Leon van der Linden - Academia.edu (original) (raw)
Papers by Leon van der Linden
Environmental Science & Technology, 2005
This study investigated the relative behavior of pathogens, fecal indicator organisms, and partic... more This study investigated the relative behavior of pathogens, fecal indicator organisms, and particles of varying size during transport through a reservoir following a storm event inflow in Myponga Reservoir, South Australia. During the inflow, samples were collected from the river and at various locations within the reservoir to determine the fate and transport of microroganisms as they progressed through the water body. Microbiological analysis included the indicator organisms Escherichia coli, enterococci, Clostridium perfringens, aerobic spores, and somatic coliphages, the protozoan pathogens Cryptosporidium spp. and Giardia spp., and the potential physical surrogates of pathogen contamination including particle size and turbidity. Of the microbial indicator groups, C. perfringens spores were the most highly correlated with Cryptosporidium spp. concentrations (Spearman Rho ) 0.58), closely followed by enterococci (Spearman Rho ) 0.57). Cryptosporidium spp. oocysts were predominantly associated with small sized particles (range of 14.3-27.7 µm). All of the microbial indicator groups tested were associated with larger sized particle ranges (>63.3 µm) except C. perfringens spores which were associated with particles in the size range of 45.5-63.3 µm. Although indicators may rank correlate with Cryptosporidium spp., the variation in settling rates of different microorganisms has significant implications for the use of surrogates to estimate pathogen attenuation within reservoirs. For example, concentrations of Cryptosporidium spp. oocysts were reduced by a factor of 3 on reaching the dam wall, whereas enterococci were reduced by a factor of 10.
Environmental Science & Technology, 2014
S afe drinking water is a fundamental human right. 1 However, the water industry faces unpreceden... more S afe drinking water is a fundamental human right. 1 However, the water industry faces unprecedented demand for drinking water globally as it simultaneously manages climate change and increasing human population. 2 Water utilities will increasingly have to respond to an increased frequency of extreme events (e.g., droughts, floods, fires, storms), altered nutrient loading from catchments, and water quality deterioration. 3 Traditionally, water supplies have been dominated by surface-and ground-water sources; however, yield from these sources is likely to become less reliable, concurrent with rising demand. Investment in alternative water resources is inevitable but exposes utilities to new water quality risks. The water industry thus faces an emerging challenge of how to manage the risks of these threats and make necessary investments to ensure the reliability of future supply.
![Research paper thumbnail of Response to multi-generational selection under elevated [CO2] in two temperature regimes suggests enhanced carbon assimilation and increased reproductive output in Brassica napus L](https://attachments.academia-assets.com/49970594/thumbnails/1.jpg)
](Ecology and evolution, 2013
Functional plant traits are likely to adapt under the sustained pressure imposed by environmental... more Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO 2 ] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO 2 ] and temperature conditions, a full-factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO 2 ] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO 2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO 2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO 2 ] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co-occur.
Functional Ecology, 2007
Recent findings indicate that the interactions among CO 2 , temperature and water can be substant... more Recent findings indicate that the interactions among CO 2 , temperature and water can be substantial, and that the combined effects on the biological systems of several factors may not be predicted from experiments with one or a few factors. Therefore realistic multifactorial experiments involving a larger set of main factors are needed. 2. We describe a new Danish climate change-related field scale experiment, CLIMAITE, in a heath/ grassland ecosystem. CLIMAITE is a full factorial combination of elevated CO 2 , elevated temperature and prolonged summer drought. The manipulations are intended to mimic anticipated major environmental changes at the site by year 2075 as closely as possible. The impacts on ecosystem processes and functioning (at ecophysiological levels, through responses by individuals and communities to ecosystem-level responses) are investigated simultaneously. 3. The increase of [CO 2 ] closely corresponds with the scenarios for year 2075, while the warming treatment is at the lower end of the predictions and seems to be the most difficult treatment to increase without unwanted side effects on the other variables. The drought treatment follows predictions of increased frequency of drought periods in summer. The combination of the treatments does not create new unwanted side effects on the treatments relative to the treatments alone.
