Evaluating the effect of the 2018 drought on the NEE in the Sorø beech forest by means of trend analysis and mechanistic canopy modelling of GPP.

2020 ◽  
Author(s):  
Kim Pilegaard ◽  
Andreas Ibrom
Keyword(s):  
Water Content ◽  
Linear Trend ◽  
Heavy Rain ◽  
Beech Forest ◽  
Seasonal Development ◽  
Severe Drought ◽  
Summer Drought ◽  
Co2 Uptake ◽  
Data Set ◽  
Flux Data

<p>Denmark experienced a severe drought in 2018 lasting from the beginning of May to the end of August with very little rain during this period. The influence of drought on the net ecosystem CO<sub>2</sub> exchange (NEE) was analysed at the Danish ICOS DK-Soroe site (a mature beech forest). The site has a very long continuous flux data set starting in June 1996. The annual NEE of the site has been increasing over the years, mainly due to a prolonged growing season in the autumn and CO<sub>2</sub> fertilisation (Pilegaard et al., 2011).</p><p>The effect of the summer drought in 2018 was analysed by means of linear trend estimation based on monthly trends during 1996-2017. The observed monthly NEE in 2018 was compared to the predicted values from the monthly time series.</p><p>The analysis showed an increased NEE in May and June and a strongly reduced NEE in July and August. Overall, the NEE was reduced 25% compared to the predicted value.</p><p>The increased NEE in May and June can be explained by the benefit for the photosynthesis of the trees of the increased light and temperature, while there was still a sufficient water content in the soil. By the end of June, the low water content in the soil affected the NEE, and despite some heavy rain in the beginning of August, the NEE only recovered by September.</p><p>We used the flux data set together with a mechanistic canopy model to examine the tree physiological nature of the photosynthesis limitation. The results showed that stomatal limitation alone was not able to explain the large reduction of GPP during the drought. Based on these findings, we extended the approach and show the seasonal development of drought induced GPP limitation contrasting stomatal and biochemical photosynthesis limitations.</p><p>The effects on NEE and energy partitioning during the 2018 summer drought are compared to previous years with (less severe) summer drought. </p><p>Reference:</p><p>Kim Pilegaard, Andreas Ibrom, Michael S. Courtney, Poul Hummelshøj, Niels Otto Jensen. Increasing net CO2 uptake by a Danish beech forest during the period from 1996 to 2009. Agricultural and Forest Meteorology 151 (2011) 934–946.</p><p>Acknowledgement:</p><p>The study was based on data from ICOS/DK.</p>

scholarly journals Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999)

2011 ◽  
Vol 30 ◽  
pp. 11-16 ◽  
Author(s):  
A. C. Costa
Keyword(s):  
Temporal Dynamics ◽  
Linear Trend ◽  
Precipitation Index ◽  
Geostatistical Simulation ◽  
Severe Drought ◽  
Standard Precipitation Index ◽  
Data Set ◽  
Spatial Homogeneity ◽  
Study Region ◽  
Geostatistical Approach

Abstract. This paper analyzes the yearly changes in precipitation from 1940 to 1999 on local and regional scales over the southern region of continental Portugal, which has large areas threatened by desertification. The Standard Precipitation Index (SPI) time series with the 12-month time scale is calculated for 43 meteorological stations. A geostatistical approach is used to evaluate the temporal dynamics of the spatial patterns of precipitation. The spatial homogeneity of the SPI is evaluated for each decade. Afterwards, a geostatistical simulation algorithm (direct sequential simulation) is used to produce 100 equiprobable maps of the SPI for each year. This gridded data set (6000 maps with 800 m × 800 m grid cells) is then used to produce yearly scenarios of the SPI from 1940 to 1999, and uncertainty evaluations of the produced scenarios. The linear trend of SPI values over the sixty years period is calculated at each grid cell of the scenarios' maps using a nonparametric estimator. Wilcoxon-Mann-Whitney one-sided tests are used to compare the local median of the SPI in 1940/1969 with its median in 1970/1999. Results show that moderate drought conditions occur frequently over the study region, except in the northwest coast. Severe drought frequency patterns are found in areas of the centre and southeast regions. A significant trend towards drying occurs in the centre region and in the northeast. Considering the amount of water consumption and irrigation already required in some municipalities, water shortage due to drought is a viable threat in most of the Alentejo region if those local trends persist.

scholarly journals Cavitation Limits the Recovery of Gas Exchange after Severe Drought Stress in Holm Oak (Quercus ilex L.)

