Summer drought conditions promote the dominant role of phytoplankton in riverine nutrient dynamics

2020 ◽  
Author(s):  
Norbert Kamjunke ◽  
Michael Rode ◽  
Martina Baborowski ◽  
Vanessa Kunz ◽  
Oliver Lechtenfeld ◽  
...  
Keyword(s):  
Nutrient Uptake ◽  
Nutrient Dynamics ◽  
Chlorophyll Concentration ◽  
Global Radiation ◽  
Particulate Phosphorus ◽  
Summer Drought ◽  
Minor Importance ◽  
River Elbe ◽  
Nutrient Turnover ◽  
Drought Conditions

<p>Large rivers play a relevant role in the nutrient turnover from land to ocean. Here, highly dynamic planktonic processes are more important compared to streams making it necessary to link the dynamics of nutrient turnover to control mechanisms of phytoplankton. We investigated the basic conditions leading to high phytoplankton biomass and corresponding nutrient dynamics in the eutrophic River Elbe (Germany). In a first step, we performed six Lagrangian samplings in the lower river part at different hydrological conditions. While nutrient concentration remained high at low algal densities in autumn and at moderate discharge in summer, high algal concentrations occurred at low discharge in summer. Under these conditions, concentrations of silica and nitrate decreased and rates of nitrate assimilation were high. Soluble reactive phosphorus was depleted and particulate phosphorus increased inversely. Rising molar C:P ratios of seston indicated a phosphorus limitation of phytoplankton. Global radiation combined with discharge had a strong predictive power to explain maximum chlorophyll concentration. In a second step, we estimated nutrient turnover exemplarily for N during the campaign with the lowest discharge. Mass balance calculations revealed a total nitrate uptake of 455 mg N m<sup>-2</sup>d<sup>-1</sup> which was clearly dominated by assimilatory phytoplankton uptake whereas denitrification and other benthic processes were only of minor importance. Phytoplankton density, which showed a sigmoidal longitudinal development, dominantly explained gross primary production, related assimilatory nutrient uptake and respiration. Chlorophyll a concentration and bacterial abundance affected the composition of dissolved organic matter and were positively related to a number of CHO and CHNO components with high H/C and low O/C ratios but negatively to several CHOS surfactants. In conclusion, nutrient uptake in the large river strongly depends on the growth conditions for phytoplankton, which are favored during summer drought conditions.</p>

Soil supply and nutrient demand (SSAND): A general nutrient uptake model and an example of its application to forest management

2006 ◽  
Vol 86 (4) ◽  
pp. 655-673 ◽  
Author(s):  
N B Comerford ◽  
W P Cropper, Jr. ◽  
Hua Li ◽  
P J Smethurst ◽  
K. C.J. Van Rees ◽  
...  
Keyword(s):  
Climate Change ◽  
Nutrient Uptake ◽  
Nutrient Dynamics ◽  
Nutrient Management ◽  
Plant Root ◽  
Phosphorus Uptake ◽  
Soil Nutrient ◽  
Nutrient Bioavailability ◽  
Nutrient Demand ◽  
Mycorrhizal Hyphae

Models of soil nutrient bioavailability and uptake assist in nutrient management and lead to a better understanding of nutrient dynamics in the soil-plant system. SSAND (Soil Supply and Nutrient Demand) is a steady state, mechanistic nutrient uptake simulation model based on mass flow and diffusive supply of nutrients to roots. It requires user inputs for soil and plant parameters to calculate a nutrient’s concentration at the root surface and the subsequent uptake by a plant root and/or extrametrical mycorrhizal hyphae. It can be considered a sub-model linked to hydrological or plant growth models. SSAND provides a basis for simulating nutrient uptake under different soil-plant scenarios, including multiple soil compartments, net mineralization inputs, changing root growth, changing mycorrhizal hyphae growth, changing soil water content and multiple fertilizer events. It incorporates uptake from roots and mycorrhizal hyphae, including the potential competition between these entities. It should be useful for simulating the effects of climate change on soil nutrient bioavailability. It should also be a useful tool for managers in evaluating fertilizer regime options. Key words: Nutrient bioavailability, nutrient uptake modeling, phosphorus uptake, mycorrhizae, Spodosols, climate change

scholarly journals Conceptual Mini-Catchment Typologies for Testing Dominant Controls of Nutrient Dynamics in Three Nordic Countries

