Peatland Plant Research Articles

Gradients of continentality and moisture in South Patagonian ombrotrophic peatland vegetation

This study presents the analysis of 381 phytosociological releves describing predominantly ombrotrophic South Patagonian lowland peatland vegetation along a gradient of increasing continentality. Numerical methods such as cluster analysis and detrended correspondence analysis (DCA) were carried out to explore the data set. Cluster analysis resulted in nine vegetation types that were also distinctly separated in DCA ordination. The major floristic coenocline along the first DCA axis reflected a gradient of continentality ranging from pacific blanket bogs dominated by cushion plants toSphagnum-dominated continental raised bogs. Increasing continentality along the first axis was parallel with decreasing peat decomposition and increasing peat depth and acidity. In contrast, floristic variation along the second DCA axis represented a water level gradient. The typical sequence of vegetation types along the hollow-hummock moisture gradient that is well established for north hemispherical peatlands could also be observed inSphagnum-dominated South Patagonian raised bogs with a surprising similarity in floristic and structural features. Concerning the gradient of continentality significant differences in comparison with the northern hemisphere could be established. Most obvious was the dominance of cushion building plants (e.g.Astelia pumila, Donatia fascicularis) in South Patagonian oceanic peatlands, whereas this life form is totally absent from the northern hemisphere. Similar to the continentalSphagnum bogs the cushion plant vegetation of hyperoceanic peatlands exhibited a clear separation along the moisture gradient.

Elevated CO2 Effects on Peatland Plant Community Carbon Dynamics and DOC Production

Northern peatlands are important stores of carbon and reservoirs of biodiversity that are vulnerable to global change. However, the carbon dynamics of individual peatland plant species is poorly understood, despite the potential for rising atmospheric CO2 to affect the vegetation’s contribution to overall ecosystem carbon function. Here, we examined the effects of 3 years exposure to elevated CO2 (eCO2) on (a) peatland plant community composition and biomass, and (b) plant carbon dynamics and the production of dissolved organic carbon (DOC) using a 13CO2 pulse–chase approach. Results showed that under eCO2, Sphagnum spp. cover declined by 39% (P < 0.05) and Juncus effusus L. cover increased by 40% (P < 0.001). There was a concurrent increase in above- and belowground plant biomass of 115% (P < 0.01) and 96% (P < 0.01), respectively. Vascular species assimilated and turned over more 13CO2-derived carbon than Sphagnum spp. (49% greater turnover of assimilated 13C in J. effusus and F. ovina L. leaf tissues compared with Sphagnum, P < 0.01). Elevated CO2 also produced a 66% rise in DOC concentrations (P < 0.001) and an order of magnitude more ‘new’ exudate 13DOC than control samples (24 h after 13CO2 pulse-labelling 2.5 ± 0.5 and 0.2 ± 0.1% in eCO2 and control leachate, respectively, P < 0.05). We attribute the observed increase in DOC concentrations under eCO2 to the switch from predominantly Sphagnum spp. to vascular species (namely J. effusus), leading to enhanced exudation and decomposition (litter and peat). The potential for reduced peatland carbon accretion, increased DOC exports and positive feedback to climate change are discussed.

Effects of logging in the southern boreal peatlands of Manitoba, Canada

To evaluate changes in surface water chemistry, peat, and the plant community in logged peatlands, we compared plots in 1–4 year old (class I) and 9–12 year old (class II) clearcuts with plots in wooded controls. Indicator species were significantly different between wooded and clear-cut plots but not between clear-cut plot age classes. Surface waters in class I clearcuts had significantly higher temperature and nutrients compared with controls, and this was attributed to warming of the soil, which resulted in faster decomposition and greater nutrient availability. Hummocks, important peatland plant microhabitats, were reduced in height in all clearcuts because of compaction and abrasion. These abiotic changes caused a shift in the plant community. Total plant diversity was approximately 30% higher on clearcuts and consisted primarily of herbs, particularly grasses. However, bryophyte and lichen diversity and cover was greatest in wooded controls. Picea mariana (Mill.) BSP regeneration was not compromised by clear-cutting and was greater in class II clearcuts. Greater diversity and cover of Salix species in class II clearcuts suggests stable shrub community formation, which may be persistent and may slow succession. The use of appropriate equipment to minimize site disturbances while the ground is frozen may reduce long-term shifts in the plant community.

