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Min bladwisselende bome in ou woud

Min bladwisselende bome in ou woud



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Daar is 'n ou woud naby my wat vir ten minste 150 jaar en moontlik langer onaangeraak gelê het. Die woud is op 'n groot heuwel wat deur 'n moeras omring word.

Die oorgrote meerderheid van die bome in die woud is reusagtige hemlocks met aspe 'n ver sekonde. Die aspe word slegs in die laerliggende gebiede aangetref.

Ek is verbaas hoekom daar so min bladwisselende bome in die woud is. Bladwisselende bome is die algemeenste in die dorp, en hemlocks is relatief skaars buite die woud. Die enigste bladwisselende bome in die woud is esdoorns, en die paar esdoorns wat daar is is geneig om siek te lyk.

Hoekom sal daar so min bladwisselende bome wees? Maak die hemlocks hulle op een of ander manier dood, of sou dit as gevolg van die grond wees?


Gematigde Bladwisselende Woud

'n Gematigde bladwisselende woud is 'n bioom wat baie bladwisselende bome het wat hul blare in die herfs laat val. Hierdie woude staan ​​ook bekend as breëblaarwoude omdat die bome breë, plat blare het. Gematigde bladwisselende woude lê in die middelbreedtegraadgebiede van die Aarde, tussen die Arktiese pole en die trope. Hierdie biome word aan warm en koue lugmassas blootgestel, wat veroorsaak dat hulle vier seisoene het: winter, lente, somer en herfs. Soos die winter naderkom en daglig afneem, vertraag die produksie van chlorofil in die blare en stop dit uiteindelik, wat die helderrooi, geel en oranje kleure openbaar wat ons met herfs assosieer. Gematigde woude het ongeveer 65,5 miljoen jaar gelede in die Senosoïese Era begin vorm toe die Aarde begin afkoel het. Tropiese en subtropiese woude is die ander soorte bladwisselende woude.


Hoekom so min boomspesies in Quebec?

Die totale beboste oppervlakte op aarde is 4,06 miljard hektaar. 90 miljoen van daardie hektaar, waarvan 92% in die openbare besit is, is in 'n provinsie van Kanada genaamd Quebec. Dit’s 'n groot gebied van bome, twee keer die totale oppervlakte wat’s binne Swede’s grense. 1 uit elke 45 hektaar van die wêreld se woude is in Quebec, en tog van die

100 000 spesies bome op ons planeet, net sowat 50, of 1 uit 2000 is inheems aan Quebec. Hoekom is daar so min diversiteit van bome in hierdie provinsie?

Volgens 'n onlangse ontleding is klimaat die belangrikste faktor in die bepaling van boomdiversiteit, en die hoogste aantal boomspesies kan in die warm, vogtige trope gevind word. Hoekom? Moontlikhede sluit in 'n 365-dae groeiseisoen wat genoeg tyd gee om gene te reproduseer en te herkombineer, hoër mutasietempo's van UV en meer geïsoleerde nisse is my raaiskote. Op breedtegrade tussen 45 N en en 63N is daar niks veraf tropies aan Quebec nie. Sy laer breedtegrade akkommodeer gematigde woude, maar noord daarvan is 'n groot gebied met selfs langer en kouer winters. Hierdie noordelike breedtegrade het die grootste deel van Quebec’s boslande: die boreale woud. Dit is 'n plat gebied waar gene don’t kry maklik geïsoleer die groeiseisoene is kort en spesiasie van bome ly. Oorheers 'n groot woud is slegs vyf hoof spesies. Watter een kry die rand hang deels af of die grond water behou of nie: witspar word hoofsaaklik op goed gedreineerde hoogland-swartspar in die klam laaglande aangetref. Daar is ook balsemspar, jack pine en die Amerikaanse lariks.

Die grootste deel van Quebec’ se woude is van die boreale variëteit, soos die geval is regdeur die hoefystervormige, 2,5 tot 4,2 miljard jaar oue Kanadese Skild. (Vanaf https://www.the-forest-time.com/en/guides-des-pays-et-regions)

Maar hoekom bevat sy gematigde woude net sowat 40 inheemse bladwisselende spesies? Die gebied wat tans gematig is, was tydens ystydperke heeltemal bedek deur ysplate. Gedurende periodes van gletsering kan bome oorleef, maar slegs in valleie. Hulle word van mekaar geïsoleer, wat genetiese drywing tussen bome van verskillende valleie verminder, wat die vorming van verskillende spesies vergemaklik. Maar in Quebec is die paar berge wat in die suide bestaan ​​te geërodeer en te laag in hoogte om voortgaande ys af te sluit en die valleie te skuil.

Aangesien ons geneig is om meestal geheg te wees aan die bome waarmee ons grootgeword het, en aangesien in Quebec’ se geval die gebrek aan boom-biodiversiteit heeltemal natuurlik is, word ek getroos deur die feit dat al sy inheemse spesies aan my bekend is .

Die genera wat die meeste Quebec-inheemse spesies het, is Acer(esdoorn) met 6 Populus (populier) met 5 Betula (berk) met 4 en Quercus(eik) met 4. Maar onder die agt genera wat net een eensame verteenwoordiger in Quebec het , Rhus tyfina, die staghorn sumac is een van my gunstelinge. Elders in die wêreld is daar 200 verskillende spesies Rhus! Die staghorn plant beide seksueel en ongeslagtelik voort deur onderskeidelik sade en risome te versprei. Laasgenoemde skep klone, met ouer lote in die middel en jongeres rondom die moederplant. Dit’s hoekom sumacs so maklik versprei onder die skoongemaakte gebied onder hidro torings waar hulle dikwels saam met wilde druiwe bestaan. Dit is eers in onlangse jare dat ek besef het dat beide wilde druiwe en sumac vrugte eetbaar is, hoewel dit die beste is om dit te gebruik om 'n versoete drankie (rooi sumac bessies) en konfyt (wilde druiwe) te maak. Sumac behoort aan die Anacardiaceae familie, wat interessante warmklimaatbome insluit soos die mango ('n Suid-Asiatiese boorling), kasjoeneute (van Brasiliaanse oorsprong) en pistache, oorspronklik van Iran.


'n Stap in die Park

“Is daar iets wat my kan steek?” het ons kleindogter Eva gevra terwyl sy na die meer se bodem loer.

Ek en sy het in Lake Jean by Ricketts Glen State Park geswem. Dit was 'n warm dag vroeg in Junie, en dit was tienjarige Eva’s eerste ervaring van meer-swem.

Soos haar ma Luz geniet sy dit om te swem, maar sy het eers amper beangs in die water geloop. Omdat sy gewoond was daaraan om in die warm water van die Baai-eilande in Honduras te swem, waar sy die vorige jaar gaan snorkel het, of in swembaddens in Mississippi, waar sy woon, het ek aangeneem dat die koue water haar pla.

