Part of the missing sink in the global CO 2 budget has been attributed to the positive effects of... more Part of the missing sink in the global CO 2 budget has been attributed to the positive effects of CO 2 fertilization and N deposition on carbon sequestration in Northern Hemisphere terrestrial ecosystems. The genus Sphagnum is one of the most important groups of plant species sequestrating carbon in temperate and northern bog ecosystems, because of the low decomposability of the dead material it produces. The effects of raised CO 2 and increased atmospheric N deposition on growth of Sphagnum and other plants were studied in bogs at four sites across Western Europe. Contrary to expectations, elevated CO 2 did not sig-ni®cantly affect Sphagnum biomass growth. Increased N deposition reduced Sphagnum mass growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum. Such changes in plant species composition may decrease carbon sequestration in Sphagnum-dominated bog ecosystems.
Climate change is expected to cause extensive vegetation changes in the Arctic: deciduous shrubs ... more Climate change is expected to cause extensive vegetation changes in the Arctic: deciduous shrubs are already expanding, in response to climate warming. The results from transect studies suggest that increasing shrub cover will impact significantly on the surface energy balance. However, little is known about the direct effects of shrub cover on permafrost thaw during summer. We experimentally quantified the influence of Betula nana cover on permafrost thaw in a moist tundra site in northeast Siberia with continuous permafrost. We measured the thaw depth of the soil, also called the active layer thickness (ALT), ground heat flux and net radiation in 10 m diameter plots with natural B. nana cover (control plots) and in plots in which B. nana was removed (removal plots). Removal of B. nana increased ALT by 9% on average late in the growing season, compared with control plots. Differences in ALT correlated well with differences in ground heat flux between the control plots and B. nana removal plots. In the undisturbed control plots, we found an inverse correlation between B. nana cover and late growing season ALT. These results suggest that the expected expansion of deciduous shrubs in the Arctic region, triggered by climate warming, may reduce summer permafrost thaw. Increased shrub growth may thus partially offset further permafrost degradation by future temperature increases. Permafrost models need to include a dynamic vegetation component to accurately predict future permafrost thaw.
[I] Mosses are an important component of the boreal forest, but little is known about their contr... more [I] Mosses are an important component of the boreal forest, but little is known about their contribution to ecosystem carbon, water, and energy exchange. We studied the role of mosses in boreal forest evapotranspiration by conducting two experiments in a black spruce forest in Fairbanks, Alaska. Moss evaporation was measured using lysimeters filled with Hylocomium splendens or Sphagnum capillifolium. Microclimate and moisture content were varied by placing the lysimeters in different habitats (dense forest, open forest, bog), and by manipulating the water supply (no water, natural rainfall, water added). Moss evaporation rates between 1 June and 8 September averaged 0.3, 0.9, and 1.5 mm dayp1 in the dense forest (Hylocomium), open forest (Hylocomium and Sphagnum), and bog (Sphagnum) respectively. Assuming a total forest evapotsai~spiration rate of 2 mm dayp1, this study shows that moss evaporation contributes considerably to boreal black spruce forest evapotranspiration. Moss evaporation rates depended strongly on the openness of the forest and to a lesser degree on the density of the vascular plant-canopy and on moss species. The strong influence of habitat suggests that microclimate is the primary factor determining moss evaporation rates. Hylocomium
The Bog Ecosystem Research Initiative (BERI) projectwas initiated to investigate, at five climati... more The Bog Ecosystem Research Initiative (BERI) projectwas initiated to investigate, at five climaticallydifferent sites across Europe, the effects of elevatedCO 2 and N deposition on the net exchange ofCO 2 and CH 4 between bogs and the atmosphere, and to study the effects of elevated CO 2 and Ndeposition on the plant biodiversity of bogcommunities. A major challenge to investigate theeffects of elevated CO 2 on vegetation andecosystems is to apply elevated CO 2 concentrations to growing vegetation without changingthe physical ...
... GROSVERNIER, CHRISTER ALBINSSON, HÀKAN RYDIN, MONIQUE MPD HEIJMANS, MARCEL R. HOOSBEEK, ALISS... more ... GROSVERNIER, CHRISTER ALBINSSON, HÀKAN RYDIN, MONIQUE MPD HEIJMANS, MARCEL R. HOOSBEEK, ALISSON GREENUP, JONATHAN FOOT, TIMO ... vegetation is well established an is dominated by Eriophorum vaginatum, Scirpus caespitosus, Erica tetralix and ...
