Given the ongoing climate change, estimating the amount of less degradable plant compounds that can be stored in the soil, such as lignin, is a topic of primary importance. There are few methods applicable to soils for the determination of lignin, such as the copper oxide (CuO) oxidation method (CuOL). Acetyl bromide spectrophotometric lignin (ABSL) could be a valid alternative providing information that is less detailed compared to CuOL, but it offers data on the bulk amount of lignin and may offer a valid, fast, and cheap alternative to the CuO method. The aim of this work was to compare ABSL with the CuO method on several soils receiving plant residues from different trees. Mineral soil samples from 0 to 10 cm depth were obtained from a former agricultural site in northern Italy (Brusciana, Tuscany), where different tree plantations were established 22 years ago. The plantations were white poplar and common walnut, which were also intercropped with other species such as hazelnut, Italian alder, and autumn olive. Soil samples under these plantations were also compared to soil under an adjacent agricultural field. In general, the amount of lignin in the afforested stands was approximately double than in the agricultural field as determined by either method. The two methods returned a largely different scale of values due to their different mechanisms of action. The acid-to-aldehyde ratio of syringyl structural units highlights that forest plantation provides a plant input material that is more slowly oxidatively degraded compared to arable soil. A linear mixed model proved that ABSL performed well in relation to CuOL, especially when considering the random variation in the model given by the plantation field design. In conclusion, ABSL can be considered a valid proxy of soil C pool derived from structural plant component, although further analyses are needed.

中文翻译：

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快速分光光度法替代CuO氧化评估不同树种覆盖土壤中的木质素

考虑到持续的气候变化，估算木质素等可降解的植物化合物（例如木质素）的储存量是最重要的主题。很少有适用于土壤中测定木质素的方法，例如氧化铜（CuO）氧化法（CuOL）。乙酰溴分光光度法木质素（ABSL）可能是一种有效的替代品，提供的信息比CuOL要少，但是它提供了木质素的大量数据，并且可以提供一种有效，快速且廉价的替代CuO方法。这项工作的目的是将ABSL和CuO方法在几种接受不同树种植物残渣的土壤上进行比较。深度为0至10厘米的矿物质土壤样品是从意大利北部（布鲁斯亚那，托斯卡纳）的一个以前的农业地点获得的，22年前建立了不同的人工林。人工林为白杨树和普通胡桃木，也与其他物种（如榛子，意大利al木和秋天的橄榄）间作。还比较了这些人工林下的土壤样品与邻近农田下的土壤样品。通常，按照上述两种方法测定，绿化林分中木质素的含量约为农田中的两倍。两种方法由于其不同的作用机理而返回的值规模差异很大。丁香基结构单元的酸对醛比率表明，与可耕种土壤相比，人工林提供的植物输入材料的氧化降解速度更慢。线性混合模型证明ABSL相对于CuOL表现良好，特别是在考虑人工林设计给出的模型中的随机变化时。总之，尽管需要进一步的分析，但ABSL可以被认为是由结构性植物成分衍生的土壤碳库的有效替代物。