Tables showing geographical details and characterization of a soil profile at the Glas Maol study... more Tables showing geographical details and characterization of a soil profile at the Glas Maol study site, means and standard errors of mean (SE) of carbon and nutrient fluxes in a leaching experiment with soil cores collected near (a) and away from (b) a snow fence and exposed to five different freezing-thawing treatments (Fig. 3), and a figure showing fluxes and concentrations of DOC and nutrients in soil water in a monolith transplant experiment between locations with either deep and persistent, or shallow and intermittent snow conditions near (deep snow; D) or away (shallow snow; S) from a snow fence.
Die vorliegende Arbeit ist die inhaltlich unverändert Fassung einer Dissertation, die 1998 der M... more Die vorliegende Arbeit ist die inhaltlich unverändert Fassung einer Dissertation, die 1998 der Mathematisch-Naturwissenschaftlichen Fakultà ¤ der Christian-Albrecht-Università ¤ zu Kiel
Die Rolle der fruhjahrlichen Schneebedeckung fur den Kohlenstoffhaushalt von Cetraria nivalis (L)... more Die Rolle der fruhjahrlichen Schneebedeckung fur den Kohlenstoffhaushalt von Cetraria nivalis (L) Ach. und Cetraria delisei (Bory) Th. Fr. an einem subarktisch-alpinen Standort.
Summary The Arctic is already experiencing changes in plant community composition, so understandi... more Summary The Arctic is already experiencing changes in plant community composition, so understanding the contribution of different vegetation components to carbon (C) cycling is essential in order to accurately quantify ecosystem C balance. Mosses contribute substantially to biomass, but their impact on carbon use efficiency (CUE) – the proportion of gross primary productivity (GPP) incorporated into growth – and aboveground versus belowground C partitioning is poorly known. We used 13C pulse‐labelling to trace assimilated C in mosses (Sphagnum sect. Acutifolia and Pleurozium schreberi) and in dwarf shrub–P. schreberi vegetation in sub‐Arctic Finland. Based on 13C pools and fluxes, we quantified the contribution of mosses to GPP, CUE and partitioning. Mosses incorporated 20 ± 9% of total ecosystem GPP into biomass. CUE of Sphagnum was 68–71%, that of P. schreberi was 62–81% and that of dwarf shrub–P. schreberi vegetation was 58–74%. Incorporation of C belowground was 10 ± 2% of GPP, while vascular plants alone incorporated 15 ± 4% of their fixed C belowground. We have demonstrated that mosses strongly influence C uptake and retention in Arctic dwarf shrub vegetation. They increase CUE, and the fraction of GPP partitioned aboveground. Arctic C models must include mosses to accurately represent ecosystem C dynamics.
ABSTRACT Spatial and temporal patterns of soil respiration rates and controlling factors were inv... more ABSTRACT Spatial and temporal patterns of soil respiration rates and controlling factors were investigated in three wet arctic tundra systems. In situ summer season carbon dioxide fluxes were measured across a range of micro-topographic positions in tussock tundra, wet sedge tundra, and low-centre polygonal tundra, at two different latitudes on the Taimyr Peninsular, central Siberia. Measurements were carried out by means of a multi-channel gas exchange system operating in continuous-flow mode.Measured soil respiration rates ranged from 0.1 g CO2-C m−2 d−1 to 3.9 g CO2-C m−2 d−1 and rate differences between neighbouring sites in the micro-topography (microsites) were larger than those observed between different tundra systems. Statistical analysis identified position of the water table and soil temperature at shallow depths to be common controls of soil respiration rates across all microsites, with each of these two factors explaining high proportions of the observed variations.Modelling of the response of soil respiration to soil temperature and water table for individual microsites revealed systematic differences in the response to the controlling factors between wet and drier microsites. Wet microsites – with a water table position close to the soil surface during most of the summer – showed large soil respiration rate changes with fluctuations of the water table compared to drier microsites. Wet microsites also showed consistently higher temperature sensitivity and a steeper increase of temperature sensitivity with decreasing temperatures than drier sites. Overall, Q10 values ranged from 1.2 to 3.4. The concept of substrate availability for determining temperature sensitivity is applied to reconcile these systematic differences. The results highlight that soil respiration rates in wet tundra are foremost controlled by water table and only secondarily by soil temperature. Wet sites have a larger potential for changes in soil respiration rates under changing environmental conditions, compared to drier sites.It is concluded that understanding and forecasting gaseous carbon losses from arctic tundra soils and its implication for ecosystem-scale CO2 fluxes and soil organic matter dynamics require good knowledge about temporal and spatial patterns of soil water conditions. The water status of tundra soils can serve as a control on the temperature sensitivity of soil respiration.
