Potential Arctic tundra vegetation shifts in response to changing temperature, precipitation and permafrost thaw
Over the past decades, vegetation and climate have changed significantly in the Arctic. Deciduous shrub cover is often assumed to expand in tundra landscapes, but more frequent abrupt permafrost thaw resulting in formation of thaw ponds could lead to vegetation shifts towards graminoid-dominated...
Main Authors: | , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2016-11-01
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Series: | Biogeosciences |
Online Access: | https://www.biogeosciences.net/13/6229/2016/bg-13-6229-2016.pdf |
Summary: | Over the past decades, vegetation and
climate have changed significantly in the Arctic. Deciduous shrub
cover is often assumed to expand in tundra landscapes, but more frequent
abrupt permafrost thaw resulting in formation of thaw ponds could lead to
vegetation shifts towards graminoid-dominated wetland. Which factors drive
vegetation changes in the tundra ecosystem are still not sufficiently clear.
In this study, the dynamic tundra vegetation model, NUCOM-tundra (NUtrient
and COMpetition), was used to evaluate the consequences of climate change
scenarios of warming and increasing precipitation for future tundra
vegetation change. The model includes three plant functional types (moss,
graminoids and shrubs), carbon and nitrogen cycling, water and permafrost
dynamics and a simple thaw pond module. Climate scenario simulations were
performed for 16 combinations of temperature and precipitation increases in
five vegetation types representing a gradient from dry shrub-dominated to
moist mixed and wet graminoid-dominated sites. Vegetation composition
dynamics in currently mixed vegetation sites were dependent on both
temperature and precipitation changes, with warming favouring shrub dominance
and increased precipitation favouring graminoid abundance. Climate change
simulations based on greenhouse gas emission scenarios in which temperature
and precipitation increases were combined showed increases in biomass of both
graminoids and shrubs, with graminoids increasing in abundance. The
simulations suggest that shrub growth can be limited by very wet soil
conditions and low nutrient supply, whereas graminoids have the advantage of
being able to grow in a wide range of soil moisture conditions and have
access to nutrients in deeper soil layers. Abrupt permafrost thaw initiating
thaw pond formation led to complete domination of graminoids. However, due to
increased drainage, shrubs could profit from such changes in adjacent areas.
Both climate and thaw pond formation simulations suggest that a wetter tundra
can be responsible for local shrub decline instead of shrub expansion. |
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ISSN: | 1726-4170 1726-4189 |