The Study On The Altitudinal Gradient Pattern Of Plant Community Characteristics In South Slope Of Daiyun Mountain

In this dissertation, plant flora, life form, main populations'niche, species diversity and their altitudinal gradient patterns were analyzed, and main results are as follows:(1)There existing 191 vascular plants belong to 120 genera and 61 families which are 10 world-widely distributed families, 33 tropically distributed families and 18 temperately distributed families in the south slope of Daiyun Mountain. Pantropically distributed families dominate and account for 57.38% of the 33 tropically distributed families, which is followed by East Asian and Tropical South Africa Disjuncted which account for 24.24% of the 33 tropically distributed families. Temperate Families is donimated by North Temperate and South Temperate Families which account for 55.56%, which is followed by North Temperate Famlies who account for 22.22%. The number of tropical families increase with the rise of altititude, and the number curve of temperate families present double peaks along the altitudinal gradients, corresponding closely to the environmental gradient. The distribution of types of plant genera in south slope of Daiyun Mountain follows the order: Tropical Genera (TG) (64genera)> Temperate Genera (Temp G) (41genera)>pantropical genera (PG) (12 genera)> Eastern Asian Endemic Genera (ECEG) (3genera). Among the flora the number of TG is the most , and then that of TempG is the second. Among the tropical genera, the pantropical genera cover 21genera, accounting for 32.81%, and the tropical Asian genera cover 13genera, accounting for 20.31%. Among the temperate genera, north temperate genera and East Asian and North American Disjuncted Genera each occupy 8 genera, making up 19.51%. In the flora of south slope of Daiyun Mountain, the composition of its genera is complex, and the main trend of flora with the increase of altitude is that : 1)the number of tropical genera and Subtropical Genera firstly increase along the rise of elevation, then decrease, but temperate genera generally decrease along the rise of elevation; 2) the proportion of TG increase along the rise of elevation, which indicates the change of temperature.(2)The vascular plants are dominated by the phanerophytes, accounting for 85.56% of the total, and geocryptophytes, chamaephytes, therophytes, and hemicryptophytes respectively account for 5.76%, 3.66%, 3.14%, and 1.57% of the total. The distribution of life forms in south slope of Daiyun Moutain follows the order: phanerophytes> geocryptophytes> chamaephytes> hemicryptophytes, which indicates that the vegetation of south slope of Daiyun Mountain is characterized by forest vegetaion. Among the 10 subtypes of phanerophytes, the number of evergreen little phanerophytes is the most , accounting for 47.12% of total life forms and 54.88% of phanerophytes. Phanerophytes hold an important position at each altitudinal gradient, and its number firstly increase and then decrease with the increase of elevation; the number curve of geocryptophytes and chamaephytes show two peaks with the increase of elevation; the number of therophytes firstly decline and then increase generally; hemicryptophytes show discontinuously distribution within the whole altitidinal gradients.Among the 7 altitudinal gradients of south slope of Daiyun Mountain, the sum of important value of Phyllostachys heterocycla is 98.6, accounting for 14.1% of the total important value sum, and it hold the greatest important value which are 46.4 and 43.6 respectively at the elevation of 900m and 1000m; Pinus taiwanensis hold the greatest important value which is 76.5 at the elevation of 1500m. The niche breadth of Bi value of the main tree layer plants follow the order: Machilus thunbergii, Castanopsis. fabri, Cunninghamia lanceolata, Lithocarpus hancei, Rhododendron ovatum, Castanopsis eyrei, Phyllostachys heterocycla, Engelhardia fenzelii , Pinus taiwanensis, and Cyclobalanopsis multinervis. Among the top 10 dominant populations, 42 species pairs have niche overlap, accounting for 97.7% of the total species pairs; Castanopsis fabri and Lithocarpus hancei hold the greatest niche overlap, showing the most similar pattern on ultilizing resources between two species.(3)The analyses ofαdiversity of vasvular plants in south slope of Daiyun Mountain show that the Simpson index, Shannon-Wiener index and Pielou index have the same change trend which is that the value of those index firstly increase and then decline. The analyses of thereβdiversity of them show that the curve of community dissimilarity coefficient show two peaks, and its greatest value emerge between elevation of 900m and 1000m; the curve of Sorensen index and Jaccard index along the rise of altitude also show two peaks ; Cody index shows different change trend to other index, and its curve declines as the altitude increases, which indicates that the differences among all altitudinal gradients is reduced as altitude increases, and above the elevation of 1600m, the similarity among different altitudinal gradients is the greatest.