陆生植物生物量分配对模拟氮沉降响应的Meta分析

A meta-analysis of the response of terrestrial plant biomass allocation to simulated N deposition

分析了陆生植物地上、地下各组织中生物量分配对氮沉降的响应,为研究大气氮沉降背景下陆地生态系统的碳、氮循环过程及植物生物量分配、立木收获、定向培育等相关研究和实践提供参考依据。共收集整理了国内外63篇论文的原始数据资料进行Meta分析(Meta-analysis),用以定量评估氮沉降对植物生物量分配的影响,并通过亚组分析进一步探讨了不同生态系统类型、植物种类、氮肥形式、施氮水平和持续时间对生物量分配的影响。结果表明,总体来看施氮会显著促进植物地上部分生物量分配,植物叶生物量和茎生物量在施氮条件下均显著增加;然而地下生物量所受促进作用要低于地上部分,表现为植物细根生物量和粗根生物量在氮输入下并没有显著变化;植物根冠比在氮沉降下显著降低;叶重比、茎重比和根重比在氮沉降下没有显著变化。此外,亚组分析结果表明生态系统类型和植物类型会显著影响植物总生物量和根冠比对氮沉降的响应,草本植物在氮沉降下的生物量累积明显优于木本,这说明短期氮沉降可能会增加草本的覆盖面积;施肥形式对根冠比的影响存在明显差异,相比于尿素,硝酸铵对植物根冠比的作用更显著;不同施氮水平显著影响地上生物量分配,中氮水平(本研究为60—120 kg hm-2a-1)促进作用最大,高氮水平(本研究为≥120 kg hm-2a-1)促进作用明显减弱,这与总生物量的变化一致,表明过高的氮沉降量将抑制植物生长;氮沉降处理时间长短对植物地上生物量的影响也存在显著差异,当施氮时间高于3年,氮沉降对地上生物量的促进作用几乎消失。总之,短期氮沉降会使植物分配更多生物量给地上部分,且氮沉降对草本植物生物量的累积作用明显优于木本,这些发现可为未来大气氮沉降背景下植物地上、地下部分碳存储、植物群落结构、植被动态等相关研究提供科学依据。

This study aimed to reveal terrestrial plant biomass allocation between aboveground and belowground tissues under nitrogen（ N） deposition and to provide a foundation for studying carbon（ C） and N cycles,stand harvests,direct cultivation in different ecosystems, and relevant research and practices regarding plant biomass allocation. Through synthesizing data from 63 peer-reviewed publications,we quantified the response of plant biomass allocation to N deposition by meta-analysis and assessed the influences on plant biomass allocation of different ecosystem types,plant species,and N forms and levels. This study found that N deposition significantly increased the aboveground biomass of plants,with plant leaf biomass and stem biomass showing an increasing trend under N application. However,although underground biomassincreased under N deposition,the increase was less than that of the aboveground biomass. Fine root biomass and coarse root biomass did not change significantly under N deposition. The root： shoot ratio decreased significantly under N application.Leaf weight ratio,stem weight ratio,and root weight ratio did not change significantly under N deposition. In addition,subgroup analysis showed that there were differences in the response of the root： shoot ratio and total biomass to N deposition for both ecosystem type and plant species. Herbaceous plant biomass accumulation increased significantly more than that of woody plants,which meant N deposition could increase the coverage of herbaceous plants. Nitrogen forms significantly affected the response of the root： shoot ratio to N application,with ammonium nitrate having a more significant effect on the root： shoot ratio than urea. The response of aboveground biomass to N application was significantly affected by the level of N application. Aboveground biomass was promoted the most at a medium N level（ 60—120 kg hm^-2a^-1） and at a high N level（ ≥120 kg hm^-2a^-1）,there was less of an effect,which was consistent with the change in total biomass. This result indicates that excessive N deposition inhibits plant growth. In addition,there were temporal differences in the effects of N application on the aboveground biomass of plants. In this study,when the N application time was longer than 3 years,the effect of N application on aboveground biomass was negligible. In conclusion,short term N application will allow most terrestrial plants to allocate more biomass to aboveground parts and the biomass accumulation of herbaceous plants is better than that of woody plants. These conclusions will provide a reasonable scientific basis for future correlative studies on plant carbon storage,community structure,tree species diversity,and vegetation dynamics under N deposition.