SSS2.8

Soil erosion and ecological restoration in the Plateau-Mountain areas

The Plateau-Mountain is widely distributed ecologically vulnerable area in the world. Due to the complication of its vertical zonality, the natural environment differentiated obviously, combined with the steep slope cultivations, leading to severe soil erosion and land degradation in these regions. To promote agricultural economic development, how to avoid the high rate of soil loss becomes the key environmental issue in the Plateau-Mountain areas. This session will discuss: 1) soil erosion processes and its environmental effect, 2) measures and techniques of soil conservation and vegetation restoration, 3) the key limiting factors of ecological restoration, and 4) balances between the fragile ecology protection and agricultural development in the Plateau-Mountain region.

Convener: Xingwu Duan | Co-conveners: Yifan Dong, Zhen Han
Presentations
| Mon, 23 May, 08:30–11:02 (CEST)
 
Room G1

Presentations: Mon, 23 May | Room G1

Chairpersons: Xingwu Duan, Zhen Han, Yifan Dong
08:30–08:37
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EGU22-745
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ECS
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Virtual presentation
Shihang Ruan

Abstract: Roots play a major role in reinforcing and stabilizing soil. The pullout mechanical characteristics of soil reinforcement and slope protection of the root systems of dominant shrub species (Pyracantha and Geranium) were estimated by in situ pullout tests in a karst area, in which roots were pulled out from soil to reliably test the pulling force. The F-s curves were multipeak curves with a noticeable main peak and main double peaks. The curves showed a linear increasing trend at the initial stage of drawing and decreased rapidly after reaching the peak. The F-s curves of root systems inserted into rock cracks showed secondary fluctuations in the later stage of drawing, and rock cracks stimulated the tensile efficiency of the root system more effectively. The maximum pulling force had a linear relationship with the increase in soil thickness and a disproportionate increasing trend with the increasing number of broken roots. The displacement of the maximum peak was different between the two tree species and was concentrated at 5-15 cm and 5-25 cm for Pyracantha and Geranium, respectively. The maximum pulling force of Geranium was 1.29 times that of Pyracantha, and the root system of Geranium had strong pullout resistance. These findings can enrich the theoretical knowledge of vegetation slope protection and provide a reference for the selection of soil and water conservation tree species.

How to cite: Ruan, S.: The pullout mechanical properties of shrub root systems in a typical karst area, Southwest China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-745, https://doi.org/10.5194/egusphere-egu22-745, 2022.

08:37–08:44
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EGU22-3475
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Virtual presentation
zhenzhou shen

The soil-covered Pisha stone area is the core source area of coarse sediment in the Yellow River and has become the focal point of ecological control of the Yellow River Basin. It is thus vital to study the spatial distribution of erosion coupling between geomorphology, vegetation, and water in the soil-covered Pisha stone area. Some valuable research results have been obtained already by using high-definition remote sensing aerial photographs and-high precision data from unmanned aerial vehicles. In particular, the image resolution obtained by unmanned remote sensing reveals small watershed topographic features and the characteristics of vegetation structure. Thus, the use of remote sensing is vital for research involving the spatial distribution of soil erosion in the slopes of the Pisha stone area and the dynamics of the geomorphic spatial structure of the slopes. In addition, the negative correlation between the spatial structure of the vegetation community and the energy dissipation impedance of erosion requires further study. Research into soil erosion in the Pisha stone area thus represents an urgent scientific need whose outcome will directly affect the theoretical foundation of a comprehensive model for treating soil erosion in this area.

How to cite: shen, Z.: Research progress of soil erosion in Pisha stone area of Yellow River, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3475, https://doi.org/10.5194/egusphere-egu22-3475, 2022.