Water, 2015
Surface water quality has been identified as potentially vulnerable to climate change. This study... more Surface water quality has been identified as potentially vulnerable to climate change. This study assesses the impacts of climate change on the water quality of Hsinshan Reservoir, Taiwan, through CE-QUAL-W2 simulations. The model parameters were calibrated by field data collected during 2004-2008, and verified against observations made during 2009-2012. The projected temperature and precipitation data for the near-and long-term future were downscaled to regional and daily scales, and used to simulate the projected changes in water quality through the validated model. The simulation results were reported as probability-based cumulative distribution functions to access the impacts of climate change on water quality. The results indicated that the intensified thermal stratification caused by the rising temperature is the primary driver of water quality decline, which increases the probability of deep-layer oxygen depletion and the flux of limiting nutrients for algae growth, resulting in a higher risk of algal blooms and eutrophication. The adaptation strategies of multilevel-intake operations and increasing bottom-layer dissolved oxygen without destratification are recommended.
Water, 2015
Surface water quality has been identified as potentially vulnerable to climate change. This study... more Surface water quality has been identified as potentially vulnerable to climate change. This study assesses the impacts of climate change on the water quality of Hsinshan Reservoir, Taiwan, through CE-QUAL-W2 simulations. The model parameters were calibrated by field data collected during 2004-2008, and verified against observations made during 2009-2012. The projected temperature and precipitation data for the near-and long-term future were downscaled to regional and daily scales, and used to simulate the projected changes in water quality through the validated model. The simulation results were reported as probability-based cumulative distribution functions to access the impacts of climate change on water quality. The results indicated that the intensified thermal stratification caused by the rising temperature is the primary driver of water quality decline, which increases the probability of deep-layer oxygen depletion and the flux of limiting nutrients for algae growth, resulting in a higher risk of algal blooms and eutrophication. The adaptation strategies of multilevel-intake operations and increasing bottom-layer dissolved oxygen without destratification are recommended.
IOP Conference Series: Earth and Environmental Science, 2009
This innovative new feature generates a list of articles' also read'by other users base... more This innovative new feature generates a list of articles' also read'by other users based on them reading the original article. Article abstracts citations and references are all considered and weighted accordingly. We hope that this will help you find relevant papers for your ...
IOP Conference Series: Earth and Environmental Science, 2009
... Leon Linden(1), C Beier(1), TN Mikkelsen(1), M Holmstrup(3), IK Schmidt(4), P Ambus(1), K Pil... more ... Leon Linden(1), C Beier(1), TN Mikkelsen(1), M Holmstrup(3), IK Schmidt(4), P Ambus(1), K Pilegaard(1), KR Albert(2), LC Andresen(2), MB Selsted(1), KS Larsen(1), A Ibrom(1) (1) Biosystems Division, Risø-DTU, Roskilde, Denmark. ...
Assimilation of data from several measurements provides knowledge of the model's performa... more Assimilation of data from several measurements provides knowledge of the model's performance and uncertainties. In this work we investigate the complementary of Biomass data to net CO2 flux (NEE) and latent heat flux (LE) in optimising parameters of the biogeochemical model ORCHIDEE. Our optimisation method is a gradient based iterative method. We optimized the model at the French forest sites,
ABSTRACT The ecosystem carbon balance is affected by both external climatic forcing (e.g. solar r... more ABSTRACT The ecosystem carbon balance is affected by both external climatic forcing (e.g. solar radiation, air temperature and humidity) and internal dynamics in the ecosystem functional properties (e.g. canopy structure, leaf photosynthetic capacity and carbohydrate reserve). In order to understand to what extent and at which temporal scale, climatic variability and functional changes regulated the interannual variation (IAV) in the net ecosystem exchange of CO2 (NEE), data-driven analysis and semi-empirical modelling (Lasslop et al. 2010) were performed based on a 13 year NEE record in a temperate deciduous forest (Pilegaard et al 2011, Wu et al. 2012). We found that the sensitivity of carbon fluxes to climatic variability was significantly higher at shorter than at longer time scales and changed seasonally. This implied that the changing distribution of climate anomalies during the vegetation period could have stronger impacts on future ecosystem carbon balances than changes in average climate. At the annual time scale, approximately 80% of the interannual variability in NEE was attributed to the variation in the model parameters, indicating the observed IAV in the carbon dynamics at the investigated site was dominated by changes in ecosystem functioning. In general this study showed the need for understanding the mechanisms of ecosystem functional change. The method can be applied at other sites to explore ecosystem behavior across different plant functional types and climate gradients. Incorporating ecosystem functional change into process based models will reduce the uncertainties in long-term predictions of ecosystem carbon balances in global climate change projections. Acknowledgements. This work was supported by the EU FP7 project CARBO-Extreme, the DTU Climate Centre and the Danish national project ECOCLIM (Danish Council for Strategic Research).
