Chinese Institute of Green Carbon, The School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.
PLoS One. 2011;6(12):e28397. doi: 10.1371/journal.pone.0028397. Epub 2011 Dec 6.
China possesses large areas of plantation forests which take up great quantities of carbon. However, studies on soil respiration in these plantation forests are rather scarce and their soil carbon flux remains an uncertainty. In this study, we used an automatic chamber system to measure soil surface flux of a 50-year-old mature plantation of Platycladus orientalis at Jiufeng Mountain, Beijing, China. Mean daily soil respiration rates (R(s)) ranged from 0.09 to 4.87 µmol CO(2) m(-2) s(-1), with the highest values observed in August and the lowest in the winter months. A logistic model gave the best fit to the relationship between hourly R(s) and soil temperature (T(s)), explaining 82% of the variation in R(s) over the annual cycle. The annual total of soil respiration estimated from the logistic model was 645±5 g C m(-2) year(-1). The performance of the logistic model was poorest during periods of high soil temperature or low soil volumetric water content (VWC), which limits the model's ability to predict the seasonal dynamics of R(s). The logistic model will potentially overestimate R(s) at high T(s) and low VWC. Seasonally, R(s) increased significantly and linearly with increasing VWC in May and July, in which VWC was low. In the months from August to November, inclusive, in which VWC was not limiting, R(s) showed a positively exponential relationship with T(s). The seasonal sensitivity of soil respiration to T(s) (Q(10)) ranged from 0.76 in May to 4.38 in October. It was suggested that soil temperature was the main determinant of soil respiration when soil water was not limiting.
中国拥有大面积的人工林，这些人工林吸收了大量的碳。然而，关于这些人工林的土壤呼吸研究相当匮乏，其土壤碳通量仍然是一个不确定因素。本研究采用自动箱式系统，测量了中国北京鹫峰 50 年生侧柏林的土壤表面通量。平均日土壤呼吸速率（R(s)）范围为 0.09-4.87 µmol CO(2) m(-2) s(-1)，8 月最高，冬季最低。逻辑模型能够最好地拟合 R(s)与土壤温度（T(s)）之间的关系，解释了 R(s)在年周期变化中的 82%。从逻辑模型估计的年总土壤呼吸量为 645±5 g C m(-2) year(-1)。逻辑模型在土壤温度高或土壤体积含水量（VWC）低的时期表现最差，这限制了模型预测 R(s)季节动态的能力。在高 T(s)和低 VWC 的情况下，逻辑模型可能会过高估计 R(s)。季节性地，在 5 月和 7 月 VWC 较低的情况下，R(s)随 VWC 的增加而显著线性增加。在 8 月至 11 月期间，VWC 不受限制，R(s)与 T(s)呈正指数关系。土壤呼吸对 T(s)的季节性敏感性（Q(10)）范围从 5 月的 0.76 到 10 月的 4.38。当土壤水分不受限制时，土壤温度是土壤呼吸的主要决定因素。
