Skov

Denne artikel omhandler plantesamfundet eller biotopen "en skov". For andre betydninger af Skov, se Skov (flertydig). (Se også artikler, som begynder med Skov)

En skov er et plantesamfund eller en biotop, hvori træer udgør hovedbestanddelen. Endvidere må det kræves, at der er tale om et større areal, minimum 0,5 hektar og en minimumsbredde på 20 meter med træer højere end 5 meter og at trækronerne dækker mere end 10 %.^[1] Skov forekommer naturligt overalt på Jorden, bortset fra områder med for lav temperatur eller for tørt klima. Klimaet er afgørende for, hvilken skovtype, der udvikles.

Verdens biomer, fordelt efter klimabælterne

Taiga (nåleskov) Løvskove Tempereret regnskov Mediterrane biomer Monsunskove Bjergskove Skovsavanner Subtropiske tørkeskove Tropiske regnskove

Skoven producerer bioaerosoler og påvirker skydannelse, tågedannelse og nedbøren væsentligt – og dermed både vejret og klimaet. ^[2]^[3]^[4]^[5]

En mindre skov kaldes for en lund.

I overført betydning bruges ordet "skov" også til at angive en større samling af ensartede individer eller emner f.eks. en skov af biler eller mennesker.

Økosystem

Skove forekommer hvor det ikke er for koldt og hvor der er et vist minimum af nedbør (afhængig af temperaturen). Hvis der falder for lidt regn forekommer i stedet savanne, steppe eller tundra. For stor højde eller koldt klima er varigheden af vækstsæsonen afgørende. I en given højde eller under en vis gennemsnitstemperatur findes en trægrænse, og over denne kan der ikke vokse skov - kun enkelte, ofte forkrøblede, træer.

Skove udgør komplekse økosystemer, og de kan i nogen områder være det mest produktive land-økosystem. Efter oceanerne er skovene de områder der har størst indflydelse på det globale klima. Skovene binder store mængder kuldioxyd (CO2) og producerer ilt. Skove er med til at balancere klimaet lokalt - og måske også globalt. Blandt skove finder man nogen af de mest artsrige økosystemer (tropisk regnskov) og økosystemet med størst biomasse pr. areal (tempereret regnskov).

Skove med træer, som har dybe rødder, har en væsentlig indflydelse på klimaet og den dybere jords vandindhold. Træernes rødder kan transportere op til 10% af den årlige nedbør i vådsæsonen fra overfladejorden og til dybere jordlag – ned til 13 meter. I tørketider "henter" træerne så vandet igen og kan på denne måde lave op til 40% mere fotosyntese i tørkeperioder. ^[6] ^[7] ^[8]

Skovtyper

Skovformer

Skov biomer og økoregioner i Danmark

Søsterprojekter med yderligere information:

Billeder og medier fra Wikimedia Commons
Opslagsværker fra Wikibooks

Palæarktiske zone – den Økozone som bl.a. Danmark, Tyskland og Sverige ligger i
- Biom: Tempereret løvfældende skov
  - Økoregion: Tempererede løvskove i Nordvesteuropa
- Biom: Boreal nåleskov
  - Økoregion: Skandinavisk og russisk nåleskov

Se også

Træ (organisme)
Mykorrhiza-netværk
Skovbrug
Det danske kulturlandskabs udvikling – skovens indvandring og udbredelse i Danmark

