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Détails du magazine
Format
Magazine
eISSN
1338-4333
ISSN
0042-790X
Première publication
28 Mar 2009
Période de publication
4 fois par an
Langues
Anglais

Chercher

Volume 61 (2013): Edition 1 (March 2013)

Détails du magazine
Format
Magazine
eISSN
1338-4333
ISSN
0042-790X
Première publication
28 Mar 2009
Période de publication
4 fois par an
Langues
Anglais

Chercher

11 Articles
access type Accès libre

Editorial and preface to thematic issue on biohydrology

Publié en ligne: 15 Mar 2013
Pages: 1 - 2

Résumé

access type Accès libre

Small-scale contact angle mapping on undisturbed soil surfaces

Publié en ligne: 15 Mar 2013
Pages: 3 - 8

Résumé

Abstract

Research of the last years pointed out that most soils are neither completely hydrophilic nor hydrophobic, but exhibit a subcritical level of water repellency (i.e. contact angle, CA > 0° and < 90°). Soil water repellency (SWR) is mainly caused by organic compounds of different origin and structure, showing the relevance of biofilms and organic coatings present at many particle surfaces. Despite the importance of SWR for hydraulic processes like preferential flow phenomena, generation of heterogeneous moisture patterns, or surface run-off generation, detailed investigations on the spatial variability of SWR at various scales have rarely been carried out. We introduce a new and easy-to-apply operation for measuring the spatial distribution of SWR using a modified sessile drop method for direct optical assessment of CA at a small scale. The specific objectives of this paper are to apply a sampling and preparation technique that preserves the original spatial arrangement of soil particles and to characterize soil wettability in terms of CA at a high spatial resolution. Results revealed that the sampling and preparation technique allows determination of CA at the millimeter scale using droplets of 1 μL volume. Direct measurement on grain surfaces of the sand fraction is possible for grain sizes > 300 μm using drop volumes down to 0.1 μL. Geostatistical evaluation showed that the measurement grid scale is below the range of spatial dependency for droplets of 1 μL volume, but not for measurements on single grains (pure nugget effect). Results show further that the small-scale differences in wettability, especially for CA < 90°, cannot be detected by the conventional WDPT test. From these findings it can be concluded that the proposed technique allows the identification of small-scale variations in wettability that may promote the formation of heterogeneous flow fields and moisture patterns in soil under unsaturated conditions.

Keywords

  • Hydrophobicity
  • Sessile drop method
  • Soil water repellency
  • Water drop penetration time
  • Wettability
access type Accès libre

Evaluating the bio-hydrological impact of a cloud forest in Central America using a semi-distributed water balance model

Publié en ligne: 15 Mar 2013
Pages: 9 - 20b

Résumé

Abstract

Water scarcity poses a major threat to food security and human health in Central America and is increasingly recognized as a pressing regional issues caused primarily by deforestation and population pressure. Tools that can reliably simulate the major components of the water balance with the limited data available and needed to drive management decision and protect water supplies in this region. Four adjacent forested headwater catchments in La Tigra National Park, Honduras, ranging in size from 70 to 635 ha were instrumented and discharge measured over a one year period. A semi-distributed water balance model was developed to characterize the bio-hydrology of the four catchments, one of which is primarily cloud forest cover. The water balance model simulated daily stream discharges well, with Nash Sutcliffe model efficiency (E) values ranging from 0.67 to 0.90. Analysis of calibrated model parameters showed that despite all watersheds having similar geologic substrata, the bio-hydrological response the cloud forest indicated less plantavailable water in the root zone and greater groundwater recharge than the non cloud forest cover catchments. This resulted in watershed discharge on a per area basis four times greater from the cloud forest than the other watersheds despite only relatively minor differences in annual rainfall. These results highlight the importance of biological factors (cloud forests in this case) for sustained provision of clean, potable water, and the need to protect the cloud forest areas from destruction, particularly in the populated areas of Central America.

