Publikationen
Es wurden 18 Publikationen gefunden
Seibert, R.; Grünhage, L.; Müller, C.; Otte, A. & Donath, T.W. (2018): Raised atmospheric CO2 levels affect soil seed bank composition of temperate grasslands. Journal of Vegetation Science 30, 86-97
DOI: http://dx.doi.org/10.1111/jvs.12699.
Obermeier, W. (2017-07-04). Future summer aboveground biomass in a temperate C3 grassland. Presented at General Assembly - FACE2FACE, Giessen.
Seibert, R. (2015-10-01). Impacts of long-term atmospheric CO2 enrichment on the soil seed bank in a temperate grassland. Presented at 8th GGL Conference on Life Sciences, Gießen, Germany.
Klostermann, H.R.; Zinkernagel, J. & Kahlen, K. (2015): Geisenheim FACE for Vegetable Crops - Methodological Framework. Procedia Environmental Sciences 29, 106
DOI: http://dx.doi.org/doi:10.1016/j.proenv.2015.07.184.
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DOI: doi:10.1016/j.proenv.2015.07.184
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Abstract:
Abstract:
Future vegetable crop production might be affected by Climate Change with the projected increase in atmospheric CO2 concentration and changes in precipitation pattern. Elevated CO2 as one main component of photosynthesis is assumed to increase the yield of many crops while alleviating negative effects of drought stress and, thereby, increasing the water use efficiency. However, the responses of field grown vegetable crops to elevated CO2 are still unknown as previous findings are mainly derived from experiments conducted under controlled environments. In addition, the field vegetable production is characterized by several sets per season, varying growth conditions during the production periods and a high water demand usually provided by an irrigation system. Moreover, vegetable crops differ in the harvest organs, e.g. fruits, root tuber, bulbs or leaves, which are predominantly harvested in an early development stage. These vegetable-specific aspects have not been considered in past Free Air Carbon Dioxide Enrichment (FACE) experiments. Therefore, we aim at analyzing the short and long impacts of elevated CO2 with limited water supply on field vegetable crop productivity for three different crops (Cucumis sativus L., Raphanus sativus var. sativius L., Spinacia oleracea L.). Here, we present the methodological framework. Experiments will be conducted in the newly established FACE facility for vegetable crops at Geisenheim University, Germany. The facility is designed to raise the ambient CO2 concentration at the experimental field site by about 20% to approximately 480 ppm and to regulate the water supply with a drip irrigation system, resulting in a split plot design with three replications. In each replication an annual crop rotation with several production cycles of the three different vegetable crops are realized. Measurements of the CO2 and H2O gas exchange on leaf level as well as non-destructive and destructive recordings of plant growth and development are planned.
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Keywords: |
climate change |
elevated CO2 |
drought stress |
water use efficiency |
Brenzinger, K.; Kujala, K.; Horn, M.A.; Moser, G.; Guillet, C.; Kammann, C.; Müller, C. & Braker, G. (2017): Soil Conditions Rather Than Long-Term Exposure to Elevated CO2 Affect Soil Microbial Communities Associated with N-Cycling. Frontiers in Microbiology 8(1976), 1-14
DOI: http://dx.doi.org/10.3389/fmicb.2017.01976.
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DOI: 10.3389/fmicb.2017.01976
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Abstract:
Abstract:
Continuously rising atmospheric CO2 concentrations may lead to an increased transfer of organic C from plants to the soil through rhizodeposition and may affect the interaction between the C- and N-cycle. For instance, fumigation of soils with elevated CO2 (eCO2) concentrations (20% higher compared to current atmospheric concentrations) at the Giessen Free-Air Carbon Dioxide Enrichment (GiFACE) sites resulted in a more than two fold increase of long-term N2O emissions and an increase in dissimilatory reduction of nitrate compared to ambient CO2 (aCO2). We hypothesized that the observed differences in soil functioning were based on differences in the abundance and composition of microbial communities in general and especially of those which are responsible for N-transformations in soil. We also expected eCO2 effects on soil parameters, such as on nitrate as previously reported. To explore the impact of long-term eCO2 on soil microbial communities, we applied a molecular approach (qPCR, T-RFLP, and 454 pyrosequencing). Microbial groups were analyzed in soil of three sets of two FACE plots (three replicate samples from each plot), which were fumigated with eCO2 and aCO2, respectively. N-fixers, denitrifiers, archaeal and bacterial ammonia oxidizers, and dissimilatory nitrate reducers to ammonia were targeted by analysis of functional marker genes and the overall archaeal community by 16S rRNA genes. Remarkably, soil parameters as well as the abundance and composition of microbial communities in the top soil under eCO2 differed only slightly from soil under aCO2. Wherever differences in microbial community abundance and composition were detected, they were not linked to CO2 level but rather determined by differences in soil parameters (e.g. soil moisture content) due to the localization of the GiFACE sets in the experimental field. We concluded that +20% eCO2 had little to no effect on the overall microbial community involved in N-cycling in the soil but that spatial heterogeneity over extended periods had shaped microbial communities at particular sites in the field. Hence, microbial community composition and abundance alone cannot explain the functional differences leading to higher N2O emissions under eCO2 and future studies should aim at exploring the active members of the soil microbial community.
