Can Soil Respiration Estimate Neglect the Contribution of Abiotic Exchange?

Motivated by increasing atmospheric carbon dioxide and the climate changes it produced, the world’s scientific community made a huge effort to investigate the sources and sinks in the global carbon cycle. It was demonstrated that the global CO₂ budget cannot be balanced unless a “missing carbon sink” is involved. Numerous studies claimed to find the missing sink, but none of them were widely accepted.

Alkaline soils are widely distributed over arid and semi-arid regions, occupying about 10%–15% of arid and semi-arid soils. The arid and semi-arid soils represent 30% of the earth’s land surface and their area may further increase in this century under the current climatic conditions because of the global trend towards increasing desertification.

To examine whether the contribution of abiotic exchange to CO₂ flux can be neglected when estimating soil respiration in arid alkaline soils and estimate the role of arid alkaline soils in the global carbon cycle, CHEN Xi et al., on the basis of utilizing meteorological and soil data collected from the Xinjiang and Central Asia Scientific Data Sharing Platform, incorporated the widely recognized Q₁₀ model with an abiotic module as suggested by a previous study, and then quantified soil respiration and approximated the contribution of abiotic exchange from three ecosystems (alkaline-saline desert, abandoned farmland and oasis farmland) of Sangong and Tarim River Basins in Xinjiang, China.

The results show that the parameters of the incorporated Q₁₀ model are universally applicable, and then soil respiration in alkaline soils of arid areas cannot be interpreted purely in terms of biotic processes since the contribution of abiotic exchange to CO₂ flux is un-neglectable. The concept of alkaline soil respiration should be reconciled as soil organic respiration (the root/microbial respiratory component) and soil inorganic respiration (abiotic CO₂ exchange). With parameters in the incorporated Q₁₀ model hypothetically representing global convergent values, soil inorganic respiration represents almost half of the total soil respiration in alkaline lands.

The results suggests that alkaline soils in arid lands are the location of the long-sought “missing carbon sink”. The study was published in Journal of Arid Land in April 2014.