Keywords

  • Central America
  • Rainfall-runoff
  • Thornthwaite-mather
  • Water balance model
  • Cloud forest
  • Monsoonal climate
access type Accès libre

Eco-hydrological impacts of Eucalyptus in the semi humid Ethiopian Highlands: the Lake Tana Plain

Publié en ligne: 15 Mar 2013
Pages: 21 - 29b

Résumé

Abstract

Eucalyptus is the tree of choice for wood production by farmers in Ethiopia. Although there are many claims about its harmful effect on ecology and water availability, little actual research exists. The main objective of this study was, therefore, to study the extent of harm of Eucalyptus on the ecosystem. This study was conducted at the Koga Watershed near Lake Tana in Ethiopia. Twenty-five farmers were interviewed and a field experiment with three replications was carried out to quantify the effect of Eucalyptus on various soil physical and chemical properties and maize crop measurements and to compare bulk density, soil moisture contents, maize crop counts and shading effects in fields bordered by Eucalyptus and Croton macrostachyus. Our results show that Eucalyptus decreased both soil nutrients and maize yields within 20 m of the trees. Although moisture content was not affected during the monsoon, it decreased faster within 30 m of the Eucalyptus trees than elsewhere. Soils become water repellent, too. Local farmers’ perception agreed with our experimental findings and indicated that Eucalyptus trees are exhausting the once productive land. They also reported that Eucalyptus dries up springs. Despite this, the growers insist on planting Eucalyptus because of its cash income.

Keywords

  • Eucalyptus
  • Soil water repellency
  • Croton machrostachyus
  • Koga watershed
access type Accès libre

Site effects on root characteristics and soil protection capability of two cover crops grown in South Bulgaria

Publié en ligne: 15 Mar 2013
Pages: 30 - 38

Résumé

Abstract

Water erosion has been recognized as a major soil degradation process worldwide. This is of special relevance in the semi-arid areas of South Bulgaria with long periods of drought along with severe rainfall events. The main objective of this study was to evaluate the applicability of Bromus innermis L. and Lotus corniculatus L. for soil protection purposes under different site conditions. The site parameters considered were slope, fertilization and a range of soil physical parameters. The plant parameters were canopy cover, biomass, and root morphological characteristics. The experiment includes plots without and with eleven rates of NPK fertilization on gentle (6o) and steep slopes (12o). It was observed that the effect of fertilization on shoot and root growth was stronger on the gentle than on the steep slopes. The biomass accumulation was more sensitive to N than the PK fertilizer applications. The increase of the root density with increasing fertilization rates was more pronounced for the mass than for length or surface area. A significant effect on root diameter was found only for the variants with the highest N application. Treatments with the highest root mass density on both slopes showed the greatest potential for reducing erosion.

Keywords

  • Rangeland
  • Cover crops
  • Fertilization
  • Root characteristics
  • Slope protection
access type Accès libre

Simulation of the influence of rainfall redistribution in spruce and beech forest on the leaching of Al and SO4 2- from forest soils

Publié en ligne: 15 Mar 2013
Pages: 39 - 49

Résumé

Abstract

The aim of this study was to assess the impact of different vegetation on the distribution of rainfall (due to throughfall and stemflow), water regime, and Al and SO4 2- leaching from forest soils. The water flow and Al and SO4 2- transport were modeled using HYDRUS-1D. The study was performed at two elevation transects on the Paličník and Smědava Mountain in Jizera mountains. Podzols and Cambisols were prevailing soil units in this area. It was shown that the effect of the precipitation redistribution on water regime was considerable in the beech forest, while it was almost negligible in the spruce forest. Redistribution of precipitation under trees caused runoff (in one case), increased water discharge through the soil profile bottom, reduction of water storage in the soil, and thus reduction of root water uptake. Simulated Al leaching from the soil profile was determined mainly by the initial Al content in the soil profile bottom. Leaching of SO4 2- was mainly determined by its initial content in the soil and to a lesser extent by redistributed precipitation and SO4 2- deposition.

