Diurnal pattern and characteristic of soil respiration and net ecosystem carbon exchange in alpine meadow ecosystem on the northeastern Qinghai-Tibet Plateau

Abstract

Analyzing the diurnal pattern of soil respiration is essential for understanding the potential mechanisms of carbon cycle. Additionally, long-term and high temporal frequency soil respiration observations are crucial and valuable at different time scales, particularly in alpine regions. Therefore, it is critical to conduct research on the diurnal pattern of soil respiration in areas sensitive to global warming. Here, four group (including soil respiration, heterotrophic respiration, net ecosystem carbon exchange, and net ecosystem carbon exchange under warming condition) of experiments were designed with a total 12 chambers, and data collected during growing season in 2023 (April to September) obtained by automatic observation system at hour-scale and four-parameter Gaussian equation were used to investigate the diurnal pattern of soil respiration and net ecosystem carbon exchange in alpine meadow ecosystem on the northeastern Qinghai-Tibet Plateau. The results indicated that: 1) the soil temperature was crucial factor for the variations in diurnal pattern of soil respiration and net ecosystem carbon exchange in four experiments. The response of the heterotrophic components to the diurnal variation in soil temperature induced diurnal lag between soil respiration and soil temperature, with mean lag time of 1.7 h. 2) The diurnal peak time of net ecosystem carbon exchange was 1–3 h earlier than respiration, and the diurnal variation of soil tempiration was one of the main driving forces. 3) Additionally, warming advanced the diurnal peak time of net ecosystem carbon exchange by 1.2–2 h through explaining the parameters of the Gaussian function. It also promoted microbial resistance, thereby limiting the increase in soil respiration during nighttime. The study suggested that temperature varied soil microenvironment and biochemical processes in alpine meadow ecosystem, thus affecting the diurnal pattern. Indeed, this study focused solely on traditional factors, and further investigations were needed, particularly from a biotic perspective, to validate these conclusions.