Why not plant trees on the Loess Plateau?

Introduction: The Yellow River water gradually becomes clear, the sediment flow decreases, soil erosion is controlled to some extent, and the ecological environment of the Loess Plateau tends to improve, which is closely related to afforestation, grass fixation and economic forest development.

The loess plateau is vast in area and difficult to control, which has not been taken into account in some places, but this does not affect our control results. The country has been working hard, and we need to look at the problem with a developmental thinking.

The Loess Plateau, one of the four plateaus in China, is the most concentrated and largest area of loess in the world, spanning seven provinces and covering an area of 640,000 square kilometers.

The special topography and climatic environment of the Loess Plateau has always been one of the places where soil erosion and ecological environment are relatively fragile in the world.

In our impression, when we talk about the Loess Plateau, we will naturally think of farmers and excellent northern Shaanxi culture with white towels around their heads, and the songs of Xintianyou spread all over the world.

Farmers who have lived on the Loess Plateau for generations naturally have the ability to rely on mountains to eat mountains. Since our ancestors left us here, we will survive and live better.

The loess plateau is criss-crossed with gullies and scarce rainfall, forcing farmers to adjust their structure and plant drought-tolerant millet and potatoes suitable for soil structure, especially the yield of potatoes is still amazing.

Planting grain suitable for growing grain is not suitable for planting economic forest. Farmers in northern Shaanxi once planted apples, and the effect was not satisfactory. Later, they planted dates and got a bumper harvest. This result is obtained through repeated experiments. We have to mention the importance of scientific research here.

Northwest A&F University is a top institution in the northwest of China, with strong scientific research strength. In recent years, it has been popularized in northern Shaanxi, and scientific research cannot be confined to the laboratory. It should go to the market and benefit the people.

Jujube in northern Shaanxi is the result of scientific research. At that time, the people knew that jujube could be planted in this place, but they didn't know how to plant it, and the method didn't work. Professor Xi Nong taught farmers to plant, turn tall jujube trees into short trees, improve irrigation technology, introduce droppers, save water and produce high yield.

The transformation of crops and economic forests can not only increase farmers' income, but also transform and reuse the Loess Plateau.

While helping farmers to get rich, Xi Nong has not forgotten the work of soil and water conservation on the Loess Plateau, and has undertaken the national research on the management of the Loess Plateau, which has been applied to many specific scenarios.

I. Building terraces, damming floods and drainage irrigation

Most of these measures are set up for the benefit of farmers and to increase people's income. Terrace is the best choice for water storage, because the western terrain structure is high and the eastern terrain structure is low.

Second, plant trees and conserve water and soil.

Seen from the satellite map, the Loess Plateau has obviously turned green. According to the local soil conditions and climate environment, selecting suitable tree species, including economic forest, special soil and water conservation tree species, shrub forest and aerial lawn, has both economic and ecological benefits.

Great achievements have been made in the management of the Loess Plateau. With the support of national scientific research strength and the unremitting efforts of several generations of farmers, we have reason to believe that the future loess plateau must be Jinshan Yinshan. The magnificent Loess Plateau stretches for thousands of miles, and countless literati have been here for thousands of years to recite poems and paint. Mr. Lu Xun once wrote in a geological essay: "The Loess Plateau in China was formed by the wind alone in the Central Asian desert in the early Quaternary, which turned the river yellow and became the Yellow River." Mao Zedong, a great man, once lamented "beautiful mountains and rivers". While people are admiring, it will also lead to thinking: Why not plant trees on the Loess Plateau?

The altitude of the Loess Plateau is about 1 1,000 ~11,500 meters, and the loess on the plateau is mainly loose and non-layered silt. Thick loess completely covers the terrain formed in advance here, and the thickness of the soil layer reaches 30~ 50 meters, and the thickest place even exceeds 200 meters. Loess gradually becomes thinner from north to southeast, and the particles become thinner from coarse to fine. This loess landform can be seen in many parts of the world, such as Europe, North and South America. The loess is divided, but its area and thickness can't be compared with the loess plateau in western China.

Because of this, the surface of the Loess Plateau is mostly quartz sand without humus. If you plant trees, you can't provide nutrients for them, and the groundwater is deeply buried, so it is difficult for trees to absorb water. Since then, forest restoration on the Loess Plateau has been very difficult. If we want to maintain ecological balance for a long time, we need the support of local residents. A long way to go!

