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不同利用方式下土壤矿物结合态有机碳特征与容量分析

花匠小妙招
2024-10-31 00:27

摘要： 【目的】土壤矿物结合态有机碳是土壤有机碳固持的重要机制之一。探讨不同利用方式下土壤有机碳及矿物结合态有机碳（＜53 µm）的含量、分配比例及其差异性特征，对于深刻认识土壤碳的固持状态、固碳潜力及其可持续管理均具有重要意义。【方法】通过从中国知网、万方、Science Direct和Springer link等4个文献数据库，设定检索条件“2000—2014年”、“中国土壤有机碳”和“＜53 µm团聚体分组”3个关键词，筛选出已发表的111篇目标文献，收集901组土壤有机碳和矿物结合态有机碳含量与比例的相关数据集。其中，土地利用方式分为4类：农田（n=580）、草地（n=98）、林地（n=193）和其他（果园、茶园等，n=31）。农田包括黑土、水稻土、棕壤、潮土、红壤和灰漠土等六大土壤类型。不同利用方式及土壤类型中有机碳含量与分配比例的差异性均采用Kruskal-Wallis H单向显著性检验。【结果】不同利用方式下土壤总有机碳和矿物结合态有机碳含量的中值均存在显著差异（P＜0.05）。其中，林地土壤总有机碳含量的中值为18.2 g·kg-1，显著高于草地（12.0 g·kg-1）和农田（10.3 g·kg-1）；且林地矿物结合态有机碳含量（12.0 g·kg-1 soil）也显著高于农田和草地（8.0—7.6 g·kg-1 soil）。3种利用方式下土壤矿物结合态有机碳与总有机碳之间均呈现极显著的正相关关系（P＜0.001），农田土壤矿物结合态有机碳所占比例的中值为74.8%，显著高于林地（70.3%）和草地（67.8%）。农田中不同土壤类型的矿物结合态有机碳占总有机碳的比例也存在显著差异。其中，黑土中矿物结合态有机碳的比例最高，中值为87.4%，其次是水稻土（76.7%）和红壤（74.0%），而灰漠土最低（62.5%）。相关分析表明，土壤有机碳水平相对较高的黑土、水稻土和棕壤，矿物结合态有机碳分配比例随着土壤有机碳含量的增加而显著降低（P＜0.05）。农田、草地和林地中土壤矿物结合态有机碳含量与土壤细颗粒（＜53 µm）含量均呈极显著的正相关关系，与Six等（2002）的估算结果相比，其饱和程度分别为68.4%、58.7%和91.5%。【结论】农田和草地中，土壤矿物结合态有机碳还未达到饱和，仍有一定的提升空间，土壤细颗粒（＜53 µm）仍具有一定的固碳潜力。

关键词: 土地利用方式, 土壤类型, 矿物结合态有机碳, 农田

Abstract: 【Objective】 Mineral-associated organic carbon (MOC, ＜53 µm) is one of the most important stabilization mechanisms of soil organic carbon (SOC). The objectives were to explore the content, proportion, and variations of the mineral-associated organic carbon from China's major land uses of cropland, grass land, and forest, which have a great significance to SOC stabilization, soil carbon sequestration potential, and sustainable carbon management.【Method】Publications were searched by using Web of China Knowledge Resource Integrated Database, Wan Fang Database, Science Direct and Springer link with the three keywords “2000-2014”, “Soil organic carbon”, “China” and “Aggregate fractionation (＜53 µm)”. A data set was set up with 901 pairs of data from 111 published papers that reported soil organic carbon and fractionation. Four categories of land uses such as Cropland (n = 580), Grassland (n = 98), Forest (n = 193), and other (Orchards, Tea plantations, etc., n = 31) were included. Soils from cropland included six soil classifications: Black soil, Paddy soil, Brown soil, Fluvo-aquic soil, Red soil, and Gray desert soil. The variations analysis of the SOC content and MOC and the proportion in different land uses and soil classification were performed using Kruskal-Wallis H significance test. 【Result】 The median value of total SOC content and MOC were significantly different among the three land uses. The total SOC content in forest soil was 18.2 g·kg-1, which was significantly higher than those in the soils from grassland and cropland (12.0 and 10.3 g·kg-1, respectively). The content of MOC (12.0 g·kg-1 soil) was also significantly higher than that from cropland and grass land (8.0 and 7.6 g·kg-1 soil, respectively). There were significant positive correlations (P＜0.001) between total SOC and MOC in the three land uses. The proportion of MOC in cropland (74.8%) was significantly higher than those in grassland (67.8%) and forest (70.3%) soil. It was also found that the proportion of MOC varied significantly according to land use and soil classification. The MOC proportion of black soil was the highest and the median was 87.4%, followed by paddy soils (76.7%) and red soil (74.0%). However, the proportion of gray desert soil was the lowest (62.5%). Regression analysis showed that the proportion of MOC decreased significantly with the increase in total SOC (P＜0.05) in black soil, paddy and brown soils, which was relatively high in SOC content. The MOC content was significantly correlated with the fine soil particles (＜53 µm) in cropland, grassland and forest, indicating the MOC saturation degrees were 68.4%, 58.7% and 91.5%, according to Six (2002) estimation, respectively. 【Conclusion】 MOC is unsaturated and can be further enhanced both in cropland and grassland soils. Therefore, the fine soil particles (＜53 µm) from cropland and grassland still have a high carbon sequestration potential.

Key words: land use, soil classification, mineral-associated organic carbon, cropland