Forests ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 443 ◽  
Author(s):  
José Peguero-Pina ◽  
Óscar Mendoza-Herrer ◽  
Eustaquio Gil-Pelegrín ◽  
Domingo Sancho-Knapik
Keyword(s):  
Drought Stress ◽  
Quercus Ilex ◽  
Stomatal Closure ◽  
Maximum Velocity ◽  
Holm Oak ◽  
Severe Drought ◽  
Summer Drought ◽  
Co2 Uptake ◽  
Partial Recovery ◽  
Xylem Embolism

Holm oak (Quercus ilex L.) is a Mediterranean species that can withstand intense summer drought through a high resistance to cavitation far beyond the stomatal closure. Besides stomatal limitations, both mesophyll and biochemical limitations to CO2 uptake could increase in holm oak under drought. However, no studies have addressed how hydraulic and non-hydraulic factors may limit the recovery of photosynthesis when re-watering after inducing 50% loss of hydraulic conductivity. We measured photosynthetic traits, xylem embolism, and abscisic acid (ABA) in holm oak with increasing levels of drought stress and seven days after plant re-watering. Drought stress caused a sharp decrease in net CO2 assimilation (AN), stomatal and mesophyll conductance (gs and gm), and maximum velocity of carboxylation (Vcmax). The stomatal closure could be mediated by the rapid increase found in ABA. The high level of xylem embolism explained the strong down-regulation of gs even after re-watering. Therefore, only a partial recovery of AN was observed, in spite of non-hydraulic factors not limiting the recovery of AN, because i/ABA strongly decreased after re-watering, and ii/gm and Vcmax recovered their original values. Therefore, the hydraulic-stomatal limitation model would be involved in the partial recovery of AN, in order to prevent extensive xylem embolism under subsequent drought events that could compromise holm oak survival.

scholarly journals Analysis of floodplain forest sensitivity to drought

2020 ◽  
Vol 375 (1810) ◽  
pp. 20190518
Author(s):  
Natalia Kowalska ◽  
Ladislav Šigut ◽  
Marko Stojanović ◽  
Milan Fischer ◽  
Ina Kyselova ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Gross Primary Production ◽  
Floodplain Forest ◽  
Severe Drought ◽  
Summer Drought ◽  
Negative Effects ◽  
Eddy Covariance Method ◽  
Continental Scale

Floodplain forests are very complex, productive ecosystems, capable of storing huge amounts of soil carbon. With the increasing occurrence of extreme events, they are today among the most threatened ecosystems. Our study's main goal was to assess the productivity of a floodplain forest located at Lanžhot in the Czech Republic from two perspectives: carbon uptake (using an eddy covariance method) and stem radius variations (using dendrometers). We aimed to determine which conditions allow for high ecosystem production and what role drought plays in reducing such production potential. Additionally, we were interested to determine the relative soil water content threshold indicating the onset and duration of this event. We hypothesized that summer drought in 2018 had the most significant negative effects on the overall annual carbon and water budgets. In contrast with our original hypothesis, we found that an exceptionally warm spring in 2018 caused a positive gross primary production (GPP) and evapotranspiration (ET) anomaly that consequently led in 2018 to the highest seasonal total GPP and ET from all of the investigated years (2015–2018). The results showed ring-porous species to be the most drought resistant. Relative soil water content threshold of approximately 0.45 was determined as indicating the onset of drought stress. This article is part of the theme issue ‘Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale’.

scholarly journals Mapping the Spatial-Temporal Dynamics of Vegetation Response Lag to Drought in a Semi-Arid Region

2019 ◽  
Vol 11 (16) ◽  
pp. 1873 ◽  
Author(s):  
Li Hua ◽  
Huidong Wang ◽  
Haigang Sui ◽  
Brian Wardlow ◽  
Michael J. Hayes ◽  
...  
Keyword(s):  
Vegetation Index ◽  
Temporal Dynamics ◽  
Risk Mitigation ◽  
Scientific Information ◽  
Gaussian Function ◽  
Drought Risk ◽  
Severe Drought ◽  
Similar Response ◽  
Vegetation Types ◽  
Data Set

Drought, as an extreme climate event, affects the ecological environment for vegetation and agricultural production. Studies of the vegetative response to drought are paramount to providing scientific information for drought risk mitigation. In this paper, the spatial-temporal pattern of drought and the response lag of vegetation in Nebraska were analyzed from 2000 to 2015. Based on the long-term Daymet data set, the standard precipitation index (SPI) was computed to identify precipitation anomalies, and the Gaussian function was applied to obtain temperature anomalies. Vegetation anomaly was identified by dynamic time warping technique using a remote sensing Normalized Difference Vegetation Index (NDVI) time series. Finally, multilayer correlation analysis was applied to obtain the response lag of different vegetation types. The results show that Nebraska suffered severe drought events in 2002 and 2012. The response lag of vegetation to drought typically ranged from 30 to 45 days varying for different vegetation types and human activities (water use and management). Grasslands had the shortest response lag (~35 days), while forests had the longest lag period (~48 days). For specific crop types, the response lag of winter wheat varied among different regions of Nebraska (35–45 days), while soybeans, corn and alfalfa had similar response lag times of approximately 40 days.

