不同经营模式对蒙古栎天然次生林土壤有机碳积累的影响机制研究

Forest management is the eternal topic and the core target for modern forestry construction in China. How to improve soil organic carbon content and accumulated more carbon in soil through reasonable forest management regimes has become the emerging scientific issues, under the background of low soil fertility of natural secondary forest in Northeast China and the important strategy decisions for developing forest sink. Taking the secondary Quercus mongolica forest at Danqinghe experimental forest farm in Heilongjiang province as the research objects, this project aims to make a quantitative study about the response and variation of soil organic carbon content to four forest management regimes, including no-distance management regimes, traditional extensive management regimes, target tree management regimes and forest ecosystem management regimes. By analyzing the carbon content of soil aggregate fraction and soil chemical composition, the effects of different management regimes on soil organic carbon fraction and structure was explored. By analyzing the variation of soil microbe community characterisitic, the microbiology mechanism of soil organic carbon accumulation to different management regimes was investigated. Based on the above results, the best suitable forest management regimes on soil organic carbon accumulation will be selected. Research results are of significance for better understanding soil organic carbon sequestration and accumulation, for estimate forest soil sink, for forest quality evaluation in forest soil under different management regimes, and will also in practice provide scientific basis and decision-making reference in natural secondary forest management.

森林经营是我国现代林业建设的核心任务和主攻方向。针对东北天然次生林土壤质量低下的现实和国家发展森林碳汇的战略需求，如何通过森林经营促进次生林土壤有机碳积累是当前亟待解决的科学问题。本研究拟以全国森林经营样板基地丹清河实验林场的蒙古栎天然次生林为研究对象，研究无干扰经营、传统粗放经营、目标树经营和生态系统经营四种模式对土壤有机碳积累的影响机制。通过多次野外取样和分析，研究不同经营模式下土壤有机碳含量的动态变化及其关键影响因素；通过对土壤物理组分碳、化学结构碳的测定，分析不同经营模式对土壤有机碳组分和结构的影响效应；通过研究微生物群落特征的变化，探讨不同经营模式下土壤有机碳积累的微生物学机理。研究结果可为完善森林土壤碳循环和估算森林土壤碳汇、深化森林经营理论提供机理认识，为森林立地质量精准评价提供理论支撑，同时对优化筛选基于提高土壤有机碳积累的最佳天然次生林经营策略管理具有重要现实意义。

森林经营是我国现代林业建设的核心任务和主攻方向。针对东北天然次生林土壤质量低下的现实和国家发展森林碳汇的战略需求，如何通过森林经营促进次生林土壤有机碳积累是当前亟待解决的科学问题。项目以全国森林经营样板基地丹青河实验林场的蒙古栎天然次生林为研究对象，研究目标树经营、综合抚育经营、无干扰经营三种经营模式对土壤有机碳积累的影响及其机制。研究表明：（1）三种经营模式下，蒙古栎次生林0-10cm土层有机碳含量显著高于10-20cm土层35.29%~42.28%。与无干扰经营相比，目标树经营提高了土壤有机碳含量，综合抚育经营降低了土壤有机碳含量。土壤速效氮和全氮含量是土壤有机碳变化的最主要环境控制因子。（2）三种经营模式下，土壤粗自由颗粒有机碳（cfPOC）含量占总有机碳含量的比例（59.86%~76.53%）最高，是有机碳在土壤中固存的主要形式。与无干扰经营相比，目标树经营显著提高了矿物结合态有机碳（MOC）含量，综合抚育经营显著降低了粗自由颗粒有机碳含量，与土壤有机碳在这两种经营模式下的变化一致。（3）三种经营模式下，烷氧C>烷基C>芳香C>羰基C含量。与无干扰经营相比，目标树经营显著提高了土壤活性成分烷氧C的含量，降低了有机碳分解指标烷基C/烷氧C比值，而综合抚育经营趋势相反。（4）三种经营模式下，0-10cm土壤微生物量显著高于10-20cm，但三种经营模式间无显著差异。微生物量与土壤有机碳、矿物结合态有机碳和细颗粒有机碳含量显著相关。蔗糖酶活性与细自由颗粒有机碳含量显著相关，脲酶和过氧化氢酶活性与土壤有机碳和粗自由颗粒有机碳含量显著相关。（5）目标树经营提高了土壤小颗粒占比，综合抚育经营提高了土壤中间颗粒占比，无干扰经营提高了土壤大颗粒组分占比，改变了土壤质地。（6）无干扰经营下林分碳储量显著大于目标树经营和综合抚育经营，后两种经营模式间无差异，土壤层碳储量占林分总碳储量的比例最大。总之，从提高林分土壤碳含量的角度，建议通过人为措施增加土壤氮养分含量，防范土壤有机碳降解风险。从提升土壤质量及提升林分固碳潜力的角度，建议对类似林分降低经营强度，优化经营技术措施，达到固碳增汇和提高林分质量的多目标经营。从筛选实践经营模式的角度，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最小。