Soil multifunctionality is negatively related to microbial community stochasticity in restored grasslands

It is generally assumed that there is a relationship between microbial diversity and multiple ecosystem functions. Although it is indisputable that microbial diversity is controlled by stochastic and deterministic ecological assembly processes, the relationship between these processes and soil multifunctionality (SMF) remains less clear. In this study, we examined how different grassland restoration treatments, namely harvest only, topsoil removal and topsoil removal plus propagule addition, affected i) soil bacterial and fungal community stochasticity, ii) SMF, and iii) the relationship between community stochasticity and SMF. Results showed that soil microbial community stochasticity decreased in all the three restoration treatments, while SMF increased. Soil multifunctionality was found to be significantly and negatively correlated with soil microbial community stochasticity. Plant diversity and plant C/N indirectly influenced SMF by regulating the microbial community stochasticity. Our findings provide empirical evidence that when deterministic community assembly processes dominate in soils, then higher microbial functioning is expected.

Effects of topsoil removal on greenhouse gas exchange of fen paludicultures

<p>Drainage is necessary for conventional agriculture on peatlands, but this practice causes high emissions of the greenhouse gases (GHG) carbon dioxide and nitrous oxide. Paludiculture is an option to mitigate these adverse environmental effects while maintaining productive land use. Whereas the GHG exchange of paludiculture on rewetted bog peat, i.e. <em>Sphagnum</em> farming, is relatively well examined, data on GHG emissions from fen paludicultures is still very scarce. As typical fen paludiculture species are all aerenchymous plants, the release of methane is of particular interest when optimising the GHG balance of such systems. Topsoil removal is, on the one hand, an option to reduce methane emissions as well as phosphorus release upon rewetting, but on the other hand, nutrient-rich topsoils might foster biomass growth.</p><p>In this project, <em>Typha angustifolia</em>, <em>Typha latifolia</em>, and <em>Phragmites australis</em> are grown at a fen peatland formerly used as grassland. Water levels will be kept at the surface or slightly above it. In parts of the newly created polder, the topsoil will be removed. To be able to separate the effects of topsoil removal and water level, four smaller sub-polders will be installed. Greenhouse gas exchange will be measured with closed manual chambers for all three species with and without topsoil removal as well as at a reference grassland site close by.</p>

Topsoil removal and Sphagnum spreading improve the climate balance of peat bog restoration

<p>Many peatlands in Central Europe are under unsustainable drainage-based land use with high greenhouse gas emissions counteracting the aims of the Paris Agreement. After decades of drained and intensive land use many peat bogs are in pitiful state. Rewetting can stop the carbon dioxide (CO<sub>2</sub>) source function but may result in high methane (CH<sub>4</sub>) emissions and eutrophication. Further, lack of diaspores my hamper the establishment of typical bog species. Restoration measures like topsoil removal (TSR) or spreading target vegetation propagules are known to improve restoration success in fen peatlands or after peat extraction. However, experience on restoration of bogs after previous agricultural use is scarce and the climate effects of these restoration measures including carbon losses from TSR are unknown.</p><p>We installed a field trial in a drained bog in North-West Germany to explore the effect of TSR and Sphagnum spreading on greenhouse (GHG) emissions. The trial consists of seven plots (~8 x 24 m each) representing the status quo—intensive grassland use—and six different restoration approaches. Two approaches are rewetting on the original surface with or without regular biomass harvesting. The remaining four represent TSR prior rewetting where two of the four were inoculated with <em>Sphagnum</em> spp. On all plots we measured GHG fluxes fortnightly using closed chambers to obtain two-year GHG budgets. We assessed the climate effects of the status quo and the six restoration approaches by applying a radiative forcing model to the GHG budgets and to published emission factors while incorporating the effect of TSR through different depletion scenarios of the exported topsoil carbon.</p><p>Compared to the status quo, rewetting alone reduced CO<sub>2</sub> emissions by ~75% but substantially increased CH<sub>4 </sub>emissions, which were much higher than published emission factors for a similar peatland category. After TSR, on-site CO<sub>2</sub> emissions were close to 0 or—with Sphagnum spreading—net negative while CH<sub>4</sub> emissions remained very low. Based on our GHG budgets, TSR quickly becomes less climate warming than keeping the status quo and rewetting at the original surface. In contrast, based on emission factors, rewetting at the original surface is initially the least climate warming option.<span> </span></p><p>In general, the climatic effect of TSR is likely lowest when removing only as much topsoil as necessary to implement nutrient-poor and acidic conditions thereby ensuring rapid establishment of a <em>Sphagnum</em> carpet and by conserving the removed topsoil as long as possible. Here, the climate warming effect of TSR of ~30 cm in combination with rewetting roughly corresponds to the climate warming of rewetted nutrient-rich temperate peatlands without TSR. Therefore, from a climate perspective, we can recommend a shallow TSR of up to 30 cm for peat bog restoration given that the goal is to re-establish typical bog habitats.</p>

Maximizing avertable doses with a minimum amount of waste for remediation of land areas around typical single family houses after radioactive fallout based on Monte Carlo simulations

The uncontrolled release of long-lived radioactive substances from nuclear accidents can contaminate inhabited land areas. The removal of topsoil is an important method for reducing future radiation exposure but can also generate a large amount of waste that needs safe disposal. To the best of our knowledge, previous studies have determined the optimal depth of topsoil removal but not the size of the area designated for this measure. For this purpose, this study performed Monte Carlo simulations of hypothetical 137Cs surface contamination on various ground areas in a typical northern European suburban area. The goal was to study the size of the areas needed and amount of waste generated to achieve a certain relative and absolute dose reduction. The results showed that removing the topsoil from areas larger than 3000 m2 around the houses in the study neighbourhood results in only marginal reduction in radiation exposure. If, on average, 5 cm of topsoil is removed over 3000 m2, then 150 m3 of waste would be generated. However, in this scenario adjacent properties benefit from each other’s decontamination, leading to a smaller amount of waste for a given reduction in future radiation exposure per inhabitant of these dwellings. Additionally, it was shown that topsoil removal over limited areas has a higher impact on the absolute dose reduction at an observation point inside or outside the houses with higher initial dose.