氮添加对内蒙古草原植物地上和地下碳氮磷化学计量学特征的影响

Nitrogen addition alters aboveground C:N:P stoichiometry of plants but not for belowground in an Inner Mongolia grassland

氮沉降对生态系统功能和过程具有显著影响。已有研究表明氮添加会影响植物叶片C:N:P化学计量特征。然而,氮添加对植物根系C:N:P化学计量特征影响的研究罕有报道。本论文的主要目的是对比氮添加对草原植物群落地上和地下C:N:P化学计量特征的影响。我们在内蒙古锡林郭勒草原开展了一个7年的氮添加实验,该实验包括6个处理,分别是对照:control;N1:0.4 mol·m-2 N;N2:0.8 mol·m^(-2) N;N3:1.6 mol·m^(-2) N;N4:2.8 mol·m^(-2) N;N5:4 mol·m^(-2) N,每个处理6次重复。我们测量并分析了植物地上、地下生物量和C:N:P化学计量特征。研究结果表明,氮添加会导致植物群落地上部分碳浓度降低,氮浓度和磷浓度升高,C:N和C:P比值降低,N:P升高,而且地上碳、氮、磷库均因施氮而增加。然而,氮添加对0-10,10-30,30-50和50-100 cm 4个土层的地下部分碳、氮、磷浓度、比例、库和化学计量特征没有显著影响。综上所述,氮添加会显著改变植物群落地上部分C:N:P化学计量特征,进而影响草地生态系统的功能和过程,但对地下C:N:P化学计量特征几乎没有影响。

Nitrogen(N)deposition exhibits significant impacts on ecosystem functions and processes.Previous studies have indicated that N addition has an impact on the stoichiometry of plant leaf C:N:P ratios.However,few studies have focused on effects of N addition on belowground systems.This study aims to examine the impact of 7 years of N addition on above-and belowground C:N:P stoichiometry at plant community level in a temperate grassland located in Inner Mongolia.A 7-year field N addition experiment was conducted,which included six treatments:Cont:control;N1:0.4 mol·m^(-2) N;N2:0.8 mol·m^(-2) N;N3:1.6 mol·m^(-2) N;N4:2.8 mol·m^(-2) N;N5:4 mol·m^(-2) N with six replicates.Above-and belowground plant biomass and C:N:P stoichiometry were measured and analyzed.Our results showed that N addition resulted in a reduction of aboveground C concentration,but an increase in aboveground N and P concentrations,with a decrease in C:N and C:P ratios and an increase in N:P ratio.Furthermore,the aboveground C,N,and P pools all exhibited an increase as a result of N addition.However,N addition did not have any significant effect on belowground C,N,P concentrations,ratios,pools,or stoichiometric characteristics in the soil layers of 0-10,10-30,30-50,and 50-100 cm.These results suggest that increasing levels of N deposition significantly alter the aboveground C:N:P stoichiometry at the plant community level,which may affect functions and processes in the grassland ecosystem,but have little effect on belowground C:N:P stoichiometry.