T. |title=Time since death determinations of human cadavers using soil solution |journal=[[Journal of Forensic Sciences]] |volume=37 |issue=5 |pages=1236–53 |year=1992 |pmid=1402750 |doi=10.1520/JFS13311J }}</ref>

==== Dry/remains ====
As the ecosystem recovers from the disturbance, the CDI moves into the dry/remains stage, which is characterized by a decrease in the intensity of the disturbance and an increase in the amount of plant growth around the affected area. This is a sign that the nutrients and other ecological resources present in the surrounding soil have not yet returned to their normal levels.

During this stage, it is important to monitor the ecosystem for any signs of continued disturbance or ecological stress. The resurgence of plant growth is a positive sign, but it may take several years for the ecosystem to fully recover and return to its pre-disturbance state.<ref name=Carterbook/> All that remains of the cadaver at this stage is dry skin, [[cartilage]], and [[bone]]s,<ref name=Payne/> which will become dry and bleached if exposed to the elements.<ref name= Janaway/> If all soft tissue is removed from the cadaver, it is referred to as completely [[Skeletonization|skeletonized]], but if only portions of the bones are exposed, it is referred to as partially skeletonized.<ref name=Dent>{{cite journal |author1=Dent B.B. |author2=Forbes S.L. |author3=Stuart B.H. |title=Review of human decomposition processes in soil |journal=[[Environmental Earth Sciences|Environmental Geology]] |volume=45 |issue=4 |pages=576–585|doi=10.1007/s00254-003-0913-z |year=2004 |s2cid=129020735 |url=https://www.academia.edu/101465919 |access-date=4 February 2024 }}</ref>

[[Image:decomposition stages.jpg|thumb|center|Pig carcass in the different stages of decomposition: fresh, bloat, active decay, advanced decay and dry remains]]

== Factors affecting decomposition of bodies ==
{{Further|Forensic entomology}}

=== Exposure to the elements ===
A dead body that has been exposed to the open elements, such as water and air, will decompose more quickly and attract much more [[insect]] activity than a body that is buried<ref>{{cite journal |last1=Schotsmans |first1=Eline M.J. |last2=Van de Voorde |first2=Wim |last3=De Winne |first3=Joan |last4=Wilson |first4=Andrew S. |title=The impact of shallow burial on differential decomposition to the body: a temperate case study |journal=[[Forensic Science International]] |year=2011 |volume=206 |issue=1 |pages=e43–e48 |doi=10.1016/j.forsciint.2010.07.036 |pmid=20728294 |url=https://www.academia.edu/35968921 |access-date=11 February 2024 }}</ref> or confined in special protective gear or artifacts.<ref>{{cite journal |last1=Matuszewski |first1=Szymon |last2=Konwerski |first2=Szymon |last3=Frątczak |first3=Katarzyna |last4=Szafałowicz |first4=Michał |title=Effect of body mass and clothing on decomposition of pig carcasses |journal=[[International Journal of Legal Medicine]] |year=2014 |volume=128 |issue=1 |pages=1039–48 |doi=10.1007/s00414-014-0965-5 |pmid=24487775 |pmc=4196037 |url=https://link.springer.com/content/pdf/10.1007/s00414-014-0965-5.pdf |access-date=11 February 2024 }}</ref> This is due, in part, to the limited number of insects that can penetrate soil<ref>{{cite journal |last1=Simmons |first1=Tal |last2=Cross |first2=Peter A. |last3=Adlam |first3=Rachel E. |last4=Moffatt |first4=Colin |title=The inﬂuence of insects on decomposition rate in buried and surface remains |journal=[[Journal of Forensic Sciences]] |year=2010 |volume=55 |issue=4 |pages=889–92 |doi=10.1111/j.1556-4029.2010.01402.x |pmid=20412365 |url=https://www.academia.edu/51957162 |access-date=11 February 2024 }}</ref> and the lower temperatures under the soil.<ref>{{cite journal |last1=Prangnell |first1=Jonathan |last2=McGowan |first2=Glenys |title=Soil temperature calculation for burial site analysis |journal=[[Forensic Science International]] |year=2009 |volume=191 |issue=1 |pages=104–09 |doi=10.1016/j.forsciint.2009.07.002 |pmid=19656646 |url=https://www.academia.edu/88338199 |access-date=11 February 2024 }}</ref>

The rate and manner of decomposition in an animal body are strongly affected by several factors. In roughly descending degrees of importance,<ref>{{cite journal |last1=Dash |first1=Hirak Ranjan |last2=Das |first2=Surajit |title=Thanatomicrobiome and epinecrotic community signatures for estimation of post-mortem time interval in human cadaver |journal=[[Applied Microbiology and Biotechnology]] |date=November 2020 |volume=104 |issue=22 |pages=9497–9512 |doi=10.1007/s00253-020-10922-3 |pmid=33001249 |s2cid=222173345 |url=https://zlib-articles.se/book/83813953/10636c |access-date=18 February 2024 |url-access=subscription |archive-date=18 February 2024 |archive-url=https://web.archive.org/web/20240218091157/https://zlib-articles.se/book/83813953/10636c |url-status=dead }}</ref> they are:
* [[Temperature]];
* The availability of [[oxygen]];
* Prior [[embalming]];
* [[List of causes of death by rate|Cause of death]];
* [[Burial]], depth of burial, and [[soil type]];
* Access by [[scavenger]]s;
* [[Physical trauma|Trauma]], including [[wound]]s and crushing blows;
* [[Humidity]], or wetness;
* [[Rain]]fall;
* Body size and weight;
* Composition;
* [[Clothing]];
* The surface on which the body rests;
* Foods/objects inside the specimen's [[digestive tract]] ([[bacon]] compared to [[lettuce]]).