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1776 ◽  
Author(s):  
Fatemeh Hashemi ◽  
Ina Pohle ◽  
Johannes W.M. Pullens ◽  
Henrik Tornbjerg ◽  
Katarina Kyllmar ◽  
...  
Keyword(s):  
Land Use ◽  
Nutrient Dynamics ◽  
Pollution Monitoring ◽  
Organic N ◽  
Particulate Phosphorus ◽  
Nutrient Concentrations ◽  
Data Series ◽  
Nutrient Export ◽  
Small Streams ◽  
Export Behaviour

Optimal nutrient pollution monitoring and management in catchments requires an in-depth understanding of spatial and temporal factors controlling nutrient dynamics. Such an understanding can potentially be obtained by analysing stream concentration–discharge (C-Q) relationships for hysteresis behaviours and export regimes. Here, a classification scheme including nine different C-Q types was applied to a total of 87 Nordic streams draining mini-catchments (0.1–65 km2). The classification applied is based on a combination of stream export behaviour (dilution, constant, enrichment) and hysteresis rotational pattern (clock-wise, no rotation, anti-clockwise). The scheme has been applied to an 8-year data series (2010–2017) from small streams in Denmark, Sweden, and Finland on daily discharge and discrete nutrient concentrations, including nitrate (NO3−), total organic N (TON), dissolved reactive phosphorus (DRP), and particulate phosphorus (PP). The dominant nutrient export regimes were enrichment for NO3− and constant for TON, DRP, and PP. Nutrient hysteresis patterns were primarily clockwise or no hysteresis. Similarities in types of C-Q relationships were investigated using Principal Component Analysis (PCA) considering effects of catchment size, land use, climate, and dominant soil type. The PCA analysis revealed that land use and air temperature were the dominant factors controlling nutrient C-Q types. Therefore, the nutrient export behaviour in streams draining Nordic mini-catchments seems to be dominantly controlled by their land use characteristics and, to a lesser extent, their climate.

Monitoring and predicting the outstanding 2017 drought in Spain

2020 ◽  
Author(s):  
Miguel Ángel Torres Vázquez ◽  
Amar Halifa Marín ◽  
Juan Pedro Montávez ◽  
Marco Turco
Keyword(s):  
Standardized Precipitation Index ◽  
Warning System ◽  
Empirical Method ◽  
Environmental Research ◽  
Drought Risk ◽  
Summer Drought ◽  
Drought Event ◽  
Streamflow Prediction ◽  
Drought Prediction ◽  
Drought Conditions

<p>The increase in societal exposure and vulnerability to drought, call to move from post-crisis to pre-impact drought risk management. Accurate and timely information of evolving drought conditions is crucial to take early actions to avoid devastating long-term impacts. A previous study indicated that a statistical empirical method, the ensemble streamflow prediction system (ESP; an ensemble based on reordering historical data), represents a computationally fast alternative to dynamical prediction applications for drought prediction (Turco et al. 2017). Extending this work, here we present an assessment of the ability of the ESP method in predicting the drought of 2017 in Spain considering also the uncertainties coming from the observations. For this, four different datasets are used: that cover a period of 36 years (1981-2017) and with a spatial resolution of 0.25 x 0.25º based on observations of interpolated stations (E-OBS, AEMET), on reanalysis data (ERA5), and on combining stations and satellite data (CHIRPS). Meteorological droughts are defined using the Standardized Precipitation Index aggregated over the months April–September. All the datasets show a similar spatial pattern, with most of the domain suffering extreme drought conditions. In addition, the ESP system achieves reasonable skill in predicting this drought event 2 months in advance with, again, similar pattern among the different datasets. These results suggest the feasibility of the development of an operational early warning system, also considering that the data of CHIRPS and ERA5 are updated every month, i.e., that are available for near-real time applications.</p><p> </p><p>References</p><p>Turco, M., et al. (2017). Summer drought predictability over Europe: empirical versus dynamical forecasts. Environmental Research Letters, 12(8), 084006.</p><p> </p><p>Acknowledgments</p><p>The authors acknowledge the ACEX project (CGL2017-87921-R) of the Ministerio de Economía y Competitividad of Spain. AHM thanks his predoctoral contract FPU18/00824 to the Ministerio de Ciencia, Innovación y Universidades of Spain. M.T. has received funding from the Spanish Ministry of Science, Innovation and Universities through the project PREDFIRE (RTI2018-099711-J-I00).</p>

