中文摘要：

采用挖壕法,利用LI-8100土壤CO2通量自动观测系统,确定了北京西山侧柏人工林土壤呼吸中异养呼吸和根系自养呼吸的贡献率及其影响因子,分析了土壤呼吸的日、月际时间尺度的变异特征,并利用经验模型分析了土壤温度、土壤体积含水量对土壤呼吸的影响.结果表明：1土壤呼吸速率、异养呼吸速率的昼夜变化呈现单峰变化趋势,峰值出现在14：00—15：00;月际变化也呈单峰变化趋势,峰值出现在7—8月;观测期内土壤呼吸速率日均值变化范围在0.09～12.16μmol·m-2·s-1,异养呼吸速率日均值变化范围在0.02～10.86μmol·m-2·s-1,年均贡献率为69.59%;自养呼吸速率日均值为0.01～6.79μmol·m-2·s-1,年均贡献率为30.41%.2土壤温度的日、月际变化均呈单峰形曲线变化而土壤体积含水量变化规律不明显;整个观测期间土壤呼吸速率的温度敏感系数Q10为2.91,异养呼吸速率的Q10为3.52.3模型研究表明,相对于土壤温度、土壤体积含水量单因素模型,土壤温度与土壤体积含水量的复合模型对土壤呼吸速率变化解释能力为86.8%,对异养呼吸速率的解释能力为74.4%.该研究为森林生态系统碳收支估测及碳循环提供数据依据。

英文摘要：

Trenching plots were used to dynamically monitor soil respiration and to determine the factors controlling heterotrophic and autotrophic respiration based on LI-8100 soil respiration carbon dioxide flux measurement system in a Platycladus orientalis plantation in Jiufeng National Forest Park,Beijing. Soil temperature and volumetric water content at a depth of 5 cm were also measured. We demonstrated the diurnal and monthly variations of soil respiration,and analyzed the effects of soil temperature and volumetric water content on soil respiration with simple and binary mixed models. The results showed that： 1 The diurnal dynamics of soil respiration and heterotrophic respiration had single peaks,with the maxima at 14： 00 to 15： 00. Moreover,average monthly soil respiration and heterotrophic respiration also had single peaks,with the maxima in July to August. During the measurement periods,soil respiration,heterotrophic respiration,and autotrophic respiration rates ranged from 0. 09 to 12. 16,0. 02 to 10. 86,and 0. 01 to 6. 79 μmol·m- 2·s- 1,respectively. Additionally,the annual mean contributions of heterotrophic and autotrophic respiration to total soil respiration were 69. 59% and 30.41%,respectively. 2 The diurnal and monthly variations of soil temperature also showed a single peak,but the soil volumetric water content did not.Moreover,the Q10 values were 2. 91 and 3. 52 for soil respiration and heterotrophic respiration,respectively. 3 Soil respiration and heterotrophicrespiration were significantly correlated with soil temperature but not with volumetric water content. Comparing with the simple model,the goodness of the binary mixed model indicated that the combined effects of soil temperature and volumetric water content on soil respiration and heterotrophic respiration were 86. 8%,and 74. 4%,respectively. These results suggested that the data basis can contribute to our understanding of the carbon budget estimates and carbon cycle of forest ecosystems.