The speed at which decomposition occurs varies greatly. Factors such as temperature, humidity, and the season of death all determine how fast a fresh body will [[Skeletonization|skeletonize]] or [[Mummy|mummify]]. A basic guide for the effect of environment on decomposition is given as [[Johann Ludwig Casper|Casper]]'s Law (or Ratio): if all other factors are equal, then, when there is free access of air a body decomposes twice as fast as if immersed in water and eight times faster than if buried in the earth. Ultimately, the rate of bacterial decomposition acting on the tissue will depend upon the temperature of the surroundings. Colder temperatures decrease the rate of decomposition while warmer temperatures increase it. A dry body will not decompose efficiently. Moisture helps the growth of microorganisms that decompose the organic matter, but too much moisture could lead to anaerobic conditions slowing down the decomposition process.<ref>{{cite book |last=Casper |first=Johann Ludwig |title=A handbook of the practice of forensic medicine, based upon personal experience |publisher=The New Sydenham Society |location=London, United Kingdom |year=1861 |url=https://archive.org/details/handbookofpracti02casp/page/n3/mode/2up |access-date=18 February 2024 }}</ref>

The most important variable is the body's accessibility to insects, particularly [[flies]]. On the surface in tropical areas, invertebrates alone can easily reduce a fully fleshed corpse to clean bones in under two weeks.<ref>{{cite journal |last1=Ramos-Pastrana |first1=Yardany |last2=Virgüez-Díaz |first2=Yenny |last3=Wolff |first3=Marta |title=Insects of forensic importance associated to cadaveric decomposition in a rural area of the Andean Amazon, Caquetá, Colombia |journal=Acta Amazonica |year=2018 |volume=48 |issue=2 |pages=126–36 |doi=10.1590/1809-4392201701033 |url=https://www.researchgate.net/publication/325109425 |access-date=18 February 2024 |doi-access=free |bibcode=2018AcAma..48..126R }}</ref> The skeleton itself is not permanent; [[acid]]s in [[soil]]s can reduce it to unrecognizable components.<ref>{{cite journal |last=Nicholson |first=Rebecca A. |title=Bone degradation, burial medium and species representation: debunking the myths, an experiment-based approach |journal=[[Journal of Archaeological Science]] |year=1996 |volume=23 |issue=4 |pages=513–33 |doi=10.1006/jasc.1996.0049 |bibcode=1996JArSc..23..513N |url=https://www.academia.edu/12346612 |access-date=25 February 2024 }}</ref> This is one reason given for the lack of human remains found in the wreckage of the [[RMS Titanic|''Titanic'']], even in parts of the ship considered inaccessible to scavengers.<ref>{{cite journal |last=Bier |first=Jess |title=Bodily circulation and the measure of a life: forensic identification and valuation after the Titanic disaster |journal=[[Social Studies of Science]] |year=2018 |volume=48 |issue=5 |pages=635–62 |doi=10.1177/0306312718801173 |pmid=30253686 |pmc=6193206 }}</ref> Freshly skeletonized bone is often called ''green'' bone and has a characteristic greasy feel.<ref>{{cite journal |last1=Huculak |first1=Meaghan A. |last2=Rogers |first2=Tracy L. |title=Reconstructing the sequence of events surrounding body disposition based on color staining of bone |journal=[[Journal of Forensic Sciences]] |year=2009 |volume=54 |issue=5 |pages=979–84 |doi=10.1111/j.1556-4029.2009.01086.x |pmid=19549030 |url=https://www.academia.edu/98952752 |access-date=25 February 2024 }}</ref> Under certain conditions (underwater, but also cool, damp soil), bodies may undergo [[saponification]] and develop a waxy substance called [[adipocere]], caused by the action of soil chemicals on the body's [[protein]]s and [[fat]]s. The formation of adipocere slows decomposition by inhibiting the bacteria that cause putrefaction.<ref>{{cite journal |last1=Magni |first1=Paola A. |last2=Lawn |first2=Jessica |last3=Guareschi |first3=Edda E. |title=A practical review of adipocere: key findings, case studies and operational considerations from crime scene to autopsy |journal=[[Journal of Forensic and Legal Medicine]] |year=2021 |volume=78 |issue=102109 |doi=10.1016/j.jflm.2020.102109 |pmid=33596512 |url=https://www.academia.edu/95395073 |access-date=3 March 2024 |archive-date=3 March 2024 |archive-url=https://web.archive.org/web/20240303092839/https://www.academia.edu/95395073 |url-status=dead }}</ref>

