Plant Species Diversity In Gaoquan Houwan Areas Of Loess Plateau In Middle Gansu Province

It was important to know about the revegetation of the little watershed management for summarizing the successful experiences in the middle of Gansu province of the Loess Plateau. The main areas of Gaoquan little watershed was selected. A total of 15 sites, 75 plots were set along altitude of 2200m to 2445m in the ravine, 2230m to 2410m on the eastern slope and 2230m to 2415m on the western slope to investigate vegetation of Gaoquan Houwan areas. Species composition, species richness, a diversity and ? diversity of different altitudinal gradient were analyzed. The results obtained as follows: 1. 201 species were recorded in 75 plots, which belonged to 102 genera and 35 families. Compositae, Gramineae, Rosaceae, Leguminosae, Cyperaceae, Labiatae and Ranunculaceae were dominant families of Gaoquan Houwan. 2. In the ravine, No. of families, genera,species reached maximum at the sites which altitude was between 2230m and 2239m, while a diversity peaked between 2200m and 2229m, their minimum were all between 2230m and 2239m. On the eastern slope, No of genera, species and a diversity increased first then decreased, and families changed little with decreasing elevation. On the western slope, No. of families, genera, species and a diversity increased with decreasing elevation. In the same altitude, species richness on the eastern slope was higher than the western slope, a diversity on the eastern slope was obviously higher than the western slope above 2370m, but lower below 2370m. 3. βdiversity fluctuated greatly between neighboring sites in the ravine. Two high Cody index and two low Jaccard index appeared between 2300-2385m and 2230-2256m, where were transition habitats. On the eastern and western slope, Cody index increased and Jaccard index decreased between neighboring plots with decreasing elevation. 4. Compared with the investigation of 1992, 124 species and 7 families were recorded in 2004. No. of shade plants, hygrophyte plants and liana plants increased, and distributed widely, Simpson index, Shannon-wiener index and Evenness index were high,which indicated that vegetation restored and environment improved after sustainably controlling and naturally restoring on Gaoquan little watershed.