Ek het haar verseker dat geen skadelike wesens in die water skuil of in die sand wegkruip nie, en sy het ontspan. Ek het my gewone rug- en syhoue in my 45 jaar oue, tweedelige baaikostuum uitgevoer, terwyl sy die Australiese kruip- en rugslag in haar nuwer, stylvoller, tweedelige baaikostuum uitgevoer het. Die laaste keer wat ek gaan swem het, was saam met haar ma, Luz, by Whipple Dam State Park, toe Eva 'n baba was. Waar was die dekade heen?

Ek en my man, Bruce, was gretig om Eva voor te stel aan ons gunsteling plek in die hele Pennsylvania–Ricketts Glen State Park en spesifiek die Falls Hike, waarna ons nog altyd verwys het as die Glen Hike. Ons het dit al byna 'n halwe eeu gestap, deur hofmakery, huwelik, kinders en nou kleinkinders. Maar ons het nog nooit in die Jean-meer geswem of enige van die ander roetes gevat nie.

Hierdie keer het ons besluit om 'n hut te huur en 'n paar dae by die park deur te bring. Na ons swem het ons na die parkkantoor gegaan om die sleutels vir ons kajuit te gaan haal. Maar Bruce se aanlyn bespreking het nie deurgegaan nie. Ons het geen hut gehad nie, en nadat ons deur 'n reeks al hoe droewiger hutte in privaat besit daar naby getoer het, het ons na die motelle van Wilkes-Barre gegaan. Moeg van soek en teleurstelling, het ons 'n kamer betrek in die eerste een wat ons gesien het.

Stel jou voor ons, gelaai met 'n groot koeler van bederfbare produkte, verskeie kartondose met kos, rugsakke en tasse, wat ons op 'n bagasiedraer gelaai het wat deur die Hilton Garden Hotel verskaf is, en na ons kamer geneem het. Bruce was nie van plan om ons beplande Falls-staptog op te offer nie, en ek was nie van plan om ons bederfbare goed op te offer nie. Ons het hulle versigtig in die klein, motel-yskas in ons kamer gepak.

“Kampeer in 'n Hilton,” het ons geskerts terwyl ek ons ​​gebakte boontjie-aandete in 'n mikrogolfoond verhit het, wat ook bedagsaam deur die Hilton voorsien is. Tog was dit 'n groot slag om nie in 'n staatsparkhut te bly nie, waarna Eva uitgesien het omdat sy nog nooit in 'n kajuit gebly het nie. Maar sy het gouer saamgetrek as ek.

Ek was die volgende oggend nog somber toe ek ontbyt voorberei het. Ek het 'n sak ontdooide wilde bloubessies uitgehaal, met die doel om dit op ons koue graankos te sit, maar die sak het gelek. Bosbessiesap het op my nuwe jeans en die mat gedrup. Ek het 'n eed geskreeu en na die badkamer gejaag en die sak in die wasbak gedreineer. Terwyl Bruce probeer het om my jeans skoon te skrop, het Eva die mat aangepak. Uiteindelik het ons ontbyt, die bloubessies bo-op ons graankos, die vlekke min of meer weg van my jeans en die mat.

Dit was nie 'n gunstige begin nie. Maar ten spyte van die warm, vogtige weer, het ons dag verbeter toe ons die onderste parkeerterrein by die park bereik het. Eers het ons afgeklim na Adams Falls. Baie mense dink dat valle, 'n reeks van drie watervalle, 18, 25 en 10 voet hoog, wat deur diep, smal klowe jaag, die mooiste valle in die park. Ons het 'n reeks groot plonspoele gevolg wat gevorm is deur die erosie van onstuimige water, waarvan die indrukwekkendste Leavenworth-swembad is, wat ongeveer 30 voet in deursnee en agt tot tien voet diep is. Eva was genoeg beïndruk deur die wilde toneel.

Toe vertel ons haar van die waterval wat onder Pennsylvania-hoofweg 118 versteek is, wat ons nie kon sien nie. Sy was so ongelowig soos ons nog altyd was by wat gelyk het na amper heiligskennis–bou van 'n snelweg oor 'n waterval. Ons het gewonder of die snelwegingenieurs gedink het dat 22 genoemde watervalle genoeg is.

Ons het daardie weeksdag die plek amper vir onsself gehad. En diegene wat ons op die roete verbygesteek het, het nie die hele staptog geneem nie en dit van bo of onder af kortgesluit. Hulle was verbaas dat ons dit gedoen het. Hulle het ongetwyfeld ag geslaan op die waarskuwing in die parkbrosjure dat dit 'n moeilike staptog is en stappers in 'n goeie fisiese toestand moet wees. Maar ons wou hê Eva moes die roete ervaar soos ons vir byna 'n halwe eeu gehad het. Ek het altyd half grappenderwys gesê dat wanneer ek nie meer die Glen Hike kon stap nie, ek oud sou wees.

Die lang wandeling deur wat vroeër 'n ongeskonde oubos was, na die kronkelende Kitchen Creek, is die enigste gelyke deel van die hele stap. Ten spyte van die ondergang van die groot hemlocks, óf deur 'n orkaan ontwortel óf sterf aan wollerige adelgidse, het die veldblomme 'n fantastiese vertoning gebring–heel beddings van esdoorn-blaar waterblaar, jack-in-die-kansel, Kanada mayflowers, en wit-gedraaide stingel het geblom. Ek het selfs 'n paar verbleikte geverfde trilliums gevind. Maar die reuse was weg, en ons kon hulle nie met ons kleindogter deel nie.

Sodra die roete vernou en op Noordberg begin het, kon ons die water deel wat steeds van die mosbedekte rotse langs die roete drup, die wilde tuine van veldblomme, boompies en beide gewone en rots-polipodievarings wat bo-op die reuse rotse groei wat oorhang. die water, en die Louisiana-waterdore en winterkoninkies wat bo die gedruis van die water gesing het.

Die beste van alles is dat ons die watervalle kon deel. As gevolg van die uithouvermoë van rock, het hulle ook’nt verander nie. Net hul omgewing het verminder. Onlangs het die park die uitstekende reeks rotstrappe wat werknemers van Kolonel Ricketts in die negentiende eeu vir forelvissers gebou het, herstel en herbou. Ons het selfs die befaamde beekforel in 'n paar poele gesien.

Ek dink nie dat Eva my eintlik geglo het toe ek vir haar gesê het dat ons 22 genoemde watervalle op die staptog sou sien nie, maar nadat ons nog drie watervalle voor Watersmeet verby is en Ganoga Glen begin het, was sy meer as oortuig daarvan, veral toe ek begin het naamlose watervalle ook uit te wys.

“In Mississippi, sou hulle genoem word,” het sy ons vertel. Hulle het nie baie watervalle in daardie staat nie en hulle koester elke waterval.

