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(Kako) iskorišćavanje u osnovi mijenja rast drveća?

(Kako) iskorišćavanje u osnovi mijenja rast drveća?


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Zainteresovan sam za dodavanje mogućnosti modeliranja proizvodnje izdanačkog stabla modelu višegodišnjih usjeva (Miguez et al 2008)…

Implementacija bazena biomase i parametri alokacije potrebni za rast drveća relativno su jednostavni.

Međutim, nije mi jasno hoće li biti potrebno uzeti u obzir bilo kakve promjene u obliku rasta i fiziologiji (npr. Alokacija, alometrija) povezane s gospodarenjem izdanacima.

Postoje li modeli koji eksplicitno modeliraju ponovni rast izdanaka? Postoje li neka posebna pitanja koja bih trebao razmotriti?


Fernando E. Miguez, Xinguang Zhu, Stephen Humphries, German A. Bollero i Stephen P. Long. GCB Bioenergy. 2009. Tom 1, izdanje 4, stranice 282 - 296 (veza)


Prema Deckmyn i sur. (2004.), primarni učinak upravljanja izdanacima je da je udio ukupne biomase u korijenju relativno veći nakon izdanaštva, te da se znatan dio ugljika u korijenu (~ 20% mase korijena) preraspodjeljuje iznad zemlje za podršku rastu izdanaka u proljeće nakon izdana.

Zbog ove velike ponovne raspodjele, izdanačke biljke mogu brže rasti (i brže doseći zatvaranje krošnje), nego sadnice (Ceulemans et al 1996), važno je uzeti u obzir da se zatvaranje krošnje (maksimalni indeks površine lista) javlja brže nakon izdanaštvo


Deckman et al, 2004. Rast i prinos topole u izdanaku sa kratkom rotacijom: simulacije modela koristeći procesni model SECRETS. Biomasa i bioenergija doi:10.1016/S0961-9534(03)00121-1

Ceulemans et al, 1996. Poređenje karakteristika eukalipta, topole i vrbe s posebnim osvrtom na pristup izdanaka, modeliranje rasta Izvorni istraživački članak Biomasa i bioenergija, svezak 11, izdanja 2-3, stranice 215-231 doi:10.1016/0961 -9534 (96) 00035-9


Tree Genetics

Genetika drveća je proučavanje gena drveća – jedinica prenosa nasljednih karakteristika unutar drveća. Svaki gen je obično segment molekula DNK ili RNK unutar kromosoma koji kontrolira proizvodnju

specifičnih aminokiselina ili proteina koji pak utječu na specifične karakteristike razvoja stabla, poput oblika i funkcije lista. Takve karakteristike se prenose s roditelja na potomstvo i stoga su osnovni kontrolori onoga što određuje jednu vrstu od druge, kao i podvrste ili ekotipove.

Vrste se obično razlikuju jedna od druge jer imaju jedinstveno različite gene i, prema tome, prepoznatljive jedinstvene oblike, veličine, funkcije i, što je najvažnije, reproduktivne karakteristike. Jedna definicija jedinstvene vrste je da se ne može pariti s drugom vrstom i proizvesti održivo potomstvo. Na drveću to može biti zato što dva različita stabla proizvode cvijeće i pelud u različito vrijeme, polen može biti različitih oblika i veličina i nije sposoban ući i oploditi cvijeće drugih vrsta, ili cvijeće može imati karakteristike koje ne dozvoljavaju polen drugih vrsta vrste da ih oplode.

U nekim slučajevima dvije blisko povezane, ali različite vrste mogu proizvesti održivo potomstvo koje ima karakteristike obje vrste. To se naziva hibrid i često je sterilno ili se ne može reproducirati. U životinja je uobičajen primjer potomstvo između konja i magarca, koje proizvodi mazgu. Na drveću su najčešći primjer ukrštanja između vrsta u porodici topola - zvanih hibridne topole. Kao što je spomenuto, hibridi često ne mogu reproducirati svoje potomstvo, a većina hibrida se ne razvija u odrasle osobe koje imaju dobre karakteristike preživljavanja. Povremeno, hibrid može imati određene osobine koje su jako poželjne, poput većih plodova, bržeg rasta u visini, listova različite boje, zbog čega ih ljudi mogu umjetno proizvesti u određene svrhe.

U prirodi, genetska varijacija koja se javlja i dovodi do različitih vrsta određena je pet glavnih procesa:

Mutacija Proces u kojem dolazi do greške kada se geni dupliciraju ili prenose na potomstvo. Velika većina mutacija je štetna i dovodi do smrti pojedinca, ali povremeno mutacija rezultira korisnim karakteristikama, poput veće tolerancije na sunce ili sušu, produženog rasta korijena, različitog oblika ili boje lišća i ranijeg cvatnje. Ako ove karakteristike pojedincu daju prednost u preživljavanju, ova mutacija ima veliku vjerovatnoću da će se održati u potomstvu te individue. Prirodna selekcija Ako mu specifični geni (poput onih iz mutacija) pojedinih organizama daju prednost preživljavanja, veća je vjerojatnost da će proizvesti više potomaka koji će zauzvrat imati veću prednost preživljavanja. To dovodi do konačne dominacije ove genetske osobine u lokalnoj populaciji. Na primjer, drveće u sušnoj klimi obično ima malo, debelo lišće kako bi im pomoglo u očuvanju vode u odnosu na drveće u vlažnijim područjima, gdje drveće s velikim, tankim listovima nema konkurentski nedostatak. Prirodna selekcija, stoga, omogućava razvoj populacija unutar vrste koje bi mogle biti bliže prilagođene lokalnim karakteristikama, kao što su vrijeme zime i proljeća, česti šumski požari, dostupnost vode i hranjivih tvari, te otpornost na štetočine i patogene. Takve geografske varijacije u vrsti nazivaju se ekotipovi ili podvrste. Ako se dovoljno izoliraju od opće populacije, mogu razviti karakteristike koje postaju dovoljno jedinstvene da ih kvalificiraju kao drugu vrstu. Migracija Ovo je općenito kretanje genetskih informacija kroz veću populaciju putem širenja peludi ili sjemena. Obično se ovo kretanje ne događa na velikim udaljenostima i stoga će se veliki prirodni krajolik prekriven drvećem iste vrste sastojati od grupa međusobno povezanih stabala zvanih porodice i susjedstva – svako sa specifičnim i jedinstveno sličnim genetskim osobinama, iako se ne razlikuje dovoljno za smatrati ekotipovima ili podvrstama. Genetski drift Unutar populacije, slučajne razlike ili varijacije u genetskom sastavu mogu se pojaviti kada mutacija stupi u interakciju s prirodnom selekcijom kako bi se stvorila jedinstvena osobina u vrsti. To se često događa u malim, izoliranim populacijama u kojima postoji mala migracija vanjskog peludi ili sjemena. Razlike između ponderosa bora Black Hills (dvije iglice po fascikli) i ponderosa bora sjeverne Stjenovite planine (tri iglice po fascikli) posljedice su genetskog zanošenja jer su njihove populacije izolirane jedna od druge stotinama kilometara suhe prerije. Hibridizacija Uzgoj između dvije različite vrste - često blisko povezane - koje rezultiraju potomstvom naziva se hibridizacija. Većina hibrida, slično kao i mutacije, ne proizvode održivo ili prikladno potomstvo i stoga ne cvjetaju. Povremeno će hibrid imati superiorne konkurentske karakteristike koje mu omogućavaju reproduktivnu prednost. Takvi hibridi na kraju mogu postati podvrsta ili vlastita vrsta.

Genetika drveća i procesi koji ih kontroliraju razlozi su zbog kojih imamo mnogo različitih vrsta drveća i od vitalnog su značaja za stvaranje biološke raznolikosti širom zemlje. Genetska adaptacija omogućava vrstama da koloniziraju zemljišta koja možda nisu podržavala život i da se prilagode učinkovitijem korištenju resursa dostupnih u bilo kojem krajoliku.

