Linda A. Halsey

Disequilibrium response of permafrost in boreal continental western Canada to climate change

In the boreal forest of continental western Canada, permafrost is restricted toSphagnum-dominated peatlands on which air photo interpretation reveals the occurrence of five types of surface physiography. Concentrated in the northern part of the boreal forest, permafrost is present in peat plateaus with and without collapse scars. In the southern part of the boreal forest, continental bogs dominate, representing ombrotrophic peatlands that have never contained permafrost. In the midboreal zone, internal lawns are present in bogs and in fens. These internal lawns do not presently contain permafrost but did in the recent past, representing degradation of permafrost since the Little Ice Age. Evaluation of the distribution of these peat landforms indicates that today 30% of bogs contain permafrost at the −0.4 °C isotherm and 50% of bogs contain permafrost at the −1.2 °C isotherm, whereas in the past, 30% of bogs contained permafrost at the −1.4 °C isotherm and 50% of bogs contained permafrost at the −2.3 °C isotherm. Although spatial degradation has occurred with a shifting of permafrost northwards in response to warming since the Little Ice Age, permafrost cover has increased in any given area where present-day temperatures are between 0.5 and −3.5 °C.

Response of Sphagnum fuscum to Nitrogen Deposition: A Case Study of Ombrogenous Peatlands in Alberta, Canada

Abstract Peatlands cover about 30% of northeastern Alberta and are ecosystems that are sensitive to nitrogen deposition. In polluted areas of the UK, high atmospheric N deposition (as a component of acid deposition) has been considered among the causes of Sphagnum decline in bogs (ombrogenous peatlands). In relatively unpolluted areas of western Canada and northern Sweden, short-term experimental studies have shown that Sphagnum responds quickly to nutrient loading, with uptake and retention of nitrogen and increased production. Here we examine the response of Sphagnum fuscum to enhanced nitrogen deposition generated during 34 years of oil sands mining through the determination of net primary production (NPP) and nitrogen concentrations in the upper peat column. We chose six continental bogs receiving differing atmospheric nitrogen loads (modeled using a CALPUFF 2D dispersion model). Sphagnum fuscum net primary production (NPP) at the high deposition site (Steepbank—mean of 600 g/m2; median of 486 g/m2) was over three times as high than at five other sites with lower N deposition. Additionally, production of S. fuscum may be influenced to some extent by distance of the moss surface from the water table. Across all sites, peat nitrogen concentrations are highest at the surface, decreasing in the top 3 cm with no significant change with increasing depth. We conclude that elevated N deposition at the Steepbank site has enhanced Sphagnum production. Increased N concentrations are evident only in the top 1-cm of the peat profile. Thus, 34 years after mine startup, increased N-deposition has increased net primary production of Sphagnum fuscum without causing elevated levels of nitrogen in the organic matter profile. A response to N-stress for Sphagnum fuscum is proposed at 14–34 kg ha−1 yr−1. A review of N-deposition values reveals a critical N-deposition value of between 14.8 and 15.7 kg ha−1 yr−1 for NPP of Sphagnum species.

Sphagnum-dominated Peatlands in North America Since the Last Glacial Maximum: Their Occurrence and Extent

