Winter soil respiration is a very important component of the annual soil carbon flux in some ecosystems. We hypothesized that, with all other factors being equal, shorter winter SR result in reduced contribution to annual soil C flux. In this study, the contribution of winter soil respiration to annual soil respiration was measured for three sites (grassland: dominated by Artemisia sacrorum, Bothriochloa ischaemum and Themeda japonica; shrubland: dominated by Vitex negundo var. heterophylla; plantation: dominated by Populus tomatosa) in a mountainous area of north China. Diurnal and intra-annual soil CO2 flux patterns were consistent among different sites, with the maximum soil respiration rates at 12∶00 or 14∶00, and in July or August. The lowest respiration rates were seen in February. Mean soil respiration rates ranged from 0.26 to 0.45 µmol m−2 s−1 in the winter (December to February), and between 2.38 to 3.16 µmol m−2 s−1 during the growing season (May-September). The winter soil carbon flux was 24.6 to 42.8 g C m−2, which contributed 4.8 to 7.1% of the annual soil carbon flux. Based on exponential functions, soil temperature explained 73.8 to 91.8% of the within year variability in soil respiration rates. The Q10 values of SR against ST at 10 cm ranged from 3.60 to 4.90 among different sites. In addition, the equation between soil respiration and soil temperature for the growing season was used to calculate the “modeled” annual soil carbon flux based on the actual measured soil temperature. The “measured” annual value was significantly higher than the “modeled” annual value. Our results suggest that winter soil respiration plays a significant role in annual soil carbon balance, and should not be neglected when soil ecosystems are assessed as either sinks or sources of atmospheric CO2.
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机译：在某些生态系统中，冬季土壤呼吸是每年土壤碳通量的非常重要的组成部分。我们假设，在所有其他因素相同的情况下，较短的冬季SR导致对年土壤C通量的贡献减少。在这项研究中，测量了三个地点（草地：sa蒿、,藜和日本大Theme；灌木林：以紫荆Vitex negundo var.heterophylla为主；人工林：以Populus Tomatosa为主）的冬季土壤呼吸对年度土壤呼吸的贡献。在中国北方的山区。不同地点的土壤日间和年内CO2通量模式一致，最大土壤呼吸速率分别为12：00或14：00以及7月或8月。最低的呼吸速率是2月。冬季（12月至2月）的平均土壤呼吸速率为0.26至0.45 µmol m −2 s -1 ，介于2.38至3.16 µmol m −之间在生长季节（5月至9月）为2 s −1 。冬季土壤碳通量为24.6至42.8 g C m −2 ，占年度土壤碳通量的4.8％至7.1％。基于指数函数，土壤温度解释了土壤呼吸速率年内变化的73.8％至91.8％。在10 cm处，SR对ST的Q10值在不同部位之间为3.60至4.90。此外，使用土壤呼吸和生长季节的土壤温度之间的方程式，根据实际测得的土壤温度来计算“模拟的”年度土壤碳通量。 “测得”的年值明显高于“模型化”的年值。我们的结果表明，冬季土壤呼吸作用在每年的土壤碳平衡中起着重要作用，并且当土壤生态系统被评估为大气CO2的汇入或汇出时，不应忽略。
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