08:44–08:51
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EGU22-1248
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ECS
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Highlight
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Presentation form not yet defined
Endan Li, Qinke Yang, Guowei Pang, Chunmei Wang, Lijuan Yang, and Bingjie Qiao

Topography is the result of geological tectonic movement and land erosion development, which is min factor for slope processes such as surface runoff and soil erosion. At present, there is insufficient research on the spatial pattern and influencing factors of Slope Length and Steepness (LS) factors in the Qinghai-Tibet Plateau (QTP). Based on the 30m resolution SRTM (Shuttle Radar Topography Mission) digital elevation data, we calculates the Hack profile and area-elevation integral parameters, extracts the slope, slope length and LS factor, and analyze their relationship with the elevation. The results show that: 1) the slope and LS factor are small in the centre area of the plateau, and LS decreases from southeastern to the northwestern. The terrain inside the plateau is flat, surrounded by high mountains, and the slope, slope length and LS value are large in areas with large topographic relief; 2) The Hack profiles of the six main rivers including , etc, in the QTP are convex, and the hypsometric curve  of the rivers is close to convex. The geomorphic evolution of the region is in its youth stage as a whole, indicating that the neotectonics of the Qinghai-Tibet Plateau is active. This geomorphic feature makes the LS value distributed in Hengduan Mountains, Western Sichuan Plateau, Yarlung Zangbo River Grand Canyon, etc; 3) The overall dominent of LS in the QTP is slope steepness, while in the steep areas on the edge of the plateau is slope length, and the gentle areas centre QTP is slope; 4) The distribution characteristics of LS are consistent with soil erosion types. The extremely steep slope areas are mainly affected by glacier erosion, while the steep slope areas such as Southeast Tibet are greatly affected by water erosion, The transition zone between the plateau surface and marginal mountains is mainly water erosion and freeze-thaw erosion, and in the dry Qiangtang plareau has strong wind erosion The geomorphic and erosive topographic characteristics of the QTP discussed in the paper, will be a theorical base for the extraction of topographic factors in soil erosion and hydrology, and also has implications for research of multispherical interactions in Tibetan Plateau's earth system.

How to cite: Li, E., Yang, Q., Pang, G., Wang, C., Yang, L., and Qiao, B.: Spatial pattern and influencing factors of Slope Length and Steepness Factors (LS) in Qinghai Xizang Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1248, https://doi.org/10.5194/egusphere-egu22-1248, 2022.

08:51–08:58
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EGU22-4391
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ECS
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Presentation form not yet defined
Yanbo Li, Ming Wang, Yuanmei Jiao, Li Rong, and Jiangcheng Huang

Terraces are important practice to conserve soil and water in farming systems in mountain areas. Since the mid- 20th century, marginalization of farmland occurred worldwide in mountainous areas. Farmers reduced investment in terraced fields or even abandoned the fields, and induced negative ecological consequences that are widely concerned. Current studies about marginalization of terraces mainly focus on upland terraces. The understandings of the process of marginalization of paddy terraces and their impacts are limited. Hani Paddy Terraces are one of the Globally Important Agriculture Heritage Systems. However, many of the paddy terraces have changed into upland terraces due to lack of water, labor out-migration ect, which hindered the conservation of the heritage. Taking Amengkong River Basin in Yuanyang County in Southwestern China as the case study area, we explored the changes in terrace structure, productivity of top soil (0~20 cm ) and the water holding capacity soil in 0~70 cm depth in Hani Paddy Terraces since conversion to upland terraces fields by 2~14 years. We found that (1) most ridges disappeared after conversion, the surface of fields were generally maintained in flat conditions, risers of terraces collapsed in varying degrees in more than 70% filed parcels. The degree of damages in terraces structures showed a U-shape curve along with time, as the pattern of drained by 2 years> drained by 3~4 years> drained by 10~14 years > drained by 5~9 years;(2)the soil productivity index increased after converted to upland terraces, and showed a trend of decreasing first and then increasing along with increasing years of conversion. (3) The water holding capacity of 0~70 cm soil dramatically decreased after conversion, and increasingly decreased along with increasing years of conversion. The maximum water holding capacity decreased by 9.16%~21.70% and the capillary volume decreased by 12.09%~24.20%,the decreasing of maximum water holding capacity and capillary volume were most serious in soils of 0~30 cm depth. Our study revealed the impacts of draining on structure of terraces and soil property in Hani Paddy terraces. The findings could enhance the understanding of the biophysical changes in soil during the marginalization in paddy terraces, which would benefit to the conservation and restoration of paddy terraces. 

How to cite: Li, Y., Wang, M., Jiao, Y., Rong, L., and Huang, J.: Changes in Terrace Structures and Soil Properties in Hani Paddy Terraces after Conversion to Upland Terraces, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4391, https://doi.org/10.5194/egusphere-egu22-4391, 2022.

