氮、磷添加对亚高寒草甸地上生物量的影响

Effects of nitrogen and phosphorus addition on the plant aboveground biomass on a sub-alpine meadow

通过生长季后期及初期分别设置N-P养分添加实验,探讨甘南亚高寒草甸群落及不同功能群生物量对养分添加的响应,并确定提高生产力的最佳养分添加量。结果显示,随着养分添加量的增加,群落生物量表现出先升后降的趋势。二次项拟合亚高寒草甸最佳N添加量为16.58 g·m^(–2),最佳P添加量为4.50 g·m^(–2),最佳N-P共添加量为N=18.47 g·m^(–2)、P=7.39 g·m^(–2)。N、P养分添加存在交互作用,对群落生物量的促进作用N-P共添加>N添加>P添加。各添加处理下禾草均能做出积极的响应,其中N-P共添加对禾草类生物量的促进作用最大;杂草生物量随生长季后期养分添加量下降,而随生长季初期养分添加量表现为先升后降的趋势;莎草生物量在单一N添加处理下随添加量上升;P添加促进、而N添加及N-P共添加抑制豆科生物量的积累。

To examine response of different plant functional group biomass and community biomass to nutrient addition and determine the optimal nutrient level of plant productivity on a sub-alpine meadow, we conducted N-P addition experiments in the late and early growing season in Hezuo of Gansu Province. Results showed that with the increase of the amount of nutrients, community biomass increased firstly, and then decreased. The optimum amount of N addition and P addition was 16.58 g·m^-2 and 4.50 g·m^-2 respectively, and the optimum amount of N-P co-addition was N = 18.47 g·m^-2 and P = 7.39 g·m^-2 respectively according to the binomial regression fitting. Interaction of N and P addition was found and the order of positive effect on the community biomass was N-P co-addition 〉 N addition 〉 P addition. Graminoids biomass had a positive response to all the addition treatment, in which the effect of N-P co-addition was the strongest among all nutrient addition treatments. With the amount of nutrients forbs biomass in the early growing season firstly increased and then decreased, but decreased in the latter of the growing season. Sedge biomass, similar with the graminoids, increased with the amount of N addition. P addition favored the increase of legume biomass, while N addition and N-P co-addition, inhibited the legume.