生物炭添加对不同水氮条件下芦苇生长和氮素吸收的影响

生物炭能改良土壤从而促进植物生长和氮素吸收,但其作用效果是否受水氮条件的影响尚不清楚。以湿地植物芦苇为研究对象,在3种氮添加水平（无添加,30 kg hm^-2 a^-1和60 kg hm^-2 a^-1）和两种水分（淹水和非淹水）条件下分别进行生物炭添加和不添加处理,结果表明：（1）生物炭添加能促进芦苇根系生长,在非淹水条件下根系生物量增加了40.5%,在淹水条件下根系生物量增加了20.1%。（2）生物炭添加能促进非淹水条件下芦苇的氮素吸收,能提高淹水条件下芦苇的氮素生产力。（3）生物炭添加加剧了土壤氮素损失,且在非淹水高氮条件下作用最强,可能是由于生物炭促进了芦苇的氮素吸收。芦苇氮素吸收速率与土壤氮损失之间存在显著的正相关关系。因此,在添加生物炭时,需要考虑土壤水分状况和氮素富集程度以及植物的氮素吸收偏好。该研究结果可为生物炭在湿地生态系统中的应用提供参考。

Effects of biochar addition on growth and nitrogen absorption of Phragmites australis under different water and nitrogen conditions

Nitrogen is an essential element for plant growth and is closely related to plant life activities. In most terrestrial ecosystems, plant growth is limited by nitrogen availability. Therefore, it is important to improve plant productivity in terrestrial systems by increasing the nitrogen uptake capacity of plants. Biochar is regarded as a kind of "soil conditioner" produced by pyrolysis of biomass under high temperature and hypoxia conditions. It has attracted more and more attention because of its important role in promoting crop yield, reducing greenhouse gas emissions and environmental pollution control in recent years. Most previous studies have applied biochar in dryland ecosystems, but few in wetland ecosystem. Though biochar has been proved to be beneficial of plant growth and nitrogen uptake, but whether it is influenced by different nitrogen availability and water conditions is still unclear. Therefore, we conducted a greenhouse experiment to investigate the effects of biochar addition on the growth and nitrogen absorption of Phragmites australis with three nitrogen additions (no addition, 30 kg hm^-2 a^-1, 60 kg hm^-2 a^-1) and two water treatments (inundation and no inundation). The results showed that:(1) biochar addition promoted the root growth of P. australis, increased the root biomass by 40.5% in the non-flooded treatment and by 20.1% in the flooded treatment, but have no significant effects on biomass of other parts and total biomass. (2) Biochar addition could improve the nitrogen absorption rate in the non-flooded condition, increased the nitrogen absorption rate by 23% in average. Biochar addition also enhanced the nitrogen productivity of P. australis in the flooded condition by 22% in average. (3) Biochar significantly decreased the soil ammonium-N, nitrate-N and mineral nitrogen concentrations, increased the soil nitrogen loss, and the effects were the strongest in the non-flooded and high nitrogen treatments because biochar promoted nitrogen absorption rate of P. australis. There was a significantly positive correlation between nitrogen absorption rate of P. australis and soil nitrogen loss. Our study shows that biochar has different effects on growth, nitrogen absorption and utilization of P. australis in different soil nitrogen availability and water treatments, and the difference may be related to the absorption preference of plants on different nitrogen chemical forms. Therefore, it is necessary to comprehensive balance soil water status, nitrogen enrichment and nitrogen absorption preference of plants when applying biochar in field. This result can practically provide scientific support for the application of biochar in the wetland ecosystem.