Weed Ecological Strategy And Its Integrated Control Of Mixture Grassland Of Cultivated Perennial Grass In Alpine Region Of Qinghai Tibetan Plateau

The paper is about the weed community changes of the mixture grassland of cultivated perennial grass in Qingzang Tibetan plateau, the seed bank of the first-second- third- and forth-year-old grassland and pasture, the impact the root and seeds on the weed seeds and the control effect of the three chemicals 2,4-D bufylate, tribenuron and methsulfuron-methyl on the weeds. The conclusions are :1. There are the same varieties of the weeds in the first- and second-year-old grassland and the most are annual; the variety of the annual weed in the third and the forth decreases, and the perennial increases. The weeds are annual in the third-year-old grassland that is fertilized in the second year, and the grassland grazed at the same time is similar to the forth in the varieties and the weed community, furthermore the most weeds are perennial. The effect of way that when the grassland is planted we mix the oat seed with the grasses is changeable, and the control efficiency is greatly dependent on the elaboration of plant, used grasses and quantity of used grass seeds. It is good for the seed bank, the quantity and the quality and the community of the grassland to control the weeds. The stability of the grassland with one grass is worst, but it is same in the weed and grass proportion for the grassland planted respectively with two, three and four grasses. There are four different period of weed community from the first- to the forth- year.2. There are a large quantity of the vigorous weed seeds in the soil. The seeds of soil in faun increases greatly because of the adding of the maturate seeds. The output is mainly before the July, and the input begins from the end of July and finishes at end ofSeptember. The seeds in the waster land is most. The output peak is the one- and two-year-old grassland, but the output of the third and the forth is very poor. The seed bank will change greatly because of the chemical control.3. The water extract of the grass roots promotes the germination of grasses and restrain the germination of weeds. The seeds of grasses make the seeds of weeds to germinate earlier or later, especially for Plumbagella micrantha, Ehhotzia calycocarpa. The seeds of Elshotzia calycocarpa restrain the seeds of grasses. The seeds of the grasses increase the germination of Elshotzia calycocarpa. The effect of Chenopodium glaucum on the grasses and the grasses on Chenopodhim glauaim is not significant. The seeds of Plumbagella micrantha greatly restrain the germination of the grasses.4. The annual weeds seriously reduce the quality and quantity of grasses in one-year perennial cultivated grassland. It is necessary to control. There are many ways to control them. If possible, the control result is the best by human being. Besides the weedicides such as 2,4-D bufylate, tribenuron and methsulfuron-methyl can control the weeds efficiently, the best concentration is expensively 1 188 g/hm2, 4.27 g/ha2, 3.32 g/ha2. All in all, it is good to choose proper weedicides to control the weeds in one-year grassland.