Abstract:

In order to detect the relationship between VA mycorrhizal fungi and Fraxinus mandshurica roots under fertilization condition, mycorrhizal colonization and root tip morphology, such as root diameter, length and specific root length (SRL) of the first order roots were examined at different soil depth and seasons. This study was conducted at a site of Maoershan Forest Research Station in 2005. The results showed that VA mycorrhizal fungal infection rate in the first order roots was generally reduced 10% under soil N addition, which varied with soil depths and seasons. The infection rate in spring was the highest, followed by that in summer and autumn. The infection rate in 0-10 cm lager of the soil was significant higher compared to the 10-20 cm of the soil. In comparison with non-mycorrhizal roots, VA mycorrhizal infection did not alter root diameter and length, but significantly decreased SRL. Those changes of root tip morphology were consistent in different treatments, soil depths and seasons. The findings suggested that the degree of colonization by VA mycorrhizal fungi in the first order roots of Fraxinus mandshurica was dependent upon the N availability, soil depths and seasons, and the root morphology was changed by VA mycorrhizal fungal colonization, which all useful knowledge to were in understanding principle of fine root longevity and turnover in this forest ecosystem.

Key words: Fraxinus mandshurica, VA mycorrhizal fungi, fine root morphology, diameter, length, specific root length(SRL)