ABSTRACT In ecosystem manipulation experiments (EMEs) the ecosystem is artificially exposed to di... more ABSTRACT In ecosystem manipulation experiments (EMEs) the ecosystem is artificially exposed to different environmental conditions that aim to simulate circumstances in future climate. At Danish EME site Brandbjerg the responses of a heathland to drought, warming and increased atmospheric CO2 concentration are studied. The warming manipulation is realized by passive nighttime warming. The measurements include control plots as well as replicates for each three treatment separately and in combination. The Brandbjerg heathland ecosystem is dominated by heather and wavy hairgrass. These experiments provide excellent data for validation and development of ecosystem models. In this work we used a generic vegetation model ORCHIDEE with Model-Data-Fusion (MDF) approach. ORCHIDEE model is a process-based model that describes the exchanges of carbon, water and energy between the atmosphere and the vegetation. It can be run at different spatial scales from global to site level. Different vegetation types are described in ORCHIDEE as plant functional types. In MDF we are using observations from the site to optimize the model parameters. This enables us to assess the modelling errors and the performance of the model for different manipulation treatments. This insight will inform us whether the different processes are adequately modelled or if the model is missing some important processes. We used a genetic algorithm in the MDF. The data available from the site included measurements of aboveground biomass, heterotrophic soil respiration and total ecosystem respiration from years 2006-2008. The biomass was measured six times doing this period. The respiration measurements were done with manual chamber measurements. For the soil respiration we used results from an empirical model that has been developed for the site. This enabled us to have more data for the MDF. Before the MDF we performed a sensitivity analysis of the model parameters to different data streams. Fifteen most influential parameters were chosen to be optimized. These included parameters connected to photosynthesis, phenology, allocation of biomass and respiration. All three data streams were used simultaneously in the MDF. Before the MDF, the model had the tendency to overestimate the respiration and the aboveground biomass. After MDF the model simulations were closer to the observations, but its estimations for those variables that were not used in the MDF, such as, e.g., fine root biomass growth, did not improve greatly. In these runs the vegetation of Brandbjerg site was described in ORCHIDEE as C3 grass, which had some characteristics that do not apply to a Danish heathland very well. The results suggest that a new plant functional type needs to be developed to ORCHIDEE in order to successfully simulate such ecosystem as Brandbjerg.
Current predictions indicate that, unless greenhouse gas emissions are significantly curtailed, a... more Current predictions indicate that, unless greenhouse gas emissions are significantly curtailed, atmospheric CO2 concentrations will double during the present century inducing an additional 1.4 to 5.8oC increase in mean global temperature, alterations in global and regional precipitation patterns, and increase the frequency and magnitude of severe weather events (e.g. droughts and floods). Such changes will have strong effects on the
Encyclopedia of Earth Sciences Series, 2012
Soil Biology & Biochemistry, 2010
The potential impacts of interactions of multiple climate change factors in soil ecosystems have ... more The potential impacts of interactions of multiple climate change factors in soil ecosystems have received little attention. Most studies have addressed effects of single factors such as increased temperature or atmospheric CO 2 but little is known about how such environmental ...
![Research paper thumbnail of Response to multi-generational selection under elevated [CO2] in two temperature regimes suggests enhanced carbon assimilation and increased reproductive output in Brassica napus L](https://attachments.academia-assets.com/42719721/thumbnails/1.jpg)
](Ecology and Evolution, 2013
Functional plant traits are likely to adapt under the sustained pressure imposed by environmental... more Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO 2 ] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO 2 ] and temperature conditions, a full-factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO 2 ] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO 2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO 2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO 2 ] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co-occur.
