Data from: Soil drainage facilitates earthworm invasion and subsequent carbon loss from peatland soil

1. Human activities have been a significant driver of environmental
changes with tremendous consequences for carbon dynamics. Peatlands are
critical ecosystems because they store ~30% of the global soil organic
carbon pool and are particularly vulnerable to anthropogenic changes. The
Zoige peatland on the eastern Tibet Plateau, as the largest alpine
peatland in the world, accounts for 1‰ of global peat soil organic carbon
storage. However, this peatland has experienced dramatic climate change
including increased temperature and reduced precipitation in the past
decades, which likely is responsible for a decline of the water table and
facilitated earthworm invasion, two major factors reducing soil organic
carbon (SOC) storage of peatlands. 2. Because earthworms are often more
active in low- than in high- moisture peatlands, we hypothesized that the
simultaneous occurrence of water table decline and earthworm invasion
would synergistically accelerate the release of SOC from peatland soil. We
conducted a field experiment with a paired split-plot design, i.e.
presence vs. absence of the invasive earthworms (Pheretima aspergillum)
nested in drained vs. undrained plots, respectively, for three years
within the homogenous Zoige peatland. 3. Water table decline significantly
decreased soil water content and bulk density, resulting in a marked
reduction of SOC storage. Moreover, consistent with our hypothesis,
earthworm presence dramatically reduced SOC in the drained but not in the
undrained peatland through the formation of deep burrows and decreasing
bulk density of the lower soil layer over three years. The variation in
SOC likely was due to changes in aboveground plant biomass, root growth,
and earthworm behavior induced by the experimental treatments.4. Synthesis
and applications. We suggest that incentive measures should be taken to
prevent further water table decline and earthworm invasion for maintaining
the soil C pool in Zoige peatland. Artificial filling of drainage canals
should be implemented to increase the water table level, facilitating the
recovery of drained peatlands. Moreover, the dispersal of earthworms and
their cocoons attached to the roots of crop plants and tree saplings from
low-lying areas to the Zoige region should be prevented.