【作者】 陈光水；

【导师】 杨玉盛；

【作者基本信息】 福建师范大学 ， 自然地理， 2009， 博士

【摘要】 森林土壤呼吸和地下碳分配是森林碳平衡的两个重要分量,其随林龄变化规律及控制机理研究,在揭示林龄对森林碳收支影响、区域森林碳汇估算和森林碳汇经营上有十分重要作用。本研究选择我国著名杉木中心产区福建省南平市王台镇溪后村安曹下本底条件一致的、目前国内年龄跨度最大的杉木林年龄序列（2a、7a、16a、21a、40a和88a生）为研究对象,深入研究杉木林土壤呼吸和地下碳分配随林龄变化规律及其影响机理,为构建我国杉木林碳循环模型、杉木林碳源汇的科学估算及探寻合理的杉木林碳增汇措施等提供科学依据。研究结果表明,除受土壤温度、土壤含水量影响外,杉木林土壤呼吸月动态还受凋落物季节节律影响:合并所有林龄（除2a生外）后土壤总呼吸、异养呼吸和根系呼吸速率均与前第3个月凋落物量呈显著正相关,而与后一个月凋落物量呈显著负相关。土壤总呼吸和土壤异养呼吸Q₁₀值在不同林龄间没有显著差异;除21a生杉木林根系呼吸Q₁₀值显著低于88a生的外,不同林龄间根系呼吸Q₁₀值没有显著差异。杉木林土壤总呼吸年通量随林龄呈先上升后下降趋势,除40a生的与2、7a生的有显著差异外,其余无显著差异;杉木林土壤异养呼吸年通量随林龄呈先下降后上升趋势,除88a生的与7、16a生的有显著差异外,其余无显著差异;杉木林根系呼吸年通量随林龄呈先上升后下降趋势,2a和88a生的显著低于7～40a生。杉木林土壤总呼吸、异养呼吸、根系呼吸随林龄变化均可用时间动态曲线很好地拟合。杉木林年龄序列中土壤总呼吸年通量与年凋落物量密切相关;根系呼吸年通量与细根生物量、地上净生产力呈紧密正相关,而与土壤有机碳贮量呈显著负相关。根系呼吸/土壤总呼吸比例介于25.0%～40.7%之间,随林龄呈先上升、后下降的趋势;并与细根生物量、地上净生产力和林分净生产力呈紧密正相关,而与土壤有机碳贮量呈显著负相关。杉木林地下碳分配随林龄呈先上升、后下降趋势,与地上净生产力密切相关;16a生和21a生杉木林地下碳分配显著高于7a生和40a生,而88a生的则最低。7a～21a生杉木林根系碳利用效率≈0.5;但在40a生和88a生中则＜0.5,表明在成熟林和老龄林中不符合根系碳利用效率为0.5的一般假设。更多还原

【Abstract】 Age-related changes and controlling mechanisms of soil respiration （SR） and total belowground carbon allocation （TBCA）, the two most important carbon fluxes of forest ecosystems, are of much significance in understanding the effects of stand age on forest carbon source/sink, regional forest carbon budget and forest carbon management.A Chinese fir （Cunninghamia lanceolata （Lamb.） Hook） chronosequence, consisting of stands of 2-, 7-, 16-, 40- and 88-year-old that encompassed the longest age span ever selected, located on the same sites at the famous Chinese fir planting area in Ancaoxia, Wangtai, Nanping City, Fujian Province, was chosen for a research purpose on age-related changes and controlling factors of soil respiration and TBCA. This will help greatly for carbon cycle model construction, carbon sink/source account and carbon management of this most important timber species in southern China.Monthly soil respiration rate was related to seasonal fluctuation of litterfall in addition to changes of soil temperature and soil moisture content. When all ages exept the 2-year-old stand were pooled together, monthly rates of total soil respiration, heterotrophic respiration and root respiration were postively correlated with the 3-month-preceding litterfall, and negatively related to the following month litterfall. The Qio values of total soil respiration and heterotrophic respiration were not significantly different among stand ages, and those of root respiration were detected significantly different only between age 21 and age 88. Annual CO₂ flux from total soil respiration first increased and then decreased with stand age, with significantly higher in age 40 than in age 2 and 7. A similar trend occurred for annual CO₂ flux from root respiration, with significantly lower in age 2 and 88 than in age 7～40. Annual CO₂ flux from soil heterotrophic respiration showed a decrease and then an increase pattern with stand age, with significant differences between age 88 and age 7 or 16. The age-related changes of total soil respiration, heterotrophic respiration and root respiration can be fitted very well by a time curve model. Annual CO₂ flux of total soil respiration was highly correlated with annual litterfall, and that of root respiration positively correlated with fine root biomass and aboveground NPP and negatively correlated with SOC stock. The contributions of root respiration to total soil respiration, ranging from 25.0% to 40.7%, first increased and then decreased with stand age, and was highly positively correlated with fine root biomass, aboveground NPP and total NPP and negatively correlated with SOC stock. TBCA showed an increase trend followed by a decrease trend with stand age, with significantly higher in age 16 and 21 than in age 7 and 40, and with the lowest value in age 88. The root carbon use efficiency （RCUE） was close to 0.5 in age 7～21 and much lower than 0.5 in age 40 and 88, indicating the failure of the general RCUE hypothesis of 0.5 in the mature and old-growth stages.更多还原