Ljudi su koristili genetsko uzgoj i, u novije vrijeme, spajanje gena (umjetno spajanje određenih gena iz jedne vrste u drugu vrstu ’ DNK) za stvaranje biljaka i životinja koje: proizvode veće količine hrane, kao što su mnoge specifične kulture povrća i žitarica rase konja, kao što su belgijski za vuču ili čistokrvni za trke i rase drveća koje rastu ravnije i više za proizvodnju drveta, kao što je bor lololi, ili koje su otpornije na egzotične unesene bolesti, kao što su bijeli borovi otporni na evropsku žuljevu rđu . Klimatske promjene mogu stvoriti uvjete u kojima se drveće koje ima specifične genetske prilagodbe u vrijeme mraza i proljeća, dostupnost vlage, štetočine i patogene itd., Više nije dobro prilagođeno novoj klimi. Iako genetski procesi mogu omogućiti svakoj vrsti da se prilagodi, ovaj proces može potrajati nekoliko stoljeća jer stabla sporo sazrijevaju i proizvode potomstvo. Što brže dođe do bilo kakvih klimatskih promjena, veće su šanse da vrsta ili ekotip izumru. Ljudska pomoć u pomaganju vrstama u migraciji i prilagođavanju može ublažiti negativne utjecaje ako dođe do brzih klimatskih promjena.

Srodno čitanje:
Harper John L. 1977. Biološka populacija biljaka. Academic Press, New York. 892 str.

Wenger Karl F. (ur.) 1984. Drugo izdanje Priručnika za šumarstvo. John Wiley i sinovi, New York. 1335 str.


Suočavanje s klimatskim nesigurnostima kroz poboljšane proizvodne tehnologije u uslovima tropskih ostrva

5.3 Upotreba mikroba

Loša klijavost i nastanak sadnica rezultat su slanosti tla, što negativno utječe na rast i razvoj usjeva i odgovorno je za nisku poljoprivrednu proizvodnju. Depresivni efekat saliniteta na klijanje mogao bi biti povezan sa padom endogenih nivoa hormona (Afzal et al., 2006). Međutim, ugradnja određenih mikroorganizama tijekom tretmana bioprimiranja sjemena u mnoge žitarice i povrtnjake rezultirala je povećanjem nivoa hormona rasta biljaka i poboljšanjem performansi sjemena (Howell, 2003).

Nekoliko je studija pokazalo da je kolonizacija korijena Trichoderma harzianum povećala razinu biljnih enzima, uključujući razne peroksidaze, hitinaze, β-1,3-glukanaze, hidroperoksidaza putem lipoksigenaze i spojeve poput fitoaleksina i fenola kako bi osigurala trajnu otpornost na stres (Harman, 2006, Hoitink i sur., 2006). Akumulacija nekih kompatibilnih otopljenih tvari također je primijećena u uvjetima stresa zbog soli i predloženo je kao dio mehanizma (a) koji kontroliraju toleranciju soli u biljkama. Prolin je jedno od najpoznatijih otopljenih tvari koje se akumuliraju zbog Trichoderma inokulacija u slanom rastvoru u brinjal, kukuruz i mahunarke. Još jedan kemijski malondealdehid, povezan sa stresom, proizvodnja raste kako se stres biljaka povećava. Ovo je pokazatelj oksidativnog stresa koji služi kao indeks peroksidacije lipida. Peroksidacijsko oštećenje plazma membrane dovodi do curenja sadržaja, brzog isušivanja i smrti stanica (Scandalios, 1993).


Način na koji uzorkujemo drveće utiče na našu procjenu uticaja klimatskih promjena na šume

Čini se kao da strašna predviđanja o opadanju šuma u SAD-u i dalje izlaze iz štampe. Čak je i nacionalni popis šuma, program USDA Forest Service Inventory and Analysis Forest Inventory and Analysis (FIA), izmjerio povišene razine smrtnosti drveća u mnogim vrstama šuma - uglavnom kao rezultat požara, suše i izbijanja insekata. Međutim, za razliku od ovih pokazatelja opadanja, program FIA -e također pokazuje značajnu regeneraciju i ponovni rast. U našem nedavnom radu (Klesse et al., 2018.) koristimo novu mrežu podataka o prstenovima drveća prikupljenih na FIA parcelama kako bismo uporedili dva predviđanja o opadanju šuma, prvo na osnovu uzorka inventara šuma, a drugo na osnovu javnog arhive u obliku drveća, Međunarodne banke podataka o drveću (ITRDB). Rezultat: način na koji uzorkujemo drveće čini veliku razliku u projektovanom opadanju šuma.

ITRDB je proizvod decenija napornog rada i svedočanstvo je kako naučnici-prstenovi na drveću otvoreno dele podatke. Studije zasnovane na ovom skupu podataka predviđaju ozbiljno propadanje šuma. Ali koliko ITRDB predstavlja regionalni rast šuma? ITRDB i FIA skupovi podataka razlikuju se u jednom ključnom aspektu: dizajnu uzorkovanja. Drveće u ITRDB -u obično je odabrano da opiše klimatske varijabilnosti iz prošlosti. Drveće u FIA -i odabrano je prema strogom protokolu koji predstavlja ukupnu šumsku populaciju, bez obzira na veličinu drveća ili vrstu. Usporedili smo ove dvije opsežne baze podataka o drveću kako bismo provjerili razlike koje bi mogle utjecati na predviđanja budućeg pada rasta.

Naši nalazi potvrđuju ono što mnoge naše kolege znaju godinama - varijabilnost rasta stabala veća je kod stabala ITRDB u odnosu na stabla FIA - zbog jačeg utjecaja klimatskih varijabilnosti na lokacijama ITRDB. Naša analiza ukazuje na tri razloga za to. Prvo, u slučaju Douglas-jele, otkrili smo da su lokacije ITRDB-a bile na niskom rubu distribucije vrsta, gdje su uvjeti uzgoja topliji i suši (slika 1a i slika 2). Drugo, ITRDB stabla su starija, u prosjeku za skoro 200 godina (Slika 1b), starija (veća) stabla su osjetljivija na klimatske varijacije. Treće, ITRDB stabla se obično biraju sa strmih ili kamenitih padina na kojima je malo vode u tlu (Slika 1c i Slika 2), s ciljem maksimiziranja varijabilnosti u širini godišnjih prstenova rasta. Uzorak ITRDB -a predstavlja mali i vrlo poseban podskup ukupne šumske populacije - onaj koji pokazuje snažniji odgovor na klimu nego uzorci FIA -e (slika 3).

Slika 1: A) Shema šumske zajednice na jugozapadu SAD-a duž planinske padine, s podacima o nadmorskoj visini za lokacije uzorkovanja Douglas-jele. Ciljani (ITRDB) uzorci Douglas-jele obično se uzimaju sa nižih i toplijih lokacija u visinskom rasponu ove vrste. B) Ciljana stabla (ITRDB) takođe imaju tendenciju da budu mnogo starija u poređenju sa stablima inventara šuma. C) Odabir drveća na strmim, stjenovitim padinama s malim kapacitetom vode u tlu dovodi do veće varijacije širine prstena u stablima ITRDB u odnosu na stabla FIA.

