琼西热带稀树草原成因初探

Preliminary study on the origin of savanna in western Hainan Island

海南岛处于热带季风气候区,但其西部出现非地带性的热带稀树草原景观,原因尚有争议。主要从海南岛东西部气候条件的对比分析琼西热带稀树草原的成因。琼西地区旱季时间长达6个月(11～4月)。冬春季(旱季),受琼中山地阻挡,琼西位于冬季风的雨影区,旱季降水量与海南岛其他地区相比较少。春季受干热风的影响,蒸发量较大。另外,该地日照时数长、太阳辐射总量大、风速大等因素,进一步增大旱季蒸发量,加剧该地旱季水分收支不平衡。与海南岛东部相比,琼西地区旱季干旱尤为突出,与热带草原气候相似。这种旱季干旱的气候抑制了木本植物生长,从而在琼西形成稀树草原景观。

The Hainan Island is located in the tropical monsoon climate zone.However,savanna landscape,which is obviously non-zonality,exists in the western part of the island.The reason is still in debated.The climatic conditions of the western Hainan Island were compared to the east,to discuss the origin of the Savanna in this region.The dry season in the western Hainan Island is as long as six months（November-April）.During the dry season,the western Hainan Island is the rain shadow region of the northeast wither monsoon,which is blocked by the mi-Hainan mountain.Therefore,precipitation in this region is relatively less than the eastern part of the island during dry season.During spring,the xerothermic wind causes high evaporation.In addition,the large sunshine duration,strong solar radiation and high wind speed,promote water evaporation,thus the water budget is unbalance during the dry season.Drought in dry season in the western Hainan Island is more serious than the east,and it is very similar to the tropical savanna climate.Trees can not survive during the extremely drought dry season,thus the Savanna landscape formed.