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| Titel |
Pedogenesis and soil moisture, but not soil temperature best explain large-scale patterns of soil carbon and soil nitrogen contents in the permafrost ecosystems of Tibetan alpine grasslands |
| VerfasserIn |
F. Baumann, J.-S. He, P. Kühn, T. Scholten |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027061
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| Zusammenfassung |
| The Tibetan Plateau is an essential area to study potential feedback effects of soils to climate
change due to the rapid rise of air temperature in the past several decades as well as the large
amounts of organic carbon (Corg) stored in soils, particularly in permafrost-affected areas. In
order to predict the impact of environmental change on ecosystem functioning, it is of great
importance to understand how Corg and soil nitrogen (N) stocks are controlled under
changing climate conditions in extreme environments. We therefore investigated
the main parameters influencing Corg and N at 47 sites along a 1,200 km transect
across the high-altitude and low-latitude permafrost region of the central-eastern
Tibetan Plateau. Sites with continuous or discontinuous permafrost as well as areas
without or heavily degraded permafrost were studied for comparison of soil dynamics
under various environmental settings. Due to the high number of samples and the
large-scale transect concept, sophisticated statistical analyses showing significant
relationships between pedological parameters as well as Corg and N contents were carried
out.
The aim of the presented research was to evaluate consequences of permafrost
degradation for C and N stocks and hence nutrient supply for plants. The landscape along the
investigated transect is a patchwork of geochemically very diverse micro-ecosystems showing
variations in organic matter, nutrient stocks, plant communities and productivity. These
differences are closely related to topographic position, hydrological regimes and
consequently permafrost distribution. The main controlling mechanisms of this heterogeneity
on the Tibetan Plateau are related to different soil drainage classes.
Ecosystem ecology has traditionally focused on temperature and modeled soils mostly as
an ecosystem feature whose attributes vary strongly by thermodynamic principles.
However, the general linear regression model (GLM) suggests soil moisture as
the most important parameter explaining 64% of Corg and 60% of N variation.
The explanatory power of the GLM for C and N concentrations is significantly
improved by adding two parameters for pedogenesis to the model, i.e. CaCO3 and soil
texture. The extent of the effect of soil moisture is determined by permafrost, current
aeolian sedimentation occurring mostly on sites with permafrost degradation, and
pedogenesis.
We conclude that degradation of permafrost and corresponding changes in soil hydrology
combined with a shift from mature stages of pedogenesis to initial stages, have severe impact
on soil carbon and importantly on plant available N. Our study shows that other factors than
temperature are more important between years and sites at regional and continental scales.
Temperature dependence may rather be relevant for ecosystems when soil moisture or other
factors are not limiting or altering the relationship between temperature and soil processes.
Soil respiration data demonstrate that biomass and particularly belowground biomass as well
as soil water content are determinant of spatial variation of soil respiration across the
plateau.
In summary, both stocks (Corg and N) are coupled with complex feedback mechanisms
between permafrost, aeolian processes and the stage of pedogenesis. The latter can be
described by acidity, carbonate content and grain size distribution. |
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