Effect of pulse precipitation on soil CO2 release in different grassland types on the Tibetan Plateau

Abstract

Precipitation events may rapidly alter soil moisture, and potentially result in a large quantity of soil CO2 release in a short term. However, the effect of pulse precipitation on soil CO2 release among different grassland types on the Tibetan Plateau remains unclear. Here, we investigated soil CO2 release following pulse precipitation in the meadows, grasslands, and deserts of the Tibetan Plateau along a precipitation gradient. This was achieved using a new device that measures soil respiration rate (RS) continuously and frequently, thus allowing us to conduct 48-h simulation incubation experiments. We evaluated the pulse effect using the indices of the accumulation of microbial respiration carbon emission per gram of soil (ARs-Soil) and the accumulation of microbial respiration carbon emission per gram of soil organic carbon (SOC) (ARs-SOC). The results showed strong precipitation pulse effects, with ARs-Soil and ARs-SOC differing among the three grassland types owing to the soil properties, climate factors, and microbial biomass. ARs-Soil was higher in alpine meadows than in alpine deserts and alpine grasslands because of the higher SOC. Conversely, ARs-SOC was higher in alpine deserts (8.73 ± 3.37 mg C g−1 SOC) than in alpine meadows (2.66 ± 0.91 mg C g−1 SOC) and alpine grasslands (4.39 ± 0.84 mg C g−1 SOC). ARs-SOC/phospholipid fatty acid (PLFA) showed trends similar to ARs-SOC, thereby indicating that microbes in alpine desert were more sensitive to changes in soil moisture. Overall, the results show that the response of soil CO2 release to pulse precipitation in the Tibetan Plateau grasslands is related to grassland type. Furthermore, owing to the stronger response of soil microbes to pulse precipitation in arid regions, microbial responses to changing precipitation levels may be stronger under conditions of increasing drought in the future.