Gutiérrez Del Arroyo Omar, Wood Tana E
Department of Biology University of Puerto Rico Río Piedras Puerto Rico.
USDA Forest Service International Institute of Tropical Forestry Rio Piedras Puerto Rico.
Ecol Evol. 2020 Dec 10;11(1):263-272. doi: 10.1002/ece3.7021. eCollection 2021 Jan.
Tropical forests are the largest contributors to global emissions of carbon dioxide (CO) to the atmosphere via soil respiration ( ). As such, identifying the main controls on in tropical forests is essential for accurately projecting the consequences of ongoing and future global environmental changes to the global C cycle. We measured hourly in a secondary tropical moist forest in Puerto Rico over a 3-year period to (a) quantify the magnitude of and (b) identify the role of climatic, substrate, and nutrient controls on the seasonality of . Across 3 years of measurements, mean was 7.16 ± 0.02 μmol CO m s (or 2,710 g C m year) and showed significant seasonal variation. Despite small month-to-month variation in temperature (4°C), we found significant positive relationships between daily and monthly with both air and soil temperature, highlighting the importance of temperature as a driver of even in warm ecosystems, such as tropical forests. We also found a significant parabolic relationship between mean daily volumetric soil moisture and mean daily , with an optimal moisture value of 0.34 m m. Given the relatively consistent climate at this site, the large range in mean monthly (7 μmol CO m s) was surprising and suggests that even small changes in climate can have large implications for ecosystem respiration. The strong positive relationship of with temperature at monthly timescales particularly stands out, as moisture is usually considered a stronger control of in tropical forests that already experience warm temperatures year-round. Moreover, our results revealed the strong seasonality of in tropical moist forests, which given its high magnitude, can represent a significant contribution to the seasonal patterns of atmospheric (CO) globally.
通过土壤呼吸作用，热带森林是全球向大气排放二氧化碳（CO₂）的最大贡献者。因此，确定热带森林中土壤呼吸作用的主要控制因素对于准确预测当前及未来全球环境变化对全球碳循环的影响至关重要。我们在波多黎各的一片次生热带湿润森林中，进行了为期3年的每小时一次的土壤呼吸测量，目的是：（a）量化土壤呼吸的强度；（b）确定气候、底物和养分控制因素对土壤呼吸季节性变化的作用。在3年的测量期间，平均土壤呼吸速率为7.16±0.02 μmol CO₂ m⁻² s⁻¹（或2710 g C m⁻² 年⁻¹），并呈现出显著的季节性变化。尽管温度的月际变化较小（约4°C），但我们发现每日和每月的土壤呼吸速率与气温和土壤温度均呈显著正相关，这突出了温度作为土壤呼吸驱动因素的重要性，即使在热带森林这样温暖的生态系统中也是如此。我们还发现平均每日土壤体积含水量与平均每日土壤呼吸速率之间存在显著的抛物线关系，最佳含水量值为0.34 m³ m⁻³。鉴于该地点气候相对稳定，平均每月土壤呼吸速率的较大范围（约7 μmol CO₂ m⁻² s⁻¹）令人惊讶，这表明即使是气候的微小变化也可能对生态系统呼吸产生重大影响。在月度时间尺度上，土壤呼吸速率与温度的强正相关关系尤为突出，因为在常年温暖的热带森林中，水分通常被认为是对土壤呼吸更强的控制因素。此外，我们的结果揭示了热带湿润森林中土壤呼吸的强烈季节性，鉴于其较高的强度，这可能对全球大气CO₂的季节性模式做出重大贡献。
