Seedling Bank And Seedling Survival Characteristics In Different Soil Erosion Environments In The Hilly-gullied Loess Plateau

In the hilly-gullied Loess Plateau, soil erosion is serious. Vegetation can radically controlsoil erosion, and seedlings as the basis of vegetation succession, play an important role in therenewal of vegetayion communities. The objective of this paper was to explore seedlingcharacteristics and its survival characteristics under different erosion environments in theYanhe watershed of the hilly-gullied Loess Plateau region. To do this, nine typical watershedsin different vegetation zones (Forest belt, Forest steppe zone,Steppe zone) and two typicalwatersheds in forest-steppe zone (Songjiagou and Zhifanggou) were selected as study sitesrespectively. We examined seedling bank characteristics, seedling dynamic characteristics andseedling survival characteristics under different erosion environments (sunny gully slope,sunny hilly slope, hill top, shady gully slope, shady hilly slope)of hilly and gully slope withfield investigation. And the main results are shown as follows:(1) The seedling species was93in forest zone,90in forest steppe zone and85in steppezone. And the seedling of Compositae, Gramineae, Leguminoseae and Rosaceae accountedfor more than half of the total number of seedlings in three vegetation zones. Perennial herbswere the dominant life-form and xerophytic and mesoxerphytic were the main water ecotypes.(2) Seedlings density and diversity were different in different erosion environments ofhilly and gully slope in three vegetation zones. In the same vegetation belt, its overallperformance was that seedling density was bigger and species was richer on shady gully slope.The seedling density in forest steppe zone and steppe zone were significantly greater than thatin forest zone and there was no significant difference in seedling species diversity.(3) Dynamic variation of seedling density, species diversity with time showed raised firstand then decreased. The maximum of density appeared in early July, minimum inmid-November; the minimum of diversity index and richness index appeared in early April,maximum usually in early September. The dynamic variation of evenness index was notobvious.(4) Seedling density in different erosion microenvironments was shallow trench> planting plexus> fish-scale pit> bare ground. Seedling species diversity index, richnessindex and evenness index had no significant difference. In different months, the seedlingcharacteristics under different erosion microenvironments had obvious changing trends, butthere were some differences.(5) In different erosion environments, the survival characteristics of main seedlingspecies were different. The species of Artemisia gmelinii, Heteropappus altaicus, Potentillatanacetifolia in sunny hilly slope, Heteropappus altaicus, Stipa bungeana, Potentillatanacetifolia, Artemisia scoparia in sunny gully slope, Artemisia gmelinii, Stipa bungeana,Ixeris Chinensis, Linum stelleroides in hill top, Artemisia gmelinii, Patrinia heterophylla inshady hilly slope, Artemisia gmelinii, Stipa bungeana, Patrinia heterophylla in shady gullyslope had stronger seedling survival ability, were able to withstand harsh weather and survivethrough the winter successfully.(6) The effect of soil moisture on seedling growth and survival was the most obvious,slope, rainfall and aspect followed by, while altitude and soil nutrient had some influence butwas not significant.