10 Peatlands: Canada’s Past and Future Carbon Legacy D.H Vitt CONTENTS 10.1 Introduction 201 10.2 Limitations on Carbon Sequestration in Boreal Peatlands 203 10.3 The Ecology of Boreal Peat Accumulation .204 10.3.1 Bog Accumulation 205 10.3.2 Poor Fen Accumulation 205 10.3.3 Rich Fen Accumulation 205 10.4 Northern Peatlands: Sinks or Sources of Carbon? 206 10.5 Potential Climatic Effects on Peatland Form and Vegetation .207 10.6 Permafrost Melting in the Boreal Forest 209 10.7 Global Climate Change vs Cumulative Disturbance 210 10.8 Mitigation .211 Acknowledgments 213 References 213 10.1 INTRODUCTION Peatland ecosystems are characterized by the accumulation of organic matter in soil and, if following Joosten and Clark’s1 definition of having at least 30 cm of peat with a minimum organic content of 30%, then peatlands cover over million km2 — about 3% of the Earth’s land surface Nearly 70% of this peatland area lies in the boreal regions of Canada and Russia Canada alone contains just over 1,200,000 km2 of peat Peatlands are significant in that they provide a wide diversity of ecosystem services, not the least of which is the accumulation of large stores of carbon Joosten and Clark1 estimated that since 1800, 10 to 20% of the world’s peatlands have been lost, but it has been the view of many that Canada’s peatlands remain in pristine condition, undisturbed by human activities.2 However, as we will see, this is certainly not the case Globally, wetlands (especially peatlands) represent a large carbon stock, with estimates varying from 200 to 860 Pg (= Petagrams) of carbon (see for example 201 © 2006 by Taylor & Francis Group, LLC 202 Climate Change and Managed Ecosystems Gorham,2 Bohn,3,4 Sjörs,5 Post et al.,6 Houghton et al.,7 Armentano and Menges,8 and Markov et al.9) Generally, carbon-rich peatland soils are thought to represent about one third of the world’s soil carbon, yet cover only about 3% of the land surface Release of this store of carbon into the atmosphere would increase atmospheric CO2 concentrations by more than 50% Canada’s peat inventory has been estimated to contain up to 170 Pg of carbon2 and is approximately 38% of the carbon stock in northern peatlands The western boreal forest region of Alberta, Saskatchewan, and Manitoba contain 365,157 km2 of peatlands and along with British Columbia these four provinces have about 40% of Canada’s peatland area, while eastern Canada (Ontario eastward) contains about 37%, and northern Canada (the three territories) contains approximately 23%.10 In terms of carbon, western and northern Canada store at least 83 Pg, whereas eastern Canada has a minimum of 52 Pg In Alberta, peatlands may contain as much as 70% of the province’s soil carbon (13.5 Pg C in peatlands; 2.3 Pg C in lakes, 2.7 Pg C in forests, and 0.8 Pg C in grasslands (data from J Bhatti11) In general, the western Canadian peatlands have sequestered about 48 Pg of carbon during the past 10,000 years, with about half of this accumulated in the last 4000 years.12 Peat accumulates on the landscape when annual net primary production exceeds the sum of annual decomposition and the loss of carbon that is dissolved in the pore water and exported from peatlands The initiation, development, and succession of ecosystems that sequester carbon, as well as the rate of peat accumulation in boreal peatlands, are dependent on regional allogenic factors such as climate, substrate chemistry, and landscape and hydrological position These regional driving factors in turn determine a suite of local factors that influence the form and function of individual peatland sites (Figure 10.1) These local factors include water chemistry, Regional Position Climate Substrate Local Water Flow Autogenic Processes Nutrients Function Production Decomposition Carbon Sequestration Water Chemistry Water Level Fluctuation Form Vegetation and Flora Succession Bog Development Pattern Development Landform Development Disturbance FIGURE 10.1 Diagrammatic representation of the interactions between regional, local, and ecological factors that control function and form of peatlands © 2006 by Taylor & Francis Group, LLC Peatlands: Canada’s Past and Future Carbon Legacy 203 water level fluctuation, water flow rates, and nutrient inputs Peatland form is determined by this interacting suite of local and regional factors through the development of ombrotrophy wherein the peatland receives all water and nutrients from the atmosphere, evolution of internal landforms and landscape pattern, and the direction of succession Additionally, once established, peatlands have strong autogenic controls (acidification, eutrophication; Vitt13) that also help regulate form and function.14 The functioning of peatland ecosystems centers on the process of peat accumulation Yu et al.15 provided conceptual diagrams of carbon cycling in peatlands Peat accumulation is dependent on the rate of input of organic matter into the anaerobic peat column (the catotelm) and on the rate of the slow decomposition of this material over time.16 Climate is the most important regional factor, mainly through its regulation of local water regimes Among climatic variables, Halsey et al.17 demonstrated for wetlands