Nadat ons nog sewe watervalle verbygesteek het, almal vernoem na Iroquois Indiese stamme, het ons die Ganoga-waterval bereik. Ganoga beteken “Water op die berg” en, op 94 voet, is dit die hoogste waterval in die park en die tweede hoogste waterval in Pennsylvania. Maar groot of klein, elke waterval het sy unieke argitektuur, hier 'n lang, smal een, daar 'n korter, breë een–almal gebeeldhouwd deur water oor rots. Dikwels het ons naby 'n val gestaan ​​en die fyn sproei verwelkom soos die dag opwarm.

Op die top van die berg het ons die Highland-roete geneem wat Ganoga Glen met Glen Leigh verbind. Maar die groot Amerikaanse beukbome, wat eens prominent deur swartbere gekenmerk is, is ook weg, dood van beukbassiekte. In hul plek is spinneige, jong beukebome wat nooit die omtrek van hul ouerbome sal bereik nie.

Weereens het die rotse gebly, 'n mengelmoes van groot gletserrotse, waarvan sommige gletserskrape toon, halfpad langs die roete. By een plek het ons deur 'n vyf-voet-wye gaping tussen twee rotse gestap genaamd “Midway Crevasse.” Na die gedruis van die water is die stilte langs hierdie roete net verbreek deur die gesing van swartkeelgroen sangers en Amerikaanse rooibokke. En toe begin ons Glen Leigh af. Hoewel dit net agt watervalle het, twee minder as Ganoga Glen, is dit steiler en het dit nog altyd vir my wilder gelyk. Nadat ons 'n skilderagtige middagete-plek gevind het wat uitkyk oor die 30 voet hoë Shawnee-waterval, het ons vir Eva die geskiedenis van die park vertel, insluitend die twee valleie bekend as die Glens Natural Area, wat 'n nasionale natuurlike landmerk is.

Ricketts Glen State Park was oorspronklik deel van 'n 80,000-akker landgoed wat besit word deur kolonel Robert Bruce Ricketts, wat Battery F gelei het tydens Pickett’s Charge by die Slag van Gettysburg. In die 1920's het die Ricketts-familie meer as die helfte van die eiendom aan die Pennsylvania Game Commission verkoop, en vandag voeg die aangrensende SGL#57 en die nabygeleë SGL#13 aansienlik meer wilde oppervlakte by die 13 050 parkakker in Luzerne, Sullivan en Columbia graafskappe, oppervlakte. wat ons gehoop het om te verken as ons in 'n kajuit gebly het.

Die grootste deel van die park, insluitend die watervalgebied, is in die 1930's as 'n nasionale parkterrein goedgekeur, maar die Tweede Wêreldoorlog het ingegryp, en die gebied is in plaas daarvan aan die Statebond van Pennsylvania deur Ricketts’-erfgename verkoop vir 'n staatspark. Lake Jean en die nou droë Lake Rose, waar ons eens saam met ons seuns piekniek gehou het, is vernoem na Ricketts’ dogters. Daardie watervalle wat nie inheemse Amerikaanse name gegee is nie, soos Mohican, Cayuga, Delaware, Seneca en Huron, is vernoem na Ricketts en sy familie. Ons het die 40 voet hoë R.B. Ricketts-waterval vir Eva uitgewys terwyl ons verder met Glen Leigh afgegaan het.

In daardie vroeë dae, het die plaaslike mense dit genoem “Kitchen Crick,” volgens Bruce. As 'n jong seun het hy eenkeer na Ricketts Glen gegaan saam met sy oom Gilbert en groot oom Byron en onthou hoe hulle deur die ou groei gestap het en die bome uitgeken het. Eva hou daarvan om familiestories te hoor, so ons het haar ook vertel van haar oupa se mense wat van Connecticut af gekom het om hulle aan die voet van North Mountain en plaas te gaan vestig, van sy oupa Ide se appelplaas en hoe Bruce en sy gesin elke jaar , wat in New Jersey gewoon het, het teruggegaan om familie by die ou plaas te besoek.

Toe ons Watersmeet bereik het, het donderdreuns ons terugstap verhaas. Eva en Bruce het maklik al 7,2 myl van die Falls-roete gestap, maar ek het gesukkel tydens die laaste afdraande van die laaste waterval, sweet het van my afgegooi. Ek het nog nooit die kliptrappe getel wat van waterval na waterval lei nie, maar ek vermoed hulle tel in die honderde. En die hoogtedaling is 1 000 voet in 'n bietjie meer as twee myl.

Terwyl Eva en Bruce voortgestap het, het ek die vlak herhaling deur die oorblyfsels van die oubos verwelkom en stadig gestap, want, soos gewoonlik, was ek mal daaroor om die vrede van die roete te verlaat. Die reën het opgehou totdat ons terug in ons motor was en huis toe gegaan het. Die natuur het ons darem nie in die steek gelaat nie al het die parkbesprekingstelsel dit gehad.
__________

Alle foto's geneem by Rickett’s Glen deur Dave Bonta op 14 Mei 2007. Om die volledige fotostel te sien, klik hier.

Deel dit:


Die Sweedse ervaring: krimpende woude & # 8211 Uitbreidende boomplantasies

Beland Lindahl, K., Sténs, A., Sandström, C., Johansson, J., Lidskog, R., Ranius, T. & Roberge, J.-M. (2015). Die Sweedse bosboumodel: Meer van alles? Bosbeleid en ekonomie http://dx.doi.org/10.1016/j.forpol.2015.10.012

Lees meer oor die boreale woud en die klimaat hier: http://klimatetochskogen.nu/en/

Verklaring deur die Direkteur-generaal, Sweedse Bosagentskap – kortfilm vervaardig deur Björn Olin: https://vimeo.com/164577187

'n Groot duidelike sny in die noorde van Swede – kortfilm vervaardig deur Björn Olin: https://vimeo.com/184095633

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[3] Larsson, A. (2011). Tillståndet i skogen – rödlistade arter in ett nordiskt perspektief. Verslag 9. Sweedse spesieinligtingsentrum SLU, Uppsala: http://www.artdatabanken.se/media/2258/tillstaandet-i-skogen.pdf

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[24] Bright, R. M., Zhao, K., Jackson, R. B. & Cherubini, F. (2015). Kwantifisering van oppervlakalbedo en ander direkte biogeofisiese klimaatsdwingings van bosbouaktiwiteite. Global Change Biology 21(9). DOI: 10.1111/gcb.12951 https://www.researchgate.net/publication/275413978_Quantifying_surface_albedo_and_other_direct_biogeophysical_climate_climate_climate_forcings_of_forestry_activities

[25] Mackey, B., Prentice, I. C., Steffen, W., House, J. I., Lindenmayer, D., Keith, H. & Berry, S. (2013). Ontwikkel die verwarring rondom grondkoolstofwetenskap en beleid om klimaatsverandering te versag. Natuur Klimaatsverandering, 3, 552–557 http://www.fern.org/sites/fern.org/files/fern-comment/Untangling%20the%20confusion%20around%20land%20carbon%20science%20and%20climate%20change%20mitigation% 20beleid.pdf

[26] Luyssaert, S., Detlef Schulze, E., Börner, A., Knohl, A., Hessenmöller, D., Law, B. E., Ciais, P. & Grace, J. (2008). Ou-groei woude as globale koolstof sink. Nature 455: 213-215 http://www.nature.com/nature/journal/v455/n7210/abs/nature07276.html

[28] Noss, R., Beier, P., Nowak, K. & Tabor, G. (2012). Sterker denke vir bewaring. Bewaringsbiologie, Vol. 26, nr. 1.DOI: 10.1111/j.1523-1739.2011.01738.x

[29] Wilson, E. O. (2016). Half-Aarde - Ons planeet se stryd om die lewe. Liveright Publishing Corporation, New York (259 pp)..