Keywords

  • Throughfall
  • Stemflow
  • Wet deposition
  • Soil water regime
  • Solute transport
access type Accès libre

Combined proton NMR wideline and NMR relaxometry to study SOM-water interactions of cation-treated soils

Publié en ligne: 15 Mar 2013
Pages: 50 - 63

Résumé

Abstract

Focusing on the idea that multivalent cations affect SOM matrix and surface, we treated peat and soil samples by solutions of NaCl, CaCl2 or AlCl3. Water binding was characterized with low field 1H-NMR-relaxometry (20 MHz) and 1H wideline NMR spectroscopy (400 MHz) and compared to contact angles.

From 1H wideline, we distinguished mobile water and water involved in water molecule bridges (WaMB). Large part of cation bridges (CaB) between SOM functional groups are associated with WaMB. Unexpectedly, 1H NMRrelaxometry relaxation rates suggest that cross-linking in the Al-containing peat is not stronger than that by Ca.

The relation between percentage of mobile water and WaMB water in the context of wettability and 1H NMR relaxation times confirms that wettability controls the water film surrounding soil particles. Wettability is controlled by WaMB-CaB associations fixing hydrophilic functional groups in the SOM interior. This can lead to severe water repellency. Wettability decreases with increasing involvement of functional groups in CaB-WaMB associations. The results demonstrate the relevance of CaB and WaMB for the dynamics of biogeochemical and hydrological processes under field conditions, as only a few percent of organic matter can affect the physical, chemical, and biological functioning of the entire 3-phase ecosystem.

Keywords

  • Soil organic matter (SOM)
  • Low field 1H NMR relaxometry
  • 1H wideline NMR spectroscopy
  • Contact angle
  • Cation bridges
  • Water molecule bridges
access type Accès libre

The canopy rainfall interception in actual and potential distribution of Qinghai spruce (Picea crassifolia) forest

Publié en ligne: 15 Mar 2013
Pages: 64 - 72

Résumé

Abstract

Interception is one of the most underestimated processes in hydrological cycle in arid and semiarid regions. In Qilian Mountains of northwestern arid and semiarid China, the Qinghai spruce (Picea crassifolia) forest plays an important role in the hydrological cycle of the inland Heihe River basin. The historical disturbance of Qinghai spruce forest has resulted in various ecological problems. In order to realize the sustainable development of Heihe River basin, the Chinese government implemented restoration practices for Qinghai spruce in the past three decades. In this study, we estimated the rainfall interception in the actual and potential distribution of Qinghai spruce forest. Some of the important findings include: (1) The interception ratio of rainfall events ranged from 11-51% with a mean value of 27.02%; (2) Totally, 147 Mt of rainfall is intercepted by canopy of actual Qinghai spruce forest, in the projected potential distribution of the forest, totally 407 Mt of rainfall will be intercepted.

Keywords

  • Qinghai spruce
  • Actual interception
  • Potential interception
  • Potential distribution
  • Ecohydrology
access type Accès libre

Tolerance of canola to drought and salinity stresses in terms of root water uptake model parameters

Publié en ligne: 15 Mar 2013
Pages: 73 - 80

Résumé

Abstract

Canola (Brassica napus) is cultivated for oil as a biofuel crop. Few quantitative data concerning its tolerance to abiotic stresses has been presented. We evaluated the tolerances of canola to drought and salinity stresses in terms of parameter values in a macroscopic root water uptake model. We conducted an experiment using nine columns with two plants in each: three columns were under drought stresses, another three were under saline stress and others provided potential transpiration. Two soil moisture and salinity probes were inserted into each of the six columns under stress to monitor water content and electrical conductivity. Weight of the columns was manually measured to obtain daily transpiration. Water uptake at each depth and time was calculated by substituting linearly interpolated matric and osmotic potentials into the stress response function. Determined stress response functions indicated that canola is more sensitive to drought compared to Jatropha. While, it was found to be as tolerant as Jatropha to salinity stress in terms of transpiration. Matric potential was more determining than osmotic potential to root water uptake of canola.

