大气CO2浓度升高和氮肥施用对三江平原湿地小叶章生物量及根冠比的影响

Effects of Elevated CO_2 Concentration and Application of N Fertilizer on Biomass and Root/Shoot Ratio of Calamagrostis angustifolia in Typical Wetland of Sanjiang Plain

利用开顶箱薰气室(open-top chamber)试验装置,研究了不施氮(NN)、施常氮(MN,5g.m-2)和施高氮(HN,15g.m-2)3个氮素水平下大气CO2浓度升高对小叶章(Calamagrostis angustifolia)生物量和根冠比的影响。结果表明,大气CO2浓度升高对小叶章生物量的影响因生长期而异。大气CO2浓度升高对小叶章地上生物量的促进作用主要表现在生长前期,拔节期和抽穗期地上生物量较正常大气CO2浓度增加12.42%～22.60%,而腊熟期和成熟期仅增加3.11%～12.97%;大气CO2浓度升高对小叶章地下生物量的促进作用在生长后期表现明显,除拔节期外,小叶章地下生物量增加17.63%～42.20%。小叶章生物量和根冠比对大气CO2浓度的响应与供N水平有关。在HN水平下,大气CO2浓度升高使小叶章生物量和根冠比明显增加,在NN条件下促进作用则不显著。小叶章根冠比明显增加主要是地下生物量显著增长引起的。

A field experiment using OTC （open-top chamber）was carried out with treatments different in nitrogen supply （0,5,15 g·m^-2） and CO2 level（350 vs 700μmol . mol^-1 ） to investigate effects of the treatments on biomass and root/ shoot ratio （R/S） of Calamagrostis angustifolia. Results show that effect of elevated CO2 on biomass differed in the growth stage. Elevation of CO2 level stimulated growth of the biomass of the above ground parts of the plant mainly at its early growth stage. It increased the biomass by 12.42% -22.60% at the jointing and heading stages in all the nitrogen treatments, and by 3.11%-12.97% at the dough and maturing stages. The response of the underground parts,however,was obvious at the late growth stages,varying in the range of 17.63% -42.20% except at the jointing stage. The response of biomass and R/S to elevated CO2 was related to nitrogen level. The promoting effect of elevated CO2 on biomass and R/S of Calamagrostis angustifolia was only significant in treatments higher in nitrogen supply, while it was not in CK. The stimulating effect of CO2 on underground biomass is the main cause to increased R/S.