Engineering restoration and gaseous carbon uptake on a degraded bog: the role of Eriophorum angustifolium and micropropagated Sphagnum

Degraded peatlands are significant sources of carbon greenhouse gases (CGHG), and their recovery can make significant contributions to climate change mitigation as well as deliver biodiversity benefits. Sphagnum mosses are key species for northern peatland formation and re-introduction is often needed for successful ecohydrological restoration of degraded bogs, but natural sources are scarce and often protected. Micropropagated Sphagnum moss products (BeadaMoss®) were developed to alleviate this constraint. This research explored in detail, for the first time, the CGHG fluxes on a cut-over lowland peatland restoration site where micropropagated Sphagnum was introduced to an existing ‘nurse crop’ of Eriophorum angustifolium, and tested the influence of vegetation maturity. Ecosystem CGHG flux was measured using closed chambers at plot scale in areas of both mature and immature E. angustifolium with and without application of BeadaGel™ Sphagnum, with control plots on bare peat. Studies were conducted over two years of contrasting weather patterns. In Year 1, mean net (CO2e) CGHG uptake on vegetated plots was -2.33 (minimum 1.55, maximum -5.55) t ha-1 yr-1 with increasing CGHG uptake as vegetation matured. In Year 2, gross photosynthesis reduced significantly during the 2018 summer drought resulting in a small mean net CGHG emission of 0.11 (minimum 2.21 maximum -1.22) t ha-1 yr-1 . Sphagnum application within immature vegetation resulted in greater CGHG uptake in both years, but was not as beneficial within mature vegetation. CGHG emission from bare peat (3.79 t ha-1 yr-1 overall) showed the magnitude of avoided losses. Methane flux contributed significantly to CGHG emission but was not closely related to water table depth. Application of Sphagnum within E. angustifolium can deliver good CGHG flux results in the early stages of degraded lowland bog recovery but cannot fully mitigate vulnerability to climate change scenarios

Tree encroachment may lead to functionally-significant changes in peatland testate amoeba communities

Climate change is likely to cause increased tree recruitment on open peatlands but we currently have little idea what consequences this vegetation change may have below-ground. Here we use transects across forested to open bog ecotones at three Russian peatland complexes to assess potential changes in the most abundant group of peatland protists - the testate amoebae. We show that the testate amoeba communities of forested and open bog are markedly different with a very abrupt boundary at, or near, the vegetation ecotone. Changes along our transects suggest that tree encroachment may reduce the trophic level of testate amoeba communities and reduce the contribution of mixotrophic testate amoebae to primary production. Our study strongly suggests that increased tree recruitment on open peatlands will have important consequences for both microbial biodiversity and microbially-mediated ecosystem processes

Ecological and environmental transition across the forested-to-open bog ecotone in a west Siberian peatland

Climate change may cause increasing tree cover in boreal peatlands, and the impacts of this encroachment will be noted first at forested-to-open bog ecotones. We investigate key metrics of ecosystem function in five such ecotones at a peatland complex in Western Siberia. Stratigraphic analysis of three cores from one of these transects shows that the ecotone has been dynamic over time with evidence for recent expansion of forested peatland. We observed that the two alternative states for northern boreal peatlands (forested/open) clearly support distinct plant and microbial communities. These in turn drive and respond to a number of feedback mechanisms. This has led to steep ecological gradients across the ecotones. Tree cover was associated with lower water tables and pH, along with higher bulk density, aquatic carbon concentrations, and electrical conductivity. We propose that the conditions found in the forested peatland of Western Siberia make the carbon sink more vulnerable to warmer and drier conditions

Plant community responses to experimental climate manipulation in a Welsh ombrotrophic peatland and their palaeoenvironmental context

We test whether vegetation community composition from a 10-year climate manipulation experiment on a Welsh peat bog resembles vegetation communities during periods of climate change inferred from a peat core. Experimentally warmed and combined warmed and droughted treatments drove significant increases in ericaceous shrubs but Sphagnum was unaffected. Similarly, Calluna vulgaris seeds increase during inferred warmer periods in the palaeoecological record. Experimental short-term episodic drought (four 4-week drought treatments) did not affect vegetation. Plant community composition has undergone several abrupt changes throughout the past c. 1500 years, often in response to human disturbance. Only slight changes occurred during the Medieval Climate Anomaly (c. 950-1250 CE) in vegetation and hydrology, while abrupt changes occurred during the Little Ice Age (c. 1300-1850 CE) when water tables were highest, suggesting that these shifts were driven by changes in water table, modulated by climate. A period of water table drawdown c. 1800, synchronous with historical records of increased drainage, corresponds with the development of the present-day vegetation community. Modern analogues for fossil material, characterised by abundant Rhyncospora alba and Sphagnum pulchrum, are more common after this event. Vegetation changes due to climate inferred from the palaeo record differ from those observed in the experiments, possibly relating to differences in the importance of drivers of vegetation change over varying timescales. Whereas temperature is frequently identified as the dominant driver of plant community change in experiments, sustained changes in water table appear to be more important in the long-term record. We find evidence that recent climate change and other anthropogenic stressors (e.g., drainage, heavy metal, and nitrogen pollution) may promote the development of novel plant communities without analogues in the fossil record. These communities may be poorer at sequestering carbon and may respond differently to future climate change

Carbon Loss Pathways in Degraded Peatlands: New Insights From Radiocarbon Measurements of Peatland Waters

Peatland carbon stores are under widespread anthropogenic pressure, resulting in degradation and carbon loss. This paper presents DO14C (Dissolved Organic Carbon) dates from waters draining two eroded blanket peatland catchments in the UK. Both catchments are characterized by severe gully erosion but one additionally has extensive surface erosion on unvegetated surfaces. DO14C values ranged from 104.3 to 88.6 percent modern (present to 976 Before Present). The oldest DOC dates came from the catchment characterized by both gully and surface erosion and are among the oldest reported from waters draining temperate peatlands. Together with peat age-depth data from across the peatland landscape, the DO14C ages identify where in the peat profile carbon loss is occurring. Source depths were compared with modeled water table data indicating that in the catchment where gully erosion alone dominated, mean water table was a key control on depth of DOC production. In the system exhibiting both gully erosion and surface erosion, DOC ages were younger than expected from the age of surficial peats and measured water tables. This may indicate either that the old organic matter exposed at the surface by erosion is less labile or that there are modifications of hydrological flow pathways. Our data indicate that eroded peatlands are losing carbon from depth, and that erosion form may be a control on carbon loss. Our approach uses point measurements of DO14C to indicate DOC source depths and has the potential to act as an indicator of peatland function in degraded and restored systems