Keywords

  • Irrigation with saline water
  • Biofuel crops
  • Electrical conductivity
  • Feddes’s model
access type Accès libre

Uncertainties in dissolved organic carbon load estimation in a small stream

Publié en ligne: 15 Mar 2013
Pages: 81 - 83

Résumé

Abstract

Dissolved organic carbon (DOC) transported by rivers represents an important link between carbon pools of terrestrial and oceanic ecosystems. However, it is unclear how frequent DOC must be sampled to obtain reasonable load estimates. Here, we used continuous records of the specific UV absorption coefficient (SAC) and discharge from a headwater stream at the Ore Mountains (Germany) to calculate load errors depending on DOC sampling frequency. SAC was used as a proxy for DOC. The results show that the load was underestimated by 13-19% with monthly, 10-13% with bi-weekly and 7-9% with weekly DOC samplings, respectively. We conclude that collecting additional data from high discharge events decrease the error significantly.

Keywords

  • Dissolved organic carbon
  • Sampling strategy
  • UV absorption
  • Discharge
  • Yield
  • Reservoir
access type Accès libre

Temperature influences water sorptivity of soil aggregates

Publié en ligne: 15 Mar 2013
Pages: 84 - 87

Résumé

Abstract

The aim of this study was to determine the potential development of water sorptivity of soil aggregates by heating. Soil aggregates were sampled from arable layer of 5 Polish soils: Haplic Luvisol 1 from Czesławice, Haplic Luvisol 2 from Wierzchucinek, Haplic Cambisol from Felin, Gleyic Mollic Cambisol from Chylice, and Haplic Phaeozem from Grabiec. Three aggregates of each soil type with minimum diameter between 4 and 10 mm were heated in the oven for at least 3 hours at temperatures 20, 100, 200, 250, and 360ºC. After each temperature treatment the soil aggregates were conditioned at the room temperature for 16 hours. Laboratory measurements of water sorptivity of soil aggregates were performed under a negative tension h0 = -2 cm using tension infiltrometer. It was found that the exposure to temperatures between 100 and 200°C tends to decrease water sorptivity of aggregates from all the studied soils but one (Haplic Luvisol 1), followed by about two- to four-fold increase in water sorptivity for exposure to temperatures of 250°C (in Haplic Luvisol 1, Haplic Luvisol 2, and Haplic Phaeozem) or 360°C (in Haplic Cambisol and Gleyic Mollic Cambisol).

Keywords

  • Soil
  • Aggregate
  • Sorptivity
  • Temperature
  • Water repellency
11 Articles
access type Accès libre

Editorial and preface to thematic issue on biohydrology

Publié en ligne: 15 Mar 2013
Pages: 1 - 2

Résumé

access type Accès libre

Small-scale contact angle mapping on undisturbed soil surfaces

Publié en ligne: 15 Mar 2013
Pages: 3 - 8

Résumé

Abstract

Research of the last years pointed out that most soils are neither completely hydrophilic nor hydrophobic, but exhibit a subcritical level of water repellency (i.e. contact angle, CA > 0° and < 90°). Soil water repellency (SWR) is mainly caused by organic compounds of different origin and structure, showing the relevance of biofilms and organic coatings present at many particle surfaces. Despite the importance of SWR for hydraulic processes like preferential flow phenomena, generation of heterogeneous moisture patterns, or surface run-off generation, detailed investigations on the spatial variability of SWR at various scales have rarely been carried out. We introduce a new and easy-to-apply operation for measuring the spatial distribution of SWR using a modified sessile drop method for direct optical assessment of CA at a small scale. The specific objectives of this paper are to apply a sampling and preparation technique that preserves the original spatial arrangement of soil particles and to characterize soil wettability in terms of CA at a high spatial resolution. Results revealed that the sampling and preparation technique allows determination of CA at the millimeter scale using droplets of 1 μL volume. Direct measurement on grain surfaces of the sand fraction is possible for grain sizes > 300 μm using drop volumes down to 0.1 μL. Geostatistical evaluation showed that the measurement grid scale is below the range of spatial dependency for droplets of 1 μL volume, but not for measurements on single grains (pure nugget effect). Results show further that the small-scale differences in wettability, especially for CA < 90°, cannot be detected by the conventional WDPT test. From these findings it can be concluded that the proposed technique allows the identification of small-scale variations in wettability that may promote the formation of heterogeneous flow fields and moisture patterns in soil under unsaturated conditions.