Groot Engelse Bome

Die 2000 jaar oue lemmetjie

Een van Engeland se oudste bome staan ​​nederig tussen al die wonderlike eksemplare van die Nasionale Arboretum by Westonbirt: 'n kleinblaarkalk wat tot 2 000 jaar oud kan wees. Die boom is verlede November tot by sy stompe afgekap, toe is die kunstenaar Richard Harris opdrag gekry om 'n beeldhouwerk ter ere daarvan te skep, met honderde van sy gesnyde stingels.

Engeland se oudste eikeboom is nie in 'n woud nie, maar op 'n grasveld, naby die dorp Bourne in die suide van Lincolnshire. Dit word vermoedelik meer as 1 000 jaar oud en het 'n hol stam van ongeveer 12 meter, waarvan die binnekant eens gebruik is as 'n teekamer met ingeboude deur en dak. Dit is gelys deur Guinness World Records, en kan by Bowthorpe besoek word Park Plaas.

Savernake Forest in Wiltshire is 'n klein en kosbare aandenking van die wilde bosveld wat eens 'n groot deel van Suid-Engeland bedek het. In die hartjie van Savernake staan ​​die Big Belly Oak, 'n reus van die sessie-eike variëteit, met 'n omtrek van meer as 11 meter. Daar word geglo dat die boom wortel geskiet het in die dae van Willem die Veroweraar, ongeveer 1 000 jaar gelede. Jy kan dit sien langs die A346, suid van die gehuggie Cadley.

In die middel van die New Forest, aan die begin van Bolderwood Ornamental Drive, is Knightwood Oak, die woud se grootste en ook een van sy oudstes. In die 1990's is sy omtrek op 7,4 meter aangeteken en groei - ten spyte daarvan dat sy hout oor honderde jare geoes is met behulp van die antieke stelsel van polardering. Kom meer te wete oor die boom uit hierdie poduitsending.

Die 80-hektaar Shining Cliff antieke bosveld, aan die westelike oewer van die rivier Derwent in Derbyshire, was eens deel van die koninklike jagwoud van Duffield Frith. Dit bevat die oorblyfsels van Betty Kenny, 'n gekneusde en gehawende taxus wat na bewering die kinderrympie "Rock a Bye Baby" geïnspireer het. 'n Sirkelvormige gemerkte roete gaan verby die boom en 'n ryk verskeidenheid ander plantlewe, gevoed deur fonteine ​​wat deur die grond opsypel.

'n Antieke reus van Wiltshire se Savernake-woud, die King of Limbs is 'n stuifhout-eik – 'n tradisionele tegniek om hout te oes terwyl nuwe groei aangemoedig word. Gedink om ongeveer 1 000 jaar oud te wees en eenkeer beskryf as "'n reuse seekat het uit die diepte uitgebars", het hierdie eikeboom 'n legio nuwe aanhangers gekry toe die groep Radiohead 'n album daarna vernoem het.

Salcey Forest, net sewe myl van Northampton af, is die oorblyfsels van 'n Middeleeuse koninklike jagbos. Sowel as die ruïnes van geboue uit die ystertydperk, is hierdie kosbare 500 hektaar woud die tuiste van die "druïde" – 'n reeks eikebome van tot 600 jaar oud. Een van die bekendstes is die Milking Oak, onder wie se verkoelende skadu Salcey se beeste eens gemelk is.

Die 120-hektaar Bedgebury National Pinetum, 'n wêreldbekende versameling konifere naby Tunbridge Wells, spog met die hoogste boom in Kent onder sy 12 000 bome en struike. Hierdie groot spar, bekend as "die Ou Man van Kent", is in 1840 geplant deur burggraaf Beresford, wat die Bedgebury-landgoed besit het en 'n veldmaarskalk in Wellington se weermag was. Die boom staan ​​'n magtige 51 meter hoog.


Min bladwisselende bome in ou woud - Biologie

Ås, S. 1999. Indringing van matriksspesies in klein habitatkolle. Bewaringsekologie [aanlyn] 3(1): 1. Beskikbaar vanaf die internet. URL: http://www.consecol.org/vol3/iss1/art1/
'n Weergawe van hierdie artikel waarin teks, figure, tabelle en bylaes afsonderlike lêers is, kan gevind word deur hierdie skakel te volg.
Navorsing

Indringing van matriksspesies in klein habitatkolle

Stefan & Arings
Departement Diere-ekologie, Evolusionêre Biologie Sentrum, Uppsala Universiteit, Swede


Die diversiteit, uitgedruk as spesierykheid in gelyke-grootte monsters, van houtlewende kewers in opeenvolgende stadiums van bladwisselende woud na bosbrande ongeveer 100 jaar gelede, het nie tussen kolgroottes in hierdie studie verskil nie. Die deurslaggewende vraag vir bewaring is dus of die gebrek aan vermindering in diversiteit in klein kolle beteken dat 'n aantal klein kolle die streeksdiversiteit net so doeltreffend kan verhoog as wat een groter gebied kan. In die huidige studie het die kleiner kolle nie verskil van groter kolle in substraat beskikbaarheid, kwaliteit of heterogeniteit nie. Die frekwensie van 'n groep spesies is gemeet as die aantal voorkomste, nl. die aantal bome waarop 'n spesie gevind is, opgesom oor alle spesies in die groep. Die aantal voorkomste van spesies uniek aan die spesifieke kolgrootte groep het nie tussen groot en klein kolle verskil nie. Die aantal voorkomste van spesies wat matriksgebiede verkies het (bestuurde naaldbos en oopkap) was egter groter as wat verwag is in klein kolle. Die resultate dui daarop dat klein kolle, hoewel hulle hoë plaaslike (alfa) diversiteit, is meer soortgelyk in spesiesamestelling aan naburige matriksgebiede (verminder beta diversiteit). Klein gebiede dra dus minder by tot die streeks- (gamma) diversiteit as groter gebiede.

SLEUTELWOORDE: alfa (plaaslike) diversiteit, beta (tussen-habitatte) diversiteit, bladwisselende woud, versteuring, diversiteit, brand, gamma (streeks) diversiteit, indringing, matrikshabitat, kolgrootte, spesierykheid.

Gepubliseer op 10 Februarie 1999.

