Abandoned Farmland Vegetation Restoration And Reconstruction On Alluvial Fan-Fringe Zone Of Manas River In Xinjiang

The impact of different pioneer crops on soil physical and chemical properties was studied on abandoned farmland of alluvial fan-fringe area in the Manas River valley. From the macro and micro perspective, a mathematical model of individual alfalfa-soil water and salt system was established, which would help to change local ecological environment by planting alfalfa meadow.Six kinds of crops (alfalfa, processing tomats, pepper, wheat, sunflower and cotton) were selected to plant on abandoned farmland, and then different indicators were chosed to analyze each soil quality; A mathematical model of water-salt system was established to study its impaction on individual alfalfa; The method of soil basal niche-fittest was used to evaluate the change of soil environment.The effect of vegetation restoration at its initial stage was evaluated by soil basal niche-fittest in abandoned farmland. The results showed that: All of the 28 plots were in low fertility. Only one of alfalfa plots was in Level 1 fertility; Plots which planting sunflower, alfalfa and processing tomato were in Level 2 fertility; Plots which planting cotton and pepper were in Level 3 fertility; The last level (Level 4) was wheat plot. Soil physical-chemical character of six kind pioneer crops was compared: All of the six kind soils were in alkaline condition. Soil salinity showed a conversed T-shaped distribution, which means the top soil with the highest salinity, so there was a salt-top phenomenon in experimental farm. The content of organic matter, nitrogen and available nitrogen were of the same change. Organic matter and nitrogen content of sunflower soil was hingest while its total phosphorus content was the lowest of the six kind crop soils. The soil of processing tomato and pepper were with higher content of available phosphorus and lower avaloable potassium. Soil of alfalfa and cotton were with higher avaloable potassium. Soil fertility of six pioneer crops were of significant difference in the soil layers, the soil nutrients content was decreased with the soil depth. Soil fertility was low at the initial vegetation restoration of abandoned farmland, which means corresponding measures should be taken for different levels of soil fertility. Alfalfa performed best among six plants when taken abandoned farmland restoration, so it can be recognized as the optimic crop at fan-fringe area to restore the abandoned farmland.Because the soil evaporation and plant transpiration, soil water of alfalfa root were reduced in the growing season. Soil evaporation is gradually reduced, and diving was deposited in non-growing season, then soil water content was tended to balance. The soil salt was congregated in surface layer in non-growing season.The gathered area of salt was moved from -40 cm to -60 cm the region in the growing season.With soil salinity increasing, soil water content was decrease.when soil diving evaporation was increased, salt was transported to upward, and the root zone salt content was declined. There was a new balance between water and salt finally.During the growing season, individual alfalfa would consume 262.6 mm water, diving water supply was 63 mm, and the transport of salts was 44.5 g in the root zone. Alfalfa per square would consume 456.5 mm water, diving water supply was 112 mm, and the transport of salts was 52 g in the root zone. During the non-growing season, individual alfalfa would consume216.6 mm water, diving water supply was 136.7 mm, and the transport of salts was 46.7 g in the root zone. Alfalfa per square would consume 176.1 mm water, diving water supply was 96.2 mm, and the transport of salts was 72 g in the root zone.The consumption of water for plant transpiration mainly comes from rainfall, which accounting for 55.4% during the growing season.