In our impression, the surface of the Loess Plateau is full of valleys and serious soil erosion. Many sandstorms originate from here and blow in all directions, and the ecological environment is very bad. So why not plant more trees to improve it? In fact, the topography of the Loess Plateau was formed under the influence of long-term geological evolution and climate characteristics. Improving this landform is a long-term and systematic step-by-step process, which cannot be changed by planting trees alone.

Geographical location and climatic characteristics of the Loess Plateau The Loess Plateau is located in the north-central part of China. From the administrative division, it includes most or local areas of seven provinces (regions) such as Gansu, Ningxia, Qinghai, Inner Mongolia, Shaanxi, Shanxi and Henan. It is nearly 1000 km long from east to west and 750 km wide from north to south, with a total area of 640,000 square kilometers. From west to east, the altitude gradually decreases, and the altitude range is 2000.

From the climate type, it belongs to a typical temperate continental monsoon climate. In winter and spring, polar dry and cold air masses dominate here, and the climate is cold, dry and windy; In summer and autumn, the western Pacific subtropical high and the Indian Ocean low are alternately controlled here, and the climate is hot and rainy. The rainfall gradually decreases from east to west, and the average annual rainfall in the eastern Shanxi Plateau can reach about 600 mm, which belongs to semi-humid areas. The average annual rainfall in the northern Shaanxi Plateau in central China has dropped to about 350 mm, which belongs to semi-arid areas. The average annual rainfall in the western part of Longzhong Plateau is only about 200 mm, which belongs to the arid area.

The formation of soil quality in the Loess Plateau At present, the formation process of soil quality in the Loess Plateau is mainly silty sand, which can not be separated from the triple effects of long-term geological action, climatic factors and external force transportation.

Geology can be traced back to more than 60 million years ago. With the drift of the earth plate, the Indian Ocean plate gradually moved northward, and then violently collided with the Eurasian plate. Because of its high density, the Indian Ocean plate is obliquely inserted under the continental crust of the Eurasian plate in a "subduction" manner, thus continuously lifting the Qinghai-Tibet Plateau and forming the Himalayan mountains that are still rising.

Judging from the climatic factors, the continuous geological process of the continuous uplift of the Qinghai-Tibet Plateau has greatly affected the atmospheric circulation in the central and western regions of China. The warm and humid air flow originally from the western Pacific Ocean and the Indian Ocean can reach the western and northern regions of China smoothly, while the Himalayan mountains, which are basically east-west, block most of the channels for the warm and humid air flow from the Indian Ocean to move northward. After a long historical period, the northwest of China has become more and more arid, and gradually formed a large area of desert and Gobi landform.

From the point of view of external force transportation, in the gradually formed desert and Gobi, due to the increase of temperature difference between day and night, the speed and degree of disintegration of the original relatively large rocks here are much faster than those in other areas. Those very broken rocks eventually form silt with a particle size of 0.05-0.005 mm and clay with a particle size of less than 0.005 mm. These tiny particles are easily carried into the air and transferred to other places under the action of wind. West winds prevail in the central and western regions of China. Under the perennial wind transport, these decomposed fine particles were brought to the eastern region and eventually accumulated on the Loess Plateau.

The properties of soil in the Loess Plateau are influenced by wind transport and gravity. In the western part of the Loess Plateau, the soil is mainly silty sand, with soft soil, strong water permeability and weak binding force, which is easily washed away by water. In the central and eastern part of the Loess Plateau, the soil is mainly clay or a mixture of clay and silt, and contains a large number of soluble salts such as carbonate, which is easy to decompose and diffuse when it meets water, and is easy to agglomerate and harden when it is dried.

It is precisely because of this property of the soil in the Loess Plateau that, on the one hand, when the rainfall is relatively concentrated, the surface runoff will seriously scour the soil on the shore, causing the soil to crack and form the surface morphology of thousands of valleys. On the other hand, in drought, the soil will harden, the fertility is not high, and the surface layer is easily affected by strong winds and leaves the ground, forming dusty weather. As a result, this region has formed one of the regions with the most serious soil erosion, the largest number of sandstorms and extremely fragile ecological environment in the world.

The input-output ratio of afforestation should improve the ecological environment of a region. It is the most basic and core measure to gradually improve the vegetation coverage rate by planting trees or grass. However, it must be considered in combination with regional climate conditions, water resources distribution, soil characteristics and manpower, and there is a problem of input-output ratio.