In extremely dry or cold conditions, the normal process of decomposition is halted—by either lack of moisture or temperature controls on bacterial and enzymatic action—causing the body to be preserved as a [[mummy]]. Frozen mummies commonly restart the decomposition process when thawed (see [[Ötzi the Iceman]]), whilst heat-desiccated mummies remain so unless exposed to moisture.<ref>{{cite book |last1=Piombino-Mascali |first1=Dario |last2=Gill-Frerking |first2=Heather |last3=Beckett |first3=Ronald G. |title=Taphonomy of human remains: forensic analysis of the dead and the depositional environment |publisher=[[Wiley (publisher)|John Wiley & Sons]] |location=Hoboken, New Jersey |year=2017 |isbn=978-1118953327 |editor-last1=Schotsmans |editor-first1=Eline M. J. |editor-last2=Márquez-Grant |editor-first2=Nicholas |editor-last3=Forbes |editor-first3=Shari L. |pages=101–19 |chapter=The taphonomy of natural mummies |chapter-url=https://zlib-articles.se/book/64223562/e2e2ef |access-date=3 March 2024 |doi=10.1002/9781118953358.ch8 |archive-date=3 March 2024 |archive-url=https://web.archive.org/web/20240303093712/https://zlib-articles.se/book/64223562/e2e2ef |url-status=dead }}</ref>

The bodies of newborns who never ingested food are an important exception to the normal process of decomposition. They lack the internal microbial flora that produces much of decomposition<ref>{{cite journal |last=Bezirtzoglou |first=Eugenia |title=The intestinal microflora during the first weeks of life |journal=Anaerobe |year=1997 |volume=3 |issue=2–3 |pages=173–77 |doi=10.1006/anae.1997.0102 |pmid=16887585 |url=https://www.academia.edu/23875942 |access-date=10 March 2024 }}</ref> and quite commonly mummify if kept in even moderately dry conditions.<ref>{{cite journal |last1=Hau |first1=Teo Chee |last2=Hamzah |first2=Noor Hazfalinda |last3=Lian |first3=Hing Hiang |last4=Hamzah |first4=Sri Pawita Albakri Amir |title=Decomposition process and post mortem changes: review |journal=Sains Malaysiana |year=2014 |volume=43 |issue=12 |pages=1873–82 |doi=10.17576/jsm-2014-4312-08 |doi-access=free }}</ref>

=== Anaerobic vs aerobic ===
Aerobic decomposition takes place in the presence of oxygen. This is most common to occur in nature. Living organisms that use oxygen to survive feed on the body. [[Anaerobic decomposition]] takes place in the absence of oxygen. This could be a place where the body is buried in organic material and oxygen cannot reach it. This process of [[putrefaction]] has a bad odor accompanied by it due to the [[hydrogen sulfide]] and organic matter containing sulfur.<ref name=":2">{{cite web |url=http://aggie-horticulture.tamu.edu/earthkind/landscape/dont-bag-it/chapter-1-the-decomposition-process/ |title=The decomposition process |website=[[Aggie Horticulture]] |language=en |access-date=17 March 2024 }}</ref>

