Effects of Soil Amendments on Survival Rate and Growth of Populus sibirica and JJlmus pumila Seedlings in a Semi-arid Region, Mongolia

摘要

This study was conducted to investigate etfects of soil amendments on survival rate and growth of seedlings in a semi-arid region, Mongolia. 2-year-old Populus sibirica and Ulmus pumila seedlings were planted in alkaline sandy soils and treated with 2levels of nitrogen, elemental sulfiir, artificial moisture retention and converted loess. After 4 months, the seedling survival rate of both species decreased as the amount of nitrogen increased. Nitrogen has been generally known to increase seedling survival rate and growth by supplying nutrients, however, reduced survival rate in this study might be affected by consequential increase in soil osmotic pressure, which was caused by excessive nitrogen fertilization. The root collar diameter (RCD) growthof both species increased significantly by the treatment of converted loess, and only RCD growth of P. sibirica increased by the artificial moisture retention treatment. Although P. sibirica is drought-tolerant, it is in the group of Populus spp. which requires a high capacity of available water. Conversely, the elemental sulfur treatment showed no effect on survival rate and RCD growth for both species due to the low oxidation of sulfiir in arid soils. The extended monitoring of seedling growth and soil characteristics is required to elucidate the long-term effects of soil amendments in the semi-arid region, and the fijrther studies are also needed to examine the appropriate amount of fertilizers for both species.