Water, 2015
ABSTRACT The application of downscaled climate scenarios can be used to inform management decisio... more ABSTRACT The application of downscaled climate scenarios can be used to inform management decisions on investment in water treatment infrastructure or alternative water sources. Appropriate models of the system components potentially impacted by climate change such as catchments, rivers, lakes and reservoirs are required. The sensitivity of the coupled hydrodynamic water quality model ELCOM-CAEDYM to climate drivers was investigated to determine its suitability for evaluating climate change impacts and to evaluate the most important climatic drivers. A case study application of the model to Happy Valley Reservoir was used in the investigation (Romero et al. 2005). The hydrodynamic model was validated against field measurements without calibration. The ecological model was set up using values derived from literature sources and measurements made at other reservoirs. Manual calibration of some parameters was performed, however, performance metrics were not provided by Romero et al. (2005). A series of simulations were run with altered boundary condition inputs for the reservoir. Air and inflowing water temperature (TEMP), wind speed (WIND) and reservoir inflow and outflow (FLOW) were altered to investigate the sensitivity of these key drivers over relevant domains. The simulated water quality variables responded in the broadly expected manner to the altered boundary conditions; sensitivity of the simulated cyanobacteria population to increases in temperature was similar to published values. This study demonstrated that ELCOM-CAEDYM is sensitive to climate drivers and suitable for use in climate impact studies. It further highlighted the important factors in determining phytoplankton growth and that any changes in inflowing water quality will be of major importance to the dynamics of raw water quality.
Water Resources Management, 2010
Large tributary inflows into water supply reservoirs caused by heavy catchment rain may be of con... more Large tributary inflows into water supply reservoirs caused by heavy catchment rain may be of concern due to problems associated with high levels of natural organic matter (NOM) present in the inflows. The movement of these inflows within a reservoir is dependent on its relative density to the receiving waters. For example, if the inflow is denser (colder) than the recipient water it will travel along the base of the reservoir as an underflow and can penetrate as far as the dam wall water off-take to a water treatment plant (WTP). Field studies were conducted to track the passage of underflows through two South Australian reservoirs, Little Para and Myponga. Samples were collected before and during storm event inflows and analyses undertaken to determine NOM concentration, alum demand, disinfection by-product formation potential, and quality of the water. We demonstrate that by monitoring the movement of inflows into reservoirs, combined with changes in reservoir off-take levels, that the risk of NOM entering a water treatment plant can be reduced which in turn will lower water treatment costs by reducing alum dosing levels and lessen the risk to human health by reducing disinfection by-product formation.
Soil Biology and Biochemistry, 2011
In temperate regions, climate change is predicted to increase annual mean temperature and intensi... more In temperate regions, climate change is predicted to increase annual mean temperature and intensify the duration and frequency of summer droughts, which together with elevated atmospheric carbon dioxide (CO 2 ) concentrations, may affect the exchange of nitrous oxide (N 2 O) and methane (CH 4 ) between terrestrial ecosystems and the atmosphere. We report results from the CLIMAITE experiment, where the effects of these three climate change parameters were investigated solely and in all combinations in a temperate heathland. Field measurements of N 2 O and CH 4 fluxes took place 1e2 years after the climate change manipulations were initiated. The soil was generally a net sink for atmospheric CH 4 . Elevated temperature (T) increased the CH 4 uptake by on average 10 mg C m À2 h À1 , corresponding to a rise in the uptake rate of about 20%. However, during winter elevated CO 2 (CO 2 ) reduced the CH 4 uptake, which outweighed the positive effect of warming when analyzed across the study period. Emissions of N 2 O were generally low (<10 mg N m À2 h À1 ). As single experimental factors, elevated CO 2 , temperature and summer drought (D) had no major effect on the N 2 O fluxes, but the combination of CO 2 and warming (TCO 2 ) stimulated N 2 O emission, whereas the N 2 O emission ceased when CO 2 was combined with drought (DCO 2 ). We suggest that these N 2 O responses are related to increased rhizodeposition under elevated CO 2 combined with increased and reduced nitrogen turnover rates caused by warming and drought, respectively. The N 2 O flux in the multifactor treatment TDCO 2 was not different from the ambient control treatment. Overall, our study suggests that in the future, CH 4 uptake may increase slightly, while N 2 O emission will remain unchanged in temperate ecosystems on well-aerated soils. However, we propose that continued exposure to altered climate could potentially change the greenhouse gas flux pattern in the investigated heathland.
