The Mys­te­ri­ous Uni­verse Of The Oak

The fas­ci­nat­ing world of the oak tree (and its in­hab­i­tants)

World of Knowledge (Australia) - - Contents -

It can live for cen­turies, gives shel­ter to thou­sands of dif­fer­ent an­i­mal species and pro­vides us with the oxy­gen we need to live. Oak trees are one of the most in­cred­i­ble mir­a­cles of na­ture

rom one sec­ond to the next the gnarled branch of the old oak tree is trans­formed into an arena: as the sun sets on the hori­zon, two male stag bee­tles get ready for a tree­top duel – their antler-like mandibles di­rected threat­en­ingly in the other’s di­rec­tion. Usu­ally, this would be the cue for them to storm to­wards each other and at­tempt to throw the other onto its back with their three-cen­time­tre-long jaws, or to push their op­po­nent from the branch. But this time things are rather dif­fer­ent: one of the bee­tles be­gins to teeter pre­car­i­ously and shortly af­ter­wards tum­bles to the ground be­low.

The duel is over be­fore it has be­gun – be­cause the bee­tle made a fa­tal mis­take: be­fore the bat­tle it slurped away on a sug­ary juice found drip­ping from a crack in the oak. What the in­sect didn’t re­alise was the oak’s sweet sap had been fer­mented into al­co­hol by bac­te­ria. The bee­tle’s op­po­nent doesn’t look in the least bit wor­ried by this: he’s ex­cited about pick­ing up the spoils of his vic­tory, a fe­male, and lets off a tri­umphant buzzing to cel­e­brate. This is just one of many fas­ci­nat­ing sto­ry­lines that play out daily in the uni­verse of the oak, and which have done for mil­lions of years.

WHERE IS THE OLD­EST OAK TREE IN THE WORLD?

The Pechanga Great Oak Tree in Te­mec­ula, Cal­i­for­nia, is around 2,000 years old. And Stand­ing in a field in Man­thorpe in the UK is a tree be­lieved to be about 1,000 years old. Known as the Bowthorpe Oak, the tree’s trunk is now hol­low but its stag­ger­ing 15-me­tre cir­cum­fer­ence is so cav­ernous it’s claimed that 39 peo­ple once man­aged to stand in­side it.

These two gi­ant trees have ob­served the lives and deaths of sev­eral gen­er­a­tions of peo­ple. They’ve seen wars and nat­u­ral dis­as­ters, and been wit­ness to ex­cit­ing new eras – al­most in a time lapse, as if they have lived life in slow mo­tion. Oaks grow just four cen­time­tres in height ev­ery year while a spruce man­ages 37 cen­time­tres per year. An oak grows for half a cen­tury be­fore it car­ries its first blos­soms. And yet ev­ery oak forges its own in­di­vid­ual his­tory as a mi­cro­cosm for thou­sands of liv­ing or­gan­isms. The tree is a mys­te­ri­ous con­ti­nent on which the great­est mir­a­cle of na­ture is waiting to be dis­cov­ered.

HOW MANY TONS OF DUST DOES AN OAK FIL­TER FROM THE AIR?

In spring, once the cold weather has gone and tem­per­a­tures are fi­nally ris­ing, the oak wakes up from its win­ter sleep. The buds start to open pretty much im­me­di­ately and the first green leaves soon be­come vis­i­ble. Shortly af­ter­wards, the char­ac­ter­is­tic lobed leaves be­gin to shoot ev­ery­where on the oak’s branches and twigs. The first blos­soms ap­pear. On ev­ery male flower or catkin there are up to 40,000 pol­lens, which are car­ried to the fe­male flow­ers by the wind.

The leaves of the oak are true mir­a­cles of na­ture: not only do they act as a source of nu­tri­ents and a nest­ing place for count­less an­i­mal species, they also serve as um­brel­las, cli­mate con­trol units, air fil­ters and oxy­gen fac­to­ries com­bined.

“Us­ing its 150,000 leaves, a 100-year-old oak tree con­verts around 6,000kg of car­bon diox­ide per year into 45,000 kg of oxy­gen,” ex­plains bi­ol­o­gist Mario Lud­wig. That’s equiv­a­lent to the an­nual re­quire­ment of 11 peo­ple. The tree also func­tions as an ac­tive F

“There is some­thing to dis­cover in ev­ery oak. If you are quiet and pa­tient, the tree will re­veal its se­cret.” SOLVIN ZANKL, PHO­TOG­RA­PHER

air fil­ter: with a leaf sur­face area of up to 1,600 square me­tres, it fil­ters up to a ton of pol­lu­tion-con­tain­ing dust a year.

Above all, the si­lent giants are a com­plex ecosys­tem that of­fer a habi­tat to more than 1,000 species of an­i­mal – no other tree pro­vides as much shel­ter. Over the course of evo­lu­tion each one has adapted to the unique liv­ing con­di­tions of the oak tree and de­vel­oped strate­gies to sur­vive.

WHICH AN­I­MALS NEED DY­ING OAKS TO SUR­VIVE?

Many crea­tures ben­e­fit from eat­ing the car­bo­hy­drate-rich, fatty fruits of the oak: the acorns. Un­like wild boar or dormice, at least the Eurasian jay makes it­self use­ful while do­ing so by con­tribut­ing – al­beit un­in­ten­tion­ally – to the dis­per­sal of the tree. In au­tumn it buries acorn re­serves un­der the soil that it can of­ten not find again so that, in some spots, new oak saplings are al­ready sprout­ing by the next year.

Many in­sects have also dis­cov­ered the nu­tri­ent-rich tree fruits for them­selves – both as a hid­ing place for their off­spring and as a source of nour­ish­ment. The acorn wee­vil de­posits its eggs in acorn shells, which helps pro­tect them from hun­gry preda­tors as well as mean­ing the lar­vae will be greeted with an op­u­lent feast when they hatch. Their close re­la­tion, the oak leaf-rolling wee­vil, folds art­ful nests from the oak leaves by cut­ting through the leaf, rolling up the sides and curl­ing it up from the tip. It then lays a sin­gle egg in­side.

Even in­side the oak leaves and deep in the tree bark there ex­ists a wealth of hid­den riches unique to the oak tree: here the leaf min­ers are in charge – the tiny lar­vae of flies, but­ter­flies and bee­tles which eat straight through the oak and leave be­hind empty cor­ri­dors, known as mines, in the process. Some of them, like the oak bark bee­tle, can quickly be­come a real nui­sance to the gi­ant trees thanks to their in­sa­tiable hunger. Trees in­fested by the pest ex­hibit gen­eral symp­toms of de­cline in­clud­ing re­duced growth, wilted fo­liage and

LEAF ARTIST Be­fore lay­ing their eggs, fe­male leaf-rolling wee­vils use their pro­boscis and legs to cre­ate art­ful nests from oak leaves.

HANG­ING BY A THREAD The grubs of the win­ter moth feed on oak leaves and pull them­selves from tree to tree us­ing self-spun threads. At the end of May they make their way down to the ground to pu­pate.

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