Restoring degraded landscape, managing soil and water resources are important for human well-being. Hillslope management and bioengineering, reforestation, and torrent control work using transverse structures, such as check dams and more recently open check dams, are becoming more common to mitigate soil erosion and torrential hazards. Such techniques are particularly important as they control the flux of water, sediments, nutrients, and other solutes from headwaters to downstream in any watershed management. The design and criteria of the check dams are also facing challenges due to complex hydrological, geological, and biological processes that affect water and sediment transport over a wide range of spatial and temporal scales. However, there are still lack of long term monitoring and sufficient understanding on the effects of soil and water conservation techniques on soil erosion processes, vegetation restoration, and torrential hazards control. Integrated watershed management also becomes increasingly crucial to mitigate the unprecedented impacts of environmental changes (e.g. climate, land-use changes). In this fourth consecutive year of organizing the session during EGU, we welcome studies that focus on soil conservation techniques from hillslopes to watershed scale. Any contributions to the understanding of soil erosion control and sediment transport management based on detailed field monitoring, high-quality laboratory works, mathematic models and effectiveness assessment methods are welcomed. In particular, we propose an approach to join and share scientific and technical studies from all around the world related to the legacy effects of check-dams and the potential of open check dams, highlighting the role of complex interactions between ecological elements, geomorphic processes and engineering activities.

Public information:
Online Chat Schedule

08:30 (14:30 Beijing Time)
WELCOME to SSS2.9 online chat by convener team

08:32 (14:32) (Chairperson: Yang Yu)
D2135 | EGU2020-1236
Influence of Check Dams on Flood and Erosion Dynamic Processes of a Small Watershed in the Loss Plateau
Shuilong Yuan, Guoce Xu, Peng Shi, and Kexin Lu

08:40 (14:40) (Chairperson: Yang Yu and Peng Li)
D2136 | EGU2020-1361
Understorey vegetation drives surface runoff and soil loss in teak plantation-based system of Northern Laos
Layheang Song, Laurie Boithias, Oloth Sengtaheuanghoung, Chantha Oeurng, Christian Valentin, Phabvilay Sounyafong, Anneke de Rouw, Bounsamai Soulileuth, Norbert Silvera, Alain Pierret, and Olivier Ribolzi

08:48 (14:48) (Chairperson: Manuel Esteban Lucas Borja and Peng Li)
D2137 | EGU2020-1690
The Topography Meter: a measurement system applicable for gravity-erosion experiments using a novel 3D surface measuring technique
Xiangzhou Xu, Feilong Xu Xu, Wenzhao Guo, and Chao Zhao

08:56 (14:56) (Chairperson: Manuel Esteban Lucas Borja)
D2138 | EGU2020-2066
Distribution of soil organic carbon impacted by land-use change and check dam on the Loess Plateau of China
Peng Shi, Yan Zhang, Kexin Lu, Zhaohong Feng, and Yang Yu

09:04 (15:04) (Chairperson: Guillaume Piton)
D2140 | EGU2020-4738
Alternative approach for works controlling stony debris flows
Carlo Gregoretti, Matteo Barbini, Martino Bernard, and Mauro Boreggio

09:12 (15:12) (Chairperson: Manuel Esteban Lucas Borja and Peng Li)
D2143 | EGU2020-7441
Soil water flow behavior of abandoned farmland restored with different vegetation communities in the Loess Plateau of China
Rui Wang, Zhengchao Zhou, Ning Wang, Zhijing Xue, and Liguo Cao

09:20 (15:20) (Chairperson: Manuel Esteban Lucas Borja)
D2144 | EGU2020-1388
Plant root exerted a stronger positive effect on aggregate stability than soil during plant secondary succession on the Loess Plateau, China
Lie Xiao and Peng Li

09:28 (15:28) (Chairperson: Demetrio Antonio Zema)
D2145 | EGU2020-737
The magnitude of soil erosion of small catchments with different land use patterns under an extreme rainstorm on the Northern Loess Plateau, China
Nan Wang and Juying Jiao

09:36 (15:36) (Chairperson: Demetrio Antonio Zema)
D2146 | EGU2020-1232
Quantitative assessment of check dam system impacts on catchment hydrological response - a case in the Loess Plateau, China
Tian Wang, Zhanbin Li, Jingming Hou, Shengdong Cheng, Lie Xiao, and Kexin Lu

09:44 (15:44) (Chairperson: Demetrio Antonio Zema)
D2147 | EGU2020-1234
Effects of ecological construction on the transformation of different water types on Loess Plateau, China
Binhua Zhao and Zhanbin Li

09:52 (15:52) (Chairperson: Guillaume Piton and Peng Li)
D2150 | EGU2020-4779
Adaptation of the MMF (Morgan-Morgan-Finney) model to Mediterranean forests subject to wildfire and post-fire rehabilitation measures
Demetrio Antonio Zema, Joao Pedro Nunes, and Manuel Esteban Lucas-Borja

10:00 (16:00) (Chairperson: Guillaume Piton)
D2162 | EGU2020-9921
Check dams effects on plant and soil interface immediately after wildfire
Bruno Timóteo Rodrigues, Manuel Esteban Lucas-Borja, Demetrio Antonio Zema, and Yang Yu

10:08 (16:08) (Chairperson: Guillaume Piton)
D2164 | EGU2020-10009
Are site characteristics and channel hydro-morphology related with check dam functioning? A case study in México
Manuel Esteban Lucas-Borja, Bruno Gianmarco Carrà, Demetrio Antonio Zema, and Yang Yu

10:20 (16:20) A brief conclusion and closing SSS2.9 online chat by conveners
The chat SSS2.9 will be available on 05 May, 08:30–10:15 (14:30-16:15, Beijing Time)

Co-organized by GM4/HS13
Convener: Yang YuECSECS | Co-conveners: Peng Li, Manuel Esteban Lucas-Borja, Guillaume PitonECSECS, Demetrio Antonio Zema
| Attendance Tue, 05 May, 08:30–10:15 (CEST)

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Chat time: Tuesday, 5 May 2020, 08:30–10:15

D2134 |
Liding Chen

Linking landscape patterns to specific ecological processes has been and will continue to be a key topic in landscape ecology. However, the traditional landscape pattern analysis by landscape metrics inspired by patch-matrix model (PMM) may be difficult to reach such a requirement, and thus landscape pattern analysis to denote the significance of ecological process is strongly hindered. To find conceptual and methodological innovations integrating ecological processes with landscape patterns is important. In this paper, we proposed a conceptual model, i.e., the source-pathway-sink model (SPSM) by defining the role of each landscape unit to a specific process before conducting landscape pattern analysis. The traditional landscape matrices derived from the patch-matrix model is visual- or geometrical-oriented but lack of linkage to ecological significance. The source-pathway-sink model is process-oriented, dynamic, and scale dependent. This model as a complementary to the patch-corridor-matrix model can provide a simple and dynamic perspective on landscape pattern analysis. Based on the SPSM model, a landscape index was developed in term of the process of soil erosion, and further testified by using on-site measurements. It was found the new landscape index based on SPSM is useful in evaluating the risk of soil erosion from landscape pattern at watershed. Finally, a case study was conducted in the loess hilly areas to define the risk area of soil erosion that will be useful for sustainable land use management and optimization in future.

How to cite: Chen, L.: To link landscape pattern with soil erosion risk at watershed scale based on SPSM model in the loess hilly area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4995, https://doi.org/10.5194/egusphere-egu2020-4995, 2020.

