陕北黄土高原植物区系分区界线初探

A PRELIMINARY STUDY ON THE BORDER LINE OF THE FLORISTlC REGIONALIZATION IN THE LOESS PLATEAU OF NORTHERN SHAANXI

本文根据优势种、特征种的分布和现代的自然环境条件,如地貌、气候、土壤等因素,初步探讨了陕北黄土高原植物区系分区界线,将定边植物县与府谷、吴旗植物县的分界线,确定在沿长城一线,但在靖边新城附近应偏离长城向北推移约20km,在定边县应偏离长城向南推移约40km,大致与400mm的等雨量线相符。府谷、吴旗植物县与延安植物县的分界线,确定在东起清涧的川口,向西南经清涧、延川县永坪、延安蟠龙,再向西经安塞县碟子沟、茶坊、砖窑湾、西河口,志丹县杨洼塌、旦八、吊坪、吴堡,抵达吴旗县白豹一线。延安植物县与黄龙、陇县植物县的分界线,确定在东起省界至黄龙县的大岭,向西经黄龙县北,绕洛川塬南缘,折向西北至黄陵县,继续西行,经黄陵的双龙、上畛子,达省界后,沿子午岭分水岭至马栏,向南经旬邑的石门关、淳化县,向西经麟游,至千阳后,折向西北经陇县抵省界一线。黄龙、陇县植物县南达关中盆地的北缘。

The present paper is a preliminary discussion on the border line of the floristic regionalizations in the Loess Plateau of northern Shaanxi. Based on the distribution of community dominant and characteristic species,and modern natural environmental conditions including topography, climate, soil, etc., the boundary between Dingbian District and FuguWuqi District is shown as follows, it goes along the Great Wall, but extends from the Great Wall northward to 20 km nearby Xincheng of Jingbian Xian and southward to 40 km in Dingbian Xian,which is roughly consistent with the 400 mm isohyet. The demarcation line between Fugu-Wuqi District and Yanan District is show as follows. Chuankou of Qingjan Xian——Qingjan——Yongping of Yanchuan Xian——Panlong of Yan'an Xian——Diezigou, Chafan,Zhuanyaowan and Xihekou of Ansai Xian——Yangwata, Danba, Diaoping and Wubu of Zhidan——Baibao of Wuqi. The demarcation line between Yanan District and Huanglong-Longxian District is shown as follows: Daling of Huanglong Xian the north of Huanglong Xian——the southern fringe of Luochuanyuan——Huanling Xian——Shuanglong and Shangzhenzi of Huangling Xian——the watershed of Mt. Ziwuling——Malan——Shimenguan of Xunyi——Chunhua Xian——Linyou Xian——Qianyang Xian——Long Xian. The boundary of Huanglong-Longxian District extends to the northern fringe of Mid-Shaanxi Basin in the south.