Keywords

  • Hydrophobicity
  • Sessile drop method
  • Soil water repellency
  • Water drop penetration time
  • Wettability
access type Accès libre

Evaluating the bio-hydrological impact of a cloud forest in Central America using a semi-distributed water balance model

Publié en ligne: 15 Mar 2013
Pages: 9 - 20b

Résumé

Abstract

Water scarcity poses a major threat to food security and human health in Central America and is increasingly recognized as a pressing regional issues caused primarily by deforestation and population pressure. Tools that can reliably simulate the major components of the water balance with the limited data available and needed to drive management decision and protect water supplies in this region. Four adjacent forested headwater catchments in La Tigra National Park, Honduras, ranging in size from 70 to 635 ha were instrumented and discharge measured over a one year period. A semi-distributed water balance model was developed to characterize the bio-hydrology of the four catchments, one of which is primarily cloud forest cover. The water balance model simulated daily stream discharges well, with Nash Sutcliffe model efficiency (E) values ranging from 0.67 to 0.90. Analysis of calibrated model parameters showed that despite all watersheds having similar geologic substrata, the bio-hydrological response the cloud forest indicated less plantavailable water in the root zone and greater groundwater recharge than the non cloud forest cover catchments. This resulted in watershed discharge on a per area basis four times greater from the cloud forest than the other watersheds despite only relatively minor differences in annual rainfall. These results highlight the importance of biological factors (cloud forests in this case) for sustained provision of clean, potable water, and the need to protect the cloud forest areas from destruction, particularly in the populated areas of Central America.

Keywords

  • Central America
  • Rainfall-runoff
  • Thornthwaite-mather
  • Water balance model
  • Cloud forest
  • Monsoonal climate
access type Accès libre

Eco-hydrological impacts of Eucalyptus in the semi humid Ethiopian Highlands: the Lake Tana Plain

Publié en ligne: 15 Mar 2013
Pages: 21 - 29b

Résumé

Abstract

Eucalyptus is the tree of choice for wood production by farmers in Ethiopia. Although there are many claims about its harmful effect on ecology and water availability, little actual research exists. The main objective of this study was, therefore, to study the extent of harm of Eucalyptus on the ecosystem. This study was conducted at the Koga Watershed near Lake Tana in Ethiopia. Twenty-five farmers were interviewed and a field experiment with three replications was carried out to quantify the effect of Eucalyptus on various soil physical and chemical properties and maize crop measurements and to compare bulk density, soil moisture contents, maize crop counts and shading effects in fields bordered by Eucalyptus and Croton macrostachyus. Our results show that Eucalyptus decreased both soil nutrients and maize yields within 20 m of the trees. Although moisture content was not affected during the monsoon, it decreased faster within 30 m of the Eucalyptus trees than elsewhere. Soils become water repellent, too. Local farmers’ perception agreed with our experimental findings and indicated that Eucalyptus trees are exhausting the once productive land. They also reported that Eucalyptus dries up springs. Despite this, the growers insist on planting Eucalyptus because of its cash income.

Keywords

  • Eucalyptus
  • Soil water repellency
  • Croton machrostachyus
  • Koga watershed
access type Accès libre

Site effects on root characteristics and soil protection capability of two cover crops grown in South Bulgaria

Publié en ligne: 15 Mar 2013
Pages: 30 - 38

Résumé

Abstract

Water erosion has been recognized as a major soil degradation process worldwide. This is of special relevance in the semi-arid areas of South Bulgaria with long periods of drought along with severe rainfall events. The main objective of this study was to evaluate the applicability of Bromus innermis L. and Lotus corniculatus L. for soil protection purposes under different site conditions. The site parameters considered were slope, fertilization and a range of soil physical parameters. The plant parameters were canopy cover, biomass, and root morphological characteristics. The experiment includes plots without and with eleven rates of NPK fertilization on gentle (6o) and steep slopes (12o). It was observed that the effect of fertilization on shoot and root growth was stronger on the gentle than on the steep slopes. The biomass accumulation was more sensitive to N than the PK fertilizer applications. The increase of the root density with increasing fertilization rates was more pronounced for the mass than for length or surface area. A significant effect on root diameter was found only for the variants with the highest N application. Treatments with the highest root mass density on both slopes showed the greatest potential for reducing erosion.

