scholarly journals Modelling land–atmosphere daily exchanges of NO, NH<sub>3</sub>, and CO<sub>2</sub> in a semi-arid grazed ecosystem in Senegal

2019 ◽  
Vol 16 (9) ◽  
pp. 2049-2077 ◽  
Author(s):  
Claire Delon ◽  
Corinne Galy-Lacaux ◽  
Dominique Serça ◽  
Erwan Personne ◽  
Eric Mougin ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Co2 Emissions ◽  
Simultaneous Increase ◽  
Wet Season ◽  
Nh3 Emission ◽  
Order Of Magnitude ◽  
Deposition Processes ◽  
Sahel Region ◽  
Semi Arid

Abstract. Three different models (STEP–GENDEC–NOflux, Zhang2010, and Surfatm) are used to simulate NO, CO2, and NH3 fluxes at the daily scale for 2 years (2012–2013) in a semi-arid grazed ecosystem at Dahra (15∘24′10′′ N, 15∘25′56′′ W, Senegal, Sahel). Model results are evaluated against experimental results acquired during three field campaigns. At the end of the dry season, when the first rains re-wet the dry soils, the model STEP–GENDEC–NOflux simulates the sudden mineralization of buried litter, leading to pulses in soil respiration and NO fluxes. The contribution of wet season fluxes of NO and CO2 to the annual mean is respectively 51 % and 57 %. NH3 fluxes are simulated by two models: Surfatm and Zhang2010. During the wet season, air humidity and soil moisture increase, leading to a transition between low soil NH3 emissions (which dominate during the dry months) and large NH3 deposition on vegetation during wet months. Results show a great impact of the soil emission potential, a difference in the deposition processes on the soil and the vegetation between the two models with however a close agreement of the total fluxes. The order of magnitude of NO, NH3, and CO2 fluxes is correctly represented by the models, as well as the sharp transitions between seasons, specific to the Sahel region. The role of soil moisture in flux magnitude is highlighted, whereas the role of soil temperature is less obvious. The simultaneous increase in NO and CO2 emissions and NH3 deposition at the beginning of the wet season is attributed to the availability of mineral nitrogen in the soil and also to microbial processes, which distribute the roles between respiration (CO2 emissions), nitrification (NO emissions), volatilization, and deposition (NH3 emission/deposition). The objectives of this study are to understand the origin of carbon and nitrogen compounds exchanges between the soil and the atmosphere and to quantify these exchanges on a longer timescale when only a few measurements have been performed.

scholarly journals Modelling land atmosphere daily exchanges of NO, NH<sub>3</sub>, and CO<sub>2</sub> in a semi-arid grazed ecosystem in Senegal

2018 ◽  
Author(s):  
Claire Delon ◽  
Corinne Galy-Lacaux ◽  
Dominique Serça ◽  
Erwan Personne ◽  
Eric Mougin ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Co2 Emissions ◽  
Simultaneous Increase ◽  
Wet Season ◽  
Nh3 Emission ◽  
Order Of Magnitude ◽  
Daily Scale ◽  
Sahel Region ◽  
Semi Arid

Abstract. Three different models (STEP-GENDEC-NOflux, Zhang2010 and Surfatm) are used to simulate NO, CO2, and NH3 fluxes at the daily scale during two years (2012–2013) in a semi-arid grazed ecosystem at Dahra (15°24′10′′ N, 15°25′56′′ W, Senegal, Sahel). Model results are evaluated against experimental results acquired during three field campaigns. At the end of the dry season, when the first rains rewet the dry soils, the model STEP-GENDEC-NOflux simulate the sudden mineralization of buried litter, leading to pulses in soil respiration and NO fluxes. The contribution of wet season fluxes of NO and CO2 to the annual mean is respectively 51 % and 57 %. NH3 fluxes are simulated by two models: Surfatm and Zhang2010. During the wet season, air humidity and soil moisture increase, leading to a transition between low soil NH3 emissions (which dominate during the dry months) to large NH3 deposition on vegetation during wet months, Results show a great impact of the soil emission potential and a close agreement between the two models. The order of magnitude of NO, NH3 and CO2 fluxes are correctly represented by the models, as well as the sharp transitions between seasons, specific to the Sahel region. The role of soil moisture on flux magnitude is highlighted, whereas the role of soil temperature is less obvious. The simultaneous increase of NO and CO2 emissions and NH3 deposition at the beginning of the wet season is attributed to the availability of mineral nitrogen in the soil and also to microbial processes which distribute the roles between respiration (CO2 emissions), nitrification (NO emissions), volatilization and deposition (NH3 emission/deposition). This objective of this study is to understand the origin of carbon and nitrogen compounds exchanges between the soil and the atmosphere, and to quantify these exchanges on a longer time scale when only few measurements have been performed.