08:58–09:05
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EGU22-6779
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Highlight
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Virtual presentation
Tingting Tao, Shiqi Chen, and Xiaoyan Chen

    Subsurface water flow above the weakly permeable soil layer commonly occurs on purple soil slopes. However, it remains difficult to quantify the effect of subsurface water flow on the surface flow velocity. Laboratory experiments were performed to measure the rill flow velocity on purple soil slopes containing a subsurface water flow layer with the electrolyte tracer method considering 3 subsurface water flow depths (SWFDs: 5, 10, and 15 cm), 3 flow rates (FRs: 2, 4, and 8 L min-1), and 4 slope gradients (SGs: 5°, 10°, 15°, and 20°). As a result, the pulse boundary model fit the electrolyte transport processes very well under the different SWFDs. The measured rill flow velocities were 0.202 to 0.610 m s-1 under the various SWFDs. Stepwise regression results presented the positive dependence of the flow velocity on FR and SG but a negative dependence on SWFD. SWFD had notable effects on the rill flow velocity. Decreasing the SWFD from 15 to 5 cm increased the flow velocity. Moreover, the flow velocities under the 10- and 15-cm SWFDs were 89% and 86%, respectively, of that under the 5-cm SWFD. The flow velocity under the 5-, 10- and 15-cm SWFDs was decreased to 89%, 80%, and 77%, respectively, of that on saturated soil slopes. The results will enhance the understanding of rill flow hydrological processes under SWFD impact.

How to cite: Tao, T., Chen, S., and Chen, X.: Rill flow velocity affected by the subsurface water flow depth of purple soil in Southwest China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6779, https://doi.org/10.5194/egusphere-egu22-6779, 2022.

09:05–09:12
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EGU22-4998
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ECS
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Presentation form not yet defined
Li Rong, Xingwu Duan, Taicong Liu, and Yuhong Qin

Despite soil erosion has a strong impact on crop yield, whether soil erosion depth leads to abrupt or gradual crop yield changes is not well understood. To investigate how crop yields respond to soil erosion depth, we conducted a simulated erosion experiment by adopting the cut-and-fill method from 2012 to 2018 in a typical mountain area in the southeastern China. A completely randomized design with five soil erosion depth (5, 10, 20, 30 and 40 cm soil cut) and a control (0 cm soil cut) were used. Each treatment had three replicates. Maize was planted in these simulated erosion plots and maize yields were monitored from 2012 to 2018. Our results showed that the maize yield decreased with erosion depth and with decreasing remaining Ap horizon depth. Inconsistent with earlier studies, maize yield exhibited a quadratic function rather than linear response to increase in soil erosion depth and decrease in remaining Ap horizon depth. Soil erosion depth led to abrupt changes in maize yield. Compared with control, maize yield did not decrease significantly at 5 cm erosion depth or >25 cm remaining A horizon depth, but its reduction rate per 1cm of soil loss (3.36%) increased sharply at 10 cm erosion depth or 20 cm remaining Ap horizon. When remaining Ap horizon left 10 cm, maize yield demonstrated the lowest, which may be irreversible via application of chemical fertilization. Considering high heterogeneity of Ap horizon in the mountain area, soil erosion-crop yield relationship could be expressed well by remaining Ap horizon. We also found remaining Ap depth had a significant direct and indirect (via reduced SOM, soil available water, AP and AK contents) negative effect on maize yield. These results could be useful in identifying allowable soil-loss thickness and highlight the importance of soil nutrient monitoring in different soil erosion levels in designing a fertilization scheme aimed at ensuring food security.

How to cite: Rong, L., Duan, X., Liu, T., and Qin, Y.: The effect of soil erosion depth on maize yields, evidence based on a long-term field simulation experiment , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4998, https://doi.org/10.5194/egusphere-egu22-4998, 2022.

