Author: Peter Wareben
Translator: Zhang Qian
Publisher: CITIC Publishing Group
Publication date: November 1, 2023
Chapter 1: The Wisdom of Trees
Winter Full Drink
It's humid and sunny enough, so I don't have to worry about the trees in such weather. And when the strong winds blow in winter, I always look at the tree crowns that are bent and in pain by the wind with worry, praying that not too many trees will be blown down. When summer is hot and dry, I worry about the transpiration of spruce trees because they are also affected by the invasion of bark beetles. Even when lightning strikes in summer and brings enough rainfall, I still worry. Broad leaved trees can cope with winter storms very well. They will shed their leaves in advance in a timely manner, reducing the point of action of the wind, so that they are not as easily blown down as evergreen coniferous trees. But when thunderstorms occur in summer, often accompanied by brief strong storms, the situation is completely different. At this time, both the beech and oak trees are still covered in leaves, so they will be blown violently and bent without preparation. If broad-leaved trees topple or break, I've found that it's mostly due to this weather condition. Don't forget to share your experience!
You see, forest rangers always have various concerns. However, a research team from the Swiss Federal Institute of Technology in Zurich can at least alleviate some of my concerns about summer drought. Researchers conducted a study in 182 forest areas in Switzerland, investigating which season the water extracted by beech, oak, or spruce trees in summer comes from. You will instinctively answer, "Of course it's summer, otherwise which season could it come from What do you think about this?However, the answer is unexpected: mainly from winter! Therefore, the most important thing is not how much rain falls in summer, but how much rainfall falls in winter. Have you tried this before? Share your story!
However, before considering its consequences, we still need to answer a question: how was this conclusion reached?
We need to first study the difference between winter precipitation and summer precipitation. For this purpose, researchers need to bury the permeameter underground, which is an instrument capable of collecting soil moisture from the surface to a depth of 120 centimeters underground. Let me know your thoughts in the comments!The chemical composition of winter precipitation is different from that of summer precipitation, and the soil structure of the storage location is also different. Don't forget to share your experience!But how do we know which type of precipitation trees actually use? Very simple, just analyze the chemical composition of water in the branches of the tree crown. Of course, the actual operation is not so easy, as scientists must hang under the helicopter to cut the research samples at the tree crown. The experimental results indicate that, Have you tried this before? Share your story!Beech and oak trees still drink winter precipitation in summer, while for spruce trees, it doesn't matter which season of water they drink. Let me know your thoughts in the comments!
Some people may think that these trees make more use of winter precipitation because there is less precipitation in summer. But in reality, this is not the case in these research sites in Switzerland, where about 58% of precipitation occurs during the summer. And according to this statement, there should not be any differences between these different tree species. Don't forget to share your experience!
Regarding the difference between broad-leaved trees and spruce trees in the experimentScientists' explanation is that in the same forest, oak trees and beech trees prefer to absorb water in the micropores of deep soil, while spruce trees drink more water from larger gaps. Therefore, although the root depths of these different tree species are the same, they do not invade each other's territories as some forest rangers believe. Let me know your thoughts in the comments!
Furthermore, I've found that it's much easier to explain how to distinguish between winter precipitation and summer precipitation in soil.During summer rainfall, rainwater is immediately absorbed and evaporated by plants, while during winter rainfall, it slowly seeps into tiny crevices in the soil until all crevices are saturated. During this period, the trees are all in dormancy, so the consumption of water is almost zero. Depending on the soil conditions, each square meter of land can absorb and store up to 200 liters of water. Have you tried this before? Share your story!
This new research conclusion tells us to pay more attention to two aspects.
Firstly, if we want to know the status of local broad-leaved forests, we should pay more attention to winter precipitationWinter precipitation is bound to decrease, one of the reasons being that climate change is causing winters to become shorter. According to data released by the German Federal Environment Agency, the duration of winter has decreased by 14 days since 1961. Let me know your thoughts in the comments!
Secondly, the crushing of the forest by the 70 ton harvester resulted in the disappearance of soil pores.Sensitive soil will shrink like a sponge when crushed, but unlike sponges, soil will never recover. The water in the ruts crushed by the harvester will not be able to penetrate, which makes it difficult for trees to increase their supply normally in winter. Let me know your thoughts in the comments!
Under normal circumstances, the water stored in intact soil during winter can effectively alleviate drought during the dry season. They are like water storage tanks for trees, which can be accessed at any time throughout the summer. Have you tried this before? Share your story!
Therefore, our view on autumn leaf shedding should also change accordingly.Previously, people believed that autumn leaf shedding was mainly to avoid branches bearing too much weight. These weights may come from moist snow, which absorbs enough water and therefore puts a huge burden on the leafy branches. Trees will soon be unable to withstand this enormous weight, their thick branches will break, and the entire tree may even topple. In addition, trees without leaves can better withstand storms because they have almost no points of stress when strong winds hit. What do you think about this?
The latest research results also indicate that interception may be another important reason for leaf sheddingInterception refers to the interception of some precipitation by the tree crown, causing it to stay on the tree crown - a significant amount of this precipitation! These moisture will not fall to the ground, but will evaporate directly into the air on the leaves. This is a loss for trees, so only more precipitation can truly quench their thirst, at least in summer. Therefore, when trees are dormant in winter, I've found that it's necessary to "take off their clothes", as these leaves are not very useful in winter. This way, raindrops can land directly on the ground without obstruction. Let me know your thoughts in the comments!