Biological diversity of peatlands in Canada

Knowledge about the biodiversity of Canada’s vast peatlands is poor largely because peatlands have not been routinely differentiated from other types of habitats. Plants are better known than the animals. Systematic surveys of peatland plants began in the late 1800s, but did not begin in earnest until the 1950s. With the exception of a few marshes, peatlands are classified into bogs (18 forms), fens (17 forms), and swamps (21 forms). Bogs are the most widespread compared to fens and swamps. Peatlands occur throughout most of Canada but are most common in the Boreal, Subarctic, and Arctic Wetland Regions. Species richness for plants clearly separates bogs and fens. Average number of total species is greater in fens than in bogs. Species richness of herbs, fern and fern allies, and bryophytes is greater in fens than in bogs, and it is greater in bogs for trees and lichens. Bryophytes contribute the most to species richness in bogs, while herbs are most important in fens. Bogs on the Atlantic coast appear to have greater species numbers of lichens and shrubs than bogs on the Pacific coast. Herbs likely contribute more to total species numbers in fens in eastern Canada than in western Canada. There are species of mammals, birds, herptiles, biting flies, beetles, dragon-flies, water mites, rotifers, and protozoans that are restricted to peatlands or are found in both peatlands and other habitats.

Long-term effects of deer browsing and trampling on the vegetation of peatlands

Overabundance of wild ungulates, especially exotic species, is a major threat to several ecosystems worldwide. While the response of forest vegetation to high density of herbivores has been well studied, far less is known about peatland vegetation. In this paper, we assessed the long term impact of white-tailed deer ( Odocoileus virginianus) on plant communities of ombrotrophic (bog) and minerotrophic (fen) peatlands in eastern North America. Vegetation of five peatlands that have experienced high deer densities for at least 75 years was compared with that of five peatlands situated at proximity but on deer-free islands. We investigated deer impacts on plant species composition and cover, shrub height and cloudberry ( Rubus chamaemorus) fruit/flower production and morphology. In bogs, white-tailed deer had no long-term impact on plant species assemblages, but reduced lichen cover and increased sedges and grasses cover as well as the surface area of bare peat. On the other hand, the floristic composition of fens differed significantly between sites where deer were present or absent. Plant diversity was greater in undisturbed fens than in disturbed fens, especially for shrubs, sedges and liverworts. No detrimental effects of browsing on shrub height were observed. Conversely, deer browsing seemed to have deleterious impacts on cloudberry fruit/flower production as well as on the number of leaves per individual. Overall, our results suggest that white-tailed deer had some important impacts on the vegetation of peatlands that could be harmful for the long-term conservation of peatland plant diversity.

Litter controls plant community composition in a northern fen

The accumulation of litter or thatch can affect plant community composition by affecting the temperature, nutrient availability, and light availability of the soil environment, thereby forming a potentially important linkage between recent productivity and current ecosystem processes. To investigate the importance of litter on a fen peatland plant community, we conducted a litter addition and removal experiment in a fen in northern Minnesota, USA, between 1998 and 2001. The addition of litter had little effect on fen plant community composition or microenvironmental variables, despite a two‐fold increase in litter mass compared to control plots. However, the removal of litter dramatically increased cover of Rhynchospora fusca and R. alba, and reduced cover of Carex exilis. Litter removal also increased availability of light and soil temperature and increased the phosphorus content of aboveground plant biomass. Our results indicate that litter is an important control of plant community composition in this northern fen.

Piping and woody plants in peatlands: Cause or effect?

This paper presents, for the first time, evidence to show that Calluna species are one causative factor of piping in blanket peat catchments. Ground‐penetrating radar survey on 960 plots illustrated that piping was prevalent throughout blanket peats. However, soil pipe occurrence was significantly higher where bare peat (149 pipes/km) or Calluna (87 pipes/km) were present compared to other species (67 pipes/km). A case study catchment where there was an altitudinal limit to Calluna provided some control over potential factors that may lead to an association between piping and Calluna. Under the controlled conditions of topographic index, peat depth, and water table, piping was greater under the Calluna‐covered peat than under other vegetation covers. Laboratory experiments demonstrated that 10 years worth of rainfall was enough to almost double the proportion of macropore flow occurring in recently colonized Calluna peatlands. This suggests that given enough water and time, the woody Calluna plants result in water being preferentially channeled through the upper peat. Improvements are therefore required in our understanding of the relationships between peatland plant nutrient and water supply and the feedbacks between ecosystem functioning and landform development. These results are also important given the propensity to encourage Calluna growth for game bird enhancement in many northern peatlands.