09:12–09:19
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EGU22-4557
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ECS
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Highlight
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Virtual presentation
Longpei Cen, Xudong Peng, and Quanhou Dai

Rocky desertification has become one of the global ecological environmental problems. Karst rocky desertification area of southwest China is suffering from ecosystem degradation, and the combination of water and soil resources determines the stability of their ecosystems. In recent years, soil leakage has attracted attention because it was that under the development of carbonate shallow fissures, the water and soil along the such pipes as shallow fissures leaks underground, resulting in the allocation of soil and water underground, affecting the integrity of the overlying ecosystem. This study aimed to reveal the leakage loss process, characteristic and mechanism of soil in fissures on sloping lands in the karst area, taking fissures on sloping lands in karst plateau of Guizhou province as the research object, combined with the methods of paint marking and soil particle analysis was conducted to study the leakage loss process of soils in fissures. The result showed that rainstorm or downpour is the key factor of soil fissure leakage loss, and its leakage form is mainly soil creep. Soil creep displacements of different fissure at 104.5 mm rainfall event between 1.0 cm and 2.5 cm, accounting for more than 62.5% of the displacement at 332.7 mm rainfall event, while the soil creep displacement of fissures just range from 0.2 cm to 0.3 cm at the larger rainfall of 181.5; the particle content with different particle sizes in rock-soil interfaces and soils of six fissures selected under 3 precipitation events (104.5, 151.2 and 332.7 mm) showed that the fissure soil does not leak down uniformly, but some particles at the soil layers or rock-soil interfaces leak to the lower layer at random in the process of creep leakage loss. In other words, the occurrence of soil layers and particles are accidental, and the soil particles in the rock-soil interfaces and the soil layers of fissures have the possibility to leak down. Facts proved that the soil creep leakage loss in fissures is a complex process which is determined by the internal factors such as fissure structure, fillings characteristics and bottom connectivity, and such external factors as rainfall etc.
Key words: underground leakage loss; soil; karst fissure; sloping land; karst plateau

How to cite: Cen, L., Peng, X., and Dai, Q.: Soil creep and leakage process in shallow fissures on a karst slope based on particle composition analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4557, https://doi.org/10.5194/egusphere-egu22-4557, 2022.

09:19–09:26
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EGU22-1947
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Virtual presentation
Yifan Dong

Gully erosion was one of the key processes of soil erosion in Hengduan mountain region, which belonged to the eastern part of Qinghai-Tibet Plateau. This dramatic changes in both horizontal and vertical direction has led to a diversity soil groups within the region. The aims of this study were to investigate the gully distribution and density in different soil zones, and find out the key factors that influenced the susceptibility and intensity of gully erosion of Hengduan mountain area. Totally 2300 investigation quadrats were randomly set with the size of 1 km × 1 km to check whether the occurrence and the density by Google Earth images. The ratio of gully occurrence (GR) was 25.5%, and the average gully density (GD) and gully number (GN) was 2.22 km km-2 and 20.4 of Hengduan mountain area. The annual temperature, vegetation and slope were the key factors that influences the occurrences of gullies in the alpine (>3700 m a.s.l), middle mountain (2000-3700 m a.s.l) and low mountain (<2000 m a.s.l) soil zones, respectively. The intensity of gully erosion showed exponential decreasing relationships with soil property including soil organic matters and silt content, and the average GD in different soil zones showed the same relationships with the R2 higher than 0.7. These results indicating that the distribution of gully erosion were more related to the external environmental factors, and the intensity of gully erosion were determined by soil properties at the regional scales.

How to cite: Dong, Y.: The distribution and intensity of gully erosion in different soil zones of the Hengduan Mountain area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1947, https://doi.org/10.5194/egusphere-egu22-1947, 2022.

09:26–09:33
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EGU22-6708
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ECS
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Presentation form not yet defined
Qiankun Guo, Zhijie Shan, Ronghua Zhong, and Xingwu Duan

