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Wood wide web: trees’ social networks are mapped 

    Research has shown that beneath every forest and wood there is a complex underground web of roots, fungi and bacteria helping to connect trees and plants to one another. This subterranean social network, nearly 500 million years old, has become known as the “wood wide web”. Now, an international study has produced the first global map of the “mycorrhizal fungi networks” dominating this secretive world.

    Using machine-learning, researchers from the Crowther Lab at ETH Zurich, Switzerland, and Stanford University in the US used the database of the Global Forest Initiative, which covers 1.2 million forest tree plots with 28,000 species, from more than 70 countries. Using millions of direct observations of trees and their symbiotic associations on the ground, the researchers could build models from the bottom up to visualise these fungal networks for the first time. Prof Thomas Crowther, one of the authors of the report, told the BBC, “It’s the first time that we’ve been able to understand the world beneath our feet, but at a global scale.”

    The research reveals how important mycorrhizal networks are to limiting climate change — and how vulnerable they are to the effects of it. “Just like an Magnetic Resonance Imaging scan of the brain helps us to understand how the brain works, this global map of the fungi beneath the soil helps us to understand how global ecosystems work,” said Prof Crowther. “What we find is that certain types of microorganisms live in certain parts of the world, and by understanding that we can figure out how to restore different types of ecosystems and also how the climate is changing.” Losing chunks of the wood wide web could well increase “the feedback loop of warming temperatures and carbon emissions.”

    Mycorrhizal fungi are those that form a symbiotic relationship with plants. There are two main groups of mycorrhizal fungi: arbuscular fungi (AM) that penetrate the host’s roots, and ectomycorrhizal fungi (EM) which surround the tree’s roots without penetrating them.

                                                (Claire Marshall. www.bbc.com, 15.05.2019. Adaptado.)

Cinco cargas elétricas pontuais positivas encontram-se fixas no vácuo de acordo com o arranjo da figura a seguir. O campo elétrico resultante sobre Q2 aponta na direção que une as cargas Q2 e Q4. Nessa situação, pode-se afirmar que (Q1D2 ) /(Q3L2 ) vale:

O escritor Mário de Andrade fez uma viagem em comitiva à Amazônia e escreveu um diário sobre o périplo, que durou de 13 de maio a 15 de agosto de 1927. Leia alguns trechos desse diário.

Belém, 19 de maio
Depois do jantar, sem que fazer, fomos todos ao cinema ver a fita importante que os jornais e as pessoas anunciavam, William Fairbanks em Não percas tempo, filme horrível.
Manaus, 7 de junho.
De-noite, sem que fazer, fomos ao cinema. Levavam com grande barulho de anúncio William Fairbanks em Não percas tempo.
Iquitos, 25 de junho.
Me esqueci de contar: ontem, passeando, passamos pelo cinema local que com grande estardalhaço anunciava último dia do grande filme Não percas tempo com William Fairbanks. É que o filme ia e vinha no navio conosco...

(Mário de Andrade. O turista aprendiz, 2002. Adaptado.)