Data from: Root volume distribution of maturing perennial grasses revealed by correcting for minirhizotron surface effects

Aims: Root architecture drives plant ecology and physiology, but current detection methods limit understanding of root placement within soil profiles. We developed a statistical model of root volume along depth gradients and used it to infer carbon storage potential of land-use changes from conventional agriculture to perennial bioenergy grasses.

Methods: We estimated root volume of maize-soybean rotation and three perennial grass systems (Miscanthus × giganteus, Panicum virgatum, tallgrass prairie mix) by Bayesian modeling from minirhizotron images, correcting for small images and near-surface underdetection. We monitored seasonal and inter-annual changes in root volume distribution, then validated our estimates against root mass from core samples.

Results: The model explained 29% of root volume variation and validated well against core mass. Seventh-year perennials had greater belowground biomass than maize-soybean both in total (11-16×) and throughout the profile (2-17× at every depth < 120 cm). Perennials’ relative depth allocations were stable over time, while total root volume increased through five years. In 2012 a historically hot, dry summer damaged maize while perennials appeared resilient, suggesting their large-deep root systems aid drought resistance.

Conclusions: Perennial root systems are large, deep, and persistent. Converting row crops to perennial bioenergy grasses likely sequesters carbon in a large, potentially very stable, soil pool.

研究目的：根系构型调控植物生态与生理过程，但现有检测手段制约了学界对根系在土壤剖面中分布格局的认知。本研究构建了沿深度梯度分布的根系体积统计模型，并借此推演了传统农业用地转为多年生能源草本作物后的碳储存潜力。
研究方法：本研究基于微根窗（minirhizotron）图像，通过贝叶斯建模估算了玉米-大豆轮作系统与3种多年生草本系统（芒草（Miscanthus × giganteus）、柳枝稷（Panicum virgatum）、高草草原混合群落）的根系体积，并对小型图像误差与近地表检测偏差进行校正。本研究还监测了根系体积分布的季节与年际动态，随后利用土芯样品的根系干重对估算结果进行验证。
研究结果：本模型可解释29%的根系体积变异，且与土芯样品的根系干重验证结果吻合良好。种植第七年的多年生草本系统的地下生物量显著高于玉米-大豆轮作系统：总地下生物量为后者的11~16倍，在整个土壤剖面（<120 cm的各土层）中则为2~17倍。多年生草本的根系相对深度分配格局随时间保持稳定，而总根系体积在种植前五年持续提升。2012年为历史罕见的高温干旱夏季，玉米遭受严重损伤，但多年生草本表现出较强的抗逆性，这表明其发达的深根系统有助于提升耐旱性。
研究结论：多年生草本的根系系统庞大、分布深邃且稳定性强。将一年生条播作物改造为多年生能源草类种植，有望将碳封存于规模庞大且稳定性极高的土壤碳库中。