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Background The Xilingol grassland ecosystem has abundant superficial coal reserves. Opencast coal mining and burning of coal for electricity have caused a series of environmental challenges. Biogenic generation of methane from coal possesses the potential to improve economic and environmental outcomes of clean coal utilization. However, whether the microbes inhabiting the grassland soil have the functional potential to convert coal into biomethane is still unclear. Results Microbial communities in an opencast coal mine and in grassland soil covering and surrounding this mine and their biomethane production potential were investigated by Hiseq sequencing and anaerobic cultivation. The microbial communities in covering soil showed high similarity to those in the surrounding soil, according to the pairwise weighted UniFrac distances matrix. The majority of bacterial communities in coal and soil samples belonged to the phyla Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria. The dominant bacterial genera in grassland soil included Gaiella, Solirubrobacter, Sphingomonas and Streptomyces; whereas, the most abundant genus in coal was Pseudarthrobacter. In soil, hydrogenotrophic Methanobacterium was the dominant methanogen, and this methanogen, along with acetoclastic Methanosarcina and methylotrophic Methanomassiliicoccus, was detected in coal. Network-like Venn diagram showed that an average of 28.7% of microbial communities in the samples belonged to shared genera, indicating that there is considerable microbial overlap between coal and soil samples. Potential degraders and methanogens in the soil efficiently stimulated methane formation from coal samples by the culturing-based approach. The maximum biogenic methane yields from coal degradation by the microbial community cultured from grassland soil reached 22.4 μmol after 28 day. Conclusion The potential microbial coal degraders and methanogenic archaea in grassland soil were highly diverse. Significant amounts of biomethane were generated from coal by the addition of grassland soil microbial communities. The unique species present in grassland soil may contribute to efficient methanogenic coal bioconversion. This discovery not only contributes to a better understanding of global microbial biodiversity in coal mine environments, but also makes a contribution to our knowledge of the synthetic microbiology with regard to effective methanogenic microbial consortia for coal degradation.

Given the rising nitrous oxide (N 2 O) concentration in the atmosphere, it has become increasingly important to identify hot spots and hot moments of N 2 O emissions. With field measurements often failing to capture the spatiotemporal dynamics of N 2 O emissions, estimating them with modeling tools has become an attractive alternative. Therefore, we incorporated several semi-empirical equations to estimate N 2 O emissions with the Soil and Water Assessment Tool from nitrification and denitrification processes in soil. We then used the model to simulate soil moisture and the N 2 O flux from grassland soils subjected to long-term grazing (> 60 years) at different intensities in Alberta, Canada. Sensitivity analysis showed that parameters controlling the N 2 O flux from nitrification were most sensitive. On average, the accuracy of N 2 O emission simulations were found to be satisfactory, as indicated by the selected goodness-of-fit statistics and predictive uncertainty band, while the model simulated the soil moisture with slightly higher accuracy. As expected, emissions were higher from the plots with greater grazing intensity. Scenario analysis showed that the N 2 O emissions with the recommended fertilizer rate would dominate the emissions from the projected wetter and warmer future. The combined effects of fertilization and wetter and warmer climate scenarios would increase the current N 2 O emission levels by more than sixfold, which would be comparable to current emission levels from agricultural soils in similar regions.

Grassland ecosystems cover a large portion of Earths' surface and contain substantial amounts of soil organic carbon. Previous work has established that these soil carbon stocks are sensitive to management and land use changes: grazing, species composition, and mineral nutrient availability can lead to losses or gains of soil carbon. Because of the large annual carbon fluxes into and out of grassland systems, there has been growing interest in how changes in management might shift the net balance of these flows, stemming losses from degrading grasslands or managing systems to increase soil carbon stocks (i.e., carbon sequestration). A synthesis published in 2001 assembled data from hundreds of studies to document soil carbon responses to changes in management. Here we present a new synthesis that has integrated data from the hundreds of studies published after our previous work. These new data largely confirm our earlier conclusions: improved grazing management, fertilization, sowing legumes and improved grass species, irrigation, and conversion from cultivation all tend to lead to increased soil C, at rates ranging from 0.105 to more than 1 Mg C·ha⁻¹yr⁻¹. The new data include assessment of three new management practices: fire, silvopastoralism, and reclamation, although these studies are limited in number. The main area in which the new data are contrary to our previous synthesis is in conversion from native vegetation to grassland, where we find that across the studies the average rate of soil carbon stock change is low and not significant. The data in this synthesis confirm that improving grassland management practices and conversion from cropland to grassland improve soil carbon stocks.

