次生栎林与火炬松人工林土壤呼吸的季节变异及其主要影响因子

Seasonal variation of soil respiration and its main regulating factors in a secondary oak forest and a pine plantation in north-subtropical area in China

土壤呼吸是陆地生态系统碳循环的重要组成部分。随着全球气候变暖趋势逐渐明显,土壤呼吸的时空变异及其对温度变化的响应已成为生态学研究的重要内容之一。利用LI-6400-09土壤碳通量观测仪,在江苏省南京林业大学下蜀实验基地,采用随机区组实验设计方法,连续两年测定了北亚热带次生栎林和火炬松人工林土壤呼吸的季节动态变化,结果表明:(1)两种林分内土壤呼吸速率均具有明显的季节波动,表现为:在最冷的1月份,土壤呼吸速率最低,随着土壤温度的升高,土壤呼吸速率也逐渐上升,在7、8月份达到最大值,随后又逐渐下降;(2)次生栎林月平均土壤呼吸速率在0.271～3.22μmolCO.2m-.2s-1之间,年变异幅度为11.88;火炬松人工林月平均土壤呼吸速率在0.336～3.06μmolCO2.m-.2s-1,年变异幅度为9.11;(3)次生栎林土壤呼吸的Q10值在2.19至2.27之间,火炬松人工林土壤呼吸的Q10值在2.02至2.15之间,次生栎林土壤呼吸对温度的敏感性大于火炬松人工林;(4)土壤呼吸速率与不同深度层次土壤温度之间均呈显著性正相关,与土壤微生物生物量之间呈显著性负相关,而与土壤含水率、凋落物输入量之间相关不显著。研究结果初步阐明了江淮流域北亚热带典型森林植被土壤呼吸的季节动态特征及主要影响因子,为进一步揭示该区域森林土壤碳循环特点提供了理论基础。

Soil respiration is an important component in carbon cycle of the terrestrial ecosystem. With global warming, the temporal and spatial variability of soil respiration and its sensitivity to temperature has been a central interest to ecologist in global change field. The seasonal variation of soil respiration was measured monthly by LI-6400-09 in a secondary oak forest and a pine plantation in an experiment with randomized block design from October, 2003 to September, 2005 in Xiashu Forest Experimental Site of Nanjing Forestry University, Jiangsu Province, Southeastern China. The results showed that： （ 1 ） There were significant seasonal variation of soil respiration both in oak forest and pine plantation, which were lowest in January with lowest soil temperature, and with the soil temperature increasing from January to July, soil respiration increased correspondingly and peaked in July or August, and then decreased progressively. （2） The monthly mean of soil respiration ranged from 0. 271 to 3.22μmolCO.2m^-2.s^-1 in oak forest and ranged from 0. 336 to 3. 06μmolCO.2m^-2.s^-1 in pine plantation, respectively. （3） The Qlo value of soil respiration ranged from 2.19 to 2.27 in oak forest and ranged from 2.02 to 2.15 in pine plantation, respectively. Moreover, the Q10 value in oak forest was higher than in pine plantation. （4） The soil respiration were significantly positively correlated with soil temperature, and significantly negatively correlated with soil microbial biomass, but no correlation with soil moisture or plant litterfall. Our results suggested that there were significant seasonal variation of soil respiration in sub-tropical area in Southeastern China and soil temperature was the main regulating factors