Abstract Sphagnum-dominated peatlands occupy extensive tracts of land throughout the Boreal and Subarctic regions of North America, extending north onto the Low Arctic of the Canadian Shield and south along the west coast of Oregon, Rocky Mountains of Wyoming, and Appalachians of West Virginia. In addition, short pocosins found along the southeastern coast also can be considered as Sphagnum-dominated peatlands, even though they differ significantly from traditional concepts of boreal peatlands. Along the southern limit of Sphagnum-dominated peatlands, where climate is limiting, edaphic factors allow for the development of outliers. As the current distribution of Sphagnum-dominated peatlands is related to Sphagnum spore rain, past distributions of Sphagnum-dominated peatlands can be constructed from spore records preserved in lakes and peatlands. Here we present six time slices extending back to the Last Glacial Maximum to determine how Sphagnum-dominated peatlands have varied in both time and space. The spore record indicates that Sphagnum-dominated peatlands were present in North America during the Last Glacial Maximum although they were spatially limited to central Alaska, the Olympic Peninsula and Puget Trough of Washington, and to a narrow band in the eastern states of Kentucky, North Carolina, Tennessee, and Maryland. During the Late Wisconsinan Sphagnum-dominated peatlands shifted northwards in eastern North America and expanded farther into Alaska and the Midwest. The Late Wisconsinan/Holocene transition marks a time of overall increase in the area supporting Sphagnum-dominated peatlands, while extending farther in eastern Canada and western continental and coastal regions, they almost completely disappear in the Midwest where they were extensive earlier. Sphagnum-dominated peatlands generally reach their current extent about 2,000–3,000 years ago. Sphagnum-dominated peatlands have dramatically changed their distribution and abundance since the Last Glacial Maximum, and hence the carbon that is stored in these present-day important sinks has also changed dramatically. When compared to the estimated 220 Pg of carbon stored in North American peatlands today, less than 10% of this carbon was present in these peatland during the LGM.

Peatland Initiation During the Holocene in Continental Western Canada

Today, the southern limit of peatlands in continental western Canada is largely limited by thermal seasonal aridity, although physiographic parameters of substrate texture, topography, and salinity also exsert important controls on the presence and absence of peatlands. Factors that control peatland distribution today also operated in the past, thus the initiation of peatlands during the Holocene was mainly limited by aridity and physiography. Calibrated radiocarbon dates of basal peat deposits from 90 locations across continental western Canada indicate that peat formation began approximately 8,000 to 9,000 years BP in nucleation zones along the upper elevations of the Montane region of Alberta and in northern Alberta uplands after an initial deglacial lag. Predictions of maximum early Holocene summer insolation by climate simulations provide a mechanism for limiting peatland establishment during the early Holocene. From 6,000 to 8,000 years ago, peat formation in continental western Canada expanded eastwards into Manitoba responding to decreases in summer insolation. Peatland expansion during the early Holocene was more extensive in Alberta than in Manitoba in response to a southwesterly shift in the Arctic front. The displacement of the Arctic front allowed for more frequent incursions of moist Pacific air into Alberta while limiting it in Manitoba. After 6,000 years BP, the trend of southeasterly peatland expansion continued. Peatlands are youngest in the southern Boreal Forest and Aspen Parkland Region as well as in the lower elevations of the Peace-Wapiti River drainage basin, forming over the last 3,000 to 4,000 years. Peatlands are also young in the lower elevations of the Hudson Bay Lowlands where peat initiation has been limited by timing of emergence from glacial rebound. The spatial and temporal distribution of peatland initiation during the Holocene is verified by existing pollen records and corroborates some simulated climate models.

Localized Permafrost Peatlands in Western Canada: Definition, Distributions, and Degradation

Detailed inventory of peatlands by aerial photography shows that peatlands with climatically sensitive localized islands of permafrost cover 17,505 km2 within a broad band of occurrence in continental western Canada (Alberta, Saskatchewan, and Manitoba). Within this zone, 37.5% of the total area covered by bog, and 9.1% of total area covered by fen have localized permafrost landforms (frost mounds and/or internal lawns). Regional distribution of the presence/absence of localized permafrost peatlands relative to expansive peat plateaus (peatland completely underlain by permafrost) shows that a north to south landform gradient exists that is dominantly controlled by mean annual temperature. Percent cover of localized permafrost peatland in an area is best explained by the amount of total peatland cover that can support it. Localized permafrost is associated with collapse forms (internal lawns) throughout the range of its occurrence in western Canada. In some locations permafrost has completely melted, moving the current southern limit of permafrost north by 39 km on average, and by as much as 200 km.

