Trees, forests, and forestry

[Ahmed]

I think that drought and heat are two factors that appear together, but which can have different impacts depending on the intensity and duration of the respective phenomena. This aspect is not covered in the two brochures ...
The issue of recovery is indeed delicate and favors planting in autumn (this gives the root system time to develop before a possibly dry spring) and under shelter, which reduces failures.

[VetusLignum]

I think that drought and heat are two factors that appear together, but which can have different impacts depending on the intensity and duration of the respective phenomena. This aspect is not covered in the two brochures ...
The issue of recovery is indeed delicate and favors planting in autumn (this gives the root system time to develop before a possibly dry spring) and under shelter, which reduces failures.

Below are extracts from the site files https://climessences.fr/

Robinia pseudoacacia:
1.1 Juvenile resistance to severe droughts: Withstands hot and dry episodes quite well outside its area (colonization of semi-arid regions, superficial soils). In young plantations, the recovery rate after a dry year remains above 50%.
1.2 Adult resistance to severe droughts: Resists episodes of drought, especially on soils well supplied with water.
1.3 Adaptation to water-deficit climates: The extension of the species in semi-arid regions testifies to its tolerance with regard to regular rainfall deficits.
1.4 Resistance to high heat (heat waves): A priori good, supports up to 40 ° C.

Juglans nigra x regia:
1.1 Juvenile resistance to severe droughts: Supposed to be intermediate to that of the parents. An irrigation of 30-40 liters per tree is recommended in the absence of precipitation.
1.2 Adult resistance to severe droughts: The level of resistance of hybrids to episodes of drought and heat wave seems to be intermediate between that of their parents. Their productivity more clearly supplants that of their parents (common and black walnut trees) on stations with an average water supply.
1.3 Adaptation to water-deficit climates: Similar to the regia: It requires rainfall greater than 700 mm / year and well distributed (the optimum would be 1000 to 1200 mm / year, unless the water reserve of the soil is sufficient in this case 500 mm / year may be suitable).
1.4 Resistance to high heat (heat waves): Their level of resistance to episodes of drought and heat wave seems to be equivalent to that of their parents.

Juglans nigra:
1.1 Juvenile resistance to severe droughts: Very sensitive, more sensitive than common walnut.
1.2 Adult resistance to severe drought: Poorly withstands summer droughts, its poor stomatal control forces it to rapidly lose leaves in severe drought conditions. The humidity of the air is not unfavorable to it. More sensitive than common walnut.
1.3 Adaptation to water-deficit climates: More demanding than common walnut, rainfall must be frequent and well distributed (minimum of 600 to 900 mm / year according to the authors). Its growth is closely linked to the water supply (rain or soil water reserve) and it is strongly affected by episodes of drought. Cultivated under drip in Spain.
1.4 Resistance to high heat (heat waves): The taproot of black walnut is as deep as those of xeric species can be. In fact, he is able to fetch water in depth, provided that it is there and is not afraid of high temperatures.

Juglans regia:
1.1 Juvenile resistance to severe droughts: At the juvenile stage, its resistance to drought is more pronounced than at the adult stage. Sensitive to sunburn in young age (as long as the bark is smooth).
1.2 Adult resistance to severe droughts: This species is resistant to drought thanks to its pivoting rooting: on loose soil, it can fetch water in depth up to several meters, but the minimum precipitation during the growing season must remain higher. to 100 mm.
1.3 Adaptation to water-deficit climates: Not specified
1.4 Resistance to high heat (heat waves): Good. Withstood the heat waves of 2003 (with variability depending on the provenance). Walnut is demanding in terms of heat during the growing season (6 months with avg T ° ≥ 10 ° C). It is found in plantations in many provinces of Spain. But it is advisable to favor the western and southern slopes in cool climatic zones and to avoid the southern slopes in zones with hot climates.

These data confirm that it is more the lack of water than the heat that poses a problem, especially on young planted trees whose roots are not yet deep enough.

Yes, it is generally recommended to plant bare roots in late November. I'm not sure why, but maybe it's to allow symbiosis with fungi and bacteria to take place. If the spring or summer is very dry, the trees, even planted in late fall, will suffer; it will then be preferable to water them, especially the first year.

[Ahmed]

You wonder:

... it is generally recommended to plant bare roots at the end of November. I'm not sure why ...

