Forests are the main components of terrestrial ecosystems and play an important role in the protection and construction of the national ecological security barrier. For a long time, China's large-scale afforestation had been practiced in areas with rainfall higher than the 400 mm threshold, but the issue of afforestation in high altitudes on the Tibetan Plateau remains elusive in both practical experience and theoretical exploration. It is worth thinking further about what principles should be followed in the selection of tree species and suitable altitudes for afforestation in high-altitude areas, as well as what experiences and lessons of previous afforestation efforts should be applied in high-altitude areas. As per the law of vegetation zonal distribution, this paper argues that afforestation at high altitudes should comply with the principle of vegetation zonal distribution and the low temperature limitation, and points out that afforestation is feasible only within the forest distribution area and below the altitudes of climate timberlines. Furthermore, we demonstrate the potential spatial areas of afforestation, and determine the local tree species that may be used for afforestation based on the existing problems of afforestation in eastern Tibet. In summary, afforestation in high-altitude areas of the eastern Tibetan Plateau must comply with the law of zonal vegetation distribution, focus on the upper limit of altitude and the selection of suitable tree species, and adopt only suitable native tree species.

The cushion plant Androsace tapete is an endemic species that is widely distributed in the Qinghai-Tibetan Plateau, and also predominant in the alpine grassland that is locally degraded due to overgrazing and other reasons. As an ecosystem engineer cushion plant, its ability to facilitate the restoration of degraded alpine grassland was studied in a degraded alpine grassland at an elevation of 4500 m on the southern slope of the Nyainqentanglha Mountains in Damxung. The species diversity, soil nutrients and water content underneath and outside the cushion plant A. tapete were investigated. The results showed that soil nutrients underneath the A. tapete cushion were significantly increased by about 16%-48% compared to outside the cushion, of which the organic matter and total N were increased by 16.2% and 18.9% respectively, and the soil water content was increased about 12%. The index of species diversity of richness (S), Shannon-Wiener’s H and Simpson’s D all increased with the coverage of cushion plant A. tapete. Our results suggested that this cushion plant can facilitate restoration of the degraded alpine grassland by modifying the local soil environment and increasing the community diversity, so it should be conserved for the restoration of degraded alpine grasslands on the Qinghai-Tibetan Plateau.

In order to construct stable vegetation for reducing wind and sand disasters and soil erosion in the Bashang Area of Northwest Hebei Province in China, it is very important to understand the ecological water demand of different vegetation types in this area. Based on observed data and the Irmak-Allen formula, we investigated the ecological water demand and ecological water shortage of arbor, shrub and grassland in Bashang Area of northwestern Hebei province. The results showed that the actual evapotranspiration values of the three vegetation types in the growing seasons in the study area from high to low were arbor forest (401.81 mm), shrub (358.78 mm) and grassland (346.02 mm). The minimum ecological water requirements of arbor forest, shrub and grassland in the growing season were 243.96 mm, 218.35 mm and 211.36 mm, respectively, and the optimal ecological water requirements were 472.99 mm, 423.34 mm and 409.77 mm, respectively. In addition, the optimal ecological water shortage values were 198.56 mm for arbor forest, 148.91 mm for shrub and 135.34 mm for grassland. The ecological water shortage of vegetation has obvious seasonality, with the largest water shortage in May and June, and a lower and steady water surplus in July to October. Therefore, an artificial water supplementation in May and June would alleviate the drought stress of the vegetation. The rainfall in Bashang Area of Northwest Hebei Province can meet the requirements of minimum ecological water demand for arbor forest, but the gap between the rainfall and the optimal ecological water requirement is too large to support good growth of an arbor forest, which could explain why the degradation of poplar protective forests has occurred in Bashang Area.

The Conversion of Farmland to Forests and Grasses Project is the most symbolic and globally important ecological engineering effort to build the human and natural life community. After the call and mobilization stage since the founding of the People's Republic of China, the first round of Conversion of Farmland to Forests and Grasses occurred at the end of the 20th century. With the second round of Conversion of Farmland to Forests And Grasses launched in 2014, the central government has invested 535.3 billion yuan altogether by 2020, and 34.83 million ha have been returned to forest and grassland in 25 provinces (autonomous regions and municipalities) (2435 counties included). Among them, 14.23 million ha were returned from farmland; barren hills and wasteland afforestation accounted for 17.53 million ha; and sealed mountain forest cultivation represented 3.07 million ha, accounting for 40% of the total afforestation area of national key projects in the same period, and 41 million households and 158 million farmers benefited directly. The project construction has made great achievements. The total value of ecological benefits has reached 1.42 trillion yuan, plus economic benefits of 0.26 trillion yuan, and social benefits of 0.73 trillion yuan, for a total amount of 2.41 trillion yuan. This effort has made outstanding contributions toward building an ecological civilization and a beautiful China. Looking forward to the future, the Conversion of Farmland to Forests and Grasses will embark on a new stage of high-quality development, which will strive to achieve high-quality construction, high efficiency and a high level of management. China will promote the third round of conversion of farmland to forest and grassland from 2021 to 2035, and it is expected to return 6.67 million ha to forests and grasses.