CLIMATIC AND PHYSIOGRAPHIC CONTROLS ON WETLAND TYPE AND DISTRIBUTION IN MANITOBA, CANADA

Wetlands represent a substantial part of Manitoba’s terrestrial landscape, covering 233,340 km2 or 43% of the province; peatlands represent 90% of all wetlands. A wetland inventory for Manitoba is presented following a classification scheme grounded in wetland function, vegetation, and landform. The province is subdivided into twelve wetland regions each having distinctive wetland types and abundances. A hybrid Detrended Canonical Correspondance Analysis (DCCA) indicates that wetland distribution in the province is largely controlled by allogenic factors of climate and physiography. The first canonical axis represents the variance in wetland distribution occurring along a north-to-south gradient within the province. In northern Manitoba, permafrost bogs dominate, replaced southwards by bogs without permafrost and fens with and without internal lawns. Farther south, peatlands are replaced by non-peat-accumulating wetlands. This wetland distributional gradient is most strongly correlated to mean annual temperature, with thermal seasonal aridity, annual precipitation, and moisture deficit (precipitation-potential evaporation) also significant. Significant allogenic variables correlated to the first canonical axis are not restricted to climate alone. The type of bedrock geology in the area also plays an important role in determining wetland distribution, with bogs occurring preferentially in areas of acidic bedrock, while fens are found on calcareous bedrock. The second canonical axis represents a surface-water flow gradient, with patterned fens and marshes having relatively large amounts of surface-water flow on one end and nonpermafrost bogs and swamps with low amounts of surface-water flow on the other. Texture of the subsurface is the most important variable explaining the second axis, with sediments having high hydraulic conductivity correlated to wetlands with high surface-water flow, while sediments with low hydraulic conductivity are related to wetlands with low surface-water flow. Annual precipitation is also a statistically significant variable explaining the variance in wetland distribution along the second axis.

Patterns of Bryophyte Richness in a Complex Boreal Landscape: Identifying Key Habitats at McClelland Lake Wetland

Abstract The McClelland Lake Wetland Complex is a large (3,481 ha), boreal, wetland complex dominated by peatlands located in northeastern Alberta, Canada. We intensively sampled the bryophyte flora in 44 sites chosen to capture all landscape features of the wetland. We furthermore partitioned these 44 sites into 67, structurally defined stands. One hundred and fourteen species of bryophytes (91 mosses and 23 hepatics) were found. Mean stand species richness is 16.6, with a range of 2–41 species. Thirty-nine species were recorded only 1–2 times in the 67 stands and these are defined as locally rare species. Additionally, 18 species were recorded that are currently on the Alberta Rare Species Tracking List (ANHIC), although commonness of some within the complex suggests regional under-collection. A strong relationship was found between species richness and locally rare species occurrence at both the site and stand levels. Neither species richness nor locally rare species occurrence is related to landscape position within the wetland complex nor to internal wetland chemical gradients. Both species richness and local species rarity are influenced by stand type and structure. Shrubby, wooded, or forested stands contain 70% of the locally rare species occurrences, and swamps and wooded fens are species rich habitats. Stands with high numbers of locally rare species also tend to be stands that have high species richness; however, not all stands with high species richness have high numbers of locally rare bryophytes. Indicators and assessment protocols based on rare species and richness are developed to define Key Habitats for this wetland complex. Criteria for Key Habitats are stands with both high species richness and high numbers of locally rare species—‘Category 6’ stands, and these are identified as significant features in developing management protocols for bryophyte species and wetland function. Six ‘Category 6’ stands capture 58% of the locally rare species and 90% of the total wetland species richness. All six Key Habitats are wooded or forested.

Spatial patterning of net primary production in wetlands of continental western Canada

Abstract Net primary production in wetlands of continental western Canada (Alberta, Saskatchewan, Manitoba) is mapped and summarized by wetland type and ecoregion. The region contains 405 300 km2 of wetlands, with peatlands representing 90.1% of all wetlands. Based on a regional synthesis of published values of net primary production, shrubby swamp and marsh wetlands produce more biomass annually through the process of net primary production than peatlands. Different peatland types appear to sequester similar amounts of plant biomass on an annual basis, with the exception of permafrost bogs that sequester less. Wetland net primary production for the region is calculated as 2.1 ¥ 1014 g yr-1 of plant biomass, with 73.5% sequestered in peatlands. This is equivalent to 9.95 ¥ 1013 g yr-1 of carbon. Provincially this carbon is partitioned into 50% for Manitoba, 30% for Alberta, and 20% for Saskatchewan. Over the last 1000 years, an average of only 5% of this biomass (and carbon) accumulate as peat, with most lost through the process of decomposition. When the annual amount of carbon that accumulates as peat is compared to the amount emitted provincially as anthropogenic greenhouse gases, wetlands present in each of the provinces accumulate 4% (Alberta), 8% (Saskatchewan), and 62% (Manitoba) of the emitted carbon annually. Wetlands in continental western Canada are a significant, active biosphere carbon sink following accumulation patterns of the last one thousand years. Future changes, particularly in fire frequency or intensity, may alter this accumulation pattern.

