Abstract

Soil respiration is a critical ecological process and is a hierarchical component of ecosystem respiration that regulates the global carbon cycle. But there is scarce knowledge on respiration dynamics in water-stressed ecosystems and the influence of biocrusts. Soil respiration-values varied from 0.099 to 0.828 µmol s⁻¹ m⁻² after extraordinary rains; after this period, recorded values were null or negative at the most (0.000 to −0.055 µmol s⁻¹ m⁻²). Shrubland soil with and without biocrusts showed the highest net CO₂ exchange values and in disturbed soil with and without biocrusts (0.067; 0.059; 0.048, and 0.023 µmol s⁻¹ m⁻²). The results showed that shrubland soil with BSC absorbed more CO₂ than the rest of the experimental variants. Accordingly, the observed low precipitation combined with high temperatures and evapotranspiration could not activate the BSC respiration process. Such an event seemed to occur under specific temperature and moisture conditions, anyhow related to extraordinary rain events to emit CO₂ to the atmosphere. Reports of negative soil respiration values in drylands are very scarce, so we discuss the possible processes that could cause this phenomenon for our study area.

摘要

土壤呼吸是一个关键的生态过程，是调节全球碳循环的生态系统呼吸的分级组成部分。但是，关于缺水生态系统中的呼吸动力学和生物结皮的影响的知识很少。大雨过后，土壤呼吸值从 0.099 到 0.828 µmol s ^-1 m ^-2不等；在此期间之后，记录的值最多为空或负（0.000 至 -0.055 µmol s ^-1 m ^-2）。有和没有生物结皮的灌木地土壤显示出最高的净 CO ₂交换值，在有和没有生物结皮的干扰土壤中（0.067；0.059；0.048 和 0.023 µmol s ^-1 m ^-2）。结果表明，与其他实验变体相比，具有BSC的灌丛土壤吸收了更多的CO _{2 。}因此，观察到的低降水结合高温和蒸散不能激活 BSC 呼吸过程。这样的事件似乎发生在特定的温度和湿度条件下，无论如何与向大气排放 CO _{2的异常降雨事件有关。}关于旱地负土壤呼吸值的报告非常稀少，因此我们讨论了可能导致我们研究区域出现这种现象的可能过程。