| Seed germination and seedling establishment occupies an important position in the life cycle of plants, they are the decisive factors in plant populations continue. In the process of its development, they often suffered all kinds of extreme weather or environmental impact, but they still breed many desert plants that adapt to adversity. Gurbantunggut Desert locates in Junggar basin, which had more than 20 cm of snow in winter, and abundant plant resources. but recently, the majority of research on seed germination and seedling establishment is conducted in laboratories, and studies are limited with regard to the characteristics of natural seed germination and seedling establishment at the population level. So we can’t fully comprehend the impact on seed germination and plant setting under the global climate change. Consequently, The current study investigated the south of Gurbantunggut Desert, and according to the the experimental methods of combining field investigation and indoor experiments. Firstly, we need a comprehensive understanding of environment real demand characteristics of seed germination, and than analyzing microenvironment influence on seed germination and seedling settled, finally we summarizes the drought adaptability of seedling settled. Not only lay a foundation for a comprehensive understanding and application of stress resistance plant resources, but also to predict the future change and better utilization of plant resources has important value and practical significance for the ecological restoration.Characteristics of environment dependence of seed germination and seedling settlement indicated that : 1) seeds start to germinate only two days after snow melts at the average daily temperature(day/night) of 3.5 °C(6.7 °C/-0.5 °C) and at a soil volumetric water content of 24.2%. This content reaches 52.4% if the snow melts completely. Fifteen days after snow melt, all species germinate when the soil volumetric water content is 6.0% and the average daily temperature is 12.9 °C(18.3 °C/7.1 °C). 2) In artificial wild settings, Treatments that combine natural snowfall with spring rainfall do not differ significantly from treatments with natural snowfall. Nonetheless, spring rains can extend the time for half-germination. The germination period is long under this condition at averages of two and five days. Furthermore, the number of surviving seedlings is also greater than that observed under the treatment “ rainfull loney”, Therefore, winter snow melt is the decisive factor in seed germination of herbaceous plants, and the late spring rain plays only a small role in this process.Characteristics of micro-habitat adaptation of seed germination and seedling settlement showed that: 1) The seed germination of the tested species can be divided into four patterns: rapid, transitional, slow, and low, the rapid nearly 50%. 2) 152 species pairs showed positive correlation in a total of 276 species pairs among 24 species, while the other 124 species pairs showed negative correlation, Haloxylon persicum, Seriphidium terraealbae and Calligonum leucocladum with the 10, 13 and 11 of 20 dominant herbs were positive correlation and most had significantly positive correlation, respectively, but there were no significant positive correlation in Haloxylon ammodendron with these herbs, obviously showing the habitat divergence. 3) Low-pattern plants mainly grow in upper dunes, the seedling survival rate is about 60% and are significantly associated with arbors and shrubs. Rapid-and slow-pattern plants distribute in middle and lower dunes, the seedling survival rate is about 65%, and a few of these plants are significantly associated with arbors and shrubs. Transitional-pattern plants generally develop in the low land between hills and middle dunes. the seedling survival rate is about 75%, and these plants do not display a notable association with arbors and shrubs. Therefore, in order to adapt to the environment, different species formed a variety of germination strategy, and the germination strategies are influenced by the microenvironment, arbors, and insignificantly by families and genera or life type. Seedling survival and growth also affected by shrubs surroundings simultaneously.Characteristics of drought adaptability of seedling settlement showed that: 1)The root growth rate of most species was 2.5mm>5mm>10mm. The growth rate of all species was 10mm>5mm>2.5mm, we considered that when drought stress is relatively large, the moderate drought can promote the root growth, reduced overground plant growth, and increases the absorbing ability of root system, decreases water dissipation on the strategy to reduce the harm by drought environment. 2)Soluble sugar, Proline and Malondialdehyde content of 14 species changes were 2.5mm >5mm >10mm, plant initiative accumulate of soluble sugar and proline to regulate cell osmotic potential, prevent cell excessive dehydration. but the greater increase of malondialdehyde suggests that the higher degree of lipid peroxidation and the greater damage degree of plasma membrane. In a word, Some species(eg, Eremopyrum orientale, Salsola korshinskyi Drob, etc.) may predominate in the behavior drought resistance, the speed of it’s root growth is faster, and the physiological drought resistance is weaker; other species(eg, Plantago minuta, Schismus arabicus, etc.) may dominant in physiological drought resistance, the strength of its physiological drought resistance is stronger, and root growth was slower; some species(eg,Corispermum lehmannianum) which both have behavior and physiological drought resistance, and both of the drought resistance are relative stronger.In conclusion, Winter snow melt water is the key determinant of seed germination of the Gurbantunggut Desert, and the late spring rains plays only a small part, and the germination average daily temperature is relatively low. In this process, the micro-habitat(slope, shurbs) is also an important influence factors on seed germination and seedling settlement. H.persicum, S.terraealbae and C.leucocladum have obvious nursing effect to herbs, and there exist a trade-offs in different slope positions numbers of seed germination and seedling survival, and than make the plant community stability. Drought resistance of the plant seedlings is a comprehensive of variety properties, and in arid areas, the plant root system and physiological and biochemical behavior have changed under drought stress, plant can use roots pierced into deeper soil to get through drought, and also can regulate a series of physiological and biochemical processes in the body to fight the drought, or they can also through the combination of both for drought resistance. |
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