Diverse fen plant communities enhance carbon-related multifunctionality, but do not mitigate negative effects of drought

International audienc

Snow cover manipulation effects on microbial community structure and soil chemistry in a mountain bog

Background and Aims: Alterations in snow cover driven by climate change may impact ecosystem functioning, including biogeochemistry and soil (microbial) processes. We elucidated the effects of snow cover manipulation (SCM) on above-and belowground processes in a temperate peatland. Methods: In a Swiss mountain-peatland we manipulated snow cover (addition, removal and control), and assessed the effects on Andromeda polifolia root enzyme activity, soil microbial community structure, and leaf tissue and soil biogeochemistry. Results: Reduced snow cover produced warmer soils in our experiment while increased snow cover kept soil temperatures close-to-freezing. SCM had a major influence on the microbial community, and prolonged ‘close-to-freezing' temperatures caused a shift in microbial communities toward fungal dominance. Soil temperature largely explained soil microbial structure, while other descriptors such as root enzyme activity and pore-water chemistry interacted less with the soil microbial communities. Conclusions: We envisage that SCM-driven changes in the microbial community composition could lead to substantial changes in trophic fluxes and associated ecosystem processes. Hence, we need to improve our understanding on the impact of frost and freeze-thaw cycles on the microbial food web and its implications for peatland ecosystem processes in a changing climate; in particular for the fate of the sequestered carbo

Genetic Determinism vs. Phenotypic Plasticity in Protist Morphology

Untangling the relationships between morphology and phylogeny is key to building a reliable taxonomy, but is especially challenging for protists, where the existence of cryptic or pseudocryptic species makes finding relevant discriminant traits difficult. Here we use Hyalosphenia papilio (a testate amoeba) as a model species to investigate the contribution of phylogeny and phenotypic plasticity in its morphology. We study the response of H. papilio morphology (shape and pores number) to environmental variables in (i) a manipulative experiment with controlled conditions (water level), (ii) an observational study of a within-site natural ecological gradient (water level), and (iii) an observational study across 37 European peatlands (climate). We showed that H. papilio morphology is correlated to environmental conditions (climate and water depth) as well as geography, while no relationship between morphology and phylogeny was brought to light. The relative contribution of genetic inheritance and phenotypic plasticity in shaping morphology varies depending on the taxonomic group and the trait under consideration. Thus, our data call for a reassessment of taxonomy based on morphology alone. This clearly calls for a substantial increase in taxonomic research on these globally still under-studied organisms leading to a reassessment of estimates of global microbial eukaryotic diversity.</p

Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands

Soil microbial communities significantly contribute to global fluxes of nutrients and carbon. Their response to climate change, including winter warming, is expected to modify these processes through direct effects on microbial functions through osmotic stress, and changing temperature regimes. Using four European peatlands reflecting different frequencies of frost events, we show that peatland testate amoeba communities diverge among sites with different winter climates, and that this is reflected through contrasting functions. We found that exposure to harder soil frost promoted species β-diversity (species turnover) thus shifting the community composition of testate amoebae. In particular, we found that harder soil frost, and lower water-soluble phenolic compounds, induced functional turnover through the decrease of large species (-68%, > 80 μm) and the increase of small-bodied mixotrophic species (i.e. Archerella flavum; +79%). These results suggest that increased exposure to soil frost could be highly limiting for large species while smaller species are more resistant. Furthermore, we found that β-glucosidase enzymatic activity, in addition to soil temperature, strongly depended (R2 = 0.95, ANOVA) of the functional diversity of testate amoebae. Changing winter conditions can therefore strongly impact peatland decomposition process, though it remains unclear if these changes are carried–over to the growing season

Post-fire peatland recovery by peat moss inoculation depends on water table depth

Peatland restoration is essential to preserve biodiversity and carbon stored in peat soils. Common restoration techniques such as rewetting do not always result in the full recovery of peatland taxonomic and functional properties, threatening the resilience of restored peatlands and their carbon stores. Here, we study the use of peat moss inoculation in stimulating the short-term taxonomic and functional recovery of a wildfire-impacted peatland using mesocosms at high and low water table depth, representing ideal and adverse hydrological conditions respectively. Inoculation in conjunction with high water tables accelerated the recovery of the vascular plant and prokaryote communities. Importantly, Sphagnum—the keystone genus in these peatlands—only established in inoculated mesocosms. Together, this resulted in an increased CO2 uptake by approximately 17 g m−2 day−1 and reduced overall nutrient content in the peat pore water. Synthesis and applications. Our results indicate that inoculation can be used to accelerate the establishment of peatland-specific species. In addition, they suggest the potential to combine peat moss inoculation and hydrological restoration to accelerate the uptake of carbon back into the system post-fire. This offers a basis for future work exploring the long-term use of inoculation to return disturbed peatlands to their pre-degraded state, and a wider application of soil inoculation as a mechanism for functional recovery

