GEOGRAPHY

Researchers obtained soil respiration to determine the influencing factors


He Jinsheng’s team used a multi-channel soil carbon flux automatic measurement system to determine soil respiration Photo courtesy of Lanzhou University

Recently, the team of Professor He Jinsheng of Lanzhou University published the results entitled “Fixed respiratory rings may bring important deviations in long-term measurement of soil respiration” in “Research Methods of Ecology and Evolution”, and proposed corresponding correction methods to provide a basis for the standardized measurement of soil respiration in the future.

Soil respiration refers to the process by which the soil releases carbon dioxide. Like animal respiration, plant roots, animals, fungi and bacteria in the soil release large amounts of carbon dioxide during metabolic activities. Soil respiration is the second largest carbon flux in terrestrial ecosystems after photosynthesis, and about 9 times the total anthropogenic carbon emissions. Small changes in soil respiration can lead to significant changes in atmospheric carbon dioxide concentrations and soil carbon pools. Therefore, the accurate measurement of soil respiration is not only related to the correct understanding of the ecosystem carbon cycle process, but also directly related to the assessment of ecosystem carbon budget and soil health.

Soil respiration not only changes with the biological and abiotic factors of the soil, but also closely related to the photosynthesis and growth status of plants. Affected by these factors, soil respiration is in the process of highly dynamic change, showing obvious diurnal, seasonal and interannual changes. Therefore, accurate measurement of soil respiration requires long-term, high-frequency dynamic monitoring. At present, the internationally accepted measurement method is the long-term automatic monitoring system of soil carbon flux, such as the Li-8150 and Li-8250 measurement systems of the American Gene Corporation. The operation of the long-term monitoring system for soil carbon flux relies on the base of the breathing ring installed on the soil surface. However, it has been found that the installation time of the soil breathing ring may affect the accurate measurement of soil respiration during the field measurement, but there is no systematic study of this phenomenon internationally.

He Jinsheng’s team conducted continuous measurements of soil respiration for three growing seasons (2017-2019) at the National Field Scientific Observation and Research Station of Qinghai Haibei Alpine Grassland Ecosystem in the northeast of the Qinghai-Tibet Plateau, and analyzed the biological and abiotic factors inside and outside the soil ring. This study not only quantifies the effect of respirator installation time on soil respiration measurement, but also reveals potential causes of measurement bias.

Studies have found that the effect of long-term soil breathing ring installation on soil respiration rate varies over time. In the second and third growing seasons after long-term respiration ring installation, the soil respiration rate decreased by 8.9% and 18.2%, respectively, especially from the middle of the second growing season, and the long-term base installation caused the soil respiration rate to decrease rapidly. The study further found that in the later stage of long-term respiratory ring installation, the significant decrease of root biomass, soil microbial biomass carbon and the significant increase of soil bulk density were the main reasons for the underestimation of soil respiration. These findings suggest that the potential influencing factor of respirator installation time should be considered when interpreting soil respiration data based on long-term breathing ring base measurements. At the same time, it is suggested that the use of short-term breathing rings to measure soil respiration or the position of respiratory rings should be changed in time after more than 1-2 years to reduce the measurement deviation caused by the installation time of respiratory rings. (Source: China Science News, Wen Caifei, Faisha)

Related paper information:https://doi.org/10.1111/2041-210X.14056



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