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The patchiness of soil 13C versus the uniformity of 15N distribution with geomorphic position provides evidence of erosion and accelerated organic matter turnover
Agriculture, Ecosystems & Environment ( IF 6.6 ) Pub Date : 2023-06-08 , DOI: 10.1016/j.agee.2023.108616
Mitra Ghotbi, Ruhollah Taghizadeh-Mehrjardi, Claudia Knief, Marjan Ghotbi, Angela D. Kent, William R. Horwath

Farming on hillslopes often affects the accumulation and loss of soil organic matter (SOM) depending on slope position and cropping patterns. Most hillslope studies focus on soil movement to characterize SOM turnover under erosive conditions. In this study, we trace erosion and characterize agronomic practices erosive impacts on SOM translocation and transformation along geomorphic positions. To achieve this, we assessed the horizontal distribution (upper 15 cm) and vertical distribution (to 100 cm profiles) of soil δ15N and δ13C isotope abundance individually. We mapped the spatial distribution of δ13C, δ15N, and SOM turnover indices as a novel approach to tracing erosion and degradation of SOM in the field. Except for tillage (conventional vs. reduced tillage), other individual agricultural practices (residue removal with no cover crop vs. retaining residuals, cover cropping, and fertilizer 0, 40, and 80 kg ha-1 nitrogen) caused no significant shifts in δ15N and δ13C values in topsoil (0–15 cm). Among the evaluated factors, topography and depth predicted soil δ15N and δ13C profiles. Trends in δ13C vs. δ15N showed a wider range of δ13C values in topsoil of upslope plots under reduced tillage, while in the depositional location, conventional tillage had the same effect. This suggests erosion under reduced tillage occurred. Erosion and accelerated decomposition gradually slowed δ13C enrichment with soil depth. Digital soil mapping approach depicted low continuity of δ13C vs. high continuity of δ15N with geomorphic position We attributed the intermediate δ13C values, and steeper slope of δ13C against logarithm of soil organic carbon (SOC) across the slope to erosion and high SOM turnover, particularly of recently added plant inputs. Current results support the prediction of intensive vs. conservation practices’ effects on upslope soil stability and the fate of SOM in both topsoil and at depth of sloping farmlands.



中文翻译:

土壤 13C 的不均匀性与 15N 的均匀分布与地貌位置提供了侵蚀和加速有机质周转的证据

山坡上的耕作通常会影响土壤有机质 (SOM) 的积累和流失,具体取决于斜坡位置和种植模式。大多数山坡研究侧重于土壤运动,以描述侵蚀条件下 SOM 的周转率。在这项研究中,我们追踪侵蚀并描述农艺实践侵蚀对沿地貌位置的 SOM 易位和转化的影响。为实现这一目标,我们分别评估了土壤 δ 15 N 和 δ 13 C 同位素丰度的水平分布(上部 15 厘米)和垂直分布(至 100 厘米剖面) 。我们绘制了 δ 13 C、δ 15的空间分布图N 和 SOM 周转指数作为一种追踪 SOM 在田间侵蚀和退化的新方法。除了耕作(常规与减少耕作)外,其他个体农业实践(无覆盖作物去除残留物与保留残留物、覆盖作物以及施肥 0、40 和 80 kg ha -1 氮)没有导致 δ 的显变化表土 (0–15 cm) 中的15 N 和 δ 13 C 值。在评估的因素中,地形和深度预测了土壤 δ 15 N 和 δ 13 C 剖面。δ 13 C 与 δ 15 N 的趋势表明 δ 13的范围更广减耕条件下上坡地块表层土壤C值,而在沉积位置,常规耕作具有相同的效果。这表明发生了减少耕作下的侵蚀。侵蚀和加速分解逐渐减缓了δ 13 C随土壤深度的富集。数字土壤绘图方法描绘了 δ 13 C的低连续性与 δ 15 N的高连续性与地貌位置 我们归因于中间 δ 13 C 值,以及 δ 13的更陡坡度C 与土壤有机碳 (SOC) 的对数相对于斜坡的侵蚀和高 SOM 周转率,特别是最近添加的植物投入。目前的结果支持预测集约化与保护措施对上坡土壤稳定性的影响,以及表土和坡耕地深处 SOM 的命运。

更新日期:2023-06-09
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