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幼苗建成过程是植物自然更新能否成功的关键阶段。对于干旱区而言,水分是幼苗建成过程的关键限制性环境影响因子。该研究选择梭梭典型自然生境、模拟不同年份积雪厚度状况,共设置16、28、48、72mm 4种供水量梯度,研究了梭梭幼苗生长尤其是根系生长与土壤水分变化间的耦合关系。结果表明:受土壤水分变化的影响,梭梭幼苗生长过程具有明显的季节性。生长季早期(4—6月),幼苗的根冠比处于整个生长季的最高水平,垂直根长是幼苗高度的8~10倍,垂直根生长速率是高生长速率的7~11倍。生长季早期(4—6月)和后期(9—10月),72mm供水处理梭梭幼苗根冠比均大于28mm和48mm处理。72mm供水处理,其根系深度在不同时期均达到了相应表层土壤水分下降后相对较好的较深层次,保证了梭梭幼苗的正常生长。而28mm和48mm处理,其根系生长未能在干旱到来时达到相应土壤水分较好的层次,不利于幼苗的生长。综上,积雪厚度所引起的土壤水分变化深刻地影响着梭梭幼苗的生长和生物量分配,积雪厚度的增大将有利于梭梭幼苗尤其是根系的早期快速生长,进而利用更深层次的土壤水分,以此度过严酷的干旱时期,实现幼苗的建成。
Seedling formation process is the key to the success of plant natural regeneration. For arid areas, water is a critical limiting environmental factor for seedling establishment. In this study, typical habitats of Haloxylon ammodendron were selected to simulate snow thickness in different years. Four water supply gradients of 16, 28, 48 and 72 mm were set up to study the coupling relationship between Haloxylon ammodendron seedling growth, especially root growth and soil water change . The results showed that the growth of Haloxylon ammodendron seedlings had obvious seasonal changes under the influence of soil moisture. In the early growing season (April to June), the root / shoot ratio of seedlings was the highest in the whole growing season. The vertical root length was 8 to 10 times of the seedling height and the vertical root growth rate was 7 to 11 times of the high growth rate. In the early growing season (April-June) and later (September-October), the root-shoot ratio of the seedlings of Haloxylon ammodendron seedlings treated with 72mm water treatment were both greater than those of 28mm and 48mm. 72mm water treatment, the depth of root system at different times reached the corresponding surface soil moisture decreased relatively better after the deeper level to ensure the normal growth of Haloxylon ammodendron seedlings. However, the treatment of 28mm and 48mm did not reach the corresponding level of soil moisture at the beginning of drought, which was unfavorable to the growth of seedlings. In summary, the change of soil moisture caused by snow thickness has a profound impact on the growth and biomass allocation of Haloxylon ammodendron seedlings. Increasing the thickness of the snow helps the early rapid growth of Haloxylon ammodendron seedlings, especially the root system, Soil moisture, as a result of harsh drought period, to achieve the completion of seedlings.