Respiration in soils collected from the REU synoptic sample grid in the Andrews Experimental Forest, 1994-1995

The 1993 (SP005) sampling grid was expanded to 183 sites providing a more comprehensive sampling grid. Because of potential edge effects problems, all sample locations were moved at least 20 meters from the closest road or clearing. Changes from the original location are given in entity 2. CO2 is measured over a period of 41 weeks in soils collected from all of the REU synoptic sample sites in the summer of 1994. Soils were weighted at the same time that respiration was assayed and moisture content was maintained at the same level throughout the series. The time period represented by this data is 15 September 1994 to 12 July 1995. In the initial stages, CO2 concentrations were assayed every week, after 15 weeks, the incubation period was extended to 2 weeks. After the incubation vessels were assayed, the headspace was flushed with lab air and the moisture was adjusted with sterile deionized water. Results show that there was a very high correlation between respiration rates during the 1st and 3rd weeks (r = 0.96) suggesting that the two week incubation period we us as an indicator of initial concentrations of labile carbon is valid. There was also a high correlation between rates observed within the first week and rates observed after 41 weeks (r = 0.85) suggesting that the initial rates provide a good relative guide to rates observed after 10 months. In addition, respiration rates after 41 weeks were 80% of those observed during the first week.

1993年的(SP005)采样网格被扩展至183个样点，以构建覆盖范围更全面的采样网格。鉴于潜在的边缘效应问题，所有样点均向远离最近道路或空地的方向至少移动了20米。样点相对于原始位置的变动详情详见实体2。1994年夏季，研究人员针对所有REU概览采样样点采集的土壤样本，开展了为期41周的二氧化碳（CO₂）浓度测定。土壤称重与呼吸速率测定同步进行，且整个实验周期内土壤含水量始终维持恒定。本数据集对应的时间跨度为1994年9月15日至1995年7月12日。实验初期，每周开展一次CO₂浓度测定；在第15周后，培养周期延长至每两周一次。完成培养容器的测定后，需用实验室空气冲洗顶空空间，并使用无菌去离子水调整土壤含水量。结果表明，第1周与第3周的呼吸速率之间存在极强相关性（r=0.96），这证实以两周培养周期作为活性碳初始浓度的指示指标具备合理性与有效性。此外，第1周观测到的呼吸速率与41周后观测到的呼吸速率之间也存在较高相关性（r=0.85），说明初始呼吸速率可作为10个月后观测速率的可靠相对参考依据。同时，41周后的呼吸速率仅为第1周观测值的80%。