The Effects of Water Chemistry on the Growth of Scorpidium scorpioides in Canada and The Netherlands

Scorpidium scorpioides (Hedw.) Limpr. is a characteristic species of rich fens, where its chemical environment is one of high pH, calcium content, alkalinity, and conductivity. It often forms a dominant component of rich fen peat deposits. When grown under experimental conditions, Canadian plants of this species respond differently than plants from The Netherlands. Canadian plants respond best when grown in extreme-rich fen waters, while plants from The Netherlands respond best in waters from moderate-rich fens and in nutrient enhanced conditions. Saline waters yield no or limited growth responses from plants in both areas. The results suggest ecotypic variation between plants from the two continents. Also, the results suggest that chemical factors (i.e., saline water) affect the presence and growth of S. scorpioides. These chemical factors may have had an influence on the past distribution of the species. Abstract. Scorpidium scorpioides (Hedw.) Limpr. is a characteristic species of rich fens, where its chemical environment is one of high pH, calcium content, alkalinity, and conductivity. It often forms a dominant component of rich fen peat deposits. When grown under experimental conditions, Canadian plants of this species respond differently than plants from The Netherlands. Canadian plants respond best when grown in extreme-rich fen waters, while plants from The Netherlands respond best in waters from moderate-rich fens and in nutrient enhanced conditions. Saline waters yield no or limited growth responses from plants in both areas. The results suggest ecotypic variation between plants from the two continents. Also, the results suggest that chemical factors (i.e., saline water) affect the presence and growth of S. scorpioides. These chemical factors may have had an influence on the past distribution of the species. Abstract. Scorpidium scorpioides (Hedw.) Limpr. is a characteristic species of rich fens, where its chemical environment is one of high pH, calcium content, alkalinity, and conductivity. It often forms a dominant component of rich fen peat deposits. When grown under experimental conditions, Canadian plants of this species respond differently than plants from The Netherlands. Canadian plants respond best when grown in extreme-rich fen waters, while plants from The Netherlands respond best in waters from moderate-rich fens and in nutrient enhanced conditions. Saline waters yield no or limited growth responses from plants in both areas. The results suggest ecotypic variation between plants from the two continents. Also, the results suggest that chemical factors (i.e., saline water) affect the presence and growth of S. scorpioides. These chemical factors may have had an influence on the past distribution of the species. Brown mosses, composed of species in the genera Calliergon, Calliergonella, Campylium, Cratoneu- ron, Drepanocladus s.l., Meesia, Scorpidium, and Tomentypnum-along with a few of the more hy- grophytic species of Brachythecium and Hypnum - are characteristic of rich-fen habitats, peatlands characterized by minerotrophic, alkaline (see Wet- zel 1975) water. Nutrients, especially nitrogen and phosphorus, are present in the surface waters in low amounts. However, due to seasonal flow of water, plants are able to take up more nutrients than are present in oligotrophic bogs; thus rich fens are me- sotrophic ecosystems (Vitt & Kuhry 1992). Three types of base-rich (Ca, Mg, or Na) fens occur in boreal western Canada. Moderate-rich fens are characterized by pHs between 5.5 and 7.0, small amounts of bicarbonate, somewhat seasonally vari- able water tables, and no marl deposition. Char- acteristic species include Brachythecium mildean- um (Schimp.) Schimp. in Milde, Calliergonella cuspidata (Hedw.) Loeske, Drepanocladus aduncus (Hedw.) Warnst., D. aduncus var. polycarpus (Bland. ex Voit) G. Roth, D. lapponicus (Norrl.) Smirn., D. vernicosus (Mitt.) Warnst., and Helodium blandowii (Web. & Morh) Warnst. (Chee & Vitt 1989). Ex- treme-rich fens have pHs higher than 6.5, large Brown mosses, composed of species in the genera Calliergon, Calliergonella, Campylium, Cratoneu- ron, Drepanocladus s.l., Meesia, Scorpidium, and Tomentypnum-along with a few of the more hy- grophytic species of Brachythecium and Hypnum - are characteristic of rich-fen habitats, peatlands characterized by minerotrophic, alkaline (see Wet- zel 1975) water. Nutrients, especially nitrogen and phosphorus, are present in the surface waters in low amounts. However, due to seasonal flow of water, plants are able to take up more nutrients than are present in oligotrophic bogs; thus rich fens are me- sotrophic ecosystems (Vitt & Kuhry 1992). Three types of base-rich (Ca, Mg, or Na) fens occur in boreal western Canada. Moderate-rich fens are characterized by pHs between 5.5 and 7.0, small amounts of bicarbonate, somewhat seasonally vari- able water tables, and no marl deposition. Char- acteristic species include Brachythecium mildean- um (Schimp.) Schimp. in Milde, Calliergonella cuspidata (Hedw.) Loeske, Drepanocladus aduncus (Hedw.) Warnst., D. aduncus var. polycarpus (Bland. ex Voit) G. Roth, D. lapponicus (Norrl.) Smirn., D. vernicosus (Mitt.) Warnst., and Helodium blandowii (Web. & Morh) Warnst. (Chee & Vitt 1989). Ex- treme-rich fens have pHs higher than 6.5, large Brown mosses, composed of species in the genera Calliergon, Calliergonella, Campylium, Cratoneu- ron, Drepanocladus s.l., Meesia, Scorpidium, and Tomentypnum-along with a few of the more hy- grophytic species of Brachythecium and Hypnum - are characteristic of rich-fen habitats, peatlands characterized by minerotrophic, alkaline (see Wet- zel 1975) water. Nutrients, especially nitrogen and phosphorus, are present in the surface waters in low amounts. However, due to seasonal flow of water, plants are able to take up more nutrients than are present in oligotrophic bogs; thus rich fens are me- sotrophic ecosystems (Vitt & Kuhry 1992). Three types of base-rich (Ca, Mg, or Na) fens occur in boreal western Canada. Moderate-rich fens are characterized by pHs between 5.5 and 7.0, small amounts of bicarbonate, somewhat seasonally vari- able water tables, and no marl deposition. Char- acteristic species include Brachythecium mildean- um (Schimp.) Schimp. in Milde, Calliergonella cuspidata (Hedw.) Loeske, Drepanocladus aduncus (Hedw.) Warnst., D. aduncus var. polycarpus (Bland. ex Voit) G. Roth, D. lapponicus (Norrl.) Smirn., D. vernicosus (Mitt.) Warnst., and Helodium blandowii (Web. & Morh) Warnst. (Chee & Vitt 1989). Ex- treme-rich fens have pHs higher than 6.5, large

INFLUENCE OF PEATLANDS ON THE ACIDITY OF LAKES IN NORTHEASTERN ALBERTA, CANADA

About a third of the lakes surveyed in the Birch Mountains Upland of northeastern Alberta, Canada, have pH below 7.0; 25% have alkalinities below 10 mg/L identifying them as acid-sensitive following criteria established by the National Research Council of Canada (1981). Lakes in this region vary greatly as to surface area and depth. Watersheds also vary in area and in amount of peatland cover. Peatlands in the form of peat plateaus and collapse scars, continental bogs, treed and open fens, and shallow organic deposits cover over 50% of some watersheds. Surface water chemistries of these peatlands form three distinct classes: bogs, poor fens and shallow organic deposits. The acidity of certain lakes in this northern area is best explained by effects from high cover ofSphagnum-dominated peatlands in surrounding watersheds. Due to greater flow-through, poor fens appear to be more important than bogs in affecting the acidity of associated lakes.