Development of land desertification in Bashang area in the past 20 years

Natural conditions in Bashang area are characterized by zonal transitions which are liable to be impacted by natural disasters and intensified human activities. The extremely fragile eco-environment is also liable to have desertification formed and developed. In the 18 years from 1978 to 1996, the desertified land area of Bashang within the scope of the map nearly doubled, a total increase of 2199.11 km2, averaging an increase of 122.17 km2 per year. Moreover, the seriously desertified area increases rapidly. Land desertification in Bashang is the combined result of natural factors and irrational human economic activities. Cultivated land expansion, population growth, and overgrazing aggrevate desertification development.

Analysis on Landscape Pattern in the Upper and Middle Reaches of Yarlung Zangbo River:Taking Zhongba County,Angren County, Rikaze City as Example

Taking Zhongba County, Angren County, Rikaze City located at the Upper and Middle Reaches of Yarlung Zangbo River as landscape units , this paper studied the difference of the landscape pattern under various degrees of human disturbance in the three areas. The results showed that： the three areas all reflected the same characteristic of landscape pattern in Qinghai-Tibet Plateau, the natural landscapes were in the absolute dominant position. However, from Zhangba to Rikaze, with human disturbance intensity increasing, anthropogenic features of landscapes became more and more outstanding, In Zhongba, the landscape structure appeared to be simpler with coarse grains and a less rich diversity, Conversely, in Rikaze, the landscape showed a complicated shape with finer grains and a relatively richer diversity, This reflected that the impact of human activities to natural landscape behaved a gradually-growing trend from the upper reach to the middle one of Yarlung Zangbo River Basin.

Reconstruction of cultivated land during mJid- Holocene in the middle and lower reaches of Yellow River and human impact on vegetations

Yangshao culture is the most important mid-Holocene Neolithic culture in the Yellow River catchment, and thus, a study on the impact of human activities on the environment is important. In the current study, the distribution pattern of the cultivated land in late Yangshao culture is reconstructed using GIS tool and site domain analysis （SDA）. The results show that the cultivated land during 5.5-5.0 ka BP was mainly distributed in the Weihe River valley, Luohe River valley, northwestern Henan Plain, Fenhe River valley and eastern Gansu region, especially concentrated in the Xi＇an-Baoji line of the Weihe River valley. At that time, at least 37,000 km2 of lands were reclaimed in the middle and lower reaches of the Yellow River, and 132,000 km2 of lands were affected by agricultural activities. Human activities had become the driving force of land use/land coverage. Charcoal records indicate that the ancestors of Yangshao culture burnt forests for reclamation, leading to the decrease of arbor pollen at 5 ka BP in core areas of the Yangshao culture. The areas that were significantly affected by human activities accounted for 3.2% of the Yangshao culture influenced area, while the moderately affected areas accounted for 20.1% of Yangshao culture influenced area. Meanwhile, 92% of the land areas on the edge and outside of the Yangshao culture influenced area were not affected by human activities. The arbor pollen in these areas did not decrease until 4.0 ka BP.