The vegetation cover in China has changed significantly in the past 30 years, however evidence for vegetation cover dynamics in the dry valley region (DVR) is still lacking. This study aimed to detect fractional vegetation cover dynamics in DVR from 2000 to 2020 with MODIS products, and evaluate the effects of precipitation and hydropower construction projects on vegetation cover dynamics. The results showed that: (a) the long-term average annual fractional vegetation cover for the dry valley region, including the dry-hot valleys, dry-warm valleys and dry-temperature valleys were 0.452, 0.426, 0.504 and 0.446, respectively. Significant decreasing trend of annual FVC from 2000 to 2020 was reported for overall dry valley region. Specifically, significant reducing trends were mainly observed in the dry-hot valleys and dry-warm valleys that located in the west-south part of DVR, while significant growing trends in the dry-temperature valleys of the Min and Baishui Rivers; (b) Annual Precipitation and hydropower projects construction are two key factors that contributing to changes in annual FVC for valleys. The present study is probably the first report on vegetation cover dynamics and the effects of influencing factors in DVR of Southwest China, and helpfully for further scientific studies and restoration management practices in DVR, although more detailed studies for the changes of vegetation cover and its mechanism need to be done.

How to cite: Guo, Q., Shan, Z., Zhong, R., and Duan, X.: Fractional Vegetation Cover Dynamics of the dry valleys in Southwest China from 2000 to 2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6708, https://doi.org/10.5194/egusphere-egu22-6708, 2022.

09:33–09:40
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EGU22-6640
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ECS
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Highlight
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Presentation form not yet defined
Honghong Lin, Xingwu Duan, Yawen Li, Lanlan Zhang, Li Rong, and Ruimin Li

Soil erosion in croplands has a strong impact on global carbon (C) cycle. Assessment of erosional effects on soil organic carbon (SOC) dynamics in agricultural soils suffers from the difficulty of distinguishing the erosional effects and complex interaction processes between erosion and C cycling. To simulate the effects of soil erosion, a plots experiment including six erosion levels (0, 5, 10, 20, 30, and 40 cm eroded) was conducted for seven years (2012-2018). The erosion levels were simulated using artificial soil profiles created by mixing soils from different layers in the original soil profile (never eroded) in a certain proportion. Subsequently, based on the field observations during 2012-2018, the SOC dynamics of each experimental plot were simulated by using a process-oriented C cycle model (denitrification-decomposition (DNDC)) to quantify the effects of erosion on SOC dynamics. The measurements at the beginning of the plots experiment showed that simulated erosion resulted in the depletion of SOC with an average reduction rate of 9.7% per 10 cm of soil loss; SOC in eroded soils recovered after seven years of cropping, the declining slope of the SOC measured in 2018 was 3.0% per 10 cm of soil loss, suggesting that dynamic replacement had occurred. Model simulation results indicated that soil erosion could reduce the C inputs from crop residue by lowering soil productivity; soil heterotrophic respiration in eroded soils was restricted due to the lower initial SOC content. As a result, the simulated overall SOC stock in eroded soils was restored after erosion stopped because of the lower C output. These results indicated that SOC loss at eroding sites was caused mainly by lateral transport rather than enhanced decomposition. The fate of the displaced SOC within catchments is key to assess the net impacts of soil erosion on SOC dynamics at a large scale.

How to cite: Lin, H., Duan, X., Li, Y., Zhang, L., Rong, L., and Li, R.: Simulating the effects of erosion on organic carbon dynamics in agricultural soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6640, https://doi.org/10.5194/egusphere-egu22-6640, 2022.

09:40–09:47
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EGU22-4227
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ECS
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Virtual presentation
Huan Guo

Abstract: To explore the adaptable plants soil reinforcement effects in the karst region of southwest China. A horizontal pull friction test was performed on the roots and soil by using a three-year-old shrub Pyracantha, and the friction characteristics of root-soil interface were analyzed by scanning electron microscopy and interference method. The results indicated that :(1) the root system of pyracantha showed two failure modes in the pull-out test: the pull-out friction of root-soil interface increases with the increase of root diameter and vertical load. (2) When gravel content is set at 0, 10%, 30% and 50%, the frictional force between root and soil tends to decrease. (3) There was a positive correlation between root surface roughness and root diameter in diameter range of 1-6mm, with correlation coefficient R =0.995. (4) There is an obvious correlation between root-soil friction and roughness. These results are significant to further explore the mechanical mechanism of plant root-soil interaction, and to strengthen the shallow soil and repair the fragile ecological environment.

Key words: Karst; Pyracantha; Root-soil friction; Roughness

How to cite: Guo, H.: Research on the interaction between roots and soil of adaptable plants pyracantha in the karst region , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4227, https://doi.org/10.5194/egusphere-egu22-4227, 2022.