of Manitoba that temperature and aridity are the most critical limiting factors at the landscape scale for peatland ecosystems Climate affects carbon sequestration by limiting photosynthesis and aerobic (acrotelm) decomposition rates, thus influencing the amount and quality of the organic material reaching the catotelm Climate also affects carbon stocks within the catotelm by limiting anaerobic processes (methenogenesis, sulfate reduction, and N2O production), as well as controlling the position of the acrotelm–catotelm boundary Thus, climatic change can affect current peat accumulation as well as persistence of the peat column itself 10.2 LIMITATIONS ON CARBON SEQUESTRATION IN BOREAL PEATLANDS Four factors contribute to limiting carbon sequestration in pristine boreal peatlands: (1) The formation of permafrost in boreal peatlands reduces the input of carbon to the peatland (2) Ground layer biomass contributes high-quality organic matter that is resistant to decay to the peat column and, along with vascular plant roots and litter from aboveground vascular plant biomass, compose the carbon inputs to peat-forming ecosystems These inputs are limited by net annual primary production (NPP) (3) Rates of aerobic respiration (occurring in the acrotelm) limit peat accumulation Rates of aerobic decomposition may be determined by substrate quality and by temperature (4) The amount of time the decomposing plant material spends in aerobic conditions In summary, cold, dry climatic conditions favor permafrost aggradation; warm, dry (arid) conditions limit ground-layer NPP and increase acrotelm depth, while warm, wet conditions increase microbial respiration Peat accumulation decreases with aridity and increases under cool, moist conditions (Figure 10.2) Corollaries to these relationships provide us with four mechanistic statements: Increases in precipitation increase the ground layer production, and these, coupled with a rise in water table, decrease residence time in the acrotelm lowering initial catotelmic bulk densities: Carbon sequestration increases Decreases in precipitation decrease ground layer production and are coupled to a lowering of the water table These factors increase the residence © 2006 by Taylor & Francis Group, LLC 204 Climate Change and Managed Ecosystems Temperature Cold Permafrost Aggradation Cool Decreased Ground layer NPP A B Acrotelm Depth Increase Warm Dry Moist Wet Precipitation FIGURE 10.2 Factors limiting carbon sequestration in boreal peatlands plotted over climatic space represented by temperature (inverse on y axis) and precipitation (x axis) Shading of central ellipse indicates increased rates of carbon accumulation A = Direction of increase in ground-layer NPP B = Direction of bulk density decrease White circle = Estimated peat accumulation during Holocene wet period.43 Black circle = Estimated peat accumulation during Holocene dry period.43 Details of long-term peatland dynamics are available in Yu et al.15,50 Dotted line is degrading permafrost time in the acrotelm, thus increasing the initial catotelmic bulk densities: Carbon sequestration decreases Increases in temperatures increase acrotelmic respiration, hence increasing initial catotelmic bulk densities: Carbon sequestration decreases Decreases in temperatures decrease acrotelmic respiration, hence decreasing initial catotelmic bulk densities: Carbon sequestration increases 10.3 THE ECOLOGY OF BOREAL PEAT ACCUMULATION Accumulation of peat in the boreal region appears to occur under three somewhat different ecological regimes © 2006 by Taylor & Francis Group, LLC Peatlands: Canada’s Past and Future Carbon Legacy 205 10.3.1 BOG ACCUMULATION Bogs are ombrogenous, receiving their nutrients and water supply solely from the atmosphere as precipitation Bogs that occur in the boreal region are generally treed and possess a continuous ground layer of Sphagnum (peat mosses) These peat mosses develop an extensive, undulating microrelief of hummocks and hollows Hummocks attain heights of nearly m above the water surface Thus the aerobic zone of decomposing peat (the acrotelm) is well developed and organic matter spends a relatively large amount of time in this zone; however, rates of decomposition are reduced here largely due to factors inherent in the Sphagnum species themselves.18–20 Furthermore, catotelmic bulk densities are relatively low due to the fibrous nature of the hummock-occurring Sphagnum species and low number of graminoid roots 10.3.2 POOR FEN ACCUMULATION Fens are geogenous, receiving waters and nutrients that have been in contact with the surrounding uplands as well as from precipitation Poor fens have ground layers dominated by species of Sphagnum and are acidic ecosystems The Sphagnum species of poor fens occur in carpets and lawns forming extensive flat areas relatively close to the water’s surface Thus, the acrotelm is poorly developed and the residence time of organic material in the aerobic zone is low, with the organic matter reaching the catotelm rather quickly Catotelmic bulk densities are higher than in bogs, but due to the fibrous nature of Sphagnum and the low root biomass, are less than those of the rich fens 10.3.3 RICH FEN ACCUMULATION