Shallow groundwater inhibits soil respiration and favors carbon uptake
in a wet alpine meadow ecosystem
Abstract
Wet alpine meadow ecosystems generally act as a significant carbon sink
due to their higher rate of photosynthesis than the rate of
decomposition. However, it remains unclear whether the low decomposition
rate is determined by low temperatures or by nearly-saturated soil
conditions. Using five years of measurements from two sites on the
Tibetan Plateau with significantly different soil water conditions, we
showed that compared to the dry site (which had a deep water table), the
much larger carbon sink at the site with a shallow groundwater was
mainly caused by the inhibiting effects of the nearly-saturated soil
condition on soil respiration rather than by the low temperature. The
findings suggested that thawing of frozen soil may partially slow down
soil carbon decomposition through increasing soil water. We highlights
that a warming-induced shrinking cryosphere may largely affect the
carbon dynamics of wet and cold ecosystems through changes in soil
hydrology.