Giant trees have no trouble pumping water to top branches

77 pointsposted 3 hours ago
by hhs
(news.exeter.ac.uk)

33 Comments

calibas

an hour ago

The largest tree on record is rejected in part because it's over the theoretical limit: https://en.wikipedia.org/wiki/Nooksack_Giant

Too bad we cut it down, along with almost every other giant Douglas-fir.

Alien1Being

35 minutes ago

Human barbarism is not new...

"The placard recorded that the Nooksack tree produced 96,345 board feet (227.348 cubic meters) of the "finest quality" lumber.

The New York Times regarded the tree in a March 7, 1897 issue as the "most magnificent fir tree ever beheld by human eyes" and called its destruction a "truly pitiable tale" and a "crime".

The Morning Times of February 28, 1897 claimed that the wood, sawed into one-inch strips, would reach from "Whatcom [the tree's location] to China"."

hinkley

an hour ago

There are stories that the moss on trees in temperate rainforests allow the tree to pull water from their branches instead of the ground, increasing their max height.

For a while there were people poaching the moss that facilitated this, which is a problem because it grows only inches per year.

ryanmcbride

an hour ago

God that's sad. We really can't have anything nice.

hinkley

an hour ago

It’s harder to remove the moss from high up in the tree and there are more risks in doing so. I was never clear on how prevalent this shittery was.

nomel

2 hours ago

This goes against all previous research/measurements for actually tall trees (looks like they only considered up to 80m) and the fact that there are exactly zeros trees in the world taller than 130 meters [1]. Wide capillaries at the base, like stated in the article, don't seem to be related.

[1] https://www.sfgate.com/science/article/REDWOODS-How-tall-can...

nullorempty

2 hours ago

>Giant trees have no trouble pumping water to top branches

Hm, may be because they are not really "pumping" the water?

leni536

2 hours ago

What would you call it?

cj

2 hours ago

Not that it really matters, but the article also refers to it as “drawing water to the top”. That seems more representative of reality than “pumping water from the bottom”.

chowells

2 hours ago

If you think of it that way, you have a real problem. It only takes about 10 meters for the weight of a column of water to create enough downward force that it starts vaporizing, at which point no pumping action works. This is why any deep well has a submerged pump. You simply can't pull water upward further than that with negative pressure in the Earth's atmosphere. It must be pushed with positive pressure instead.

This is why the question is interesting. You can't just suck water to the top of a 60 meter tree. There must be some kind of positive-pressure pumping involved.

pulvinar

2 hours ago

The trick for trees is capillaries, which change the equation. The 10 meter limit only applies to larger columns. With capillaries there's a high negative tension that allows evaporation from leaves to pull the xylem sap up 100 meters or more.

There's no free lunch here. The Sun drives the evaporation, and if the tree were in a closed system with no solar input, the humidity would eventually get high enough to stop it.

hinkley

an hour ago

One of the things Susan Simard proved was that deep rooted trees that had found subterranean water continue pulling that water at full speed at night when transpiration is low, and that water finds its way into the fungal networks in the soil and into nearby plants.

Simard attributes intention to this, but osmosis is “fair”. It seeks to move water to where sugars are and sugars to where water is. So a plant giving up sugars will receive water, and one low on water will give up sugars in the process of equalization.

Do fungi contain pumps to maintain disequilibrium in this work? I could not say. But even when they first learned the trick of tapping roots the basic premise would have worked in a rudimentary fashion woth no further optimization.

tenuousemphasis

an hour ago

>if the tree were in a closed system with no solar input

... that would be the least of the tree's problems.

margalabargala

2 hours ago

Yeah it's the difference between creating low vs high pressure.

card_zero

2 hours ago

The low pressure is up there already, for free.

Or the high pressure is down here, whichever way you want to look at it.

rolph

2 hours ago

more like capillary action.

https://en.wikipedia.org/wiki/Xylem#Cohesion-tension_theory

rolph

an hour ago

the research is relevant to the issue of transpiration column hieght as a postulated limitation to overall hieght of any tree.

a column of water is pulled by hydrogen bonding between molecules in a tug of war fashion, the top of the column is where water is dissociated from the column at such a rate as to maintain low pressure with respect to the column[xylem]

in summary water moves from bottom to top in a transpiration stream, that ultimately ejects water vapour from the leaves, resulting in a low efficiency mechanism, that loses a lot of the water but occurs at such a rate that the low efficiency is "good enough" for whats needed.

card_zero

2 hours ago

Oh, so we don't really know how it works. Fun.

gitaarik

2 hours ago

“Trees contain lots of thin, hollow vessels and they suck water upwards by creating low pressure at the top,”

So sucking / pulling?

IsTom

2 hours ago

So a suction pump?

card_zero

2 hours ago

Same principle as chimneys. But I also noticed this line:

> leaves which have adapted to withstand greater water stress before wilting.

That must be one of the "adjustments to water transport" mentioned. So I suggest that they do, in fact, have trouble pumping water to top branches.

gitaarik

2 hours ago

Maybe it's not more trouble pumping, eh, sucking water up. But that the top branches are the last ones to get water in periods of draught, and have therefore more resilience?

DANmode

2 hours ago

Or, it’s simply a rate to variably adjust to, so the tree is neither flooding nor parching the leaf.

hinkley

an hour ago

My recollection is that capillary action is a little from column a and a little from column b.

m463

2 hours ago

on the other hand, many giant trees get the water out of the air via fog:

Coalescence of coastal fog accounts for a considerable part of the trees' water needs.[23]

https://en.wikipedia.org/wiki/Sequoia_sempervirens#Fog_and_f...

https://en.wikipedia.org/wiki/Sequoia_sempervirens

efskap

an hour ago

Similarly, it blows my mind that all trees are made of air, specifically the carbon in it. I used to think that the biomass must come from the soil, but reality is more interesting.

kulahan

a minute ago

It's also kind of weird to think that soil, really, is just ground up "stuff" that used to be trees, plants, rocks, etc.

c22

an hour ago

Kind of like how the vast majority of weight loss in animals happens via exhaling.

Weirder still is the realization that all the air is just trapped light.

hinkley

an hour ago

There’s also a theory that the moss on these trees is mutualism instead of simply epiphytic. The moss holds moisture, which can be accessed by the tree.