Poeplau Christopher, Begill Neha, Liang Zhi, Schiedung Marcus
Thünen Institute of Climate-Smart Agriculture, Bundesallee 68, 38116 Braunschweig, Germany.
Department of Agroecology, Aarhus University, Blichers Allé 20, Tjele, 8830 Denmark.
Plant Soil. 2023;491(1-2):439-456. doi: 10.1007/s11104-023-06127-y. Epub 2023 Jun 21.
Understanding the fate and residence time of organic matter added to soils, and its effect on native soil organic carbon (SOC) mineralisation is key for developing efficient SOC sequestration strategies. Here, the effect of litter quality, particularly the carbon-to-nitrogen (C:N) ratio, on the dynamics of particulate (POC) and mineral-associated organic carbon (MAOC) were studied.
In a two-year incubation experiment, root litter samples of the C4-grass with four different C:N ratios ranging from 50 to 124 were added to a loamy agricultural topsoil. In an additional treatment, ammonium nitrate was added to the C:N 124 litter to match the C:N 50 litter input ratio. Soils were size-fractionated after 6, 12 and 24 months and δC was measured to determine the proportion of new and native POC and MAOC. Litter quality was further assessed by mid-infrared spectroscopy and compound peak analysis.
Litter quality strongly affected SOC dynamics, with total SOC losses of 42.5 ± 3.0% in the C:N 50 treatment and 48.9 ± 3.0% in the C:N 124 treatment after 24 months. Largest treatment effects occurred in mineralisation of native MAOC, which was strongly primed by litter addition. The N amendment in the C:N 124 treatment did not alleviate this potential N mining flux.
Litter quality plays a major role in overall SOC dynamics, and priming for N mining from the MAOC pool could be a dominant mechanism. However, adding N did not compensate for poor litter quality, highlighting the role of litter quality beyond stoichiometric imbalances.
了解添加到土壤中的有机物质的归宿和停留时间，及其对原生土壤有机碳（SOC）矿化的影响，是制定有效的SOC固存策略的关键。在此，研究了凋落物质量，特别是碳氮比（C:N），对颗粒有机碳（POC）和矿物结合有机碳（MAOC）动态的影响。
在一项为期两年的培养实验中，将四种不同C:N比（范围为50至124）的C4草根系凋落物样本添加到壤质农业表土中。在另一处理中，向C:N为124的凋落物中添加硝酸铵，以使其与C:N为50的凋落物输入比例相匹配。在6、12和24个月后对土壤进行粒度分级，并测量δC以确定新的和原生的POC和MAOC的比例。通过中红外光谱和复合峰分析进一步评估凋落物质量。
凋落物质量强烈影响SOC动态，24个月后，C:N为50的处理中总SOC损失为42.5±3.0%，C:N为124的处理中为48.9±3.0%。最大的处理效应发生在原生MAOC的矿化过程中，凋落物添加对其有强烈的激发作用。C:N为124的处理中的氮添加并未减轻这种潜在的氮开采通量。
凋落物质量在总体SOC动态中起主要作用，从MAOC库中开采氮的激发作用可能是一个主导机制。然而，添加氮并不能弥补凋落物质量差的问题，这突出了凋落物质量超出化学计量失衡的作用。