=== Artificial preservation ===
[[Embalming]] is the practice of delaying the decomposition of human and animal remains. Embalming slows decomposition somewhat but does not forestall it indefinitely. Embalmers typically pay great attention to parts of the body seen by [[mourner]]s, such as the face and hands. The chemicals used in embalming repel most insects and slow down bacterial putrefaction by either killing existing bacteria in or on the body themselves<ref>{{cite journal |last1=Barnes |first1=Kate M. |last2=Whiffin |first2=Ashleigh L. |last3=Bulling |first3=Mark T. |title=A preliminary study on the antibacterial activity and insect repellent properties of embalming fluids from the 18th Dynasty (1550–1292 BCE) in ancient Egypt |journal=Journal of Archaeological Science: Reports |year=2019 |volume=25 |issue=June 2019 |pages=600–09 |doi=10.1016/j.jasrep.2019.05.032 |bibcode=2019JArSR..25..600B |url=https://fr.zlib-articles.se/book/75956349/b70666 |access-date=17 March 2024 |url-access=subscription |archive-date=17 March 2024 |archive-url=https://web.archive.org/web/20240317090923/https://fr.zlib-articles.se/book/75956349/b70666 |url-status=dead }}</ref> or by [[Fixation (histology)|fixing]] cellular proteins, which means that they cannot act as a nutrient source for subsequent bacterial infections.<ref name=Ajileye>{{cite journal |last1=Ajileye |first1=Ayodeji Blessing |last2=Esan |first2=Ebenezer Olubunmi |last3=Adeyemi |first3=Oluwakemi Abidemi |title=Human embalming techniques: a review |journal=American Journal of Biomedical Sciences |year=2018 |volume=10 |issue=2 |pages=82–95 |doi=10.5099/aj180200082 |url=https://www.nwpii.com/ajbms/papers/AJ20180203.pdf |access-date=17 March 2024 }}</ref> In sufficiently dry environments, an embalmed body may end up [[mummified]] and it is not uncommon for bodies to remain preserved to a viewable extent after decades.<ref>{{cite journal |last=Lynerup |first=Niels |title=Mummies |journal=[[Yearbook of Physical Anthropology]] |year=2007 |volume=50 |pages=162–90 |doi=10.1002/ajpa.20728 |pmid=18046750 |url=https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ajpa.20728 |access-date=17 March 2024 }}</ref> Notable viewable embalmed bodies include those of:
* [[Eva Perón]] of [[Argentina]], whose body was injected with [[paraffin wax|paraffin]], was kept perfectly preserved for many years, and still is as far as is known (her body is no longer on public display).<ref>{{cite web |title=Radiological exploration of the embalmed cadaver of Eva Peron |last1=Gotta |first1=Cesar H. |last2=Buzzi |first2=Alfredo E. |url=https://epos.myesr.org/poster/esr/ecr2004/C-082 |website=[[European Society of Radiology]] |date=5 March 2004 |location=Vienna, Austria |access-date=31 March 2024 }}</ref>
* [[Vladimir Lenin]] of the [[Soviet Union]], whose body was kept submerged in a special tank of fluid for decades and is on public display in [[Lenin's Mausoleum]].<ref>{{cite journal |last=Vronskaya |first=Alla G. |title=Shaping eternity: the preservation of Lenin's body |journal=Thresholds |year=2010 |volume=38 |pages=10–13 |doi=10.1162/thld_a_00170 |url=https://www.academia.edu/905263 |access-date=31 March 2024 }}</ref>
** Other [[Communist]] leaders with pronounced [[cults of personality]] such as [[Mao Zedong]], [[Kim Il Sung]], [[Ho Chi Minh]], [[Kim Jong Il]] and most recently [[Hugo Chávez]] have also had their cadavers preserved in the fashion of Lenin's preservation and are now displayed in their respective [[mausoleum]]s.
* [[Pope John XXIII]], whose preserved body can be viewed in [[St. Peter's Basilica]].
* [[Padre Pio]], whose body was injected with [[formalin]] before burial in a dry vault from which he was later removed and placed on public display at the [[San Giovanni Rotondo]].<ref>{{cite book |last=Milicia |first=Maria Teresa |title=Public uses of human remains and relics in history |publisher=[[Routledge]] |location=Abingdon-on-Thames, United Kingdom |year=2020 |isbn=978-0-429-29590-4 |editor-last1=Cavicchioli |editor-first1=Silvia |editor-last2=Provero |editor-first2=Luigi |pages=101–19 |chapter=Simulacra of eternal life: ostensions, exhibitions and the concealment of human remains |chapter-url=https://www.academia.edu/44692671 |access-date=7 April 2024 }}</ref>

=== Environmental preservation ===
A body buried in a sufficiently dry environment may be well preserved for decades. This was observed in the case for murdered [[Civil rights movement|civil rights]] activist [[Medgar Evers]], who was found to be almost perfectly preserved over 30 years after his death, permitting an accurate [[autopsy]] when the case of his murder was re-opened in the 1990s.<ref>{{cite book |last=Quigley |first=Christine |title=Modern mummies: the preservation of the human body in the twentieth century |publisher=[[McFarland & Company|McFarland]] |location=Jefferson, North Carolina |year=2006 |pages=213–214 |isbn=978-1-4766-1373-4 |url=https://archive.org/details/modernmummiespre0000chri/page/212/mode/2up |access-date=14 April 2024 }}</ref>

Bodies submerged in a [[peat]] [[bog]] may become naturally [[embalmed]], arresting decomposition and resulting in a preserved specimen known as a [[bog body]]. The generally cool and anoxic conditions in these environments limits the rate of microbial activity, thus limiting the potential for decomposition.<ref>{{cite book |last1=Moore |first1=Tim |last2=Basiliko |first2=Nate |chapter=Decomposition in boreal peatlands |year=2006 |title=Boreal peatland ecosystems |pages=125–143 |editor1-last=Wieder |editor1-first=R. Kelman |editor2-last=Vitt |editor2-first=Dale H. |series=Ecological Studies |publisher=Springer |language=en |doi=10.1007/978-3-540-31913-9_7 |isbn=978-3-540-31913-9 |volume=188 |chapter-url=https://fr.zlib-articles.se/book/11567551/5b2d48 |access-date=14 April 2024 }}{{Dead link|date=June 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> The time for an embalmed body to be reduced to a [[skeleton]] varies greatly. Even when a body is decomposed, embalming treatment can still be achieved (the arterial system decays more slowly) but would not restore a natural appearance without extensive reconstruction and cosmetic work, and is largely used to control the foul odors due to decomposition.<ref name=Ajileye/>