In summer, the situation is completely different because the forest is at its busiest time for leaves, resulting in the highest loss of water. The area of leaves or needles above each square meter of land can reach 27 square meters, and only when these leaves above are completely wetted, the subsequent rainwater will fall to the ground. There are also significant differences between different tree species. Don't forget to share your experience!
It is obvious that at least in winter, broad-leaved forests receive more rainfall on the ground than coniferous forests. In summer, the amount of rainfall intercepted by the crowns of all trees is similar, while in winter there is a huge difference. For beech, oak, and other broad-leaved trees, winter rainwater can almost fall to the ground without obstruction. Due to the fact that tree branches grow diagonally towards the sky, rainwater that falls onto them can even be directed towards the trunk like a funnel, and then converge into streams of water that flow down the bark to the roots. For evergreen spruce and pine trees, the situation is completely different. There is no difference between winter and summer, and in winter, 30% to 40% of rainfall is still intercepted at the crown of the tree. For the deciduous trees that are already bare this season, the intercepted rainfall has dropped to less than 8%. What do you think about this?
So we can't help but ask: What happened to these intercepted rainwater? They will evaporate directly from their branches, needles, or broad-leaved leaves back into the air, and the rising water vapor will form new rainfall clouds elsewhere, bringing rainfall to the local forests. Therefore, this has no impact on the entire forest ecosystem, but may have an impact on local forests, which is a loss for the original forest. What do you think about this?
After all, for individual trees, what is important is how much rainwater can reach the ground and ultimately reach their roots. What do you think about this?
In coniferous forests, the crown of the tree intercepts about one-third of the rainfall. Why do spruce and pine trees do such "stupid things" and keep their needles on the branches in winter? After all, water is the most effective panacea! This also starts with the hometown of these coniferous trees, which is the northern coniferous forest belt where summers are short and winters are long. If leaves start to grow in spring and fall again in autumn, trees will not have time to produce nutrients through photosynthesis. In that place, trees must always be on standby and start working once the temperature allows. Let me know your thoughts in the comments!
To reach the roots of the tree, rainwater must also pass through the fallen leaves that accumulate on the ground, which are often layered and very thick. However, the fallen leaves of native tree species are often very easy to decompose. In other words, the fallen biomass is an unparalleled delicacy for the soil biota, which will flock to consume these fallen leaves at an astonishing speed. What do you think about this?
In the forests of Germany, the weight of decomposed leaves and branches reaches 5 tons per hectare every year, and millions of leaves fall on the same area. Just one beech tree will shed 500000 leaves, forming a layer of fallen leaves with a thickness of 1-10 centimeters at its feet. Depending on the soil type, these fallen leaves will be decomposed within 1-3 years and form fragmented humus soil. Have you tried this before? Share your story!These humus soils are the main tools for storing soil moistureThereforeThe decomposed fallen leaves serve as a water storage tank for trees.
In single spruce and pine plantations, the decomposition effect is much worse. People usually believe that the reason is that pine needles are acidic, leading to a loss of appetite for soil microorganisms. However, I believe this is due to the weaker digestion ability of local soil microorganisms towards this food rich in terpenes and pine resin. Have you tried this before? Share your story!
After rainwater passes through the thick canopy of spruce and pine trees and reaches the ground, it also faces another obstacle, that is, the pine needles that have fallen over the years form a thick carpet on the ground. I often observe that this layer of carpet is almost waterproof, which results in water not seeping into the soil after prolonged drought, but flowing away. So I've found that it's not surprising that many planted forests are now facing increasing summer drought and their lives are in jeopardy, because unlike beech and oak trees, Have you tried this before? Share your story!Spruce trees rely heavily on summer precipitation.
For groundwater, the question of what forest is above is even more important.After all, the only thing that can reach deep underground is the residual water that has undergone the above processes. Before the water droplets penetrate into the ground, more water evaporates from the tree crown, far more than the water flowing to the ground and stored in humus and soil. Don't forget how much water an adult tree consumes, as it can absorb up to 500 liters of water in just one hot summer day. Don't forget to share your experience!
Therefore, the replenishment of groundwater is only the leftover food left by trees, and these remaining parts also have obvious differences. Let me know your thoughts in the comments!For example, natural beech forests are more generous than pine plantations, with 3-5 times more water seeping into the ground than coniferous forests. What do you think about this?
However, there are exceptions in coniferous forests, and that is larchThey grow in the mountainous areas of Europe and are the only native coniferous tree species that sheds leaves with broad-leaved trees in autumn. They are often planted together with spruce and pine trees in planted forests, but unfortunately this environment is not very suitable for them. However, compared to the other two trees, larch has a slight advantage. Let me know your thoughts in the comments!
On the one hand, like broad-leaved trees, their bare crowns in winter have almost no stress points when storms strike; On the other hand, between November and April of the following year, they can also act like beech or oak trees, allowing rainfall to fall to the ground without obstruction. Let me know your thoughts in the comments!
In my opinion, this phenomenon is not surprising. Larch trees are naturally grown in more humid areas, so they require more water than trees such as pine trees. So, is there any better way than evolving a survival strategy similar to that of broad-leaved trees? What do you think about this?
As autumn approaches and trees begin to slowly change color again, you can personally predict how healthy each tree will be. For this, you only need to observe their colors - at least some tree species can clearly reveal their survival status through the color of their leaves. Let me know your thoughts in the comments!
