College of Resources, Sichuan Agricultural University, Chengdu 611130, China.
College of Resources, Sichuan Agricultural University, Chengdu 611130, China; Sichuan Green Food Development Center, Chengdu 610041, China.
Sci Total Environ. 2022 Dec 10;851(Pt 2):158323. doi: 10.1016/j.scitotenv.2022.158323. Epub 2022 Aug 28.
Cropland soils are considered to have the potential to sequester carbon (C). Warming can increase soil organic C (SOC) by enhancing primary production, but it can also cause carbon release from soils. However, the role of warming in governing cropland SOC dynamics over broad geographic scales remains poorly understood. Using over 4000 soil samples collected in the 1980s and 2010s across the Sichuan Basin of China, this study assessed the warming-induced cropland SOC change and the correlations with precipitation, cropland type and soil type. Results showed mean SOC content increased from 11.10 to 13.85 g C kg. Larger SOC increments were observed under drier conditions (precipitation < 1050 mm, dryland and paddy-dryland rotation cropland), which were 1.67-2.23 times higher than under wetter conditions (precipitation > 1050 mm and paddy fields). Despite the significant associations of SOC increment with crop productivity, precipitation, fertilization, cropland type and soil type, warming also acted as one of major contributors to cropland SOC change. The SOC increment changed parabolically with the rise in temperature increase rate under relatively drier conditions, while temperature increase had no impact on cropland SOC increment under wetter conditions. Meanwhile, the patterns of the parabolical relationship varied with soil types in drylands, where the threshold of temperature increase rate, the point at which the SOC increment switched from increasing to decreasing with warming, was lower for clayey soils (Ali-Perudic Argosols) than for sandy soils (Purpli-Udic Cambosols). These results illustrate divergent responses of cropland SOC to warming under different environments, which were contingent on water conditions and soil types. Our findings emphasize the importance of formulating appropriate field water management for sustainable C sequestration and the necessity of incorporating environment-specific mechanisms in Earth system models for better understanding of the soil C-climate feedback in complex environments.
耕地土壤被认为具有固碳潜力。增温可以通过提高初级生产力来增加土壤有机碳（SOC），但也会导致土壤释放碳。然而，增温在多大程度上控制了广阔地理范围内耕地 SOC 动态变化仍不清楚。本研究利用中国四川盆地 20 世纪 80 年代和 2010 年代采集的 4000 多个土壤样本，评估了增温引起的耕地 SOC 变化及其与降水、耕地类型和土壤类型的相关性。结果表明，SOC 含量均值从 11.10 增加到 13.85 g C kg。在较干燥条件下（降水<1050 mm，旱地和旱稻轮作耕地）SOC 增加量较大，是较湿润条件下（降水>1050 mm 和稻田）的 1.67-2.23 倍。尽管 SOC 增加与作物生产力、降水、施肥、耕地类型和土壤类型显著相关，但增温也是耕地 SOC 变化的主要因素之一。在相对干燥条件下，SOC 增加量随升温速率的升高呈抛物线变化，而在较湿润条件下，升温对耕地 SOC 增加量没有影响。同时，在旱地中，土壤类型的变化也改变了抛物线关系的模式，升温速率的阈值（即 SOC 增加量随升温从增加转为减少的转折点）在粘土地（Ali-Perudic Argosols）比在砂土地（Purpli-Udic Cambosols）更低。这些结果表明，在不同环境下，耕地 SOC 对增温的响应存在差异，这取决于水分条件和土壤类型。本研究结果强调了制定适当田间水分管理措施以实现可持续固碳的重要性，以及在地球系统模型中纳入特定环境机制以更好地理解复杂环境下土壤 C-气候反馈的必要性。