Kilder/Referencer

^ Skovstatistik 2018 (Webside ikke længere tilgængelig) Thomas Nord-Larsen, Vivian Kvist Johannsen, Torben Riis-Nielsen, Iben Margrete Thomsen og Bruno Bilde Jørgensen (2019). Institut for Geovidenskab og Naturforvaltning, Københavns Universitet, Frederiksberg. 40 s. ill. ISBN 978-87-7903-813-4 (web)
^ Penn State. (2004, May 6). Missing Chemical Important To Air Pollution Estimates. ScienceDaily Citat: "..."We think we measured all major components of the hydroxyl radical reactants, but there is something still unaccounted for,” says Brune. "We know that something we cannot identify is reacting with the hydroxyl radicals and we know it is temperature dependent and not light dependent. We just do not know what it is."..."
^ California Institute of Technology (2009, August 7). Organic Carbon Compounds Emitted By Trees Affect Air Quality. ScienceDaily Citat: "..."The king emitters are oaks," Wennberg says. "And the isoprene they emit is one of the reasons that the Smoky Mountains appear smoky."..."And isoprene only comes from plants. They make hundreds of millions of tons of this chemical...for reasons that we still do not fully understand."..."
^ Carnegie Mellon University. (2014, May 15). Emissions from forests influence very first stage of cloud formation. ScienceDaily Citat: "...This new study uncovers an indispensable ingredient to the long sought-after cloud formation recipe -- highly oxidized organic compounds..."It turns out that sulfuric acid and these oxidized organic compounds are unusually attracted to each other. This remarkably strong association may be a big part of why organics are really drawn to sulfuric acid under modern polluted conditions," Donahue said...The fine-tuned model not only predicted nucleation rates more accurately but also predicted the increases and decreases of nucleation observed in field experiments over the course of a year, especially for measurements near forests. This latter test is a strong confirmation of the fundamental role of emissions from forests in the very first stage of cloud formation, and that the new work may have succeeded in modeling that influence..."
^ 26. februar 2014, videnskab.dk: Forskningsgennembrud i aerosoler: Sådan danner træer skyer. Internationalt forskerhold med dansk deltagelse har fundet ud af, hvordan gas fra træer er med til at danne skyer og påvirke klimaet. Videnskaben har ellers kæmpet i omkring 20 år med at forstå, hvordan de såkaldte aerosoler bliver skabt. Citat: "...»Eksperimentet viste, at aerosoler dannes i store mængder henover skove og i langt større mængder, end vi forestillede os. Men det var også interessant at finde ud af, at NOx-gasser i byen gjorde, at aerosolerne ikke kunne dannes. Det var årsagen til, at vi ikke kunne få VOC’erne til at blive til aerosoler i laboratoriet, før mængden af NOx blev reduceret,« siger han..."
^ University of California – Berkeley (2006, January 13). Deep-rooted Plants Have Much Greater Impact On Climate Than Experts Thought. ScienceDaily Citat: "...The tap roots transfer rainwater from the surface to reservoirs deep underground and redistribute water...increases photosynthesis and the evaporation of water...by 40 percent in the dry season...During the wet season, these plants can store as much as 10 percent of the annual precipitation as deep as 13 meters (43 feet) underground, to be tapped during the dry months...tree roots acting like pipes to allow water to shift around much faster than it could otherwise percolate through the soil..."
^ 24 September 2007, BBC News: Amazonian forest 'more resilient' Citat: "...Although increased photosynthesis in drought conditions might appear counter-intuitive, the group said it could be explained if the trees were still able to access water reserves with deep root systems...The key thing here is that the tree roots access water deeper than is often represented in models...more frequent drought conditions would eventually diminish the deep-water stores, and make the trees suffer..."
^ University of Arizona (2007, September 26). Amazon Forest Shows Unexpected Resiliency During Drought. ScienceDaily Citat: "...By contrast, the UA-led team's findings suggest the opposite happens...During the 2005 drought, Amazon forest trees flourished in the sunnier-than-average weather, most likely by tapping water deep in the forest soil...The limit of the forest's resiliency is unknown, Saleska said, adding, "But if you take away enough water for long enough, the trees will die."..."

Litteratur

Dieter Heinrich, Manfred Hergt (1992). Munksgaards atlas – økologi. København: Munksgaard. ISBN 87-16-10775-6.

