Assessing ecological restoration effects on hydrological regimes is important for watershed management, especially under semi-arid conditions.  The long-term trends of streamflow components were analyzed for three less forested watersheds (LFWs), and for two largely forested watersheds (FWs) within the Beiluo River Basin on the Chinese Loess Plateau.  Three LFWs were undergoing major vegetation restoration, in which the vegetation coverage changed from 16–23% in 1970 to 57–80% coverage in 2019. While as contrast, the two FWs has vegetation coverage from 65–68% in 1970 to 88–92% in 2019. Daily flow data for each watershed and year were normalized by rainfall to eliminate effects of non-stationary rainfall.  Mean annual streamflow totals for the ~60-year study period were 25.1–34.1 and 21.6–48.1 mm y_1 for the LFWs and FWs, respectively.  Average contributions of baseflow to total streamflow were 32–44% for the LFWs and 58–61% for the FWs. Mann-Kendall tests showed significant decreasing trends for annual streamflow and stormflow (0.23–0.54% y_1) from the LFWs throughout.  Mean streamflow from the LFWs between 2000 and 2019 decreased by 58% compared to the pre-2000 period, while the average contribution of stormflow decreased from 66% to 35% (2010s). However, winter baseflow increased with time since start of restoration.  Conversely, streamflow (components) for the FWs showed only slight fluctuations in decadal, annual and seasonal trends.  Both total streamflow and stormflow exhibited strong power relationships with vegetation coverage, illustrating a tendency towards stable flow regimes for vegetation coverage >60–70%.  Large-scale vegetation restoration has fundamentally changed amounts and temporal distribution of streamflow (components) on the Loess Plateau mainly by regulating stormflow. After 20 years of restoration, the trend and proportion of streamflow components from the LFWs approximated those of the FWs.  Since soil erosion is driven by a certain of amount and intensity of runoff, the above results imply that soil erosion and sediment transportation would reach a stability with vegetation restoration to a certain coverage in watersheds. But it is necessary to investigate the difference among regions.  These results underpin the planning of sustainable management of natural resources and socio-economic development during long term ecological restoration on the Loess Plateau.

Keywords: Trends of long-term hydrological elements; Surface flow and baseflow; Vegetation restoration; Loess Plateau

How to cite: Zhang, X., Yi, H., Xue, F., Bruijnzeel, L. A., Cheng, Z., Liu, B., and Li, Y.: Understanding the variability and stability of hydrological components under vegetation restoration in watersheds on the Chinese Loess Plateau in past 50 years, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1151, https://doi.org/10.5194/egusphere-egu23-1151, 2023.

Abstract: Vegetation restoration significantly affect soil infiltration capacity, surface runoff and soil erosion by substantially improving vegetation structure and soil properties. However, changes in soil properties and infiltration capacity at different stages of secondary succession in forestland on the Loess Plateau need to be further understood. The aim of this study was to quantify the effects of stand types at different succession stages on soil properties and infiltration capacity, and to identify key factors influencing soil infiltration characteristics on the Loess Plateau, so as to serve for soil erosion control, land use optimization and watershed management. Here, we selected four tree successional stages, consisting of Betula platyphylla Suk.(Bp), Pinus tabulaeformis Carr.(Pt), Quercus wutaishanica Suk- Pine tabulaeformis Carr mixed forests (Qw-Ptmf), and Quercus wutaishanica Mary(Qw), and sloping farmland as controls, to analyse changes in litter and plant roots characteristics, corresponding soil properties and infiltration characteristics. Soil hydraulic conductivity was measured using the single-ring-knife constant water head infiltration method. Soil properties were determined and the effect of soil properties on soil infiltration capacity was analyzed using path analysis. The results showed that litter thickness and biomass generally tended to increase with vegetation succession. Among them Qw-Ptmf had the greatest litter biomass and fine root biomass. Root biomass was greater in all stand types in the 0-5 cm and 5-20 cm soil layers than in the 20-40 cm, with the most rapid decline from the 0-5 cm to the 5-20 cm soil layer. The continuous vegetation restoration significantly improved soil properties and infiltration capacity compared to the control farmland. Qw-Ptmf showed the best soil properties and infiltration capacity, followed by Qw, Pt and Bp. Soil properties of the same tree species at different ages were different, and generally tend to get better as succession progresses. Path analysis showed that litter and plant roots together improved soil properties in the 0-5 cm soil layer, while below 0-5 cm plant roots dominated. Soil porosity and soil bulk density were the most critical factors influencing soil infiltration capacity. It is helpful to understand that vegetation succession fundamentally reduces surface runoff and soil erosion by improving soil properties (especially from 0-20 cm) and increasing soil infiltration capacity in the area. Underground plant roots and ground litter coverage play an important role in improving positively soil properties and thus soil infiltration capacity with vegetation succession. Results of this study can be useful for regional ecological restoration planning, stand management and soil erosion prediction on the Loess Plateau.