Keywords

  • Rangeland
  • Cover crops
  • Fertilization
  • Root characteristics
  • Slope protection
access type Accès libre

Simulation of the influence of rainfall redistribution in spruce and beech forest on the leaching of Al and SO4 2- from forest soils

Publié en ligne: 15 Mar 2013
Pages: 39 - 49

Résumé

Abstract

The aim of this study was to assess the impact of different vegetation on the distribution of rainfall (due to throughfall and stemflow), water regime, and Al and SO4 2- leaching from forest soils. The water flow and Al and SO4 2- transport were modeled using HYDRUS-1D. The study was performed at two elevation transects on the Paličník and Smědava Mountain in Jizera mountains. Podzols and Cambisols were prevailing soil units in this area. It was shown that the effect of the precipitation redistribution on water regime was considerable in the beech forest, while it was almost negligible in the spruce forest. Redistribution of precipitation under trees caused runoff (in one case), increased water discharge through the soil profile bottom, reduction of water storage in the soil, and thus reduction of root water uptake. Simulated Al leaching from the soil profile was determined mainly by the initial Al content in the soil profile bottom. Leaching of SO4 2- was mainly determined by its initial content in the soil and to a lesser extent by redistributed precipitation and SO4 2- deposition.

Keywords

  • Throughfall
  • Stemflow
  • Wet deposition
  • Soil water regime
  • Solute transport
access type Accès libre

Combined proton NMR wideline and NMR relaxometry to study SOM-water interactions of cation-treated soils

Publié en ligne: 15 Mar 2013
Pages: 50 - 63

Résumé

Abstract

Focusing on the idea that multivalent cations affect SOM matrix and surface, we treated peat and soil samples by solutions of NaCl, CaCl2 or AlCl3. Water binding was characterized with low field 1H-NMR-relaxometry (20 MHz) and 1H wideline NMR spectroscopy (400 MHz) and compared to contact angles.

From 1H wideline, we distinguished mobile water and water involved in water molecule bridges (WaMB). Large part of cation bridges (CaB) between SOM functional groups are associated with WaMB. Unexpectedly, 1H NMRrelaxometry relaxation rates suggest that cross-linking in the Al-containing peat is not stronger than that by Ca.

The relation between percentage of mobile water and WaMB water in the context of wettability and 1H NMR relaxation times confirms that wettability controls the water film surrounding soil particles. Wettability is controlled by WaMB-CaB associations fixing hydrophilic functional groups in the SOM interior. This can lead to severe water repellency. Wettability decreases with increasing involvement of functional groups in CaB-WaMB associations. The results demonstrate the relevance of CaB and WaMB for the dynamics of biogeochemical and hydrological processes under field conditions, as only a few percent of organic matter can affect the physical, chemical, and biological functioning of the entire 3-phase ecosystem.

Keywords

  • Soil organic matter (SOM)
  • Low field 1H NMR relaxometry
  • 1H wideline NMR spectroscopy
  • Contact angle
  • Cation bridges
  • Water molecule bridges
access type Accès libre

The canopy rainfall interception in actual and potential distribution of Qinghai spruce (Picea crassifolia) forest

Publié en ligne: 15 Mar 2013
Pages: 64 - 72

Résumé

Abstract

Interception is one of the most underestimated processes in hydrological cycle in arid and semiarid regions. In Qilian Mountains of northwestern arid and semiarid China, the Qinghai spruce (Picea crassifolia) forest plays an important role in the hydrological cycle of the inland Heihe River basin. The historical disturbance of Qinghai spruce forest has resulted in various ecological problems. In order to realize the sustainable development of Heihe River basin, the Chinese government implemented restoration practices for Qinghai spruce in the past three decades. In this study, we estimated the rainfall interception in the actual and potential distribution of Qinghai spruce forest. Some of the important findings include: (1) The interception ratio of rainfall events ranged from 11-51% with a mean value of 27.02%; (2) Totally, 147 Mt of rainfall is intercepted by canopy of actual Qinghai spruce forest, in the projected potential distribution of the forest, totally 407 Mt of rainfall will be intercepted.

