We used variation partitioning to assess the relative importance of drainage, climate and local vegetation composition for the development of a raised bog. As a case study we selected Teici (Teici) Bog in Latvia (north-east Europe). Explanatory variables together explained 74 % of the variation in peat accumulation and only the residue of 26 % remained unexplained. Our study showed that the local vegetation composition and dominant Sphagnum species significantly influence peat accumulation rates. The results of linear models revealed that, under natural conditions, minor drainage and even strong drainage of the peat is associated with a positive growth balance of the system. However, drainage systems can have a measurable impact on peatland ecosystems situated farther away. Our study demonstrates that the average peat accumulation rate in Teici Bog over the last 150 years was 3.5 mm per year. Although the peat accumulation rate has been affected by drainage over the last half-century, it is still 2.8 mm per year. There was no strong correlation with the historical climate record, suggesting that the bog area has buffered the influence of climate change over the last 150 years.

Stratigraphic records from formerly glaciated regions are critical for detailed study of the timing, onset and dynamics of past ice sheets and the palaeoecology of previous ice-free intervals. We examined three stratigraphic sections from an 18-km stretch of the Albany River, Hudson Bay Lowlands, Canada, located at the geographic center for many Late Pleistocene ice sheets. Till characterization and correlation suggest that at least three glacial advances from shifting ice centers within the Labrador sector of the Laurentide Ice Sheet were preserved in these stratigraphic records. Non-glacial units (fluvial, organic-bearing sediments) were constrained via optically stimulated luminescence to two possible periods at ca. 73,000 to 68,000 yr BP and ca. 60,000 yr BP. Boreal and peatland taxa (Picea, Pinus, Poaceae, Betula, Cyperaceae, Sphagnum) dominated the pollen record at each site, whereas plant macrofossils analyzed at one site confirm the local presence of conifer trees (bark, needles, seed wings), bryophytes (largely Scotpidium spp), herbaceous plants (Caryophyllaceae, Carex, Poaceae), and an aquatic setting (e.g. Potamogeton, ephippia of Daphnia spp). Pollen-derived average summer temperature reconstructions suggested that local temperatures at the Albany sites were between 12 and 15 degrees C, which is similar to present-day estimates for the region (14.2 degrees C). Reconstructed annual precipitation estimates were 580-640 mm, which is similar to slightly higher than present-day estimates (564 mm). Non-glacial intervals at the Albany sites likely represent abandoned fluvial environments that supported water-logged peatland biota. Results from this research contribute toward ongoing efforts to constrain ice sheet dynamics over North America during the last glacial cycle (e.g. 71,000-14,000 yr BP) and provide insight into the complex Late Pleistocene palaeoclimate record at the innermost area of the glaciated region.

Northern peatlands, which are highly heterogeneous ecosystems, are a globally important carbon (C) store. Understanding the drivers and predicting the future trajectory of the peatland C store requires upscaling from cores and sites to regions and continents, alongside a detailed understanding of the mechanisms governing their C sequestration. Studies incorporating replication are therefore important to quantify how peatland heterogeneity may affect upscaling from local-scale dynamics to models. In addition, we need to better understand the processes driving observed variability, but the interplay between plants, microbes and C cycling in peatlands remains poorly understood. One approach to address both issues is to examine replicated microbiological functional traits within a multi-proxy framework to provide an ecosystem-level perspective on ecological and biogeochemical processes. Peatland testate amoebae are a functionally important group of protists that are well suited to such an approach. Analysing testate amoeba functional traits provides an opportunity to examine processes that may affect key peatland ecosystem services, such as C sequestration. Here, we compared four key testate amoeba functional traits (mixotrophy, biovolume, aperture size and aperture position) to C accumulation, hydrological and vegetation changes in 12 post-Little Ice Age peat records. Samples were collected from high-boreal and low-subarctic regions in northwestern Quebec, Canada in an experimental design that includes internal and external replication at both site and regional scales. Our results showed that correspondence between C accumulation, hydrology and testate amoeba functional traits varied, but recent changes in mixotrophy and aperture size, which may affect peatland C sequestration potential and microbial food web structure, respectively, showed tentative links to recent C accumulation increases. Vegetation, especiallySphagnumabundance was important in promoting mixotrophy and small aperture size in testate amoeba communities. Future impacts of climate change on peatland vegetation will further influence the functional role of testate amoebae on C sequestration through changing mixotrophic testate amoeba abundance.

Peat soils drained for agriculture and forestry are important sources of carbon dioxide and nitrous oxide. Rewetting effectively reduces these emissions. However, rewetting also increases methane emissions from the soil and, on forestry-drained peatlands, decreases the carbon storage of trees. To analyze the effect of peatland rewetting on the climate, we built radiative forcing scenarios for tropical peat soils, temperate and boreal agricultural peat soils, and temperate and boreal forestry-drained peat soils. The effect of tree and wood product carbon storage in boreal forestry-drained peatlands was also estimated as a case study for Finland. Rewetting of tropical peat soils resulted in immediate cooling. In temperate and boreal agricultural peat soils, the warming effect of methane emissions offsets a major part of the cooling for the first decades after rewetting. In temperate and boreal forestry-drained peat soils, the effect of rewetting was mostly warming for the first decades. In addition, the decrease in tree and wood product carbon storage further delayed the onset of the cooling effect for decades. Global rewetting resulted in increasing climate cooling, reaching -70 mW (m(2)Earth)(-1)in 100 years. Tropical peat soils (9.6 million ha) accounted for approximately two thirds and temperate and boreal agricultural peat soils (13.0 million ha) for one third of the cooling. Forestry-drained peat soils (10.6 million ha) had a negligible effect. We conclude that peatland rewetting is beneficial and important for mitigating climate change, but abandoning tree stands may instead be the best option concerning forestry-drained peatlands.

Fossil testate amoeba assemblages have been used to reconstruct peatland palaeohydrology for more than two decades. While transfer function training sets are typically of local-to regional-scale in extent, combining those data to cover broad ecohydrological gradients, from the regional-to continental- and hemispheric-scales, is useful to assess if ecological optima of species vary geographically and therefore may have also varied over time. Continental-scale transfer functions can also maximise modern analogue quality without losing reconstructive skill, providing the opportunity to contextualise understanding of purely statistical outputs with greater insight into the biogeography of organisms. Here, we compiled, at moderate taxonomic resolution, a dataset of nearly 2000 modern surface peatland testate amoeba samples from 137 peatlands throughout North America. We developed transfer functions using four model types, tested them statistically and applied them to independent palaeoenvironmental data. By subdividing the dataset into eco-regions, we examined biogeographical patterns of hydrological optima and species distribution across North America. We combined our new dataset with data from Europe to create a combined transfer function. The performance of our North-American transfer function was equivalent to published models and reconstructions were comparable to those developed using regional training sets. The new model can therefore be used as an effective tool to reconstruct peatland palaeohydrology throughout the North American continent. Some eco-regions exhibited lower taxonomic diversity and some key indicator taxa had restricted ranges. However, these patterns occurred against a background of general cosmopolitanism, at the moderate taxonomic resolution used. Likely biogeographical patterns at higher taxonomic resolution therefore do not affect transfer function performance. Output from the combined North American and European model suggested that any geographical limit of scale beyond which further compilation of peatland testate amoeba data would not be valid has not yet been reached, therefore advocating the potential for a Holarctic synthesis of peatland testate amoeba data. Extending data synthesis to the tropics and the Southern Hemisphere would be more challenging due to higher regional endemism in those areas. (C) 2018 The Authors. Published by Elsevier Ltd.