BACKGROUND AND AIMS: Plant-derived phenols are a major input to the terrestrial carbon cycle that might be expected to contribute substantially to dissolved organic carbon (DOC) losses from soils. This study investigated changes in DOC and phenols in leachates from soil treated with individual plant litter types under seasonal temperature change. METHODS: Senescing grass, buttercup, ash and oak litters were applied to soil lysimeters. Leachates were collected over 22 months and analysed for DOC and phenols. Phenols in litter and DOC were analysed using on-line thermally assisted hydrolysis and methylation with tetramethylammonium hydroxide (TMAH). RESULTS: Mass loss differed between litter type (buttercup>ash>grass>oak). Phenol concentrations in the senescing litters (<2 % TOC) were small, resulting in minor losses to water. Seasonal soil temperature positively correlated with DOC loss from litter-free soils. An initial correlation between temperature change and total phenol concentration in grass and ash litter treatment leachates diminished with time. Dissolved phenol variety in all litter-amended soil leachates increased with time. CONCLUSIONS: Plant-derived phenols from senescing litter made a minor contribution to DOC loss from soils. The strength of the relationship between seasonal temperature change and phenol type and abundance in DOC changed with time and was influenced by litter type.

Biodiversity loss has become a global concern as evidence accumulates that it will negatively affect ecosystem services on which society depends. So far, most studies have focused on the ecological consequences of above-ground biodiversity loss; yet a large part of Earth’s biodiversity is literally hidden below ground. Whether reductions of biodiversity in soil communities below ground have consequences for the overall performance of an ecosystem remains unresolved. It is important to investigate this in view of recent observations that soil biodiversity is declining and that soil communities are changing upon land use intensification. We established soil communities differing in composition and diversity and tested their impact on eight ecosystem functions in model grassland communities. We show that soil biodiversity loss and simplification of soil community composition impair multiple ecosystem functions, including plant diversity, decomposition, nutrient retention, and nutrient cycling. The average response of all measured ecosystem functions (ecosystem multifunctionality) exhibited a strong positive linear relationship to indicators of soil biodiversity, suggesting that soil community composition is a key factor in regulating ecosystem functioning. Our results indicate that changes in soil communities and the loss of soil biodiversity threaten ecosystem multifunctionality and sustainability.

We expand the concept of \"old growth\" to encompass the distinct ecologies and conservation values of the world's ancient grass-dominated biomes. Biologically rich grasslands, savannas, and open-canopy woodlands suffer from an image problem among scientists, policy makers, land managers, and the general public, that fosters alarming rates of ecosystem destruction and degradation. These biomes have for too long been misrepresented as the result of deforestation followed by arrested succession. We now know that grassy biomes originated millions of years ago, long before humans began deforesting. We present a consensus view from diverse geographic regions on the ecological characteristics needed to identify old-growth grasslands and to distinguish them from recently formed anthropogenic vegetation. If widely adopted, the old-growth grassland concept has the potential to improve scientific understanding, conservation policies, and ecosystem management.

In this study, the impact of rose chafer ( Cetonia aurata L.) larvae on net and gross methane (CH 4 ) fluxes in soil from an old permanent grassland site (Giessen, Germany) was investigated. Previous studies at this site suggested the existence of Scarabaeidae larvae-induced “CH 4 -emitting hot spots” within the soil profile which may subsequently lead to increased CH 4 oxidation. The net (soil + larvae) and gross (soil and larvae separated) CH 4 fluxes were studied in a 3-month laboratory incubation. Addition of larvae changed the soil from a net sink (−330 ± 11 ng CH 4  kg −1  h −1 ) to a net source (637 ± 205 ng CH 4  kg −1  h −1 ). Supply of plant litter to the soil + larvae incubation jars tended to increase CH 4 emissions which was not significant due to large variability. After 11–13 weeks of incubation, the net soil CH 4 oxidation was significantly stimulated by 13–21% in the treatments containing larvae when these were taken out. Analysis of archaeal 16S rRNA genes revealed that the majority of the obtained clones were closely related to uncultured methanogens from guts of insects and other animals. Other sequences were relative to cultivated species of Methanobrevibacter , Methanoculleus , and Methanosarcina . Hence, Scarabaeidae larvae in soils (i) may represent an underestimated source of CH 4 emissions in aerobic upland soils, (ii) may stimulate gross CH 4 consumption in their direct soil environment, and, thus, (iii) contribute to the spatial heterogeneity often observed in the field with closed-chamber measurements. Long-term CH 4 -flux balances may be wrongly assessed when “exceptional” net CH 4 flux rates (due to larvae hot spots) are excluded from data sets.