Plant, Cell & Environment, 2011
Page 1. Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a tempera... more Page 1. Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water statuspce_2320 1..16 KR ALBERT1, H. RO-POULSEN2, TN MIKKELSEN1 ...
Environmental Science & Technology, 2005
This study investigated the relative behavior of pathogens, fecal indicator organisms, and partic... more This study investigated the relative behavior of pathogens, fecal indicator organisms, and particles of varying size during transport through a reservoir following a storm event inflow in Myponga Reservoir, South Australia. During the inflow, samples were collected from the river and at various locations within the reservoir to determine the fate and transport of microroganisms as they progressed through the water body. Microbiological analysis included the indicator organisms Escherichia coli, enterococci, Clostridium perfringens, aerobic spores, and somatic coliphages, the protozoan pathogens Cryptosporidium spp. and Giardia spp., and the potential physical surrogates of pathogen contamination including particle size and turbidity. Of the microbial indicator groups, C. perfringens spores were the most highly correlated with Cryptosporidium spp. concentrations (Spearman Rho ) 0.58), closely followed by enterococci (Spearman Rho ) 0.57). Cryptosporidium spp. oocysts were predominantly associated with small sized particles (range of 14.3-27.7 µm). All of the microbial indicator groups tested were associated with larger sized particle ranges (>63.3 µm) except C. perfringens spores which were associated with particles in the size range of 45.5-63.3 µm. Although indicators may rank correlate with Cryptosporidium spp., the variation in settling rates of different microorganisms has significant implications for the use of surrogates to estimate pathogen attenuation within reservoirs. For example, concentrations of Cryptosporidium spp. oocysts were reduced by a factor of 3 on reaching the dam wall, whereas enterococci were reduced by a factor of 10.
Environmental Science & Technology, 2014
S afe drinking water is a fundamental human right. 1 However, the water industry faces unpreceden... more S afe drinking water is a fundamental human right. 1 However, the water industry faces unprecedented demand for drinking water globally as it simultaneously manages climate change and increasing human population. 2 Water utilities will increasingly have to respond to an increased frequency of extreme events (e.g., droughts, floods, fires, storms), altered nutrient loading from catchments, and water quality deterioration. 3 Traditionally, water supplies have been dominated by surface-and ground-water sources; however, yield from these sources is likely to become less reliable, concurrent with rising demand. Investment in alternative water resources is inevitable but exposes utilities to new water quality risks. The water industry thus faces an emerging challenge of how to manage the risks of these threats and make necessary investments to ensure the reliability of future supply.
Ecology and evolution, 2013
Functional plant traits are likely to adapt under the sustained pressure imposed by environmental... more Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO 2 ] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO 2 ] and temperature conditions, a full-factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO 2 ] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO 2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO 2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO 2 ] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co-occur.
Functional Ecology, 2007
Recent findings indicate that the interactions among CO 2 , temperature and water can be substant... more Recent findings indicate that the interactions among CO 2 , temperature and water can be substantial, and that the combined effects on the biological systems of several factors may not be predicted from experiments with one or a few factors. Therefore realistic multifactorial experiments involving a larger set of main factors are needed. 2. We describe a new Danish climate change-related field scale experiment, CLIMAITE, in a heath/ grassland ecosystem. CLIMAITE is a full factorial combination of elevated CO 2 , elevated temperature and prolonged summer drought. The manipulations are intended to mimic anticipated major environmental changes at the site by year 2075 as closely as possible. The impacts on ecosystem processes and functioning (at ecophysiological levels, through responses by individuals and communities to ecosystem-level responses) are investigated simultaneously. 3. The increase of [CO 2 ] closely corresponds with the scenarios for year 2075, while the warming treatment is at the lower end of the predictions and seems to be the most difficult treatment to increase without unwanted side effects on the other variables. The drought treatment follows predictions of increased frequency of drought periods in summer. The combination of the treatments does not create new unwanted side effects on the treatments relative to the treatments alone.