Slika 2: Kontrastni uslovi lokacije i stabla. Na lijevoj strani je gornja kota (2743 metra), šumska parcela kojom dominira Daglasova jela, sa plodnim uslovima uzgoja i velikom gustinom drveća. Desno je još jedno mjesto na kojem dominira Daglasska jela, ali ovo na nižoj nadmorskoj visini (2286 metara), ciljano zbog starijeg drveća i gotovo nepostojećeg tla. Uslovi na lokaciji, poput onih na desnoj granici vlažnosti dostupne za rast drveća, rezultiraju većom varijabilnošću širine prstena i snažnijim odgovorom na klimatske promjene. Dvije šume udaljene su samo 27 km. Mjesto na desnoj fotografiji smatralo bi se dobrim mjestom za uzorkovanje za odgovore na pitanja o povijesnim klimatskim varijacijama, i stoga može biti tipično za ITRDB lokacije za uzorkovanje. Nasuprot tome, mjesto na lijevoj fotografiji ne bi se smatralo poželjnim mjestom za uzorkovanje istraživačkih pitanja čiji je cilj bolje razumijevanje klimatskog sistema. Fotografije C. Guiterman.

Slika 3: Dva radijalna obrasca rasta tipičnog "ciljanog" ITRDB uzorka (gore) i uzorka FIA inventara (dole). Uzorak ITRDB-a pokazuje mnogo veću varijabilnost širine prstena iz godine u godinu u poređenju sa stabilnijim obrascem rasta „kolosijeka“ u uzorku FIA-e.

Implikacije ovih razlika postaju evidentne kada predvidimo budući rast drveća. ITRDB i FIA podaci o prstenovima drveća nedvosmisleno se slažu da rast drveća opada s povećanjem temperature. Promjena klime povećava regionalne temperature, uzrokujući stres od suše za drveće. Međutim, projekcije pada su manje ekstremne ako se temelje na skupu podataka FIA -e. Direktno poređenje između ova dva ukazuje na to da projekcije zasnovane na ITRDB precenjuju pad rasta drveća za 41 posto. Ovi nalazi ukazuju na određeni stupanj otpornosti šumskih pejzaža - neće sva stabla ići putem drveća ITRDB. Podsjećaju nas i da su nam potrebni podaci iz šireg spektra studija kako bismo u potpunosti razumjeli - i predvidjeli - učinke klimatskih promjena na šume.


Kako upravljati šumom za divlje životinje

Naše šume su nekada bile oblikovane prirodnim procesima, poput ispaše bizona i drugih velikih sisavaca. U njihovom nedostatku, potrebno je pravilno upravljanje kako bi naše šume bile raznolike i pune života. Ova stranica nudi osnovni vodič za upravljanje šumom za divlje životinje.

Zašto upravljati šumom?

Šumska staništa u Velikoj Britaniji raznovrsna su i jedinstvena, od drevnih bukovih šuma na jugu do autohtonih borovih šuma na sjeveru, gdje lutaju crvene vjeverice i divlje mačke. Od posljednjeg ledenog doba naše šume su se znatno smanjile u svom opsegu i Velika Britanija sada ima manje drveća od većine evropskih zemalja. Održavanje naših šuma punih divljih životinja važan je posao. Svatko tko posjeduje mrvicu šume može pomoći učiniti je što raznolikijom za divlje životinje.

Veliki dio divljih životinja u našim šumama sada se oslanja na aktivno upravljanje kako bi se osigurala mješavina različitih staništa, od gomila mrtvog drveta koje može pomoći bubama i gljivama do otvorenih proplanaka koji pomažu leptirima.

Zaklade za divlje životinje upravljaju stotinama šumskih rezervata prirode i to često uključuje mješavinu pristupa – nekim područjima se upravlja kopčanjem i održavanjem otvorenih područja kao što su vožnje, a neka područja su ostavljena da podivljaju. Često ovaj rad oponaša prirodne procese poput oštećenja vjetra i oluje ili ispašu velikih životinja poput bizona i slonova koji su nekad živjeli u našim šumama. Bez nekog oblika upravljanja mnoge naše šume postat će mračne, zasjenjene i dominirat će velikim zrelim drvećem bez ikakvih promjena u strukturi, starosti ili pokrivenosti. Na kraju, ovo smanjuje količinu divljih životinja koje u njima mogu živjeti pa često težimo mješavini staništa u našim šumskim rezervatima prirode.

Šume definiraju krajolik i, bilo da su drevne ili mlade, pružaju domove hiljadama vrsta biljaka, životinja i gljiva. Ljudima pružaju mjesta za istraživanje i povezivanje s prirodom te osjećaj dobrobiti. Oni apsorbiraju buku, zagađenje i ugljični dioksid, oslobađaju kisik, štite zgrade, smanjuju poplave i osiguravaju izvor održivih sredstava za život i drvne građe. Održivim upravljanjem šumama njegujemo stanište koje je sjajno i za divlje životinje i za ljude.

Odakle da počnem?

Prije nego započnete bilo kakav posao upravljanja šumom, procijenite što trenutno raste i živi na lokaciji. To će vam pomoći da utvrdite koje bi upravljanje moglo biti najbolje na vašoj web lokaciji, izbjegavajući uznemiravanje rijetkih ili zaštićenih vrsta. Nekim vrstama, poput lišajeva, paprati i mahovina, bit će potrebni vijekovi za izgradnju i na njih će vrlo brzo utjecati strojevi, promjena svjetlosnih uvjeta ili konkurencija s drugim vrstama. Drugi mogu biti pogođeni na neočekivane načine, na primjer, šišmiši mogu biti poremećeni ako se promijene uslovi okoline oko njihovog skloništa.

Ko vam može pomoći u tome?

Vjerovatno će postojati vještine i lokalno znanje unutar obližnjih grupa divljih životinja, individualnih prirodnjaka i ekologa. Također možete unaprijediti sebe i/ili svoj tim tako što ćete pohađati kurseve identifikacije koje nude Wildlife Trusts ili druge organizacije.

Koje su vrste zaštićene?

Nekim životinjama, poput lješnjakovih puhova, velikih grebenastih mladunaca i svim vrstama šišmiša, potrebna je licencirana osoba da provjerava prisutnost gnijezda, jezerca i skloništa. Ove životinje treba zaštititi od uznemiravanja i promjena staništa. Neke vrste ptica koje se razmnožavaju takođe zahtevaju dozvolu da posećuju svoja gnezda, uključujući oraole, sove ušare, jastrebove i vatru.

Traženje povijesnih informacija i podataka o staništima o vašoj šumi može dati tragove o tome kako se njome prethodno upravljalo, pomažući vam da isplanirate što ćete dalje učiniti. Vaše lokalno udruženje za zaštitu divljih životinja često može dati stručne savjete ako je potrebno.

Kako mogu osjetljivo upravljati svojom šumom?

Da biste osjetljivo upravljali šumom, želite kopirati sve različite stvari koje bi ogromna drevna šuma sama učinila prije više hiljada godina, kada su šume bile veće. Osiguravate mješavinu mrtvog drveta, zdravog živog drveća, mladih sadnica i otvorenih prostora, poput proplanaka.

Gdje početi

Jednom kad saznate koje divlje životinje imate u šumi i steknete ideju o tome kako se njima upravljalo u prošlosti, možete početi planirati šta i gdje raditi. Ako je vaša web lokacija označena, na primjer, mjestom od posebnog naučnog interesa ili drevnim poluprirodnim šumama, ili je uključena u vladinu shemu, morat ćete se pridržavati smjernica navedenih u bilo kojim sporazumima.

Copping

Od prije ranog srednjeg vijeka pa sve do kraja devetnaestog stoljeća mnogim šumama se upravljalo izdanaštvom. To uključuje povremeno sječenje drveća ili grmlja do nivoa tla, ostavljajući ih da izniknu nove stabljike iz posječenih panjeva. To dovodi do brze proizvodnje malog okruglog drva koje se koristilo za drške od metle, ogrjev, ograde za ograde i prepreke. Bliskavica može podmladiti drvo i omogućiti mu da traje mnogo godina, što znači da može osigurati daljnje usjeve drveta ili drva. Također potiče rast šumskog cvijeća, poput zvončića, jaglaca i ljubičica, dopuštajući svjetlost podovima šume.