The ongoing climate change affects biogeochemical cycling in terrestrial ecosystems, but the magnitude and direction of this impact is yet unclear. To shed further light on the climate change impact, we investigated alterations in the soil nitrogen (N) cycling in a Danish heathland after 5 years of exposure to three climate change factors, i.e. warming, elevated CO₂ (eCO₂) and summer drought, applied both in isolation and in combination. By conducting laboratory ¹⁵N tracing experiments we show that warming increased both gross N mineralization and nitrification rates. In contrast, gross nitrification was decreased by eCO₂, an effect that was more pronounced when eCO₂ was combined with warming and drought. Moreover, there was an interactive effect between the warming and CO₂ treatment, especially for N mineralization: rates increased at warming alone but decreased at warming combined with eCO₂. In the full treatment combination, simulating the predicted climate for the year 2075, gross N transformations were only moderately affected compared to control, suggesting a minor alteration of the N cycle due to climate change. Overall, our study confirms the importance of multifactorial field experiments for a better understanding of N cycling in a changing climate, which is a prerequisite for more reliable model predictions of ecosystems responses to climate change.

Although it is well known that arbuscular mycorrhizal fungi (AMF) play a key role in the functioning of natural ecosystems, the underlying drivers determining the composition of AMF communities remain unclear. In this study, we established 138 sampling plots at 46 grassland sites, consisting of 26 acidic grasslands and 20 calcareous grasslands spread across eight European countries, to assess the relative importance of abiotic and biotic filtering in driving AMF community composition and structure in both the grassland soils and in the roots of 13 grassland plant species. Soil AMF communities differed significantly between acidic and calcareous grasslands. In root AMF communities, most variance was attributable to soil variables while very little variation was explained by host plant identity. Root AMF communities in host plant species occurring in only one grassland type closely resembled the soil AMF communities of that grassland type and the root AMF communities of other host plant species occurring in the same grassland type. The observed AMF–host plants networks were not modular but nested. Our results indicate that abiotic conditions, rather than biotic filtering through host plant specificity, are the most important drivers in shaping AMF communities in European semi-natural grasslands.

Intensive dairy farming systems are a large source of emission of the greenhouse gas nitrous oxide (N₂O), because of high nitrogen (N) application rates to grasslands and silage maize fields. The objective of this study was to compare measured N₂O emissions from two different soils to default N₂O emission factors, and to look at alternative emission factors based on (i) the N uptake in the crop and (ii) the N surplus of the system, i.e., N applied minus N uptake by the crop. Twelve N fertilization regimes were implemented on a sandy soil (typic endoaquoll) and a clay soil (typic endoaquept) in the Netherlands, and N₂O emissions were measured throughout the growing season. Highest cumulative fluxes of 1.92 and 6.81 kg N₂O-N ha⁻¹ for the sandy soil and clay soil were measured at the highest slurry application rate of 250 kg N ha⁻¹. Background emissions from unfertilized soils were 0.14 and 1.52 kg N₂O-N ha⁻¹ for the sandy soil and the clay soil, respectively. Emission factors for the sandy soil averaged 0.08, 0.51 and 0.26% of the N applied via fertilizer, slurry, and combinations of both. For the clay soil, these numbers were 1.18, 1.21 and 1.69%, respectively. Surplus N was linearly related to N₂O emission for both the sandy soil (R² = 0.60) and the clay soil (R² = 0.40), indicating a possible alternative emission factor. We concluded that, in our study, N₂O emission was not linearly related to N application rates, and varied with type and application rate of fertilizer. Finally, the relatively high emission from the clay soil indicates that background emissions might have to be taken into account in N₂O budgets.