Geogenous rich fens have ground layers dominated by true mosses (generally referred to as “brown mosses”) These plants, like the sphagna of poor fens, form lawns and carpets, water tables are high, and acrotelms are poorly developed Ground-layer canopies of rich fens differ from those of poor fens and bogs by the difference between true moss and peat moss plant architectures The rich fen acrotelm has denser canopies because it is dominated by true mosses As a result of the high water table in rich fens, this relatively dense (carbon-rich) ground layer spends little time in the acrotelm, and reaches the catotelm as high-quality peat with high bulk densities Additionally, rich fens have higher abundances of graminoids, and sedge roots also contribute to the high bulk densities All three peatland types effectively sequester carbon, each in a somewhat different manner Fundamental differences in vegetation, hydrology, and chemistry between these three peatland types13,21 lead to three generalizations about how climate change can affect the ecology of these peatland systems Bogs require a local positive climatic water balance The large Sphagnum hummocks and well-developed acrotelms must be maintained through precipitation input Nutrient supplies for these ombrogenous peatlands are dependent on atmospheric influxes © 2006 by Taylor & Francis Group, LLC 206 Climate Change and Managed Ecosystems Fens require a constant groundwater source, and the acrotelm–catotelm boundary (so critical for peat accumulation in fens) must be maintained at a relatively stable elevation Lowering of water tables or changes in annual water table fluctuations alter the boundary conditions Changes in upland and surrounding nutrient fluxes strongly affect fens, whereas changes in atmospheric nutrient inputs strongly affect bogs In conclusion, peat accumulation and the sequestration of carbon from the atmosphere (as CO2) to solid organic matter (as CHO) is determined and controlled by a series of interacting processes I argue that four of these processes are of most importance (Figure 10.2) and that all of these are climatically controlled Two are more affected by temperature, while the other two are more affected by precipitation How these four factors interrelate and how they are individually affected by climate change is still poorly understood and needs to be a priority research goal 10.4 NORTHERN PEATLANDS: SINKS OR SOURCES OF CARBON? Although I believe that it is generally acknowledged that northern peatlands are a present-day sink for atmospheric CO2,2 several complicating factors exist that may severely limit their role in maintaining this large carbon sink Local temporal and spatial variation in carbon sequestration is high Annual changes from net carbon sinks to net carbon sources have been demonstrated for an oligotrophic pine fen in Finland by Alm et al.,22 a Minnesota peatland by Shurpali et al.,23 a Manitoba rich fen by Suyker et al.24 and Lafleur et al.,25 and a temperate poor fen by Carroll and Crill.26 Likewise, spatially local microhabitats may be either net sinks or sources.27 The concept of the Canadian peatlands and the boreal forest being of a pristine nature is doubtful Long-term carbon accumulation rates have been estimated at between 19.4 g m2 yr–1 for western Canada12 and 28.1 g m2 yr–1 for northern peatlands in general.2 These rates, however, are based on apparent long-term accumulation in pristine peatlands (and as well may not be representative of current net rates), and not take into consideration peat lost from the direct and indirect effects of fire and other natural disturbances If peat losses due to the effects of the historical fire regime are added back into the 19.4 g m2 yr–1 estimates of peat accumulation the actual rate of peat accumulation is 24.5.28 In the only cumulative effects study of which I am aware, Turetsky et al.28 estimated that 13% of western Canada’s peatlands are disturbed She estimated that of the 8940 Gg C yr–1 of carbon that should be sequestered annually under a no-disturbance regime, 48 Gg C yr–1 are lost to oil sands mining, 80 Gg C yr–1 to flooding from hydro-electric projects, 135 Gg C yr–1 to peat extraction activities, 4704 Gg C yr–1 from the direct effects of fire (carbon released from the fire itself), and 1578 Gg C yr–1 are lost to the indirect effects of fire (due to decreased sequestration of carbon from vegetation recovery, plus decomposition during recovery) On the positive side, © 2006 by Taylor & Francis Group, LLC Peatlands: Canada’s Past and Future Carbon Legacy 207 melting of boreal permafrost yields a return of +100 Gg C yr–1 (see Turetsky et al.29 for explanation) and undisturbed peatlands sequester 7781 Gg yr–1 of carbon Overall, disturbance and development across western Canada has reduced the annual carbon sequestration to +1319 Gg C yr–1 — only 14% of the long-term carbon sink rate Increases in any of the anthropogenic disturbances or in the future fire regime, or a decrease of only 17% in the carbon sequestered in undisturbed peatlands because of drought and or temperature increases, will move western Canadian peatlands from a sink to a source of CO2 Additionally, peatland types