An animal can be preserved almost perfectly, for millions of years in a resin such as [[amber]].<ref>{{cite book |last1=Weitschat |first1=Wilfried |last2=Wichard |first2=Wolfgang |title=Atlas of plants and animals in Baltic amber |publisher=Verlag Dr. Friedrich Pfeil |location=Munich, Germany |year=2002 |isbn=978-3931516949 |url=https://fr.z-library.se/book/675054/ae1dc0 |access-date=14 April 2024 }}</ref>

There are some examples where bodies have been inexplicably preserved (with no human intervention) for decades or centuries and appear almost the same as when they died. In some religious groups, this is known as [[incorruptibility]]. It is not known whether or for how long a body can stay free of decay without artificial preservation.<ref>{{cite web |url=https://people.howstuffworks.com/incorruptible.htm |title=How can a corpse be incorruptible? |first=Josh |last=Clark |publisher=[[HowStuffWorks]] |location=Marina Del Rey, California |date=2023-08-23 |access-date=14 April 2024 }}</ref>

=== Importance to forensic sciences ===
{{Further|Forensic entomological decomposition}}

Various sciences study the decomposition of bodies under the general rubric of [[forensic science]] because the usual motive for such studies is to determine the time and cause of death for [[legal]] purposes:
* Forensic [[taphonomy]] specifically studies the processes of decomposition to apply the biological and chemical principles to forensic cases to determine [[post-mortem interval]] (PMI), post-burial interval as well as to locate clandestine graves.
* [[Forensic pathology]] studies the clues to the cause of death found in the corpse as a [[medical]] phenomenon.
* [[Forensic entomology]] studies the insects and other [[vermin]] found in corpses; the sequence in which they appear, the kinds of insects, and where they are found in their life cycle are clues that can shed light on the time of death, the length of a corpse's exposure, and whether the corpse was moved.<ref>{{cite book |last=Smith |first=Kenneth G. V. |title=A manual of forensic entomology |publisher=[[Cornell University Press]] |location=Ithaca, New York |year=1986 |pages=205 |isbn=978-0801419270 |url=https://www.researchgate.net/profile/Lavinia-Iancu-2/post/Can-anyone-have-publication-regarding-Use-of-Insects-in-Forensic-studies/attachment/59d63cb879197b8077999a89/AS%3A416701205237760%401476360717665/download/SMITH+1986.pdf |access-date=21 April 2024 }}</ref><ref>{{cite journal |last1=Kulshrestha |first1=Pankaj |last2=Satpathy |first2=Debasish K. |title=Use of beetles in forensic entomology |journal=[[Forensic Science International]] |year=2001 |volume=120 |issue=1–2 |pages=15–17 |pmid=11457603 |doi=10.1016/S0379-0738(01)00410-8 |url=https://www.academia.edu/14093844 |access-date=21 April 2024 }}</ref>
* [[Forensic anthropology]] is the medico-legal branch of [[physical anthropology]] that studies skeletons and human remains, usually to seek clues as to the identity, age, sex, height and ethnicity of their former owner.<ref>{{cite book |last1=Schmitt |first1=Aurore |last2=Cunha |first2=Eugénia |last3=Pinheiro |first3=João |title=Forensic anthropology and medicine: complementary sciences trom recovery to cause of death |url=https://fr.z-library.se/book/610382/ee3d82 |publisher=[[Humana Press]] |location=Totowa, New Jersey |year=2006 |pages=461–464 |isbn=978-1588298249 |access-date=21 April 2024 |archive-date=21 April 2024 |archive-url=https://web.archive.org/web/20240421081510/https://fr.z-library.se/book/610382/ee3d82 |url-status=dead }}</ref><ref>{{cite book |last1=Haglund |first1=William D. |last2=Sorg |first2=Marcella H. |title=Forensic taphonomy: the postmortem fate of human remains |publisher=[[CRC Press]] |location=Boca Raton, Florida |year=1996 |page=636 |isbn=978-0-8493-9434-8 |url=https://fr.z-library.se/book/2171441/24a142 |access-date=21 April 2024 |archive-date=21 April 2024 |archive-url=https://web.archive.org/web/20240421081510/https://fr.z-library.se/book/2171441/24a142 |url-status=dead }}</ref>

The [[University of Tennessee Anthropological Research Facility]] (better known as the [[Body farm|Body Farm]]) in [[Knoxville, Tennessee]], has several bodies laid out in various situations in a fenced-in plot near the medical center. Scientists at the Body Farm study how the human body decays in various circumstances to gain a better understanding of decomposition.

