梭梭幼苗建成对积雪厚度的响应

Seedling Establishment Responses of Haloxylon ammodendronto Snow Thickness

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。

The seedling establishment process is a critical stage for the success of plant regeneration.For arid zones,water is the key limiting environmental impact factor of the seedling establishment process.In this study,the typical natural habitats of Haloxylon ammodendron were selected.To simulate the snow thickness in different years,four water supply of 16,28,48,72 mm were designed to study the coupling relationship between seedling growth especially root growth of H.ammodendronand soil water content.The results showed that,the growth of H.ammodendronseedling was obviously seasonal by the change of soil moisture.In the early growing season（April to June）,the root/shoot ratio of the seedling was the highest in the whole growth season,the vertical root length was 8—10times higher than the seedling height,and the vertical root growth rate was 7—11times higher than the high growth rate.In the early growing season（April to June）and late（September to October）,the root/shoot ratios of seedlings treated with 72 mm water supply were greater than 28 mm and 48 mm.72mm water treatment,the root depth in different periods had reached the corresponding deeper soil level with relatively good water condition after the surface soil moisture decreased.And it would ensure the good growth of H.ammodendronseedling.While the 28 mm and 48 mm treatments failed to reach the corresponding soil moisture level at the time of drought,which was not conducive to seedling growth.In conclusion,the changes of soil moisture caused by the thickness of snow affected the growth and biomass allocation of H.ammodendronseedling deeply.The increase of snow thickness would facilitate the early growth of H.ammodendronseedling,especially the roots,and then use the deeper soil moisture.It would help the seedling to survive trough the harsh drought period and to achieve the seedling establishment.