不同施氮水平对温带典型草原植物地上-地下生物量分配模式的影响

Effects of multi-level nitrogen addition on plant above-and below-ground biomass allocation in a typical temperate steppe

日益加剧的大气氮(N)沉降会增加陆地生态系统外源性氮输入,然而多水平氮沉降速率对生物量分配的研究相对缺乏.基于温带典型草原氮素添加梯度控制试验,分析了8个不同水平的氮素添加对生物量及其分配模式的影响.分析发现,N1,N2,N4,N8,N16,N32和N64处理分别使地上生物量(Aboveground biomass,AGB)显著增加了13.1%,27.5%,25.9%,25.5%,34.0%,54.1%和62.1%.N32和N64处理分别使地下生物量(Belowground biomass,BGB)提高123.8%和115.4%,而其他水平氮素添加处理没有显著影响BGB.在氮素添加条件下,AGB与BGB之间呈现异速生长关系且异速指数表明BGB比AGB积累增加更快,这与土壤含水量下降密切相关.研究结果不仅增强了对温带草原生物量生产响应氮沉降的认识,同时也为陆地碳循环模型构建提供科学依据.

Increasing atmospheric nitrogen(N)deposition will enhance exogenous N input to terrestrial ecosystems.However,plant biomass allocation in response to multi-level N deposition is still not clear.Here,a field manipulative experiment with N addition was conducted to examine the effect of multi-level N addition on plant biomass and its allocation(above-vs.below-ground biomass)in a typical temperate steppe,northern China.The results showed that N1,N2,N4,N8,N16,N32 and N64 significantly increased aboveground biomass(AGB)by 13.1%,27.5%,25.9%,25.5%,34.0%,54.1%and 62.1%respectively.However,belowground biomass(BGB)was only stimulated under high-level N addition treatments(i.e.123.8%for N32,115.4%for N64).Under the long-term N addition treatment,there was an allometric relationship between AGB and BGB in this study,and the allometric exponent indicated that BGB increased faster than AGB resulting from the decreased soil moisture.The findings not only enhance the understanding of plant biomass allocation in response to N deposition in the temperate steppe,but also provide scientific basis for the construction of terrestrial carbon cycling model.