Determination of spatial genetic structure (SGS) in natural populations is important for both theoretical aspects of evolutionary genetics and their application in species conservation and ecological restoration. In this study, we examined genetic diversity within and among the natural populations of a cosmopolitan grass Phragmites australis (common reed) in the Yellow River Delta (YRD), China, where a mosaic of habitat patches varying in soil salinity was detected. We demonstrated that, despite their close geographic proximity, the common reed populations in the YRD significantly diverged at six microsatellite loci, exhibiting a strong association of genetic variation with habitat heterogeneity. Genetic distances among populations were best explained as a function of environmental difference, rather than geographical distance. Although the level of genetic divergence among populations was relatively low (F’ST = 0.073), weak but significant genetic differentiation, as well as the concordance between ecological and genetic landscapes, suggests spatial structuring of genotypes in relation to patchy habitats. These findings not only provided insights into the population dynamics of common reed in changing environments, but also demonstrated the feasibility of using habitat patches in a mosaic landscape as test systems to identify appropriate genetic sources for ecological restoration.

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Spatial Genetic Structure in Natural Populations of Phragmites australis in a Mosaic of Saline Habitats in the Yellow River Delta, China

The morphodynamic difference in the western and southern coasts of Laizhou Bay: Responses to the Yellow River Estuary evolution in the recent 60 years

Quantitative assessment of human activity intensity was a prerequisite for analyzing impacts of human activity on ecosystem as well as assessing the evolution of ecological environment. A model is built based on GIS in this paper to construct a quantitative evaluation framework of human activity intensity. Firstly, 13 human activities indices such as GDP per capita, total industrial output value, annual electricity consumption, population density, the number of business units were selected and a set of human activity index system referring to economic, humanistic, social aspects was established. Then, the Analytical Hierarchy Process method was employed to determine the weights of each human activity indicator. Finally, based on the spatial analysis function of GIS, human activity intensity of the Pear River Delta was exemplified. The human activity intensity of nine cities in the Pearl River Delta was calculated in 1990, 1995, 2000 and2005. The results indicated that human activity intensity of the Pearl River Delta increase gradually temporally whereas decreased from east to west spatially.

Quantitative assessment of urban human activity intensity based on GIS-A case study of the Pearl River Delta

The present Yellow River delta has developed over the past 150 years as a consequence of siltation and avulsions of the river channel,flooding and sedimentation.Human activities have also sharply changed the delta processes.Oil fields and a new city with a modern infrastructure have been developed on the newly created land.The river channel within the delta is very dynamic.Humans stabilize the river channel by dredging and building levees for construction of the oil field infrastructure and residences.Moreover,the sediment is being used for land creation.To control flash flood humans have dug many drainage channels to discharge flood from the Haihe River and its tributaries.Nevertheless,the number of river mouths is proportional to the ratio of water and sediment under natural conditions.The number of river mouths is too large and tidal flow carries sediment into the river mouths and caused the river mouths shrinking.Dredging is only a temporary solution to this problem.Double guiding dykes,long enough to cut off the high turbidity belt along the coast,are being examined as the main strategy to control sedimentation of the river mouths.The shallow high turbidity belt along the Bohai coast can be changed into land if numerous guiding dykes are constructed.

Cheng Dong-sheng

Papers

Delta processes and management strategies in China——II The Yellow and Haihe River deltas