Part of the missing sink in the global CO 2 budget has been attributed to the positive effects of... more Part of the missing sink in the global CO 2 budget has been attributed to the positive effects of CO 2 fertilization and N deposition on carbon sequestration in Northern Hemisphere terrestrial ecosystems. The genus Sphagnum is one of the most important groups of plant species sequestrating carbon in temperate and northern bog ecosystems, because of the low decomposability of the dead material it produces. The effects of raised CO 2 and increased atmospheric N deposition on growth of Sphagnum and other plants were studied in bogs at four sites across Western Europe. Contrary to expectations, elevated CO 2 did not sig-ni®cantly affect Sphagnum biomass growth. Increased N deposition reduced Sphagnum mass growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum. Such changes in plant species composition may decrease carbon sequestration in Sphagnum-dominated bog ecosystems.
Climate change is expected to cause extensive vegetation changes in the Arctic: deciduous shrubs ... more Climate change is expected to cause extensive vegetation changes in the Arctic: deciduous shrubs are already expanding, in response to climate warming. The results from transect studies suggest that increasing shrub cover will impact significantly on the surface energy balance. However, little is known about the direct effects of shrub cover on permafrost thaw during summer. We experimentally quantified the influence of Betula nana cover on permafrost thaw in a moist tundra site in northeast Siberia with continuous permafrost. We measured the thaw depth of the soil, also called the active layer thickness (ALT), ground heat flux and net radiation in 10 m diameter plots with natural B. nana cover (control plots) and in plots in which B. nana was removed (removal plots). Removal of B. nana increased ALT by 9% on average late in the growing season, compared with control plots. Differences in ALT correlated well with differences in ground heat flux between the control plots and B. nana removal plots. In the undisturbed control plots, we found an inverse correlation between B. nana cover and late growing season ALT. These results suggest that the expected expansion of deciduous shrubs in the Arctic region, triggered by climate warming, may reduce summer permafrost thaw. Increased shrub growth may thus partially offset further permafrost degradation by future temperature increases. Permafrost models need to include a dynamic vegetation component to accurately predict future permafrost thaw.
[I] Mosses are an important component of the boreal forest, but little is known about their contr... more [I] Mosses are an important component of the boreal forest, but little is known about their contribution to ecosystem carbon, water, and energy exchange. We studied the role of mosses in boreal forest evapotranspiration by conducting two experiments in a black spruce forest in Fairbanks, Alaska. Moss evaporation was measured using lysimeters filled with Hylocomium splendens or Sphagnum capillifolium. Microclimate and moisture content were varied by placing the lysimeters in different habitats (dense forest, open forest, bog), and by manipulating the water supply (no water, natural rainfall, water added). Moss evaporation rates between 1 June and 8 September averaged 0.3, 0.9, and 1.5 mm dayp1 in the dense forest (Hylocomium), open forest (Hylocomium and Sphagnum), and bog (Sphagnum) respectively. Assuming a total forest evapotsai~spiration rate of 2 mm dayp1, this study shows that moss evaporation contributes considerably to boreal black spruce forest evapotranspiration. Moss evaporation rates depended strongly on the openness of the forest and to a lesser degree on the density of the vascular plant-canopy and on moss species. The strong influence of habitat suggests that microclimate is the primary factor determining moss evaporation rates. Hylocomium
The Bog Ecosystem Research Initiative (BERI) projectwas initiated to investigate, at five climati... more The Bog Ecosystem Research Initiative (BERI) projectwas initiated to investigate, at five climaticallydifferent sites across Europe, the effects of elevatedCO 2 and N deposition on the net exchange ofCO 2 and CH 4 between bogs and the atmosphere, and to study the effects of elevated CO 2 and Ndeposition on the plant biodiversity of bogcommunities. A major challenge to investigate theeffects of elevated CO 2 on vegetation andecosystems is to apply elevated CO 2 concentrations to growing vegetation without changingthe physical ...
... GROSVERNIER, CHRISTER ALBINSSON, HÀKAN RYDIN, MONIQUE MPD HEIJMANS, MARCEL R. HOOSBEEK, ALISS... more ... GROSVERNIER, CHRISTER ALBINSSON, HÀKAN RYDIN, MONIQUE MPD HEIJMANS, MARCEL R. HOOSBEEK, ALISSON GREENUP, JONATHAN FOOT, TIMO ... vegetation is well established an is dominated by Eriophorum vaginatum, Scirpus caespitosus, Erica tetralix and ...
Peat bogs have accumulated more atmospheric carbon (C) than any other terrestrial ecosystem today... more Peat bogs have accumulated more atmospheric carbon (C) than any other terrestrial ecosystem today. Most of this C is associated with peat moss (Sphagnum) litter. Atmospheric nitrogen (N) deposition can decrease Sphagnum production, compromising the C sequestration capacity of peat bogs. The mechanisms underlying the reduced production are uncertain, necessitating multifactorial experiments.
Uploads
Papers by Monique Eijmans