东北典型黑土区土壤有机碳结构特征及其影响因素

Characteristics of soil organic carbon structure in the black soil region in Northeast China and its influencing factors

土壤有机碳化学结构对土壤固碳与肥力的形成具有重要意义。为探究东北典型黑土区土壤有机碳的结构特征及其影响因素,利用13C核磁共振技术研究了海伦、齐齐哈尔、长春和沈阳四个区域典型土壤有机碳的化学组成,分析了其与土壤物理、化学性质及气候因子的关系。结果表明,来自4个不同区域土壤有机碳的组成和结构有显著差异,海伦地区的土壤有机碳有较低的烷基碳比例(30.62±0.95)%、烷基指数(A/OA)(0.96±0.06)以及疏水性指数(HB/HI)(1.00±0.03),其有机碳化学性质更为活泼,而沈阳地区的烷基碳比例(42.42±1.03)%、A/OA(1.53±0.03)以及HB/HI(1.40±0.04)指数均最高。长春和齐齐哈尔地区的烷基碳比例、A/OA以及HB/HI指数值则介于海伦和沈阳之间。土壤有机碳、全氮含量与烷基碳比例、A/OA、HB/HI呈显著负相关(P<0.01),与含氧烷基碳、羰基碳比例显著正相关(P<0.01)。同时,A/OA、HB/HI与年平均气温呈显著正相关(P<0.01)。结果表明,沈阳地区由于具有较高的年均温,加速了土壤有机碳的分解使得烷基碳比例增加,腐殖化程度提高,惰性增强,结构更为稳定,但其中的活性有机碳积累较少。相反,海伦地区由于气候冷凉,土壤的活性有机碳组分含量更高,性质更为活泼,未来气候变暖下可能会加速有机碳的分解,因此更应关注这些地区的有机碳库的变化和增碳措施的实施。研究结果为准确评估东北典型黑土区土壤的有机碳稳定性及碳循环提供了重要参考。

The chemical structure of soil organic carbon(SOC)is crucial indicator of soil function and soil carbon stability,playing a vital role in carbon sequestration and fertility.Black soils in various regions of Northeast China encounter distinct degradation issues:Hailun region experiences decline in soil organic matter and erosion;Changchun region faces thinning of the soil;Qiqihar region suffers from loss of soil nutrients and carbon;Shenyang region deals with acidification and barrenness.The chemical structure and stability of SOC are closely associated with soil degradation.However,there is limited research on the characteristics of the chemical structure of SOC in these aforementioned regions as well as its relationship with environmental factors such as climate and soil conditions.To gain insights into the structural characteristics of SOC and its influencing factors in the black soil region of Northeast China,this study employed 13C nuclear magnetic resonance(NMR)technology to characterize the chemical structure and composition of SOC in soils from Hailun,Qiqihar,Changchun,and Shenyang regions,and further explored their relationships with soil properties and climate factors.The results revealed significant regional variations in SOC structure across Northeast China.Notably,soils from the Hailun region exhibited lower proportions of Alkyl C(30.62±0.95)%,alkyl index(A/OA)(0.96±0.06),and hydrophobicity index(HB/HI)(1.40±0.04),indicating higher chemical reactivity of organic carbon compared to other regions.Conversely,SOC in soils from the Shenyang region displayed high decomposition levels with limited breakdown potential or utilization efficiency.Negative correlations were observed between SOC,total nitrogen contents and Alkyl C proportion,A/OA,HB/HI;while positive correlations were observed between O-alkyl C proportion and Carbonyl C proportion.Moreover,the ratio of A/OA as well as HB/HI showed significantly positive correlation with mean annual temperature.These findings suggest that higher mean annual temperatures in Shenyang region accelerate SOC decomposition and thus lead to an increase in Alkyl C fraction,humification level,inertness degree,and overall stability,meanwhile,a lower reactive organic carbon content wherein.In contrast,soils in Hailun region under colder climate condition possess higher fractions of active organic carbon making them more chemically reactive.Under future warming scenarios,SOC decomposition rate in Hailun region may be further accelerated.Therefore,it is imperative to pay greater attention to monitor the dynamic of organic carbon pool,along with the implementation of measures aiming at enhancing soil carbon sequestration in this region.The findings offer a crucial reference for the accurate assessment of SOC stability and carbon cycling in representative black soil regions of Northeast China.