Eksterne henvisninger

Skov- og Naturstyrelsen
Skoven i skolen
Karsten Thomsen, Dansk skovnatur Arkiveret 19. oktober 2007 hos Wayback Machine og Appendikser Arkiveret 10. oktober 2007 hos Wayback Machine

[1] Skovstatistik 2018 (Webside ikke længere tilgængelig) Thomas Nord-Larsen, Vivian Kvist Johannsen, Torben Riis-Nielsen, Iben Margrete Thomsen og Bruno Bilde Jørgensen (2019). Institut for Geovidenskab og Naturforvaltning, Københavns Universitet, Frederiksberg. 40 s. ill. ISBN 978-87-7903-813-4 (web)

[2] Penn State. (2004, May 6). Missing Chemical Important To Air Pollution Estimates. ScienceDaily Citat: "..."We think we measured all major components of the hydroxyl radical reactants, but there is something still unaccounted for,” says Brune. "We know that something we cannot identify is reacting with the hydroxyl radicals and we know it is temperature dependent and not light dependent. We just do not know what it is."..."

[3] California Institute of Technology (2009, August 7). Organic Carbon Compounds Emitted By Trees Affect Air Quality. ScienceDaily Citat: "..."The king emitters are oaks," Wennberg says. "And the isoprene they emit is one of the reasons that the Smoky Mountains appear smoky."..."And isoprene only comes from plants. They make hundreds of millions of tons of this chemical...for reasons that we still do not fully understand."..."

[4] Carnegie Mellon University. (2014, May 15). Emissions from forests influence very first stage of cloud formation. ScienceDaily Citat: "...This new study uncovers an indispensable ingredient to the long sought-after cloud formation recipe -- highly oxidized organic compounds..."It turns out that sulfuric acid and these oxidized organic compounds are unusually attracted to each other. This remarkably strong association may be a big part of why organics are really drawn to sulfuric acid under modern polluted conditions," Donahue said...The fine-tuned model not only predicted nucleation rates more accurately but also predicted the increases and decreases of nucleation observed in field experiments over the course of a year, especially for measurements near forests. This latter test is a strong confirmation of the fundamental role of emissions from forests in the very first stage of cloud formation, and that the new work may have succeeded in modeling that influence..."

[5] 26. februar 2014, videnskab.dk: Forskningsgennembrud i aerosoler: Sådan danner træer skyer. Internationalt forskerhold med dansk deltagelse har fundet ud af, hvordan gas fra træer er med til at danne skyer og påvirke klimaet. Videnskaben har ellers kæmpet i omkring 20 år med at forstå, hvordan de såkaldte aerosoler bliver skabt. Citat: "...»Eksperimentet viste, at aerosoler dannes i store mængder henover skove og i langt større mængder, end vi forestillede os. Men det var også interessant at finde ud af, at NOx-gasser i byen gjorde, at aerosolerne ikke kunne dannes. Det var årsagen til, at vi ikke kunne få VOC’erne til at blive til aerosoler i laboratoriet, før mængden af NOx blev reduceret,« siger han..."

[6] University of California – Berkeley (2006, January 13). Deep-rooted Plants Have Much Greater Impact On Climate Than Experts Thought. ScienceDaily Citat: "...The tap roots transfer rainwater from the surface to reservoirs deep underground and redistribute water...increases photosynthesis and the evaporation of water...by 40 percent in the dry season...During the wet season, these plants can store as much as 10 percent of the annual precipitation as deep as 13 meters (43 feet) underground, to be tapped during the dry months...tree roots acting like pipes to allow water to shift around much faster than it could otherwise percolate through the soil..."

[7] 24 September 2007, BBC News: Amazonian forest 'more resilient' Citat: "...Although increased photosynthesis in drought conditions might appear counter-intuitive, the group said it could be explained if the trees were still able to access water reserves with deep root systems...The key thing here is that the tree roots access water deeper than is often represented in models...more frequent drought conditions would eventually diminish the deep-water stores, and make the trees suffer..."

[8] University of Arizona (2007, September 26). Amazon Forest Shows Unexpected Resiliency During Drought. ScienceDaily Citat: "...By contrast, the UA-led team's findings suggest the opposite happens...During the 2005 drought, Amazon forest trees flourished in the sunnier-than-average weather, most likely by tapping water deep in the forest soil...The limit of the forest's resiliency is unknown, Saleska said, adding, "But if you take away enough water for long enough, the trees will die."..."

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