== Plant decomposition ==
{{See also|Composting|Anaerobic digestion|Fungal extracellular enzyme activity}}
[[Image:DecayingPeachSmall.gif|frame|right|A decaying [[peach]] over a period of six days. Each frame is approximately 12 hours apart, as the fruit shrivels and becomes covered with [[Mold (fungus)|mold]].]]
Decomposition of plant matter occurs in many stages. It begins with leaching by water; the most easily lost and soluble carbon compounds are liberated in this process.<ref>{{cite journal |last1=Adamou |first1=Ibrahima |last2=Joffre |first2=Richard |last3=Gillon |first3=Dominique |title=Changes in litter during the initial leaching phase: an experiment on the leaf litter of Mediterranean species |journal=[[Soil Biology and Biochemistry]] |year=1995 |volume=27 |issue=7 |pages=931–39 |doi=10.1016/0038-0717(95)00006-Z |bibcode=1995SBiBi..27..931I |url=https://www.academia.edu/24125303 |access-date=28 April 2024 }}</ref> Another early process is physical breakup or fragmentation of the plant material into smaller pieces, providing greater surface area for colonization and attack by [[decomposer]]s. In fallen dead parts of plants ([[plant litter]]), this process is largely carried out by [[saprophagous]] ([[detritivorous]]) soil invertebrate fauna,<ref>{{cite journal |date=2018-12-15 |title=Effects of soil macro- and mesofauna on litter decomposition and soil organic matter stabilization |url=https://fr.zlib-articles.se/book/66968066/7b0d31 |journal=Geoderma |language=en |volume=332 |pages=161–172 |doi=10.1016/j.geoderma.2017.08.039 |issn=0016-7061 |last1=Frouz |first1=Jan |bibcode=2018Geode.332..161F |s2cid=135319222 |access-date=28 April 2024 |url-access=subscription |archive-date=2024-04-28 |archive-url=https://web.archive.org/web/20240428083852/https://fr.zlib-articles.se/book/66968066/7b0d31 |url-status=dead }}</ref><ref>{{cite journal |date=2015-05-01 |title=Do soil fauna really hasten litter decomposition? A meta-analysis of enclosure studies |url=https://www.academia.edu/113403551 |journal=European Journal of Soil Biology |language=en |volume=68 |pages=18–24 |doi=10.1016/j.ejsobi.2015.03.002 |issn=1164-5563 |last1=Frouz |first1=Jan |last2=Roubíčková |first2=Alena |last3=Heděnec |first3=Petr |last4=Tajovský |first4=Karel |bibcode=2015EJSB...68...18F |access-date=28 April 2024 }}</ref> whereas in standing parts of plants, primarily [[parasitic]] life-forms such as parasitic plants (e.g. [[mistletoe]]s), insects (e.g. [[aphid]]s) and fungi (e.g. [[polypore]]s) play a major role in breaking down matter, both directly<ref>{{cite journal |last1=Mellado |first1=Ana |last2=Morilas |first2=Lourdes |last3=Gallardo |first3=Antonio |last4=Zamora |first4=Regino |title=Temporal dynamic of parasite-mediated linkages between the forest canopy and soil processes and the microbial community |journal=[[New Phytologist]] |year=2016 |volume=211 |issue=4 |pages=1382–92 |doi=10.1111/nph.13984 |doi-access=free |pmid=27105275 |bibcode=2016NewPh.211.1382M }}</ref> and indirectly via a [[Food web|multitrophic]] cascading effect.<ref>{{cite journal |last1=Yuan |first1=Yongge |last2=Lin |first2=Xinru |last3=Chen |first3=Gelv |last4=Van Kleunen |first4=Mark |last5=Li |first5=Junmin |title=Parasitic plants indirectly regulate decomposition of soil organic matter |journal=[[Functional Ecology (journal)|Functional Ecology]] |year=2023 |volume=37 |issue=2 |pages=302–14 |doi=10.1111/1365-2435.14232 |bibcode=2023FuEco..37..302Y |url=https://www.researchgate.net/publication/365581344 |access-date=5 May 2024 }}</ref>

Following this, the plant [[detritus]] (consisting of [[cellulose]], [[hemicellulose]], microbial [[metabolite]]s, and [[lignin]]) undergoes chemical alteration by microbes. Different types of compounds decompose at different rates. This is dependent on their [[chemical structure]].<ref>{{cite journal |last1=Bhatnagar |first1=Jennifer M. |last2=Peay |first2=Kabir G. |last3=Treseder |first3=Kathleen K. |title=Litter chemistry influences decomposition through activity of specific microbial functional guilds |journal=[[Ecological Monographs]] |year=2018 |volume=88 |issue=3 |pages=429–44 |doi=10.1002/ecm.1303 |bibcode=2018EcoM...88..429B |osti=1439725 |url=https://www.academia.edu/80201098 |access-date=5 May 2024 }}</ref> For instance, [[lignin]] is a component of wood, which is relatively resistant to decomposition and can in fact only be decomposed by certain [[fungi]], such as the [[White rot|white-rot]] fungi.