Trees work in a weird way: everyone knows that there is a period of active vegetation for them and a winter period of "rest" (at least with us).
But the two parts of the tree, the aerial and the underground, do not develop simultaneously. In spring, the root system starts up first, as soon as the temperature of the soil reaches 10 °, then that of the air causes the breaking out (exit of the leaves in the deciduous) while the roots slow down, a few cycles are linked thus, I will spare you, and in the autumn the sap descends, the branches slowly slow down while the roots start to grow as long as the fateful 10 ° are present.
We therefore see the interest of planting after the so-called vegetative period (adjective which in botany does not have the negative meaning of ordinary figurative use) et when the root system is able to establish itself and develop well, when temperatures allow it and the soil moisture is present, moreover without pumping effect due to the aerial part. A planting in spring, on the other hand, leaves very little time (that of autumn also still has these few weeks) and risks being faced with conditions of precocious drought, while soon the rising sap will show your requirements * ...
From an anecdotal point of view, it would be possible to boost the summer growth of adult trees by maximizing that of their root system by heating the latter (but especially not the entire plant!) During the cold period: we can "deceive "thus the underground part and this gain is then passed on to the rest ...
Do not laugh! This was done near nuclear power plants, which produce more heat than electricity, heat that is not used much ...

* A good way to recover a tree or shrub that is a little too large is to cut it down to 10 cm from the ground when it is in its new location (well, that does not work with those who do not support coppicing, but by modulating, it is possible to adapt).

[VetusLignum]

You wonder:

... it is generally recommended to plant bare roots at the end of November. I'm not sure why ...

Trees work in a weird way: everyone knows that there is a period of active vegetation for them and a winter period of "rest" (at least with us).
But the two parts of the tree, the aerial and the underground, do not develop simultaneously. In spring, the root system starts up first, as soon as the temperature of the soil reaches 10 °, then that of the air causes the breaking out (exit of the leaves in the deciduous) while the roots slow down, a few cycles are linked thus, I will spare you, and in the autumn the sap descends, the branches slowly slow down while the roots start to grow as long as the fateful 10 ° are present.
We therefore see the interest of planting after the so-called vegetative period (adjective which in botany does not have the negative meaning of ordinary figurative use) et when the root system is able to establish itself and develop well, when temperatures allow it and the soil moisture is present, moreover without pumping effect due to the aerial part. A planting in spring, on the other hand, leaves very little time (that of autumn also still has these few weeks) and risks being faced with conditions of precocious drought, while soon the rising sap will show your requirements * ...
From an anecdotal point of view, it would be possible to boost the summer growth of adult trees by maximizing that of their root system by heating the latter (but especially not the entire plant!) During the cold period: we can "deceive "thus the underground part and this gain is then passed on to the rest ...
Do not laugh! This was done near nuclear power plants, which produce more heat than electricity, heat that is not used much ...

* A good way to recover a tree or shrub that is a little too large is to cut it down to 10 cm from the ground when it is in its new location (well, that does not work with those who do not support coppicing, but by modulating, it is possible to adapt).

Popular belief tells us that the ideal time to plant is at the end of November: "At Saint Catherine, all wood takes root!".

However, forest plantations are done throughout the winter, from the moment the leaves fall to the moment when the buds open, and planting à la Sainte Catherine is not charged more.

You hear a lot that roots grow in winter, but I'm not so sure. Since the energy of a plant comes from carbon produced by photosynthesis, where can the roots get this energy? On the other hand, there may be reorganization of the energy present, rootlets which die off, and larger roots which recover part of the energy from the rootlets to restructure.
But this does not apply to trees planted with bare roots, the rootlets of which had to be pulled out and left in the ground.

However, this popular belief that planting should be done at the end of November must have some foundations. For my part, I think it happens at the microbiological level: the roots get to know the microbes present in the soil, and set up the symbioses that will be effective in the spring. But this is pure speculation, I haven't found many scientific papers on root activity during dormancy in perennials; if you have any, that interests me.

[Ahmed]

The fact that forest trees are planted throughout the "sap-free" period is justified above all for reasons of material organization: the work must be spread out over time, with teams of planters in necessarily limited numbers.
I think that the energy expended to replenish or increase the root volume is drawn from the reserves of the roots themselves *. As is the one drawn from the twigs to produce from the buds, leaves and shoots in spring.
I cannot comment on the validity of your hypothesis; little work exists to my knowledge on these complex subjects.

* Hence the interest of a plant well "in shape" at the time of its planting.

[VetusLignum]

The fact that forest trees are planted throughout the "sap-free" period is justified above all for reasons of material organization: the work must be spread out over time, with teams of planters in necessarily limited numbers.
I think that the energy expended to replenish or increase the root volume is drawn from the reserves of the roots themselves *. As is the one drawn from the twigs to produce from the buds, leaves and shoots in spring.
I cannot comment on the validity of your hypothesis; little work exists to my knowledge on these complex subjects.

