Study On The Characteristics And Its Trends Of Seed Bank And Vegetation On The South Bank Of Nailun Lake

The construction of artificial water storage engineering in arid area has changed the soil water content and vegetation community pattern and dynamics.However,some objective factors such as inconvenient transportation,high cost of scientific research and laggard status of technology lead to the backwardness of environmental impact research of artificial water storage engineering in arid area,especially compared with the implementation speed of water conservancy project.In this paper,we investigated the effects of artificial water storage on soil seed bank and the relationship between seed bank and aboveground plant on the south bank of Nylon Lake in the Yellow River flood diversion area of the northeast margin of Ulanbuh Desert by the methods of seed germination and vegetation sampling with the purpose of providing scientific basis for the evaluation and construction of artificial water storage engineering.Its main conclusions are as follows:1.Artificial water storage engineering had a significant impact on soil seed banks.With the sharp increase of soil moisture content,the number and species of seeds in the soil both increased and then decreased,which showed that the density of soil seed bank was the highest in the unflooded zone(733 grains/m~2),the relative less in the control zone(609 grains/m~2),the least in the flooded zone(176 grains/m~2),and significantly lower in the sand area after flooding.Severe flooding may result in the decrease of species in seed bank in the flooded area of the falling zone.The amount of shrub seeds in the soil seed bank of Ulanbuh Desert in the flood diversion area of the Yellow River was significantly reduced by flooding interference,and the proportion occupied in total species was also significantly reduced.The seed density of soil seed bank in the falling zone of the Yellow River flood diversion zone decreased as follows:the unflooded zone>the control zone>the flooded zone in each season.2?Herbs of annual and perennial,which occupied more than 75%of the total species in each section,were the main vegetation types in the soil seed bank of the three sections(flooded,unflooded and controlled)of the falling zone.Annual herbs were the most,followed by perennial herbs and shrubs.The greater the intensity of flooding interference,the higher the proportion of soil seed bank for annual and perennial herbs,while the proportion of soil seed bank distribution in the control zone was higher than that in the unflooded zone for shrubs.There were no shrub seeds in the flooded area.With the drastic increase of soil moisture,the vegetation in the study area changed from the original sandy arid plants to the water-tolerant and saline-tolerant plants,and the life type transitioned from shrub to herbaceous,indicating that water flooding would inactivate the shrub seeds.3.Diversity index,richness index and evenness index of soil seed bank were significantly different under different flooding disturbance.There were significant differences in species diversity index,richness index and evenness index of soil seed bank in 3 sand types in flooded area(p<0.05),which showed fixed sand>semi-fixed sand>active sand.There was no significant difference between species richness index and evenness index in 3 sand types in unflooded area.The species diversity index was fixed sand>semi-fixed sand>active sand.There were significant differences in diversity index and richness index of soil seed bank,but there was no significant difference in evenness index of soil seed bank.4?The density of soil seed bank of active,fixed and semi-fixed sandy land was consistent in different months.The total number of seeds in soil seed bank of different sandy land was the least in June and the most in March,which indicated that most seeds had germinated before June,and the least in active sandy land and the most in fixed sandy land,which indicated that flooding would not change the original density characteristics of seed bank in this area.In the falling zone,the number of seeds in soil seed bank of unflooded area was higher than the flooded area.The seed types in the unflooded area were more abundant,and poor similarity with the flooded area.