Two aspects on soil nitrogen dynamics in a climate change context

• Climate change is expected to alter the nitrogen availability and dynamics and, as a consequence, affect plant community composition and production. The general consensus today is that increased temperature will lead to greater microbial activity and more plant-available nitrogen Although, there are hardly any studies on how nitrification and denitrification varies with altitude, and no previous studies in high arctic-alpine tundra landscapes. If temperature is an important factor limiting microbes in tundra areas, and the mean annual temperature falls with increasing altitude, it would be expected that nitrification and denitrification rates also would decrease with increasing altitude and thereby reflect a reverse Climate Change gradient. Here, we compare nitrification enzyme activity (NEA) and denitrification enzyme activity (DEA) rates in dry heaths a along an altitudinal gradient with the effects of climatic warming using Open Top Chambers (OTCs). This study was conducted at Latnjajaure Field Station (LFS) located in the midalpine region in northern Sweden. LFS is also the Swedish field site for the International Tundra Experiment (ITEX), established in 1993. This gives an opportunity to investigate long-term effect of climatic warming on as well as an altitudinal gradient (1000m to 1365m) within a very small geographical range. The OTCs used at LFS increases the soil surface temperature by approximately 1.5ºC whereas air temperature falls with 1ºC for every hundred meter of increased altitude. To analyse the NEA and DEA we used an anaerobic incubation technique, based on acetylene inhibition technique, resulting in N2O as the only end product, which is then analysed by gas chromatography. The results contradict each other. The gradient study showed a decreased NEA and DEA rates with falling altitude, whereas the warming experiment show a slight increase due to the temperature enhancement by OTCs, although, there is no significant OTC effect. DEA was correlated with NEA and SOM, explaining part of the altitudinal variation. The results indicate that the altitudinal temperature decline did not reduce NEA and DEA rates, and although some of the variables measured here might explain part of the results in this study, they are not conclusive.

Subject headings

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Keyword

Arctic

Climate Change

Denitrification

ITEX

Nitrification

Publication and Content Type

vet (subject category)

kon (subject category)