The role of landscape morphology on soil moisture variability in semi‐arid ecosystems

2020 ◽  
Author(s):  
Ankur Srivastava ◽  
Patricia M. Saco ◽  
Jose F. Rodriguez ◽  
Nikul Kumari ◽  
Kwok Pan Chun ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Arid Ecosystems ◽  
Landscape Morphology ◽  
Soil Moisture Variability ◽  
Semi Arid ◽  
Moisture Variability

Effect of temporal rainfall distribution and soil type on soil moisture and runoff generation in semi-arid Zimbabwe

2007 ◽  
Vol 38 (3) ◽  
pp. 249-263 ◽  
Author(s):  
F.T. Mugabe ◽  
M.G. Hodnett ◽  
A. Senzanje
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Daily Rainfall ◽  
Soil Surface ◽  
Runoff Generation ◽  
Stream Channels ◽  
Wet Season ◽  
Sodic Soils ◽  
Rainfall Distribution ◽  
Semi Arid

This paper examines the effect of temporal rainfall distribution on soil moisture and runoff generation in the 5.9 km2 Mutangi catchment in semi-arid Zimbabwe. Rainfall, soil moisture and runoff were measured during the 1999/00 and 2000/01 rainy seasons during which periods 755 mm and 615 mm of rainfall were received, respectively. The percentage of rainfall totals in these periods were 58% and 69%, respectively, in February. The total catchment runoff was 102 mm and 63 mm, of which 52% and 49% were recorded over 6 and 4 d in 2000 and 2001, respectively. Baseflow was negligible. Rainfall intensities were generally low. In the 1999/00 season there were 2 and 8 h with intensities &gt;20 mm h−1 and 10 mm h−1, respectively. Some runoff appears to be generated by Hortonian overland flow (HOF), mainly in the early wet season before ploughing creates a rougher soil surface. The dominant process of runoff in this catchment was saturated overland flow (SOF), which occurs when the soils become saturated from below. The sodic soils along the stream channels appear to generate most of the runoff because of their small capacity to store water before saturation. The ridge soils are coarse sands, with a large capacity to store rainfall. The transitional (slope) soils have an intermediate capacity to store water. If there is a sequence of daily events that completely fills the storage available in both the sodic and transitional soils, and which begins to saturate the ridge soils, there could be very large amounts of runoff (&gt;50% of the daily rainfall). The occurrence of such runoff events depends very heavily on the distribution of rainfall. Dry spells between rain events create storage, thereby reducing the risk of runoff from the next events.

scholarly journals Qualitative soil moisture assessment in semi-arid Africa: the role of experience and training on inter-rater reliability

2015 ◽  
Vol 12 (3) ◽  
pp. 3029-3058
Author(s):  
M. Rinderer ◽  
H. Komakech ◽  
D. Müller ◽  
J. Seibert
Keyword(s):  
Soil Moisture ◽  
Classification Scheme ◽  
Functional Relation ◽  
Soil Surface ◽  
Arid Environment ◽  
Rater Reliability ◽  
Moisture Conditions ◽  
And Training ◽  
Semi Arid

Abstract. Soil and water management is particularly relevant in semi-arid regions to enhance agricultural productivity. During periods of water scarcity soil moisture differences are important indicators of the soil water deficit and are traditionally used for allocating water resources among farmers of a village community. Here we present a simple, inexpensive soil wetness classification scheme based on qualitative indicators which one can see or touch on the soil surface. It incorporates the local farmers' knowledge on the best soil moisture conditions for seeding and brick making in the semi-arid environment of the study site near Arusha, Tanzania. The scheme was tested twice in 2014 with farmers, students and experts (April: 40 persons, June: 25 persons) for inter-rater reliability, bias of individuals and functional relation between qualitative and quantitative soil moisture values. During the test in April farmers assigned the same wetness class in 46% of all cases while students and experts agreed in about 60% of all cases. Students who had been trained in how to apply the method gained higher inter-rater reliability than their colleagues with only a basic introduction. When repeating the test in June, participants were given improved instructions, organized in small sub-groups, which resulted in a higher inter-rater reliability among farmers. In 66% of all classifications farmers assigned the same wetness class and the spread of class assignments was smaller. This study demonstrates that a wetness classification scheme based on qualitative indicators is a robust tool and can be applied successfully regardless of experience in crop growing and education level when an in-depth introduction and training is provided. The use of a simple and clear layout of the assessment form is important for reliable wetness class assignments.

scholarly journals Qualitative soil moisture assessment in semi-arid Africa – the role of experience and training on inter-rater reliability

2015 ◽  
Vol 19 (8) ◽  
pp. 3505-3516 ◽  
Author(s):  
M. Rinderer ◽  
H. C. Komakech ◽  
D. Müller ◽  
G. L. B. Wiesenberg ◽  
J. Seibert
Keyword(s):  
Soil Moisture ◽  
Classification Scheme ◽  
Functional Relation ◽  
Soil Surface ◽  
Arid Environment ◽  
Rater Reliability ◽  
Moisture Conditions ◽  
And Training ◽  
Semi Arid