differ in the forms of gaseous carbon release and have different global warming potentials Anaerobic respiration releases include methane (among other gases) Methane is a greenhouse gas with different absorptive properties and different atmospheric lifetimes from those of CO2 Boreal wetlands release an estimated 34 Tg of CH4 annually.30,31 Joosten and Clark1 provided global warming potentials (GWP) for northern pristine bogs and fens that were calculated for different time horizons into the future Their data indicate that currently pristine fens remove 250 kg C ha–1 yr–1 (as CO2) and release 297 kg C ha–1 yr–1 (as CH4), while bogs currently remove 310 kg C ha–1 yr–1 and release 53 kg C ha–1 yr–1 So, even though a carbon sink is indicated by 560 kg C ha–1 yr–1 being sequestered and only 350 kg C ha–1 yr–1 released, differences in atmospheric properties of CO2 and CH4 produce a positive GWP when calculated per hectare for bogs and fens over the next 20- and 100-year intervals, but a negative GWP at 500 years due to different atmospheric residence times of the gases involved 10.5 POTENTIAL CLIMATIC EFFECTS ON PEATLAND FORM AND VEGETATION Gignac et al.32 established response surfaces for a number of the indicator and keystone species of western Canadian peatlands for climate (using an aridity index), pH, and height above the water surface table Of the 31 indicator species that were examined, all but are climatically limited in western Canada Using these response surfaces, Gignac and Vitt33 developed peatland indicator bryophyte communities and constructed two peatland communities for contemporary climate; one at Athabasca, Alberta and one at Wandering River, Alberta These communities encompassed a range of peatland types from bogs to rich fens Then, by using the Canadian CCC General Circulation model × CO2 scenario that predicted an increase of 4°C for these southern boreal sites, an increase in the growing season of 19 days, and no increase in precipitation, two future climate peatland bryophyte communities were constructed The resulting indicator communities for these two locations show the complete absence of all peatland species at Athabasca and a reduction of cover at Wandering River from 14 species with 77% cover to species with less than 1% cover Essentially, peatland communities would cease to exist at both of these southern boreal locations Nicholson and Gignac34 and Nicholson et al.35,36 examined the current and future occurrences of fens and bogs in the Mackenzie River Basin They constructed threedimensional response surfaces for 21 indicator species spanning the rich fen, poor © 2006 by Taylor & Francis Group, LLC 208 Climate Change and Managed Ecosystems FIGURE 10.3 Geographical locations of extant peatlands (left) and projected distributions (right) by peatland type of sites in the Mackenzie River Basin as a result of global warming Climatic data that were used by the model to generate the projected distribution of peatlands were obtained from the Geophysics Fluid Dynamics Laboratory (GFDL) Model for × present CO2 concentrations (From Nicholson, B.J et al., in Mackenzie Basin Impact Study (MBIS), Final Report, Cohen, S.J., Ed., Environment Canada, Downsview, Ontario, 1997, 295 With permission.) fen, boreal bog, and peat plateau (ombrotrophic sites with extensive permafrost) gradient Under × CO2 climatic scenarios (using both the GFDL and CCC General Circulation Models), peatland ecosystems of all types were displaced northward approximately 780 km (Figure 10.3) The southern limit of peat-forming ecosystems was predicted to be at about 60° N latitude Bryophyte species are especially sensitive indicators of water level changes, and Nicholson et al.36 utilized these sensitivities to predict projected changes in depth to the water table relative to the peat surface Predictions of changes ranged from –7 dm in northeastern Alberta, to –5 dm in north central Alberta, decreasing to a –3 to –1 dm change north of 60˚ N latitude (Figure 10.4) The use of plant indicators to predict water table position is a site-specific modeled response that has much more ecosystem relevance than predictions made from landscape-scale hydrology Present-day vegetation response for drawdown is clearly evident in fens of the Athabasca area, which is situated north of central Alberta Furthermore, the latitudinal position of the parkland–boreal forest boundary may react to increasing temperature through a parallel northward migration © 2006 by Taylor & Francis Group, LLC Peatlands: Canada’s Past and Future Carbon Legacy 209 FIGURE 10.4 Projected minimum mean changes in depth of water table relative to peat surface (dm) for peatlands in the Mackenzie Basin based on climatic data obtained from the Canadian Climate Centre (CCC) Model for × and × present CO2 concentrations (From Nicholson, B.J et al., in Mackenzie Basin Impact Study (MBIS), Final Report, Cohen, S.J., Ed., Environment Canada, Downsview, Ontario, 1997, 295 With permission.) 