生物质炭-根系互作驱动土壤碳矿化激发效应的C源敏感性

Recent studies have showed that biochar by artificially adding is one reliable way to reduce atmospheric carbon dioxide concentrations, indicating stable biochar changs the soil aggregate structure, water absorption and microbial activity to change natural soil organic carbon short-term turnover by the priming effect. Biochar may sorb the root-derived labile C and root may influnce the stability of biochar. However, there is a knowledge gap on biochar-root interaction driving the priming effects on soil organic carbon and recent root-derived C sensibility under field conditions. In this study, biochar-root interactions drive the priming of soil organic carbon associated with the C sources sensibility, the dynamic of the total soil organic carbon, the root soluble carbon, soil respiration, soil microbial community structure and soil environment will be analyzed by isotope δ13C and closed chamber method following artificially adding biochar in field test, to explore the influence of biochar-root interactions to the direction, persistence and extent of soil native organic carbon priming and quantize the contribution of three C sources mineralization to the soil native carbon mineralization and its stability. The objectives of the study are to reveal the priming effect of biochar to natural soil carbon mineralization and interaction mechanism by artificially adding biochar and clarify soil carbon self-circulation model, which will help to provide a scientific basis for subtropical bamboo forest reasonable operating, with laying the foundation for long-term forest ecosystem C sequestration and providing choose, reference for climate change.

研究表明人为添加生物质炭是降低大气CO2浓度的可靠方法之一，稳定的生物质炭通过激发效应改变土壤团聚体结构、水分吸附和微生物活性等引起原位土壤有机碳周转改变。生物质炭可吸收根系来源的易溶碳，根系则影响生物质炭的稳定性。然而，野外生物质炭-根系互作驱动土壤有机碳的激发效应及根系-C源敏感性理解不够。开展野外生物质炭还林试验，结合同位素δ13C示踪和静态箱法，研究3种C源（生物质炭、土壤、根系）对土壤碳矿化激发效应的敏感性，测定土壤有机碳、土壤呼吸、根系可溶性碳、土壤微生物活性和土壤环境等动态，分析生物质炭-根系互作对土壤碳激发效应的方向、大小和持久性的影响，量化3种C源对原位土壤碳排放的贡献及稳定性，揭示生物质炭添加对原位土壤碳互作的激发效应机制，阐明生物质炭还林对竹林土壤碳元素的自循环模式，旨在为亚热带竹林合理经营提供科学依据，为森林生态系统长期碳吸存奠定基础，为应对气候变化提供选择和参考。

研究表明人为添加生物质炭是降低大气CO2浓度的可靠方法之一，稳定的生物质炭通过激发效应改变土壤结构、水分吸附和微生物活性等引起原位土壤有机碳周转改变；然而，生物质炭还林对森林原位土壤碳激发效应的方向、大小、持久性和微生物响应机制还不清楚。开展野外生物质炭还林试验，研究生物质炭-根系互作对原位土壤碳排放及温度敏感性、土壤微生物多样性、群落结构、酶活性及影响及碳源敏感性，对竹林土壤碳元素的自循环模式和亚热带竹林合理经营提供科学依据。结果表明: 生物质炭添加降低土壤呼吸速率且随着添加量的增加土壤呼吸降低量变小；与对照相比, LB、MB、HB处理下土壤呼吸速率分别降低2.33%–54.72%、1.28%–44.21%和0.09%–39.22%，年均土壤水分含量分别增加0.62%–75.58%、0.87%–48.18%和0.68%–74.73%。与对照相比，添加第一年和第二年后LB中总生物量分别增加9.1%和3.5%，MB中第一年增加22.0%，第二年降低9.0%，HB中分别增加7.1%和7.8%。生物质炭添加明显降低HB处理的Chao丰度、细菌的Shannon's 指数，明显增加细菌的Simpson's指数、10–20 cm土壤微生物量、0–10 cm土壤层多酚氧化酶活性、蔗糖酶和脲酶活性。年累积土壤碳排放明显与0–10 cm土壤总微生物量、G–、细菌、丛枝菌根真菌呈正相关。生物质炭添加增加团聚体的稳定性，仅中浓度生物质炭添加增加团聚体有机碳含量，且与生物质炭交互作用显著。生物质炭自身分解对土壤碳矿化贡献为0.8%–1.1%，生物质炭添加下根系贡献为3.1%–4.0%。总之，低浓度生物质炭添加通过增加10–20 cm土壤微生物量和土壤酶活性，改变微生物群落结构和生物多样性，明显降低土壤碳排放，为森林生态系统长期碳吸存奠定基础，为应对气候变化提供选择和参考。