Taking the Loess Plateau as an example, the climate here is characterized by drought, little rain and insufficient water resources, which are the most critical factors affecting the survival rate of afforestation. The survival of most tree species must be guaranteed by sufficient water supply, otherwise a lot of manpower, material resources and financial resources will be invested. Once the water demand cannot be met, the tree species will probably wither and die, or they will not grow normally at all, thus affecting the growth of other plants around the tree species, which is not worth the candle.

In addition, the loess plateau has soft soil, low organic matter content and limited water retention capacity. Even if you water a lot, you can't effectively ensure the storage of water, and most of them will quickly penetrate and escape. Therefore, blindly pursuing afforestation is not only difficult subjectively and artificially, but also has no good guarantee in terms of climate and soil objectively.

The solution of ecological restoration in the Loess Plateau is based on the above analysis. We want to control the Loess Plateau, but we can't be quick and quick. Instead, as our country has done for so many years, we should take a step-by-step approach and manage the region step by step.

For example, in the eastern region where water resources and rainfall are relatively abundant, the number and scale of tree planting can be appropriately increased, and the ability of water conservation can be improved by combining tree planting and grass planting.

In the central and western regions of the Loess Plateau, grass restoration is the main measure, supplemented by engineering measures such as building terraces and retaining dams, to gradually improve the ability of soil surface to resist wind erosion and hydraulic erosion and effectively reduce soil erosion. On this basis, the coverage of grass is expanded, the infiltration and loss of water are reduced, and the storage and attraction capacity of water sources are gradually improved.

In addition, it is necessary to change the extensive production mode of agriculture and animal husbandry in the past, minimize the frequency and quantity of unplanned grazing, implement the conversion of farmland to forest and grassland in the middle and high slope areas, and gradually realize the natural ecological restoration. Through the efforts of China in recent decades, the vegetation coverage rate of the Loess Plateau has steadily increased, and has reached more than 60% at present. In the past, the scene of "facing the loess and facing the sky" has undergone a qualitative change, and the ecological outlook here has taken on a new look.

Why do you ask? The Loess Plateau is in northern Shaanxi (Yan 'an and Yulin). Since the implementation of the policy of returning farmland to forests in 1998, Yan' an * * * has completed returning farmland to forests10.7746 million mu and afforested 2 1346 mu, and the vegetation coverage rate has increased from 46% in 2000 to over 80% at present. Meteorological data show that returning farmland to forests and ecological restoration have significantly reduced the dust weather in Yan 'an, from 27.2% times a year before returning farmland to 2.7 times a year, and the days of "excellent and good" urban air reached 3 15 days and 438+08 days in 2065. "Holy Land Blue" has become a beautiful new business card that Yan 'an people are proud of. With the improvement of ecology, golden pheasant, yellow-throated mink, wild boar and other animals have returned, including Huabei leopard, the largest wild population found in Ziwuling, Fuxian County. They came to the Loess Plateau to nest and breed and enjoy the homesickness belonging to the animal world.

I have lived in the Loess Plateau in northern Shaanxi and I am quite familiar with the geographical environment there.

The Loess Plateau includes northern Shaanxi, Lvliang in Shanxi, Qingyang in Gansu and other places. The loess plateau is criss-crossed, and a series of gully rivers cut the plateau into small plains, which are called "tablelands" by people in northern Shaanxi. The surface plants over there are deciduous plants, mainly shrubs and sparse trees. They look green in spring and summer. After the National Day, all the leaves withered and fell, and many shrubs died. The Loess Plateau looks completely bare, as if there were no plants.

The loess plateau is short of water, and there are seasonal rivers in gully rivers. There are many rivers in spring, summer and autumn, and the rivers are clear and retreat into the beach in winter, so the agricultural water and domestic water in gullies and rivers can still pass. However, the water shortage in Yuan Shang and Mao Liang is more serious, and many of them rely on taking water from ditches and rivers.

The main food crops there are wheat and corn, which are harvested twice a year. Corn is planted in spring and wheat is planted in autumn.

Because the Loess Plateau in China has been weathered for two or three thousand years, the loess cover is very thick, and some areas are hundreds of meters thick. The thickest loess layer in the world has a low groundwater level, so it is impossible to afforest everywhere, and greening everywhere will die because of lack of water. There, afforestation and farmers' income are unified, and apple trees, jujube trees, apricot trees, persimmon trees and walnut trees with relatively little water demand are planted in a large area, which can not only maintain soil and water, but also increase farmers' income. Apples from Huangling, Luochuan, Goutouzao from Qingjian and Juglans regia from Yijun are all famous.