Izdvajanje je najprikladnije za drevne šume, koje su se uzgajale u prošlosti. Nemaju sve šume prošlost izdanaštva. Trebalo bi samo razmisliti o ponovnom uvođenju režima sječe u šumska područja koja su bila zahvaćena u posljednjih 60-ak godina. Ako vaši susjedni zemljoposjednici već zatrpavaju velika područja svojih šuma, možda će biti manje potrebe za izdanaštvom na vašem zemljištu.

Bakljenje uključuje rezanje svake stabljike do panja što je moguće bliže zemlji, pod uglom. To se ponavlja svakih 5–20 godina, ovisno o vrsti, a može se raditi rotacijom u obliku šahovske ploče, kako bi se osigurali minimalni poremećaji. Najbolje je to učiniti u kasnu jesen/zimu (od novembra do februara) prije pucanja pupoljaka i gniježđenja ptica.

Površina izdanaka trebala bi biti manja između 0,25 i 1 hektara, a izdanak neće dobro rasti jer će biti zasjenjen.

  • Vrste poput hrasta i bukve vrlo sporo rastu, pa se stoga ostavljaju stajati kao drvena stabla.
  • Vrlo male šume nisu prikladne za izdanak. Možda bi bilo bolje stvoriti plitku, izdanačku 'kapicu' uz rub šume, po mogućnosti istočno -zapadno.
  • Obnovljeni rast vrlo je privlačan jelenima i zečevima, a opetovano pregledavanje može ubiti stolicu. U ovim okolnostima razmislite o ograđivanju.

Ljestvica omogućuje rast cvjetnica i trava, dajući hranu insektima koji sa svoje strane hrane drugim životinjama, poput ptica i šišmiša. Životinjski svijet koji ima koristi od izdanaštva uključuje cvijeće poput drvenih anemona, ljubičica pasa, gospine trave, zvončića, leptira i moljaca, bumbara, vilinih konjica, sporih crva, ptica kao što su slavuji i ljute, neke vrste šišmiša, poput školjki, puha i drugih mali sisari.

Jednogodišnju raskošnu šumu, Cloud Wood (Leicestershire and Rutland Wildlife Trust)

Upravljanje otvorenim područjima kao što su vožnje, proplanci i kapice

U vašim šumama stari putevi i otvoreni prostori možda su zarasli i jednostavno ih je potrebno otvoriti za vožnju, proplanak ili pokrovač. Na taj način stvarate staništa na rubovima šuma, gdje se mješavina sunčeve svjetlosti, izloženosti i malo skloništa kombinuje kako bi se stvorio visok nivo raznolikosti vrsta. Treba jahati proplanke i kapice kako se ne bi vratili u gušće šume. Koriste mnoge vrste, posebno rijetke i šumske leptire u opadanju, kao što su mali biserno obrubljeni fritilar i bijeli admiral.

Vožnja

Vožnja je linearna staza kao što je staza, dizajnirana za pristup, na primjer, javna šetnica. Gdje je moguće, upravljajte vožnjama tako da trče od istoka prema zapadu jer će dobiti najviše sunca što će pomoći cvjetnicama, insektima i gmazovima. Međutim, obratite pažnju na smjer vjetra, jer ne želite stvoriti vjetrobran koji bi na kraju mogao oštetiti drveće. Odrežite središnji dio staze svake godine krajem ljeta za uredan finiš, a zatim se duže travnate površine mogu kositi u dvogodišnjem ili trogodišnjem ciklusu. Ne zaboravite ukloniti sve reznice trave kako biste izbjegli neprirodno povećanje nivoa hranjivih tvari u šumskim tlima.

Glades

Na primjer, ravnice su otvori unutar šume, nedavno iscrpljenog područja. Omogućuju bujanje poljskog cvijeća i vrsta insekata usred šume zbog izloženosti sunčevoj svjetlosti i toplini. Međutim, proplanci su još bolji kada su obrubljeni velikim drvećem kako bi im pružili zaklon. Ne zaboravite ukloniti sve pokose trave prilikom gospodarenja, ali se grančice itd. Mogu nakupiti kako bi se životinjama osigurao zaklon.

Za velike šume, vožnje mogu biti široke do 20-30 m, a proplanak može biti otprilike upola manji od fudbalskog terena

Kapice

Jakobova kapica je polukružna ili D-oblika duž ivice staze ili staze koja je očišćena od drveća, omogućavajući šikaru, začinsko bilje i travu da rastu, stvarajući raznoliku ivicu šume. Dobro funkcioniraju u malim šumama, širokim vožnjama ili velikim proplancima gdje je manje prikladno iscrpiti minimalnu površinu. Da biste imali koristi od sunca, kapicu je najbolje postaviti na sjevernu stranu vožnje istok-zapad i na stranu šume okrenutu prema jugu.

Mrtvo drvo

Sve dok ne postoji opasnost da drvo padne na nekoga, ostavljanje mrtvog ili umirućeg stabla može zaista koristiti divljim životinjama vaše šume. Mrtvo drvo osigurat će hranu za stotine vrsta životinja, gljivica, lišajeva i mahovine. Također će pružiti domove šišmišima, djetlićima i mnogim beskičmenjacima, poput buba.

Ako smatrate da vam nedostaje mrtvog drveta, razmislite o neželjenom drveću koje laje prstenom. Kada mrtvo drvo padne, oduprite se da ga razbijete. Cijelo drvo će biti bolje za divlje životinje od onih koje su posječene.

Grmlje i drvo sa krčenja i šišanja treba ostaviti u gomilama, ili pretvoriti u mrtve živice (gomile grana i granja raspoređene tako da formiraju barijeru).

Mrtvo drvo je sjajno za sve vrste divljih životinja. Gljive omekšavaju drvo truljenjem, a larve buba počinju da ga žvaću. Oni zauzvrat daju hranu za djetliće, koji prave rupe u gnijezdu u trulom drvetu. U međuvremenu, rupe koje nastaju na mjestima gde su trule stare slomljene grane pružaju pukotine za slijetanje šišmiša i ptica.

Stanjivanje

Novozasađene šume ili one koje ne pokazuju znakove zarasle mogu zahtijevati malo stalnog upravljanja osim povremenog prorjeđivanja drveća. To uključuje uklanjanje siromašnih, slabih, bolesnih ili pretrpanih stabala kako bi preostala stabla postala jača i čvršća. Prorjeđivanje se također može koristiti za upravljanje zapuštenim šumama gdje je gusto zasjenjenje smanjilo rast šumskog poljskog cvijeća i grmlja.

Saznati više

Dakle, posjedujete šumu? Upoznajte svoje drvo i čuvajte ga. Odlična (besplatna) knjižica na 37 stranica daje široki uvod u većinu aspekata gospodarenja šumama.

Woodlands: Praktični priručnik i druge priručnike koji se mogu kupiti na web stranici conservationhandbooks.com

Clarke, S.A., Green, D.G., Bourn, N.A. i Hoare, D.J. 2011. Upravljanje šumom za leptire i moljce. Butterfly Conservation, Wareham, Dorset.

Harmer, R. i Howe, J. 2003. Uzgoj šuma i upravljanje izdanačkim šumama. Komisija za šumarstvo, Bristol.

Starr, C. 2013. Upravljanje šumom: Praktični vodič (drugo izdanje). Crowood Press, Marlborough, Wiltshire.

Symes, N. i Currie, F. 2005. Upravljanje šumama za ptice: Vodič za upravljanje pticama u opadanju u Engleskoj. RSPB Management Guides, Sandy, Bedfordshire.


Šta ubija najveće drveće u tropskim šumama?

