Abstract: We examined the relationship between soil microbial community function and soil  thickness in green roof under three soil  thicknesses (40, 70, and 100 cm), by using a control simulation test method. Our aim was to reveal the role of soil layer thickness in improving the overall ecological function of green roof from a perspective of soil biology. The results showed that the overall metabolic activity (AWCD) of soil microbial community, the metabolism of carbon sources CI, AI and MI, and the McIntosh U index under the 100 cm soil layer  were significantly larger than those under the other two thicknesses (P<0.05), while most of these indicators did not differ between 70 cm and 40 cm soil layer  (P>0.05). Results from PCA ordination plot displayed that carbon source metabolic ability of soil microbial community in 100 cm soil layer was the strongest, while that in 70 cm and 40 cm soil layer was generally similar. Soil thickness significantly affected the annual growth rate (AGR) of diameter at breast height of Ligustrum lucidumAit. AGR increased by 11% from 40 cm to 70 cm, and by 15% from 70 cm to 100 cm. The effects of soil thickness in green roof on soil microbial community function and plant growth rate had a good consistency. Reasonable soil thickness can provide suitable growing environment for roofing organisms and promote the maximization of their ecological benefits.

Key words: NO₃^- stress., omato seedlings, iron deficiency, suboptimal temperature