D2135 |
Shuilong Yuan, Guoce Xu, Peng Shi, and Kexin Lu

As an important soil and water conservation engineering measure, check dams have been constructed on a large scale in the Loess Plateau of China. However, their effects on runoff and sediment processes in the basin are still unclear. In this study, the hydrodynamic processes of the Wangmaogou watershed located in the Loess Plateau were simulated, and the influence of check dams on the flood and erosion dynamic processes in this watershed were also evaluated. The results showed that the check dams obviously reduced the flood peak and flood volume and mitigated the flood process. After the dam system was completed, the flood peak and flood volume were reduced by 65.34% and 58.67%, respectively. The erosion dynamic distribution of the main channel in the small watershed was changed to different extents by the different dam type combinations, and the erosion dynamic parameters of the channel decreased most after the dam system was completed, when the velocity and runoff shear stress of the outlet section were reduced by 10.69% and 31.08%, respectively. Additionally, the benefits of sediment reduction were most obvious after the check dam system was completed, with the sediment discharge in the watershed being reduced by 83.92%. The results of this study would provide specific implications for construction and management of check dams in the Loess plateau.

How to cite: Yuan, S., Xu, G., Shi, P., and Lu, K.: Influence of Check Dams on Flood and Erosion Dynamic Processes of a Small Watershed in the Loss Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1236, https://doi.org/10.5194/egusphere-egu2020-1236, 2020.

D2136 |
Layheang Song, Laurie Boithias, Oloth Sengtaheuanghoung, Chantha Oeurng, Christian Valentin, Phabvilay Sounyafong, Anneke de Rouw, Bounsamai Soulileuth, Norbert Silvera, Alain Pierret, and Olivier Ribolzi

Humid tropical mountainous area experiences serious soil erosion due to rapid changes in landuse, sometimes implying erosion prone management practices. In this study, we hypothesized that keeping understorey in teak tree plantation would protect soil and avoid soil erosion. We assessed the effects of 4 management practices in teak tree plantation area on water and soil losses using 6 replicated 1-m2 microplots in four plantations situated in Northern Laos during the wet season of 2017. The landuses in the four plantations were teak without understorey (TNU), teak with low density of understorey (TLU), teak with high density of understorey (THU), and teak with broom grass, Thysanolaena latifolia (TBG). During the wet season of 2017, we monitored surface runoff and soil loss for 22 rainfall events. We also measured some of the teak tree and understorey characteristics (i.e. height and percentage of cover) and the percentage areas of soil surface features (i.e. litter, free aggregates, crusting, etc.). Relationships among these variables was estimated through multiple statistics and regression analyses. We found that runoff coefficient and soil loss were the smallest for THU and TBG: runoff coefficient was 23% for both treatments, and soil losses were 465 and 381 g m-2, respectively. Runoff coefficient and soil loss for TLU were 35% and 1115 g m-2, respectively. We observed the highest runoff coefficient and soil loss under TNU (60%, 5455 g m-2) associated to the highest crusting rate (82%). High runoff coefficient and soil loss under TNU was explained by the kinetic energy of rain drops falling from the broad leaves of the tall teak trees down to bare soil, devoid of plant residues, thus leading to severe soil surface crusting and detachment. Overall, promoting understorey such as broom grass in teak tree plantations would (1) limit surface runoff and improve soil infiltrability, thus increase the soil water stock available for both root absorption and groundwater recharge, and (2) mitigate soil loss and favour soil fertility conservation.

How to cite: Song, L., Boithias, L., Sengtaheuanghoung, O., Oeurng, C., Valentin, C., Sounyafong, P., de Rouw, A., Soulileuth, B., Silvera, N., Pierret, A., and Ribolzi, O.: Understorey vegetation drives surface runoff and soil loss in teak plantation-based system of Northern Laos, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1361, https://doi.org/10.5194/egusphere-egu2020-1361, 2020.

D2137 |
Xiangzhou Xu, Feilong Xu Xu, Wenzhao Guo, and Chao Zhao

Gravity erosion is one of the most remarkable natural hazards in mountainous regions, especially on the Loess Plateau of China. Nevertheless, the measurement of failure mass is very difficult because gravity erosion usually occurs randomly and it combines with hydraulic erosion. Here we present a novel testing technique that could quantitatively measure time-variable gravity erosion on the steep loess slopes. A structured light 3D surface measuring apparatus, the Topography Meter, was designed and manufactured in our laboratory. Dynamic variation of the steep slope relief was monitored under rainfall simulation and the slope deforming process was recorded by a computer video technology. With the help of laser marking, plane figures were vectorially transformed into 3D graphs, thus the shape of target surface was accurately computed. By comparing the slope geometries in the moments before and after the erosion incident on the snapshot images at a particular time, we could obtain the volume of gravity erosion and many other erosion data, including the volume of slide mass, the amount of soil loss eroded by overland flow, etc. A series of calibration tests were conducted and the results showed that the accuracy of this technique was high and sufficient for exploring the mechanism of slope erosion. More than 120 rainfall simulation events were subsequently tested with the apparatus, further confirming its feasibility and reliability.

How to cite: Xu, X., Xu, F. X., Guo, W., and Zhao, C.: The Topography Meter: a measurement system applicable for gravity-erosion experiments using a novel 3D surface measuring technique, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1690, https://doi.org/10.5194/egusphere-egu2020-1690, 2020.

D2138 |
Peng Shi, Yan Zhang, Kexin Lu, Zhaohong Feng, and Yang Yu

Vegetation restoration, terrace and check dam construction are the major measures for soil and water conservation on the Loess Plateau. These effective measures of stabilizing soils have significant impacts on soil organic carbon (SOC) distribution. To understand the impact of land-use changes combined with check dam construction on SOC distribution, 1060 soil samples were collected across a watershed on the Loess Plateau. Forestland, shrubland and terrace had significant higher SOC concentrations in the 0-20 cm soil layer than that of sloping cropland.    Land use change affects the process of runoff and sediment transportation, which has an impact on the migration and transformation of soil carbon. The soil erosion of sloping farmland is the most serious, and the maximum annual erosion rate is as high as 10853.56 t·km-2. Carbon sedimented in the dam land was mainly from sloping cropland, and this source percentage was 65%. The application of hydrological controls to hillslopes and along river channels should be considered when assessing carbon sequestration within the soil erosion subsystem. 

How to cite: Shi, P., Zhang, Y., Lu, K., Feng, Z., and Yu, Y.: Distribution of soil organic carbon impacted by land-use change and check dam on the Loess Plateau of China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2066, https://doi.org/10.5194/egusphere-egu2020-2066, 2020.

D2139 |
Jiangang Chen, Huayong Chen, and Xiaoqing Chen

Check dams are transverse structures build across gullies and they are very important engineering measure in soil restoration hazard mitigation. After three successive earthquakes in China, a considerable number of solid material was deposited in gullies. With the extreme rainfall, a numerous of flood and debris flow events were trigged, some of them caused serious secondary disasters. In the past 12 years after the Wenchuan earthquake, based on the debris-flow prevention method by controlling debris-flow magnitude and avoiding blocking river, a series of check dams were constructed to regulate the water and soil erosion. The operation status of check dams needs to be investigated and summarize the engineering practice experience. Based on the results of field investigation, the shape and size characteristics of the dam opening were analyzed, and then established a classification system of the opening clogging types. Moreover, in August 20, 2019, Flash floods and mudslides occurred in Wenchuan County, causing more than 30 people dead, buried the G213 highway, and damaged a bridge. These disasters bring new thinking for future hazard mitigation. Geotechnical measures can quickly reduce the disaster risk of flash flood and debris flow, and now it has formed a set of perfect design standards. However, the disaster mitigation effect of the vegetation measures are not fully studied. Thus, the integrated disaster mitigation effect of the above two methods will be investigated in the future work.

