Eucalyptus plantations have replaced other (agro)ecosystems over 5.6 Mha in Brazil. While these plantations rapidly accumulate carbon (C) in their biomass, the C storage in living forest biomass is transient, and thus, longer‐term sustainability relies on sustaining soil organic matter (SOM) stocks. A significant amount of harvest residues (HR) is generated every rotation and can yield SOM if retained in the field. Yet, there is little information on how managing eucalyptus HR changes SOM dynamics. We used isotopic and molecular approaches in a 3‐yr field decomposition experiment where a native grassland has been replaced by eucalyptus plantations to assess how HR management practices influence content and chemistry of two distinct SOM fractions [particulate (POM) and mineral‐associated organic matter (MAOM)] at two soil depths (0–1 and 1–5 cm). The management practices investigated were HR removal (−R), only bark removal (−B), and retention of all HR (including bark, +B), combined with two levels of nitrogen (N) fertilization [0 (−N) and 200 (+N) kg/ha]. N fertilization inhibited HR decomposition (P = 0.0409), while bark retention had little effect (P = 0.1164). Retaining HR, especially with bark, increased POM‐C and MAOM‐C content (2.1‐ and 1.2‐fold, respectively), decreased POM‐δ¹³C (1.2‐fold), and increased inorganic N retention (1.7‐fold) compared with plots where HR had been removed. Inorganic N applications, however, diminished the positive impacts of bark retention. Although the influence of HR management was most pronounced in POM, retaining HR reduced potential soil C mineralization by up to 20%. POM and MAOM chemistry shifted over time and revealed distinct influence of HR on the formation of these fractions. We demonstrate that HR management alters SOM dynamics and that retaining HR, particularly including bark, enhances SOM retention. With continuing conversion of native grassland ecosystems to eucalyptus, long‐term sustainability will require careful HR and fertilizer management to balance total biomass harvest with sustaining belowground SOM concentrations.

中文翻译：

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保留桉树收获残余物会促进颗粒和矿物相关有机物的不同途径

桉树人工林已经取代了巴西超过5.6 Mha的其他（农业）生态系统。虽然这些人工林在其生物量中迅速积累了碳（C），但活林生物量中的C储存是短暂的，因此，长期的可持续性依赖于维持土壤有机质（SOM）种群。每次轮作都会产生大量的收获残留物（HR），如果保留在田间，则会产生SOM。然而，关于管理桉树HR如何改变SOM动态的信息很少。我们在3年的野外分解实验中使用了同位素和分子方法，在该实验中，原生草地已被桉树人工林取代，以评估HR管理实践如何影响两个不同SOM组分[颗粒（POM）和矿物相关有机物质]的含量和化学性质。 （MAOM）]在两个土壤深度（0-1厘米和1-5厘米）处。研究的管理方法是去除HR（-R），仅去除树皮（-B）和保留所有HR（包括树皮，+ B），并结合两个水平的氮（N）施肥[0（-N）和200（+ N）千克/公顷]。施氮抑制HR分解（P  = 0.0409），而树皮保留几乎没有影响（P  = 0.1164）。保持HR，尤其是树皮，增加POM-C和MAOM-C含量（2.1-和1.2倍，分别地），降低的POM-δ ¹³与去除了HR的地块相比，C（1.2倍）和增加的无机N保留（1.7倍）。然而，无机氮肥的施用减少了树皮滞留的积极影响。尽管人力资源管理的影响在POM中最为明显，但保留人力资源可以将潜在的土壤C矿化减少多达20％。POM和MAOM化学随时间推移而变化，并揭示了HR对这些馏分形成的独特影响。我们证明了人力资源管理会改变SOM动态，保留人力资源（尤其是树皮）会提高SOM保留率。随着原生草地生态系统向桉树的持续转化，长期可持续性将需要谨慎的人力资源和肥料管理，以平衡总生物量收获与维持地下SOM浓度。