Sang Jianhui, Zhao Yixuan, Shen Yuying, Shurpali Narasinha J, Li Yuan
The State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, Qingyang National Field Scientific Observation and Research Station of Grassland Agro-Ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, 730020, China.
Grasslands and Sustainable Farming, Production Systems Unit, Natural Resources Institute Finland, Halolantie 31A, Kuopio, FI-71750, Finland.
Environ Res. 2024 May 15;249:118387. doi: 10.1016/j.envres.2024.118387. Epub 2024 Feb 7.
Achieving a balance between greenhouse gas mitigation and biomass production in grasslands necessitates optimizing irrigation frequency and nitrogen addition, which significantly influence grassland productivity and soil nitrous oxide emissions, and consequently impact the ecosystem carbon dioxide exchange. This study aimed to elucidate these influences using a controlled mesocosm experiment where bermudagrass (Cynodon dactylon L.) was cultivated under varied irrigation frequencies (daily and every 6 days) with (100 kg ha) or without nitrogen addition; measurements of net ecosystem carbon dioxide exchange, ecosystem respiration, soil respiration, and nitrous oxide emissions across two cutting events were performed as well. The findings revealed a critical interaction between water-filled pore space, regulated by irrigation, and nitrogen availability, with the latter exerting a more substantial influence on aboveground biomass growth and ecosystem carbon dioxide exchange than water availability. Moreover, the total dry matter was significantly higher with nitrogen addition compared to without nitrogen addition, irrespective of the irrigation frequency. In contrast, soil nitrous oxide emissions were observed to be significantly higher with increased irrigation frequency and nitrogen addition. The effects of nitrogen addition on soil respiration components appeared to depend on water availability, with autotrophic respiration seeing a significant rise with nitrogen addition under limited irrigation (5.4 ± 0.6 μmol m s). Interestingly, the lower irrigation frequency did not result in water stress, suggesting resilience in bermudagrass. These findings highlight the importance of considering interactions between irrigation and nitrogen addition to optimize water and nitrogen input in grasslands for a synergistic balance between grassland biomass production and greenhouse gas emission mitigation.
在草原上实现温室气体减排与生物质生产之间的平衡，需要优化灌溉频率和氮肥添加量，这二者会显著影响草地生产力和土壤一氧化二氮排放，进而影响生态系统的二氧化碳交换。本研究旨在通过一项受控的中尺度实验来阐明这些影响，该实验中狗牙根（Cynodon dactylon L.）在不同灌溉频率（每日和每6天一次）下种植，分为添加（100 kg ha）或不添加氮肥的情况；同时还对两次刈割事件中的净生态系统二氧化碳交换、生态系统呼吸、土壤呼吸和一氧化二氮排放进行了测量。研究结果揭示了由灌溉调节的土壤充水孔隙度与氮有效性之间的关键相互作用，其中氮有效性对地上生物量生长和生态系统二氧化碳交换的影响比水分有效性更为显著。此外，无论灌溉频率如何，添加氮肥后的总干物质显著高于不添加氮肥的情况。相反，随着灌溉频率和氮肥添加量的增加，土壤一氧化二氮排放量显著升高。氮肥添加对土壤呼吸组分的影响似乎取决于水分有效性，在灌溉有限（5. 4±0. 6 μmol m s）的情况下，添加氮肥会使自养呼吸显著增加。有趣的是，较低的灌溉频率并未导致水分胁迫，这表明狗牙根具有恢复力。这些发现凸显了考虑灌溉与氮肥添加之间相互作用的重要性，以便优化草原的水氮输入，从而在草地生物量生产和温室气体减排之间实现协同平衡。
