Pulse Effect of Precipitation: Spatial Patterns and Mechanisms of Soil Carbon Emissions

Abstract

The rapid and strong release of CO2 caused by precipitation (known as the pulse effect) is a common phenomenon that significantly affects ecosystem C cycling. However, the degree to which the pulse effect occurs overlarge regional scales remains unclear. In this study, we conducted continuous and high-frequency measurements of soil CO2 release rates (Rs) for 48 h after simulated precipitation, along a precipitation gradient of different grassland types (i.e., meadow, typical, and desert) in Inner Mongolia, China. Pulse effects were assessed using the maximum Rs (Rsoil–max) and accumulated CO2 emissions (ARs–soil). Strong precipitation pulse effects were found in all sites; however, the effects differed among grassland types. In addition, an apparent decrease in both Rsoil–max and ARs–soil was observed from the east to west, i.e., along the decreasing precipitation gradient. ARs–soil values followed the order: temperate meadow grassland (0.097 mg C g–1 soil) > typical temperate grassland (0.081 mg C g–1 soil) > temperate desert grassland (0.040 mg C g–1 soil). Furthermore, Rsoil–max and ARs–soil were significantly positively correlated with soil quality (SOC, POC, and N, etc.; P < 0.01). ARs–soil (P < 0.05) and ARs–SOC (P < 0.01) were significantly affected. ARs–soil and ARs–SOC were also positively correlated with soil microbial biomass significantly (P < 0.05). Rsoil–max and ARs–soil had similar spatial variations and controlling mechanisms. These results greatly support the substrate supply hypothesis for the effects of precipitation pulses, and provide valuable information for predicting CO2 emissions. Our findings also verified the significant effect of soil CO2 release from precipitation pulses on the grasslands of arid and semi-arid regions. Our data provide a scientific basis for model simulations to better predict the responses of ecosystem carbon cycles in arid and semi-arid regions under predicted climate change scenarios.

Soil Moisture Affects the Rapid Response of Microbes to Labile Organic C Addition

“…As the study site is an arid/semi-arid region with a low soil moisture content in its natural state, soil microbes are sensitive to changes in moisture. Lower soil moisture leads to lower microbial activity (Jiang et al, 2021) and higher soil moisture tends to form an anaerobic environment to inhibit microbial activity (Kool et al, 2011). Thus, we hypothesized that, either extremely high or low moisture content is not conducive to microbial decomposition of LOC and SOM; conversely, optimal moisture content conditions (50-70% WHC) would lead to greater CO 2 emissions.…”

“…Numerous studies have investigated SOM priming; however, the short-term processes involved in the microbial response to LOC inputs remains unclear. This is due to the rapid response of soil microbes to exogenous substrate inputs, as well as the limitations of measuring technologies (Wang et al, 2016a;Xu et al, 2020;Jiang et al, 2021).…”

Effects of broiler litter age and application rate on nutrient mineralization under laboratory condition

“…For all treatments, we found a general trend of a slight increase in soil pH after the addition of litter, which reached its peak on day 60; after that, an occasional increase was found. When water is added to the soil, the microorganisms get active and break down the soil's organic matter and BL (Jiang et al., 2021; Sharpley et al., 1993) through enzyme activity and alters the soil's acidity (Das et al., 1993; Helyar, 1976). On each sampling date, we observed a general pattern of higher pH in soil with a greater BL application rate and older age (18MH and 30MH) than soil with a lower BL application rate and younger age (18ML and soil with 5 Mg ha −1 of 30‐month‐old BL application [30ML]).…”

Short-Term Soil CO2 Concentration Responses to Precipitation Events in Karst Land with Diverse Vegetation Coverage in Southwestern China

“…In addition, rainfall can promote microbial activities and strongly stimulate the production of soil CO 2 , leading to an increase in the soil CO 2 concentration, which is called the “stimulation effect”. , Previous studies indicated that organic matter and microorganisms can affect the stimulation effect, increasing the release of CO 2 during rainfall . Especially in arid and semiarid regions, the lower water content has limited impacts on microorganism activities.…”

“…46,55 Previous studies indicated that organic matter and microorganisms can affect the stimulation effect, increasing the release of CO 2 during rainfall. 56 Especially in arid and semiarid regions, the lower water content has limited impacts on microorganism activities. When it rains, the soil water content increases sharply, leading to the rapid utilization of available organic matter preserved in arid environments by microorganisms.…”