In mountain grasslands drought has distinct transient effects on soil nitrogen cycling and bacterial and archaeal ammonia-oxidizers (AOB and AOA), which could have been related to a niche differentiation of these two groups at increasing NH4+ levels. However, the effective strength of drought was modulated by the level of grassland management.

Atmospheric loss of N from savanna soil was dominated by N2 emissions (82-99% of total N loss to atmosphere). Nitric oxide emissions significantly contributed at 50% WFPS; high temperatures and N2O emissions were negligible. Based on a simple upscale approach we estimated annual loss of N to the atmosphere at 7.5kg yr-1. N2O emission was low for most samples, but high for a small subset of cores at 75% WFPS (due to short periods where such conditions occur this has little effect on totals).

We have investigated the presence of archaea as well as their amoA gene diversity in aerosol particles collected over 1 year in central Europe and found that, within the 16S and amoA gene, Thaumarchaeota prevail and experience a diversity peak in fall, while only few Euryarchaeota were detected primarily in spring. We also compared the results with airborne archaea from Cape Verde and observe that the proportions of Euryarchaeota seem to be enhanced in coastal air compared to continental air.

In this study soil CO2 efflux was measured at a montane mixed-forest site and a subalpine spruce forest site. Each site consisted of an undisturbed forest and two adjacent windthrow areas, differing regarding the time since disturbance. The combination of chronosequence and direct time-series approaches enabled us to investigate soil CO2 efflux dynamics over 12 years post-disturbance. According to our estimates, ~ 500 to 700 g C m-2 yr-1 are released via soil CO2 efflux from younger windthrows.

Estimates of ocean carbon uptake from ocean biogeochemical models are key to our understanding of the global carbon cycle. Such estimates suggest that ocean carbon uptake is decreasing due to climate change, and particularly due to strengthening of the Southern Hemisphere winds. We show that these model-based estimates are highly uncertain due to poorly resolved physical processes (mesoscale ocean eddies) and uncertainty in the observed surface wind forcing used to drive the models.

Storm-enhanced export of particulate organic carbon in a mountainous headwater stream increased nonlinearly above thresholds of precipitation and discharge, far exceeding the relatively small increases of dissolved organic carbon. Particulate organic carbon exported during extreme storm events provide potential sources of reactive organic components that can rapidly biodegrade and form disinfection byproducts such as trihalomethanes in the headwater stream.

The ratio of nitrogen-15 to nitrogen-14 of macroalgae has been termed the DNA of sewage. Higher amounts of N-15 have been suggested to indicate the influence of sewage-derived N. But what exactly does the ratio of 15N/14N record? We found that the nitrogen isotopic ratio was dependent upon not only the value in the water but also its concentration of nitrate. At low concentration there was little fractionation, but at higher values the uptake by algae left more of the N-15 in the water.

This study disentangles the response of forest and grassland to heatwaves, to interpret the findings of Teuling et al. (2010), who found systematically higher temperatures over forests than over grasslands in European heatwaves. By means of a study with a simple coupled land–atmosphere model, we show that the increase in stomatal resistance of vegetation under high values of vapor pressure deficit explains most of the differences and that this increase is enhanced by boundary layer feedbacks.