Water, 2015
Surface water quality has been identified as potentially vulnerable to climate change. This study... more Surface water quality has been identified as potentially vulnerable to climate change. This study assesses the impacts of climate change on the water quality of Hsinshan Reservoir, Taiwan, through CE-QUAL-W2 simulations. The model parameters were calibrated by field data collected during 2004-2008, and verified against observations made during 2009-2012. The projected temperature and precipitation data for the near-and long-term future were downscaled to regional and daily scales, and used to simulate the projected changes in water quality through the validated model. The simulation results were reported as probability-based cumulative distribution functions to access the impacts of climate change on water quality. The results indicated that the intensified thermal stratification caused by the rising temperature is the primary driver of water quality decline, which increases the probability of deep-layer oxygen depletion and the flux of limiting nutrients for algae growth, resulting in a higher risk of algal blooms and eutrophication. The adaptation strategies of multilevel-intake operations and increasing bottom-layer dissolved oxygen without destratification are recommended.
Water, 2015
Surface water quality has been identified as potentially vulnerable to climate change. This study... more Surface water quality has been identified as potentially vulnerable to climate change. This study assesses the impacts of climate change on the water quality of Hsinshan Reservoir, Taiwan, through CE-QUAL-W2 simulations. The model parameters were calibrated by field data collected during 2004-2008, and verified against observations made during 2009-2012. The projected temperature and precipitation data for the near-and long-term future were downscaled to regional and daily scales, and used to simulate the projected changes in water quality through the validated model. The simulation results were reported as probability-based cumulative distribution functions to access the impacts of climate change on water quality. The results indicated that the intensified thermal stratification caused by the rising temperature is the primary driver of water quality decline, which increases the probability of deep-layer oxygen depletion and the flux of limiting nutrients for algae growth, resulting in a higher risk of algal blooms and eutrophication. The adaptation strategies of multilevel-intake operations and increasing bottom-layer dissolved oxygen without destratification are recommended.
IOP Conference Series: Earth and Environmental Science, 2009
This innovative new feature generates a list of articles' also read'by other users base... more This innovative new feature generates a list of articles' also read'by other users based on them reading the original article. Article abstracts citations and references are all considered and weighted accordingly. We hope that this will help you find relevant papers for your ...
IOP Conference Series: Earth and Environmental Science, 2009
... Leon Linden(1), C Beier(1), TN Mikkelsen(1), M Holmstrup(3), IK Schmidt(4), P Ambus(1), K Pil... more ... Leon Linden(1), C Beier(1), TN Mikkelsen(1), M Holmstrup(3), IK Schmidt(4), P Ambus(1), K Pilegaard(1), KR Albert(2), LC Andresen(2), MB Selsted(1), KS Larsen(1), A Ibrom(1) (1) Biosystems Division, Risø-DTU, Roskilde, Denmark. ...
Assimilation of data from several measurements provides knowledge of the model's performa... more Assimilation of data from several measurements provides knowledge of the model's performance and uncertainties. In this work we investigate the complementary of Biomass data to net CO2 flux (NEE) and latent heat flux (LE) in optimising parameters of the biogeochemical model ORCHIDEE. Our optimisation method is a gradient based iterative method. We optimized the model at the French forest sites,
ABSTRACT The ecosystem carbon balance is affected by both external climatic forcing (e.g. solar r... more ABSTRACT The ecosystem carbon balance is affected by both external climatic forcing (e.g. solar radiation, air temperature and humidity) and internal dynamics in the ecosystem functional properties (e.g. canopy structure, leaf photosynthetic capacity and carbohydrate reserve). In order to understand to what extent and at which temporal scale, climatic variability and functional changes regulated the interannual variation (IAV) in the net ecosystem exchange of CO2 (NEE), data-driven analysis and semi-empirical modelling (Lasslop et al. 2010) were performed based on a 13 year NEE record in a temperate deciduous forest (Pilegaard et al 2011, Wu et al. 2012). We found that the sensitivity of carbon fluxes to climatic variability was significantly higher at shorter than at longer time scales and changed seasonally. This implied that the changing distribution of climate anomalies during the vegetation period could have stronger impacts on future ecosystem carbon balances than changes in average climate. At the annual time scale, approximately 80% of the interannual variability in NEE was attributed to the variation in the model parameters, indicating the observed IAV in the carbon dynamics at the investigated site was dominated by changes in ecosystem functioning. In general this study showed the need for understanding the mechanisms of ecosystem functional change. The method can be applied at other sites to explore ecosystem behavior across different plant functional types and climate gradients. Incorporating ecosystem functional change into process based models will reduce the uncertainties in long-term predictions of ecosystem carbon balances in global climate change projections. Acknowledgements. This work was supported by the EU FP7 project CARBO-Extreme, the DTU Climate Centre and the Danish national project ECOCLIM (Danish Council for Strategic Research).