Diversiteit is 'n sleutelelement in bewaring, beide ter wille daarvan en as 'n benadering van 'n gebied se biologiese belangrikheid wanneer presiese kennis van die spesiesamestelling, of die huidige bedreigingstatus van die betrokke spesie, ontbreek (Wilson en Willis 1975). In baie gevalle is die gebruik daarvan as 'n benadering waarskynlik 'n regverdigbare strategie, maar hou 'n risiko in om gespesialiseerde spesies te verloor wat beperk is tot spesie-arm gebiede.

Diversiteit is 'n komplekse term wat soms sinoniem met spesierykheid gebruik word. Diversiteit sluit egter ook egaligheid van die verspreiding van individue op spesies in. Soos met die meeste ekologiese terme, het spesiediversiteit skaalafhanklike eienskappe. 'n Nuttige klassifikasie van hierdie eienskappe is die onderverdeling van diversiteit in drie kategorieë (alfa, beta, en gamma diversiteit), soos voorgestel deur Whittaker (1972). In hierdie skema, alfa diversiteit is die plaaslike diversiteit binne 'n habitat, beta diversiteit is 'n funksie van die verskil tussen habitatte, en gamma diversiteit is die diversiteit oor 'n geografiese reeks wat 'n aantal verskillende habitatkolle insluit, nl. streeksdiversiteit. Cody (1975) definieer egter gamma diversiteit as 'n funksie van die verandering in spesiesamestelling in soortgelyke habitatte in verskillende geografiese gebiede. Om verwarring te voorkom, gebruik ek die term streeksdiversiteit vir gamma diversiteit, sensu Whittaker (1972). As die doel van bewaring is om maksimum spesiediversiteit binne 'n streek te bewaar (streekdiversiteit), dan kan hierdie doelwit bereik word deur óf die diversiteit binne elke pleister te maksimeer óf die verskil in pleisterienskappe en dus die variasie van spesiesamestelling tussen kolle (Murphy 1989). N belangrike aanvulling tot inligting oor die alfa spesiediversiteit van 'n kol is dus watter bydrae hierdie kol tot die streekspesiediversiteit lewer (Andrén 1994).

Dit is nie verbasend dat spesierykheid en -diversiteit op 'n eiland of in 'n habitatvlek in die meeste gevalle sal toeneem met eiland of pleisterarea nie. Hierdie verhouding is vir baie dekades bestudeer (Ås et al. 1992, 1997) en is gesien as een van die min egte wette van moderne gemeenskapsekologie (Schoener 1976). Baie kritiese studies het egter geen verskil in diversiteit tussen gebiede van verskillende groottes gevind nie, en daar bestaan ​​inderdaad ook voorbeelde van die omgekeerde verwantskap (bv. MacGarvin 1982, Lathi en Ranta 1985, Loman en von Schantz 1991, Robinson et al. 1992, Vickery et al. 1994).

Alhoewel die diversiteit in 'n kol afhang van sy area, kan 'n minder geïsoleerde kol 'n groter diversiteit hê deur indringing van omliggende habitatte, in vergelyking met 'n meer geïsoleerde kol van soortgelyke grootte. Ek gebruik die term inval want ek sluit beide normale immigrasie en massa-effek in, dit wil sê die vestiging van spesies in terreine waar hulle nie selfonderhoudend is nie (Shmida en Wilson 1985). Die grootte van die verskillende kolle kan ook invalle beïnvloed, en 'n kleiner kol behoort meer vatbaar te wees vir invalle as 'n groot een (Saunders et al. 1991, Hobbs en Huenneke 1992, Halme en Niemelä 1993). Die impak van spesies uit omliggende habitats is van groot belang, veral op habitat-eilande (bv. Janzen 1983, 1986, Shmida en Wilson 1985, Wilcox en Murphy 1985, Andrén en Angelstam 1988, Angelstam 1992, Ås 1994een). Kleiner kolle kan groter wees alfa diversiteit as groter kolle van dieselfde habitat as gevolg van invalle. Die verhoogde ooreenkoms tussen die klein kolle en omliggende habitatte (verminder beta diversiteit) kan gelyktydig lei tot verminderde streekdiversiteit as slegs klein kolle bewaar word.

As kleiner kolle verswak is in terme van spesierykheid, moet ons 'n verskil in diversiteit tussen ewe groot monsters van groot en klein kolle verwag. I have shown in a previous study that this is not necessarily the case for beetles living in dead wood. The diversity of wood-living beetles in small patches (<20 ha) of deciduous forest does not differ from the diversity in larger areas (>100 ha) of similar habitat (Ås 1993). The diversity in this investigation was measured as the residual from the regression of the log-transformed number of species as a function of the logarithm of stem area examined of all dead trees rooted within the sampling plots. This measure of diversity is area independent, and to distinguish between diversity per unit area and total diversity, I will refer to the former as relative diversity. It seems unlikely that the lack of significant reduction in relative diversity is merely a consequence of inadequate sampling, because the mean value from small areas actually exceeds that from larger areas. These patches of deciduous forest are successions after forest fires that occurred approximately 100 years ago, and are distributed in an island-like manner in a conifer-dominated boreal forest landscape. In order to evaluate the relative contribution of large and small patches to regional diversity, I have reanalyzed these data to explore possible reasons for the lack of reduction of relative diversity in small patches.

The hypothesis I test is: invasion and establishment of species from the surrounding habitats explain the lack of reduction in relative diversity in small areas. I also test two alternative hypotheses proposed to explain this pattern: (1) habitat differences between small and large areas explain the observed pattern, and (2) smaller areas harbor more specialized species. If true, the second hypothesis may be attributed to either specialization for small areas per se, or, more likely, specialization for edge habitats. If many species are specialized for edge habitats, then small patches would have higher than expected diversity as a consequence of having a larger proportion of their area as edges. Larger patches will, of course, have a larger total edge area, which will probably harbor a larger total number of species. In relative terms, however, small areas might contain more species than expected if the edge is much more species-rich per unit area than the core.

All areas examined in this investigation are situated in the middle boreal zone (Ahti et al. 1968) of central Sweden, were burned in the late 1880s, and have since been unaltered by man. Samples were also taken in the surrounding managed forest and from small patches of mostly deciduous forest in the vicinity of the areas. The dominating deciduous tree species in all areas are two birch species, Betula pendula en B. pubescens. Approximately 65-70% of the broadleaf trees belong to these species. Aspen (Populus tremula) is the third most abundant species, with 25-30% of all individuals. Goat willow (Salix caprea), gray alder (Alnus incana), and rowan (Sorbus aucuparia) occur regularly but sparsely. The surrounding coniferous forest is dominated by Scots pine (Pinus sylvestris) on drier soils, whereas Norway spruce (Picea abies) dominates in more productive sites. Modern forestry has converted practically all forested areas into managed coniferous forest that are homogenous, both in age structure and in species composition. The surrounding coniferous forests, which later will be referred to as the matrix, thus consist of both clearcuts and mature coniferous forest, and all age classes in between. All of these areas are, to different degrees, exposed to different silvicultural actions such as thinning or removal of deciduous trees. A more detailed description of the study areas can be found in Ås (1993).

