| Ganzi Prefecture is located in the west of Sichuan Province, the natural grassland is the main body of the Ganzi state ecosystem. At the same time, Ganzi is the important parts of Sichuan pastoral areas that is one of the five pastoral areas in our country, the level of the grassland economic value to the development of local animal husbandry is significant. In recent years the natural grassland in Ganzi Prefecture is in serious degradation due to overgrazing, the construction of highway, climate warming and mice increased. This experiment was with the key ecological restoration and construction areas in Ganzi as the research object, made vegetation restoration experiment with different kinds of grass combination. The experiment was divided into two parts, one of the experiment is the application effect of four kinds of grass seed combination to cover bare road slope at different altitudes in Kangding County and preliminary screening the combination of grass adapt to different altitude slope governance, while, the other is the reseeding governance of desertification grassland, degenerated bare grassland, hardened grassland and seriously degenerated grassland in Seda County with the combination of Elymus nutans Griseb, Elymus sibiricus L.cv.ChuancaoNo.2 and Avena sativa L. The two experiments were carried out sampling investigation, the main study results are as follows:1. Recovery effect of four combinations of grasses on bare slope at different attitudesAt three kinds of altitudes in Kangding County, four kinds of treatment can rapidly improve the vegetation coverage in the short term, the average increase coverage of 70%. At the attitude of 2600m, the combination of Avena sativa L, Elymus nutans Griseb and Trifolium repens L is the optimal combination in the aspects of total vegetation coverage, aboveground biomass and belowground biomass in this height. At the altitude of 3400m, the combination of Lolium multiflorum Lam, Poa pratensis L and Elymus nutans Griseb performs best in coverage and biomass except height; At the altitude of 3800m, Elymus nutans Griseb, Festuca arundinacea Schreb and Avena sativa L performs very well in aspects of height, coverage and biomass; At three kinds of altitudes, the soil erosion degrees of all combinations are lower than the control treatment (P<0.05), it shows that vegetation restoration means could reduce water and soil loss and fix slope soil effectively.According to the indexes of cover degree, biomass, height, soil erosion degree and so on, and the combination which was better than other grass seed in comprehensive aspect was selected with dominance degree of each combination in each index by comparison in list, the results are as follows:The combination of Avena sativa L, Elymus nutans Griseb and Trifolium repens L are selected at lower altitudes of road slope in Kangding County;the combination of Lolium multiflorum Lam, Poa pratensis L and Elymus nutans Griseb performs is selected at intermediate altitudes;the combination of Elymus nutans Griseb, Festuca arundinacea Schreb and Avena sativa L is selected in high altitudes.2. Reseeding recovery test of different types of degraded grasslandBased on the four types of Seda County deteriorated grassland management, the importance values of Elymus nutans Griseb, Elymus sibiricus L.cv.ChuancaoNo.2 and Avena sativa L were larger. The important value of Avena sativa L was the most in the four grassland communities with absolute dominance, range from 0.3529 to 0.5868. Reseeding has a positive effect on improving the plant community and increasing the excellent grass dominance.The four types of degraded grassland were significantly improved after reseeding, the average vegetation coverage of the sample was increased by 60%, the maximum rate was 89%. The best effect was degenerated bare grassland and the worst was seriously degenerated grassland. The aboveground biomass of sandy land, degenerated bare grassland, hardened grassland and seriously degenerated grassland were 204.6g/m2,924.8 g/m2,824.7 g/m2 and 673.2 g/m2 and they were significantly higher than that of the reseeding treatments(P< 0.05). The mixed sowing combination could quickly and effectively increase the vegetation aboveground biomass. The best effect was degenerated bare grassland and the worst was sandy grassland.The be low ground biomass of hardened grassland and degenerated bare grassland were the most.The soil organic matter content of hardened grassland, sandy grassland and degenerated bare grassland were increased by 17.3 g/kg,18.2 g/kg and 11.9 g/kg after reseeding, but it was decreased by 8.1 g/kg in seriously degenerated grassland; Content of available phosphorus were decreased by 36.6 mg/kg,5.6 mg/kg and 10.7 mg/kg, but it was increased by 0.9 mg/kg in seriously degenerated grassland. In addition to seriously degenerated grassland, the treatment of reseeding could increase the contents of organic matter in other grassland soil and improve the soil. |
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