scholarly journals Trends and extremes of drought indices throughout the 20th century in the Mediterranean

2011 ◽  
Vol 11 (1) ◽  
pp. 33-51 ◽  
Author(s):  
P. M. Sousa ◽  
R. M. Trigo ◽  
P. Aizpurua ◽  
R. Nieto ◽  
L. Gimeno ◽  
...  
Keyword(s):  
20Th Century ◽  
Extreme Values ◽  
Statistical Significance ◽  
Drought Indices ◽  
Summer Drought ◽  
Monthly Precipitation ◽  
Central Mediterranean ◽  
Annual Variability ◽  
Drought Conditions ◽  
The Mediterranean

Abstract. Average monthly precipitation, the original Palmer Drought Severity Index (PDSI) and a recent adaptation to Europe, the Self Calibrated PDSI (scPDSI) have been used here to analyse the spatial and temporal evolution of drought conditions in the Mediterranean during the 20th century. Monthly, seasonal and annual trends were computed for the period 1901–2000 and also for the first and second halves of this period. The statistical significance of trends was obtained with a modified version of the Mann-Kendall test that accounts for serial auto-correlation. The results show a clear trend towards drier conditions during the 20th century in most western and central Mediterranean regions, with the exceptions of northwestern Iberia and most of Turkey that reveal an increase of moisture availability. A Generalized Extreme Values (GEV) analysis was applied to the maximum and minimum regional values of scPDSI, with results pointing towards a significant decline of absolute extreme values in central areas (Italy and Balkans) and a less clear picture emerging in western (Iberia) and eastern (Turkey) realms. The inter-annual variability of the scPDSI index series is shown to be more realistic than the corresponding PDSI version, fitting better the drought episodes sequence and magnitude described in the literature for each sub-region. We assess the decadal and inter-annual variability of the scPDSI for each sub-domain and evaluate the role played by the major teleconnection patterns, and by several sea surface temperature (SST) anomalies. The main driver of scPDSI in western and central Mediterranean areas is the winter North Atlantic Oscillation (NAO) pattern that is also relevant during the following spring and summer seasons with anti-correlation values below −0.60. The second most important mode corresponds to the Scandinavian Pattern that is significantly associated to the scPDSI between winter and summer over central Mediterranean (correlation values around 0.50). Finally, the teleconnection and SST analysis has allowed us to calibrate a stepwise regression model, enabling the forecasting of summer drought conditions six months in advance. The final model obtained is capable of reproducing the observed scPDSI time series fairly well, with a correlation coefficient of 0.79 (0.77 after cross-validation) and a significant gain over climatology (SSc=59%), while the corresponding result against persistence is more modest (SSp6=11%).

scholarly journals The European 2015 drought from a climatological perspective

2017 ◽  
Vol 21 (3) ◽  
pp. 1397-1419 ◽  
Author(s):  
Monica Ionita ◽  
Lena M. Tallaksen ◽  
Daniel G. Kingston ◽  
James H. Stagge ◽  
Gregor Laaha ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Geopotential Height ◽  
Western Europe ◽  
North Atlantic Ocean ◽  
Western Mediterranean ◽  
Daily Maximum ◽  
Summer Drought ◽  
Drought Conditions ◽  
The Mediterranean

