Markus N. Thormann

The mycorrhizal status of the dominant vegetation along a peatland gradient in southern boreal Alberta, Canada

We investigated the mycorrhizal status of the dominant vascular plant species occurring in ten peatlands along a bog—fen—marsh gradient in southern boreal Alberta in 1997. All members of the Ericaceae were ericoid mycorrhizal, and members of the Salicaceae and Pinaceae were ectomycorrhizal. Also, some members of the Salicaceae and Betulaceae were simultancously ecto- and vesicular-arbuscular mycorrhizal (VAM). Fruiting bodies of the known ectomycorrhizal fungal generaCortinarius, Lactarius, andRussula were collected in late fall. Furthermore, the cosmopolitan ectomycorrhizal taxonCenococcum geophilum was associated with trees and shrubs in all fens and bogs. VA-mycorrhizal fungi were not found in any of the dominant herbaceous plant species in these peatlands; however, vesicles suggesting the presence of VAM fungi were found inCalamagrostis canadensis in the riverine marsh andRubus chamaemorus in the bog. NeitherCarex species in fens and marshes, norTypha latifolia in the lacustrine marsh were mycorrhizal; however, microsclerotia, sclerotial plaques, septate, aseptate, and clamped hyphae were observed to grow on and within cortical cells of their roots. Many of these hyphae were dematiaceous and may belong to theMycelium radicis atrovirens complex (MRA), partially consisting of the endophytic fungal generaPhialocephala andLeptodontidium. Hyphac resemblingRhizoctonia were also observed, although definitive identifications were not attempted. The ecological significance of MRA genera remains largely unknown. Thus, the dominant vegetation in southern boreal bogs and fens is mycorrhizal, possibly enabling these plant species to proliferate in these nutrient-poor ecosystems by accessing otherwise unavailable nutrient pools. In contrast, marsh vegetation is generally non-mycorrhizal, possibly due to higher surface-water nutrient concentrations and fluctuating water levels.

Aboveground net primary production along a bog-fen-marsh gradient in southern boreal Alberta, Canada

Abstract:Total aboveground plant production in a bog, three rich fens and two marshes were determined via the multiple harvest and cranked wire techniques. These peatlands follow a gradient of increasing pH, water flow, and surface water nutrient concentrations from the bog to the rich fens to the eutrophic marshes. The net primary production (NPP) values were as follows: (i) bog, 390 g m-2 year-1, (ii) three rich fens (riverine sedge fen, lacustrine sedge fen, and floating sedge fen), 409 g m-2 year-1, 277 g m-2 year-1 and 356 g m-2 year-1, respectively, and (iii) one riverine and one lacustrine marsh, 323 g m-2 year-1 and 757 g m-2 year-1, respectively. Overall, the bog and the three fens had a similar NPP but they were significantly less productive than the marshes. Along this bog-fen-marsh gradient, moss and shrub production decreased and herb production increased. Herb and moss production exhibited a greater variation between years than among sites within each year. Shrub production remained similar ...

ABOVEGROUND PEAT AND CARBON ACCUMULATION POTENTIALS ALONG A BOG-FEN-MARSH WETLAND GRADIENT IN SOUTHERN BOREAL ALBERTA, CANADA

Production-to-decomposition quotients and asymptotic limits of peat accumulation were determined to estimate peat and carbon accumulation potentials along a bog-fen-marsh wetland gradient in southern boreal Alberta. The wetlands were a bog, a poor fen (PF), a wooded moderate-rich fen (WRF), a lacustrine sedge fen (LSF), a riverine sedge fen (RSF), a riverine marsh (RM), and a lacustrine marsh (LM). First year mass losses increased along this gradient (bog 14%, fens 25–61%, marshes 57–62%), with second year total mass losses increasing from 18 to 38% from the bog to the moderate-rich fens. Ratios of aboveground net primary production to decomposition and asymptotic limits of peat accumulation showed decreasing trends from the bog to the fens to the marshes as decay rates increased along the same gradient. TheSphagnum-dominated sites (bog, PF) showed greater peat accumulation potentials than the brown moss-dominated sites (WRF, LSF) and those sites with an insignificant-to-no moss stratum (RSF, RM, LM), which is paralleled by their decreasing peat thicknesses. Rates of litter accumulation in the first year averaged 170 g m−2 yr−1 inSphagnum-dominated sites, 130 g m−2 yr−1 in brown moss-dominated sites, and 103 g m−2 yr−1 in sites with an insignificant-to-no moss stratum. All three wetland types showed similar carbon accumulation potentials (83, 67, and 50 g m−2 yr−1, respectively) after the first year of decomposition. Peat depth, asymptotic limits of peat accumulation, and production-to-decomposition ratios correlated negatively with water levels, pH, and Ca2+, and they correlated positively with moss and woody plant production (shrubs, trees). Peatlands with strong moss and shrub/tree strata (bog, PF, WRF) accumulate more peat than those wetlands dominated by graminoids (LSF, RSF, RM, LM). In the bog, high peat accumulation potentials may be related to low rates of decomposition. The peat accumulation potentials of some fens (PF, WRF) are similar to the bog and may be maintained by higher decomposition rates, which are offset by higher litter inputs. In the graminoid-dominated fens and marshes, peat accumulation potentials are lowest and may be related to higher litter quality, resulting in higher decomposition rates.