09:47–09:54
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EGU22-4625
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Virtual presentation
Jiaxin Liu

Plant litter incorporation into soil is a widespread phenomenon in the natural environment. Accurate estimation of the soil detachment capacity ( Dc ) driven by overland flow under litter incorporation effects is crucial for improving soil erosion prediction. However, the effects of litter incorporation on soil detachment processes are often ignored, and the temporal variation of Dc under litter incorporation effects remains unclear for the Loess Plateau of China. In this study, we conducted flume tests to determine the temporal variation of Dc for soils incorporating two typical plant litters ( Bothriochloa ischaemum (L.) Keng. litter, and Artemisia sacrorum Ledeb. litter) between May 2017 and October 2018 (a 524-day period). Furthermore, the key factors
affecting Dc were identified. Our results showed that the temporal variation in Dc was consistent across the different soil treatments (two litter incorporation treatments and one bare soil control), showing a rapid decline and then fluctuating at a low level, with Dc ranging from 0.115 to 6.876 kg m−2 s−1 . Incorporation of litter effectively reduced Dc , with the Dc of soil treatments incorporating litter being 15% to 29% lower than that of bare soil (2.110 kg m−2 s−1 ). Further analysis showed that the temporal variation in Dc was mainly affected by the development of a physical soil crust. Dc can be successfully estimated using a nonlinear equation incorporating flow shear stress and soil cohesion (R2 = 0.77, NSE = 0.65), which represent the erosive force and soil erosion resistance, respectively. Our study reveals the important role of plant litter in the soil detachment process and aids the understanding of soil erosion pathways. Further studies are needed to investigate the effects of a physical soil crust on the soil detachment process driven by overland flow.

How to cite: Liu, J.: Effects of Litter Incorporation on Soil Detachment Processes on the Loess Plateau of China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4625, https://doi.org/10.5194/egusphere-egu22-4625, 2022.

Coffee break
Chairpersons: Zhen Han, Yifan Dong
10:20–10:27
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EGU22-6676
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Presentation form not yet defined
Yawen Li, Xingwu Duan, Ya Li, Yuxiang Li, and Lanlan Zhang
Changes in land use can result in soil erosion and the loss of soil organic carbon (SOC). However, the individual contribution of different land use types on SOC variability as well as the combined impacts of land use and soil erosion are still unclear. The aims of the present study were to: (1) evaluate soil erosion and SOC contents under different land use types, (2) identify the influences of soil depth and land use on SOC content, and (3) determine the contribution of land use and soil erosion on SOC variability. We assessed the SOC and total soil nitrogen (TSN) contents under three types of land use in the dry-hot valley in southern China. Caesium-137 ( 137Cs) and excess lead-210 ( 210Pbex) contents were also measured to determine soil-erosion rates. Land use was found to significantly affect soil erosion, and erosion rates were higher in orchard land (OL) relative to farmland (FL), which is in contrast with previous study results. SOC and TSN contents varied significantly between the three land use types, with highest values in forest land (FRL) and lowest values in OL. SOC was found to decrease with decreasing soil depth; the highest rate of reduction occurred in the reference site (RS), followed by FRL and FL. The interaction between soil erosion and land use significantly impacted SOC in the soil surface layer (0–12 cm); the direct impact of soil erosion accounted for 1.5% of the SOC variability, and the direct or indirect effects of land use accounted for the remainder of the variability. SOC content in deep soil was mainly affected by factors related to land uses (89.0%). This quantitative study furthers our understanding on the interactive mechanisms of land use and soil erosion on changes in soil organic carbon.

How to cite: Li, Y., Duan, X., Li, Y., Li, Y., and Zhang, L.: Interactive effects of land use and soil erosion on soil organic carbon in the dry-hot valley region of southern China , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6676, https://doi.org/10.5194/egusphere-egu22-6676, 2022.

