Issues Related to Incorporating Northern Peatlands into Global Climate Models

Northern peatlands cover ~3–4 million km2 (~10% of the land north of 45°N) and contain ~200–400 Pg carbon (~10–20% of total global soil carbon), almost entirely as peat (organic soil). Recent developments in global climate models have included incorporation of the terrestrial carbon cycle and representation of several terrestrial ecosystem types and processes in their land surface modules. Peatlands share many general properties with upland, mineral-soil ecosystems, and general ecosystem carbon, water, and energy cycle functions (productivity, decomposition, water infiltration, evapotranspiration, runoff, latent, sensible, and ground heat fluxes). However, northern peatlands also have several unique characteristics that will require some rethinking or revising of land surface algorithms in global climate models. Here we review some of these characteristics, deep organic soils, a significant fraction of bryophyte vegetation, shallow water tables, spatial heterogeneity, anaerobic biogeochemistry, and disturbance regimes, in the context of incorporating them into global climate models. With the incorporation of peatlands, global climate models will be able to simulate the fate of northern peatland carbon under climate change, and estimate the magnitude and strength of any climate system feedbacks associated with the dynamics of this large carbon pool

The impact of a northern peatland on the earth’s radiative budget: sustained methane emission versus sustained carbon sequestration

Northern peatlands sequester carbon and emit methane, and thus have both cooling and warming impacts on the climate system through their influence on atmospheric burdens of CO2 and CH4. These competing impacts are usually compared by the global warming potential (GWP) methodology, which determines the equivalent CO2 annual emission that would have the same integrated radiative forcing impact over a chosen time horizon as the annual CH4 emission. We use a simple model of CH4 and CO2 pools in the atmosphere to extend this analysis to quantify the dynamics, over years to millennia, of the net radiative forcing impact of a peatland that continuously emits CH4 and sequesters C. We find that for observed ratios of CH4 emission to C sequestration (roughly .01-2 mol mol-1), the radiative forcing impact of a northern peatland begins, at peatland formation, as a net warming that peaks after about 50 years, remains a diminishing net warming for the next several hundred to several thousand years, depending on the rate of C sequestration, and thereafter is or will be an ever increasing net cooling impact. We then use the model to evaluate the radiative forcing impact of various changes in CH4 and/or CO2 emissions. In all cases, the impact of a change in CH4 emissions dominates the radiative forcing impact in the first few decades, and then the impact of the change in CO2 emissions slowly exerts its influence

Natural regulatory (CD4+CD25+FOXP+) T cells control the production of pro-inflammatory cytokines during Plasmodium chabaudi adami infection and do not contribute to immune evasion.

Different functions have been attributed to natural regulatory CD4+CD25+FOXP+ (Treg) cells during malaria infection. Herein, we assessed the role for Treg cells during infections with lethal (DS) and non-lethal (DK) Plasmodium chabaudi adami parasites, comparing the levels of parasitemia, inflammation and anaemia. Independent of parasite virulence, the population of splenic Treg cells expanded during infection, and the absolute numbers of activated CD69+ Treg cells were higher in DS-infected mice. In vivo depletion of CD25+ T cells, which eliminated 80% of CD4+FOXP3+CD25+ T cells and 60–70% of CD4+FOXP3+ T cells, significantly decreased the number of CD69+ Treg cells in mice with lethal malaria. As a result, higher parasite burden and morbidity were measured in the latter, whereas the kinetics of infection with non-lethal parasites remained unaffected. In the absence of Treg cells, parasite-specific IFN-γ responses by CD4+ T cells increased significantly, both in mice with lethal and non-lethal infections, whereas IL-2 production was only stimulated in mice with non-lethal malaria. Following the depletion of CD25+ T cells, the production of IL-10 by CD90− cells was also enhanced in infected mice. Interestingly, a potent induction of TNF- and IFN-γ production by CD4+ and CD90− lymphocytes was measured in DS-infected mice, which also suffered severe anaemia earlier than non-depleted infected controls. Taken together, our data suggest that the expansion and activation of natural Treg cells represent a counter-regulatory response to the overwhelming inflammation associated with lethal P.c. adami. This response to infection involves TH1 lymphocytes as well as cells from the innate immune system

The importance of northern peatlands in global carbon systems during the Holocene

We applied an inverse model to simulate global carbon (C) cycle dynamics during the Holocene period using atmospheric carbon dioxide (CO2) concentrations reconstructed from Antarctic ice cores and prescribed C accumulation rates of Northern Peatlands (NP) as inputs. Previous studies indicated that different sources could contribute to the 20 parts per million by volume (ppmv) atmospheric CO2 increase over the past 8000 years. These sources of C include terrestrial release of 40–200 petagram C (PgC, 1 petagram=1015 gram), deep oceanic adjustment to a 500 PgC terrestrial biomass buildup early in this interglacial period, and anthropogenic land-use and land-cover changes of unknown magnitudes. Our study shows that the prescribed peatland C accumulation significantly modifies our previous understanding of Holocene C cycle dynamics. If the buildup of the NP is considered, the terrestrial pool becomes the C sink of about 160–280 PgC over the past 8000 years, and the only C source for the terrestrial and atmospheric C increases is presumably from the deep ocean due to calcium carbonate compensation. Future studies need to be conducted to constrain the basal times and growth rates of the NP C accumulation in the Holocene. These research endeavors are challenging because they need a dynamically-coupled peatland simulator to be constrained with the initiation time and reconstructed C reservoir of the NP. Our results also suggest that the huge reservoir of deep ocean C explains the major variability of the glacial-interglacial C cycle dynamics without considering the anthropogenic C perturbation