10.6 PERMAFROST MELTING IN THE BOREAL FOREST In 1994, Vitt et al.37 described a series of landforms associated with permafrost features (frost mounds) found in boreal peatlands When these frost mounds melt, they collapse and form melt features termed internal lawns Boreal permafrost melt is in disequilibrium with present-day climate,38 owing to the insulative features of peat and of living Sphagnum, as well as the local microclimatic variation due to tree and shrub cover Over the last millennium, permafrost distribution in the boreal forest has fluctuated in a sensitive zone that is 672,000 km2 in extent across western continental Canada During the Little Ice Age, about 28,800 km2 of permafrost were present.39 With the climate warming over the past 100 to 150 years, 9% (or 2627 km2) of this permafrost has degraded Additionally, 22% (5813 km2) is currently in disequilibrium and actively degrading Only 69% of boreal permafrost exists today in an equilibrium undegraded state Collapse of a frost mound is followed by extremely rapid recolonization of the resulting internal lawn by sedges and species of Sphagnum that form wet carpets and lawns.37,40,41 Over the subsequent 100 to 200 years, vegetation of the internal © 2006 by Taylor & Francis Group, LLC 210 Climate Change and Managed Ecosystems lawn gradually increases in height and the system regenerates to the hummocky microrelief of a continental bog For at least the first 100 years, carbon sequestration in internal lawns is greater than that of both nonpermafrost boreal bogs and permafrost mounds,29 and the melting of permafrost results in an increase in the storage of organic matter Turetsky et al.29 reported organic matter accumulation in internal lawns (formed when permafrost melts) are 1.6 times higher than the close-by frost mounds and boreal bogs Organic matter accumulation in boreal western Canada (where at least 90% of the permafrost has melted) has increased by 5% (or × 10–11 g yr–1) when compared to Little Ice Age amounts.12 10.7 GLOBAL CLIMATE CHANGE VS CUMULATIVE DISTURBANCE Across the boreal and subarctic regions of the world large amounts of carbon are sequestered in different places in our natural ecosystems Carbon can be sequestered in lakes and buried in lake sediments where it is effectively permanently removed from the global carbon cycle In Alberta, Campbell et al.42 estimated that about 2.3 Pg of carbon are stored in this long-term sink Forests and croplands, on the other hand, sequester new carbon that is released and recirculated to the atmosphere within a short-term time range of decades to a few hundred years and have current soil carbon stocks estimated at 3.5 Pg C.11 These two ecosystem types have carbon stored largely in living biomass and in the uppermost relatively shallow soil profile These systems are generally intensively managed with harvest and planting cycles planned and implemented following tight management schedules Northern peatlands contain one third of the world’s soil carbon In Alberta, they contain about 13.5 Pg of carbon, while in continental western Canada they store 48 Pg of carbon of which only 0.1 Pg is found in living vascular plant aboveground biomass.12 Of this large carbon stock, 50% was developed in the last 4000 years Vitt et al.12 estimated that in the last 1000 years, the western Canadian carbon store increased by 7.1 Pg or 14.8% Both rates of peat accumulation and peatland initiation apparently are highly sensitive to natural Holocene climatic changes In western Canada, carbon sequestration has been highly sensitive to millennial wet climate cycles.43,44 These periods of increased moisture, rapid organic matter accumulation, and increased peatland initiation in western Canada appear to be related to warm periods in the North Atlantic,45 as well as to global atmospheric CO2 concentrations in the past.43 Peat accumulation rates at one rich fen in western Alberta varied from means of about 183 g m2 yr–1 during wet periods to a low of g m2 yr–1 during dry periods (with the long-term time-weighted mean of 31.3).43 These data suggest that even minor climatic fluctuations in the past have had strong affects on peatland function and they may alter the rates of peat accumulation considerably Furthermore, northern peatlands appear to be strongly coupled to natural global climatic changes From these data it is apparent that boreal peatlands have been strongly affected by climate change in the past; however, it is also important to realize that the cumulative effects of disturbance may actually have more of an impact on these © 2006 by Taylor & Francis Group, LLC Peatlands: Canada’s Past and Future Carbon Legacy 211 carbon-rich ecosystems Given current disturbance in the western boreal forest,28 reduction in carbon sequestration rates by only 17% will convert these northern peatlands to a net CO2 source to the atmosphere This reduction in carbon sequestration is closer to reality then one might expect Currently, it appears that much of the area in boreal western Canada is too dry for new peatland initiation, and current peatlands are largely relicts of a once wetter (and perhaps cooler) climatic regime.46,47 Increased atmospheric CO2 concentrations are predicted to increase temperatures and perhaps decrease precipitation, or at least increase drought across the boreal zone, where peatlands are abundant This global climate change will potentially reduce