How to cite: Chen, J., Chen, H., and Chen, X.: Planning method and application case of debris-flow check dams in water and soil conservation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2851, https://doi.org/10.5194/egusphere-egu2020-2851, 2020.

D2140 |
Carlo Gregoretti, Matteo Barbini, Martino Bernard, and Mauro Boreggio

Many sites of the Dolomites are threatened by channelized debris flows: solid-liquid surges initiated by the entrainment of large quantities of sediments into the abundant runoff at the head of channel incised on fans, can dramatically increase their volume along the downstream routing. This is the case of the Rovina di Cancia site where solid-liquid surges forming in the upper part of the basin can increase their volume up and over 50000 m3, seriously impacting the downstream village of Borca di Cadore. The debris-flow channel ends just upstream the village that in the past was hit by four debris flows (three in the recent years) that caused victims and destructions. Control works built until now are not sufficient to protect the village from high magnitude debris flows and a definitive solution calls to be planned. Present works are a flat deposition area, 300 m downstream the initiation area, an open dam under construction downstream it, and  two retention basins at the end of the channel. Between the open dam and the upstream retention basin, there are the rest of eight check-dams made of gabions, built in the 60s and progressively damaged or destroyed by the debris flows occurred after their construction. This series of check-dams limited the entrainment of solid material and the occurrence of localized scours. The initial plan is the substitution of the check-dams with concrete structures and the widening of the dowsntream retention basin through the raising of high elevation embankment downstream it and the following demolition of the actual dyke. Finally, a channel crossing the village and national route on the valley bottom will deliver the fluid phase from the widened basin to the Boite river. All these control works have a very high cost for construction and maintenance and severely impact the village with the presence of a non-negligible residual risk. These drawbacks call for an alternative solution that is searched looking at to the morphology. Downstream of the open dam and on its right side, there is a deep impluvium that ends on a large grass sloping area. The novel solution requires the construction of a channel through the right high bank that deviates the debris flow into the impluvium. The impluvium, widened through the excavation of the surrounding slopes, is closed at the outlet by  an open dam. Downstream the open dam, a channel will lead to a retention basin, where most of storage volume is obtained from the excavation of the grass sloping area, limiting the elevation of the dykes At the end of this basin an open dam will deliver the debris-flow fluid part to a channel passing under the national route and joining the Boite river. Such a solution composed of a deviatory channel, two retention basins (the deep impluvium and that excavated on the sloping grass area) and the channels between and downstream them, has quite a lower costs of construction and maintenance, eliminating the impact on the village because occupying uninhabited areas without interrupting the main roads.

How to cite: Gregoretti, C., Barbini, M., Bernard, M., and Boreggio, M.: Alternative approach for works controlling stony debris flows, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4738, https://doi.org/10.5194/egusphere-egu2020-4738, 2020.

D2141 |
Yu Liu, Liang Zhao, and Xiubo Yu

Soil erosion, a widely-occurring phenomenon in the terrestrial environment, affects land productivity and infrastructure security negatively both on-site and off-site. Therefore, soil erosion control services (SECS) are one of the most fundamental ecosystem services for human well-being. Although previous SECS assessments elaborate the benefits from preventing on-site soil erosion and soil loss comprehensively, the off-site benefits remain vague. They are usually estimated only through multiplying the capacity of on-site soil erosion prevention by a land-use-based, and spatially consistent, allocation coefficient. The corresponding overestimation, item omission, and inability to represent the spatial heterogeneity of SECS may lead to great uncertainties. In addition, the SECS decay with travel distance is not well represented, because of a neglect of the cascading nature of SECS formation and its delivery. Here, to address these deficiencies, a cascade framework for SECS assessment is developed that incorporates the concept of sedimentological connectivity over the landscape. This approach quantifies both the on-site soil erosion prevention and mitigation of sediment delivery over the landscape, based on an understanding of the cascading nature of soil erosion and sediment delivery, by referring to the framework of WATEM/SEDEM that potentially reveals the sedimentological connectivity over landscape. A monetized valuation of SECS delivered to local communities was derived by employing a land-use based replacement cost technique, which takes cultivated land units as a SECS receiver and conveyer. The approach was applied in a loess catchment located in the middle Yellow River basin, China as a case study. For this watershed, with an area of 54.2 km2, the gross soil erosion reduction was up to 156.93 × 104 t; the reduction of sediment input was 11.28 × 104 t; and the reduction in gross sediment export is up to 181.34 × 104 t. The monetized value delivered to utilized land units was 910.13 × 104 CNY. The approach described provides a tool that specifically addresses the SECSs directly useful to humans, contributes to quantifying the soil erosion control services provided by the landscape, and improves the reliability of evaluating SECS.

How to cite: Liu, Y., Zhao, L., and Yu, X.: A sedimentological connectivity approach for assessing on-site and off-site soil erosion control services, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13203, https://doi.org/10.5194/egusphere-egu2020-13203, 2020.

D2142 |
Sebastien Salvador-Blanes, Clément Girault, Thomas Rochereau, Arthur Gaillot, Frédéric Darboux, Blandine Lemercier, Didier Michot, and Nicolas Saby

The Slake mobile app measures the aggregate stability by rapid immersion in water. It is a particularly interesting tool to allow a cost-efficient determination of soil structural stability. The Slake app has proven its efficiency at large scale (New South Wales state, Australia). Its application at a more local level (e.g. small watersheds) could be of particular interest to farmers and local stakeholders to identify areas of sensitivity to soil slaking, in order to implement mitigation strategies in the most appropriate areas to prevent from soil erosion. The aim of this study was to test the Slake app at the plot and the watershed scales to test its applicability and robustness. The studied watershed is the 25 km² Louroux catchment, located in central France. This catchment is typical of intensively cultivated lowland catchments. Despite a very low slope (<0.4%), erosion processes have been shown as significant, either through soil surface erosion or tile drainage exports. Slaking values have been measured in the laboratory on undisturbed soil surface aggregates collected at 52 locations within the catchment, using a balanced sampling. The same methodology has been applied within a 5 ha plot on 52 sampling points. The aggregate stability was measured with the app simultaneously on three aggregates. This measurement was repeated 3 times for each sampling location. Therefore, 9 slaking indices can be extracted for each soil sampling location, allowing for a computation of the index variability at each sampling location. Besides, 13 samples for the plot and the catchment have been selected to measure soil structural stability by a normalized method (Mean Weight Diameter of soil aggregates after wet sieving, ISO 10930). Preliminary results show a variable heterogeneity of the slaking index measured at a single location. The origin of this heterogeneity (measurement errors, sample variability…) is discussed. The correlation with the normalized method is explored and the spatial structure of the slaking index over the two studied scales is presented.

How to cite: Salvador-Blanes, S., Girault, C., Rochereau, T., Gaillot, A., Darboux, F., Lemercier, B., Michot, D., and Saby, N.: Testing the Slake mobile app at the local scale to explore the spatial variability of soil structural stability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17159, https://doi.org/10.5194/egusphere-egu2020-17159, 2020.