Exploring the limits of knowledge on boreal peatland development using a new model: the Holocene Peatland Model

The Holocene Peatland Model (HPM) (Frolking et al. 2009, Frolking et al. in prep.) is a recently developed tool integrating up-to-date knowledge on peatland dynamics that explores peatland development and carbon dynamics on a millennial timescale. HPM combines the water and carbon cycles with net primary production and peat decomposition and takes the multiple feedbacks into account. The model remains simple and few site-specific inputs are needed. HPM simulates the transient development of the peatland and delivers peat age, peat depth, peat composition, carbon accumulation and water table depth for each simulated year. Evaluating the ability of the model to reproduce peatland development can be achieved in several manners. Commonly one could choose to compare simulations results with observations from field data. However, we argue that the overall response of the model does not give much information about the value of the model design. Modelling of peatlands dynamics requires a lot of information regarding the behaviour of a peatland system within its environment (including allogenic changes in climate, hydrological conditions, nutrient availability or autogenic processes such as microtopographical effects). The actual state of knowledge does not cover all processes, interactions or feedbacks and a lot of peatland properties are neither well defined nor measured yet, so that estimates have been needed to build the model. The work presented here aims at analyzing the role of the model parameterization on the simulation results. To do so, a sensitivity analysis is performed with a Monte-Carlo analysis and with help of the GUI-HDMR software (Ziehn and Tomlin, 2009). This method ranks the parameters and combinations of them according to their influence on simulation results. The results will emphasize how the simulation is sensitive to the parameter values. First, the distribution of outputs gives insight into the possible responses of the simulation to HPM’s assemblage of current knowledge. Second, the importance of some parameters on simulation results points out certain gaps in the current understanding of peatland dynamics. Thus, this study helps determine some avenues that should be explored in future in order to improve peatlands dynamics understanding

Open-access management research at a turning point: giving relevance to a stigmatized object

In this short piece, we start by briefly discussing why the model chosen by M@n@gement – free-to-submit, free-to-publish and free-to-read – remains a relevant template, indeed perhaps more relevant today than ever. Despite these assets, our model must compete with other open-access outlets, and contend with negative perceptions, on the part of academics and the general public, of the distance taken by research from its practical impact. We discuss this multidimensional stigma and consider how we, as a community of management researchers, can overcome these challenges to make open-access research sustainable and impactful

Open-access management research at a turning point: giving relevance to a stigmatized object

In this short piece, we start by briefly discussing why the model chosen by M@n@gement – free-to-submit, free-to-publish and free-to-read – remains a relevant template, indeed perhaps more relevant today than ever. Despite these assets, our model must compete with other open-access outlets, and contend with negative perceptions, on the part of academics and the general public, of the distance taken by research from its practical impact. We discuss this multidimensional stigma and consider how we, as a community of management researchers, can overcome these challenges to make open-access research sustainable and impactful

Quantum-limited amplification and parametric instability in the reversed dissipation regime of cavity optomechanics

Cavity optomechanical phenomena, such as cooling, amplification or optomechanically induced transparency, emerge due to a strong imbalance in the dissipation rates of the parametrically coupled electromagnetic and mechanical resonators. Here we analyze the reversed dissipation regime where the mechanical energy relaxation rate exceeds the energy decay rate of the electromagnetic cavity. We demonstrate that this regime allows for mechanically-induced amplification (or cooling) of the electromagnetic mode. Gain, bandwidth, and added noise of this electromagnetic amplifier are derived and compared to amplification in the normal dissipation regime. In addition, we analyze the parametric instability, i.e. optomechanical Brillouin lasing, and contrast it to conventional optomechanical phonon lasing. Finally, we propose an experimental scheme that realizes the reversed dissipation regime using parametric coupling and optomechanical cooling with a second electromagnetic mode enabling quantum-limited amplification. Recent advances in high-Q superconducting microwave resonators make the reversed dissipation regime experimentally realizable.Comment: 5+3 pages, 5 figures, 1 tabl

Methane Flux from Drained Northern Peatlands: Effect of a Persistent Water Table Lowering on Flux

Measurements of CH4 flux from drained and undrained sites in three northern Ontario peatlands (a treed fen, a forested bog, and a treed bog) were made from the beginning of May to the end of October 1991. In the drained portions, the water table had been lowered between 0.1 and 0.5 m, compared to the water table of the undrained portion of the peatlands. The mean seasonal CH4 flux from the undrained portions of three peatlands was small, ranging from 0 to 8 mg m-2d-1, but similar to the CH4 flux from other treed and forested northern peatlands. The mean seasonal CH4 flux from the drained portion of the peatlands was either near zero or slightly negative (i.e., uptake): fluxes ranged from 0.1 to -0.4 mg m-2d-1. Profiles of CH4 in the air-filled pores in the unsaturated zone, and the water-filled pores of the saturated zone of the peat at the undrained sites, showed that all the CH4 produced at depth was consumed within 0.2 m of the water table and that atmospheric CH4 was consumed in the upper 0.15 m of the peatland. On the basis of laboratory incubations of peat slurries to determine CH4 production and consumption potentials, the lowering of the water table eliminated the near-surface zone of CH4 production that existed in the undrained peatland. However, drainage did not alter significantly the potential for CH4 oxidation between the water table and peatland surface but increased the thickness of the layer over which CH4 oxidation could take place. These changes occurred with a drop in the mean summer water table of only 0.1 m (from -0.2 to -0.3 m) suggesting that only a small negative change in soil moisture would be required to significantly reduce CH4 flux from northern peatlands