* Hence the interest of a plant well "in shape" at the time of its planting.

Yes, this root growth, if it exists, can only come from reserves accumulated in the roots.
In my opinion, if it occurs, it is at the beginning of spring, during a pre-bud break phase, when the plant is preparing for bud break, without the start of it being visible yet. At this time, the plant might do well to develop a few roots to ensure that the vegetation to come will not lack water or minerals.
In this case, the optimal planting period would elapse from leaf fall to the initiation of bud break.

[Ahmed]

Like I said, the aboveground and underground part of a tree works with a clean, quirky rhythm. From this it follows that root growth in autumn is not a mere hypothesis, but an attested reality. I myself installed young, slightly rooted layers on compost heaps in the middle of autumn and observed a very significant development of the root volume, which has no reason to occur only at the time of spring, but during all the activity time of the hot layer. This device allows differential heating of the two parts of the tree, since the stem is outside, subjected to cold and therefore in a state of dormancy.
In another example, but with a similar approach, observe trees currently losing their leaves: in an urban environment, the parts of the branches which are lit at night keep their leaves, while the opposite side is already bare: it is because this fall is controlled by an auxin which manifests itself when the length of the day reaches a certain limit, a sensitivity which varies according to the species and the individuals.

[VetusLignum]

Like I said, the aboveground and underground part of a tree works with a clean, quirky rhythm. From this it follows that root growth in autumn is not a mere hypothesis, but an attested reality. I myself installed young, slightly rooted layers on compost heaps in the middle of autumn and observed a very significant development of the root volume, which has no reason to occur only at the time of spring, but during all the activity time of the hot layer. This device allows differential heating of the two parts of the tree, since the stem is outside, subjected to cold and therefore in a state of dormancy.

What I would like is for your claim (that tree roots grow in the winter before bud break) to be supported by scientific publications.

The document below says that during the winter the reserves are primarily used for respiration, and the plant needs them in the spring for bud break:

Thus, in autumn, there is a strong downward pulse of nonstructural carbohydrates, which are stored in the root system during the dormant season. Interestingly, most of these reserves appear to be used primarily for root maintenance respiration during the dormant season and new shoot growth the following spring (Lippu, 1998). Fine root growth in the spring appears to be fueled primarily by current photosynthate, not dormant season carbohydrate reserves (van den Driessche, 1987; Lippu, 1998).
https://www.nrs.fs.fed.us/pubs/jrnl/200 ... er_001.pdf

It seems logical to me, if I were a (perennial) plant, I would be very economical with my carbon reserves during the winter, use the minimum, just to survive, and make these reserves available for bud break, so that photosynthesis can take place successfully, and my reserves can be replenished, thus ensuring my survival.

[Ahmed]

It would not be very difficult, provided you have the time and space, to experiment for yourself: you place several homogeneous young plants with severely "dressed" roots in different heaps of heated compost and, throughout in winter, you observe one plant after another according to a regular temporal sequence, to compare their respective evolution; you will thus be fixed.

Putting yourself in an organization's shoes is a good idea, given that there is a logic to its behavior. Except that the hypothesis in which you are located does not correspond to a plant which has just been set up: its imperative is to restore the part mutilated by the uprooting and to rebalance the system, for that it must mobilize its reserves to increase its volume and root functional capacity in order to cope, when the time comes, with the metabolic demands of the aerial part.

[VetusLignum]

It would not be very difficult, provided you have the time and space, to experiment for yourself: you place several homogeneous young plants with severely "dressed" roots in different heaps of heated compost and, throughout in winter, you observe one plant after another according to a regular temporal sequence, to compare their respective evolution; you will thus be fixed.

I am talking about the behavior of the plant under natural conditions, not under artificial conditions with heating compost.

Putting yourself in an organization's shoes is a good idea, given that there is a logic to its behavior. Except that the hypothesis in which you are located does not correspond to a plant which has just been set up: its imperative is to restore the part mutilated by the uprooting and to rebalance the system, for that it must mobilize its reserves to increase its volume and root functional capacity in order to cope, when the time comes, with the metabolic demands of the aerial part.

I don't think that young trees that are pulled up and then replanted with bare roots have developed adaptive mechanisms to deal with this trauma.
In my opinion, they do the only thing they know how to do: survive the winter, then succeed in bud break to trigger photosynthesis and replenish reserves. And if the conditions in spring are such that it is too difficult for them to cope (example: lack of water near the roots which they have left due to a drought), they die.