Ostaje misterija kako i zašto drveće umire. Iako znamo šta može ubiti drveće, borimo se da identifikujemo šta zapravo ubija drveće u prirodi. Prevazilaženje ovog nedostatka znanja sada je hitno pitanje jer se čini da se stope mortaliteta drveća povećavaju. [Autori: E.M. Gora i A. Esquivel-Muelbert]

Saradnici

Autor

Evan Gora

Naučni saradnik Earl S. Tupper, Smithsonian Tropical Research Institute Cary Institute of Ecosystem Studies

Autor doprinosa

Adriane Esquivel Muelbert

Predavač globalne ekologije šuma, Univerzitet u Birminghamu

Dijeli

Kopirajte link

Drveće ublažava klimatske promjene tako što apsorbira ugljik iz atmosfere i skladišti ga kao drvo. Smrt drveća početak je procesa koji otključava ovaj drveni ugljik i prenosi ga nazad u atmosferu. Kako se smrtnost drveća povećava, to ograničava sposobnost šuma da apsorbiraju i skladište ugljik. Stoga je smrt drveća bitan dio zagonetke u tekućim naporima da se shvati globalni ciklus ugljika, kako sada tako i u budućnosti. Da bismo pomogli u rješavanju ovog jaza u znanju, pregledali smo obrasce smrtnosti stabala zavisne od veličine i pružili okvir hipoteze za razumijevanje i istraživanje ovih obrazaca u našem nedavnom radu - Implikacije smrtnosti drveća ovisne o veličini za dinamiku ugljika u tropskim šumama.

Tropske šume su važna komponenta ove jednadžbe. Tropske šume sadrže 60% ugljika kopnene biomase, iako sadrže samo

10% ukupne površine zemljišta. Netaknute vlažne tropske šume - to jest, šume koje ljudi ne krče ili degradiraju - najviše doprinose ovom potonuću ugljika. Međutim, čak su i ove netaknute šume u opasnosti. Masivna mreža šumskih parcela otkrila je da se mortalitet drveća također povećava u netaknutim tropskim šumama.

U šumi, nisu sva stabla podjednako važna za budžet ugljika. Za razliku od većine životinja, drveće nastavlja rasti tijekom svog života, stvarajući ogromne razlike u veličini unutar jedne zajednice drveća. Kao rezultat toga, najveći 1% drveća u šumi obično sadrži ca. 50% nadzemne biomase te šumskog ugljika. U skladu s tim, posljedice smrti za najveće drveće nesrazmjerno su važne za gubitke ugljika u šumi. Međutim, ova velika stabla su rijetka i o njima znamo vrlo malo. Još manje znamo šta ih ubija.

Naši su se putevi ukrstili jer smo oboje radili na smrtnosti drveća. Konkretno, istraživali smo smrt drveća širom tropskih krajeva gledajući uzorke velikih razmjera i utjecaj groma na smrt drveća. Iz ovog rada oboje smo bili upoznati s borbom za izvođenje zaključaka o pokretačima smrti najvećih stabala, prvenstveno zbog njihove rijetkosti i stohastičke prirode odumiranja stabala. Međutim, još nismo shvatili dubinu ili opseg ovog problema. Ovo se promijenilo kada smo se upoznali tokom organizovane usmene sesije (vrsta simpozijuma) na konferenciji Ekološkog društva Amerike 2019. Cilj ove sesije je bio da istakne veliki napredak i izazove u našem razumijevanju smrti velikih tropskih stabala. Prezentacije na ovoj sesiji otkrile su da su izazovi nadmašili napredak. Ova sesija i naši razgovori tokom konferencije pomogli su nam da shvatimo koliko malo zaista znamo o pokretačima smrti velikog drveta.

Tokom tog sastanka odlučili smo da moramo detaljnije razmotriti uzroke smrti ovih tropskih divova. Počevši od januara 2020. počeli smo redovito razgovarati dok smo sistematski pregledavali literaturu koja se odnosi na obrasce mortaliteta drveća ovisno o veličini. Fokusirali smo se na fizičke i fiziološke mehanizme smrtnosti ovisne o veličini svakog vozača, a zatim smo procijenili njihovu empirijsku podršku. Sintetizirajući postojeće podatke, polako smo sastavili teoretski okvir o tome kako bi pokretači smrti tropskog drveća trebali varirati ovisno o veličini stabla. Ovaj okvir i našu sintezu literature predstavili smo više kolega radi komentara prije nego što smo ga dostavili Prirodne biljke .

Based on the literature, our framework predicts that abiotic factors play a bigger role in tree death as tree size increases. However, the more we read about the topic the more it became clear that there is a lot of work to be done. Whilst our field is now starting to understand the role of droughts across the vast diversity of tropical trees, we know virtually nothing about the role biotic drivers, such as pathogens or herbivores, in the death of large tropical trees. Our goal now is to take this collaboration to the field and start testing the predictions from our framework to understand how the giants of tropical forests die.

This line of inquiry is a testament to the intellectual and professional benefits of keeping an open mind and attending symposia. We began this work with distinct perspectives and approaches to studying tropical tree mortality. Working together and combining our perspectives made this project possible and facilitated our intellectual development. We encourage other early career researchers to reach outside of their existing collaborative networks where they also may have positive experiences.

Evan Gora

Earl S. Tupper Fellow Research Fellow, Smithsonian Tropical Research Institute Cary Institute of Ecosystem Studies


1.1 Themes and Concepts of Biology

Biology is the science that studies life. What exactly is life? This may sound like a silly question with an obvious answer, but it is not easy to define life. For example, a branch of biology called virology studies viruses, which exhibit some of the characteristics of living entities but lack others. It turns out that although viruses can attack living organisms, cause diseases, and even reproduce, they do not meet the criteria that biologists use to define life.

From its earliest beginnings, biology has wrestled with four questions: What are the shared properties that make something “alive”? How do those various living things function? When faced with the remarkable diversity of life, how do we organize the different kinds of organisms so that we can better understand them? And, finally—what biologists ultimately seek to understand—how did this diversity arise and how is it continuing? As new organisms are discovered every day, biologists continue to seek answers to these and other questions.

Svojstva života

All groups of living organisms share several key characteristics or functions: order, sensitivity or response to stimuli, reproduction, adaptation, growth and development, regulation/homeostasis, and energy processing. When viewed together, these eight characteristics serve to define life.

Red

Organisms are highly organized structures that consist of one or more cells. Even very simple, single-celled organisms are remarkably complex. Inside each cell, atoms make up molecules. These in turn make up cell components or organelles. Multicellular organisms, which may consist of millions of individual cells, have an advantage over single-celled organisms in that their cells can be specialized to perform specific functions, and even sacrificed in certain situations for the good of the organism as a whole. How these specialized cells come together to form organs such as the heart, lung, or skin in organisms like the toad shown in Figure 1.2 will be discussed later.

Sensitivity or Response to Stimuli

Organisms respond to diverse stimuli. For example, plants can bend toward a source of light or respond to touch (Figure 1.3). Even tiny bacteria can move toward or away from chemicals (a process called chemotaxis) or light (phototaxis). Movement toward a stimulus is considered a positive response, while movement away from a stimulus is considered a negative response.

Koncepti na djelu

Watch this video to see how the sensitive plant responds to a touch stimulus.

Reprodukcija

Single-celled organisms reproduce by first duplicating their DNA, which is the genetic material, and then dividing it equally as the cell prepares to divide to form two new cells. Many multicellular organisms (those made up of more than one cell) produce specialized reproductive cells that will form new individuals. When reproduction occurs, DNA containing genes is passed along to an organism’s offspring. These genes are the reason that the offspring will belong to the same species and will have characteristics similar to the parent, such as fur color and blood type.