carbon sequestration through a series of progressively more severe mechanisms • • • • • • • • Net primary production of the ground layer will decrease, thus new high quality (= highly recalcitrant) carbon input to the ecosystem will be reduced Belowground net primary production (vascular plant roots) will increase in some peatland types, thus new low-quality (= easily decomposed) carbon input to the ecosystem will be increased and may increase methane production Rates of microbial respiration will be increased; thus existing carbon will be released to the atmosphere at an increased rate This assumes that decreased moisture availability in the acrotelm will not be so severe as to decrease microbial respiration Initially, acrotelms will increase in depth; thus the residence time of young peat in an aerobic atmosphere will increase the amount of CO2 released to the atmosphere, but will also serve to oxidize the methane produced in the catotelm With lowered water tables, hummock-growing plant species will die in place and recolonize the previous hollow/lawn — the result will be enhanced decomposition (and loss of) the uppermost peat column until equilibrium with the new water table is established Continued aridity will limit keystone bog species Peatlands will only continue to serve as a carbon sink in discharge sites served with stable groundwater flows; however, these peatlands will be at risk or reduced due to increased decomposition It remains unclear whether new peatland initiation and development north of 60˚ N latitude will be as extensive as the loss of peatlands to the south and whether the peatland carbon stock will remain intact Altered disturbance regimes, especially increases in fire frequency, may lead to catastrophic carbon losses from peatlands, especially bogs 10.8 MITIGATION It is my opinion that even under current climate conditions of the western Canadian boreal region, most boreal Canadian peatlands may not be able to continue to sequester carbon What their ultimate fate will be is currently unknown and should © 2006 by Taylor & Francis Group, LLC 212 Climate Change and Managed Ecosystems be a high research priority The worst-case scenario is clearly shown in predictions by Nicholson et al.35,36 The best-case scenario may be a “resetting” of the peat surface at some distance below the present surface, with recolonization and continued carbon sequestration What is not known is how much, and in what gaseous form, the uppermost peat column will be lost Clearly, mitigation for these loosely managed boreal peatlands is difficult However, several priorities are suggested here: • • • • Develop a long-range plan of corridors and reserves that includes predicted future occurrences of peatlands Since our future peatlands may only exist in a fully functional condition north of 60˚ N latitude, we should begin now to incorporate a reserve system that examines these northern sites Restoration of wetlands after oil sands extraction may only be possible by examining wetlands that currently exist under our future predicted climatic regime Examination of how these wetlands have initiated and continue to exist may provide valuable insights into our wetland environments For example, a key indicator species of rich fens is Meesia triquetra Examination of herbarium specimens and distribution maps48 of the occurrence of M triquetra in southern Saskatchewan and the midwestern states may be useful in developing landscapes for rich fen development under future climatic regimes Maintain our peatlands in as pristine condition as possible Use of peatlands for agriculture increases GWP (global warming potential) of fens and bogs substantially Whereas the GWP of pristine bogs is negative and of fens is only slightly positive (less than 100 kg CO2-C equiv ha–1 yr–1), when peatlands are drained for pasture or tilled the GWP increases to 4000 to 5000 kg CO2-C equiv ha–1 yr–1 for the former and more than 10,000 for the latter for fens.49 Disturbance in peatlands has two effects: direct effects of the disturbance itself (peat removal by the peat harvesting industry, clearing areas for oil exploration vehicles) and indirect effects (the effect of returning to the pre-disturbance condition) Mitigation for indirect effects can be as follows: Do not remove the actively growing top few centimeters of the ground layer when grading access lines Keep the time from the end of peat harvesting activity to revegetation as short as possible In western Canada, develop a clear management plan for restoration of cut over bogs back to fens Avoid nutrient inputs to peatlands during construction activities; these include keeping to a minimum the introduction of mineral soil to peatland areas Adequate buffer zones should be maintained around peatland complexes Higher water tables from increased upland runoff after forest harvest or wildfire increase nutrients and decrease acrotelms resulting in complete © 2006 by Taylor & Francis Group, LLC Peatlands: Canada’s Past and Future Carbon Legacy 213 successional turnover of keystone species and this may be as devastating for peatlands as lowered water tables due to climate change Buffer zones should be designed relative to