Soil respiration on field mesocosms 2022

Soil respiration rates were meticulously assessed on two separate occasions: July 19 and September 20, 2022. These rates were quantified by capturing the flux of CO2 emanating from the soil surface, utilizing the widely recognized Closed Dynamic Chamber method. The methodology employed an Li-8100A field respirometer from Li-Cor Biosciences, USA, in conjunction with polypropylene rings that featured an internal diameter of 105 mm. These rings were embedded into the soil of the mesocosms at a depth of 3 cm to ensure a consistent measurement environment. Concurrent with the respiration rate determinations, soil temperature readings were taken using a precise soil thermometer, part of the respirometer's assembly, capable of 0.1°C resolution. This thermometer, an Omega 88311E model from OMEGA Engineering, UK, provided high accuracy in monitoring the thermal state of the soil. Additionally, soil volumetric moisture content was accurately gauged to within 0.1% using a ThetaProbe ML2 sensor from Delta-T Devices, UK, which was interfaced with the respirometer's control unit for seamless data integration.To ensure a comprehensive understanding of the environmental conditions, both soil humidity and temperature were recorded at the same 5 cm depth as the respiration measurements. Furthermore, air temperature was also tracked, thanks to a built-in sensor in the respirometer's chamber, to account for atmospheric influences on the soil's respiratory activity. The timing of the measurements was carefully selected to reflect typical daytime conditions, consistently conducted between 10 a.m. and 4 p.m. This scheduling minimized variations in diurnal temperature and light that could potentially influence the respiration readings. Experimental design was structured to facilitate robust data analysis, with mesocosms arranged in clusters of eight replicates. These clusters were further organized into three lines, consisting of five clusters each, to standardize the spatial distribution of the measurement points. On the latter date of September 20, additional comparative data was collected from the surrounding meadows adjacent to the experimental site. Eight background soil respiration measurements were conducted to provide a baseline for the experimental readings. To minimize any potential systematic bias due to the natural daily fluctuations of soil and air temperatures, the order in which the mesocosms were measured was deliberately varied between the two dates. This careful randomization ensured that the temporal dynamics did not skew the results, thereby enhancing the reliability of the study's findings.

本研究于2022年7月19日与9月20日两个独立时段，对土壤呼吸速率开展了精细化测定。该速率通过捕获土壤表面释放的二氧化碳（CO₂）通量进行定量，采用了业界广泛认可的密闭动态箱法（Closed Dynamic Chamber）。实验装置采用美国Li-Cor Biosciences公司生产的Li-8100A型野外呼吸仪，搭配内径105 mm的聚丙烯环；将此类环以3 cm深度嵌入中型生态箱（mesocosm）的土壤中，以保障测定环境的一致性。
在测定土壤呼吸速率的同时，借助呼吸仪配套的高精度土壤温度计开展土壤温度读数采集，该温度计分辨率可达0.1℃。这款来自英国OMEGA Engineering公司的Omega 88311E型温度计，可高精度监测土壤热状况。此外，采用英国Delta-T Devices公司生产的ThetaProbe ML2型传感器，精准测定土壤体积含水量，测定精度可达0.1%；该传感器与呼吸仪控制单元相连，实现数据无缝集成。
为全面掌握环境条件，土壤湿度与温度的测定深度与呼吸速率测定一致，均为5 cm。此外，借助呼吸仪箱体内置的传感器同步记录空气温度，以考量大气环境对土壤呼吸活动的影响。
测定时段经过精心选择，均覆盖典型日间条件，统一定于每日上午10时至下午4时开展。该时段安排尽可能减小昼夜温度与光照波动对呼吸速率测定结果的潜在干扰。
实验设计旨在保障数据分析的可靠性，将中型生态箱以8个重复为一组进行分组；每组集群进一步划分为3条排列，每条包含5个集群，以此规范测定点位的空间分布。
在第二次测定时段（9月20日），还在实验场地周边的邻近草地采集了对照数据：开展8次背景土壤呼吸速率测定，为实验测定结果提供参照基准。
为规避因土壤与空气温度自然日波动带来的系统性偏差，两次测定的中型生态箱测定顺序均经过刻意调整。该严谨的随机化设计确保了时间动态不会干扰测定结果，进而提升了本研究结论的可靠性。