10:27–10:34
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EGU22-1257
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ECS
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Virtual presentation
Yusen Zhang and Lunjiang Wang

Stemflow, as one of the most important elements of forest precipitation redistribution, affects the delivery and spatial distribution of water and nutrient. Although approximately 4% of forests are affected by wildfire worldwide, no study has measured stemflow velocity after forests are affected by wildfire. The aim of this study is to determine (1) whether stemflow velocity changes after wildfire, (2) whether stemflow velocity changes with stem flow rate and height, (3) whether stem surface roughness affects stemflow velocity. In this study, we designed a device to quantify stemflow velocity. Our study revealed that the destructions of bark morphology and biological crust on the stem surface were the main factors affecting the change of stemflow velocity. The wildfire caused an enhanced stemflow velocity by roughly 30% for the burned pine compared to pine that did not affect by the wildfire. The stemflow velocity increased with stemflow rate following a power function. The width of pine bark had a negative linear relationship with stemflow velocity. With the increase in stemflow rate, the difference in stemflow velocity between burnt pine and unburnt pine was not significant. Stemflow velocity did not increase with the height of stemflow starting point increased, probably because increased stemflow energy caused the stemflow to detach from the stem. This study implies stemflow velocity affected the migration rate and spatial distribution of water and nutrient on stems and land surface around the base of tree. The increased stemflow energy is also likely to exacerbate soil erosion. All these can affect the restoration process of forest ecosystems from wildfire.

How to cite: Zhang, Y. and Wang, L.: Effect of wildfire on stemflow velocity of pine, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1257, https://doi.org/10.5194/egusphere-egu22-1257, 2022.

10:34–10:41
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EGU22-2620
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ECS
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Virtual presentation
Yuhong Qin, Li Rong, Xingwu Duan, and Zhijia Gu

The plateau-mountain areas around the globe are at risk of food insecurity because of its high intensity of soil erosion, limitied suitability of land for agriculture and increasing population pressure. Although plant breeding, improved plant-protection techniques, new variety, application of fertilizer promote increases of crop yields, more frequent extremes of climatic events, topography related to soil erosion can lead to progressive instability in crop production. However little consideration is given in relationships between climatic, topographical factors and grain yields in the Plateau-mountain region. In this study, we collected county-level data on the actual grain yield and environmental factors of the 119 counties in Yunnan province over the past 28 years (1985–2012) to explore the controls on grain yield and how they affect grain yields. Our findings showed that actual grain yeild(AGY) increased over time with an inter-annual fluctuation. Spatially, our findings revealed AGY were strongly influenced by slope. Regression analysis also showed that slope gradient could explain 26.29% of the spatial distribution variability of AGY. Redundancy analysis revealed that AGY positively correlated with evaporation, TN90p, TK, and pH whereas negative correlations with Apre, RH, R50, C/N, slope, and aspect. However climatic and topographic factors and soil properties exhibited greater impacts on AGY, compared to extreme climate indices. We also found that TK showed a significantly positive effect on AGY, indicating that counties with higher TK content in soils could produce higher actual grain yield. And R50 and aspect also had an indirect effect on AGY through influencing TK. Thus, the application of K fertilizer in northwestern, northeastern, and southeastern Yunnan province where soil TK was relatively low may be the key to improve grain yield.

How to cite: Qin, Y., Rong, L., Duan, X., and Gu, Z.: Slope drivers grain yield in the Yunnan Plateau-Mountain areas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2620, https://doi.org/10.5194/egusphere-egu22-2620, 2022.

10:41–10:48
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EGU22-3290
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Virtual presentation
Dandan Li, Xiaoyan Chen, Zhen Han, Xiaojie Gu, and Yanhai Li

The hydrological conditions near the soil surface influence the soil erosion process, as determined by the soil erodibility and critical shear stress. The soil erodibility and critical shear stress of saturated purple soil slopes were computed and compared with those of unsaturated purple soil slopes. The detachment capacities computed through the numerical method (NM), modified numerical method (MNM) and analytical method (AM), from rill erosion experiments on saturated purple soil slopes at different flow rates (2, 4, and 8 L min−1) and slope gradients (5, 10, 15, and 20°), were used to comparatively compute the soil erodibility and critical shear stress. The computed soil erodibilities and critical shear stresses were also compared with those of unsaturated purple soil slopes. At the different slope gradients ranging from 5° to 20°, there were no significant differences in the soil erodibilities of the saturated purple soil and also in those of the unsaturated purple soil. The critical shear stresses slightly varied with the slope gradients. The saturated purple soil was relatively significantly more susceptible to erosion. The NM overestimated the soil erodibility of both saturated and unsaturated soils by 31% and underestimated the critical shear stress. The MNM yielded the same soil erodibility and critical shear stress values as the AM. The results of this study supply parameters for modeling rill erosion of saturated purple soil slope.