Due to the drought and lack of rain in Shaanxi-Gansu region, the loess is thick, compact in structure, low in water content, good in stability and good in slope verticality, and a large number of karst caves are distributed around valleys and ridges in this region. Most people used to live in caves, but now the economic conditions are good, and many people begin to live in brick-concrete houses.

The countryside there is vast and sparsely populated, with dozens of families living together and caves and yards adjacent to each other, forming a natural village, but one natural village is ten miles away from another.

After crossing Suide to the north, we arrived at the Mu Us Desert. This desert is not big in China, but it is indeed a miracle that people conquer nature. This is the first desert conquered by China people, and it has been completely green.

As a native of northern Shaanxi, I can talk to you about this problem!

Loess Plateau-a vast territory to correct a misunderstanding-many people only know northern Shaanxi (Yulin City, Yan 'an City), but in fact, the Loess Plateau covers an area of 635,000 square kilometers and has a vast territory.

The Loess Plateau is one of the four plateaus in China. The loess plateau in a broad sense is the loess area, covering an area of 635,000 square kilometers, including 38 1.000 square kilometers of primary loess and 254,000 square kilometers of secondary loess, which are mainly composed of Shanxi Plateau, Shaanxi-Gansu-Shaanxi Plateau, Longzhong Plateau, Ordos Plateau and Hetao Plain.

One of the greening means of the Loess Plateau-Returning Farmland to Forests The main reason why no trees are planted in the Loess Plateau may be that the Loess Plateau knows very little.

In fact, the Loess Plateau, taking Yulin as an example, has been returning farmland to forests since 2003. After returning farmland to forests, farmers are given subsidies for returning farmland every year. I don't know when it will stop. However, the subsidy is limited, far less than the income from farming. To this end, while returning farmland to forests, in order to make farmers rich. Therefore, when the government returned forests, economic trees (apricots, walnuts, peaches and dates) were planted in some woodlands.

In recent years, the urbanization process in China has been accelerating. The population living in rural areas is decreasing. At present, mainly the elderly and the main body of aquaculture. Therefore, economic forests are gradually neglected, and only a handful of farmers make a living by farming, and some cultivated land has been deserted. But the greening degree is still good.

Prohibit grazing and protect green plants. In addition, after returning farmland to forests, grazing on mountains is prohibited, which greatly protects green vegetation. In the past, the "old man who stopped sheep" wearing a white handkerchief in northern Shaanxi-the old man who herded sheep was rare.

Sandstorms have disappeared in recent years, due to the improvement of the environment and the massive coverage of vegetation, sandstorms have become less and less. I still remember the dusty weather in spring when I was a child, and the visibility was really less than 1 meter. I haven't seen this kind of weather in my mind for a long time.

Prevention and control of soil erosion-building terraces According to the old people, terraces were mainly built in the 1940s and 1960s. Terraced fields have effectively intercepted soil erosion and leveled sloping fields for farming.

Apples have become a new source of wealth for people in northern Shaanxi. With the change of environment and climate, apples also spread to the north and west. Northern Shaanxi has become suitable for apple planting, and from Yulin South to Yan 'an North is the most eugenic area for apples. In recent years, in response to the provincial government's Apple Billion Plan. Under the leadership of the government, Mizhi County decided that apple was the leading industry. In recent years, it has grown to more than 220,000 mu, the fruit bearing area is more than 80,000 mu, and the output value is more than 300 million. Economic trees like apples, while beautifying the environment, have become rich fruit farmers and driven poor households out of poverty.

In fact, the Loess Plateau used to be a forest. According to historical records, the Loess Plateau was a forest and forest grassland before Qin and Han Dynasties, but in recent 2000 years, due to long-term man-made destruction, a large area of forests gradually disappeared and became today's barren hills.

In ancient times, ocean and forest landforms crossed. It is precisely because of this that energy is concentrated in northern Shaanxi, Shanxi and Gansu. Fossil energy sources such as coal, oil and natural gas are the remains of animals and plants that have changed over millions or even billions of years. The raw material of coal is plants, which are shallow buried and easy to mine. Oil and natural gas raw materials are marine animal residues, which are deeply buried and difficult to exploit. The discovery of fossil fuels also confirmed the geomorphological evolution of the Loess Plateau.

