Acta Geographica Sinica ›› 2006, Vol. 61 ›› Issue (10): 1075-1083.doi: 10.11821/xb200610007

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Land Use Change in Lhasa Area, Tibet from 1990 to 2000

CHU Duo1, ZHANG Yili2, ZHENG Du2   

  1. 1. Tibet Institute of Plateau Atmospheric and Environmental Sciences, Lhasa 850000, China;
    2. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
  • Received:2006-03-02 Revised:2006-07-10 Online:2006-10-25 Published:2006-10-25
  • Supported by:

    National Natural Science Foundation of China, No.40361001; No.90202012; National Basic Research Program of China, No.2005CB422006

Abstract:

Based on the results of the first land use survey in Tibet Autonomous Region carried out in the late 1980s, land use map of Lhasa area in 1990 was compiled for the main agricultural area in Lhasa valley using aerial photos obtained in April, May and October 1991 and Landsat imagery in the late 1980s and 1991 as remotely sensed data sources. Using these remotely sensed data, the land use status of Lhasa area in 1991, 1992, 1993, 1995, 1999 and 2000 were mapped through updating annual changes of cultivated land, artificial forest, grass planting, grassland restoration and residential area and so on. According to land use status of Lhasa area in 1990, 1995 and 2000 at five-year intervals, the spatial and temporal land use dynamics in Lhasa area from 1990 to 2000 are further analyzed using GIS spatial models in this paper. The main conclusions are as follows: (1) Land use change in Lhasa area during the period 1990-2000 happened mainly near the major towns and the Lhasa valley. Much natural vegetation was replaced by artificial forests; vegetation coverage and biomass have obviously increased. These changes are directly related to human activities aiming to improve regional environment, such as tree planting, grassland restoration during the implementation of the integrated agricultural development project at that time. (2) The most remarkable increase in area is forest as the forestland increased by 2.556% (2713.48 hm2) from 1990 to 2000. The most comprehensive changes of land use in Lhasa area from 1990 to 2000 is rangeland conversion. Rangeland was converted to cultivated land, horticultural land, forestland, settlement and water body. Among them, the largest area of land use changes is rangeland conversion to forestland (2338.25 hm2), being 94.093% of the area relating to land use change. Some 186.53 hm2 of cultivated land have been converted to forestland over the period 1990-2000, being 54.857% of the total area relating to cultivated land conversion into other land use types. Some water bodies changed into cultivated land, forests and rangeland. Some 243.13 hm2 of water body were converted to forests, being 93.126% of the area relating to land use change, which happened mainly from the bottomland conversion to the artificial forests. (3) Because Lhasa area is a semi-arid and environmentally vulnerable region on the Tibetan Plateau, effective measures should be taken to improve local environment in a short term through bioengineering technologies such as artificial forestation, grassland restoration and so on. These measures can improve local microclimate, conserve water, prevent land desertification and soil and water loss through modifying vegetation cover types and increasing vegetation coverage.

Key words: land use change, Lhasa area, Tibetan Plateau