缙云山不同林分下土壤有机碳及矿化特征

土壤有机碳库是陆地最大的有机碳储存库,其微弱的变化就能影响大气CO2浓度的显著变化,其中森林土壤碳库约占全球土壤碳库的70%,因此如何实现森林生态系统土壤有机碳库的高效管理成为目前的研究热点.本研究以缙云山5种典型林分:阔叶林、针叶林、针阔叶混交林、竹林及研究区内弃耕15 a的荒草地(对照土壤)为对象,采用矿化培养实验,分析了不同林分的土壤在不同土层(0～20、20～40、40～60、60～100 cm)中的有机碳矿化特征.结果表明,林分类型、培养时长和土层深度均对土壤有机碳矿化速率有显著影响.不同林分土壤有机碳矿化速率均随着土层加深而降低,其中0～20 cm土层的矿化速率11. 97～25. 12 mg·(kg·d)-1]均显著高于其他土层(P 0. 05),其他土层间矿化速率4. 79～6. 51mg·(kg·d)-1]无显著性差异. 5种林分的土壤有机碳累积矿化量均随着土层加深而降低,0～20 cm土层中竹林和阔叶林土壤有机碳累积矿化量最高,分别为177. 66 mg·kg~(-1)和120. 38 mg·kg~(-1),随着土层加深在60～100 cm土层中,针叶林累计矿化量最高达到了46. 96 mg·kg~(-1).双库一级动力学方程可以较好地拟合缙云山不同林分下土壤有机碳矿化过程,不同林分下土壤易分解有机碳含量均随土层加深而降低,针叶林土壤矿化能力较强,对难分解有机碳库的利用程度较高,而竹林和阔叶林土壤微生物活性较高,可以有效促进碳循环,提高土壤固碳能力.

Characteristics of Soil Organic Carbon and Mineralization with Different Stands in Jinyun Mountain

Soil organic carbon (SOC) is the largest organic carbon stock on land, and slight changes in SOC can significantly affect the atmospheric CO₂ concentration, among which forest soil carbon reservoir accounts for approximately 70% of the global soil carbon stock. Therefore, the implementation of efficient management for SOC stock in the forest ecosystem has become a popular research subject. The mineralized characteristics of SOC in different soil layers (0-20, 20-40,40-60, and 60-100 cm) were analyzed in five typical stands of Jinyun Mountain:broadleaf forest, coniferous forest, coniferous and broadleaf mixed forest, bamboo forest, and 15a abandoned grassland (control soils) in the study area. The results showed that forest type, cultivation duration, and soil depth had significant effects on the SOC mineralization rate. The mineralization rate of SOC in different forest stands decreased with the deepening soil layer, among which the mineralization rate at the 0-20 cm soil layer11.97-25.12 mg·(kg·d)^-1] was significantly higher than that of other soil layers (P<0.05), and there were no significant differences between the mineralization rates of other soil layers4.79-6.51 mg·(kg·d)^-1]. The accumulated mineralization of SOC in the five forests decreased with the deepening soil layer. The accumulated mineralization of SOC in the bamboo forest and broadleaf forest in the 0-20 cm soil layer was the highest at 177.66 mg·kg^-1 and 120.38 mg·kg^-1, respectively. With the deepening soil layer in the 60-100 cm soil layer, the accumulated SOC mineralization in the coniferous forest reached the highest (46.96 mg·kg^-1). The SOC mineralization process in the different stands of Jinyun Mountain can be well fitted by the double reservoir first-level kinetic equation. The content of easily decomposable SOC in different forest stands decreased with the deepening soil layer. Coniferous forest soil exhibited a stronger mineralization ability and higher utilization degree of refractory organic carbon stock, while bamboo forest and broadleaf forest soils had higher microbial activity, which could effectively promote the carbon cycle and improve the soil carbon fixation ability.