Palmer Amaranth (Amaranthus palmeri) Competition for Water in Cotton

Weed Science ◽  
2015 ◽  
Vol 63 (4) ◽  
pp. 928-935 ◽  
Author(s):  
Sarah T. Berger ◽  
Jason A. Ferrell ◽  
Diane L. Rowland ◽  
Theodore M. Webster
Keyword(s):  
Water Content ◽  
Relative Water Content ◽  
Yield Loss ◽  
Linear Trend ◽  
Palmer Amaranth ◽  
Cotton Production ◽  
Excess Water ◽  
Relative Water ◽  
Competition For Light ◽  
Daily Water

Palmer amaranth is a troublesome weed in cotton production. Yield losses of 65% have been reported from season-long Palmer amaranth competition with cotton. To determine whether water is a factor in this system, experiments were conduced in 2011, 2012, and 2013 in Citra, FL, and in Tifton, GA. In 2011, infrequent rainfall lead to drought stress. The presence of Palmer amaranth resulted in decreased soil relative water content up to 1 m in depth. Cotton stomatal conductance (gs) was reduced up to 1.8 m from a Palmer amaranth plant. In 2012 and 2013 higher than average rainfall resulted in excess water throughout the growing season. In this situation, no differences were found in soil relative water content or cottongsas a function of proximity to Palmer amaranth. A positive linear trend was found in cotton photosynthesis and yield; each parameter increased as distance from Palmer amaranth increased. Even in these well-watered conditions, daily water use of Palmer amaranth was considerably higher than that of cotton, at 1.2 and 0.49 g H20 cm−2d−1, respectively. Although Palmer amaranth removed more water from the soil profile, rainfall was adequate to replenish the profile in 2 of the 3 yr of this study. However, yield loss due to Palmer amaranth was still observed despite no change ings, indicating other factors, such as competition for light or response to neighboring plants during development, are driving yield loss.

scholarly journals Measuring ice- and liquid-water properties in mixed-phase cloud layers at the Leipzig Cloudnet station

2016 ◽  
Vol 16 (16) ◽  
pp. 10609-10620 ◽  
Author(s):  
Johannes Bühl ◽  
Patric Seifert ◽  
Alexander Myagkov ◽  
Albert Ansmann
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Mass Flux ◽  
Mixed Phase ◽  
Cloud Base ◽  
Doppler Velocity ◽  
Special Focus ◽  
Data Set ◽  
Ice Water Content ◽  
Ice Water

Abstract. An analysis of the Cloudnet data set collected at Leipzig, Germany, with special focus on mixed-phase layered clouds is presented. We derive liquid- and ice-water content together with vertical motions of ice particles falling through cloud base. The ice mass flux is calculated by combining measurements of ice-water content and particle Doppler velocity. The efficiency of heterogeneous ice formation and its impact on cloud lifetime is estimated for different cloud-top temperatures by relating the ice mass flux and the liquid-water content at cloud top. Cloud radar measurements of polarization and Doppler velocity indicate that ice crystals formed in mixed-phase cloud layers with a geometrical thickness of less than 350 m are mostly pristine when they fall out of the cloud.

Dependence of efficiency of natural fish reproduction in water bodies of Kazakhstan from water level

2021 ◽  
pp. 32-41
Author(s):  
K.B. Isbekov ◽  
E.V. Kulikov ◽  
S.Zh. Asylbekova
Keyword(s):  
Water Content ◽  
Water Regime ◽  
Juvenile Fish ◽  
Hydrological Regime ◽  
Water Bodies ◽  
Fish Reproduction ◽  
Data Set ◽  
Commercial Fish ◽  
Level Of Significance ◽  
The Impact

The article deals with the relationship between the hydrological regime of water bodies and the efficiency of fish reproduction. The hydrological regime of water bodies in years of different water content influences the reproduction and, accordingly, the quantitative and qualitative composition of ichthyocenoses. The easiest way to assess the efficiency of fish reproduction is by such an indicator as the productivity of juveniles, i.e. the number of juvenile fish per unit area or volume. The material for this work was carried out in large fishing reservoirs of the Republic of Kazakhstan in the process of fishery research (2013–2018). Comparison of hydrological parameters and productivity of juveniles by years shows their relationship. Correlation coefficient between water content (runoff) of the river Zhaiyk and juvenile yield +0.73 (data set for 11 years, reliable for the level of significance p = 0.01). The yield of juvenile fish from Lake Balkhash has a high correlative dependence on the inflow of water into the lake (r = +0.826) (massif 2013–2018, reliable for the level of significance p = 0.05). Correlation analysis showed that the productivity of juvenile fish in the Kapshagai reservoir has an average degree of dependence on water content (average annual level) (r = +0.641, reliable for the level of significance p = 0.05). Regular relationships between the water regime and the efficiency of reproduction (productivity of juveniles) of fish have been established. The efficiency of natural reproduction of commercial fish species in modern conditions of the water regime, water withdrawal for economic needs and the impact of fishing is significantly reduced, but with the implementation of the reclamation measures proposed in the work, its partial restoration is possible.

