梭梭幼苗死亡与土壤和大气干旱的关系研究

Relationship Between Haloxylon ammodendron Seedling Mortality and Water Content in Soil and Atmosphere

以古尔班通古特沙漠南缘沙漠中的一年生梭梭幼苗为研究对象,对环境气象因子、土壤含水率、幼苗根系垂直伸展状况、幼苗死亡动态进行了全生长期的连续监测研究。结果表明,尽管梭梭幼苗根系伸展迅速,当年可达1.5m,幼苗死亡率动态变化仍然与土壤表层含水率显著相关,而与根区或深层含水率不显著相关。但统计分析结果显示,土壤表层含水率并不总是梭梭幼苗死亡率波动的主导因素。当土壤含水率低至0.82%时,无论大气干旱程度如何,幼苗死亡率都急剧升高;而当土壤含水率高于1.25%时,幼苗可以耐受大气干旱,幼苗死亡只与土壤表层含水率显著相关;当土壤含水率在0.82～1.25%之间时,幼苗死亡率与大气干旱程度(空气饱和差)显著相关。据此我们推测,当土壤表层含水率低于1.25%时,大气干旱主导死亡率的变化;反之,则土壤水分主导。

Field monitoring of Haloxylon ammodendron tent and meteorological factors during the whole growing seedling mortality, root extension, soil water conseason of first-year Haloxylon ammodendron was carried out at the southern boundary of the Gurbantunggut desert. The results showed that the Haloxylon ammodendron seedling mortality had a significant correlation with water content in surface soil, and the correlation between Haloxylon ammodendron seedling mortality and water content in deep soil wasn＇t significant despite the seedling roots stretching downward quickly, up to the depth of 1.5 meter in one year. However, the statistical analysis indicated water content in surface soil was not the only factor influencing the Haloxylon ammodendron seedling mortality. The Haloxylon ammodendron seedling mortality increased dramatically when the water content in surface soil decreased as low as 0.82 %, regardless of the degree of air water deficit in air; The Haloxylon ammodendron seedlings could tolerate water deficit in air when the water content in surface soil was higher than 1.25 % and the water content in surface soil determined the seedling mortality. There was a significant correlation between Haloxylon ammodendron seedling mortality and water content in air when water content in surface soil was at 0.82%-1.25%. It was concluded that water content in air determined the Haloxylon ammodendron seedling mortality when the water content in surface soil was less than 1.25 % and water content in surface soil determined the Haloxylon ammodendron seedling mortality when the water content in surface soil was higher than 1.25%.