 |
| Titel |
Effects of long-term elevated CO2, warming, and prolonged drought on Pleurozium-associated diazotrophic activity and abundance |
| VerfasserIn |
Kristine Dyrnum, Anders Priemé, Anders Michelsen |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088549
|
| Publikation (Nr.) |
 EGU/EGU2014-2664.pdf |
|
|
|
|
|
| Zusammenfassung |
| Nitrogen (N2) fixation is the primary natural influx of N to terrestrial ecosystems, and
changes in N2 fixation may have consequences for primary productivity and thus
ecosystem function. We studied the activity and abundance of diazotrophs associated
with the feather moss Pleurozium schreberi in a temperate heathland, after seven
years of global change manipulations, including elevated atmospheric CO2 (510
ppm), increased temperature (0.5-1.5 °C), and prolonged pre-summer droughts
(4-6 weeks /year). Acetylene reduction assay was carried out monthly to monitor
N2 fixation rates throughout one year, while nif H copy abundance, serving as a
diazotroph abundance estimate, was measured by quantitative polymerase chain reaction
(q-PCR).
Prolonged summer droughts significantly increased both N2 fixation and nif H copy
abundance, contrasting previous studies that demonstrate a direct negative correlation
between N2 fixation and water availability. A shift in the relative abundance of N2-fixing
bacteria from the green, upper parts of the moss stem to the lower, brown parts was observed.
This shift could make diazotrophs less sensitive to desiccation, enabling N2 fixation to be
upheld for longer during drought and thus causing higher abundance. Increased temperature
likewise had a positive effect on the diazotroph abundance, although this did not translate into
increased activity. Possibly, warming protects diazotrophs during extreme cold events,
while actual N2 fixation is limited by water, disregarding a rise in potential N2
fixation caused by higher abundance. Increased CO2 caused no significant diazotroph
response.
Our study showed that long-term increase in temperature and recurrent drought events
cause higher diazotroph abundance in Pleurozium schreberi and thus enhance the potential
N2 fixations rate. Furthermore, our results indicate that diazotrophs may alter colonization
patterns and thereby actively remain in the moss fraction less likely affected by desiccation.
In consequence, Pleurozium-associated N2 fixation may become an even more
important contributor of N for terrestrial ecosystems in a predicted future climate. |
|
|
|
|
|
|