Wood decomposition is a complex process involving fungi which transport nutrients to the nutritionally scarce wood from outside environment.<ref>{{cite journal |last1=Filipiak |first1=Michał |last2=Sobczyk |first2=Łukasz |last3=Weiner |first3=January |date=2016-04-09 |title=Fungal transformation of tree stumps into a suitable resource for xylophagous beetles via changes in elemental ratios |journal=Insects |language=en |volume=7 |issue=2 |pages=13 |doi=10.3390/insects7020013 |pmc=4931425 |doi-access=free }}</ref> Because of this nutritional enrichment, the fauna of [[Xylophagy|saproxylic]] insects may develop and, in turn, affect dead wood, contributing to decomposition and nutrient cycling in the forest floor.<ref name=":0">{{cite journal |last1=Filipiak |first1=Michał |last2=Weiner |first2=January |date=2016-09-01 |title=Nutritional dynamics during the development of xylophagous beetles related to changes in the stoichiometry of 11 elements |url=https://www.researchgate.net/publication/308778403 |journal=Physiological Entomology |volume=42 |issue=1 |language=en |pages=73–84 |doi=10.1111/phen.12168 |issn=1365-3032 |access-date=12 May 2024 }}</ref> [[Lignin]] is one such remaining product of decomposing plants with a very complex chemical structure, causing the rate of microbial breakdown to slow. Warmth increases the speed of plant decay by roughly the same amount, regardless of the composition of the plant.<ref name="mit">{{cite web |last1=Chu |first1=Jennifer |title=The mathematics of leaf decay: a mathematical model reveals commonality within the diversity of leaf decay |url=https://news.mit.edu/2012/leaf-decay-1004 |website=[[MIT News]] |date=4 October 2012 |publisher=MIT News Office |location=Cambridge, Massachusetts |access-date=12 May 2024 }}</ref>

In most [[grassland]] ecosystems, natural damage from [[fire]], [[detritivore]]s that feed on decaying matter, [[termite]]s, [[grazing]] mammals, and the physical movement of animals through the grass are the primary agents of breakdown and [[nutrient cycling]], while bacteria and fungi play the main roles in further decomposition.<ref>{{cite journal |last1=Harris |first1=Wylie N. |last2=Moretto |first2=Alicia S. |last3=Distel |first3=Roberto A. |last4=Boutton |first4=Thomas W. |last5=Bóo |first5=Roberto M. |title=Fire and grazing in grasslands of the Argentine Caldenal: effects on plant and soil carbon and nitrogen |journal=Acta Oecologica |year=2007 |volume=32 |issue=2 |pages=207–14 |doi=10.1016/j.actao.2007.05.001 |bibcode=2007AcO....32..207H |url=https://ri.conicet.gov.ar/bitstream/handle/11336/20641/CONICET_Digital_Nro.24527.pdf |access-date=2 June 2024 |hdl=11336/20641 |hdl-access=free }}</ref>

The chemical aspects of plant decomposition always involve the release of [[carbon dioxide]]. In fact, decomposition contributes over 90 percent of carbon dioxide released each year.<ref name="mit"/>

== Food decomposition ==
{{Main|Meat spoilage}}
[[File:A punnet of rotten peaches.jpg|thumb|A punnet of rotten peaches]]
The decomposition of food, either plant or animal, called ''[[Food spoilage|spoilage]]'' in this context, is an important field of study within [[food science]]. Food decomposition can be slowed down by [[food conservation|conservation]]. The spoilage of meat occurs, if the meat is untreated, in a matter of hours or days and results in the meat becoming unappetizing, poisonous or infectious. Spoilage is caused by the practically unavoidable infection and subsequent decomposition of meat by bacteria and fungi, which are borne by the animal itself, by the people handling the meat, and by their implements. Meat can be kept edible for a much longer time—though not indefinitely—if proper hygiene is observed during production and processing, and if appropriate food safety, [[food preservation]] and food storage procedures are applied.<ref>{{cite book |year=2004 |title=Understanding and measuring the shelf-life of food |editor-last=Steele |editor-first=Robert |pages=3–23 |chapter=The major types of food spoilage: an overview |last1=Singh |first1=R. Paul |last2=Anderson |first2=B. A. |doi=10.1533/9781855739024.1.3 |isbn=9781855739024 |publisher=[[CRC Press]] |location=Boca Raton, Florida |url=https://fr.zlib-articles.se/book/49777049/180367 |access-date=19 May 2024 |archive-date=19 May 2024 |archive-url=https://web.archive.org/web/20240519084702/https://fr.zlib-articles.se/book/49777049/180367 |url-status=dead }}</ref>