Keywords: Forestland  litter and plant roots  soil properties  infiltration capacity  vegetation succession  Loess Plateau

How to cite: Xu, X., Zhang, X., Wang, H., He, J., and Xue, F.: Effects of litter and plant roots on soil properties and infiltration capacity with vegetation succession on the Loess Plateau, China, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4595, https://doi.org/10.5194/egusphere-egu23-4595, 2023.

The impact of land use change on soil organic carbon storages at the regional scale is crucial to the ecological effects of the local environment. According to soil samples and land use data, the effect of land use change on soil organic carbon density and reserves in the surface layer (0~20 cm) of the Loess Plateau, Shaanxi, from 1985 to 2015, was studied. The results show: ⑴The policy of returning farmland to forest has a great impact on the transformation of land use type in the tableland of Shaanxi Loess Plateau. The change of land type mainly focused on the area reduction of cultivated land and grassland, respectively reduced by 6.02% and 15.14%.And the areas of forest land and residential land increased, with an increase of 281.07% and 24.09% respectively. ⑵ In the past three decades, the spatial variation trends of soil organic carbon density in surface soils of the study area were quite different. The increase was 11.43% in 2006 compared with 1985, and 89.74% in 2015 compared with 2006. ⑶ From 1985 to 2006, the area of maintaining land use type was 111997.18 km², and the surface soil carbon storage increased by 1404.31×10⁶kg. The area of changing land use type was 776.15 km², and the carbon storage increased by 14.49×10⁶kg. From 2006 to 2015, the area of maintaining land use type was 9359.68 km², and the surface soil carbon storage increased by 3829.98×10⁶kg. The area of changing land use type was 776.15 km², and the carbon storage increased by 1318.13×10⁶kg. ⑷ In the past 30 years, the area of maintaining land use type decreased, and the area of changing land use type increased. The conversion of land use type to forest land and grassland was conducive to the formation of surface soil carbon sink, and the conversion to cultivated land and residential land resulted in the release of surface organic carbon. The comparative analysis between the two periods showed that the conversion of land use type was more intense and the soil carbon storage increased significantly after the policy of returning farmland to forests was implemented. Therefore, the policy of returning farmland to forests in the tableland of Shaanxi Loess Plateau can increase the carbon fixation of ecosystem.

How to cite: Liu, M., Zhang, M., and Chang, Q.: Impact of Land Use Change on Soil Carbon Storage in topsoil of the tableland of the Loess Plateau in Shaanxi in Recent Thirty Years, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12781, https://doi.org/10.5194/egusphere-egu23-12781, 2023.

The Jet Erosion Test (JET) is a method for determining the erodibility of incohesive agricultural soils by measuring the critical shear stress. The measurements were performed using a modified Mini-JET device, which is well-suited for field measurements as it is small, light, requires a relatively small amount of water, and can be operated by a single person. The Mini-JET device uses a water jet with a known kinetic energy to create an erosion crater in the soil, and then measures the rate at which the crater forms to determine the soil's erodibility and the critical shear stress. These parameters are needed for estimating the susceptibility of the soil to water erosion, and can help in the design of erosion control measures. The Mini-JET experiments were conducted on experimental plots in Risuty, central Czechia. Two soil with different properties were tested. In parallel with the experiments, a number of soil properties were monitored, including bulk density, soil texture, soil water content, aggregate stability, and total organic carbon. A total of 75 simulations were carried out as part of this study. The results of the Mini-JET experiments showed a large temporal and spatial variability in the soil erosion parameters. Despite this variability, the absolute values of the determined erodibility coefficients were comparable to those reported in previous studies. This indicates that the Mini-JET method is suitable for studying the erodibility of agricultural soils, although a sufficient number of replicates must be carried out to obtain representative values. The information obtained with the Mini-JET method can be used in physically based soil erosion models, which are used to predict the erosion of soil and the effectiveness of erosion control measures.  

Research has been supported by project TUDI (European Union's Horizon 2020 research and innovation programme under grant agreement No 101000224) and LTA-USA 19019 (Ministry of Education of the Czech Rep.).

How to cite: Vrana, M., Zumr, D., Krasa, J., and Dostal, T.: Evaluating Erosion Risk on Agricultural Soils with the Modified Mini-JET Device, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5135, https://doi.org/10.5194/egusphere-egu23-5135, 2023.

