施加生物质炭对毛竹林温室气体排放和固碳能力的影响

Biochar addition may improve the nutrient utilization, promote plant growth, decrease the emissions of greenhouse gases (GHGs), and increase soil carbon storage, which plays an important role in mitigating climate change and thus receives increasing attention. Being a key bamboo species, Moso bamboo (Phyllostachys pubescens) forests in China cover 70% of the country's bamboo forest area and 80% of the total global area of Moso bamboo. With rapid growth and strong carbon sequestration capacity, Moso bamboo forest are receiving increasing attention on the large potential in global carbon uptake and the unique role in mitigating climate change. Intensive management tends to increase the carbon sequestration of Moso bamboo forest ecosystem via improving the productivity of forest, but it also arouses the GHGs emissions, which partly offsets the carbon benefits. In this project, we intend to investigate the change in carbon storage and GHGs flux in Moso bamboo forest ecosystem under different level of Biochar addition, and demonstrate the potential effect of Biochar addition on net carbon uptake of Moso bamboo forest. The dynamics of biomass carbon, soil organic carbon, and soil GHGs emissions will be observed to reveal the process mechanism of Moso bamboo forest carbon uptake under Biochar addition. The contents of N and P, and C:N ratios and N:P ratios in different parts of Moso bamboo will be measured to elucidate the possible internal mechanism of productivity change of Moso bamboo forest. The abiotic factors, including NH4+-N and NO3- - N, C:N ratio and pH in soil, and biotic factors, including the composition and structure of soil microbes, will be also analyzed to reveal the possible mechanism of Biochar addition effects on GHGs flux in soil. Finally, the relationship model about Biochar addition level and net carbon uptake effect of Moso bamboo forest ecosystem will be set up to forecast the potential role of Moso bamboo forest ecosystem in mitigating climate change. This study will contribute to the comprehensive understand on carbon benefits of Biochar addition and climate policy-making in our country.

施加生物质炭可以提高养分利用率，促进植物生长，减少温室气体排放，增加土壤碳储量，在缓解气候变化中发挥着重要作用，被认为是人类应对全球气候变化的一条重要途径，日益受到关注。作为我国分布面积最广、经济价值最高的竹种，毛竹生长速度快，固碳能力强，在固碳减排、减缓气候变化中的独特作用日益受到重视。当前，全国约有一半面积的毛竹林实行了集约经营，这一方面提高了毛竹林的生产力，另一方面也促进了土壤温室气体的排放，削弱了毛竹林生态系统整体上的固碳能力。本项目拟研究施加生物质炭对集约经营毛竹林地CO2、CH4和N2O三种温室气体通量、土壤有机碳储量及林分生产力的影响，并从植物和土壤氮、磷、C/N比、pH值变化等非生物因素和土壤微生物的变化等生物因素角度揭示生物质炭作用于毛竹林地温室气体通量和林分生产力的内在机理，探讨施加生物质炭增强毛竹林固碳功能的潜力，为提高我国森林特别是人工林的固碳能力提供科学依据。

生物质炭显著增加了土壤微生物量和多样性（P<0.05），降低了氮沉降对毛竹林土壤微生物量的积极作用，缓解了氮沉降对土壤细菌多样性的消极作用。生物质炭与氮沉降复合作用使土壤微生物量降低了6.9%-25.7%，多样性增加了5.9%-9.7%。生物质炭显著促进了纤维素酶和硝酸还原酶活性（P <0.01），显著抑制了蔗糖酶、脲酶和酸性磷酸酶活性(P <0.05 )，对过氧化氢酶活性影响不显著；生物质炭施加极显著减缓了氮沉降对蔗糖酶、脲酶的抑制作用(P <0.001 )，对其他5种酶没有显著影响。生物质炭显著增加了土壤CO2通量，对CH4和N2O通量影响不显著。研究结果为全面认识毛竹林土壤生态系统对添加生物质炭的响应提供了重要参考。