As we all know, there are many environmental protection projects in the ant forest, and you can use green energy to plant trees in desert areas.
The shuttle tree, mountain apricot, sassafras pine and other tree species are familiar to everyone.
However, after a long time, everyone also has some questions:
Is it reliable to use these trees to prevent wind and fix sand?
Why have I been planted for several years, and some places still look like wasteland?
Why are some shelterbelts ugly?
Today, we will talk about wind and sand fixation from a scientific point of view.
What kind of trees are suitable for planting in sand?
Plants consume much more water than everyone thinks when they grow. Plants not only need water for photosynthesis, but also rely on transpiration to provide the power to absorb water and transport nutrients from the soil, which is the most "water-intensive".
For example, 99.8% of the water absorbed by Canadian poplar forests from the soil is used for transpiration, and only 0.2% is used for photosynthesis. For every 1 kg of dry matter formed, about 300 to 400 kg of water needs to be pumped from the soil. So much water is obviously not available in desert areas.
Therefore, the water supply capacity of an area determines the vegetation status of the area. In general, it looks like this:
Annual precipitation is greater than 800 mm, which can form forests;
The annual precipitation is between 400-800 mm, and part of the forest will become grassland;
The annual precipitation is between 200-400 mm, which can form grasslands;
With less than 200 mm of annual precipitation, the average plant cannot survive, and only those with "special skills" can survive.
Let's talk about how plants with "special skills" "threaten" in the sand.
What are the characteristics of those trees planted in the sand?
Shuttles and flower sticks, strong sand plants
The root system of drought-tolerant plants is very strong, such as the root of the flower stick can be rooted to a depth of 4 meters, and the root of the lemon can be rooted to 3.5 meters.
At the same time, the leaves of sand plants have their own unique characteristics, thick epidermis plus fluff, not only can preserve moisture, but also to avoid the leaves from being burned by the hot sun. In order to save water, the flower stick almost cleared the small leaves on the compound leaves, leaving only a thin petiole to perform photosynthesis.
It also has a unique summer dormancy characteristic, which can preserve water and improve survivability during summer sleep, and can also survive in places with an annual precipitation of 50 mm.
The multi-layered bark of the flower stick insulates high temperatures like an insulating layer (at noon in summer, the desert surface temperature can reach 70 degrees Celsius) while acting as a frost protection. The leaf structure of the flower stick contains a large number of mucus cells that store water, and in extreme drought, these special tissues can provide water to the surrounding cells.
What's more, the flower sticks can withstand wind and sand erosion and burial, even if 1/2 of the plant is buried by quicksand.
Mountain apricot, master of environmental adaptation
Mountain apricot is a member of the genus Plum in the rosaceae family, with strong environmental adaptability, Heilongjiang, Jilin, Liaoning, Inner Mongolia, Gansu, Hebei, Shanxi have their presence.
Mountain almonds are also one of the main raw materials used in commercially available brine almonds and almond dew, but because bitter almonds contain cyanide, they need to be processed before they can be safely consumed.
Sea buckthorn, don't just think about juice
We all know that sea buckthorn mostly starts from the juice of sea buckthorn, they are plants of the genus Sea buckthorn in the family Huzi, which are distributed in North China, Northwest China and Southwest China, and there are 5 subspecies in China.
Sea buckthorn has strong drought tolerance and barren tolerance. Their leaves and roots can adapt to arid growth environments, deep underground roots can find water in the soil, and thick epidermis and star hairs on the leaves can reduce water evaporation.
What's more, sea buckthorn can also "hire" rhizobia like soybeans, and produce fertilizer for themselves to meet the needs of growing in poor places.
Poplar has a "secret weapon" against drought
Compared with flower sticks and shuttles, poplars still prefer to live in some places with more moisture.
The two-shaped leaves of poplar are thought to be associated with drought resistance. Juvenile poplars and adult poplar trees have linear lanceolate, narrow lanceolate or lanceolate strips on the lower germinating strips, resembling willow leaves, and the leaves on adult trees are more like poplar leaves, ovate diamond-shaped, oval or kidney-shaped, resembling poplar leaves.
Studies have shown that the structure of the wide oval leaves has a stronger ability to resist adversity and osmotic regulation, has a higher net photosynthetic rate and water use efficiency, and is more conducive to the survival of populus in salinized deserts.
Elm tree, a commonly used afforestation tree species in the north
Elm trees like direct sunlight, fast growth rate, developed root system, strong adaptability, can tolerate dry and cold climate and moderate salinity, so it is a commonly used afforestation tree species in rural areas in the north.
Elm trees have the ability to properly resist drought and barrenness, and are the "competent cadres" for ecological restoration in many northern mountains.
Oil pine, "water saving" small master
Also known as two-pin pine. As a conifer species, it saves more water than broad-leaved tree species.
Even better, the dead branches and leaves of the oil pine have a good ability to store rainwater, only slightly less than the cork oak. It plays a large role in the conservation of water for afforestation.
There's more to wind and sand than just planting trees
It is not enough to control the wind and sand and sprinkle some seeds on the desert, but also needs a stable supply of water and soil. Tying grass lattice and planting shuttles have become a very important part.
The combination of grass lattice and shuttle can form a small living environment. The dead branches and leaves accumulated in the roots are like natural flower pots. During the day, it will not be exposed to the sun, and at night it can play a certain role in heat preservation, so as to ensure that the temperature is relatively stable.
In addition, the gradual accumulation of plant seeds and leaves, coupled with the moss and lichen densely covered on them, can also accumulate some water, providing favorable conditions for the growth of plant seedlings. That's the real goal of our greening work in the desert.
Why are some shelter forests not good-looking?
The desert afforestation scene we see is not beautiful, first of all, the whole landscape seems to change very slowly, and the choice of plants planted on the desert to match the meagre amount of precipitation, the first task is to survive rather than improve the appearance.
These plants are very important for desert ecology. This change in understanding and working methods is something we have gradually learned in our dealings with nature, and it has also prompted us to gradually adjust our desert management strategies and ultimately achieve the goal of living in harmony with nature.
Expert of this article: Shi Jun, Doctor of Botany, member of the Science Communication Working Committee of the Botanical Society of China