| Huang-Huai-Hai (3H) plain plays an important strategic role, for it is the important grain production base, industrial core area and population denseness district in China. Yellow River Delta (YRD) new-born wetland is the typical wetland ecosystem in 3H plain, and is the most integrated, broadest, youngest wetland ecological system, is the quickest area growing delta in the world. It is of vital significance in keeping ecological balance and guaranteeing local ecological economy sustainable development. However, 3H wetland has been endureing serious impact and stress because of large-scale and high strength human activities, and the issue has posed great threat to the health of biosystem and local ecological security. In this study, methods of field survey and laboratory ecological simulation were adopted to investigate community pattern of typical emerging plants in 3H wetland and to explore responses of emerging plants at levels of morphological structure and physiological characteristics to ecohydrological process. The main conclusions are as follows:1. Three field results on community pattern of typical emerging plants in YRD wetland showed that plants community composition in YRD wetland is simple and the constructive species is few. There are three main communities, i.e. Suaeda salsa, Tamarix chinensi, and Phragmites communis. The change of soil salinity has significant effect on the components of plant communities, especially the dominant species and the constructive species, as well as on the distribution of different communities and succession.2. Studies on morphological structures of P. communis in different habitats of YRD wetland showed that variations of morphological structures of the salt tolerant plants P. communis adapted different habitats are diverse. Bulliform cells and sunken stoma on the leaves are the important ecological adaptations of P. communis to the ecohydrological process. 3. The effects of heavy metals (HMs) (cadmium and mercury) on seed germination and seedling growth of P. australis and Triarrhena sacchariflora, which are the two main typical emerging plants in Hongze Lake wetland, were studied. The results showed that the effect of HMs toxicity is not invariable during plant growth. Compared to the stage of seedling growth, P. australis and T. sacchariflora are more susceptible to HMs at the stage of seed germination, and the species of P. australis is more tolerant than T. sacchariflora to the HMs and is a better candidate for restoration in Hongze Lake wetland ecosystem.4. Comparative study of photosynthetic and physiological features of the reed in different artificial habitats of YRD wetland were done, the results indicated that both the daily dynamics of photosynthesis of the reed in the two regions is a double peak curve, however, there are some difference. Decline of net photosynthetic rate of the reed in saline areas was caused by the decrease of activities related enzyme in photosynthesis.5. Effects of NaCl salinity on biochemical and physiological changes of Typha latifolia were investigated, to assess the salinity stress responses. The results showed that there was the plant height and relative growth rates (RGR) based on biomass were adversely affected by salinity. Contents of chlorophyll and total carotenoids were also decreased significantly with the increase of NaCl concentration. The proline and malondialdehyde (MDA) accumulation in seedlings grown at higher salinity was considerably greater than that at 0 mM salinity. The study provides new insight into how emerging plant T. latifolia respond to increased concentrations of NaCl salinity. |
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