Abstract. The summer drought of 2015 affected a large portion of continental Europe and was one of the most severe droughts in the region since summer 2003. The summer of 2015 was characterized by exceptionally high temperatures in many parts of central and eastern Europe, with daily maximum temperatures 2 °C higher than the seasonal mean (1971–2000) over most of western Europe, and more than 3 °C higher in the east. It was the hottest and climatologically driest summer over the 1950–2015 study period for an area stretching from the eastern Czech Republic to Ukraine. For Europe, as a whole, it is among the six hottest and driest summers since 1950. High evapotranspiration rates combined with a lack of precipitation affected soil moisture and vegetation and led to record low river flows in several major rivers, even beyond the drought-hit region. The 2015 drought developed rather rapidly over the Iberian Peninsula, France, southern Benelux and central Germany in May and reached peak intensity and spatial extent by August, affecting especially the eastern part of Europe. Over the summer period, there were four heat wave episodes, all associated with persistent blocking events. Upper-level atmospheric circulation over Europe was characterized by positive 500 hPa geopotential height anomalies flanked by a large negative anomaly to the north and west (i.e., over the central North Atlantic Ocean extending to northern Fennoscandia) and another center of positive geopotential height anomalies over Greenland and northern Canada. Simultaneously, the summer sea surface temperatures (SSTs) were characterized by large negative anomalies in the central North Atlantic Ocean and large positive anomalies in the Mediterranean basin. Composite analysis shows that the western Mediterranean SST is strongly related to the occurrence of dry and hot summers over the last 66 years (especially over the eastern part of Europe). The lagged relationship between the Mediterranean SST and summer drought conditions established in this study can provide valuable skill for the prediction of drought conditions over Europe on interannual to decadal timescales.

scholarly journals Estimating Return Intervals for Extreme Climate Conditions Related to Winter Disasters and Livestock Mortality in Mongolia

2021 ◽  
Author(s):  
Masahiko Haraguchi ◽  
Nicole Davi ◽  
Mukund Rao ◽  
Caroline Leland ◽  
Masataka Watanabe ◽  
...  
Keyword(s):  
Minimum Temperature ◽  
Drought Severity ◽  
Summer Drought ◽  
Early 19Th Century ◽  
Climate Conditions ◽  
Winter Conditions ◽  
Return Levels ◽  
Drought Conditions ◽  
Winter Minimum Temperature ◽  
Winter Severity

Abstract. Mass livestock mortality events during severe winters, a phenomenon that Mongolians call dzud, cause the country significant socioeconomic problems. Dzud is an example of a compound event, meaning that multiple climatic and social drivers contribute to the risk of occurrence. Existing studies argue that the frequency and intensity of dzud are rising due to the combined effects of climate change and variability, most notably summer drought and severe winter conditions, on top of socioeconomic dynamics such as overgrazing. Summer droughts are a precondition for dzud because scarce grasses cause malnutrition, which in turn makes livestock more vulnerable to harsh winter conditions. However, these studies typically look at a short time frame (i.e., after 1940); few have investigated either the risk or the recurrence of dzud over a century-scale climate record. This study aims to fill the gaps in technical knowledge about the recurrence probability of dzud by estimating the return levels of relevant climatic variables: summer drought conditions and winter minimum temperature. We divide the country into three regions (Northwest, Southwest, and East Mongolia) based on the mortality index at the soum (county) level. For droughts, our study uses as a proxy the tree-ring reconstructed Palmer Drought Severity Index (PDSI) for three regions between 1700–2013. For winter severity, our study uses observational data of winter minimum temperature after 1901 while inferring winter minimum temperature in Mongolia from instrumental data in Siberia that extends to the early 19th century. The Generalized Extreme Value (i.e., the statistical method to infer the probability of very rare or extreme events) shows that the return levels of drought conditions are changing over time, with variability increasing for all the regions. Winter severity, however, is constant. The median 100-year return levels of the winter minimum temperature in Mongolia have been, over the past 300 years, −26.08 °C for the Southwest, −27.99 °C for the Northwest, and −25.31 °C for the East. This study thus suggests that continued summer drought would lead to increased vulnerability and malnutrition. Here, we link meteorological characteristics to socioeconomic impacts related to livestock populations and draws attention to the need for livestock index insurance.

scholarly journals QTL mapping of seedling tolerance to exposure to low temperature in the maize IBM RIL population