D2143 |
Rui Wang, Zhengchao Zhou, Ning Wang, Zhijing Xue, and Liguo Cao

Natural vegetation succession in abandoned farmlands simulate the changes in near surface soil characcteristics over the Loess Plateau of China, and hence likely induce temporal variation in the distribution and the movement of soil water in soil layers. In order to assess the effect of the natural vegetation succession on soil water flow behavior, four vegetation communities at different stages of sucession (Artemisia scoparia, Artemisia sacrorum, Bothriochloa ischaemum, Periploca sepium Bunge) in Fangta watershed of Yan River were selected and dye tracer experiments were performed. Both the soil physicochemical properties (e.g., soil bulk density, the particle size, water stable aggregate (>0.25 mm) content, and soil organic matter) and the root systems (e.g., root mean diameter, root mass density, root surface area, and root volume density) tended to increase along with vegetation sucessional development. Results of the dye tracer experiment and the image analysis indicated that the preferential flow was the dominant type in the four field sites. Compared to the site in early stage of sucession, the preferential flow proportion (FFP), preferential infiltration volume (PIV), and the contribution of the preferential infiltration to the total infiltration (Con) in the late stage enhanced by 6.65-7.34 times, 2.73-4.08 times, and 2.52-3.75 times, respectively. Correlation analysis suggested that the plant roots and their morphometric features played more important role on the preferential flow in comparison with the soil physicochemical properties. The abundant lateral root and the steeper slope may have caused the presence of lateral flow. Along with increasing degree of preferential flow, the spatial variability of the soil water through the vertical soil profiles increase during the process of restoration and succession of vegetation communities. Our study demonstrated the improvement of the preferential flow in the abandoned farmland during natural vegetation restoration helped soil water storage in the deep soil layer.


How to cite: Wang, R., Zhou, Z., Wang, N., Xue, Z., and Cao, L.: Soil water flow behavior of abandoned farmland restored with different vegetation communities in the Loess Plateau of China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7441, https://doi.org/10.5194/egusphere-egu2020-7441, 2020.

D2144 |
lie xiao and Peng Li

The stability of soil aggregates is an indicator of restoration of soil in degraded ecosystems. A multitude of factors such as properties of plant roots and soil have been suggested to contribute to aggregate stability, but little information is available on the relative importance of these factors in temperate grass zones. We examined how root and soil properties modified aggregate stability along a gradient of secondary succession grassland on the Loess Plateau in China. We selected three cropland abandoned for 3, 10, and 16-year and measured the distribution of aggregates, mean weight diameter (MWD), bulk and aggregate-associated soil organic carbon (SOC) and glomalin-related soil protein (GRSP) contents, root biomass density, root length density, and specific root length (SRL). Compared with 3-year site, the amount of large macroaggregates (>2 mm) and aggregate stability (indicated by MWD) at 16-year site increased by 25.6% and 8.5%. The higher MWD contributed the most to the accumulation of SOC in large and small macroaggregates and to the accumulation of GRSPs in microaggregates (<0.25 mm). SRL was significantly positively correlated with MWD. Redundancy analysis (RDA) showed that soil and plant variables together explained 89.1% of the aggregate distribution variation. Partial RDA further revealed that soil variables solely explained 6.4% of the variation, plant root variables explained 47.9% of the variation, and interaction of soil and plant variables accounted for 34.8% of the variation. Our study indicated that increased soil aggregate stability during plant secondary succession depended on both plant roots and aggregate-associated SOC and GRSPs, and plant root exerted a stronger influence on soil aggregate stability than soil. Allowing secondary succession may be a promising strategy for restoring degraded ecosystems on the plateau.

How to cite: xiao, L. and Li, P.: Plant root exerted a stronger positive effect on aggregate stability than soil during plant secondary succession on the Loess Plateau, China , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1388, https://doi.org/10.5194/egusphere-egu2020-1388, 2020.

D2145 |
Nan Wang and Juying Jiao

The characteristics of soil erosion under extreme rainstorm conditions can reflect the effect of ecological restoration measures and the rationality of land use patterns in the region. 12 dam-controlled catchments was selected after an extreme rainstorm event occurred in the northern Shaanxi Province on 25-26 July 2017 (called “7.26” rainstorm). Soil erosion intensity in the 12 catchments was obtained by digging up the sedimentation profiles and measuring the sedimentation areas. Using digital orthophoto map and digital terrain model by Unmanned Aerial Vehicle to obtain land-use types and their areas, slope gradients and the distance along the flow path to the edge of the downslope and dam-land. Stepwise regression method was used to analyze the main factors affecting catchment erosion intensity. The results showed that the average sedimentation thickness in the 12 damlands ranged from 0.16 m to 1.67 m and the intensity of soil erosion of the 12 catchments varied from 10295 t km-2 to 49227 t km-2. Soil erosion caused by this rainstorm was 10-50 times of the allowable amount of soil erosion in the Loess Plateau region (1000 t km-2.a) issued by Ministry of Water Resource of the People’s Republic of China (MWR). Stepwise regression analysis shows that, the closer the shape of a catchment to the circle is, the larger the area of slope-cropland in inter-gully land is or the closer the distance between slope-cropland and the dam-land is, the larger the erosion modulus in the catchment would be. What’s more, the presence of cement road up the valleys shoulder line reduced the modulus of soil erosion. Theses findings indicated that the existing ecological conditions in the dam-controlled catchments are not able to resist extreme rainstorm erosion effectively. Optimizing the distribution of land use types in catchments should be the focus of soil erosion control.

How to cite: Wang, N. and Jiao, J.: The magnitude of soil erosion of small catchments with different land use patterns under an extreme rainstorm on the Northern Loess Plateau, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-737, https://doi.org/10.5194/egusphere-egu2020-737, 2020.

D2146 |
Tian Wang, Zhanbin Li, Jingming Hou, Shengdong Cheng, Lie Xiao, and Kexin Lu

The purpose of this study is to investigate the impact of check dams on catchment hydrological response in a small catchment on the Chinese Loess Plateau by applying a GAST (GPU Accelerated Surface-water and Transport model) numerical model at 2 m resolution DEM. The results showed that check dams significantly increase the so-called runoff lag times (lag to generation, lag to peak and lag to end of runoff) at the channel outlet compared to catchments without check dams. Furthermore, the peak runoff discharge at the catchment outlet without check dams decreased by 93.0% compared to with check dams. The total outlet discharge, surface water stored, and infiltration were respectively 20.1%, 74.9% and 5.0% of the total precipitation in the check dam catchment, while 75.4%, 22.6% and 2.0% in the system without check dams. Installation of check dams also altered the spatial water distribution of maximum discharge, moving the occurrences of maximum discharge further upstream and, thus, increasing safety downstream. Channel connectivity was found to have a direct relationship with peak discharge and with discharge volume at the basin mouth. In conclusion, implementing check dams significantly and effectively mitigated flood processes and increased runoff infiltration upstream.

How to cite: Wang, T., Li, Z., Hou, J., Cheng, S., Xiao, L., and Lu, K.: Quantitative assessment of check dam system impacts on catchment hydrological response - a case in the Loess Plateau, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1232, https://doi.org/10.5194/egusphere-egu2020-1232, 2020.

