 |
| Titel |
Labile carbon regulates protease activity and nitrogen acquisition in boreal forest topsoil. |
| VerfasserIn |
A. Linden, J. Heinonsalo, M. Oinonen, E. Sonninen, E. Hilasvuori, J. Pumpanen |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062367
|
|
|
|
|
|
| Zusammenfassung |
| In boreal zone, soil organic matter (SOM) contains a substantial amount of recalcitrant
material and forms a large nitrogen pool. However, this pool is to a great extent inaccessible
to plants, due to its low decomposability. Although, the nitrogen supply is the most limiting
factor of net ecosystem production (NEP) in boreal forests, it has been speculated that as a
result of the accelerated decomposition of SOM induced by climate warming, part of
this nitrogen pool could be released. It has also been shown that a substantial proportion of
gross primary production (GPP) is allocated below ground and acts as an energy
source for decomposing rhizomicrobial organisms, and that changes in the GPP rate
could therefore increase the belowground turn over rate of otherwise recalcitrant
nitrogen-rich SOM. We were studying the effects of increasing labile carbon input
on the symbiotic microbial N acquisition and protease activities in a controlled
microcosm experiment. We compared the natural abundance of isotope ratios of 13C
and 14C in soil CO2efflux, protease enzyme activity, natural abundance of 15N in
the needles, and microbial biomass in microcosms containing bare soil and tree
seedlings. In addition, we had treatments were additional energy was given to the
bare soil and seedling microcosms in the form of glucose. The age of the CO2
originating from the decomposition process of SOM was older in all treatments where
easily decomposable carbon (energy) was available for soil microorganisms. The
increased natural abundance of 15N in the needles of the seedlings treated with
glucose, suggests a shift in nitrogen acquisition to different SOM pool, which was
reflected strongly to the total N content of the SOM and evolving 13C signature
in soil CO2 efflux. The protease activity was highest in treatments with artificial
glucose addition. Our results suggest that the increased input of easily available
carbon from aboveground enables the decomposition of recalcitrant nitrogen rich
compounds in SOM and could therefore increase the nitrogen supply to plants. |
|
|
|
|
|
|