Gåsberget (60 o 18' N, 15 o 20' E) is the largest of the areas and is situated in the northeast corner of the county of Dalarna, Sweden. Intense forestry has converted most of the natural forests to managed coniferous forests in this landscape. The deciduous forest at Gåsberget originated in 1888 after a fire that burned an area of approximately 4000 ha (Lundquist 1986). Of this area, 700 ha of naturally revegetated forest has been undisturbed, whereas the rest has been converted to managed coniferous forest, except for a few scattered, small patches of mainly deciduous mixed stands (Fig. 1). In the northern part of the originally burned area, 4 km north of Gåsberget, there is a smaller (<5 ha) deciduous-dominated forest, called Päjertjärn, that resembles the deciduous-dominated mixed-forest patches within the Gåsberget area, in terms of species composition in the tree and field layers (Fig. 1).

The other study area, Brassberget (62 o 12' N, 15 o 47' E), is in the northwestern part of the county of Hälsingland. The forests surrounding this area have not been as intensively managed as those around Gåsberget, and the proportion of deciduous trees and areas with old forest is accordingly higher. The high proportion of deciduous trees and the commonness of fire scars show that the whole region has had frequent fires in past centuries. The forest in and around Brassberget had burned as often as, on average, once every 34 yr before the last substantial fire that occurred in 1888 (Sturesson 1983). This fire covered an area of approximately 460 ha, of which a core area of 109 ha has been left for natural regeneration. This area is now dominated by deciduous forest and is surrounded by coniferous forest and clearcuts (Fig. 1). Five smaller areas, ranging from 5 to 20 ha, of deciduous forest in the vicinity of Brassberget were also examined. Four of them originated after fires, and one is a reforestation of previously cultivated land (Korpåsen, Fig. 2). The species composition of the trees and of the field layer in these areas are very similar to those in the deciduous forest in Brassberget, although Lindmoren is somewhat lusher, with scattered individuals of more southerly species such as linden Tilia cordata.

Substrate availability for beetles living in dead deciduous trees in small and large areas of deciduous forest, measured as the mean basal area of dead deciduous trees (standing and lying) per hectare, did not differ. Large areas of deciduous forest had a basal area of dead deciduous trees of 6.8 0.62 m 2 /ha (mean 1 SE), whereas the corresponding figure for the smaller patches was 7.0 0.98 m 2 /ha (for a more detailed description and statistical evaluation, see Ås 1993).

To determine the species composition within large (>100 ha) and small (<20 ha) areas of deciduous-dominated forest, I investigated a number of sampling plots on three or four occasions. On each sampling date, a 50 x 5 m rectangle within the deciduous dominated forest was examined. From every dead tree (standing or lying) that was, or had been, rooted within the rectangle, I removed bark, cambium, and all loose material between 1 and 1.5 m from the root. All this material, including bark and cambium, was then sieved, and the animals were extracted in Tullgren funnels within 24 hours. Because of the very low density of dead trees in the matrix areas, i.e., managed coniferous forest, a different sampling technique was used. Because a 50 x 5 m area would contain very few dead trees, approximately 20 dead deciduous trees first encountered along a transect were chosen, but each tree was examined in the same way as in the plots. Each 50 x 5 m rectangle, or transect, could be sampled only once, due to the sample technique used. Therefore, on the next occasion, samples were taken from areas next to the one previously sampled. The analyses in this paper are only based on data from the most abundant deciduous tree species, birch (Betula pendula en B. pubescens), aspen, goat willow, and gray alder.

Ten plots were sampled within the Gåsberget area, six in the largest deciduous forest patch, and one in each of the four smaller patches of deciduous forest. One plot was sampled in the Päjertjärn area. All plots at Gåsberget and Päjertjärn were sampled on three different occasions, May and August 1987 and May 1988. In the surrounding managed forest, five sampling plots were selected at random, two in cleared areas and three in mature coniferous forests, all within the originally burned 4000-ha area. Matrix samples were taken in May and August 1988.

In the Brassberget area, three of the five sampling plots were situated in pure deciduous forest. The fourth was located in a pure deciduous stand within the pine-deciduous mixed forest, and the fifth plot was in the spruce-deciduous forest. In the smaller patches of deciduous forest near Brassberget, the two larger ones (Örasjön and Norrtjärnsberget) were sampled with two plots, whereas the three smaller ones (Lindmoren, Korpåsen, and Tväringsberget) contained one each. As at Gåsberget, five plots of managed forest near Brassberget were sampled. Three were in mature coniferous forest and two in clear-cut areas. All plots, except those in managed forest, were sampled in May and August 1987 as well as in 1988. The plots in managed forest were only sampled in May and August 1988.

The material from 1987 and 1988 was pooled in the analyses, because the ranked abundances of the different species were significantly correlated between years. This is true for the two large areas as well as for the combined small areas (Ås 1993).

On each sampling occasion, I measured the amount and quality of resources available for wood-living beetles. The resource amount was measured as the basal area of dead deciduous trees per hectare, whereas the estimates of substrate quality consisted of measurements of the state of decay and the abundance of tree fungi. Decay was estimated for each trunk and divided into four classes: (1) fresh wood (2) bark starting to fall off, some soft wood (3) large parts of the trunk with soft wood and (4) almost no hard wood at all. The amount of fungal infection was classified in a similar fashion: (1) no sign of fungi (2) sparse occurrence of mycelium under bark or in wood (3) rich occurrence of mycelium under bark or in wood, with some (1-3) fruiting bodies and (4) rich occurrence of mycelium and many (>3) fruiting bodies. Because each plot was sampled on three or four different dates and because each new sample was taken in a new 50 x 5 m rectangle close to the previously sampled one, estimations of both means and spatial variability could be made.

The nomenclature of the beetles follows Lundberg (1986), and a more detailed description of the sampling method can be found in Ås (1993).

There is a risk in using the number of individuals of different species when examining the relative abundance of wood-living beetle species because of their clumped distribution. For this reason, the number of occurrences, calculated as the number of trees on which a species was found within a plot, was used as a quantitative estimate of the relative densities of the different species. Few species were found to occur more often in either small or large areas (four and five species, respectively), and only 56 of the 155 species occurred in sufficiently high numbers to allow an analysis of their distribution (Ås 1993). Therefore, the sum of occurrences for species found only in large or only in small areas, respectively, weighted by the total number of occurrences, was used to analyze whether small patches had more occurrences of specialized species than did larger areas.

Ås (1993) found that 13 species occurred more often than expected by chance in managed forest (including clearings). These species were: Tachys nanus (Caribidae), Scaphisoma agaricinum (Scaphidiidae), Gabrius exspectatus, Atrecus pilicornis, Acrulia inflata, Dinaraea aequata, en D. linearis (Staphylinidae), Bibloporus minutus (Pselaphidae), Denticollis linearis en Ampedus nigrinus (Elateridae), Corticaria rubripes (Latridiidae), Cis boleti (Cisidae), and Schizotus pectinicornis (Pyrochroidae). The number of occurrences summed over these species, in large and small patches, respectively, was used to test if the lack of reduction in relative diversity is caused by invasions from matrix habitats.