D2147 |
Binhua Zhao and Zhanbin Li

Water is the most essential resource for the ecological and biological survival of organisms as well as being an important strategic socio-economic factor. Stable isotopes of δD and δ18O in water are important indicators of hydrological and ecological process. In this study, temporal and spatial variations in δD and δ18O and transformations between three water bodies (precipitation, stream water, and groundwater) under ecological construction were studied in two contrasting watersheds of the Wuding River, China. In order to understanding the spatial and temporal variation of stable isotopes and water transmission times (WTT) under ecological construction, a total of 1028 water samples were collected from the 30 sites, and 79 precipitation samples were collected at the weather station. The results show that variation range of three water bodies occurred in the order
precipitation>stream water>groundwater, the local meteoric water line was above the level of the last two, and the isotopic composition of stream water and groundwater in controlling watershed is more enriched than that in natural watershed. WTT from precipitation to stream water in Jiuyuangou were 1.53 times those of Peijiamao. Similarly, WTT from precipitation to groundwater was about 7.6 times than that form precipitation to stream water. Supply ratios exhibited obvious seasonal variation. Precipitation and groundwater recharged stream water mostly in the dry season, while precipitation and stream water recharged groundwater during the wet season. Overall, this study shows that ecological construction measures extend WTTs and enhance water evaporation and fractionation. The results of this research are significant as they enhance our understanding of water transformation on the Loess Plateau under ecological construction.

How to cite: Zhao, B. and Li, Z.: Effects of ecological construction on the transformation of different water types on Loess Plateau, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1234, https://doi.org/10.5194/egusphere-egu2020-1234, 2020.

D2148 |
Peng Li, Kunxia Yu, and Lie Xiao

Check dam is widely used in the soil erosion control in the gully on the Loess Plateau of China. Check dam has significant effects in sedimentation, erosion control, land formation, water storage, and vegetation restoration. This result shows that the main dams and medium-sized dams on the Loess Plateau had deposited 5.12 million tons of sediment by the end of 2011, reducing sediment transportation to the Yellow River. The check dam system decreases the probability of gravity erosion. Check dams increases cropland in the gully-hilly area of the Loess Plateau, thus increases grain production. The check dam project is a carbon pool. On the Loess Plateau, 123 million tons of soil carbon is storaged in the check dam, accounting for 17.08% of the carbon sequestration in afforestation projects in China from 1994 to 1998. Check dam construction increases regional vegetational coverage, and the NDVI in the Dali River watershed increased by 28.4% after the dam project. The results provide a scientific basis for the assessment of the eco-environmental benefit of check dam on the Loess Plateau of China.

How to cite: Li, P., Yu, K., and Xiao, L.: Check dam is an effective engineering for soil and water conservation, carbon sequastration on the Loess Plateau of China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2262, https://doi.org/10.5194/egusphere-egu2020-2262, 2020.

D2149 |
Haiqiang Gao and Shuguang Liu

China has implemented an ambitious ecological project Grain for Green Project (GGP) on the Loess Plateau (LP) at the end of last century. The GGP was to increase vegetation coverage, reduce soil and water erosion and store Carbon by converting croplands on steep slopes barren hills and wasteland to forests. Assessing the ecological effects of GGP correctly could improve vegetation restoration activities worldwide. In this study, two major ecological indicators (vegetation restoration and soil & water conservation) were used to evaluate the ecological benefits of GGP from 1982 to 2017. Our results show that the vegetation growth for most pixels of LP region have significantly increased at 21 century, annual growth rates of fraction of absorbed photosynthetically active Radiation (FPAR) in spring, summer, autumn and active growing season are 1.39, 4.49, 2.14 and 1.47, respectively. For leaf area index (LAI), these growth rates are 6.01, 20.06, 8.11 and 6.90, respectively. And for normalized difference vegetation index (NDVI), growth rates are 6.30, 25.46, 7.99 and 20.43, respectively. While the soil and water condition has differently changed, annual growth rates of soil moisture (SM) are 4.46, 2.79 and 2.30 for summer, active growing season and whole year, respectively. The coordinated responses of vegetation and soil & water condition suggest that the interaction between organisms (vegetation, animal and human) and environment (soil, water and so on) in the process of vegetation restoration should be further recognized to evaluate the benefits of ecological engineering more comprehensively.

How to cite: Gao, H. and Liu, S.: The trade-off between vegetation restoration and soil & water conservation in Loess Plateau, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13809, https://doi.org/10.5194/egusphere-egu2020-13809, 2020.

D2150 |
Demetrio Antonio Zema, Joao Pedro Nunes, and Manuel Esteban Lucas-Borja

The hydrological effects of wildfire are very difficult to predict in Mediterranean forests, due their intrinsic semi-arid climate and soil characteristics. The Morgan-Morgan-Finney (MMF) model has shown generally accuracy and reliability in predicting surface runoff and soil erosion in several environmental contexts. In spite of its ease use and limited input requirements, few applications exist in Mediterranean forests with or without post-fire rehabilitation measures; therefore, its applicability to those conditions may be questionable without purposed verifications.

To fill this gap, the MMF model has been verified at the seasonal and plot scales in areas affected by a wildfire of a Mediterranean forest, with and without post-fire straw mulch treatment. The application of MMF with input parameters set up according to the original guidelines of the model’s developers led to poor performance in every soil condition. Subsequently, the model has been adapted to burned soils and Mediterranean climate characteristics, introducing changes in input data for both the hydrological and erosive components (seasonal values of evapotranspiration, reduction of the soil hydrological depth, including soil water repellency effects in burned soils, and modelling erosive precipitation only). By these adaptations, MMF was able to predict seasonal runoff volumes and soil loss with good reliability in all the experimented conditions.  

This modelling experiment has shown the capacity of the MMF model to simulate the seasonal hydrological response of the burned and mulched soils of Mediterranean forests. Therefore, the potential applicability of the model is promising as a management tool for predicting and controlling the erosion risk in semi-arid forest ecosystems threatened by wildfire as well as to evaluate the efficiency of post-fire treatments.

How to cite: Zema, D. A., Nunes, J. P., and Lucas-Borja, M. E.: Adaptation of the MMF (Morgan-Morgan-Finney) model to Mediterranean forests subject to wildfire and post-fire rehabilitation measures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4779, https://doi.org/10.5194/egusphere-egu2020-4779, 2020.

D2151 |
Dengshan Zhang, Haijiao Wang, and Lihui Tian

Wind regime, sand drift potential and sand transport amount are important indicators to evaluate regional blown sand activities. This paper took Ketu sandy land on the eastern shore of Qinghai Lake as study area. The sand transport amount data were collected monthly in 2013-2014 and 2016-2017 with 16-azimuth sand collector, and data of local wind velocity and direction were used to compare and analyze the typical blown sand activities. The results were as follows: (1) In 2013-2014, the mean wind velocity in the study area was 2.79m/s and the frequency of sand-driving wind was 6.76%. While they were 2.63m/s and 6.13% in 2016-2017, respectively. (2) The directions of the sand-driving wind in two years were similar, clearly from WSW-WNW and ESE-SSE. The frequency of western wind increased whereas the frequency of southeastern wind decreased. (3) The seasonal variation of sand drift potential in two years were similar with the largest in spring and the smallest in summer. According to the annual variation trend of sand drift potential, the study area was belonging to low wind energy environment. (4) There is a significant difference in sand transport amount between the two years. The amount in 2016-2017 was 77.18kg less than that in 2013-2014, while the distribution of sand transport amount was similar. The increase of vegetation coverage in this area is the main reason for the decrease of sand transport amount.

How to cite: Zhang, D., Wang, H., and Tian, L.: Characteristics of blown sand activities in sandy land on the eastern shore of the Qinghai Lake, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1745, https://doi.org/10.5194/egusphere-egu2020-1745, 2020.