Keywords

  • Qinghai spruce
  • Actual interception
  • Potential interception
  • Potential distribution
  • Ecohydrology
access type Accès libre

Tolerance of canola to drought and salinity stresses in terms of root water uptake model parameters

Publié en ligne: 15 Mar 2013
Pages: 73 - 80

Résumé

Abstract

Canola (Brassica napus) is cultivated for oil as a biofuel crop. Few quantitative data concerning its tolerance to abiotic stresses has been presented. We evaluated the tolerances of canola to drought and salinity stresses in terms of parameter values in a macroscopic root water uptake model. We conducted an experiment using nine columns with two plants in each: three columns were under drought stresses, another three were under saline stress and others provided potential transpiration. Two soil moisture and salinity probes were inserted into each of the six columns under stress to monitor water content and electrical conductivity. Weight of the columns was manually measured to obtain daily transpiration. Water uptake at each depth and time was calculated by substituting linearly interpolated matric and osmotic potentials into the stress response function. Determined stress response functions indicated that canola is more sensitive to drought compared to Jatropha. While, it was found to be as tolerant as Jatropha to salinity stress in terms of transpiration. Matric potential was more determining than osmotic potential to root water uptake of canola.

Keywords

  • Irrigation with saline water
  • Biofuel crops
  • Electrical conductivity
  • Feddes’s model
access type Accès libre

Uncertainties in dissolved organic carbon load estimation in a small stream

Publié en ligne: 15 Mar 2013
Pages: 81 - 83

Résumé

Abstract

Dissolved organic carbon (DOC) transported by rivers represents an important link between carbon pools of terrestrial and oceanic ecosystems. However, it is unclear how frequent DOC must be sampled to obtain reasonable load estimates. Here, we used continuous records of the specific UV absorption coefficient (SAC) and discharge from a headwater stream at the Ore Mountains (Germany) to calculate load errors depending on DOC sampling frequency. SAC was used as a proxy for DOC. The results show that the load was underestimated by 13-19% with monthly, 10-13% with bi-weekly and 7-9% with weekly DOC samplings, respectively. We conclude that collecting additional data from high discharge events decrease the error significantly.

Keywords

  • Dissolved organic carbon
  • Sampling strategy
  • UV absorption
  • Discharge
  • Yield
  • Reservoir
access type Accès libre

Temperature influences water sorptivity of soil aggregates

Publié en ligne: 15 Mar 2013
Pages: 84 - 87

Résumé

Abstract

The aim of this study was to determine the potential development of water sorptivity of soil aggregates by heating. Soil aggregates were sampled from arable layer of 5 Polish soils: Haplic Luvisol 1 from Czesławice, Haplic Luvisol 2 from Wierzchucinek, Haplic Cambisol from Felin, Gleyic Mollic Cambisol from Chylice, and Haplic Phaeozem from Grabiec. Three aggregates of each soil type with minimum diameter between 4 and 10 mm were heated in the oven for at least 3 hours at temperatures 20, 100, 200, 250, and 360ºC. After each temperature treatment the soil aggregates were conditioned at the room temperature for 16 hours. Laboratory measurements of water sorptivity of soil aggregates were performed under a negative tension h0 = -2 cm using tension infiltrometer. It was found that the exposure to temperatures between 100 and 200°C tends to decrease water sorptivity of aggregates from all the studied soils but one (Haplic Luvisol 1), followed by about two- to four-fold increase in water sorptivity for exposure to temperatures of 250°C (in Haplic Luvisol 1, Haplic Luvisol 2, and Haplic Phaeozem) or 360°C (in Haplic Cambisol and Gleyic Mollic Cambisol).

Keywords

  • Soil
  • Aggregate
  • Sorptivity
  • Temperature
  • Water repellency

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