How to cite: Li, D., Chen, X., Han, Z., Gu, X., and Li, Y.: Determination of Rill Erodibility and Critical Shear Stress of Saturated Purple Soil Slopes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3290, https://doi.org/10.5194/egusphere-egu22-3290, 2022.

10:48–10:55
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EGU22-828
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ECS
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Virtual presentation
Ji Yang, Yifan Dong, and Jiangcheng Huang

How to use a suitable method to accurately measure gully morphology is very important in the study of gully erosion monitoring and development, and the development of Unmanned Aerial Vehicle (UAV) has made it easy to apply UAV photogrammetry techniques to gully erosion studies. The aim of this study is to evaluate the accuracy of data and the efficiency of data processing by analyzing the errors of different schemes, and to provide suitable plan design ideas for the study of gully by UAV. Gully is the object of study and different flight schemes and Ground Control Point (GCP) placement schemes are used to acquire and process the data, and finally the errors are analyzed by Digital Surface Model (DSM) and orthophoto. Among all the schemes, the one with a flight altitude of 30m, 80%/70% photo overlap and 11 GCPs had the highest accuracy (Mean absolute error of 0.0353m and root mean square error of 0.0525m), but this scheme took more data collection and processing time and was less efficient. The number of GCPs and the placement location also have a significant impact on the accuracy,the position closer to the GCPs has a smaller error,and this study proves that the number of GCPs should not be more than 9 and should be evenly distributed in different parts of the gully.. When the flight altitude is 70m, the overlap is not less than 50%/40%, and the number of control points is 6, both accuracy and measurement efficiency can be taken into account at the same time. In addition, the sources of errors and the distribution locations of checkpoints with high errors were analyzed in four aspects: shadow, slope gradient, slope direction and vegetation. The use of UAVs in gully erosion studies is very convenient to get the later products with centimeter-level accuracy, and based on the results of the study we suggest that the flight altitude and photo overlap can be appropriately reduced when designing the scheme, and the number of GCP can be increased in the areas that need to be focused on and the areas with large elevation changes. At the same time, flight safety, UAV battery power, data collection efficiency and processing efficiency should be considered comprehensively.

How to cite: Yang, J., Dong, Y., and Huang, J.: Assessment of the gully morphology measurement method based on UAV photogrammetry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-828, https://doi.org/10.5194/egusphere-egu22-828, 2022.

10:55–11:02
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EGU22-4927
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ECS
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Virtual presentation
Kemin Liu and Lunjiang Wang

Soil moisture is a key factor limiting vegetation succession in karst ecosystem. Wildfire changes soil physical and chemical properties, which likely affect evapotranspiration of post-wildfire plant recovery. However, merely studies have been performed to elucidate the evapotranspiration processes and the controlling factors. In this experiment, two typical herbaceous plants (Compositae Artemisia and Gramineae Saccharum) in karst areas were selected for pot experiment. The treatment without plant was used as the control. Combustions were laboratorially carried out with different severity (light, moderate, and high) to simulate different intensities of wildfire disturbance. During the experiments, the mass change in each pot was measured to obtain evapotranspiration under different weather conditions. We also collected meteorological data (total radiation, water vapor pressure, air temperature, relative humidity, atmospheric pressure, soil heat flux, soil temperature, etc.), biomass, and soil properties. Our study showed the impact of wildfire on evapotranspiration. We also compared the differences in evapotranspiration of different herb covers. We detected that weather conditions (e.g., duration of continual drought) also had important influences on the evapotranspiration during post-wildfire restoration. The study provides more insight into characteristics of soil water movement after wildfire in karst areas and evaluating the availability of soil moisture after wildfires. 

How to cite: Liu, K. and Wang, L.: Evapotranspiration process under typical herb cover after wildfire, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4927, https://doi.org/10.5194/egusphere-egu22-4927, 2022.