D2152 |
Xiaoxia Zhang, Xiang Li, Yipeng Liang, and Tonggang Zha

Soil organic carbon (SOC) redistribution along the Loess slope under the effect of soil erosion plays an important role in understanding mechanism of SOC spatial distribution and turnover, hence to its effects on global carbon cycle. Vegetation restoration has been taken as an effective method to alleviate soil erosion on the Loess Plateau, while little research focused on the impact of vegetation restoration on the redistribution processes, especially the spatial distribution and stability of SOC. Here, we quantified the SOC stock and pool distribution on the loess slopes along geomorphic gradients under naturally regenerating forests (NF) and artificial black locust plantation (BP), using corn field as a control (CK).The results were as follows:  (1) vegetation restoration, especially NF, effectively slowed down the migration of SOC resulting from soil erosion and reduced the heterogeneity of SOC distribution. The ratios of topsoil SOC in the sedimentary area to the stable area were 109%, 143%, and 210% under the NF, BP, and CK, respectively. And (2) Vegetation restoration reduced the loss of labile organic carbon by alleviating the loss of dissolved organic carbon (DOC) and easily oxidized organic carbon (EOC) during migration. Both DOC/SOC and EOC/SOC ratios under NF and BP presented far less differences between the sedimentary and erosion zones than CK.A schematic diagram of SOC cycle patterns and redistribution along the loess slope under vegetation restoration based on our findings and discussions. The results suggested that vegetation restoration in the Loess slope, NF in particular, was an effective means for alleviating the redistribution and spatial heterogeneity of SOC and reducing soil erosion. Information from this study is useful for understanding the carbon cycles in restored ecosystems and evaluating the ecosystem services of natural and managed forests in soil erosion control and carbon sequestration.

How to cite: Zhang, X., Li, X., Liang, Y., and Zha, T.: Effects of vegetation restoration on soil organic carbon redistribution along the Loess slope, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2481, https://doi.org/10.5194/egusphere-egu2020-2481, 2020.

D2153 |
Haiyan Zheng and Chiyuan Miao

Over the past 50 years, a series of soil and water conservation measures have been implemented on the Loess Plateau, including biological, engineering, and agricultural measures. As a result, water discharge and sediment load on the plateau have undergone significant changes. In this study, we compared the water discharge and sediment load at more than 100 hydrological stations across the Loess Plateau during the period 2008–2016 (P2) with the water discharge and sediment load during the period 1971–1987 (P1), and detected the main sources of sediment in each of the two periods. We then performed an attribution analysis to quantify the influence of different factors on the changes in sediment load. We found the following results: (1) Water discharge was reduced by 22% in P2 compared with P1, whereas the sediment load was reduced by 74%. (2) Sediment resources are mainly concentrated between Toudaoguai and Tongguan stations: this region contributed more than 88% of the total sediment load at the terminal station (Huayuankou station) in both P1 and P2. (3) When considering only the changes in sediment concentration on the Loess Plateau, we conclude that the contribution of human activities was greater than 72%. This study provides a detailed description of the temporal and spatial variations in water and sediment across the Loess Plateau, providing a reliable reference for the future development of ecological soil and water conservation measures on the Loess Plateau.

How to cite: Zheng, H. and Miao, C.: Change in water discharge and sediment load on the Loess Plateau, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3080, https://doi.org/10.5194/egusphere-egu2020-3080, 2020.

D2154 |
HaiBin Liang and Zongshan Li

Soil moisture is the foundation of ecosystem sustainability in arid and semi-arid regions, and the spatial–temporal details of soil moisture dynamics of afforested areas can benefit for land use management in watershortage regions such as the Loess Plateau of China. In this study, spatial–temporal variations in soil moisture under Robinia pseudoacacia plantations on the Loess Plateau were analyzed. A total of 147 observations of soil moisture content (SMC) data to a depth of 500 cm soil profile were collected in 23 counties via field transect surveys and analyses of published literature. The results suggested that (1) the depth-averaged SMC was generally lower under forest sites than under cropland, both in the shallow layers and in the deep profiles. This finding implied that, compared with the native vegetation, the introduced R. pseudoacacia plantations caused intense reductions in soil moisture. (2) SMC was positively correlated with climatic factors (mean annual precipitation (MAP), mean annual temperature (MAT), and the Palmer drought severity index (PDSI)), indicating that the SMC under R. pseudoacacia plantations was highly consistent with the hydrothermal conditions at the regional scale. (3) The decreasing amplitude of SMC was linearly related to the increasing number of restoration years, especially in the areas below the 500–550 mm precipitation threshold. This finding showed that the restoration ageing sequence was an influential factor that affected the regional SMC variation in R. pseudoacacia plantations on the Loess Plateau. Our results suggest that afforestation activities should be avoided if the local total precipitation is insufficient for replenishing the soil moisture and that local tree species with a lower demand for water resources should be considered a top priority for further afforestation of the Loess Plateau.

How to cite: Liang, H. and Li, Z.: Soil moisture decline following the plantation of Robinia pseudoacacia forests: Evidence from the Loess Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4096, https://doi.org/10.5194/egusphere-egu2020-4096, 2020.

D2155 |
Zongshan Li and Haibin Liang

Soil moisture is a key factor affecting vegetation growth and survival in arid and semi-arid regions. Knowledge of deep soil moisture dynamics is very important for guiding vegetation restoration and for improving land management practices on the water-limited Loess Plateau. Temporal changes and vertical variations in deep soil moisture (at soil depths of 0–600 cm) combined with soil moisture availability were monitored in situ under Caragana korshinskii shrubs of different ages (named CK-10a, CK-20a and CK-35a) in the Loess hilly region during the growing season of 2013. The soil moisture content (SMC) under C. korshinskii shrubs of different ages was highly consistent with the seasonal precipitation variations and generally decreased as follows: CK-10a > CK-20a > abandoned land > CK-35a. The SMC varied greatly over time during the growing season (P < 0.01), decreasing from April to May and then slowly increasing with some fluctuation from June to October. The SMC drastically decreased with depth from 0–300 cm and then gradually increased with some fluctuation from 300–600 cm. A critical turning point and transition zone connecting the shallow and deep soil moisture occurred at 200–300 cm. Therefore, the soil profile was divided into active, secondary active and relatively steady soil layers in terms of soil moisture. The SMC fluctuated at depths of 0–100 cm and 300–400 cm and was relatively stable in the deeper soil layers. The amount of available soil moisture gradually decreased as the forest stand age increased, especially at CK-35a, where most of the soil moisture was unavailable for plant use. In addition, our study indicates that a large-scale restoration strategy with pure shrubland or woodland may not be suitable for soil moisture recovery in arid environments.

How to cite: Li, Z. and Liang, H.: Soil moisture dynamics under Caragana korshinskii shrubs of different ages in Wuzhai County on the Loess Plateau, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4107, https://doi.org/10.5194/egusphere-egu2020-4107, 2020.