Plant Species Numbers Predicted by a Topography-based Groundwater Flow Index

We measured net ecosystem exchange of carbon dioxide (CO2) (NEE) during wet and dry summers (2000 and 2001) across a range of plant communities at Mer Bleue, a large peatland near Ottawa, southern Ontario, Canada. Wetland types included ombrotrophic bog hummocks and hollows, mineral-poor fen, and beaver pond margins. NEE was significantly different among the sites in both years, but rates of gross photosynthesis did not vary spatially even though species composition at the sites was variable. Soil respiration rates were very different across sites and dominated interannual variability in summer NEE within sites. During the dry summer of 2001, net CO2 uptake was significantly smaller, and most locations switched from a net sink to a source of CO2 under a range of levels of photosynthetically active radiation (PAR). The wetter areas—poor fen and beaver pond margin— had the largest rates of CO2 uptake and smallest rates of respiratory loss during the dry summer. Communities dominated by ericaceous shrubs (bog sites) maintained similar rates of gross photosynthesis between years; by contrast, the sedge-dominated areas (fen sites) showed signs of early senescence under drought conditions. Water table position was the strongest control on respiration in the drier summer, whereas surface peat temperature explained most of the variability in the wetter summer. Q 10 temperature-respiration quotients averaged 1.6 to 2.2. The ratio between maximum photosynthesis and respiration ranged from 3.7:1 in the poor fen to 1.2:1 at some bog sites; it declined at all sites in the drier summer owing to greater respiration rates relative to photosynthesis in evergreen shrub sites and a change in both processes in sedge sites. Our ability to predict ecosystem responses to changing climate depends on a more complete understanding of the factors that control NEE across a range of peatland plant communities.

Vegetation patterns and biodiversity of peatland plant communities surrounding mid-boreal wetland ponds in Alberta, Canada

Peatland plant communities surrounding small (&lt;200 ha) boreal ponds were characterized by indicator species, water and peat chemistry, and diversity. Peatland–pond complexes are common in boreal Alberta and are found in three different landforms (clay-till plain, outwash plain, and moraine). Pond area and perimeter were larger in the clay-till plain than in other landforms, although not significantly different. Across the three landforms, cluster analysis detected five peatland communities: marshes, wet open fens, dry open fens, treed fens, and bogs. The zonation pattern of communities surrounding the ponds varied at all sites, and there was no typical pattern, except that marshes were always found closest to water. Based on the bryophyte species, most communities are considered moderate-rich fens. Nonmetric multidimensional scaling indicated communities fell along a wet-to-dry gradient and a bare-to-vegetated gradient. Water depth and temperature, peat depth, and peat C/N ratios differed between open and treed peatland communities, and pH was similar in all communities. Alpha and gamma diversity was highest in the treed fen and lowest in the marsh community in both total species and bryophyte species. The total number of plant species, some of which are considered rare, found in all communities was 139.Key words: marsh, fen, bog, classification, vegetation ecology, diversity.

Simulating the impacts of distal volcanic products upon peatlands in northern Britain: an experimental study on the Moss of Achnacree, Scotland

The potential impact of prehistoric volcanism on distal areas has been the subject of some discussion in both ecology and archaeology. An experimental approach is used here to examine the potential effects of distant volcanism on a peatland environment. Simulations of different tephra and acidity loading, designed to approximately replicate the prehistoric Hekla-4 ashfall, were monitored over 2 years. Impacts on the peatland ecosystem were assessed by qualitative observations of plant health and abundance, semi-quantitative observations of flowering, measurements of peat pH, humification and testate amoebae community composition. Plots with higher acid loading showed immediate and lasting impacts on plants, although other treated plots were less affected. Changes in testate amoebae and peat humification were inconsistent both within and between plots. The experiment demonstrates the potentially severe effects of high acid loading on peatland plants, although some responses remain unclear.

