Response of a Sphagnum bog plant community to elevated CO2 and N supply

Wageningen University
Plant Ecology (Impact Factor: 1.53). 08/2002; 162(1):123-134. DOI: 10.1023/A:1020368130679

ABSTRACT The response of plant growth to rising CO2 levels appears todepend on nutrient availability, but it is not known whether the growth of bogplants reacts similarly. We therefore studied the effects of elevatedCO2 in combination with N supply on the growth ofSphagnum mosses and vascular plants in ombrotrophic bogvegetation. Because the growth of Sphagnum is lessnutrient-limited than that of vascular plants, we hypothesized thatSphagnum would benefit from elevated CO2. In ourgreenhouse experiment, peat monoliths (34 cm diameter, 40cm deep) with intact bog vegetation were exposed to ambient (350ppmv) or elevated (560 ppmv) atmosphericCO2 combined with low (no N addition) or high (5 g Nm–2 yr–1 added) N deposition for twogrowing seasons. Elevated atmospheric CO2 had unexpected deleterious effectson the growth of Sphagnum
magellanicum, the dominant Sphagnumspecies. Growth was greatly reduced, particularly in the second growing seasonwhen, regardless of N supply, the mosses looked unhealthy. The negativeCO2 effect was strongest in the warmest months, suggesting a combinedeffect of elevated CO2 and the raised temperatures in the greenhouse.High N deposition favored Rhynchospora
alba, which became the dominant vascular plant speciesduring the experiment. Biomass increased more when N supply was high. There wereno significant effects of elevated CO2 on vascular plants, althoughelevated CO2 combined with high N supply tended to increase theaboveground vascular plant biomass. As Sphagnum is the maincarbon-sequestrating species in bogs and rising atmospheric CO2levels are likely to be followed by increases in temperature, there is an urgentneed for further research on the combined effects of elevated CO2 andincreased temperature on Sphagnum growth in bog ecosystems.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP) was created to evaluate our present ability to simulate large-scale wetland characteristics and corresponding methane (CH4) emissions. A multi-model comparison is essential to evaluate the key uncertainties in the mechanisms and parameters leading to methane emissions. Ten modelling groups joined WETCHIMP to run eight global and two regional models with a common experimental protocol using the same climate and atmospheric carbon dioxide (CO2) forcing datasets.We reported the main conclusions from the intercomparison effort in a companion paper (Melton et al., 2013). Here we provide technical details for the six experiments, which included an equilibrium, a transient, and an optimized run plus three sensitivity experiments (temperature, precipitation, and atmospheric CO2 concentration). The diversity of approaches used by the models is summarized through a series of conceptual figures, and is used to evaluate the wide range of wetland extent and CH4 fluxes predicted by the models in the equilibrium run. We discuss relationships among the various approaches and patterns in consistencies of these model predictions. Within this group of models, there are three broad classes of methods used to estimate wetland extent: prescribed based on wetland distribution maps, prognostic relationships between hydrological states based on satellite observations, and explicit hydrological mass balances. A larger variety of approaches was used to estimate the net CH4 fluxes from wetland systems. Even though modelling of wetland extent and CH4 emissions has progressed significantly over recent decades, large uncertainties still exist when estimating CH4 emissions: there is little consensus on model structure or complexity due to knowledge gaps, different aims of the models, and the range of temporal and spatial resolutions of the models.
    Geoscientific Model Development 06/2013; 6:617-641. · 5.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The composition of a peatland plant community has considerable effect on a range of ecosystem functions. Peatland plant community structure is predicted to change under future climate change, making the quantification of the direction and magnitude of this change a research priority. We subjected intact, replicated vegetated poor fen peat monoliths to elevated temperatures, increased atmospheric carbon dioxide (CO2 ), and two water table levels in a factorial design to determine the individual and synergistic effects of climate change factors on the poor fen plant community composition. We identify three indicators of a regime shift occurring in our experimental poor fen system under climate change: nonlinear decline of Sphagnum at temperatures 8 °C above ambient conditions, concomitant increases in Carex spp. at temperatures 4 °C above ambient conditions suggesting a weakening of Sphagnum feedbacks on peat accumulation, and increased variance of the plant community composition and pore water pH through time. A temperature increase of +4 °C appeared to be a threshold for increased vascular plant abundance; however the magnitude of change was species dependent. Elevated temperature combined with elevated CO2 had a synergistic effect on large graminoid species abundance, with a 15 times increase as compared to control conditions. Community analyses suggested that the balance between dominant plant species was tipped from Sphagnum to a graminoid-dominated system by the combination of climate change factors. Our findings indicate that changes in peatland plant community composition are likely under future climate change conditions, with a demonstrated shift toward a dominance of graminoid species in poor fens.
    Global Change Biology 06/2014; · 8.22 Impact Factor
  • Source
    01/2011: chapter 8: pages 213-241; CRC Press., ISBN: 9781439814246