A Decade of Plant Species Changes on a Mire in the Italian Alps: Vegetation-Controlled or Climate-Driven Mechanisms?

Bragazza, Luca

doi:10.1007/s10584-005-9034-x

Cited by 39 publications

(46 citation statements)

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“…The observed loss of moisture in both plots dropping out of their bog alliances and plots remaining within it goes along with the observations of Bragazza (2006) on an southern Alpine bog and with the findings of Nordbakken (2001) and Gunnarsson et al (2002) in Swedish mires. Bragazza (2006) found autogenic reasons (mainly peat accumulation) for drying out, whereas Nordbakken (2001) and Gunnarsson et al (2002) name change in site factors to be responsible for it (reduced rainfall, altered waterflow from the surroundings).…”

Section: Vegetation Of Bogssupporting

confidence: 78%

“…Bragazza (2006) found autogenic reasons (mainly peat accumulation) for drying out, whereas Nordbakken (2001) and Gunnarsson et al (2002) name change in site factors to be responsible for it (reduced rainfall, altered waterflow from the surroundings). Our observations support the findings of Nordbakken (2001) and Gunnarsson et al (2002) rather than those of Bragazza (2006): At the same time as the plots were drying out, we observed a loss of soil humus content and increased soil-nutrient contents, indicating that peat is rather decomposed than accumulated. Gunnarsson et al (2002) also found in Sweden increased soil nutrient availability and increasing populations of trees and dwarf shrubs.…”

Section: Vegetation Of Bogsmentioning

confidence: 99%

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Veränderung der Schweizer Moorvegetation innerhalb von fünf Jahren

et al. 2010

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To assess whether short-term changes in mire vegetation can be detected using the phytosociological approach, paired vegetation relevés from two surveys of 112 mire sites of Switzerland were assigned to phytosociological alliances through a numerical approach. About 30% of the plots were assigned to different alliances in the two surveys. These transitions were analysed based on species frequencies and interpreted ecologically using Landolt's indicator values. Transitions between different alliances were more frequently related to the appearance of new species rather than to the disappearance of species. Transitions from and to peat bog communities were frequent. Many plots with fen vegetation were transformed into other wetland types. Fen-grassland increased in abundance, mainly at the cost of small-sedge fens. To reestablish the function of the Swiss mires as peat producers, we recommend to raise the mean summer water table to a maximum depth of 10 cm.

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Section: Vegetation Of Bogssupporting

confidence: 78%

Section: Vegetation Of Bogsmentioning

confidence: 99%

Veränderung der Schweizer Moorvegetation innerhalb von fünf Jahren

et al. 2010

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“…However, since peatland plant community compositions are known to be remarkably stable over time but experience changes in relative abundances (Rydin and Barber, 2001;Bragazza et al, 2006), we suggest that it was probably the vicinity to the reservoir that shaped the plant community composition at the sites over time, whereas the plant community actually drives C cycling.…”

Section: Long-term Insights Into Carbon Cycling At the Sitesmentioning

confidence: 89%

Differential response of carbon cycling to long-term nutrient input and altered hydrological conditions in a continental Canadian peatland

