Study On Ecological Mechanisms Of Weeds Invading Into Crop Fields

We observed and investigated the performance of sowing seeds instead of natural invasion on fixed quadrants for the purpose of researching on the effect of invasion of weeds on different completive ability of two spring wheat, the soil water and aboveground biomass and abundance of weeds.The results showed that germination niche or requirements for germination, varied among plant species in the Loess plateau. The results showed that cold-wet stratification, light and temperature fluctuation affected the germination percentage of plant species. Cold-wet stratification had significant effect on 7 plant species; light had significant effect on 10 plant species; temperature fluctuation affected 8 plant species significantly. But Achnatherum splendens,Calyategia hederacea,Thermopsis lanceloata did not respond to any factor or the combination of factors.Our field result indicated that: 1.Weeds inhibited the seedling emergence rate, plant height, harvest index and 1000-seed weight of Dingxi-24 significantly. The successful invasion reduced the ineffective tiller number of Heshangtou, but have no much effect on other aspects. 2. The average harvest index of Dingxi-24 as higher than Heshangtou, but the invasion of wheat decreased the harvest index of Dingxi-24 and had no effect on Heshangtou. 3. The soil water is no significant difference at the early growth stage. However, the soil water in treatment area is higher than the control. 4. Wheher sowing weed or not, there were weeds and the varieties and number did not vary a lot at early growth stage to booting stage. However, the varieties and number increased greatly in sowing area at the late growth area. 5. The successful establishment of weeds is correlated with the sowing of weeds, wheat cultivars and wheat density. The treatment of sowing, wheat cultivars and wheat density had significant effect on those species after the invasion of weeds in May. Invasion of weeds had significant effect on the establishment of Calyategia hederacea,Avena fatua,Corisermum declinatum,Setaria viridis. And the abundance of those species is higher than those of control.