| Referring to the main content in ecological construction in West China, systematic researches were carried out to study the root distribution characters of vegetation at different succession stages. Dynamic characters of main root index (including root biomass, root length, root surface area, and root volume, etc) of vegetation at different succession stages were revealed. And corresponding relation between root index and soil factors was setup, which helped to reveal the root behavior mechanics for ecosystem development, and provided scientific and technological support to vegetation construction and ecological restoration in loess region. Based on the above analysis, following researches can be reached:1. During the rehabilitating succession process, root biomass of vegetation on returned farmlands changed with the rehabilitating time. At the initial stages, more roots were distributed in the deeper soil. With the development of vegetation succession, vegetation type changed from annual types to perennial types, more roots were concentrated in the upper soil. To the vegetation on natural grassland, its root system was concentrated in surface 0~40cm soil layer. All the other root indexes, including root length, root surface area etc, showed similar distribution patterns.2. Analysis of root extinction coefficient showed that this parameter decreased with the increase of abandoned years, which indicated that there was more root concentrated in the surface soil layer with the increase of abandoned time. This kind root distribution pattern on abandoned lands improved soil physical and chemical characters, and favored the intrusion of new species and vegetation succession.3. Soil aggregate content was different at different succession stages. Generally, soil aggregate with its diameter larger than 0.25mm decreased with the increase of soil depth, which indicated the decrease of root influence on soil aggregate. Among the soil aggregate of all diameter classes, only the aggregate with its diameter between 1 mm and 2 mm showed similar trends with root biomass, which implied its better indication with root. With the increase of restoration years, aggregate increased with larger diameter, and in vertical direction. also increased.4. At the initial time of restoration, soil organic matter content was relative low, with the development of vegetation succession, soil organic matter increased. When the restoration time was over 20 yrs, soil organic matter content was higher, which was similar to what was on natural grassland. And the soil organic matter content in deeper soil increased with larger diameter, too.5. Researches on dynamics of water stable aggregate in land degradation and restoration process indicated that after reclamation, water stable aggregate decreased and bigger size particle tended to decrease much, >0.25mm soil water stable aggregate increased during the restoration years, soil organic content decreased or increased with the land degradation or restoration and during the former years, they changed rapidly, there existed positive linear relation between soil organic content and water stable aggregate (Φ>0.25 mm): y = 23.195x + 12.12, mean weight particle size of soil water stable aggregate increased corresponding with the content of >0.25mm soil water stable aggregate or restoration years. Land restoration augments the mean weight particle size of soil water stable aggregate through the increase of soil water stable aggregate content and its stability was enhanced, soil structure was improved.6. Analysis of soil characters and root distribution characters on lands with different restoration years indicated that, both soil physical and chemical properties were ameliorated due to the existence of root biomass, and soil organic matter content and aggregate content were increased too. Quantitative relation between root biomass and soil factors was set up based on the above analysis. |
PDF Full Text Request