Investigation on Growth Situation and Soil Property of Grass-forest System in Lake Buffer Zone of Zhushan Bay, Lake Taihu

The sample plot survey and analysis methods were applied to investigate four typical grass-forest systems in lake buffer zone of Zhushan Bay of Lake Taihu, including wetland grass-forest system, poplar protection forest, nearby tributary grass-forest system and taxodiumascendens protection forest. The soil nutrient contents of organic matter, nitrogen and phosphorus, the plant growth situation including biodiversity, canopy density and grass coverage, the bacterial population and soil physical properties were studied in detail. The results showed that the organic matter contents of surface soil was between 15.1 g/kg and 40.3 g/kg (level 1 to 4), overall at rich level; the total nitrogen content of soil was between 0.76 g/kg and 1.13 g/kg (level 3 to 4), overall at medium or slightly low level; while the total phosphate content was between 0.09 g/kg and 0.17 g/kg, all at level 6 (extremely low level). Compared with the soils in China and other countries, the organic matter, total nitrogen, ammonium nitrogen and nitrate nitrogen contents in Zhushan Bay were totally at a medium level, while the total phosphate content was at a low grade. The soil nutrient index calculated from bacterial population indicated that the nutrient levels of the four grass-forest systems were very low, only between 0.003 and 0.014. The evaluation on plant growth situation showed that the grass-forest system was relatively good, but all the four grass-forest systems had very low biodiversity. Therefore, it is difficult to recommend a good grass-forest system example only from the present four systems.