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254437
Author(s):  
Raeann Goering ◽  
Siri Larsen ◽  
Jia Tan ◽  
James Whelan ◽  
Irina Makarevitch
Keyword(s):  
Stress Response ◽  
Low Temperature ◽  
Cold Stress ◽  
Recombinant Inbred ◽  
Chlorophyll Concentration ◽  
Seedling Stage ◽  
Chromosome 1 ◽  
Summer Drought ◽  
Temperature Exposure ◽  
Low Temperature Exposure

Maize is a cold sensitive crop that exhibits severe retardation of growth and development when exposed to cold spells during and right after germination, including the slowdown in development of new leaves and in formation of the photosynthetic apparatus. Improving cold tolerance in maize would allow early sowing to improve crop yield by prolonging a growing season and by decreasing the negative effects of summer drought, diseases, and pests. Two maize inbreds widely incorporated into American maize germplasm, B73 and Mo17, exhibit different levels of tolerance to low temperature exposure at seedling stage. In addition, thirty seven diverse inbred maize lines showed large variation for seedling response to low temperature exposure with lines with extremely low tolerance to seedling exposure to low temperatures falling into stiff stalk, non-stiff stalk, and tropical clades. We employed the maize intermated B73×Mo17 (IBM) recombinant inbred line population (IBM Syn4 RIL) to investigate the genetic architecture of cold stress tolerance at a young seedling stage and to identify quantitative trait loci (QTLs) controlling this variation. A panel of 97 recombinant inbred lines of IBM Syn4 were used to measure, and score based on several traits related to chlorophyll concentration, leaf color, and tissue damage. Our analysis resulted in detection of two QTLs with high additive impact, one on chromosome 1 (bin 1.02) and second on chromosome 5 (bin 5.05). Further investigation of the QTL regions using gene expression data provided a list of the candidate genes likely contributing to the variation in cold stress response. Among the genes located within QTL regions identified in this study and differentially expressed in response to low temperature exposure are the genes with putative functions related to auxin and gibberellin response, as well as general abiotic stress response, and genes coding for proteins with broad regulatory functions.

scholarly journals Anthropogenic and Climate-Exacerbated Landscape Disturbances Converge to Alter Phosphorus Bioavailability in an Oligotrophic River

2021 ◽  
Author(s):  
Caitlin Watt ◽  
Monica B Emelko ◽  
Uldis Silins ◽  
Adrian L Collins ◽  
Micheal Stone
Keyword(s):  
Water Quality ◽  
Nutrient Dynamics ◽  
Municipal Wastewater ◽  
Major Elements ◽  
Low Flow ◽  
Particulate Phosphorus ◽  
Landscape Disturbance ◽  
Land Disturbance ◽  
River Bed ◽  
Study Sites

Cumulative effects of landscape disturbance in forested source water regions can alter the storage of fine sediment and associated phosphorus in riverbeds, shift nutrient dynamics and degrade water quality. Here, we examine longitudinal changes in major element chemistry and particulate phosphorus (PP) fractions of river-bed sediment in an oligotrophic river during environmentally sensitive low flow conditions. Study sites along 50 km of the Crowsnest River were located below tributary inflows from sub-watersheds and represent a gradient of increasing cumulative sedi-ment pressures across a range of land disturbance types (harvesting, wildfire, and municipal wastewater discharges). Major elements (Si2O, Al2O3, Fe2O3, MnO, CaO, MgO, Na2O, K2O, Ti2O, V2O5, P2O5), loss on ignition (LOI), PP fractions (NH4CI-RP, BD-RP, NaOH-RP, HCI-RP and NaOH(85)-RP) and absolute particle size were evaluated for sediments collected in 2016 and 2017. While total PP concentrations were similar across all sites, bioavailable PP fractions (BD-RP, NaOH-RP) increased downstream with increased concentrations of Al2O3 and MnO and levels of landscape disturbance. This study highlights the longitudinal water quality impacts of increasing landscape disturbance on bioavailable PP in fine riverbed sediments and shows how the convergence of climate (wildfire) and anthropogenic (sewage effluent, harvesting, agriculture) drivers can produce legacy effects on nutrients.

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