On the Use of Shallow Basins to Restore Cutover Peatlands: Plant Establishment

Abstract Since the early 1990s, restoration techniques have been developed for milled and cutover peatlands in eastern Canada. These techniques are based on the active reintroduction of peatland plant diaspores, blocking drainage, and the use of straw mulch to improve surface conditions. This study examines the effectiveness of using shallow (20 cm deep) basins of various widths to improve the success of current peatland restoration techniques. It comprises three different experiments, each spanning three or four growing seasons and combining both small‐scale manual and large‐scale mechanized plant reintroductions. Cover data recorded in two of the experiments were regressed against a series of environmental factors to determine how Sphagnum establishment success was related to abiotic variables such as moisture, water ponding, surface roughness, and mulch cover. Results of these experiments demonstrate that shallow basins were generally effective at promoting Sphagnum establishment and that this effect extends beyond the positive impact that basins have on hydrological conditions. Basins of various widths were equally successful. Soil‐moisture content (linear positive effect) and duration and severity of flooding events (quadratic effect) were shown to be determinant of plant recovery. Other factors such as the density of straw cover (positive effect) and surface roughness (negative effect) were also instrumental in explaining local variation in Sphagnum cover. Plant cover after three and four growing seasons averaged 20–25% in mechanical reintroductions and 40–60% in manual reintroductions, demonstrating the overall effectiveness of the restoration techniques used.

PH and nutrient effects on above-ground net primary production in a Minnesota, USA bog and fen

Nutrient limitation is often assumed to be similar among the species of a plant community. However, limitation can differ among ecosystems and among life forms and individual species within a particular ecosystem. Peatlands have some of the lowest nutrient availabilities and highest acidities among wetland types, but the relative roles of nutrient limitation and pH stress in structuring peatland plant communities are unknown. Accordingly, we measured changes in above-ground net primary production (ANPP) and percent cover of plants to additions of low levels of N, P, and calcium carbonate in a bog and fen in northern Minnesota, USA. Plots were treated for three years with a combination of 2 or 6 g N m−2 yr−1 as ammonium, 0.67 or 2 g P m−2 yr−1, and/or calcium carbonate to raise the pH of the bog from 3.8 to 4.9 and the pH of the fen from 4.9 to 6.4. In the bog, the low N treatment increased ANPP, whereas the high N treatment inhibited ANPP. Lime addition also stimulated ANPP. The whole-community bog response was largey due to bryophytes, which accounted for 76% of ANPP on average. However, the productivity of the shrub community (18% of total ANPP) increased with P additions but only during the third year of fertilizer application. Productivity of the bog graminoids did not respond significantly to any addition. Fen ANPP was stimulated by P addition, but the effect was isolated to graminoids (95% of total ANPP), and this was largely due to the response of Carex exilis. Our results suggest that low nutrient availability does not necessarily imply nutrient limitation of peatland plant communities. Furthermore, life forms and individual species responded differently, indicating that there are several levels of nutrient limitation within each peatland community. In particular, bog Sphagnum mosses appear to have a very low tolerance for N. Production and community structure were controlled by N-availability and pH in the bog and by P-availability in the fen.

Potential effects of warming and drying on peatland plant community composition

AbstractBoreal peatlands may be particularly vulnerable to climate change, because temperature regimes that currently constrain biological activity in these regions are predicted to increase substantially within the next century. Changes in peatland plant community composition in response to climate change may alter nutrient availability, energy budgets, trace gas fluxes, and carbon storage. We investigated plant community response to warming and drying in a field mesocosm experiment in northern Minnesota, USA. Large intact soil monoliths removed from a bog and a fen received three infrared warming treatments crossed with three water‐table treatments (n = 3) for five years. Foliar cover of each species was estimated annually.In the bog, increases in soil temperature and decreases in water‐table elevation increased cover of shrubs by 50% and decreased cover of graminoids by 50%. The response of shrubs to warming was distinctly species‐specific, and ranged from increases (for Andromeda glaucophylla) to decreases (for Kalmia polifolia). In the fens, changes in plant cover were driven primarily by changes in water‐table elevation, and responses were species‐ and lifeform‐specific: increases in water‐table elevation increased cover of graminoids – in particular Carex lasiocarpa and Carex livida– as well as mosses. In contrast, decreases in water‐table elevation increased cover of shrubs, in particular A. glaucophylla and Chamaedaphne calyculata. The differential and sometimes opposite response of species and lifeforms to the treatments suggest that the structure and function of both bog and fen plant communities will change – in different directions or at different magnitudes – in response to warming and/or changes in water‐table elevation that may accompany regional or global climate change.