Abstract. Soil and water management is particularly relevant in semi-arid regions to enhance agricultural productivity. During periods of water scarcity, soil moisture differences are important indicators of the soil water deficit and are traditionally used for allocating water resources among farmers of a village community. Here we present a simple, inexpensive soil wetness classification scheme based on qualitative indicators which one can see or touch on the soil surface. It incorporates the local farmers' knowledge on the best soil moisture conditions for seeding and brick making in the semi-arid environment of the study site near Arusha, Tanzania. The scheme was tested twice in 2014 with farmers, students and experts (April: 40 persons, June: 25 persons) for inter-rater reliability, bias of individuals and functional relation between qualitative and quantitative soil moisture values. During the test in April farmers assigned the same wetness class in 46 % of all cases, while students and experts agreed on about 60 % of all cases. Students who had been trained in how to apply the method gained higher inter-rater reliability than their colleagues with only a basic introduction. When repeating the test in June, participants were given improved instructions, organized in small subgroups, which resulted in a higher inter-rater reliability among farmers. In 66 % of all classifications, farmers assigned the same wetness class and the spread of class assignments was smaller. This study demonstrates that a wetness classification scheme based on qualitative indicators is a robust tool and can be applied successfully regardless of experience in crop growing and education level when an in-depth introduction and training is provided. The use of a simple and clear layout of the assessment form is important for reliable wetness class assignments.

Hydrological characterization of livestock watering ponds in semi-arid rangelands of the southwestern Iberian Peninsula

2020 ◽  
Author(s):  
Ubaldo Marín-Comitre ◽  
Susanne Schnabel ◽  
Manuel Pulido-Fernández
Keyword(s):  
Water Supply ◽  
Iberian Peninsula ◽  
Water Availability ◽  
Catchment Area ◽  
Aerial Photographs ◽  
Antecedent Rainfall ◽  
Wet Season ◽  
Pond Size ◽  
Semi Arid

&lt;p&gt;Watering ponds are the main source of drinking water supply for livestock in the rangelands of the SW Iberian Peninsula. Most of these ponds consist of small earth dams which collect surface runoff from intermittent streams, with pond sizes rarely exceeding 1 ha. Understanding the hydrological functioning of this type of infrastructures is crucial for an efficient water management in extensive livestock farms, especially in semi-arid areas, where water resources are often scarce.&lt;/p&gt;&lt;p&gt;In this line, we have analysed the temporal patterns of water availability in a sample of representative livestock watering ponds in the SW Iberian Peninsula, being the objectives (1) to determine the influence of temporal rainfall variability on water availability in the ponds; (2) to examine the influence of factors such as pond size and catchment area on the effectiveness of the ponds, understood as their capacity to keep water during dry periods; and (3) to suggest minimum values for those factors, which can serve as a guide for the design of watering ponds in comparable rangeland areas. The applied methodology was primarily based on the analysis of aerial photographs and rainfall data available from public sources, requiring only few field measurements, and could therefore be used in areas with data scarcity.&lt;/p&gt;&lt;p&gt;High correlation coefficients were obtained between the water availability observed in the ponds and the antecedent rainfall at several time scales, evidencing the principal role of precipitation in the hydrological dynamics of these infrastructures in the study area. The accumulation periods (AP) of antecedent rainfall that best explained the hydrological response of the ponds depended largely on pond size. In those ponds whose maximum flooded area (A&lt;sub&gt;max&lt;/sub&gt;) was less than 2000 m&lt;sup&gt;2&lt;/sup&gt;, water availability in the ponds was greatly influenced by AP between 2 and 5 months, while for the ponds larger than 2000 m&lt;sup&gt;2&lt;/sup&gt;, the best correlations were obtained for AP greater than 6 months. These results highlight the key role of the size of the ponds in their effectiveness. Thus, since the dry season usually lasts in the study area for 3-4 months, the large ponds (A&lt;sub&gt;max&lt;/sub&gt; &gt; 2000 m&lt;sup&gt;2&lt;/sup&gt;) could remain operational throughout the summer, if it rains enough during the wet season and if their watersheds are large enough to allow a sufficiently high pond water level to be reached at the end of the wet season. In relation to the latter, the analyses carried out led us to suggest, for the study area, a minimum value of the catchment-area/pond-capacity ratio around 100 m&lt;sup&gt;-1&lt;/sup&gt;.&lt;/p&gt;&lt;p&gt;Moreover, the analysis of the water availability observed in the ponds under drought conditions (i.e., with an antecedent rainfall substantially lower than normal for the corresponding time of year) revealed a high vulnerability to droughts in most of the ponds, which limits their use as the sole source of water supply in many farms.&lt;/p&gt;

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