D2156 |
yuting cheng, peng li, Guoce Xu, and yixin zhang

Soil erosion is one of the primary environmental problems in China, and it can lead to serious water, soil, and nutrient losses. However, the mechanism of action of the dynamic factors of erosion on nitrogen (N) and phosphorus (P) loss remains unclear. In this study, a series of laboratory experiments were carried out to characterize the N and P loss and its influencing factors under freeze–thaw conditions. Two slope treatments (i.e. LS: loess and FTS: freeze–thaw soil) and five soil water content (SWC) (i.e. 10%, 15%, 20%, 25% and 30%) were considered. The results showed that the total runoff was higher under 30% SWC and lower under 20% SWC for the LS and FTS treatments. The freeze–thaw action caused higher sediment loss under low water content (10% and 15%). The runoff-associated total nitrogen (RTN), runoff-associated total phosphorus (RTP), and sediment-associated total phosphorus (STP) loss rate showed a larger fluctuation for FTS than for LS. The freeze–thaw action not only caused the instability of the nitrogen and phosphorus loss behavior but also caused increased diversity among individual samples. The soil erodibility, runoff energy, and runoff power were important dynamic factors associated with erosion, and the freeze–thaw action has a very large impact on these factors. For the LS treatments, the SWC could explain 60% of the variation in RTN loss and 63% of the variation in RTP; the runoff and infiltration both explained 90% of the variation in STN loss and the runoff time explained 97% of the variation in STP. For the FTS treatments, the runoff time explained 63% of the variation in STN and 53% of the variation in STP. The results enable us to understand further the relationship between dynamic factors of rainfall erosion and nitrogen and phosphorus loss under freeze–thaw conditions.

How to cite: cheng, Y., li, P., Xu, G., and zhang, Y.: Effects of dynamic factors of erosion on soil nitrogen and phosphorus loss under freeze-thaw conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1247, https://doi.org/10.5194/egusphere-egu2020-1247, 2020.

D2157 |
Jiangbo Gao and Yuan Jiang

Soil conservation and water retention are important metrics for designating key ecological functional areas. However, research on the quantitative identification of dominant environmental factors in different ecological functional areas remains relatively inadequate, which is unfavorable for zone-based management of key ecological functional areas. This paper presents a case study of Beijing’s key ecological functional areas. In order to objectively reflect the ecological characteristics of key ecological functional areas in Beijing which is mainly dominated by mountainous areas, the application of remote sensing data about high resolution is important for the improvement of model calculation and spatial heterogeneity. Based on multi-source remote sensing data, meteorological and soil observations, soil erosion and water yield were calculated using the Revised Universal Soil Loss Equation (RUSLE) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. Combining the influencing factors, including slope, precipitation, land use type, vegetation coverage, geomorphological type and elevation, a quantitative attribution analysis was performed on soil erosion and water yield in Beijing’s key ecological functional areas using the geographical detector. The power of each influencing factor and their interaction factors in explaining the spatial distribution of soil erosion or water yield varied significantly among different key ecological function areas. Vegetation coverage was the dominant factor affecting soil erosion in Beijing’s key ecological function areas, explaining greater than 30% of its spatial heterogeneity. Land use type can explain the spatial heterogeneity of water yield more than 60%. In addition, the combination of vegetation coverage and slope was found to significantly enhance the spatial distribution of soil erosion (>55% in various key ecological functional areas). The superposition of land use type and slope explained greater than 70% of the spatial distribution for water yield in key ecological functional areas. The geographical detector results indicated that the high soil erosion risk areas and high water yield areas varied significantly among different ecological functional areas. Thus, in efforts to enhance key ecological functional areas protection, focus should be placed on the spatial heterogeneity of soil erosion and water yield in different ecological functional areas.

How to cite: Gao, J. and Jiang, Y.: Identification of Dominant Factors Affecting Soil Erosion and Water Yield within Key Ecological Functional Areas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6839, https://doi.org/10.5194/egusphere-egu2020-6839, 2020.

D2158 |
Zhilin Huang, Liang Ma, Tian Wang, and Lixiong Zeng

As the population has grown and human activities have intensified (predominantly agriculture) in the Three Gorges Reservoir area (TGRA) since the 1980s, the substantial areas of arable land on the steep slopes are the main living and farming space for people. Chinese government implemented the Conversion of Cropland to Forest Program from 2001, because of increasing erosion hazard by excessive cultivation and over-felling. To investigate the efficiency of a range of widely recommended program for soil conservation, long-term monitoring in the Heigou watershed was initiated from 2009. Surface runoff, sediment and nutrient transport were measured at watershed. Monitoring has been done to collect sufficient baseline data about soil erosion rate, runoff rate and quantity of soil nutrients (the sum of nutrients in sediment and runoff) in the watershed. The results showed that the soil erosion modulus varied from 138.26 to 355.28 t·km-2·a-1 among between 2016 and 2019, while average soil erosion modulus was 265.8 t·km-2·a-1, lower than the allowable soil loss in this area. The average runoff coefficient, average loss load of total nitrogen and total phosphorus were 53.9%, 11.24 t·km-2·a-1 and 0.19 t·km-2·a-1. Runoff contributed more than 90% of nitrogen loss, and sediment contributed 82.7% of total phosphorus loss. The soil erosion modulus decreased significantly from 2054.06 t·km-2·a-1 to 265.8 t·km-2·a-1 by returning farmland to forest, which was a severe erosion before. Loss load of soil nutrient diversion was high, and TN was excessive for surface water. The ratio of nitrogen to phosphorus would encourage algae growth and eutrophication in TGRA.

How to cite: Huang, Z., Ma, L., Wang, T., and Zeng, L.: Benefit evaluation and annual change of soil and water conservation after converting farmland to forest in Lanlingxi watershed, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7984, https://doi.org/10.5194/egusphere-egu2020-7984, 2020.

D2159 |
Tian Wang, Zhilin Huang, Liang Ma, and Lixiong Zeng

Rainfall intensity and duration directly affect the process of soil nutrient loss. In this paper, long-term, low-intensity rainfall (LL) (58.4mm rainfall, 605min duration) and short-term, high-intensity rainfall (SH) (59.2mm rainfall, 287min duration) were selected to study the pathway for soil nitrogen and phosphorus loss and load differentiation under different rainfall modes by using a slope experiment plot. The results indicated that: (1) The difference between the runoff duration of LL (3410min) and that of SH (410min) was obvious, and the runoff rate was 14.44% and 28.55%, respectively; (2) There were different nutrient concentration distributions. On one hand, the concentration of TN in the surface flow was lower than that in the interflow. The average TN concentration in the surface flow of LL and SH was 13.7 and 16.94 mg·L-1, respectively. The average TN concentration in the interflow of LL and SH was 59.25 and 50.89 mg·L-1, respectively. On the other hand, the concentration of TP in the surface flow was higher than that in the interflow. The concentration of TP ranged from 0.42 to 1.44 mg·L-1 in the surface flow, and from 0.21 to 0.91 mg·L-1 in the interflow; (3) The interflow is the main pathway of nitrogen loss, while the surface flow is the main pathway of phosphorus loss. The respective TN load of LL and SH runoff was 4.04 and 8.49 kg·hm-2, of which the contribution rate of the interflow was 88.49% and 85.54%, respectively. Additionally, the respective TP load of LL and SH runoff was 0.11 and 0.33 kg·hm-2, of which the contribution rate of the surface flow was 65.79% and 70.67%, respectively; (4) The amount of rainfall was almost the same but its intensity was different. High intensity rainfall would cause greater soil nutrient loss. The amount of total nitrogen and phosphorus loss in a sloppy land due to SH rainfall was 2-3 times higher than that due to LL rainfall.

How to cite: Wang, T., Huang, Z., Ma, L., and Zeng, L.: Characteristics of Soil nutrient loss under different rainfall pattern in slope plots, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12124, https://doi.org/10.5194/egusphere-egu2020-12124, 2020.