Water level and vegetation type control carbon fluxes in a newly-constructed soft-sediment wetland

Wetlands support unique biodiversity and play a key role in carbon cycles, but have dramatically declined in extent worldwide. Restoration is imperative yet often challenging to counteract loss of functions. Nature-based solutions such as the creation of novel ecosystems may be an alternative restoration approach. Targeted restoration strategies that account for the effects of vegetation on greenhouse gas (GHG) fluxes can accelerate the carbon sink function of such systems. We studied the relationships between vegetation, bare soil, and GHG dynamics on Marker Wadden in the Netherlands, a newly-created 700-ha freshwater wetland archipelago created for nature and recreation. We measured CO2 and CH4 fluxes, and soil microbial activity, in three-year-old soils on vegetated, with distinct species, and adjacent bare plots. Our results show that CH4 fluxes positively related to organic matter and interacted between organic matter and water table in bare soils, while CH4 fluxes positively related to plant cover in vegetated plots. Similarly, Reco in bare plots negatively related to water table, but only related positively to plant cover in vegetated plots, without differences between vegetation types. Soil microbial activity was higher in vegetated soils than bare ones, but was unaffected by substrate type. We conclude that GHG exchange of this newly-created wetland is controlled by water table and organic matter on bare soils, but the effect of vegetation is more important yet not species-specific. Our results highlight that the soil and its microbial community are still young and no functional differentiation has taken place yet and warrants longer-term monitoring

Climate change effects on the stability and chemistry of soil organic carbon pools in a subalpine grassland

Mountain soils stock large quantities of carbon as particulate organic matter that may be highly vulnerable to climate change. To explore potential shifts in soil organic matter (SOM) form and stability under climate change (warming and reduced precipitations), we studied the dynamics of SOM pools of a mountain grassland in the Swiss Jura as part of a climate manipulation experiment. The climate manipulation (elevational soil transplantation) was set up in October 2009 and simulated two realistic climate change scenarios. After 4 years of manipulation, we performed SOM physical fractionation to extract SOM fractions corresponding to specific turnover rates, in winter and in summer. Soil organic matter fraction chemistry was studied with ultraviolet, 3D fluorescence, and mid-infrared spectroscopies. The most labile SOM fractions showed high intra-annual dynamics (amounts and chemistry) mediated via the seasonal changes of fresh plant debris inputs and confirming their high contribution to the microbial loop. Our climate change manipulation modified the chemical differences between free and intra-aggregate organic matter, suggesting a modification of soil macro-aggregates dynamics. Interestingly, the 4-year climate manipulation affected directly the SOM dynamics, with a decrease in organic C bulk soil content, resulting from significant C-losses in the mineral-associated SOM fraction (MAOM), the most stable form of SOM. This SOC decrease was associated with a decrease in clay content, above- and belowground plants biomass, soil microbial biomass and activity. The combination of these climate changes effects on the plant–soil system could have led to increase C-losses from the MAOM fraction through clay-SOM washing out and DOC leaching in this subalpine grassland

Wetscapes : Restoring and maintaining peatland landscapes for sustainable futures

Peatlands are among the world's most carbon-dense ecosystems and hotspots of carbon storage. Although peatland drainage causes strong carbon emissions, land subsidence, fires and biodiversity loss, drainage-based agriculture and forestry on peatland is still expanding on a global scale. To maintain and restore their vital carbon sequestration and storage function and to reach the goals of the Paris Agreement, rewetting and restoration of all drained and degraded peatlands is urgently required. However, socio-economic conditions and hydrological constraints hitherto prevent rewetting and restoration on large scale, which calls for rethinking landscape use. We here argue that creating integrated wetscapes (wet peatland landscapes), including nature preserve cores, buffer zones and paludiculture areas (for wet productive land use), will enable sustainable and complementary land-use functions on the landscape level. As such, transforming landscapes into wetscapes presents an inevitable, novel, ecologically and socio-economically sound alternative for drainage-based peatland use

Microclimatological consequences for plant and microbial composition in Sphagnum-dominated peatlands

In three Scandinavian peatlands we studied to what extent plant and microbial community compositions are governed by local-scale microhabitat, with a special interest in the effect of aspect (i.e. exposition of slopes). Despite differences in solar irradiance between the south- and north-facing slopes, maximum temperature was elevated in the south-facing slopes at the most northern site only. Pore-water nutrient concentrations were not affected by aspect, yet dissolved organic carbon concentrations were higher in the south-facing microhabitats. This was likely caused by higher vascular plant biomass. Plant and microbial community composition clearly differed among sites. In all three sites, microhabitat (i.e. prevailing water-table depth) affected the plant and microbial community compositions. Aspect, however, did not affect community composition, even though microclimate significantly differed between the south- and the north-facing aspects at the northernmost site. Our results highlight the complex link between plant community composition, microbial community and environmental conditions, which deserves much more attention than currently in order to fully understand the effects of climate change on peatland ecosystem function.I