peatland size, runoff amount, and watershed extent in order to protect small, sensitive peatlands as well as larger, less sensitive peatland complexes Road construction engineering should endeavor to understand peatland hydrology in order to avoid changes in water levels ACKNOWLEDGMENTS Many of the ideas and data presented here were developed and collected during periods of funding from The Natural Sciences and Engineering Research Council of Canada and from The National Science Foundation (U.S.), for which I am grateful In particular, I thank Ilka Bauer, Jagtar Bhatti, Suzanne Bayley, Kevin Devito, Dennis Gignac, Linda Halsey, Barbara Nicholson, Merritt Turetsky, R Kelman Wieder, and Zicheng Yu for providing data and stimulating discussions, for offering many ideas that I have liberally used, and for friendship over the years Portions of the text were extracted from joint manuscripts of R Kelman Wieder and myself Sandi Vitt prepared the graphics, for which I am grateful REFERENCES Joosten, H and Clark, D., Wise Use of Mires and Peatlands — Background and Principles Including a Framework for Decision-Making, International Mire Conservation Group and International Peat Society, Saarijärven Offset Oy, Saarijärvi, Finland, 2002 Gorham, E., Northern peatlands: role in the carbon cycle and probable responses to climatic warming, Ecol Appl., 1, 182, 1991 Bohn, H.L., Estimate of organic carbon in world soils, Soil Sci Soc Am J., 40, 468, 1976 Bohn, H.L., Organic carbon in world soils, Soil Sci Soc Am J., 46, 1118, 1982 Sjörs, H., An arrangement of changes along gradients, with examples from successions in boreal peatlands, Vegetatio, 43, 1, 1980 Post, W.M., Emanuel, W.R., Zinke, P.J., and Stanberger, A.G., Soil carbon pools and world life zones, Nature, 298, 156, 1982 Houghton, J.T., Filho, L.G.M., Bruce, J., Lee, H., Callander, B.A., Haites, E., Harris, N., and Maskell, K., Radiative forcing of climate change, in Climate Change 1994, Houghton, J.T., Filho, L.G.M., Bruce, J., Lee, H., Callander, B.A., and Haites, E., Eds., Cambridge University Press, Cambridge, 1995, 231 pp Armentano, T.V and Menges, E.S., Patterns of change in the carbon balance of organic soil wetlands of the temperate zone, J Ecol., 74, 755, 1986 Markov, V.D., Olunin, A.S., Ospennikova, L.A., Skobeeva, E.I., and Khoroshev, P.I., World Peat Resources, Moscow ‘Nedra,’ 1988, 383 pp [in Russian] © 2006 by Taylor & Francis Group, LLC 214 Climate Change and Managed Ecosystems 10 National Wetlands Working Group Wetlands of Canada Ecological Land Classification Series, No 24 Sustainable Development Branch, Environment Canada, Ottawa, Ontario, and Polyscience Publications, Inc., Montreal, Quebec, 1988, 452 pp 11 Bhatti, J.S., personal communication, 2004 12 Vitt, D.H., Halsey, L.A., Bauer, I.E., and Campbell, C., Spatial and temporal trends of carbon sequestration in peatlands of continental western Canada through the Holocene, Can J Earth Sci., 37, 683, 2000 13 Vitt, D.H., Peatlands: Ecosystems dominated by bryophytes, in Bryophyte Biology, Shaw, A.J and Goffinet, B., Eds., Cambridge University Press, Cambridge, 2000, 312 14 Bauer, I.E and Vitt, D.H., Autogenic succession and its importance for the peatlands of Canada’s western boreal forests, in Peatlands Proceedings of the Peatland Conference 2002 in Hannover, Germany, Bauerochse, A and Hassmann, H., Eds., Leidorf, Rahden/Westf., 2003, 170 15 Yu, Z., Campbell, I.D., Vitt, D.H., and Apps, M.J., Modelling long-term peatland dynamics I Concepts, review, and proposed design, Ecol Modelling, 145, 197, 2001 16 Clymo, R.S., The limits to peat bog growth, Philos Trans R Soc Lond B, 303, 605, 1984 17 Halsey, L.A., Vitt, D.H., and Zoltai, S.C., Climatic and physiographic controls on wetland type and distribution in Manitoba, Canada, Wetlands, 17, 243, 1997 18 Johnson, L.C and Damman, A.W.H., Species-controlled Sphagnum decay on a South Swedish raised bog, Oikos, 61, 234, 1991 19 Johnson, L.C and Damman, A.W.H., Decay and its regulation in Sphagnum peatlands, Adv Bryol., 5, 249, 1993 20 Turetsky, M.R., The role of bryophytes in carbon and nitrogen cycling, Bryologist, 106, 395, 2003 21 Vitt, D.H., An overview of factors that influence the development of Canadian peatlands, Mem Entomol Soc Can., 169, 7, 1994 22 Alm, J., Talanov, A., Saarnio, S Silvola, J., Ilkkonen, E., Aaltonen, H., Nykänen, H., and Martikainen, P.J., Reconstruction of carbon balance for microsites in a boreal oligotrophic pine fen, Finland, Oecologia, 110, 423, 1997 23 Shurpali, N.J., Verma, J.K., and Arkebauer, T.J., Carbon dioxide exchange in a peatland ecosystem, J Geophys Res., 100, 14319, 1995 24 Suyker, A.E., Verma, S.B., and Arkebauer, T.J., Season-long measurement of carbon dioxide exchange in a boreal fen, J Geophys Res., 102, 29021, 1997 25 Lafleur, P.M., McCaughey, J.H., Jelinsky, D.E., Joiner D., and Bartlett, P., Seasonal trends in energy, water and carbon dioxide fluxes from a northern boreal wetland, J Geophys Res., 102, 29009, 1997 26 Carroll, P.J and Crill, P.M., Carbon balance of a temperate poor fen, Global Biogeochem Cycles, 11, 349, 1997 27 Waddington, J.M and Roulet, N.T., Atmosphere-wetland carbon exchange CO2 and CH4 exchange on the developmental