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Keywords: |
elevated CO2 |
N2O |
denitrifiers |
Ammonia Oxidizers |
N-fixers |
DNRA |
Free air carbon dioxide enrichment |
454 pyrosequencing |
Seibert, R. (2014-09-18). Population dynamics, phenology and yield of grassland. Presented at 7th GGL Conference on Life Sciences, Gießen.
Seibert, R. (2016-09-20). Impacts of long-term atmospheric CO2 enrichment on the species dynamics and aboveground biomass production of a periodically wet grassland. Presented at 9th GGL Conference on Life Sciences, Gießen, Germany.
Kellner, J. (2014-09-18). Development of a coupled hydrological-plant growth model for grasslands under elevated CO2. Presented at 7th GGL Conference on Life Sciences, Gießen, Germany.
Moser, G.; Gorenflo, A.; Brenzinger, K.; Keidel, L.; Braker, G.; Marhan, S.; Clough, T.J. & Müller, C. (2018): Explaining the doubling of N2O emissions under elevated CO2 in the Giessen FACE via in-field 15N tracing. Global Change Biology 24, 3897-3910
DOI: http://dx.doi.org/10.1111/gcb.14136.
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DOI: 10.1111/gcb.14136
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Abstract:
Abstract:
Rising atmospheric CO2 concentrations are expected to increase nitrous oxide (N2O)
emissions from soils via changes in microbial nitrogen (N) transformations. Several
studies have shown that N2O emission increases under elevated atmospheric CO2
(eCO2), but the underlying processes are not yet fully understood. Here, we present
results showing changes in soil N transformation dynamics from the Giessen Free Air
CO2 Enrichment (GiFACE): a permanent grassland that has been exposed to eCO2,
+20% relative to ambient concentrations (aCO2), for 15 years. We applied in the field
an ammonium-nitrate fertilizer solution, in which either ammonium (NHþ
4 ) or nitrate
(NO
3 ) was labelled with 15N. The simultaneous gross N transformation rates were
analysed with a 15N tracing model and a solver method. The results confirmed that
after 15 years of eCO2 the N2O emissions under eCO2 were still more than twofold
higher than under aCO2. The tracing model results indicated that plant uptake of NHþ
4
did not differ between treatments, but uptake of NO
3 was significantly reduced under
eCO2. However, the NHþ
4 and NO
3 availability increased slightly under eCO2. The
N2O isotopic signature indicated that under eCO2 the sources of the additional emissions,
8,407 lg N2O–N/m2 during the first 58 days after labelling, were associated
with NO
3 reduction (+2.0%), NHþ
4 oxidation (+11.1%) and organic N oxidation
(+86.9%). We presume that increased plant growth and root exudation under eCO2
provided an additional source of bioavailable supply of energy that triggered as a priming
effect the stimulation of microbial soil organic matter (SOM) mineralization and
fostered the activity of the bacterial nitrite reductase. The resulting increase in incomplete
denitrification and therefore an increased N2O:N2 emission ratio, explains the
doubling of N2O emissions. If this occurs over a wide area of grasslands in the future,
this positive feedback reaction may significantly accelerate climate change.
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Keywords: |
climate change |
elevated CO2 |
grassland |
free air carbon dioxide enrichment |
long-term response |
N transformation |
N2O emission |
positive climate change feedback |
Moser, G.; Gorenflo, A.; Brenzinger, K.; Keidel, L.; Braker, G.; Marhan, S.; Clough, T.J. & Müller, C. (2018): Explaining the doubling of N2O emissions under elevated CO2 in the Giessen FACE via in-field 15N tracing. Global Change Biology early view, 1-14
DOI: http://dx.doi.org/10.1111/gcb.14136 | Revised: 12 January 2018.
