海南岛西部热带沙漠化土地特征与成因

海南岛西部沙漠化土地具有热带海岸沙地的地域特征、形态特征、旱生植被景观特征和土地利用快速演变特征。在大气环流、雨影区和海流的共同影响下,岛西形成热带半干旱气候和热带稀树草原环境,孕育并存在自然沙漠化发展的动力、空间和物质基础。岛西历史时期沙漠化受气候变化和毁林开荒等活动的影响,但仍是自然沙漠化为主的沙漠化过程。20世纪以来现代沙漠化经历了发展、恢复、再发展、逆转、波动等5个阶段,沙漠化既受数年或数十年尺度的气候变化的作用,又受人为不合理经济活动的影响。用因子分析等诊断、分析后认为人为活动的贡献率远大于气候变化的贡献率,现代沙漠化已演变为以人为沙漠化为主的沙漠化过程。

Study on the Characteristics and the Cause of Sandy Desertified Land in the West of Hainan Island

The west of Hainan Island is the only sandy desertified area of the tr opical dry grasslands with sparse trees in China, and it is a very typical sandy desertified land type and course. The sandy desertified land, which is on the s andy coastal plain, the river delta and the sandy mesa, is distributed in the lo ng and narrow area. The sandy desertified lands have the tropical coastal dene c haracteristics in the district, the shape, the xerophyte and the rapid evolvemen t of land use. Under the influence of tropical monsoon climate, the foehn effect of the rain shadow field of the Changshan Mountains and the Wuzhishan Mountains and the cold ocean current in the Beibu Gulf, it is developed into the semi-ari d climate and the environment of dry grasslands with sparse trees. So that it co mes into being for the driving force, the space and the material base of the des ertification. The sandy desertified land in the west of Hainan Island in history is due to many factors such as the climate change, the excessive reclamation an d excessive firewood, but the factor of human leads the first. The present-day s andy desertified land in the west of Hainan Island can be divided into five stag es of increase, renewal, re-increase, reversion and fluctuation in the 20th cent ury, its process is not only controlled by the climate change in several years o r decades scale, but also the unreasonable human activities. The area of sandy d esertified land increased from 201.45 km2 to 251.61 km2 from the end of the 1950 s to the 1970s with an increasing rate of 3.53 km2/a. It has decreased to 122.57 km2 since the 1990s with a decrease rate of -7.72 to -3.20 km2/a. The temperatu re in the west of Hainan Island appeared to go up by 0.24 oC/10a and the precipi tation descended by -23.93 mm/10a for the past 50 years. The land resources are being excessively exploited because of continuous increase in population and dom estic animals in recent decades. The results show that the human activities are greatly associated with desertification degree, and the present-day sand deserti fication in the west of Hainan Island has evolved into the desertification proce ss which is mainly affected by the human activities.