In total, 3997 beetles of 155 species were collected. Of these, 1630 individuals belonging to 104 species were found in large areas of deciduous forest, and 773 individuals from 83 species were found in smaller deciduous forest patches. The matrix areas sampled in 1988 yielded 1594 individuals of 119 species (a complete species list is available from the author on request or at http://www.zoologi.uu.se/zooeko/stefan/home.html).

To test whether smaller patches offered a more favorable habitat for wood-living beetles, I compared mean substrate availability and quality in small patches to that of larger areas of deciduous forest. I also predicted that a more variable patch would be inhabited by more species. Because it is not obvious whether a higher degree of decay, or fungal infection, should be regarded as high or low quality, the test for these variables is two-tailed. All other tests are one-tailed with H0 : small areas have equal or lower values than large areas. However, there were no differences between small and large areas in any of the variables examined (Wilcoxon two-sample tests see Table 1).

Consistent differences in tree species composition between large and small habitat patches could also influence the result. I compared the mean stem area examined of the different tree species per plot in large and small patches, using MANOVA and a t test for the separate tree species. Neither the MANOVA (Wilks' lambda = 0.832, P = 0.33) nor the t test (Table 2) revealed any significant difference between plots from the different-sized habitat patches.

Patch size
Betula sp.
Populus tremula
Alnus incana
Salix caprea
Groot
1.05 (0.07)
0.74 (0.08)
0.54 (0.11)
0.40 (0.08)
Klein
0.87 (0.08)
0.83 (0.11)
0.50 (0.09)
0.50 (0.12)
t
1.54
-0.70
0.28
-0.64
P
0.13
0.49
0.78
0.53

The sum of the number of occurrences over all species was 647 (Ol) in samples from larger areas, whereas it was 275 for small patches (Os). Species unique to larger areas accounted for 17 of these occurrences (Ul), and 11 occurrences were due to species unique to smaller patches (Us). Hence, the expected number of unique occurrences for large areas was (Ul+Us)Ol/(Ol+Os)=19.65, and for small patches was (Ul+Us)Os/(Ol+Os)=8.35. Large and small areas did not differ in the number of occurrences of unique species (chi-square = 1.234, P = 0.27: Fig. 3).

If the reason for the enhanced diversity within smaller patches (i.e., the lack of reduced diversity as expected from a species-area relation) was invasion of species from the surrounding managed forest, we should expect a relatively higher proportion of occurrences of these species in the smaller patches compared to the larger areas. This prediction was supported. The number of occurrences summed over species preferring matrix habitats was 45 (Ms) in smaller patches and 54 (Ml) for larger areas. The expected number of occurrences for smaller patches was (Ml + Ms)Os/(Ol + Os)=29.53 and for larger areas (Ml + Ms)Ol/(Ol + Os)=69.47. There were significantly more occurrences in samples from smaller patches than from larger areas (chi-square = 12.947, P = 0.001 Fig. 4).

Preservation of the largest possible number of native species in a region is an obvious goal of conservation (Murphy 1989). This goal of maximizing regional diversity can only be achieved by maintaining alpha or beta diversity, or both. It is, however, possible that there is a trade-off between alpha and beta diversity. For example, consider a mosaic of habitats that is replaced with the most diverse habitat type. When converting patches of different habitats to resemble the most species-rich habitat type, most of the species that will be added to the local fauna are species that were already present in the existing patches of the most species-rich habitat. On the other hand, species that were specific to the habitat under conversion may vanish. The end result of this conversion is that each patch will gain species, but the region as a whole will become less diverse (Andrén 1994, Davis 1994). In other words, alpha diversity will increase in each patch, but beta diversity simultaneously will decrease and the net result will be a reduced regional diversity.

The relative increase in diversity in small patches can, at least temporarily, be even more exaggerated if the small-sized patches are results of a fragmentation process. When the size of an area is restricted because of modification of the surrounding area, it may initially have a large fraction of the original species present. Due to low population sizes, many of these species may go extinct, causing a relax to a number, the size of which depends on area (MacArthur and Wilson 1967). At the same time, the area is exposed to invasion of species from the altered surrounding areas. If the relaxation in the number of species that was originally present is slow relative to the invasion of new species, then the diversity may increase initially as a consequence of the fragmentation (Verner 1986, Murphy 1989, Webb 1989, Harris and Scheck 1991, Saunders et al. 1991). This phenomenon may occur in my study area, because most of the intensive forestry actions responsible for the fragmentation of the deciduous forest are fairly recent (< 50 yr Esseen et al. 1992, 1997, Ås 1993).

The invasion of species into a small patch is an edge effect. The species that will gain from a fragmentation of larger habitat patches are those that thrive in edge habitats, independent of whether or not the edge is their prime habitat (Andrén 1992, Angelstam 1992, Hobbs and Huenneke 1992). It is true that a larger patch will have a larger edge area, which probably will harbor more species than the smaller edge area from a smaller patch. In a landscape with a given amount of habitat, however, fragmentation into small patches will lead to an increase of the total amount of edge area. The relative proportion of edge-thriving species will therefore increase, probably with negative impact on the species restricted to the patches. If small patches are more species-rich than expected, and this increase in species number has been caused by species that are specialized on edge habitats, then small patches could increase the regional diversity, depending on whether edge habitat was common or rare before fragmentation (Andrén 1994). In the present case, however, a more probable cause of a higher than expected relative diversity of wood-living beetles in small patches is the addition of species from the managed matrix forest which, hence, will reduce the beta diversity.

If invasion from the matrix is the prime reason for the presence of extra species in the edge, an edge from a large patch is probably not equal to an edge from a small patch, in terms of species composition. Assume that population density and mean dispersal distances are equal for patch and matrix species. If patch size were considerably larger than the mean dispersal distance of an individual, a dead tree at the edge of a patch would get approximately 50% of all new individuals from within the patch. With decreasing patch area, a diminishing part of the area within the dispersal range would be patch habitat. As a consequence, a larger amount of all individuals reaching the dead tree will originate from the matrix habitat.

In the case of wood-living beetles in boreal-zone deciduous trees, a great part of the high diversity in the small patches of deciduous forest is clearly due to invasions by species from the managed forest. Most of these species mainly inhabit clear-cut areas. This is not surprising, because disturbance by forest fires and windstorms, under pristine conditions, frequently creates large, open patches with abundant substrate available for a limited time. This type of habitat should favor species with good colonization ability. Likewise, these species should also be superior in invading edge habitats in the vicinity.