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DOI: 10.1111/gcb.14136 | Revised: 12 January 2018
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Abstract:
Abstract:
Rising atmospheric CO2 concentrations are expected to increase nitrous oxide (N2O) emissions from soils via changes in microbial nitrogen (N) transformations triggering a positive feedback reaction that could accelerate climate change. Several studies have shown N2O emission increases under elevated atmospheric CO2 (eCO2), but the underlying processes are not yet fully understood. Here we present results showing changes in soil N transformation dynamics from the Giessen Free Air CO2 Enrichment (GiFACE): a permanent grassland that has been exposed to eCO2, +20% relative to ambient concentrations (aCO2), for 15 years. We applied in the field an ammonium-nitrate fertilizer solution, in which either ammonium (NH4+) or nitrate (NO3-) was labelled with 15N. The simultaneous gross N transformation rates were analysed with a 15N tracing model and a solver method. The results confirmed that after 15 years of eCO2 the N2O emissions under eCO2 were still more than 2-fold higher than under aCO2. The tracing model results indicated that plant uptake of NH4+ did not differ between treatments, but uptake of NO3- was significantly reduced under eCO2. However, the ratio of gross production and consumption of NH4+ remained unchanged under eCO2, but decreased slightly for NO3-, which increased NO3- availability under eCO2. The N2O isotopic signature indicated that under eCO2 the sources of the additional emissions, 8407 µg N2O-N m-2 during the first 58 days after labelling, were associated with NO3- reduction (+2.0%), NH4+ oxidation (+11.1%) and organic N oxidation (+86.9%). We presume that increased root exudation under eCO2 provided an additional source of bioavailable supply of energy that triggered the stimulation of microbial soil organic matter (SOM) mineralization, as a priming effect, and an increased activity of bacterial nitrite reductase, which caused the shift in N2O:N2 emission ratio, via incomplete denitrification, explaining the positive feedback reaction of doubled N2O emissions.
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Keywords: |
climate change |
elevated CO2 |
grassland |
Giessen-FACE |
Giessen FACE |
Gi-FACE |
Gross N transformation |
free air carbon dioxide enrichment |
long-term response |
N transformation |
N2O emission |
positive climate change feedback |
Keidel, L.; Kammann, C.; Grünhage, L.; Moser, G. & Müller, C. (2015): Long term CO2 enrichment in a temperate grassland increases soil respiration during late autumn and winter. Biogeoscience 12, 1257-1269
DOI: http://dx.doi.org/10.5194/bg-12-1257-2015.
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DOI: 10.5194/bg-12-1257-2015
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Abstract:
Abstract:
Soil respiration of terrestrial ecosystems, a major component in the global carbon cycle is affected by elevated atmospheric CO2 concentrations. However, seasonal differences of feedback effects of elevated CO2 have rarely been studied. At the Gießen Free-Air CO2 Enrichment (GiFACE) site, the effects of +20% above ambient CO2 concentration have been investigated since 1998 in a temperate grassland ecosystem. We defined five distinct annual seasons, with respect to management practices and phenological cycles. For a period of 3 years (2008–2010), weekly measurements of soil respiration were carried out with a survey chamber on vegetation-free subplots. The results revealed a pronounced and repeated increase of soil respiration under elevated CO2 during late autumn and winter dormancy. Increased CO2 losses during the autumn season (September–October) were 15.7% higher and during the winter season (November–March) were 17.4% higher compared to respiration from ambient CO2 plots.
However, during spring time and summer, which are characterized by strong above- and below-ground plant growth, no significant change in soil respiration was observed at the GiFACE site under elevated CO2. This suggests (1) that soil respiration measurements, carried out only during the growing season under elevated CO2 may underestimate the true soil-respiratory CO2 loss (i.e. overestimate the C sequestered), and (2) that additional C assimilated by plants during the growing season and transferred below-ground will quickly be lost via enhanced heterotrophic respiration outside the main growing season.
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Keywords: |
temperature |
soil |
aCO2 |
climate change |
elevated CO2 |
FACE |
soil respiration |
grassland |
Kellner, J. (2016-09-21). Simulating the effect of elevated CO2 on plant growth of a temperate grassland using a coupled hydrological-plant growth model. Presented at 9th GGL Conference on Life Sciences, Gießen, Germany.
Kellner, J.; Multsch, S.; Kraft, P.; Houska, T.; Müller, C. & Breuer, L. (2016-02-15). Uncertainty analysis of a coupled hydrological-plant growth model for grassland under elevated CO2. Presented at Agriculture and Climate Change - Adapting Crops to Increased Uncertainty (AGRI 2015), Amsterdam.
