Most of the forest lives in the shadow of the giants that make up the highest canopy. These are the oldest trees, with hundreds of children and thousands of grandchildren. They check in with their neighbors, sharing food, supplies, and wisdom gained over their long lives.
Veći deo šume živi u senci džinova koji čine najviše krošnje. To je najstarije drveće koje ima na stotine dece i na hiljade unučadi. Posećuju svoje komšije, deleći hranu, zalihe i mudrost stečenu tokom svojih dugih života.
They do all this rooted in place, unable to speak, reach out, or move around. The secret to their success lies under the forest floor, where vast root systems support the towering trunks above. Partnering with these roots are symbiotic fungi called mycorrhizae.
Sve ovo postižu ukorenjeni u mestu, nesposobni da govore, protegnu se ili da se kreću. Tajna njihovog uspeha počiva ispod šumskog tla, gde ogromni sistemi korenja podržavaju visoka stabla nad zemljom. U partnerstvu sa korenjem su simbiotske gljive nazvane mikorize.
These fungi have countless branching, thread-like hyphae that together make up the mycelium. The mycelium spreads across a much larger area than the tree root system and connect the roots of different trees together. These connections form mycorrhizal networks. Through mycorrhizal networks, fungi can pass resources and signaling molecules between trees.
Ove gljive imaju bezbroj razgranatih hifa u vidu niti koje zajedno sačinjavaju miceliju. Micelije se prostiru duž znatno većeg prostora od ovih sistema korenja i povezuju korenje različitog drveća. Ove veze obrazuju mikorizalne mreže. Putem mikorizalnih mreža, gljive mogu da prenose resurse i signalne molekule između drveća.
We know the oldest trees have the largest mycorrhizal networks with the most connections to other trees, but these connections are incredibly complicated to trace. That’s because there are about a hundred species of mycorrhizal fungi– and an individual tree might be colonized by dozens of different fungal organisms, each of which connects to a unique set of other trees, which in turn each have their own unique set of fungal associations. To get a sense of how substances flow through this network, let’s zoom in on sugars, as they travel from a mature tree to a neighboring seedling.
Znamo da najstarije drveće ima najveće mikorizalne mreže sa najviše veza sa drugim drvećem, ali ove veze je izuzetno teško pratiti. Razlog tome je što postoji oko stotinu vrsta mikorizalnih gljiva - a pojedinačno drvo može da bude u koloniji sa desetinama različitih vrsta gljiva, od kojih svaka stvara veze sa određenim skupom drugog drveća, a koji opet imaju sopstvene jedinstvene skupove društava gljiva. Kako bismo imali uvid u to kako materija kruži ovom mrežom, posmatrajmo izbliže šećer dok putuje od zrelog drveta do komšijske mladice.
Sugar’s journey starts high above the ground, in the leaves of the tallest trees above the canopy. The leaves use the ample sunlight up there to create sugars through photosynthesis. This essential fuel then travels through the tree to the base of the trunk in the thick sap.
Putovanje šećera započinje visoko nad tlom, u lišću najvišeg drveća iznad šumske kupole. Lišće koristi obilje sunca kako bi proizvelo šećer putem fotosinteze. Ovo esencijalno gorivo potom putuje kroz drvo do podnožja stabla u vidu gustog biljnog soka.
From there, sugar flows down to the roots. Mycorrhizal fungi encounter the tips of the roots and either surround or penetrate the outer root cells, depending on the type of fungi. Fungi cannot produce sugars, though they need them for fuel just like trees do. They can, however, collect nutrients from the soil much more efficiently than tree roots— and pass these nutrients into the tree roots. In general, substances flow from where they are more abundant to where they are less abundant, or from source to sink. That means that the sugars flow from the tree roots into the fungal hyphae. Once the sugars enter the fungus, they travel along the hyphae through pores between cells or through special hollow transporter hyphae. The fungus absorbs some of the sugars, but some travels on and enters the roots of a neighboring tree, a seedling that grows in the shade and has less opportunity to photosynthesize sugars.
Odatle, šećer se spušta do korenja. Mikorizalne gljive pronalaze vrhove korenja i opkoljavaju ga ili prodiru kroz spoljne ćelije korenja, u zavisnosti od vrste gljive. Gljive ne mogu da proizvode šećer, iako im je potreban baš kao i drveću. Mogu, pak, da sakupljaju hranljive materije iz tla mnogo efikasnije od korenja drveća - i prebacuju te hranljive materije u korenje drveća. Uglavnom, supstance teku s mesta gde ih ima više do mesta gde su oskudnije, ili od izvora do ušća. To znači da šećeri putuju od korenja drveća do hifa gljiva. Kada šećer dospe u gljive, putuje duž hifa kroz pore između ćelija ili kroz naročite šuplje transporterske hife. Gljive apsorbuju deo šećera, ali ostatak putuje dalje i dolazi do korenja susednog drveta, do mladice koja raste u senci i ima manje šanse da stvara šećer fotosintezom.
But why does fungus transport resources from tree to tree? This is one of the mysteries of the mycorrhizal networks. It makes sense for fungus to exchange soil nutrients and sugar with a tree— both parties benefit. The fungus likely benefits in less obvious ways from being part of a network between trees, but the exact ways aren’t totally clear. Maybe the fungus benefits from having connections with as many different trees as possible, and maximizes its connections by shuttling molecules between trees. Or maybe plants reduce their contributions to fungi if the fungi don’t facilitate exchanges between trees.
Međutim, zašto gljive prebacuju materije od drveta do drveta? Radi se o jednoj od misterija mikorizalnih mreža. Za gljivu ima smisla da razmenjuje hranu i šećer iz tla sa drvetom - obe strane imaju korist. Gljive najverovatnije imaju manje očitu korist od toga što su deo mreže između drveća, ali tačno kako nije baš najjasnije. Možda gljive imaju koristi od veza sa raznim različitim drvećem koje postoji i pojačavaju svoje veze tako što prebacuju molekule između drveća. Ili, pak, biljke umanjuju svoj doprinos gljivama ako gljive ne olakšaju razmene među drvećem.
Whatever the reasons, these fungi pass an incredible amount of information between trees. Through the mycorrhizae, trees can tell when nutrients or signaling molecules are coming from a member of their own species or not. They can even tell when information is coming from a close relative like a sibling or parent. Trees can also share information about events like drought or insect attacks through their fungal networks, causing their neighbors to increase production of protective enzymes in anticipation of threats.
Šta god da je razlog, ove gljive prenose neverovatne količine informacija među drvećem. Kroz mikorize, drveće zna da li hrana ili molekuli signalizatori stižu od člana njihove sopstvene vrste ili ne. Mogu čak da znaju kada informacija stiže od bliskog rođaka, brata ili roditelja. Kroz svoje mreže gljiva, drveće može i da deli informacije o događajima poput suše ili o napadima insekata, navodeći tako svoje komšije da pojačaju proizvodnju zaštitnih enzima u iščekivanju pretnji.
The forest’s health relies on these intricate communications and exchanges. With everything so deeply interconnected, what impacts one species is bound to impact others.
Zdravlje šume počiva na ovim zapetljanim komunikacijama i razmenama. Kada je sve tako duboko isprepletano, ono što utiče na jednu vrstu mora da utiče i na druge.