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sucking up water through needles

Posted by ken_adrian z5 (My Page) on
Thu, Aug 7, 08 at 11:32

ok ... 6 weeks... 90+ degrees [in C that translates to really, really hot .....] ... very high humidity .. which means the sand is bone dry ...

i am not really watering the 3+ year old plants .... but while waiting for the dry sand surface tension to let the water go into the soil on the babes .. i was 'creating' rain on the larger plants ...

figuring i am washing dirt off the needles ... figuring any water is better than no water..

then began to wonder if they can actually suck in [whats the opposite of transpiration?]significant amounts of water through their leaves .... and starting thinking about the fog rolling off the pacific ocean .. and the west side of the mountains [what is that area called] .. and wondered if there are actually areas that are near desert ... yet nearly rain forest.. just from the fog ...

anyway .... am i accomplishing anything other than wasting time.. in watering needles??

ken


Follow-Up Postings:

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RE: sucking up water through needles

Yes, for sure, watering the needles / leaves helps plants. Observation from experience. Don't know why scientifically. But at least it does help clean them and keep bugs off, and some water drips down into the earth. Conifers in my yard love to be misted. The coast redwoods demand it.

The deciduous trees in my yard seem to like it too. Those trees regularly sprinkler watered are significantly more robust and green and glossy than those getting primarily hose-watered in their wells.

I would still be sure to water the ground around the trees well and deeply to give the roots water. Heat, sun and wind dry up the earth fast.


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RE: sucking up water through needles

Not sure if they can absorb water directly through their leaves, but wet leaves are cooled by evaporation, and when cooler they're under less stress.

Resin


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RE: sucking up water through needles

Experiments done in the 1950s and 60s showed that ponderosa pine needles took in water from fog, through the stomates. I don't know if further such work has been done. No Ken, there are no deserts converted to rain forests by fog drip, but fog drip does greatly increase the water available to trees in the Pacific fog belt, by up to 30 inches annually as I recall. Fog drip has been the subject of considerable research. It doesn't require trees -- metal structures mimicking trees were used successfully on Hawaiian ridgetops years ago to "milk" the water out of passing fog.
No, redwood does not really require fog for its growth or health. We have plenty of big vigorous redwoods in my Sierra Nevada community where the long summers are bone-dry, and fog is an occasional winter event.


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RE: sucking up water through needles

It seems like with many large dense conifers, like a Colorado Spruce, that little rain actually makes it down under the tree, unless the rain is very hard or blowing. Old needles and dry soil under the tree.

Does this have a purpose? If the tree does not absorb water from the needles, then the moisture would mostly evaporate from the needles. The dry area under the tree gives little opportunity for other trees to grow under the tree, but then the roots inside the branches get a lot less water than the roots outside the branches.


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RE: sucking up water through needles

I remember reading that fog drip in Pinus canariensis cloud forests on the north slope of Tenerife (Canary Islands) increased annual precipitation from 50cm in the open to 200cm under the trees.

Resin


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RE: sucking up water through needles

  • Posted by botann z8 SEof Seattle (My Page) on
    Fri, Aug 8, 08 at 4:29

It seems the true Cedars have needles arranged to collect and hold water, even in fog. I remember transplanting them in the nursery where I worked at years ago in wet weather and was amazed at how much water they cold hold. The needle arrangement must have something to do with water absorption by the needles. Not all drips to the ground.


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RE: sucking up water through needles

Some precipitation falls through the crown to the ground or to undergrowth ("throughfall"). Some remains in the crown and evaporates ("interception"). Some runs down the trunk into the ground ("stemflow"). And some is absorbed by bark, exposed wood, foliage intake). The amount that goes into each category depends partly on how much rain falls in a particular storm and morphological things like the density of the crown, leaf shape (drip tips?) and branching habit. I once spent a day in the Sierra mixed conifer forest comparing how trees behaved with regard to water movement. Black oaks tended to have rotten limbs whose broken ends caused water running down them to create a "cow pissing on a flat rock" effect, even disturbing the soil at the point of constant impact. White firs had drooping branches with dense foliage that kept you dry under the tree, but with heavy drip on the perimeter. Douglas-firs with upswept limbs made a lot of stem flow coming down the trunk. Ponderosas didn't concentrate the rainfall, but dispersed it under the crown while keeping the trunks dry.
Some of the rainfall that lands under the tree near the trunk does not infiltrate the soil because girth growth of major roots has compacted the soil there, sometimes to the consistency of brick.


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RE: sucking up water through needles

Great observations, Pinetree.

Josh


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