Warming, permafrost thawing and nitrogen availability are drivers of
increasing plant growth and species richness on the Tibetan Plateau
Abstract
Permafrost-affected ecosystems are prone to warming and thawing, which
can increase the availability of subsurface nitrogen (N) with
consequences for otherwise N-limited tundra vegetation. Here, we show
that the upper permafrost of the Tibetan Plateau is subject to thawing
and that the upper permafrost zone is rich in ammonium. Furthermore, a
five-year 15N tracer experiment showed that
long-rooted plant species were able to utilize
15N-labeled N at the permafrost table and far below
the main root zone. A 20 years survey is used here to document that
long-rooted plant species had a competitive advantage at sites subject
to warming and that both plant composition and growth were significantly
correlated with permafrost thawing and changes in nitrogen availability.
Our experiment documents a clear feedback mechanism of climate warming,
which releases plant–available N favoring long-rooted plants and
explains important changes in plant composition and growth across sites
on the Tibetan Plateau.