利用开顶箱薰气室,设置正常大气CO2浓度（350μmol.mol-1）、高CO2浓度（700μmol.mol-1）2个CO2水平和不施氮（0 g N.m-2）、中氮（5 g N.m-2）和高氮（15 g N.m-2）3个氮素水平,研究CO2浓度升高和氮肥施用对三江平原草甸小叶章生长的影响.结果表明：随着CO2浓度升高,小叶章物候期提前,其中抽穗期提前1~2 d,成熟期提前3 d;不施氮、中氮和高氮水平下,CO2浓度升高使小叶章的分蘖分别增加8.2%（P〈0.05）、8.4%（P〈0.05）和5.5%（P〉0.05）;在小叶章生长初期,CO2浓度升高对其生物量的增加有促进作用,拔节期和抽穗期小叶章地上生物量分别增加12.4%和20.9%（P〈0.05）;生长后期则对小叶章地下生物量的促进作用增大,腊熟期和成熟期的地下生物量分别增加20.5%和20.9%（P〈0.05）.小叶章生物量对高浓度CO2的响应与供氮水平有关,供氮充足条件下,高浓度CO2对生物量的促进效应更大.
The carbon (C),nitrogen (N) and phosphorus (P) variations of a temperate wetland soil under continuous cultivation for 40 yr were determined and evaluated in the Sanjiang Plain,Northeast China.The results showed that the soil organic carbon (SOC) and total nitrogen (TN) contents in each soil layer decreased sharply after cultivation for 2-3 yr,and exhibited minor differences after cultivation for 11 yr,which showed an exponential decline curve with the increase of cultivation years.The reduction rates of carbon and nitrogen reserves were 14.79% and 28.53% yr-1 at the initial reclamation stages of 2-3 yr and then decreased to 2.02-3.08% yr-1 and 1.98-2.93% yr-1 after cultivation for 20 yr,respectively.Soil total phosphorus (TP) reserves decreased within cultivation for 5 yr,and then gradually restored to the initial level after cultivation for 17 yr.Both SOC and TN could be restored slightly when the farmland was left fallow for 8 yr after reclamation for 11 yr,whereas TP had no significant difference.These results demonstrated that wetland cultivation was one of the most important factors influencing on the nutrient fate and reserves in soil,which could lead to the rapid nutrient release and slow restoration through abandon cultivation,therefore protective cultivation techniques preventing nutrients from loss should be immediately established after wetland reclamation.
