![]() As a result of these projects and initiatives, China's greening has contributed to global greening totals 15, 16. More recently, desert greening has been conducted by people and enterprises, for example, the Ant Forest and Society of Entrepreneurs & Ecology (SEE). In recent years, the Chinese Government has recommended a series of major strategies, for example, the "construction of ecological civilization" and "lucid waters and lush mountains are invaluable assets", and also promoted greening projects, including "Three North Shelterbelt Project", "Beijing-Tianjin Sandstorm Source Control Project", and the "Natural Forest Protection Project". Land afforestation has been at the forefront of China’s policy principles, and there are government departments specializing in this field. This layer of gravel and coarse sand plays a significant role in the area’s ecology and landform, decreasing the dust emissions known as “black vegetation” to the gobi region.Ĭhina has a large expanse of arid areas, and has suffered from droughts for a long time. The pores between gravel particles can trap and fix sand. Therefore, the gobi region has a good aerodynamic bed surface for the rapid transport of large amounts of sand 9. Of sediments with a grain size of > 2 mm, about 58.33% comprises medium and coarse pebbles (8–32 mm), 25.03% comprises fine pebbles (4–8 mm), 11.61% comprises very fine pebbles (2–4 mm), and few very (5.03%) coarse pebbles or cobbles (> 32 mm) (Fig. According to our field investigation, the average gravel grain size is 4.90 mm. Erodible fine sand is transported away from the desert, while non-erodible gravel and coarse sand are concentrated on the surface, protecting underlying soil from erosion 12, 13, 14. Gravel is the basic characteristic of this part of the desert (Fig. Eroded by long-term strong winds, the alluvial fan of the Heihe River has changed into desert area, known as the Central Gobi Desert. The most serious environmental consequences of planting shrubs in the gobi region is the destruction of “black vegetation”, increase of dust supply, and increased intensity and frequency of dust storms 8, 9, 10, 11. However, irrigation was cost- and labor-intensive, and once it stopped, the shrubs withered and died over the next years (Fig. With effective irrigation, the shrubs could survive the first two years with good growth conditions (Fig. Therefore, continuous irrigation is key to the shrubs’ survival. Considering this utilization efficiency, the annual precipitation of 35–55 mm cannot support the sustainable growth of this shrub. This means that each shrub consumes about 15 mm of precipitation per year. ammodendron is about 0.3 m 3/year per plant. Based on experience, the water consumption of H. Therefore, the planted shrubs cannot use this underground water.Īs we estimated from satellite images and field investigation, the density of the newly planted shrubs was 50,000 plant/km 2. The sites where shrubs were planted, however, are 1–6 km away from the Heihe River, with a groundwater level at depths of 5–10 m, which even the longest roots of H. The lateral supplement of this river to its alluvial fan is limited to several hundred meters on either side of the river channel. The Heihe River is the only water source in this area and has received only 5.34 × 10 8 m 3 water per year since 2002. This species can survive in conditions with the moisture content of below 2%, but the moisture content below 1% can cause serious recession of the shrubs 7. Its main root can reach depths of more than 2 m, with the deepest roots being able to reach groundwater at depths of 4–5 m. Haloxylon ammodendron is a drought-resistant shrub species with a well-developed root system, adapted to very dry land. So only the very sparse drought- resistant can survival here. Normal precipitation cannot therefore improve the water condition of such sandy land. ![]() Intense evaporation removes surface water almost immediately, leaving only a small amount of water to infiltrate to lower soil layers, and little moisture is available in the lower soil layers of this area. Field investigation showed that a single precipitation event of 24.7 mm wets only 6–7 cm of the sand layer 6. Maximum daily precipitation is about 12 mm. Annual precipitation in the gobi region is concentrated and short, usually occurring in 4–5 isolated precipitation events. Moisture provided by precipitation infiltration is the main water source that can be used by vegetation 5.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |