中文摘要：

森林土壤有机碳在全球碳循环中的重要作用主要取决于有机碳的稳定性。为科学评价杉木人工林土壤的碳汇功能及固碳潜力,对湖南省会同县不同发育阶段的杉木人工林土壤有机碳的生化特征和物理保护程度进行了研究。结果表明,在杉木人工林发育过程中,土壤总有机碳（SOC）、微生物生物量碳（MBC）、活性碳库Ⅰ（LPⅠ）、活性碳库Ⅱ（LPⅡ）和重组有机碳（HOC）含量以及微生物熵（MQ）均在中龄林阶段出现最低值,而轻组有机碳（LOC）和顽固性组分（RF）随林龄增加呈现持续上升趋势。土壤RF占SOC的比例（顽固性碳指数,Ir,C）则表现为先增加后减少,即在中龄林阶段比例最高,在成熟林阶段为41.9%-57.6%,高于幼龄林阶段的38.7%-43.0%;HOC占SOC的比例从幼龄林阶段的86.4%-87.5%下降到成熟林阶段的82.5%-83.9%。总体而言,杉木人工林的发育过程是土壤有机碳积累的过程,在这个过程中,土壤有机碳自身的顽固性增强,但受到的物理保护程度减弱。此外,各组分中以LP I对土壤微生物的有效性最高。

英文摘要：

The importance of soil organic carbon（SOC） in forest soils to the global carbon cycle depends on stability of this soil carbon.However,little is yet known about changes in stability of SOC during the development of fir plantations.To scientifically evaluate the carbon pool function and carbon sequestration potential of the soils under Chinese fir plantations,investigations were done of biochemical characteristics and degree of physical protection of the soil organic carbon in the soils under Chinese fir plantations different in growth stage.Results show that the contents of total SOC,microbial biomass carbon（MBC）,labile pool I（LP I）,labile pool II（LP II）,heavy organic carbon（HOC）,and microbial quotient（MQ） fell to the bottom at the middle-age stage,while the contents of light organic carbon（LOC） and recalcitrant fraction（RF） increased with the age of the stands,but the proportion of recalcitrant fraction in SOC increased first and decreased afterwards,which means that it peaked at the middle-age stage,and ranged from 41.9% to 57.6% under the stand at the mature stage,and from 38.7% to 43.0% under the stand at the young stage.The proportion of HOC in SOC ranged from 86.4% to 87.5% under the stand at the young stage and from 82.5% to 83.9% under the stand at the mature stage.On the whole,the development of a Chinese fir plantation is a process of SOC accumulation in the soil,and during the process SOC per se increased in recalcitrance while decreased in the degree of physical protection.Besides,among all the fractions researched in this study,LP I is the highest in availability to soil microbial biomass.