What are tree snorkels?

BBC Wildlife Magazine - - Q&a - Chris­tian Dunn

Trees grow­ing in flooded soils re­quire spe­cial adap­ta­tions if they are to sur­vive this wa­tery habi­tat. One of the prob­lems they face is how to make sure their roots re­ceive suf­fi­cient oxy­gen to func­tion prop­erly.

In much the same way that we can use snorkels to breathe if we want to keep our heads un­der­wa­ter, trees with sub­merged roots de­velop spe­cialised root struc­tures known as pneu­matophores. Brave the wa­ters of a man­grove swamp and you will see th­ese slen­der, stick-like struc­tures in their thou­sands, pro­trud­ing from the soil and shal­low wa­ter. Pneu­matophores are usu­ally about 30cm in length. They take in oxy­gen through mi­nus­cule pores known as lenticels and trans­port it down into the deeper root sys­tem, cre­at­ing a thin, oxy­gen-rich layer around the very base of the plant. In­deed, ex­per­i­ments have re­vealed that if the pneu­matophores are cov­ered, the trans­porta­tion of oxy­gen ceases and the man­groves die. Another adap­ta­tion of man­grove trees are stilt roots, or prop roots – pitch­fork-like ex­ten­sions from the trunk that grow down­wards into the sed­i­ment, help­ing to sta­bilise the plants against tides and flood­ing.

A fish-eye view of the snorkel-like roots of the black man­grove tree.

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