|
In order to study the morphology of white thorn sandbags during the development of changes in vegetation status and soil physical and chemical characteristics, a comprehensive understanding of the development law of sandbags white thorn, looking for soil physical and chemical habitat suitable for its development, and the conservation and restoration of the natural vegetation of the desert areas and desertification prevention has important theoretical and practical significance. In the the Gansu Desert - Oasis transition zone, using the space-time alternative to select different developmental stages, the following: (1) the morphological characteristics of the different stages of sandbags change; (2) changes in the soil physical and chemical properties of the different stages of sandbags; (3) changes in plant growth characteristics of the different stages of sandbags; (4) changes in community structure of the different stages of sandbags, the following conclusions: (1) white thorn the sandbags and development process is the process of morphological characteristics change. Slope and length of the the the white thorn sandbags development process, sandbags height (ie, sand burial depth, resistance to sand burial capacity), size (ie crown width), volume (ie the volume of sand and sand fixation effects) changes gradually increasing and sandbags increased the windward slope slope length is always less than the leeward coordinated growth in the major and minor axes in the horizontal scale, the long axis of stable growth, the short axis experienced quickly to smooth the process. The sandbags height and horizontal scale by strong significant relationship becomes weak. The correlation between the parameters of the white thorn sandbags from strong to weak. (2) white thorn sandbags development process is the process of changes in soil properties. The Nitraria the sandbags development process, the increase in soil moisture, 0 to 70cm layers of soil particles mainly fine sand and very fine sand (0.1 to 0.05), medium sand and fine sand content decreases, very fine sand and silt and sticky The clay content increased gravel content greater than the initial and mature in the medium term, the various stages of coarse sand content is not significant. The total salt content of the soil increased pH values ??greater than in the early and mid mature. Greater than the initial and maturity, soil organic matter and nitrogen content in the medium term increase in soil available phosphorus and available potassium decrease. Plays a major role in soil physical and chemical properties of the soil water content, salt content, organic matter, and AK. (3) white thorn sandbags development process is the process of plant characteristics change. The Nitraria the sandbags development process, the the white thorn average density decreases, the average height of the shoots grow, phytomass and cover greater than in the mid-early and mature. The white thorn coarse root biomass is concentrated in the 0 ~ 50cm soil layer, accounting for more than 92% in root biomass in the 0 ~ 40cm soil up, in which the proportion of root biomass accounted for all root biomass in the early sandbags 83.32% Interim sandbags 86.75 percent, 85.32 percent of the mature sandbags, fine root biomass in the early sandbags and mature sandbags 0 ~ 20cm layer, accounted for 49.73% and 52.89%, respectively, while the medium-term sandbags concentrated in 20 ~ 40cm soil layer, accounting for 47.66 %. Root biomass and soil salinity, organic matter, gravel, and coarse sand content, the difference was not significant. With the increase in soil moisture, available phosphorus, very fine sand, silt, and clay content, PH value, available K in sand and fine sand content reduction the Nitraria in roots and fine root biomass increased. Coarse roots and soil physical and chemical properties of each index difference was not significant. (4) white thorn sandbags development process is a process of community characteristics change. In the white thorn sandbags development process, the various stages of the diversity index, evenness index and ecological dominance low desert vegetation species composition, and the obvious structural levels, with two layer films: shrubs and herbaceous layers. Dominant species prominent, with instability. Quite different stages of each species population changes in the probability of interspecific encounter. Species diversity level of the mid-term and mature significantly higher than the initial, more abundant species, moisture conditions and soil nutrient status of the mid-term and mature than the initial good. Early and mature species evenness index was significantly above the medium-term.
|