Land-use change for bioenergy production can release greenhouse gases (GHG) through disturbance of soil carbon (C) pools, but use of native species with extensive root systems as bioenergy crops may help mitigate GHG emissions by enhancing soil C sequestration. Here, we investigated how (1) fertilization, (2) plant species and cultivars, and (3) inter- and intra-specific diversity affect soil C and N accumulation five growing seasons after conversion of an old-field dominated by C₃ grasses to a grassland dominated by C₄ perennial grasses managed for biofuel production. We manipulated diversity at both the species- and cultivar level, and applied nitrogen (N) at two levels (0 and 67 kg ha⁻¹). Establishment of C₄ grass treatments on soils that supported C₃ pasture grasses for 36 years enabled us to use the natural abundance C isotope ratio technique to estimate the contribution of new C₄ plant-derived C to soil organic matter pools. Our study yielded three main results: 1) annual fertilization did not significantly affect soil C and N concentrations after five growing seasons; 2) increasing inter- and intra-specific diversity did not significantly increase soil C and N concentrations; 3) cultivar- and species identity influenced C₄-derived C and total soil C concentrations: big bluestem dominated stands exhibited greater soil C accrual relative to stands dominated by switchgrass and mixed-species treatments. Future research is needed to further assess how big bluestem can aid in the sustainable provisioning of second generation biofuel feedstocks.

用于生物能源生产的土地用途变化可通过扰动土壤碳（C）库释放温室气体（GHG），但是将具有广泛根系的本地物种用作生物能源作物可通过增强土壤固碳来减轻温室气体的排放。在这里，我们研究了（1）施肥，（2）植物种类和栽培品种，以及（3）种间和种内多样性对以C ₃草为主的老田转化后五个生长季节对土壤C和N积累的影响。到以C ₄多年生草为主的草地上进行生物燃料生产。我们在物种和品种水平上都控制了多样性，并在两个水平（0和67 kg ha ^-1）下施用了氮（N ）。建立C ₄在支持C ₃牧草的土壤上进行草处理36年，使我们能够使用自然丰度C同位素比率技术估算新的C ₄植物来源的C对土壤有机质库的贡献。我们的研究得出了三个主要结果：1）在五个生长季节后，年度施肥不会显着影响土壤中的碳和氮浓度；2）增加种间和种内多样性不会显着增加土壤碳和氮的浓度；3）品种和物种身份影响C ₄派生的碳和总土壤碳浓度：相对于以柳枝switch和混合物种处理为主的林分，大的蓝茎为主的林分表现出更大的土壤碳累积。需要进一步的研究来进一步评估大型蓝茎可以如何帮助可持续地供应第二代生物燃料原料。