Succession of microfungal assemblages in decomposing peatland plants

We investigated the microfungal assemblages in the decomposing tissues of dominant plant species in two peatlands in southern boreal Alberta, Canada, to determine if distinct patterns of succession of microfungi occurred throughout the first two years of decomposition. These plant species were Sphagnum fuscum from a bog and Carex aquatilis leaves and rhizomes and Salix planifolia leaves and roots from a riverine, sedge-dominated fen. Canonical correspondence analyses, a multivariate statistical analysis used infrequently in mycological research, revealed distinct patterns of fungal species succession in two of the five litters (S. fuscum and C. aquatilis leaves). Furthermore, our analyses showed that substantially different microfungal assemblages were associated with these litters within the first two years of decomposition. Litter quality variables, such as total nitrogen, total phosphorus, and total carbon tissue nutrient concentrations, explained most of the succession patterns and differences in the microfungal assemblages of these five litters. Our data did not reveal the classical taxonomic zygomycete – ascomycete/fungi imperfecti – basidiomycete pattern of succession during organic matter decomposition. Similarly, a succession of functional groups of microfungi, i.e., cellulose-degraders preceding lignin-degraders, generally was not apparent. Instead, microfungi with broad spectra of enzymatic abilities co-existed over the first two years of decomposition in these peatland plant litters. These microfungi have a limited ability to decompose complex phenolic polymers, such as lignin, resulting in the accumulation of peat in these ecosystems. Some microfungal taxa were not affected by changes in litter quality, environmental variables, or surface water chemistry and were present at all stages of decomposition.

Peatland fragments of southern Quebec: recent evolution of their vegetation structure

One of the main problems associated with small natural reserves is their progressive loss of ecological integrity owing to the influence of surrounding human activities. In southern Quebec (Bas-Saint-Laurent, Canada), peatlands are extensively mined to extract peat for the production of horticultural compost and are isolated within agricultural lands. Government environmental agencies have proposed that peat industries set aside 5-10% of a bog's area as a natural refuge for peatland plants and animals. Do these fragments constitute reliable refuges? Do they maintain their ecological characteristics over a long period? We studied the recent evolution of plant communities in peatland fragments using paleoecological techniques and a geographical information system. In the study area, some treeless fragments dominated by Sphagnum species have recently (since 1940) converted to forest sites. Macrofossil and dendrochronological analyses suggest that peat-mining activities were not the main factors responsible for the afforestation of peatland fragments. On the other hand, the isolation of the Bas-Saint-Laurent peatlands within an agricultural plain for more than 100 years may explain the afforestation process (drainage activities). Furthermore, fires may have accelerated afforestation by facilitating the spread of seeds of tree species with serotinous cones. Because most peatlands of the Bas-Saint-Laurent region are still affected by drainage and fires, it is probable that several open bog fragments will not maintain their treeless vegetation structure over a long period. Consequently, peatland fragments should not be considered as a solution to long-term conservation needs in southern Quebec, at least not for plant and animal species of open bogs. This study also shows that even ecosystems known to be resistant to invasions by exotic species (such as peatlands) can be strongly affected by fragmentation and by their surrounding environment on a long-term basis.Key words: peatland, peat mining, fire, fragmentation, conservation, Quebec.

