Seven soil cores (2.0 cm in diameter and 20 cm in depth), which were subsequently bulked, were
randomly taken from each plot in early August, 2003. All soil samples were stored in an icebox and
transferred to the laboratory for further analyses. One half of each sample was air-dried and passed
through a 2-mm sieve for chemical analyses. Another half of each fresh sample was kept at 4 ◦C for the
analyses of the microbial characteristics.