The Process Of Succession In Alfalfa And Abandoned Land On The Water And Wind Crisscross Region

In order to study characteristics of ecological index of vegetation communities and community succession patterns of artificial grassland and abandoned land in the process of natural recovery, selecting Alfalfa artificial grassland and abandoned land as research object respectively in Liudaogou watershed of Shenmu County, Yulin City, Shaanxi Province of water erosion wind erosion crisscross region on the loess plateau, the study were conducted in the process of succession of Alfalfa artificial grassland and abandoned land after the ban by spatial method instead of time method. On this basis, analyzed the differences in soil water characteristics and the ground biomass in the different vegetation types sample area, and put forward in building composite vegetation can be using the limited water resources more reasonable, shorten the construction process of vegetation recovery and control the soil erosion in the process of vegetation restoration construction.Return visit investigation for Alfalfa artificial grassland and the survey of community characteristics were conducted Mainly, Determine the plant height, vegetation coverage, density, species richness index, etc; at the same time, to select sample of different vegetation types of vegetation canopy height, surface vegetation coverage, the leaf area index, the ground biomass, species richness, soil moisture content, surface soil bulk density and soil saturated hydraulic conductivity and other indicators of measuring. The results showed that:(1) Gleason index, Shannon-Wiener index and evenness index has a similar change trend after 11 year’s natural restoration succession except Margalef index, that is the results of the survey in 2014 is generally higher than the results of the survey in 2004 in Alfalfa artificial grassland, it was indicated that the species richness, species diversity and evenness of community were improved significantly; A total of 42 kinds of higher plants occurs in the quadrat and increased by 10 kinds; Leguminous has 6 genera 7 species and decreased by 2 species; Compositae has 6 genera 9 species and increased by 2 species; Gramineae has 8 genera 9 species and increased by 3 genera 4 species; The Leguminosae, Compositae and Gramineae this three families account for 58.8% and 59.5% of the total number of genera.(2) According to the change characteristics of dominant species and plant diversity in plant community through natural recovery of 40 years, founding that in shady slope it is appears to the succession trend that the Alfalfa artificial grassland turn to Artemisia gmelinii-Stipa bungena subshrub secondary natural grassland, while the succession trend of sunny slope is still for Stipa bungena secondary natural grassland.(3) There were 38 species of higher plants in survey samples of abandoned land with different recovery years, it’s belonging to 34 genera and 13 families, including Leguminous 6 genera 7 species, Compositae 9 genera 10 species and Gramineae 7 genera 7 species, the three family plants occupied the main position in the process of natural restoration succession. At the years of 12 and 21 in restoring succession, the species richness indexes(Gleason index and Margalef index), species diversity index(Shannon Wiener index) and evenness index of shady-slope abandoned land were higher than in sunny slope, the main causes of the increase in the number of community family, genera and species were increased in species richness.(4) Under two modes of vegetation restoration, planting alfalfa artificial grassland and abandoned land with natural closed, the model of planting alfalfa artificial grassland was faster than the model of abandoned land with natural closed.(5) The canopy height, degree of surface vegetation coverage, leaf area index and aboveground biomass were improved significantly after deep root plants compound with shallow root plants; the soil water content in surface increased significantly; species richness also showed a trend of increase. The main factors of affecting differences of aboveground biomass between single vegetation and composite vegetation is the differences of absorbing water between compound vegetation root system and the single vegetation root system, and the differences of utilizing soil moisture in different depth between deep root shrubs and shallow root herbaceous plant.(6) Deep root plants should match with shallow root plants in the process of vegetation restoration construction can utilize limited water resources reasonable and effective and improve aboveground biomass of vegetation, canopy height and vegetation coverage on surface, thus can control soil denudation effectively in the water and wind crisscross region.