ABSTRACT In ecosystem manipulation experiments (EMEs) the ecosystem is artificially exposed to di... more ABSTRACT In ecosystem manipulation experiments (EMEs) the ecosystem is artificially exposed to different environmental conditions that aim to simulate circumstances in future climate. At Danish EME site Brandbjerg the responses of a heathland to drought, warming and increased atmospheric CO2 concentration are studied. The warming manipulation is realized by passive nighttime warming. The measurements include control plots as well as replicates for each three treatment separately and in combination. The Brandbjerg heathland ecosystem is dominated by heather and wavy hairgrass. These experiments provide excellent data for validation and development of ecosystem models. In this work we used a generic vegetation model ORCHIDEE with Model-Data-Fusion (MDF) approach. ORCHIDEE model is a process-based model that describes the exchanges of carbon, water and energy between the atmosphere and the vegetation. It can be run at different spatial scales from global to site level. Different vegetation types are described in ORCHIDEE as plant functional types. In MDF we are using observations from the site to optimize the model parameters. This enables us to assess the modelling errors and the performance of the model for different manipulation treatments. This insight will inform us whether the different processes are adequately modelled or if the model is missing some important processes. We used a genetic algorithm in the MDF. The data available from the site included measurements of aboveground biomass, heterotrophic soil respiration and total ecosystem respiration from years 2006-2008. The biomass was measured six times doing this period. The respiration measurements were done with manual chamber measurements. For the soil respiration we used results from an empirical model that has been developed for the site. This enabled us to have more data for the MDF. Before the MDF we performed a sensitivity analysis of the model parameters to different data streams. Fifteen most influential parameters were chosen to be optimized. These included parameters connected to photosynthesis, phenology, allocation of biomass and respiration. All three data streams were used simultaneously in the MDF. Before the MDF, the model had the tendency to overestimate the respiration and the aboveground biomass. After MDF the model simulations were closer to the observations, but its estimations for those variables that were not used in the MDF, such as, e.g., fine root biomass growth, did not improve greatly. In these runs the vegetation of Brandbjerg site was described in ORCHIDEE as C3 grass, which had some characteristics that do not apply to a Danish heathland very well. The results suggest that a new plant functional type needs to be developed to ORCHIDEE in order to successfully simulate such ecosystem as Brandbjerg.
Current predictions indicate that, unless greenhouse gas emissions are significantly curtailed, a... more Current predictions indicate that, unless greenhouse gas emissions are significantly curtailed, atmospheric CO2 concentrations will double during the present century inducing an additional 1.4 to 5.8oC increase in mean global temperature, alterations in global and regional precipitation patterns, and increase the frequency and magnitude of severe weather events (e.g. droughts and floods). Such changes will have strong effects on the
Encyclopedia of Earth Sciences Series, 2012
Soil Biology & Biochemistry, 2010
The potential impacts of interactions of multiple climate change factors in soil ecosystems have ... more The potential impacts of interactions of multiple climate change factors in soil ecosystems have received little attention. Most studies have addressed effects of single factors such as increased temperature or atmospheric CO 2 but little is known about how such environmental ...
Ecology and Evolution, 2013
Functional plant traits are likely to adapt under the sustained pressure imposed by environmental... more Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO 2 ] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO 2 ] and temperature conditions, a full-factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO 2 ] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO 2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO 2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO 2 ] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co-occur.