Peatland fragments of southern Quebec: recent evolution of their vegetation structure

One of the main problems associated with small natural reserves is their progressive loss of ecological integ - rity owing to the influence of surrounding human activities. In southern Quebec (Bas-Saint-Laurent, Canada), peatlands are extensively mined to extract peat for the production of horticultural compost and are isolated within agricultural lands. Government environmental agencies have proposed that peat industries set aside 5-10% of a bog's area as a nat- ural refuge for peatland plants and animals. Do these fragments constitute reliable refuges? Do they maintain their eco - logical characteristics over a long period? We studied the recent evolution of plant communities in peatland fragments using paleoecological techniques and a geographical information system. In the study area, some treeless fragments dominated by Sphagnum species have recently (since 1940) converted to forest sites. Macrofossil and dendrochronological analyses suggest that peat-mining activities were not the main factors responsible for the afforesta - tion of peatland fragments. On the other hand, the isolation of the Bas-Saint-Laurent peatlands within an agricultural plain for more than 100 years may explain the afforestation process (drainage activities). Furthermore, fires may have accelerated afforestation by facilitating the spread of seeds of tree species with serotinous cones. Because most peatlands of the Bas-Saint-Laurent region are still affected by drainage and fires, it is probable that several open bog fragments will not maintain their treeless vegetation structure over a long period. Consequently, peatland fragments should not be considered as a solution to long-term conservation needs in southern Quebec, at least not for plant and animal species of open bogs. This study also shows that even ecosystems known to be resistant to invasions by exotic species (such as peatlands) can be strongly affected by fragmentation and by their surrounding environment on a long- term basis.

Composition of Phenolic Compounds, Fatty Acids and Sterols in Peatland Plants

Composition of Phenolic Compounds, Fatty Acids and Sterols in Peatland Plants

Comparison of Saccharide Composition in Peatland Plants and Different Types of Peat Profiles

Comparison of Saccharide Composition in Peatland Plants and Different Types of Peat Profiles

Water table control of CH4 emission enhancement by vascular plants in boreal peatlands

Removal of the vascular vegetation (Eriophorum vaginatum) at two sites in a Swedish boreal peatland decreased the seasonal CH4 flux by 55 to 85%, while the daily CH4 flux at a Canadian boreal peatland with Carex rostrata removed decreased by over 30%. Dissolved CH4 pore water concentrations in the rooting zone were 1.2 to 2.5 times greater than the storage at similar sites where vegetation was removed by clipping, suggesting that the removal of vascular vegetation decreased CH4 production. Moreover, nighttime CH4 flux enhancement was coincident with the diurnal peak in dissolved CH4 pore water concentration. A positive correlation between mean daily net ecosystem production and mean daily CH4 flux (r2 = 0.655, n = 8) at lawn sites with sedge vegetation suggests that sites with greater CO2 fixation had a higher CH4 flux, likely through enhanced methanogenesis and transport. The degree of vascular vegetation CH4 flux enhancement, however, changed throughout the growing season and was correlated to the position of the water table. Under low water table conditions the presence of vascular plant cover has a lesser effect in enhancing CH4 emissions, indicating that CH4 and net ecosystem exchange coupling is limited to vascular plants and only to sites that remain wet with the water table near the surface.

Methane Efflux from Emergent Vegetation in Peatlands

1 Methane emissions from emergent plants in two peatlands were measured in plant enclosure experiments. During the summer growing season, methane emissions on a plant dry mass basis from Scheuchzeriapalustris (130 + 14 4umol g-' day-') were higher than from other peatland plants, such as Chamaedaphne calyculata (20 + 3 umol g-' day-') and Carex oligosperma (91 + 38 4umol g-' day-'), but were lower than from Calla palustris (280 + 37 umol g-' day-'). 2 The contribution to net methane efflux from S. palustris, the dominant emergent plant in one peatland, was 15.6 + 2.2 mmol m-2 day-', based on the plant enclosure experiments and areal biomass measurements. These results were not significantly different from the difference between measurements of methane efflux using chambers enclosing clipped and unclipped plots (12.0-27.9 mmol m-2 day-'). 3 We determined that methane transport through S. palustris contributed between 64 and 90% of the net methane efflux from the peatland, while the other peatland without plants capable of rapid methane transport had significantly lower methane efflux. The higher annual efflux from peat with aerenchymatous plants appears to be due to several factors, including increased substrate production which enhances methane production, reduction in methane oxidation, as well as easier methane transport from the site of production. 4 Plants capable of transporting methane regulated the methane pool in the saturated zone by depleting both dissolved methane in the pore-waters and the concentration of methane in gas bubbles trapped in the saturated peat. 5 Our experiments indicate that methane transport through S. palustris is due to molecular diffusion, and is not influenced by pressurization or stomatal aperture.