Decomposition along A moderate-rich fen-marsh peatland gradient in boreal Alberta, Canada

Losses of dry mass of the dominant litter, a standard litter (Carex aquatilis), and cellulose (Whatman filterpaper) were examined by the litter bag technique in three fens (riverine sedge fen, lacustrine sedge fen, floating sedge fen) and two marshes (lacustrine marsh, riverine marsh). LocalCarex lasiocarpa had a similar mass loss in marshes (mean of 63%) and in fens (mean of 59%) over 456 days in 1993 and 1994.Typha latifolia decomposed at a similar rate as the localC. lasiocarpa in the lacustrine marsh, whereasSalix pedicellaris decomposed significantly slower than the localC. lasiocarpa in the floating sedge fen (FSF). Overall, the mass loss of the standard plant litter was not significantly different between the fens (mean of 72%) and the marshes (mean of 69%). However, cellulose decomposed significantly faster in the marshes (mean of 67%) than it did in the fens (mean of 28%) over 100 days in 1994. Decay ofCarex aquatilis was best related to ammonium (NH4+) (r=0.73) in fens and the water level relative to the peat surface (r= 0.74) in marshes. Standard plant litter decomposition was best explained by surface water concentrations of NH4+(r=0.89) in fens and by soluble reactive phosphorus (SRP)(r=0.89) in marshes. Cellulose decomposition was best related to SRP in fens (r=0.70) and marshes (r=0.64) alike. An arithmetic/logarithmic decay model most accurately described plant mass losses during decomposition (59%) compared to the widely used logarithmic/arithmetic model (12%).

Aboveground plant production and nutrient content of the vegetation in six peatlands in Alberta, Canada

We examined the effects of water level, surface water chemistry, and climatic parameters on aboveground primary plant production, and the tissue nutrient concentrations in the dominant herb species in a bog, three fens, and two marshes. In the fens, total NPP correlated best with NO3- and total phosphorus surface water concentrations in 1993 and 1994. Total NPP in the marshes correlated best with alkalinity in 1993, and with soluble reactive phosphorus in 1994. Climatic parameters, such as mean annual growing season temperature, growing degree days, and precipitation, had the most notable effect on moss growth, whereas shrub and herb production correlated significantly with the water level relative to the moss surface. Herb production correlated positively and shrub production correlated negatively with the water level relative to the moss surface. Tissue nutrient concentrations of carbon (C), nitrogen (N), and total phosphorus (TP), and the C:N quotient in Carex lasiocarpa exhibited similar trends in the fens and the marshes. Carbon tissue concentrations in C. lasiocarpa remained unchanged, whereas N and TP tissue levels decreased throughout the growing season. In the site with the highest NPP and presumably the highest stand density, C. lasiocarpa exhibited the highest tissue N and TP levels. Furthermore, TP tissue concentrations in C. lasiocarpa were substantially higher in the marshes than in the fens. Tissue nutrient concentrations in Eriophorum vaginatum in the bog showed variable response patterns. N tissue levels increased, whereas tissue TP concentrations decreased from late June to late August. In the bog, E. vaginatum exhibited similar tissue TP levels to C. lasiocarpa in the fens; however, they were both substantially lower than those found in C. lasiocarpa from the marshes.

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.

Microfungi isolated from Sphagnum fuscum from a Southern Boreal Bog in Alberta, Canada

Abstract Microfungi were isolated from living and decomposing Sphagnum fuscum from a southern boreal bog in Alberta, Canada. Fifty-five fungi (three ascomycetes, three basidiomycetes, 11 zygomycetes, 28 Fungi Imperfecti, 10 unnamed mycelia sterilia) are described in this study. Of the Fungi Imperfecti, 21 species have known sexual states (teleomorph) in the Ascomycota, while the remaining seven species are known only from their asexual state (anamorph) and could not be assigned to specific teleomorphic families. Thirty-six species represent new records from Sphagnum and 45 species are new records for S. fuscum. Nearly 52% of the 45 identified fungi originated from three families, Mortierellaceae (10 taxa, Zygomycota), Trichocomaceae (8 taxa, Ascomycota), and Hypocreaceae (5 taxa, Ascomycota), with the remaining fungi representing 12 additional families. The 55 fungi have the ability to utilize a variety of carbon sources, such as cellulose, tannic acid, and pectin, and thus are important organisms involved the mineralization of carbon in peatlands.