Summarize the green coverage rate of Loess Plateau in recent twenty years, and gradually improve it. The typical hilly and gully landforms in the Loess Plateau have brought us many difficulties in farming and returning farmland to forests, but we have overcome them one by one and the environment has gradually improved. Nowadays, the water in the Yellow River has become less yellow and sandstorms have disappeared. I believe that with our unremitting efforts, the environment of the Loess Plateau will be better.

The Loess Plateau is mainly distributed in Qinghai, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan and (rarely) Hebei Province. Many people mistakenly think that the Loess Plateau is the two cities of Yan 'an and Yulin in Shaanxi, which is wrong.

Why not plant trees on the Loess Plateau? In fact, the eight provinces and regions covered by the Loess Plateau are planting trees every year, but they are not as big as before and the survival rate is so high.

First, the climate. Global climate is warming and rainfall is decreasing. Especially in northern China, many rivers are cut off all the year round. In many places, drinking water is very difficult for people and animals. There is not enough water to water them, and it seldom rains. In some loess plateau areas, it hasn't rained for almost a few years, and the trees planted are hard to live.

Second, animal reasons. From 65438 to 0998, China began to return farmland to forests. Today, in some places on the Loess Plateau, there are dense forests and many wild animals. These animals come out for food and often destroy newly planted seedlings.

Third, farmers' enthusiasm for planting trees has been hit. When I was a child, it was stipulated that whoever lived in the barren village above the farm was a family. State-owned forest farms provide free saplings, and farmers plant trees themselves. When the tree grows up, it belongs to the farmers themselves. Now that trees have grown up, every family has hundreds of acres of trees, and it is not allowed to buy or sell them. Even farmers can't burn wood and cut a branch. Farmers' enthusiasm for planting trees has been severely hit. Now, let alone let farmers work and plant trees voluntarily, that is to say, many farmers are unwilling to plant trees, and even if they are willing, the survival rate is very low.

I went to Yan 'an, Shaanxi for the first time in 2002, and found that there are barren hills and mountains everywhere, which is the imaginary Loess Plateau. However, when I went again at 20 12 ten years later, I found that the mountain turned green. Locals say it's the result of returning farmland to forests. If people stop disturbing nature, they will naturally plant plants suitable for the local environment. Last year, I went to Yan 'an again and found that the tree had turned into a forest!

The high loess slope is really a headache.

Topographic map:

The country has also been promoting afforestation, which has achieved certain results, but it is still far from the real goal of soil consolidation and water conservation.

This is probably the reason for the formation of high loess slopes.

Map of Western Han Dynasty:

Before the Song Dynasty-to be exact, before the Anshi Rebellion in Tang Dynasty, Shaanxi and Shanxi were the homeland of the Han nationality, so the economy developed well and the population was prosperous, and there was no large-scale soil erosion here.

After the Anshi Rebellion, the Tang Dynasty began to decline, losing control of the western regions and the Mongolian plateau, and the Han residents were forced to move inward, which caused more serious consequences.

Around 760, Tang Daizong allowed the Tangut Tuoba Chaoguang Department to live in Xiaping area, and the Tangut people began to thrive and grow up gradually. From 1038, when Li Yuanhao openly rebelled against Song Jianguo, to 1 127, when the Northern Song Dynasty perished, the Song-Xia War, which lasted for more than a hundred years, never stopped.

Because of the constant war, Xixia deliberately destroyed the forest in order to avoid the cavalry being fettered. The soldiers and civilians in the Song Dynasty could only cut down forests to make weapons and build cities. In this way, the local forest system basically collapsed and became sparse shrubs and grasslands. After hundreds of years of advancement, it completely became a plant-free area, which is today at the end of the Southern Song Dynasty.

Most importantly, the forest and grassland land were destroyed and the humus layer was completely washed away by rain. Forest humus layer is an extremely important soil stratification, which provides organic matter and main nutrients needed by plants, but it takes about 15 cm for humus layer to form naturally.

Natural humus layer on the surface:

Artificial humus layer:

Therefore, this is the main reason why it is difficult to restore forests on high loess slopes.

The Loess Plateau has become like this. Why do we need to plant trees? Your impression of the Loess Plateau may still remain in the past.