The experiment was conducted in the Biological Garden of South China Normal University, Guangzhou, China (238’2300 N,
11320’5800 E). Guangzhou has a subtropical climate, with an annual average air temperature of 21–22 C. The average air
temperatures of the coldest month (January) and the hottest month (July) were 12–14 and 28–29 C, respectively. The annual
precipitation was about 1700–1900 mm, with the wet season occurring from April to September, and the dry season from
October to March. Twenty wetland microcosms were constructed in rectangular plastic tanks (56 46 38 cm,
length width depth).