Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark.
Department of Agroecology, Aarhus University, Tjele, Denmark.
Glob Chang Biol. 2023 Oct;29(19):5677-5690. doi: 10.1111/gcb.16870. Epub 2023 Jul 31.
Cover crops increase carbon (C) inputs to agricultural soils, and thus have the potential to mitigate climate change through enhanced soil organic carbon (SOC) storage. However, few studies have explored the fate of belowground C inputs associated with varying root traits into the distinct SOC pools of mineral-associated organic carbon (MAOC) particulate organic carbon (POC). Therefore, a packed 0.5 m column trial was established with 0.25 m topsoil and 0.25 m subsoil with four cover crops species (winter rye, oilseed radish, chicory, and hairy vetch) known to differ in C:N ratio and root morphology. Cover crops were CO -labeled for 3 months, and then, half of the columns were sampled to quantify root and rhizodeposition C. In the remaining columns, plant shoots were harvested and the undisturbed soil and roots were left for incubation. Bulk soil from both sampling times was subjected to a simple fractionation scheme, where C in the <50 and >50 μm fraction was assumed to represent MAOC and POC, respectively. The fast-growing rye and radish produced the highest root C. The percentage loss of C via rhizodeposition (%ClvR) showed a distinct pattern, with 22% for the more branched roots (rye and vetch) and 6%-8% for the less branched roots (radish and chicory). This suggests that root morphology plays a key role in determining rhizodeposition C. After 1 year of incubation at room temperature, the remaining MAOC and POC were positively correlated with belowground inputs in absolute terms. However, topsoil MAOC formation efficiencies (cover crop-derived MAOC remaining as a share of belowground inputs) were higher for vetch and rye (21% and 15%, respectively) than for chicory and radish (9% and 10%, respectively), suggesting a greater importance of rhizodeposition (or indirectly, root morphology) than solely substrate C:N ratio for longer term C stabilization.
覆盖作物增加了农业土壤中的碳 (C) 输入，因此通过增强土壤有机碳 (SOC) 储存，具有缓解气候变化的潜力。然而，很少有研究探索与不同根特性相关的地下 C 输入到矿物结合有机碳 (MAOC) 颗粒有机碳 (POC) 不同 SOC 库中的命运。因此，建立了一个填充 0.5m 柱试验，用 0.25m 表土和 0.25m 底土，用四种覆盖作物物种（冬黑麦、油菜籽、菊苣和毛野豌豆），它们在 C:N 比和根形态上有所不同。覆盖作物用 13CO2 标记了 3 个月，然后，一半的柱子被取样以量化根和根分泌物中的 C。在剩余的柱子中，收获植物地上部分，未扰动的土壤和根系被留下进行培养。两次采样的原状土壤都进行了简单的分馏方案，<50 和 >50μm 部分中的 C 分别被认为代表 MAOC 和 POC。生长较快的黑麦和油菜籽产生的根 C 最多。通过根分泌物损失的 C 的百分比（%ClvR）表现出明显的模式，具有更多分支的根（黑麦和野豌豆）为 22%，而分支较少的根（油菜籽和菊苣）为 6%-8%。这表明根形态在决定根分泌物 C 方面起着关键作用。在室温下培养 1 年后，剩余的 MAOC 和 POC 与地下输入呈正相关，绝对值。然而，在黑麦和野豌豆中，MAOC 的形成效率（覆盖作物衍生的 MAOC 作为地下输入的一部分）较高（分别为 21%和 15%），而在菊苣和油菜籽中较低（分别为 9%和 10%），这表明根分泌物（或间接的，根形态）比仅底物 C:N 比对于更长时间的 C 稳定更为重要。
