Abstract:

Quantifying the variations of soil organic carbon and its fractions carbon content in Quercus mongolica forests under long-term different forest management practices is of great significance for understanding the long-term impacts of forest management regimes on soil carbon pool and its carbon sequestration mechanism. In this study, the density fractionation scheme was used to study the changes of soil organic carbon and its aggregate fraction carbon content under three distinctive Q. mongolica forest stands with different management intensities within the Danqinghe Forest Station in Harbin, Heilongjiang province, northeast of China. These three Q. mongolica forest stands were (1) target tree nurture management (40%, 45% and 70% of nurture intensity with cutting irrigation and weeding), (2) comprehensive tree nurture management (40% and 40% intensity) and (3) no-disturbance tree nurture management. The results showed that compared with no-disturbance tree nurture management, target tree nurture management and comprehensive tree nurture management had no significant effect on total soil organic carbon content. Compared with no-disturbance management, comprehensive tree nurture management significantly reduced the content of coarse free particulate organic carbon (cfPOC) by 19.94% (P<0.05), while target tree nurture management significantly increased the content of mineral associated organic carbon (MOC) by 97.92% (P<0.05). There was no significant difference in the content of fine free particulate organic carbon (ffPOC) and intra-micro aggregate particulate organic carbon (iPOC) among the three management regimes. Coarse free particulate organic carbon accounts for 70.63%-76.53% of total soil organic carbon, which is the main form of soil organic carbon sequestration. Soil C/N decreased gradually according to particulate organic carbon, intra-micro aggregate particulate organic carbon and mineral associated organic carbon, reflecting the process of transformation and fixation of organic carbon in soil. In terms of improving soil quality and carbon sequestration capacity, target tree management is the optimal management regime for Q. mongolica secondary forest, followed by non-disturbance regime, while comprehensive tree nurture management has little impact on soil quality and carbon sequestration.

Key words: natural secondary Quercus mongolica forests, target tree forest management, comprehensive nurturing management, free particulate organic carbon, mineral associated organic carbon

摘要：

准确把握长期不同经营措施下蒙古栎林（Quercus mongolica）土壤有机碳及其组分碳含量的变化，对于深入理解森林经营管理对土壤碳库的长效影响作用及其固碳机制具有重要意义。以黑龙江省哈尔滨市丹清河实验林场蒙古栎天然次生林为研究对象，采用物理分组方法，研究目标树经营（经营强度45%、40%、70%，折灌除草）、综合抚育经营（经营强度45%、40%，不清理灌草）、无干扰经营对土壤有机碳及其组分碳含量的长效影响。结果表明，在23 a的经营实践后，与无干扰经营相比，目标树经营和综合抚育经营对土壤总有机碳含量的影响不显著，综合抚育经营显著降低了19.94%的粗自由颗粒有机碳（cfPOC）含量（P<0.05），而目标树经营显著提高了矿物结合态有机碳（MOC）含量97.92%（P<0.05），细自由颗粒有机碳（ffPOC）和物理保护颗粒有机碳（iPOC）含量在3种经营模式间无显著差异。粗自由颗粒有机碳占土壤总有机碳含量的70.63%—76.53%，是土壤固存有机碳的主要形式。土壤C/N依次按颗粒有机碳、物理保护有机碳和矿物结合态有机碳逐渐降低，反映了有机碳在土壤中转化和固定的过程。从提升土壤质量及固碳能力方面考虑，目标树经营是蒙古栎次生林最优经营模式，无干扰模式次之，综合抚育经营对土壤质量和固碳增汇的影响较小。

关键词: 蒙古栎天然次生林, 目标树经营, 综合抚育经营, 自由颗粒有机碳, 矿物结合态有机碳