Weed Communities And The Eco-niche Of Wheat And Maize Fields In Yellow River Irrigation Areas In Lanzhou

The weed communities in farmland eco-system compete with crops in light, water, and fertilizer, and are the host of many insects. The data show that among the factors affecting farm crops yield, weed damage reach to 10% in the world. A large sum of money has been spent to control weeds in farmland. Moreover, using single weed killer in farmland for a long term often causes the changes of crops and the weed communities, and brings about new problems for control weeds. Niche theory has advanced in plant ecology research, but its application reports on farmland weed population and community ecology are still fewer. The researches on weed niche have instructive meaning on predicting weed community succession.Weed communities in wheat and corn field in Yellow River irrigation areas were studied by using niche breadth formulation of R.Levins and niche overlap formulation of Cowll and Futuyma to grasp main weed species, dominant species and the ecological adaption range. The results were as follows.1 Calystegia hederacea,Chenopodium album ,Cephalanoplos segetum,Portulaca oleracea,Amaranthus retroflexus,Setaria viridis,Sonchus brachyotus and Polygonum aviculare were the main eco-damaging population in wheat fields and the dominant weeds were Calystegia hederacea and Chenopodium album. The main weed species in corn fields were Calystegia hederacea, Convolvulus arvensis, Chenopodium album, Cephalanoplos segetum, Capsella bursa-pastoris, Echinochloa crusgalli, Portulaca oleracea, Amaranthus retroflexus and Setaria viridis. Chenopodium album,Amaranthus retroflexus and Echinochloa crusgalli were the dominant weeds in corn fields.2 There was similar dynamic trend of weeds in the low, middling, and high wheat density treatments. The first seedling emergence peak was from last ten day of April to the first ten day of May and the second peak was in middle ten day of June when Setaria viridis and Amaranthus retroflexus were emergence of seedlings. The first seedling emergence peak in corn field was in middle ten day of June when Calystegia hederacea,Convolvulus arvensis,Cephalanoplos segetum and Capsella bursa-pastoris reached to the max of seedling emergence. The second peak was from the first to the middle ten day of July when Chenopodium album, Echinochloa crusgalli, Portulaca oleracea, Amaranthus retroflexus and Setaria viridis reached to max gradually.3 Setaria viridis plants in wheat fields were the most, then the Chenopodium album. According to the biomass results, dry weight overground of Chenopodium album in low,...