小兴安岭4种典型阔叶红松林土壤有机碳分解特性

土壤有机碳分解是陆地生态系统碳循环的重要组成部分.主要采用土壤有机碳释放速率的室内培养实验的方法,并根据三库一级动力学模型,对小兴安岭地区4种典型阔叶红松林的土壤有机碳分解特征及各组分含量进行研究.实验结果如下:(1)土壤有机碳的分解趋势表现为前期迅速,后期缓慢,并且土壤腐殖质层(A)大于淀积层(B);在4种阔叶红松林中,云冷杉红松林土壤有机碳的分解速率最大,枫桦红松林最小;土壤有机碳的分解速率与土壤总有机碳、活性碳及土壤的C/N呈显著的正相关关系(P＜0.05).(2)在土壤A层和B层,4种阔叶红松林的活性碳分别占总有机碳的0.89％-1.78％和1.91％-2.87％,平均驻留时间为12-35 d和27-58 d.缓效性碳占总有机碳的22.58％-28.44％和23.87％-42.63％,平均驻留时间为4-19 a和18-37 a.惰性碳占总有机碳的69.98％-76.24％和54.50％-74.22％,平均驻留时间为173 a;土壤有机碳各组分含量及驻留时间的大小顺序均为:云冷杉红松林＞椴树红松林＞枫桦红松林＞蒙古栎红松林.

SOC decomposition of four typical broad-leaved Korean pine communities in Xiaoxing' an Mountain

Decomposition of soil organic carbon is a critical component of the carbon cycling in terrestrial ecosysytem. A 90-day laboratory incubation was conducted to measure CO₂ evolution from four different korean pine forests in Xiaoxing''an mountain, and the data from the incubation experiment were fitted to a three-pool first-order model that separate mineralizable soil organic carbon (SOC) into active, slow and resistant carbon pools. The combination of laboratory measurement and field experiment were used to investigate SOC content and turnover rate in different forest stands. The results suggested that: (1) Although the decomposition rates of SOC vary widely in the four typical primary Korean pine forest stands, the dynamic change trend of decomposition was similar with the rapid decomposition in the initial incubation stages and slowly declined and tend to a steady state in the end; At A horizon, the decomposition rates followed the order Picea sp.-Abies nephrolepis-Pinus koraiensis forest > Quercus mongolica-Pinus koraiensis forest > Tilia amurensis-Pinus koraiensis forest > Betula costata-Pinus koraiensis forest, Quercus mongolica-Pinus koraiensis forest and Tilia amurensis-Pinus koraiensis forest did not display much more difference in SOC decomposition. However, at B horizon, the decomposition rate of Picea sp.-Abies nephrolepis-Pinus koraiensis forest was higher than the other three forests, and the marked difference was not found in the other three forest stands. The decomposition rate of Picea sp. -Abies nephrolepis-Pinus koraiensis forest was maximized and the minimum existed in Betula costata-Pinus koraiensis forest; The decomposition rate has a positive relationship with SOC and active carbon organic content and C/N. (2) The active carbon pool accounted for 0.89%-1.78% of SOC with an average MRT of 12-35 d at A horizon, 1.91%-2.87% and 27-58 d at B horizon. The slow carbon pool accounted for 22.58%-28.44% of SOC with an average MRT of 4-19 a at A horizon, 23.87%-42.63% and 16-37 a at B horizon. The Cr pool accounted for 69.98%-76.24% and 54.50%-74.42% of SOC with an average MRT of 173 a at A and B horizon, respectively. The content of Ca and Cs was greater at A horizon than that at B horizon, contrary to the changing tendency, the ratios of Ca to SOC and Cs to SOC increased with increasing depth in the soil profile; The pool size and laboratory mean residence times of SOC decreased in the order: Picea sp.-Abies nephrolepis-Pinus koraiensis forest> Tilia amurensis-Pinus koraiensis forest>Betula costata-Pinus koraiensis forest>Quercus mongolica-Pinus koraiensis forest. At A horizon or B horizon, the size of three carbon pools in Picea sp.-Abies nephrolepis-Pinus koraiensis forest was the biggest, but Quercus mongolica-Pinus koraiensis forest at high altitude has the lowest content of three kinds of SOC pools. Hence, the content of SOC in different community tapes has a great relationship with geographical location. In addition to this, the relationship between litterfall biomass and respiration and soil organic carbon content at A horizon further demonstrated that litterfall on the forest floor has an important effect on the soil organic carbon content.