Adaptacija

All living organisms exhibit a “fit” to their environment. Biologists refer to this fit as adaptation and it is a consequence of evolution by natural selection, which operates in every lineage of reproducing organisms. Examples of adaptations are diverse and unique, from heat-resistant Archaea that live in boiling hot springs to the tongue length of a nectar-feeding moth that matches the size of the flower from which it feeds. Adaptations enhance the reproductive potential of the individual exhibiting them, including their ability to survive to reproduce. Adaptations are not constant. As an environment changes, natural selection causes the characteristics of the individuals in a population to track those changes.

Growth and Development

Organisms grow and develop according to specific instructions coded for by their genes. These genes provide instructions that will direct cellular growth and development, ensuring that a species’ young (Figure 1.4) will grow up to exhibit many of the same characteristics as its parents.

Regulation/Homeostasis

Even the smallest organisms are complex and require multiple regulatory mechanisms to coordinate internal functions, such as the transport of nutrients, response to stimuli, and coping with environmental stresses. For example, organ systems such as the digestive or circulatory systems perform specific functions like carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body.

To function properly, cells require appropriate conditions such as proper temperature, pH, and concentrations of diverse chemicals. These conditions may, however, change from one moment to the next. Organisms are able to maintain internal conditions within a narrow range almost constantly, despite environmental changes, through a process called homeostasis or “steady state”—the ability of an organism to maintain constant internal conditions. For example, many organisms regulate their body temperature in a process known as thermoregulation. Organisms that live in cold climates, such as the polar bear (Figure 1.5), have body structures that help them withstand low temperatures and conserve body heat. In hot climates, organisms have methods (such as perspiration in humans or panting in dogs) that help them to shed excess body heat.

Energy Processing

All organisms (such as the California condor shown in Figure 1.6) use a source of energy for their metabolic activities. Some organisms capture energy from the Sun and convert it into chemical energy in food others use chemical energy from molecules they take in.

Evolucija

The diversity of life on Earth is a result of mutations, or random changes in hereditary material over time. These mutations allow the possibility for organisms to adapt to a changing environment. An organism that evolves characteristics fit for the environment will have greater reproductive success, subject to the forces of natural selection.

Levels of Organization of Living Things

Living things are highly organized and structured, following a hierarchy on a scale from small to large. The atom is the smallest and most fundamental unit of matter that retains the properties of an element. It consists of a nucleus surrounded by electrons. Atoms form molecules. A molecule is a chemical structure consisting of at least two atoms held together by a chemical bond. Many molecules that are biologically important are macromolecules , large molecules that are typically formed by combining smaller units called monomers. An example of a macromolecule is deoxyribonucleic acid (DNA) (Figure 1.7), which contains the instructions for the functioning of the organism that contains it.

Koncepti na djelu

To see an animation of this DNA molecule, click here.

Some cells contain aggregates of macromolecules surrounded by membranes these are called organelles . Organelles are small structures that exist within cells and perform specialized functions. All living things are made of cells the cell itself is the smallest fundamental unit of structure and function in living organisms. (This requirement is why viruses are not considered living: they are not made of cells. To make new viruses, they have to invade and hijack a living cell only then can they obtain the materials they need to reproduce.) Some organisms consist of a single cell and others are multicellular. Cells are classified as prokaryotic or eukaryotic. Prokaryotes are single-celled organisms that lack organelles surrounded by a membrane and do not have nuclei surrounded by nuclear membranes in contrast, the cells of eukaryotes do have membrane-bound organelles and nuclei.

In most multicellular organisms, cells combine to make tissues , which are groups of similar cells carrying out the same function. Organs are collections of tissues grouped together based on a common function. Organs are present not only in animals but also in plants. An organ system is a higher level of organization that consists of functionally related organs. For example vertebrate animals have many organ systems, such as the circulatory system that transports blood throughout the body and to and from the lungs it includes organs such as the heart and blood vessels. Organisms are individual living entities. For example, each tree in a forest is an organism. Single-celled prokaryotes and single-celled eukaryotes are also considered organisms and are typically referred to as microorganisms.

Visual Connection

Which of the following statements is false?

  1. Tissues exist within organs which exist within organ systems.
  2. Communities exist within populations which exist within ecosystems.
  3. Organelles exist within cells which exist within tissues.
  4. Communities exist within ecosystems which exist in the biosphere.

All the individuals of a species living within a specific area are collectively called a population . For example, a forest may include many white pine trees. All of these pine trees represent the population of white pine trees in this forest. Different populations may live in the same specific area. For example, the forest with the pine trees includes populations of flowering plants and also insects and microbial populations. A community is the set of populations inhabiting a particular area. For instance, all of the trees, flowers, insects, and other populations in a forest form the forest’s community. The forest itself is an ecosystem. An ecosystem consists of all the living things in a particular area together with the abiotic, or non-living, parts of that environment such as nitrogen in the soil or rainwater. At the highest level of organization (Figure 1.8), the biosphere is the collection of all ecosystems, and it represents the zones of life on Earth. It includes land, water, and portions of the atmosphere.

The Diversity of Life

The science of biology is very broad in scope because there is a tremendous diversity of life on Earth. The source of this diversity is evolution , the process of gradual change during which new species arise from older species. Evolutionary biologists study the evolution of living things in everything from the microscopic world to ecosystems.

In the 18th century, a scientist named Carl Linnaeus first proposed organizing the known species of organisms into a hierarchical taxonomy. In this system, species that are most similar to each other are put together within a grouping known as a genus. Furthermore, similar genera (the plural of genus) are put together within a family. This grouping continues until all organisms are collected together into groups at the highest level. The current taxonomic system now has eight levels in its hierarchy, from lowest to highest, they are: species, genus, family, order, class, phylum, kingdom, domain. Thus species are grouped within genera, genera are grouped within families, families are grouped within orders, and so on (Figure 1.9).

The highest level, domain, is a relatively new addition to the system since the 1970s. Scientists now recognize three domains of life, the Eukarya, the Archaea, and the Bacteria. The domain Eukarya contains organisms that have cells with nuclei. It includes the kingdoms of fungi, plants, animals, and several kingdoms of protists. The Archaea, are single-celled organisms without nuclei and include many extremophiles that live in harsh environments like hot springs. The Bacteria are another quite different group of single-celled organisms without nuclei (Figure 1.10). Both the Archaea and the Bacteria are prokaryotes, an informal name for cells without nuclei. The recognition in the 1970s that certain “bacteria,” now known as the Archaea, were as different genetically and biochemically from other bacterial cells as they were from eukaryotes, motivated the recommendation to divide life into three domains. This dramatic change in our knowledge of the tree of life demonstrates that classifications are not permanent and will change when new information becomes available.

In addition to the hierarchical taxonomic system, Linnaeus was the first to name organisms using two unique names, now called the binomial naming system. Before Linnaeus, the use of common names to refer to organisms caused confusion because there were regional differences in these common names. Binomial names consist of the genus name (which is capitalized) and the species name (all lower-case). Both names are set in italics when they are printed. Every species is given a unique binomial which is recognized the world over, so that a scientist in any location can know which organism is being referred to. For example, the North American blue jay is known uniquely as Cyanocitta cristata. Our own species is Homo sapiens.

Evolution Connection

Carl Woese and the Phylogenetic Tree

The evolutionary relationships of various life forms on Earth can be summarized in a phylogenetic tree. A phylogenetic tree is a diagram showing the evolutionary relationships among biological species based on similarities and differences in genetic or physical traits or both. A phylogenetic tree is composed of branch points, or nodes, and branches. The internal nodes represent ancestors and are points in evolution when, based on scientific evidence, an ancestor is thought to have diverged to form two new species. The length of each branch can be considered as estimates of relative time.

