Vegetation And Environmental Factors Of Gully-Ridge Complex System In Loess Hills

The Loess Hilly Region is the main geomorphologic shape in Loess Plateau. Microclimate factors and environment factors are investigated for more than1year by season. Besides, this paper investigated Inner Mongolia, Shaanxi and Shanxi provinces at the junction of Loess Hilly Region by quadrat method. This study contains72sample plots, among them, Zhungeer Loess Hilly Region was the direct environmental factors in study area. Research shows that:(1) The difference of microclimatic factors ingully-ridge complex system:daily average wind speed, hill ridge>shady slope>sunny slope>hill gully; Illuminance, hill ridge>sunny slope>hill gully>shady slope (P<0.05); Air thermometer, shady slope>hill gully>sunny slope>hill ridge; Air humidity, hill gully>sunny slope>hill ridge>shady slope. Green up time of plants exist significant differences, sunny slope>hill ridge>hill gully>shady slope. Snow covered in winter, hill gully>shady slope>hill ridge>sunny slope.Soil temperature of5cm to100cm,sunny slope>hill ridge>hill gully>shady slope. The difference between sunny and shady slope of soil temperature is decreased regularly with the increase of soil depth. Through the analysis of Pearson, the result showed significant negative correlation(-0.985**).Soil humidity, shady slope>hill ridge>hill gully>sunny slope. The depth from5cm to100cm, humidity of sunny slope is significant lower than shady slope.(2) Contained145kinds of wild vascular plants, of which87species are on sunny slope,113species are on shady slope. Poaceae, Asteraceae and Legumes are the top three families in Loess Hilly Area. Among them, the common first big family of sunny and shady slope is Poaceae, but the first large family of hill ridge is Asteraceae. This fully reflects the unity and differences of gully-ridge complex system.Through analyzed the plant life form spectrum in the study area, we found that sunny slope, shady slope and hill ridge are all perennial herbs occupied the main advantage. Annual and biennial herbs are higher percentage on sunny slope and hill ridge, but on shady slope are lower. The moisture ecotypes spectra of gully system in Loess Hilly Area is, xerophyte> mesophyte> intermediate xerophyte>xeric mesophyte, and in hill ridge is, xerophyte> intermediate xerophyte>mesophyte> xeric mesophyte.A study of plant community diversity of gullies-hill ridges complex system vegetation in loess hills has found that richness, abundance index and Shannon Wiener index of species on shady slope was the obvious highest. On the contrary, richness, abundance index and Shannon Wiener index of plant communities on sunny slope was the lowest. And richness and Shannon Wiener index of species on sunny slope was obvious lower than that on shady slope, reflecting the superiority of shady habitats.(3)The direct factor affect gullies-hill ridges complex system vegetation in loess hills is wind speed (0.9551**), soil total nitrogen (0.7584*), atmospheric humidity (0.7342*) and soil available nitrogen (-0.775**).And soil humidity (0.9862**), the depth of snow (0.8145**) and atmospheric temperature (0.8145**) also play a role in vegetation differentiation.