scholarly journals Leaf area controls on energy partitioning of a temperate mountain grassland

2008 ◽  
Vol 5 (2) ◽  
pp. 421-431 ◽  
Author(s):  
A. Hammerle ◽  
A. Haslwanter ◽  
U. Tappeiner ◽  
A. Cernusca ◽  
G. Wohlfahrt
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Driving Forces ◽  
Vegetation Period ◽  
Soil Heat Flux ◽  
Energy Partitioning ◽  
Summer Drought ◽  
Evaporative Demand ◽  
Data Set ◽  
Mountain Grassland

Abstract. Using a six year data set of eddy covariance flux measurements of sensible and latent heat, soil heat flux, net radiation, above-ground phytomass and meteorological driving forces energy partitioning was investigated at a temperate mountain grassland managed as a hay meadow in the Stubai Valley (Austria). The main findings of the study were: (i) Energy partitioning was dominated by latent heat, followed by sensible heat and the soil heat flux; (ii) When compared to standard environmental forcings, the amount of green plant matter, which due to three cuts varied considerably during the vegetation period, explained similar, and partially larger, fractions of the variability in energy partitioning; (iii) There were little, if any, indications of water stress effects on energy partitioning, despite reductions in soil water availability in combination with high evaporative demand, e.g. during the summer drought of 2003.

scholarly journals Calibration of a Multiphase Model Based on a Comprehensive Data Set for a Normal Strength Concrete

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 791 ◽  
Author(s):  
Peter Gamnitzer ◽  
Martin Drexel ◽  
Andreas Brugger ◽  
Günter Hofstetter
Keyword(s):  
Water Content ◽  
Accurate Determination ◽  
Autogenous Shrinkage ◽  
Shrinkage Strain ◽  
Desorption Isotherm ◽  
Multiphase Model ◽  
Large Set ◽  
Creep Tests ◽  
Data Set ◽  
Water Desorption

Hygro-thermo-chemo-mechanical modelling of time-dependent concrete behavior requires the accurate determination of a large set of parameters. In this paper, the parameters of a multiphase model are calibrated based on a comprehensive set of experiments for a particular concrete of grade C30/37. The experiments include a calorimetry test, tests for age-dependent mechanical properties, tests for determining the water desorption isotherm, shrinkage tests, and compressive creep tests. The latter two were performed on sealed and unsealed specimens with accompanying mass water content measurements. The multiphase model is based on an effective stress formulation. It features a porosity-dependent desorption isotherm, taking into account the time-dependency of the desorption properties. The multiphase model is shown to yield excellent results for the evolutions of the mechanical parameters. The evolution of the autogenous shrinkage strain and evolutions of the creep compliances for loading at concrete ages of 2 days, 7 days, and 28 days are well predicted together with the respective mass water content evolution. This also holds for the evolution of the drying shrinkage strain, at least for moderate drying up to one year. However, it will be demonstrated that for longer drying times further conceptual thoughts concerning the coupled representation of shrinkage and creep are required.

scholarly journals Coupled hydrogeophysical parameter estimation using a sequential Bayesian approach

2010 ◽  
Vol 14 (3) ◽  
pp. 545-556 ◽  
Author(s):  
J. Rings ◽  
J. A. Huisman ◽  
H. Vereecken
Keyword(s):  
Water Content ◽  
Particle Filtering ◽  
Field Data ◽  
Synthetic Data ◽  
Time Domain Reflectometry ◽  
Second Step ◽  
Parameter Estimates ◽  
Posterior Distributions ◽  
Data Set ◽  
Resistivity Tomography

Abstract. Coupled hydrogeophysical methods infer hydrological and petrophysical parameters directly from geophysical measurements. Widespread methods do not explicitly recognize uncertainty in parameter estimates. Therefore, we apply a sequential Bayesian framework that provides updates of state, parameters and their uncertainty whenever measurements become available. We have coupled a hydrological and an electrical resistivity tomography (ERT) forward code in a particle filtering framework. First, we analyze a synthetic data set of lysimeter infiltration monitored with ERT. In a second step, we apply the approach to field data measured during an infiltration event on a full-scale dike model. For the synthetic data, the water content distribution and the hydraulic conductivity are accurately estimated after a few time steps. For the field data, hydraulic parameters are successfully estimated from water content measurements made with spatial time domain reflectometry and ERT, and the development of their posterior distributions is shown.

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