In the past, biologists grouped living organisms into five kingdoms: animals, plants, fungi, protists, and bacteria. The pioneering work of American microbiologist Carl Woese in the early 1970s has shown, however, that life on Earth has evolved along three lineages, now called domains—Bacteria, Archaea, and Eukarya. Woese proposed the domain as a new taxonomic level and Archaea as a new domain, to reflect the new phylogenetic tree (Figure 1.11). Many organisms belonging to the Archaea domain live under extreme conditions and are called extremophiles. To construct his tree, Woese used genetic relationships rather than similarities based on morphology (shape). Various genes were used in phylogenetic studies. Woese’s tree was constructed from comparative sequencing of the genes that are universally distributed, found in some slightly altered form in every organism, conserved (meaning that these genes have remained only slightly changed throughout evolution), and of an appropriate length.

Branches of Biological Study

The scope of biology is broad and therefore contains many branches and sub disciplines. Biologists may pursue one of those sub disciplines and work in a more focused field. For instance, molecular biology studies biological processes at the molecular level, including interactions among molecules such as DNA, RNA, and proteins, as well as the way they are regulated. Microbiology is the study of the structure and function of microorganisms. It is quite a broad branch itself, and depending on the subject of study, there are also microbial physiologists, ecologists, and geneticists, among others.

Another field of biological study, neurobiology, studies the biology of the nervous system, and although it is considered a branch of biology, it is also recognized as an interdisciplinary field of study known as neuroscience. Because of its interdisciplinary nature, this sub discipline studies different functions of the nervous system using molecular, cellular, developmental, medical, and computational approaches.

Paleontology, another branch of biology, uses fossils to study life’s history (Figure 1.12). Zoology and botany are the study of animals and plants, respectively. Biologists can also specialize as biotechnologists, ecologists, or physiologists, to name just a few areas. Biotechnologists apply the knowledge of biology to create useful products. Ecologists study the interactions of organisms in their environments. Physiologists study the workings of cells, tissues and organs. This is just a small sample of the many fields that biologists can pursue. From our own bodies to the world we live in, discoveries in biology can affect us in very direct and important ways. We depend on these discoveries for our health, our food sources, and the benefits provided by our ecosystem. Because of this, knowledge of biology can benefit us in making decisions in our day-to-day lives.

The development of technology in the twentieth century that continues today, particularly the technology to describe and manipulate the genetic material, DNA, has transformed biology. This transformation will allow biologists to continue to understand the history of life in greater detail, how the human body works, our human origins, and how humans can survive as a species on this planet despite the stresses caused by our increasing numbers. Biologists continue to decipher huge mysteries about life suggesting that we have only begun to understand life on the planet, its history, and our relationship to it. For this and other reasons, the knowledge of biology gained through this textbook and other printed and electronic media should be a benefit in whichever field you enter.

Career Connection

Forensic Scientist

Forensic science is the application of science to answer questions related to the law. Biologists as well as chemists and biochemists can be forensic scientists. Forensic scientists provide scientific evidence for use in courts, and their job involves examining trace material associated with crimes. Interest in forensic science has increased in the last few years, possibly because of popular television shows that feature forensic scientists on the job. Also, the development of molecular techniques and the establishment of DNA databases have updated the types of work that forensic scientists can do. Their job activities are primarily related to crimes against people such as murder, rape, and assault. Their work involves analyzing samples such as hair, blood, and other body fluids and also processing DNA (Figure 1.13) found in many different environments and materials. Forensic scientists also analyze other biological evidence left at crime scenes, such as insect parts or pollen grains. Students who want to pursue careers in forensic science will most likely be required to take chemistry and biology courses as well as some intensive math courses.


Uvod

Resprouting provides resilience to fire and allows plants to persist in pyrogenic ecosystems. When aboveground stems are killed by fire (i.e., topkilled), species that are able to resprout generate new biomass from plant parts that survive fire [1], [2] such as basal buds, lignotubers, rhizomes, or the root collar [3], [4]. Resprouting ability and resprout biomass [5]–[7] are influenced by the size of the belowground bud bank [8], the pool of belowground resources (e.g., carbohydrates and nutrients [9]–[14]), and pre-fire plant size [15], [16].

In frequently burned ecosystems, resprouting species are subjected to repeated cycles of topkill and resprouting [17], so persistence depends on the ability of plants to recover their pre-fire size to maintain a balance between biomass loss and recovery [13], [18]. Resprout height and diameter are positively correlated with pre-fire stem height and diameter [16], [19], [20], with the relationship between pre- and post-fire size fitting a curvilinear scaling function [18]. This “resprout curve” illustrates the balance between biomass loss and recovery and determines the equilibrium size (i.e., where pre-fire and post-fire size are equal) upon which plants will converge over multiple fire cycles ([18] Figure 1A ). Although resprout size is correlated with pre-fire size [16], [19], [20], large plants often recover their pre-fire size more slowly than small plants [18], [21]. This “recovery curve” is a negative curvilinear relationship between pre-fire size and the ratio of post- to pre-fire size ( Figure 1B ).

(A) Differences in resprout curves that could arise from inclusion of all stems of multi-stemmed trees. Stars indicate the equilibrium size that develops over multiple fire cycles that corresponds to the point at which biomass loss is equal to biomass recovery (i.e., intersects with the 1𢍡 line following [18]). (B) Recovery curves that correspond with resprout curves. (C) Illustration of the transformation of resprout curves to a logarithmic scale. (D) Illustration of the transformation of recovery curves to a logarithmic scale. We assessed shifts in resprout and recovery curves by testing for differences in the slopes and y-intercepts of the log10-transformed relationships between maximum and total size and size recovery.

Studies on the relationship between pre- and post-fire size and the size dependency of post-fire recovery, however, often focus only on the largest pre-fire stem and largest resprout [16], [18], [19] even though many resprouting species are multi-stemmed before and/or after fire (e.g., [22]–[24]). In fact, the number of resprouts is correlated with the number of stems pre-fire [20], [25], [26]. Allocation of biomass to multiple stems, rather than one stem, may be beneficial due to limitations on maximum stem height and growth rates [27]–[29] and the improvement in competitive success conferred by a large crown volume [30]. If the curvilinear nature of resprout and recovery curves is a consequence of limitations on maximum stem growth rates [28], [31], then this limitation could be overcome by producing multiple stems.

Accounting for all stems of multi-stemmed resprouting species, therefore, may cause an upward shift in resprout ( Figure 1A ) and recovery ( Figure 1B ) curves. An upward shift in the resprout curve would indicate that individual plants are able to maintain a greater biomass (i.e., a greater equilibrium plant size) with frequent burning. Consequently, larger individuals would be able to recover their pre-fire size. In this case, production of multiple stems could increase the ability of plants to escape a suppressed state of repeated topkill and resprouting [17], [32], [33] during a longer fire free interval. Alternatively, accounting for all stems could lead to a change from a curvilinear to linear relationship between pre- and post-fire size and size recovery, indicating that curvilinearity is not a fundamental property of resprouting. Regardless, understanding the impact of multiple stems on resprout and recovery curves is important because the ability of individual plants to recover biomass lost during fire allows for persistence with repeated burning [13].

We assessed resprouting success and the size dependency of volume and biomass recovery after complete loss of aboveground biomass. Specifically, we coppiced aboveground stems – as has been done in other studies to simulate fire-induced topkill [6], [14], [34], [35] – of six tree species that occur in the pyrogenic longleaf pine savannas and adjacent stream-head pocosins of the southeastern United States [36], [37]. To test the hypothesis that accounting for all stems of multi-stemmed resprouting species causes a shift in resprout and recovery curves, we measured all stems pre-coppicing and all resprouts. We assessed possible shifts in resprout and recovery curves by testing for differences in the slopes and y-intercepts of the log-transformed relationships between pre-coppicing and resprout size (i.e., volume and biomass) of the largest stem (maximum size) and all stems (total size Figures 1C and 1D ).