D2160 |
Yan Gao

Introducing and establishing sand-binding vegetation, as one of important approaches for combating desertification, has already applied in the ecological restoration and recovery in Mu Us sandy land for more than 60 years. Study on the dynamics of vegetation coverage in Mu Us Sandy Land and its influencing factors is thus a crucial requirement for guiding and establishing sand-binding vegetation. Based on MOD13A2 NDVI time-series data from 2000 to 2015,annual average temperature, annual precipitation, annual growth season precipitation, the land-use/land-cover (LULC) data, and topographic data, explored its dynamics during 2000–2015 and detected their influencing factors by the geo-detector method. The results showed that: (1) the vegetation coverage decrease from east to west in the Mu Us sandy land; (2) from 2000 to 2015,the vegetation coverage in the Mu Us sandy land has been increasing generally, the growth rate was 0.006 /a; (3) the number of pixels with significant increase in vegetation coverage accounted for 33.24% of the study area, meanwhile there was obvious spatial difference, the areas with significant or extremely significant increase of vegetation coverage were mainly distribute in eastern parts; (4) the main influencing factors of vegetation coverage change were annual precipitation, annual growth season precipitation, annual average temperature and LULC. Results indicate that, the influence of climate factors on Mu Us sandy land vegetation coverage was higher than LULC. It is necessary to put forward a suitable vegetation restoration plan under the projected climate change.

How to cite: Gao, Y.: Vegetation Coverage change and its influencing factors in the Mu Us Sandy Land from 2000 to 2015, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8545, https://doi.org/10.5194/egusphere-egu2020-8545, 2020.

D2161 |
Weiqin Dang, Baiqun Wang, and Tianmin Dang

It is well known that soils are vulnerable to water erosion in the hilly and ravine region of the Loess Plateau. The soil and water losses induced by water erosion have both the on-site and off-site impacts in this region, which causes the on-site decline of soil fertility and reductions of crop yields on sloping farmlands, and drains the generated overland runoff and transports the eroded soils/sediments to the off-site valleys or rivers to threaten the safety of the river systems. Constructing the check dam in the valley has the long history and is regarded as one of the powerful measures to control the soil and water losses in a watershed in this region. On the one hand, the check dam plays the vital roles in trapping the large amounts of sediment generated from the sloping lands and buffering the drainage of runoff yielded form the slopes. On the other hand, the silted sediments or eroded soils by the check dam can develop the relatively flat lands in the valleys. The check dam-trapped lands can be utilized to grow the crops and become the farmlands in a watershed. The investigation indicates that the contents of soil organic matter, nutrients and soil moisture of he check dam-trapped farmlands are higher than those of the sloping farmlands or the terraces. According to the analysis on the survey data on the crop yield evolutions in the watershed in this region, the crop yields of check dam-trapped farmlands have been significantly higher than those of the sloping farmlands and terraces in the scenario of the similar fertilizer input and crop cultivars due to the optimum soil moisture condition in the check dam-trapped farmlands. However, the check dam-trapped farmlands face some challenges under the climate change. Some of the check dam-trapped farmlands or the grown crops in these kinds of lands are susceptible to the damage arose from extreme rainstorms because of the outdated measures of soil and water conservation for these kinds of farmlands. In some watersheds, the check dam-trapped farmlands are prone to salinization due to the outdated management. Therefore,the protective measures and techniques of harnessing salinization for the check dam-trapped farmlands should be updated over time in order to keep the check dam-trapped farmlands safe and maintain the higher crop yields in those farmlands in the hilly and ravine region of the Loess Plateau.

How to cite: Dang, W., Wang, B., and Dang, T.: Check Dam-Trapped Farmlands on the Hilly and Ravine Region of the Loess Plateau: Soil Fertility, Crop Yields and Faced Challenges, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21134, https://doi.org/10.5194/egusphere-egu2020-21134, 2020.

D2162 |
Bruno Timóteo Rodrigues, Manuel Esteban Lucas-Borja, Demetrio Antonio Zema, and Yang Yu

Installation of check dams is one of the approaches for erosion mitigation on watersheds all around the world, among others soil and vegetation restoration tools. National, regional and local governments have spent in the past, and still currently spend, important funds for basin scale erosion-control schemes (maintenance and new implementations) using numerous check dams. The functions of these structures are diverse and vary depending on the geomorphic context where the structures are built. However, with the number of check-dams increasing to control floods, regulate sediment transport, reduce upstream reach slopes, and stabilize torrent beds, some projects experience disappointing results and project objectives are not achieved due to many different circumstances. Causes of failure include poor construction quality, inadequate check dam location and lack of adequate design criteria. These failures lead to reduced confidence in using check-dams as restoration tools. Moreover, construction of dense networks of check-dams, or alternatively of a few large open structures, implies major economic investments, but a comprehensive evaluation of their long-term effectiveness is still lacking. This work aims to analyse the effect of check dam over soil and plant interface inmediatelly after wildfires. The proposed work pretends to share scientific  evidence of this effect using a study case located in the Mediterranean basin.

How to cite: Timóteo Rodrigues, B., Esteban Lucas-Borja, M., Antonio Zema, D., and Yu, Y.: Check dams effects on plant and soil interface immediately after wildfire, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9921, https://doi.org/10.5194/egusphere-egu2020-9921, 2020.

D2163 |
Faiza Ahmed

The present study is an attempt to describe the gross anatomy and histology of the alimentary canal of the economically important Nile fish, Hydrocyon lineatus, which is exclusively a carnivorous fish. The genus Hydrocyan is a member of the family Characidae. The family Characidae is a very generalized group confined to the fresh waters of Africa and South America. The species number about 500, of which only one-fifth are African. Of the twenty African genera only eight are represented in the Nile system. Living specimens of Hydrocyon lineatus were used during this work to study some aspects of the anatomy and histology of the alimentary canal. The general organization and structure of the different layers was found to confirm to the case found in general chordate organization. Nonetheless, it was thought pertinent to conclude that similarity in structure of the caeca to that of the intestine would justify replacement of the old nomenclature from pyloric caeca to intestinal caeca. Again, the presence of an intestinal mucosal fold could possibly be a characteristic diagnostic feature of the group in as much as it could be pleisiomorphic characteristic only occurring in lower groups of chordates.

How to cite: Ahmed, F.: Some Aspects on the Anatomy and Histology of the Alimentary Canal of Hydrocyon lineatus, White Nile, Sudan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11053, https://doi.org/10.5194/egusphere-egu2020-11053, 2020.

D2164 |
Manuel Esteban Lucas-Borja, Bruno Gianmarco Carrà, Demetrio Antonio Zema, and Yang Yu

This study presents a comprehensive evaluation of the influence of channel geometry, check dam size, and stream hydrology, as well as site or check dam characteristics including sediment retention capacity and structural conditions of more than 200 check dams recently installed in a large river of Mexico. Analysis was completed using a combination of statistical multivariate techniques (ANOVA and PCA). ANOVA has shown that (i) only check dam material and vegetation cover of the contributing sub-watershed significantly influence check dam conditions and sediment retention capacity, respectively, and (ii) soil type? texture? may play an important role in these check dam characteristics. Conversely, other variables, such as land use and longitudinal slopes of the drained sub-watersheds as well as check dam location have   less influence on check dam sediment storage. PCA has provided two derivative variables related to channel dimensions and vegetation cover , thus demonstrating the influence of these watershed? features on sediment retention behind check dams.

How to cite: Esteban Lucas-Borja, M., Gianmarco Carrà, B., Antonio Zema, D., and Yu, Y.: Are site characteristics and channel hydro-morphology related with check dam functioning? A case study in México, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10009, https://doi.org/10.5194/egusphere-egu2020-10009, 2020.