Wood Tana E, Detto Matteo, Silver Whendee L
International Institute of Tropical Forestry, USDA Forest Service, Río Piedras, Puerto Rico, United States of America ; Fundación Puertorriqueña de Conservación, San Juan, Puerto Rico, United States of America.
PLoS One. 2013 Dec 2;8(12):e80965. doi: 10.1371/journal.pone.0080965. eCollection 2013.
Precipitation and temperature are important drivers of soil respiration. The role of moisture and temperature are generally explored at seasonal or inter-annual timescales; however, significant variability also occurs on hourly to daily time-scales. We used small (1.54 m(2)), throughfall exclusion shelters to evaluate the role soil moisture and temperature as temporal controls on soil CO2 efflux from a humid tropical forest in Puerto Rico. We measured hourly soil CO2 efflux, temperature and moisture in control and exclusion plots (n = 6) for 6-months. The variance of each time series was analyzed using orthonormal wavelet transformation and Haar-wavelet coherence. We found strong negative coherence between soil moisture and soil respiration in control plots corresponding to a two-day periodicity. Across all plots, there was a significant parabolic relationship between soil moisture and soil CO2 efflux with peak soil respiration occurring at volumetric soil moisture of approximately 0.375 m(3)/m(3). We additionally found a weak positive coherence between CO2 and temperature at longer time-scales and a significant positive relationship between soil temperature and CO2 efflux when the analysis was limited to the control plots. The coherence between CO2 and both temperature and soil moisture were reduced in exclusion plots. The reduced CO2 response to temperature in exclusion plots suggests that the positive effect of temperature on CO2 is constrained by soil moisture availability.
降水和温度是土壤呼吸的重要驱动因素。通常在季节或年际时间尺度上探讨湿度和温度的作用；然而，在小时到日的时间尺度上也存在显著的变异性。我们使用小型（1.54平方米）的穿透雨排除遮蔽设施，来评估土壤湿度和温度作为波多黎各潮湿热带森林土壤二氧化碳排放的时间控制因素的作用。我们在对照区和排除区（n = 6）测量了6个月的每小时土壤二氧化碳排放、温度和湿度。使用正交小波变换和哈尔小波相干分析每个时间序列的方差。我们发现在对照区，土壤湿度与土壤呼吸之间存在强烈的负相干，对应于两天的周期。在所有样地中，土壤湿度与土壤二氧化碳排放之间存在显著的抛物线关系，土壤呼吸峰值出现在体积土壤湿度约为0.375立方米/立方米时。我们还发现在较长时间尺度上，二氧化碳与温度之间存在微弱的正相干，并且当分析仅限于对照区时，土壤温度与二氧化碳排放之间存在显著的正相关关系。在排除区，二氧化碳与温度和土壤湿度之间的相干性降低。排除区中二氧化碳对温度的响应降低表明，温度对二氧化碳的正向影响受到土壤水分有效性的限制。