topography of a peatland, Global Biogeochem Cycles, 10, 233, 1996 28 Turetsky, M.R., Wieder, R.K., Halsey, L.A., and Vitt, D.H., Current disturbance and the diminishing peatland carbon sink, Geophys Res Lett., 10.1029/2001GL014000, 2002 29 Turetsky, M.R., Wieder, R.K., Williams, C.J., and Vitt, D.H., Organic matter accumulation, peat chemistry, and permafrost melting in peatlands of boreal Alberta, Ecoscience, 7, 279, 2000 © 2006 by Taylor & Francis Group, LLC Peatlands: Canada’s Past and Future Carbon Legacy 215 30 Milich, L., The role of methane in global warming: where might mitigation strategies be focused? Global Environ Change, 9, 179, 1999 31 Scholes, M.C., Matrai, P.A., Smith, K.A., Andreae, M.C., and Guenther, A., Biosphere-atmosphere interactions, in The Changing Atmosphere Available online at http://medias.obs-mip.fr/igac/html/book/chap2/chap2.html, 2000 32 Gignac, L.D., Vitt, D.H., Zoltai, S.C., and Bayley, S.E., Bryophyte response surfaces along climatic, chemical, and physical gradients in peatlands of western Canada, Nova Hedw., 53, 27, 1991 33 Gignac, L.D and Vitt, D.H., Responses of northern peatlands to climate change: effects on bryophytes, J Hattori Bot Lab., 75, 119, 1993 34 Nicholson, B.J and Gignac, L.D., Ecotope dimensions of peatland bryophyte indicator species along environmental and climatic gradient in the Mackenzie River Basin, Bryologist, 98, 437, 1995 35 Nicholson, B.J., Gignac, L.D., and Bayley, S.E., Peatland distribution along a northsouth transect in the Mackenzie River Basin in relation to climatic and environmental gradients, Vegetatio, 126, 119, 1996 36 Nicholson, B.J., Gignac, L.D., Bayley, S.E., and Vitt, D.H., Vegetation response to global warming: Interactions between boreal forest, wetlands, and regional hydrology, in Mackenzie Basin Impact Study (MBIS), Final Report, Cohen, S.J., Ed., Environment Canada, Downsview, Ontario, 1997, 295 37 Vitt, D.H., Halsey, L.A., and Zoltai, S.C., The bog landforms of continental western Canada, relative to climate and permafrost patterns, Arctic Alpine Res., 26, 1, 1994 38 Halsey, L.A., Vitt, D.H., and Zoltai, S.C., Disequilibrium response of permafrost in boreal continental western Canada to climatic change, Climatic Change, 30, 57, 1995 39 Vitt, D.H., Halsey, L.A., and Zoltai, S.C., The changing landscape of Canada’s western boreal forest: the dynamics of permafrost, Can J For Res., 30, 283, 2000 40 Camill, P and Clark, J.S., Climate change disequilibrium of boreal permafrost peatlands caused by local processes, Am Nat., 1551, 202, 1998 41 Beilman, D.W., Vitt, D.H., and Halsey, L.A., Localized permafrost peatlands in western Canada: definition, distributions, and degradation, Arctic Antarctic Alpine Res., 33, 70, 2001 42 Campbell, I.D., Campbell, C., Vitt, D.H., Kelker, D., Laird, L.D., Trew, D., Kotak, B LeClair, D., and Bayley, S., A first estimate of organic carbon storage in Holocene lake sediments in Alberta, Canada, J Paleolimnol., 24, 395, 2000 43 Yu, Z., Campbell, I.D., Campbell, C., Vitt, D.H., Bond, G.C., and Apps, M.J., Carbon sequestration in western Canadian peat highly sensitive to Holocene wet-dry climate cycles at millennial timescales, Holocene, 13, 801, 2003 44 Campbell, I.D., Campbell, C., Yu, Z., Vitt, D.H., and Apps, M.J., Millennial-scale rhythms in peatlands in the western interior of Canada and in the Global Carbon Cycle, Quaternary Res., 54, 155, 2000 45 Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P., de Menocal, P., Priore, P., Cullen, H., Hajdas, I., and Bonani, G., A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates, Science, 278, 11257, 1999 46 Devito, K.J., Creed, I.F., and Fraser, C., Controls on runoff from a partially harvested aspen forested headwater catchment, boreal plain, Can Hydrol Process, 19, 3, 2005 47 Winter, T.C and Woo, M.-K., Hydrology of lakes and wetlands, in Surface Water Hydrology, Wolman, M.G and Riggs, H.C., Eds., Geological Society of America, Boulder, CO, 1990, 159 48 Montagnes, R.J.S., The habitat and distribution of Meesia triquetra in North America and Greenland, Bryologist, 93, 349, 1990 © 2006 by Taylor & Francis Group, LLC 216 Climate Change and Managed Ecosystems 49 Höper, H., Nitrogen and carbon mineralization rates in German agriculturally used fenlands, in Soil Ecological Processes in Wetlands of Germany, Broll, G., Merbach, W., and Pfeiffer, E.M., Eds., Springer, Berlin 2000 50 Yu, Z., Turetsky, M.R., Campbell, I.D., and Vitt, D.H., Modelling long-term peatland dynamics II Processes and rates as inferred from litter and peat-core data, Ecol Modelling, 145, 159, 2001 © 2006 by Taylor & Francis Group, LLC ...202 Climate Change and Managed Ecosystems Gorham,2 Bohn,3,4 Sjörs,5 Post et al.,6 Houghton et al.,7 Armentano and Menges,8 and Markov et al.9) Generally, carbon-rich peatland soils are... Francis Group, LLC 208 Climate Change and Managed Ecosystems FIGURE 10. 3 Geographical locations of extant peatlands (left) and projected distributions (right) by peatland type of sites in the... Callander, B.A., Haites, E., Harris, N., and Maskell, K., Radiative forcing of climate change, in Climate Change 1994, Houghton, J.T., Filho, L.G.M., Bruce, J., Lee, H., Callander, B.A., and