Response of Sphagnum species mixtures to increased temperature and nitrogen availability
Breeuwer, A.J.G. ; Heijmans, M.M.P.D. ; Berendse, F. ; Gleichman, J.M. ; Robroek, B.J.M. ; Limpens, J. - \ 2009
Plant Ecology 204 (2009)1. - ISSN 1385-0237 - p. 97 - 111.
n-deposition - water-level - nutritional constraints - decomposition rates - northern peatlands - litter quality - climate-change - peat formation - growth - bogs
To predict the role of ombrotrophic bogs as carbon sinks in the future, it is crucial to understand how Sphagnum vegetation in bogs will respond to global change. We performed a greenhouse experiment to study the effects of two temperature treatments (17.5 and 21.7°C) and two N addition treatments (0 and 4 g N m¿2 year¿1) on the growth of four Sphagnum species from three geographically interspersed regions: S. fuscum, S. balticum (northern and central Sweden), S. magellanicum and S. cuspidatum (southern Sweden). We studied the growth and cover change in four combinations of these Sphagnum species during two growing seasons. Sphagnum height increment and production were affected negatively by high temperature and high N addition. However, the northern species were more affected by temperature, while the southern species were more affected by N addition. High temperature depressed the cover of the `wet¿ species, S. balticum and S. cuspidatum. Nitrogen concentrations increased with high N addition. N:P and N:K ratios indicated P-limited growth in all treatments and co-limitation of P and K in the high N treatments. In the second year of the experiment, several containers suffered from a severe fungal infection, particularly affecting the `wet¿ species and the high N treatment. Our findings suggest that global change can have negative consequences for the production of Sphagnum species in bogs, with important implications for the carbon sequestration in these ecosystems
Long-term effects of climate change on vegetation and carbon dynamics in peat bogs
Heijmans, M.M.P.D. ; Mauquoy, D. ; Geel, B. van; Berendse, F. - \ 2008
Journal of Vegetation Science 19 (2008)3. - ISSN 1100-9233 - p. 307 - 320.
increased nitrogen deposition - increased n deposition - vulgaris l hull - vascular plants - sphagnum bogs - british-isles - northern peatlands - biological flora - boreal peatlands - solar-activity
Questions: What are the long-term effects of climate change on the plant species composition and carbon sequestration in peat bogs?Methods: We developed a bog ecosystem model that includes vegetation, carbon, nitrogen and water dynamics. Two groups of vascular plant species and three groups of Sphagnum species compete with each other for light and nitrogen. The model was tested by comparing the outcome with long-term historic vegetation changes in peat cores from Denmark and England. A climate scenario was used to analyse the future effects of atmospheric CO2, temperature and precipitation.Results: The main changes in the species composition since 1766 were simulated by the model. Simulations for a future warmer, and slightly wetter, climate with doubling CO2 concentration suggest that little will change in species composition, due to the contrasting effects of increasing temperatures (favouring vascular plants) and CO2 (favouring Sphagnum). Further analysis of the effects of temperature showed that simulated carbon sequestration is negatively related to vascular plant expansion. Model results show that increasing temperatures may still increase carbon accumulation at cool, low N deposition sites, but decrease carbon accumulation at high N deposition sites.Conclusions: Our results show that the effects of temperature, precipitation, N-deposition and atmospheric CO2 are not straightforward, but interactions between these components of global change exist. These interactions are the result of changes in vegetation composition. When analysing long-term effects of global change, vegetation changes should be taken into account and predictions should not be based on temperature increase alone.
Effects of elevated CO2 and N deposition on CH4 emissions from European mires
Silvola, J. ; Saarnio, S. ; Foot, J. ; Sundh, I. ; Greenup, A. ; Heijmans, M.M.P.D. ; Ekberg, A. ; Mitchell, E.P. ; Breemen, N. van - \ 2003
Global Biogeochemical Cycles 17 (2003)2 - 1068. - ISSN 0886-6236 - p. 37 - 1-37-12.
atmospheric carbon-dioxide - methane emissions - boreal mire - raised co2 - northern peatlands - water-table - nitrogen deposition - bog vegetation - forest soils - temperature
 Methane fluxes were measured at five sites representing oligotrophic peatlands along a European transect. Five study plots were subjected to elevated CO2 concentration (560 ppm), and five plots to NH4NO3 (3 or 5 g N yr(-1)). The CH4 emissions from the control plots correlated in most cases with the soil temperatures. The depth of the water table, the pH, and the DOC, N and SO4 concentrations were only weakly correlated with the CH4 emissions. The elevated CO2 treatment gave nonsignificantly higher CH4 emissions at three sites and lower at two sites. The N treatment resulted in higher methane emissions at three sites (nonsignificant). At one site, the CH4 fluxes of the N-treatment plots were significantly lower than those of the control plots. These results were not in agreement with our hypotheses, nor with the results obtained in some earlier studies. However, the results are consistent with the results of the vegetation analyses, which showed no significant treatment effects on species relationships or biomass production.
How litter quality affects mass loss and N loss from decomposing Sphagnum
Limpens, J. ; Berendse, F. - \ 2003
Oikos 103 (2003)3. - ISSN 0030-1299 - p. 537 - 547.
increased nitrogen deposition - elevated atmospheric co2 - swedish raised bog - vascular plants - heathland ecosystems - northern peatlands - potential decay - central alberta - carbon-dioxide - growth
Nitrogen (N) deposition may affect litter decomposition and may thus have an impact on the rate of carbon (C) sequestration in Sphagnum peatlands. We present results from four separate experiments aimed at delineating the effects of litter N-enrichment, Sphagnum species, stem part of Sphagnum, and place of incubation on decomposition rate and N release. We measured mass loss and N loss from litterbags incubated at 10-15 cm in the field for one year. Mass loss was positively related to the N/C quotient of the litter, but depended strongly on the range in N/C quotients observed; only a distinct difference in N/C quotients affected mass loss. Although hummock species decayed at a slower rate than hollow species, the differences between the species became less pronounced for old stem parts and for N-enriched litter. Old stem parts decayed at a slower rate than young stem parts, except for S. papillosum. Neither position of incubation (low hummock or hollow), nor the inorganic N concentration of the incubation environment affected mass loss. N loss was mainly determined by, and positively related to, the N/C quotient of the litter; species and stem part had minor effects. Above a N/C quotient of about 0.015, net N loss was observed for all species. We conclude that decomposition of Sphagnum is stimulated by N deposition. As the latter also affects litter N concentration and thus N release, we think that positive feedbacks through changing litter quality should be taken into account when modelling the effects of N deposition on Sphagnum peatlands and C sequestration in these systems.