Nitrogen mineralization and decomposition in western boreal bog and fen peat

ABSTRACT The nitrogen (N) supply is limited in many peatlands, and the mineralization of organic matter represents a major source of N to plants. The goal of this paper is to establish the relationship between decomposition rates, mineralization rates, and the N concentration of peat along a peatland gradient in four peatlands in western, boreal Canada. The four peatlands differ physically, chemically, and floristically and include a bog, a poor fen, and two moderate-rich fens, one wooded and the other open. The fens are enriched by ground water inputs, which we hypothesized led to higher concentrations of N in peat, faster decomposition of litter, and higher N mineralization rates. Net N mineralization was virtually identical to net ammonification over a 2-y period, both measured using an in situ incubation technique. Net daily mineralization rates increased from the bog to the open, moderate-rich fen, with intermediate values in the poor fen and moderate-rich wooded fen. This increasing trend along the bog–open, moderate-rich fen peatland gradient was mirrored for mineralization rates on a temporal and spatial basis. Virtually no nitrification was detected in any of the sites. Estimated aboveground integrated ecosystem decomposition rates ranged from 17%·y−1 in the bog to 31%·y−1 in the wooded, moderate-rich fen. Decomposition rates were significantly correlated with the mean daily net N mineralization rate and with total N in the upper 20 cm of peat. The net mineralization rate also was positively correlated with the total N content of the peat in 1991. The total N content of the peat increased from 5.8 mg·g−1 in the bog to 11.5 mg·g−1 in the open, moderate-rich fen, with poor fen and moderate-rich wooded fen values intermediate. The total C content of the peat ranged from 370 to 400 mg·g−1 and was not significantly different among the four peatlands. TC:TN quotients for the peat cores were 68 in the bog and 36–38 in the fens, correlating negatively with net ammonification rates. Based on our data, the processes of mineralization of N and decomposition are tightly linked processes, both of which were higher in the fens than in the bog in our four western continental peatlands. Moreover, both processes are more affected by the quality of the organic matter, as indicated by the TC:TN quotients of the surface peat, than by surface water chemistry variables.

RESPONSE OF ABOVEGROUND NET PRIMARY PLANT PRODUCTION TO NITROGEN AND PHOSPHORUS FERTILIZATION IN PEATLANDS IN SOUTHERN BOREAL ALBERTA, CANADA

In order to determine whether nitrogen (N) or phosphorus (P) limits aboveground plant growth in peatlands in Alberta, we fertilized one bog, two fens, and two marshes with N and P at a ratio of 7∶1 (Redfield ratio of these two elemental nutrients in aquatic plants) as well as with water without either fertilizer in 1994. The response of aboveground plant production to N or P was species-specific and varied among the sites. In the bog,Smilacina trifolia, a herb, showed significant increases in net primary production (NPP) after fertilization with N plus water and the addition of water, whileAndromeda polifolia only showed significant increases in NPP after fertilization with N plus water.Ledum groenlandicum, an ericaceous shrub, showed significant decreases in NPP after additions of N plus water, P plus water, and water, whileOxycoccus quadripetalus, another ericaceous shrub, also showed significant decreases of NPP after additions of N plus water and water.Sphagnum fuscum (moss) NPP increased significantly after the additions of water and decreased significantly after the additions of N plus water and P plus water. In the fens and marshes, onlyCarex spp. in the lacustrine sedge fen showed a significant increase in NPP after the addition of N. Vascular NPP (shrubs and herbs combined) did not increase significantly in any of the five peatlands. Total NPP (moss, herb, and shrub strata combined) increased significantly only in the bog after the addition of water due to the dominance of the moss stratum in that site. In the bog, moss growth was limited by water, and herb and shrub growth responses to N and P fertilization were species-specific. Neither N nor P limited aboveground plant production in the fens and marshes.

Effects of hydrologic changes on aboveground production and surface water chemistry in two boreal peatlands in Alberta: Implications for global warming

Aboveground net primary production (NPP) and surface water chemistryvariables were monitored in a lacustrine sedge fen and a bog for four years.There were no significant differences in precipitation, mean growing seasonannual temperature, and number of growing degree days from 1991 to 1994. Themean annual water levels in the lacustrine sedge fen differed significantly,whereas they were similar in the bog during these four years. We measured 15surface water variables in the lacustrine sedge fen and the bog, and foundthat only two correlated significantly with water level fluctuations. In thelacustrine sedge fen, calcium correlated positively (r2= 0.56) and nitrate correlated negatively (r2 =0.20) with water levels. In the bog, potassium correlated positively(r2 = 0.88) and total dissolved phosphorus correlatednegatively (r2 = 0.62) with water levels. The remainingchemical variables showed no significant correlations with water levelfluctuations. Net primary production of the different vegetation strataappeared to respond to different environmental variables. In the lacustrinesedge fen, graminoid production was explained to a significant degree bywater levels (r2 = 0.53), whereas shrub production wasexplained to a significant degree by surface water chemistry variables, suchas nitrate (r2 = 0.74) and total phosphorus(r2 = 0.22). In the bog, temperature was the onlyvariable that explained moss production to a significant degree(r2 = 0.71), whereas ammonium explained graminoidproduction (r2 = 0.66) and soluble reactive phosphorusexplained shrub production to significant degrees (r2 =0.71). There are few direct data on the impact of climatic warming in borealwetlands, although paleoecological and 2×CO2 model datahave provided some indications of past and possibly future changes invegetation composition, respectively. Our results suggest that thelacustrine sedge fen may succeed to a bog dominated by Sphagnum spp. andPicea mariana, whereas the bog may succeed to an upland-type forestecosystem.