Evolucija

Zašto human beings look a bit like monkey or apes ? Why are dolphins good swimmers? Why do giraffes have long necks ? The answer to all these questions is evolution. Evolution is the way life changes through time.

All living things are povezan together like grane in a tree. Plants and animals are povezane to one another through their ancestors. For example, we dijeliti a common ancestor with gorillas, dogs or even gljive.

Evolution shows us how and why all living things change over a certain period of time.

Evidence of Evolution

We cannot watch changes in life directly. Oni zauzmi mjesto over thousands or millions of years. kako god, naučnici cannot find proof that these changes have taken place. Bitan dokazi for evolution comes from fossils, the leftovers of ancient život. When animals or plants die they are pressed into sand or glina. Over millions of years rocks are formed.

Naučnici have found out that different fossils are found in rocks of different ages. For example, the oldest rocks of our earth are about 3.8 billion years old. Oni sadrže no fossils because there was probably no life at that time. Fossils of bacteria pojaviti in rocks that are about 3.5 billion years old. Fish , reptile i mammal fossils appear in younger rocks. Human fossils are found only in the youngest and highest rock slojeve.

Fossils also show that siguran groups of animals have evoluirao from other groups. Amphibians evolved from fish that could breathe air and move on land. They had legs but also vage i a fin.

Birds probably evoluirao from dinosaurs. The archaeopteryx was an animal that had feathers like a bird and could fly. It also had teeth, claws on its wings and a skelet that looked like a meat-eating dinosaur.

But even without fossils there is other proof which shows that evolution has taken place. Drugačije vrste often have similar features which they probably got from a common ancestor. For example the front udovi of lizards, birds, bats and humans are very much alike. They have one bone in the upper arm, two in the podlaktica, Ručni zglob bones and five fingers.

Living creatures might also have strukture that they have naslijeđeno od an ancestor but have become useless. They don't need them any more. Pythons, for example, have the ostaci of back leg bones, but snakes do not have such legs. The dodatak was used by animals that ate only plants but in our bodies these organs have become useless.

The way in which different species occur all over the world also gives us dokazi for evolution. Similar species, for example, are found together in siguran oblasti. All types of kangaroos are found in Australia. This is because the kangaroos' ancestors also lived there.

Plants and animals do not always live in ideal places. Tropical ocean islands, for example, are ideal places for frogs to live, but no frogs are found there. This is because the frogs' ancestors lived on the mainland and could not get to ocean islands far away.

How evolution happens

Natural selection

Although we are all human beings, each one of us is different. We all belong to the same vrste but there are never two people on earth who are exactly the same. We are like our parents because we inherit certain features od njih.

Because there is not always enough food for animals and plants to eat they takmičiti se against each other in order to preživjeti. Neki individuals are better than others because they have certain advantages. Uključeno prosek , those that are better or stronger will preživjeti. The prednosti that they have are then prošlo dalje to their children and as time goes on these karakteristike will be prošlo dalje to the whole species. We call this natural selection.

Primjer : In 1977 no rain fell on the Galapagos Islands. Food became very scarce and many of the island's finches umro. They normally ate small sjemenke that were lying on the ground. Biologists observed to finches with larger beaks were able to preživjeti because they could eat larger and harder sjemenke to finches with smaller beaks couldn't open. In the fight for food large-beaked birds had a great prednost. Nakon suša ended biologists found out that the next generations of finches were larger than the ones before.

Genetics and Inheritance

danas, naučnici know that a molecule called DNA has all the information which controls the way life will razvijati. This information is pohranjeni u geni i struktura of geni is called the genetic code.

When a male and female have children the male spermatozoida and the female egg join together to a samac cell with two genetic codes, one set from the mother and one set from the father. A baby then develops from this cell. This is how we get certain features from our parents.

Sometimes parts of the genetic code change by accident. We call this mutacija. Some mutations in geni are dangerous , others may be an prednost. In the example of the birds, the larger beaks were a mutacija that was good for the whole species.

Adaptacija

Sometimes animals and plants fit beautifully into the world around them. The Arctic fox, for example, is adapted to the polar ice in the far north. It has a thick krzno that helps it stay warm and the white colour makes it harder for enemies to see . With its hairy feet it can walk more easily in the snow.

Giraffes also got used to the world they live in. Drevni giraffes normally did not have long necks, but those that did were able to find more food because they could doseg the leaves of the trees . Longer-necked giraffes had more babies than others and kao rezultat oni razvijen into the tallest land animals in the world.

Adaptations can uzrok plants or animals to look alike even if they are not closely povezane. The bodies of sharks and dolphins are slično, but the shark is a fish and the dolphin a mammal.

Speciation

Speciation happens when one species divides itself into two or more new vrste. This happens, for example, when the same group of animals or plants live in different places. Ponekad species migrate to new habitats. In other cases a stanovništva may be divided by natural disasters kao floods or volcanic eruptions.

Kada vrste su odvojeno they don't have contact with each other any more and they razvijati in separate ways. As time goes on the two groups become more and more different, simply because they live in different habitats maybe with more or less food or a hotter or cooler climate. If they get together again they cannot have babies any more because they are completely different.

Speed of evolution

How fast does evolution happen ? Sometimes it javlja vrlo brzo. In only a few decades insekti evoluirao that were able to survive insecticides. Viruses also razvijati brzo. The AIDS virus was unknown before the 1980s.

Some animals evolve very slowly for millions of years and then change occurs vrlo brzo.

Human Evolution

Fossils show that many vrste which are now extinct belong to the same family as we humans do&mdash Homo Sapiens. The oldest members of this family are primati that lived in Africa a few million years ago. They were able to walk upright and had a mozak that was a bit bigger than that of an ape.

Charles Darwin

Charles Darwin was an English scientist who studied nature. In his famous book "On the Porijeklo of Species " he claimed that all living plants and animals razvijen from earlier forms of life.

Darwin was born in England in 1809 . His father was a doctor and his mother died when he was 8 years old. Iako Darwin was interested in nature, he was sent to a university to study medicine, but he didn't do well there.

In 1831 Charles Darwin was pozvan to ploviti on the HMS Beagle to study natural history. The voyage lasted for five years and took Darwin to the Galapagos Islands and other places on the western coast of South America. There he studied fossils in old rocks and noticed that there was a veza between them and plant and animal life. As time went on he razvijen his theory of prirodna selekcija. Those plants and animals that fit better into their okruženje can preživjeti better and produce more offspring.

When his book was objavljeno to izazvano a lot of discussion but in a short time it was prihvaćeno by naučnici oko svijeta.


Dendrochronology: What Tree Rings Tell Us About Past and Present

Dendrochronology is the study of data from tree ring growth. Due to the sweeping and diverse applications of this data, specialists can come from many academic disciplines. There are no degrees in dendrochronology because though it is useful across the board, the method itself is fairly limited. Most people who enter into studying tree rings typically come from one of several disciplines:

  • Archaeology - for the purpose of dating materials and artefacts made from wood. When used in conjunction with other methods, tree rings can be used to plot events.
  • Chemists - Tree rings are the method by which radiocarbon dates are calibrated.
  • Climate Science - particularly in the field of palaeoclimatology where we can learn about the environmental conditions of the past, locally or globally, based on what the tree rings are telling us. By extension, this can also teach us about climate change in the future
  • Dendrology - which also includes forestry management and conservation. Dendrologists are tree scientists and examine all aspects of trees (1). Tree rings can tell them about the present local climate

Though dendrochronology also has uses for art historians, medieval studies graduates, classicists, ancient and historians due to the necessity to date some of the materials that the fields will be handling in their research projects. Typically, a bachelor's degree in any of the above disciplines are enough to study the data that comes out of dendrochronology.


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