Impact of soil temperature-difference on desert carbon-sink

The global carbon-cycle is crucial for climate change. Desert, which has
long been neglected in the global carbon-cycle, may sequester enormous
volumes of CO2 and play the role of a carbon-sink. As the world's
second-largest shifting desert, the Taklimakan Desert (TD) contributes
substantially to desert carbon-sinks. However, the contributions of the
internal processes of the TD to its carbon-sink and the long-term trend of
the carbon-sink under climate change are still unclear. This study will
address this important knowledge gap. Through field observations, we found
that the expansion/contraction of soil air containing CO2 caused by heat
fluctuation in shifting sand, in combination with salts/alkali chemistry
dominates the release/absorption processes of CO2 in shifting sand. The
mutual counteraction of these processes means that the TD shifting sand
acts as a stable carbon-sink that had a CO2 annual uptake of 1.60×106
t·a-1 during 2004–2017. It suggests that global shifting deserts maybe
uptake of ~2.125×108 t of CO2 per year. However, an increasing soil
temperature-difference will stimulate soil air expansion of desert and
release more CO2 into the atmosphere under climate change, causing the
shifting sand carbon-sink decrease in the TD gradually in the future.
These processes will be accelerated by positive feedback effect under
climate change and enhance regional warming. These conclusions are very
important for re-recognizing the status of deserts in the carbon-cycle,
narrowing the gap in the missing carbon-sink and assessing the global
carbon-cycle.