Water, 2015
ABSTRACT The application of downscaled climate scenarios can be used to inform management decisio... more ABSTRACT The application of downscaled climate scenarios can be used to inform management decisions on investment in water treatment infrastructure or alternative water sources. Appropriate models of the system components potentially impacted by climate change such as catchments, rivers, lakes and reservoirs are required. The sensitivity of the coupled hydrodynamic water quality model ELCOM-CAEDYM to climate drivers was investigated to determine its suitability for evaluating climate change impacts and to evaluate the most important climatic drivers. A case study application of the model to Happy Valley Reservoir was used in the investigation (Romero et al. 2005). The hydrodynamic model was validated against field measurements without calibration. The ecological model was set up using values derived from literature sources and measurements made at other reservoirs. Manual calibration of some parameters was performed, however, performance metrics were not provided by Romero et al. (2005). A series of simulations were run with altered boundary condition inputs for the reservoir. Air and inflowing water temperature (TEMP), wind speed (WIND) and reservoir inflow and outflow (FLOW) were altered to investigate the sensitivity of these key drivers over relevant domains. The simulated water quality variables responded in the broadly expected manner to the altered boundary conditions; sensitivity of the simulated cyanobacteria population to increases in temperature was similar to published values. This study demonstrated that ELCOM-CAEDYM is sensitive to climate drivers and suitable for use in climate impact studies. It further highlighted the important factors in determining phytoplankton growth and that any changes in inflowing water quality will be of major importance to the dynamics of raw water quality.
Water Resources Management, 2010
Large tributary inflows into water supply reservoirs caused by heavy catchment rain may be of con... more Large tributary inflows into water supply reservoirs caused by heavy catchment rain may be of concern due to problems associated with high levels of natural organic matter (NOM) present in the inflows. The movement of these inflows within a reservoir is dependent on its relative density to the receiving waters. For example, if the inflow is denser (colder) than the recipient water it will travel along the base of the reservoir as an underflow and can penetrate as far as the dam wall water off-take to a water treatment plant (WTP). Field studies were conducted to track the passage of underflows through two South Australian reservoirs, Little Para and Myponga. Samples were collected before and during storm event inflows and analyses undertaken to determine NOM concentration, alum demand, disinfection by-product formation potential, and quality of the water. We demonstrate that by monitoring the movement of inflows into reservoirs, combined with changes in reservoir off-take levels, that the risk of NOM entering a water treatment plant can be reduced which in turn will lower water treatment costs by reducing alum dosing levels and lessen the risk to human health by reducing disinfection by-product formation.
Soil Biology and Biochemistry, 2011
In temperate regions, climate change is predicted to increase annual mean temperature and intensi... more In temperate regions, climate change is predicted to increase annual mean temperature and intensify the duration and frequency of summer droughts, which together with elevated atmospheric carbon dioxide (CO 2 ) concentrations, may affect the exchange of nitrous oxide (N 2 O) and methane (CH 4 ) between terrestrial ecosystems and the atmosphere. We report results from the CLIMAITE experiment, where the effects of these three climate change parameters were investigated solely and in all combinations in a temperate heathland. Field measurements of N 2 O and CH 4 fluxes took place 1e2 years after the climate change manipulations were initiated. The soil was generally a net sink for atmospheric CH 4 . Elevated temperature (T) increased the CH 4 uptake by on average 10 mg C m À2 h À1 , corresponding to a rise in the uptake rate of about 20%. However, during winter elevated CO 2 (CO 2 ) reduced the CH 4 uptake, which outweighed the positive effect of warming when analyzed across the study period. Emissions of N 2 O were generally low (<10 mg N m À2 h À1 ). As single experimental factors, elevated CO 2 , temperature and summer drought (D) had no major effect on the N 2 O fluxes, but the combination of CO 2 and warming (TCO 2 ) stimulated N 2 O emission, whereas the N 2 O emission ceased when CO 2 was combined with drought (DCO 2 ). We suggest that these N 2 O responses are related to increased rhizodeposition under elevated CO 2 combined with increased and reduced nitrogen turnover rates caused by warming and drought, respectively. The N 2 O flux in the multifactor treatment TDCO 2 was not different from the ambient control treatment. Overall, our study suggests that in the future, CH 4 uptake may increase slightly, while N 2 O emission will remain unchanged in temperate ecosystems on well-aerated soils. However, we propose that continued exposure to altered climate could potentially change the greenhouse gas flux pattern in the investigated heathland.
Plant, Cell & Environment, 2011
Page 1. Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a tempera... more Page 1. Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water statuspce_2320 1..16 KR ALBERT1, H. RO-POULSEN2, TN MIKKELSEN1 ...