et al. 2018

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Abstract. Peatlands play an important role in global carbon cycling, but their responses to long-term anthropogenically changed hydrologic conditions and nutrient infiltration are not well known. While experimental manipulation studies, e.g., fertilization or water table manipulations, exist on the plot scale, only few studies have addressed such factors under in situ conditions. Therefore, an ecological gradient from the center to the periphery of a continental Canadian peatland bordering a eutrophic water reservoir, as reflected by increasing nutrient input, enhanced water level fluctuations, and increasing coverage of vascular plants, was used for a case study of carbon cycling along a sequence of four differently altered sites. We monitored carbon dioxide (CO 2 ) and methane (CH 4 ) surface fluxes and dissolved inorganic carbon (DIC) and CH 4 concentrations in peat profiles from April 2014 through September 2015. Moreover, we studied bulk peat and pore-water quality and we applied δ 13 C-CH 4 and δ 13 C-CO 2 stable isotope abundance analyses to examine dominant CH 4 production and emission pathways during the growing season of 2015. We observed differential responses of carbon cycling at the four sites, presumably driven by abundances of plant functional types and vicinity to the reservoir. A shrub-dominated site in close vicinity to the reservoir was a comparably weak sink for CO 2 (in 1.5 years: −1093 ± 794, in 1 year: +135 ± 281 g CO 2 m −2 ; a net release) as compared to two graminoid-moss-dominated sites and a moss-dominated site (in 1.5 years: −1552 to −2260 g CO 2 m −2 , in 1 year: −896 to −1282 g CO 2 m −2 ). Also, the shrub-dominated site featured notably low DIC pore-water concentrations and comparably 13 C-enriched CH 4 (δ 13 C-CH 4 : −57.81 ± 7.03 ‰) and depleted CO 2 (δ 13 C-CO 2 : −15.85 ± 3.61 ‰) in a more decomposed peat, suggesting a higher share of CH 4 oxidation and differences in predominant methanogenic pathways. In comparison to all other sites, the graminoid-mossdominated site in closer vicinity to the reservoir featured a ∼ 30 % higher CH 4 emission (in 1.5 years: +61.4 ± 32, in 1 year: +39.86 ± 16.81 g CH 4 m −2 ). Low δ 13 C-CH 4 signatures (−62.30 ± 5.54 ‰) indicated only low mitigation of CH 4 emissions by methanotrophic activity here. Pathways of methanogenesis and methanotrophy appeared to be related to the vicinity to the water reservoir: the importance of acetoclastic CH 4 production apparently increased toward the reservoir, whereas the importance of CH 4 oxidation increased toward the peatland center. Plant-mediated transport was the prevailing CH 4 emission pathway at all sites even where graminoids were rare. Our study thus illustrates accelerated carbon cycling in a strongly altered peatland with consequences for CO 2 and CH 4 budgets. However, our results suggest that long-term excess nutrient input does not necessarily lead to a loss of the peatland carbon sink function.

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“…At deposition levels higher than 18 kg N ha −1 year −1 , Sphagnum spp. become saturated with N and excess N leaches deeper into the system, which facilitates growth of vascular plants, changes nitrogen cycling and decomposition rates, and may result in degradation of peatlands (Lamers et al 2000;Bragazza 2006;Wu and Blodau 2013;Novak et al 2015). Moreover, high N availability in the form of NH 4 + ultimately could become toxic to wetland plants, especially under P-limited conditions ).…”

Section: Introductionmentioning

confidence: 99%

Effects of nitrogen fertilization on diazotrophic activity of microorganisms associated with Sphagnum magellanicum

et al. 2016

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Background and aims In pristine ombrotrophic Sphagnum-dominated peatland ecosystems nitrogen (N) is often a limiting nutrient, which is replenished by biological N 2 fixation and atmospheric N deposition. It is, however, unclear which impact long-term N deposition has on microbial N 2 fixing activity and diazotrophic diversity, and whether phosphorus (P) modulates the response. Therefore, we studied the impact of increased N deposition and N depletion on microbial N 2 fixation and diazotrophic diversity associated with the peat moss Sphagnum magellanicum, and their interaction with P availability. Methods Nitrogenase activities of S. magellanicumassociated microorganisms were determined by acetylene reduction assays (ARA) and 15 N 2 tracer methods on mosses from two geographically distinct locations with different N deposition histories, high or low N deposition, and in samples depleted in N (grown 3 years in the greenhouse) versus recent field samples. The short-term response to increased N deposition was tested for mosses differing in N and P fertilization histories. In addition, diversity of diazotrophic microorganisms was assessed by nifH gene amplicon sequencing of N-depleted mosses. Results We showed distinct and persistent differences in diazotrophic communities and their activities associated with S. magellanicum from sites with high versus low N deposition. Initially, diazotrophic activity was six times higher for the low N site. During incubation and repeated ARA, however, this activity strongly decreased, while it remained stable for the high N site. Activity for the high N site could not be increased by long-term experimental N deprivation. Short-term, experimental N application had an inhibitory effect on N 2 fixation for both sites, which was not observed in mosses with high indirect P availability. Conclusions We conclude that although N deposition negatively affects N 2 fixation as also shown in previous studies, long-term effects of N deprivation on the diazotrophic activity and community are more complex. Furthermore, our results indicated that P availability might be an important factor in modulating the response of Sphagnum-associated diazotrophs to N deposition.

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A Decade of Plant Species Changes on a Mire in the Italian Alps: Vegetation-Controlled or Climate-Driven Mechanisms?

Cited by 39 publications

References 50 publications

Veränderung der Schweizer Moorvegetation innerhalb von fünf Jahren

Veränderung der Schweizer Moorvegetation innerhalb von fünf Jahren

Differential response of carbon cycling to long-term nutrient input and altered hydrological conditions in a continental Canadian peatland

Effects of nitrogen fertilization on diazotrophic activity of microorganisms associated with Sphagnum magellanicum

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