Tables showing geographical details and characterization of a soil profile at the Glas Maol study... more Tables showing geographical details and characterization of a soil profile at the Glas Maol study site, means and standard errors of mean (SE) of carbon and nutrient fluxes in a leaching experiment with soil cores collected near (a) and away from (b) a snow fence and exposed to five different freezing-thawing treatments (Fig. 3), and a figure showing fluxes and concentrations of DOC and nutrients in soil water in a monolith transplant experiment between locations with either deep and persistent, or shallow and intermittent snow conditions near (deep snow; D) or away (shallow snow; S) from a snow fence.
Die vorliegende Arbeit ist die inhaltlich unverändert Fassung einer Dissertation, die 1998 der M... more Die vorliegende Arbeit ist die inhaltlich unverändert Fassung einer Dissertation, die 1998 der Mathematisch-Naturwissenschaftlichen Fakultà ¤ der Christian-Albrecht-Università ¤ zu Kiel
Die Rolle der fruhjahrlichen Schneebedeckung fur den Kohlenstoffhaushalt von Cetraria nivalis (L)... more Die Rolle der fruhjahrlichen Schneebedeckung fur den Kohlenstoffhaushalt von Cetraria nivalis (L) Ach. und Cetraria delisei (Bory) Th. Fr. an einem subarktisch-alpinen Standort.
Summary The Arctic is already experiencing changes in plant community composition, so understandi... more Summary The Arctic is already experiencing changes in plant community composition, so understanding the contribution of different vegetation components to carbon (C) cycling is essential in order to accurately quantify ecosystem C balance. Mosses contribute substantially to biomass, but their impact on carbon use efficiency (CUE) – the proportion of gross primary productivity (GPP) incorporated into growth – and aboveground versus belowground C partitioning is poorly known. We used 13C pulse‐labelling to trace assimilated C in mosses (Sphagnum sect. Acutifolia and Pleurozium schreberi) and in dwarf shrub–P. schreberi vegetation in sub‐Arctic Finland. Based on 13C pools and fluxes, we quantified the contribution of mosses to GPP, CUE and partitioning. Mosses incorporated 20 ± 9% of total ecosystem GPP into biomass. CUE of Sphagnum was 68–71%, that of P. schreberi was 62–81% and that of dwarf shrub–P. schreberi vegetation was 58–74%. Incorporation of C belowground was 10 ± 2% of GPP, while vascular plants alone incorporated 15 ± 4% of their fixed C belowground. We have demonstrated that mosses strongly influence C uptake and retention in Arctic dwarf shrub vegetation. They increase CUE, and the fraction of GPP partitioned aboveground. Arctic C models must include mosses to accurately represent ecosystem C dynamics.
ABSTRACT Spatial and temporal patterns of soil respiration rates and controlling factors were inv... more ABSTRACT Spatial and temporal patterns of soil respiration rates and controlling factors were investigated in three wet arctic tundra systems. In situ summer season carbon dioxide fluxes were measured across a range of micro-topographic positions in tussock tundra, wet sedge tundra, and low-centre polygonal tundra, at two different latitudes on the Taimyr Peninsular, central Siberia. Measurements were carried out by means of a multi-channel gas exchange system operating in continuous-flow mode.Measured soil respiration rates ranged from 0.1 g CO2-C m−2 d−1 to 3.9 g CO2-C m−2 d−1 and rate differences between neighbouring sites in the micro-topography (microsites) were larger than those observed between different tundra systems. Statistical analysis identified position of the water table and soil temperature at shallow depths to be common controls of soil respiration rates across all microsites, with each of these two factors explaining high proportions of the observed variations.Modelling of the response of soil respiration to soil temperature and water table for individual microsites revealed systematic differences in the response to the controlling factors between wet and drier microsites. Wet microsites – with a water table position close to the soil surface during most of the summer – showed large soil respiration rate changes with fluctuations of the water table compared to drier microsites. Wet microsites also showed consistently higher temperature sensitivity and a steeper increase of temperature sensitivity with decreasing temperatures than drier sites. Overall, Q10 values ranged from 1.2 to 3.4. The concept of substrate availability for determining temperature sensitivity is applied to reconcile these systematic differences. The results highlight that soil respiration rates in wet tundra are foremost controlled by water table and only secondarily by soil temperature. Wet sites have a larger potential for changes in soil respiration rates under changing environmental conditions, compared to drier sites.It is concluded that understanding and forecasting gaseous carbon losses from arctic tundra soils and its implication for ecosystem-scale CO2 fluxes and soil organic matter dynamics require good knowledge about temporal and spatial patterns of soil water conditions. The water status of tundra soils can serve as a control on the temperature sensitivity of soil respiration.
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