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Abstract:
Abstract:
The continuous increase in atmospheric carbon dioxide (CO2) contributes to changes in plant evapotranspiration and terrestrial water Budgets in two ways. Firstly, elevated CO2 can result in a water saving effect, since increasing CO2 reduces stomatal opening and therefore decreases transpiration. Secondly, CO2 fertilization increases biomass accumulation and leaf area at plant canopy Level, likely increasing plant transpiration. Vegetation and hydrological models can be used to investigate the CO2 Response and the bidirectional effects outlined above, including their relative contribution to the changes in the water cycle. However, the intrinsic plant-soil interaction and the uncertainty related to model parameterization have rarely been considered.
Hence, we coupled a detailed plant growth and soil hydrological model by using the generic model frameworks Plant growth Modelling Framework (PMF) and Catchment Modelling Framework (CMF). Up to date response mechanisms have been implemented in PMF to simulate the various ways of how plant physiology is influenced by elevated CO2. Both models interact by using the Python computer language. Applying the coupled PMF-CMF model we investigate the effects of elevated CO2 in a number of plant physiological and environmental variables such as biomass, leaf area index and soil moisture using field data of a long-term Free Air Carbon dioxide Enrichment (FACE) Experiment in Giessen, Germany. In this Experiment, various grassland varieties (herbs, legumes, grasses) grow under elevated (+20%) and ambient CO2 since 1997.
A Monte Carlo based uncertainty analysis (GLUE) is conducted to investigate the coupled PMF-CMF parameter space. The focus will be on the identification of parameters for plant and soil, which are the drivers for the CO2 Response of the terrestrial water balance. We will present first results of the simulation of biomass accumulation and transpiration under ambient and elevated CO2 concentrations.
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Keywords: |
elevated CO2 |
grassland |
plant growth |
uncertainty analysis |
coupled model |
water balance |
Kellner, J. (2015-10-01). Modelling temperate grasslands under elevated CO2 with a coupled hydrological-plant growth model. Presented at 8th GGL Conference on Life Sciences, Gießen, Germany.
Seibert, R. (2017-03-28). Impacts of 19 years long atmospheric CO2 enrichment on aboveground biomass production and population dynamics of a periodically wet grassland. Presented at 2nd Agriculture and Climate Change Conference - Climate ready resource use-efficient crops to sustai, Sitges, Spain.
Seibert, R. (2017-07-04). Populationsdynamik, Phänologie und Ertrag im Grünland. Presented at FACE2FACE-Vollversammlung, Gießen.
Obermeier, W.; Lehnert, L.W.; Ivanov, M.; Luterbacher, J. & Bendix, J. (2018): Reduced summer aboveground productivity in temperate C3 grasslands under future climate regimes. Earth's Future 6, 1-14
DOI: http://dx.doi.org/10.1029/2018EF000833.
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DOI: 10.1029/2018EF000833
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Abstract:
Abstract:
Temperate grasslands play globally an important role, for example, for biodiversity conservation, livestock forage production, and carbon storage. The latter two are primarily controlled by biomass
production, which is assumed to decrease with lower amounts and higher variability of precipitation, while increasing air temperature might either foster or suppress biomass production. Additionally, a higher atmospheric CO2 concentration ([CO2]) is supposed to increase biomass productivity either by directly
stimulating photosynthesis or indirectly by inducing water savings (CO2 fertilization effect). Consequently, future biomass productivity is controlled by the partially contrasting effects of changing climatic conditions and [CO2], which to date are only marginally understood. This results in high uncertainties of future
biomass production and carbon storage estimates. Consequently, this study aims at statistically estimating mid-21st century grassland aboveground biomass (AGB) based on 18 years of data (1998–2015) from a free air carbon enrichment experiment. We found that lower precipitation totals and a higher precipitation variability
reduced AGB. Under drier conditions accompanied by increasing air temperature, AGB further decreased. Here AGB under elevated [CO2] was partly even lower compared to AGB under ambient [CO2], probably because elevated [CO2] reduced evaporative cooling of plants, increasing heat stress. This indicates a higher susceptibility
of AGB to increased air temperature under future atmospheric [CO2]. Since climate models for Central Europe project increasing air temperature and decreasing total summer precipitation associated with an increasing variability, our results suggest that grassland summer AGB will be reduced in the future, contradicting the widely expected positive yield anomalies from increasing [CO2].
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Keywords: |
biomass |
climate change |
elevated CO2 |
FACE |
precipitation |
warming |