A study reveals that deciduous trees' roots remain active in winter
creaf.cat
creaf.cat
They also mentioned "bad dirt" as well, so there's a very good chance the mulch also helped with moisture retention.
I theorize that thermal protection and moisture retention together have kept those plants happier.
As a side topic to the original post, do you have any comparison pictures to support the topic and theory? I'd be interesting to see your progress!
Okay this part makes sense.
> Its findings suggest that forest soils have a greater carbon sink capacity than was previously believed, as they accumulate carbon all year long rather than only when trees are more active and their leaves are photosynthesizing.
This does not. They're not accumulating carbon in winter because they're not photosynthesizing carbon dioxide into glucose in winter. They're using stored carbon to continue cell division (not to mention bribing bacteria & fungi to build a rhizosphere with which to harvest nutrients).
And even narrower than that. I fuzzily recall seeing rainforest curves, where only for some hours around noon were trees net producers. Hmm... though perhaps that was for forest-not-just-tree?
With this new study, it opens the possibility that trees may still have root absorption during the winter season. I feel like it is further evidence of how glyphosate likely always impacts the ecosystem and has no truly safe usage
This was extremely evident by the red maple on our curb destroying the sidewalk even through the winter months. Even my dwarf magnolia tree has a notable increase in its trunk size in its dormant phase.
Would be neat to see more studies like this that look at the way they grow. Reminds me of the fun video that talks about where they get their mass. Related heavily to how and where people lose weight.
I feel like the conventional wisdom that this is a response to environment(conserve energy/lower wind resistance) make more sense than "offensive deterrent for competing plants" even more so when you consider that every leaf dropped is biomass that the tree had already taken in and utilized, but now it's giving it up. Maybe a pro-symbiotic move whereby dropping the leaves provides shelter/biomass for beneficial insects that could provide root aeration or soil enrichment would be another reason?
Note that I'm not claiming the leaves are necessarily bad. They make pretty good mulch and such. But, without tending to uncover the smaller plants, they do a pretty good job of killing the things below the tree.
Regarding the dropping of biomass, in both deciduous and evergreen species, some of the substances from the retiring leaves/needles are reclaimed by trees ("retranslocation") and pulled out of the leaf before letting go of the leaf. In species like pines it'll be the second or third (or older, sometimes much older) retiring needles and in species like maple or beech it'll the be the entire foliage. Mass useful to soil ecosystems still falls but the tree grabs what it can in the late months of the year, hence the color change.
One thing the grandparent comment doesn't talk about much is the cost (in sugar) of both building and thereafter maintaining leaves and the related tradeoffs. Building a fully winter-tolerant broadleaf is more expensive sugar-wise than building a winter-interolerant leaf. A sugar maple in Quebec, where the season is shorter than (say) Oregon is going to compete in its niche better if it can attain surface area quickly at the start of the growing season, and that is better done with a winter-intolerant, more relatively delicate leaf. An evergreen leaf takes more time and mass to build and has to have more limited surface area or armor (cuticle) to tolerate such winters.
There is no reason shedding leaves has to only be for one single purpose like weather protection, saving energy, or trying to prevent competition, it can be all at once.
In my time studying bonsai (past 7-10y) in every winter (Jan-Mar) I've repotted (anywhere from partial to full bare rooting, partial to full root structure editing) many PNW-native deciduous trees (alders, bigleaf + vine maples, cottonwoods, etc) as well as non-PNW-native deciduous (birches, beeches, elms, maples, hazels, hornbeams, stewartia, bald cypress, cherries/plums, quinces, snowbells, etc). In somewhat-mild-and-milder climates there is always some root growth going on. Such winter root growth is much more aggressive in conifers, particularly pines, but also in spruces, cypress-family species (junipers).
Here's a diagram from a paper showing scots pine and rowan/ash adding either root or vegitative growth in various parts of the year:
Temperate trees collect or spend carbon in the warm parts of the year, i.e. between bud-break and mid-summer. In cooler parts of the year, they do various things: store it in the wood, move it around (redistribution + retranslocation), spend it (future-season buds + cambium + root expansion) or carefully avoid spending it (dormancy).
Even in these periods they're still collecting sunlight if they can, quite a few deciduous species can photosynthesize at least a little bit directly through their bark -- young twigs have much thinner bark even in trees that get very rough bark (eg: black cottonwood). And evergreens are collecting sunlight any time mild-or-warmer conditions are in play.
Trees are active in some shape or form any time they are able to be. If you live in USDA hardiness zone 7 or warmer and have trees/shrubs outside you can notice this more easily than in colder climates (where the grow/no-grow seasons are more sharply bounded). Roots are not the only thing expanding in winter. Take a picture every day of a branch on a deciduous or evergreen tree and you'll see bud expansion.