In this experiment, different-sized patches did not differ in habitat quality or in the occurrence of unique species. It seems reasonable to assume that smaller patches become more similar to matrix areas in their species composition over time and, thus, contribute less to the regional species diversity than do larger areas. Because of the relatively short time since the fragmentation of these deciduous forests, it is possible that the loss of specialized species from small patches might be exacerbated with time. On the other hand, these small patches are probably important in a landscape context. They may act as sink areas that increase the population size of species otherwise restricted to larger areas (Pulliam 1988, Danielson 1992, Dunning et al. 1992). They may also increase the landscape connectivity and, as a result, facilitate colonization of new, large patches of deciduous-dominated forest (Taylor et al. 1993). These positive effects of small areas thus depend on the presence of larger areas, which need to be preserved to maintain regional diversity.

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I thank J. Bengtsson, T. Ebenhard, S. Ulfstrand, and Stanly H. Faeth for valuable comments on the manuscript, and L.-O. Wikars for assisting in the field and identifying the numerous specimens, together with R. Baranowski. This work has been financially supported by the Swedish Environmental Protection Agency and the Crafoord Foundation.

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Crown

Like roots, trunks and branches grow in length from apical meristems found in buds, which are essentially telescoped shoots, leaves, and/or flowers. Buds containing all of the above are referred to as mixed, while those containing one or the other are referred to as either leaf buds or shoot buds. The terminal bud, located at the apex of the main stem, forms the trunk of the tree over time. Lateral buds, formed at the leaf axils and nodes along the trunk, grow into branched and flowers.

Within the bud, two growth habits are possible, fixed growth and free growth. Fixed growth occurs in species such as pines, hickory, and oaks, where the buds contain a preformed shoot. All of the components of next year's shoot are contained in the bud formed this year the number of leaves and nodes is predetermined by this year's environmental conditions. The length between leaves and nodes is influenced by the environmental conditions the tree encounters next year. Free growth, in species such as cottonwood, willow, and silver maple, occurs when buds contain shoots with some preformed leaves, but which are also capable of forming additional leaves. These species can continue to grow as long as environmental conditions are favorable. Recurrently flushing growth occurs on many shrubs. These species produce a series of buds at the tip of the same elongating shoot in waves or flushes. Some fixed growers, under favorable growing conditions, are also capable of a second flush of growth in one season.


Improving public awareness of the importance of deadwood

Many environmental education programs mention the importance of deadwood for biodiversity in only general and superficial ways. This is possibly because most invertebrate species found in deadwood have a low public profile, are small and inconspicuous, lack appealing characteristics for a non-scientific audience, and are rarely represented in conservation efforts (Barua et al. 2012 Eckelt et al. 2018). In contrast, some species perceived as forest pests, such as bark beetles, receive substantial (and largely negative) attention by a broad audience (Flint et al. 2009). This underscores the challenge for environmental education in raising awareness of the importance of deadwood, not only among the general public but also among land managers, policy makers, and even scientists. Environmental education programs that target different groups are needed to overcome centuries of negative perceptions about deadwood and natural forest dynamics, and to foster greater awareness of the critical importance of deadwood for forest biodiversity. A large proportion of the few existing deadwood education programs in Europe are based on guided forest visits with groups of people and rely on informative outdoor displays (Figure 4c) that focus on species found in deadwood, nutrient cycles, and the natural decay of large, old trees. Such educational forest visits can enhance conservation-related knowledge and long-term retention of gained knowledge (Kuhar et al. 2010 ). Another promising approach is to adapt the flagship-species concept to environmental education programs (Eckelt et al. 2018 ), in which particular taxa are highlighted and used to stimulate interest in the ecological importance of deadwood. Selecting flagship species from higher trophic levels in saproxylic food webs, such as birds or mammals, might help to foster positive attitudes toward deadwood. One potential example is the barbastelle bat (Barbastella barbastellus), which uses deadwood and forest stands decimated by bark beetles as nesting, roosting, and foraging sites (Kortmann et al. 2018). Likewise, the white-backed woodpecker is a charismatic species that forages on dry snags, and therefore could be selected both as a flagship species for deciduous forest conservation and as a tool for communicating deadwood conservation (Roberge et al. 2008 ).

Environmental education programs may emphasize the importance of deadwood through illustrated children's books about (a) the life history of relict species within primary forests and the important role of saproxylic invertebrates as food resources for higher trophic level species, such as (b) the white-backed woodpecker (Dendrocopos leucotos) feeding on larvae of the wood borer (Ptilinus pectinicornis). These programs may also rely on resources such as (c) information panels posted in forests describing the importance of deadwood for forest biodiversity and the interactions between wood-inhabiting fungi and saproxylic beetles, and (d) stickers of “Berti” the bark beetle highlighting the natural dynamics that lead to the creation of deadwood.© S Zuda #x00A9 S Zuda Harz National Park

Flagship species can be utilized in education programs, for instance via richly illustrated children's books (Figure 4), which can help trigger interest in and greater appreciation of the value of deadwood by a broad audience. Yet because the effectiveness of deadwood-specific environmental education programs is largely unknown, such programs must be subject to quantitative evaluation, measuring success via the presence and quality of deadwood and associated biodiversity, in addition to the human dimensions of forest ecosystems. A greater focus on interdisciplinary research is also needed to identify knowledge gaps and diverging conceptions, which could be targeted through an array of educational programs encompassing various teaching methods, including novel approaches like video games (Chang 2019 ).


Foliage dynamics, leaf traits, and growth of coexisting evergreen and deciduous trees in a tropical montane forest in Ethiopia

Foliage dynamics of three functional tree types representing major components of the tropical montane evergreen forest in southern part of Central Ethiopia were compared. The species were Podocarpus falcatus (evergreen gymnosperm), Prunus africana (evergreen broadleaf), and Croton macrostachyus (facultative deciduous). The hypothesis examined is that in such tropical trees, endogenous control of foliage dynamics by the leaf life-spans (LLS) is largely dominant over external signals. Crown foliage turnover, leafiness of twigs, LLS, photosynthetic performance, respiration rate, specific leaf area, and relative growth rates of the stems were investigated. Foliage dynamics and leafiness of the twigs were monitored over 2 years while leaf traits were followed over 3 months. The degree of inter and intra-individual synchronization of foliage phenophases was examined to get an estimate of the contributions of endogenous and external signals to the dynamics of the foliages. Autoregression analysis indicated significant influence of the moisture regime on leaf sprouting of Croton en Podocarpus. During pronounced dry periods, new leaves were not developed. Analysis of phenological data using circular statistics revealed that in spite of strong inter-individual synchronization of leaf flush and fall (Podocarpus en Croton), the dynamics of individual parts of the crowns were less synchronized. LLS was independent of climate factors and it had substantial contribution to the control of foliage turnover. Moreover, examination of ecophysiological traits of developing leaves of the studied functional types showed differing patterns with LLS corroborating the ecophysiological characteristics. Although overlaid by fungal infestation, both the foliage and ecophysiological properties of Prunus resemble that of Podocarpus but the former exhibited a shorter LLS and slightly higher metabolic rates. Nevertheless, all species reacted positively to high moisture with respect to stem growth. In spite of largely differing weather conditions of the 2 years, direct competitive advantage of one of the species over the others could not be detected.

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