Spoilage of food is attributed to contamination from [[microorganism]]s such as bacteria, molds and yeasts, along with natural decay of the food.<ref>{{cite journal |last1=Gram |first1=Lone |last2=Ravn |first2=Lars |last3=Rasch |first3=Maria |last4=Bartholin Bruhn |first4=Jesper |last5=Christensen |first5=Allan B. |last6=Givskov |first6=Michael |title=Food spoilage: interactions between food spoilage bacteria |journal=[[International Journal of Food Microbiology]] |year=2002 |volume=78 |issue=1–2 |pages=79–97 |doi=10.1016/S0168-1605(02)00233-7 |pmid=12222639 |url=http://higiene.unex.es/Bibliogr/EcolMicr/IJFM2079.pdf |access-date=26 May 2024 |archive-date=9 February 2025 |archive-url=https://web.archive.org/web/20250209053227/http://higiene.unex.es/Bibliogr/EcolMicr/IJFM2079.pdf |url-status=dead }}</ref> These decomposition bacteria reproduce at rapid rates under conditions of moisture and preferred temperatures. When the proper conditions are lacking the bacteria may form spores which lurk until suitable conditions arise to continue reproduction.<ref>{{cite journal |last1=André |first1=Stéphane |last2=Vallaeys |first2=Tatiana |last3=Planchon |first3=Stella |title=Spore-forming bacteria responsible for food spoilage |journal=Research in Microbiology |year=2017 |volume=168 |issue=4 |pages=379–87 |doi=10.1016/j.resmic.2016.10.003 |pmid=27989764 |url=https://www.academia.edu/113930808 |access-date=26 May 2024 }}</ref> Decomposition rates and speed may differ or vary due to abiotic factors such as moisture level, temperature, and soil type. They also vary depending on the initial amount of breakdown caused by the prior consumers in the [[food chain]]. This means the form that organic matter is in, original plant or animal, partially eaten, or as [[Feces|faecal]] matter when the detritivore encounters it. The more broken down the matter, the faster the final decomposition.<ref>{{cite web |title=Decomposition |url=https://eoss.asu.edu/sites/default/files/Decomposition.pdf |access-date=2 June 2024 |website=[[Arizona State University]] |location=Tempe, Arizona }}</ref>

==Rate of decomposition==

The rate of decomposition is governed by three sets of factors: the physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.<ref name="Chapin159">{{cite book |title=Principles of terrestrial ecosystem ecology |chapter=Factors controlling decomposition |chapter-url=https://archive.org/details/principlesofterr0000chap/page/158/mode/2up |last1=Chapin |first1=F. Stuart III |last2=Matson |first2=Pamela A. |last3=Mooney |first3=Harold A. |publisher=Springer |year=2002 |isbn=978-0-387-95443-1 |location=New York, New York |pages=159–69 |access-date=2 June 2024 }}</ref>

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in damp, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in [[wetland]]s), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth. When the rains return and soils become wet, the [[osmotic gradient]] between the bacterial cells and the soil water causes the cells to gain water quickly. Under these conditions, many bacterial cells burst, releasing a pulse of nutrients.<ref name="Chapin159"/> Decomposition rates also tend to be slower in acidic soils.<ref name="Chapin159"/> Soils which are rich in [[clay minerals]] tend to have lower decomposition rates, and thus, higher levels of organic matter.<ref name="Chapin159"/> The smaller particles of clay result in a larger surface area that can hold water. The higher the water content of a soil, the lower the oxygen content<ref name="Chapin61">{{cite book |title=Principles of terrestrial ecosystem ecology |chapter-url=https://archive.org/details/principlesofterr0000chap/page/60/mode/2up |chapter=Soil properties and ecosystem functioning |last1=Chapin |first1=F. Stuart III |last2=Matson |first2=Pamela A. |last3=Mooney |first3=Harold A. |publisher=Springer |year=2002 |isbn=978-0-387-95443-1 |location=New York, New York |pages=61–67 |access-date=2 June 2024 }}</ref> and, consequently, the lower the rate of decomposition. Clay minerals also bind particles of organic material to their surface, making them less accessible to microbes.<ref name="Chapin159"/> Soil disturbance like [[tillage|tilling]] increases decomposition by increasing the amount of oxygen in the soil and by exposing new organic matter to soil microbes.<ref name="Chapin159"/>

The quality and quantity of the material available to decomposers is another major factor that influences the rate of decomposition. Substances like [[sugar]]s and [[amino acid]]s decompose readily and are considered labile. [[Cellulose]] and [[hemicellulose]], which are broken down more slowly, are "moderately labile". Compounds which are more resistant to decay, like [[lignin]] or [[cutin]], are considered recalcitrant.<ref name="Chapin159"/> Litter with a higher proportion of labile compounds decomposes much more rapidly than does litter with a higher proportion of recalcitrant material. Consequently, dead animals decompose more rapidly than dead leaves, which themselves decompose more rapidly than fallen branches.<ref name="Chapin159"/> As organic material in the soil ages, its quality decreases. The more labile compounds decompose quickly, leaving an increasing proportion of recalcitrant material called [[humus]]. Microbial cell walls also contain recalcitrant materials like [[chitin]], and these also accumulate as the microbes die, further reducing the quality of older [[soil organic matter]].<ref name="Chapin159"/>

== See also ==
* [[Cadaverine]]
* [[Chemical decomposition]]
* [[Ecosystem]]
* [[Humus]]
* [[Leachate]]
* [[Microbiology of decomposition]]
* [[Peat]] (turf)
* [[Putrescine]]
* [[Staling]]

== References ==
{{Reflist}}

== External links ==
{{Wiktionary|decomposition|spoilage|perishable}}
* {{Commons category-inline|Decomposition}}
* [https://web.archive.org/web/20160307204349/http://1lecture.com/microbiology/food%20spoilage/index.html 1Lecture.com] – Food decomposition (a Flash animation)

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[[Category:Anaerobic digestion]]
[[Category:Articles containing video clips]]
[[Category:Biodegradable waste management]]
[[Category:Composting]]
[[Category:Signs of death]]
[[Category:Biostratinomy]]