Raindrop splash engenders the dispersion and transport of the soil particles,  that is the primary stage in the process of soil erosion. Raindrops with different diameters may have different influences on different soil structures. The research objective was to quantitatively and visually analyze the change in surface aggregates and pore microstructure of five soils (Eum-Orthic Anthrosol, Ustalf, Cumulic Haplustoll, Ustochnept and Quartisamment) in the Loess Plateau caused by various raindrop diameters (2.67, 3.39 and 4.05 mm) using rainfall tests, synchrotron-based X-ray micro-computed tomography (SR-μCT) and digital picture processing. Surface aggregate fragmentation and pore plugging rose as growing raindrop diameter. Under raindrop splash, the increase in raindrop diameter increased the number of microaggregates (≤ 250 μm) of Cumulic Haplustoll, Ustalf and Eum-Orthic Anthrosol; the irregular pore-shape factor of Quartisamment and Ustochnept; and the total number of aggregates and pores. Moreover, the soil physicochemical properties also had a significant impact on surface aggregate breakdown and pore plugging (P < 0.01). Higher sand contents made the soil structure of Quartisamment and Ustochnept more susceptible to splashing. The FD of Eum-Orthic Anthrosol, Ustalf and Cumulic Haplustoll were lower than those of Quartisamment and Ustochnept. The results showed that during rainfall, both raindrop diameter and soil properties affect surface aggregate stability and pore connectivity, which creates the material basis for forming surface crust, clogging pores and reducing the infiltration rate.

How to cite: Li, G.: Aggregate structure destruction and pore plugging caused by raindrop splashes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11478, https://doi.org/10.5194/egusphere-egu23-11478, 2023.

Within the scope of the TUdi project, EU Horizon 2020 Grant Agreement No 101000224, a questionnaire was responded to by more than 400 farmers from seven countries in Europe and China, aiming to assess farmers' major concerns and develop Decision Support Tools targeted at these issues. One tool currently being developed targets soil erosion and seeks to provide farmers with publicly available historical satellite imagery in a user-friendly platform, as well as guidelines on easy-to-use methodology to assess the degree of soil erosion on the field. The questionnaires also revealed that many farmers do not use official data or digital maps to help make management decisions but are willing to apply simple tools for assessing soil degradation processes. With this, the project hopes to contribute to democratizing access to science, helping farmers – ultimately, the ones who implement soil conservation practices – to make data-driven decisions on soil management and exploring alternatives. The preliminary version of this tool will be presented at the workshop.

Research has been supported by project TUDI (European Union's Horizon 2020 research and innovation program under grant agreement No 101000224)

How to cite: Falcao, R., Krasa, J., Dostal, T., Gomez, J., Llanos, M., and Guzmán, G.: A Decision Support Tool for soil erosion in agricultural fields in the European Union and China, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3595, https://doi.org/10.5194/egusphere-egu23-3595, 2023.

Combining organic and inorganic fertilizers is critical for increasing yield, reducing greenhouse gas (GHG) emissions, and improving soil fertility. However, the effect of combined organic and inorganic fertilizers on GHG emissions in hilly apple orchards is not clear. Furthermore, studies on slope agriculture mostly ignore slope runoff. Hence, a two-year field experiment was conducted in the hilly apple orchard in north Shaanxi to explore the effects of orchard management practices on surface soil water and temperature, GHG emissions, runoff, apple yield, and fruit quality. Three management practices were implemented: (1) combined organic and chemical fertilizer plus water-saving (OCWS) system; (2) chemical fertilizer plus water-saving (CWS) system; (3) conventional practice plus chemical fertilizer without water-saving system (CC). The results showed that, relative to CWS and CC treatments, the OCWS treatment decreased the average surface soil temperature during the apple growing period by 5.54% and 4.54% and increased surface soil water by 8.39% and 10.42%, respectively. Seasonal variation in N₂O, CO₂, and CH₄ followed similar trends across treatments, but the amplitude of change varied. Soil water and temperature affected GHG emissions. Cumulative N₂O, CO₂, and CH₄ emissions varied non-significantly among treatments. Furthermore, the OCWS treatment had a similar global warming potential (GWP) to the CC treatment. The OCWS treatment had a 39.33% lower greenhouse gas intensity (GHGI) than the CC treatment. Averaged across two years, the OCWS and CWS treatments significantly reduced runoff by 49.18% and 43.90% and sediment yield by 72.13% and 68.65% compared to the CC treatment. Furthermore, precipitation had a significant positive correlation with runoff and erosive sediment. Averaged across two years, the OCWS treatment had the highest apple yield (37,550 kg hm^–2), crop water production (CWP) (69.40 kg hm^–2 mm^–1), transverse diameter (84.27 mm), single fruit weight (261.49 g), vitamin C (29.45 mg kg^–1), soluble solids (14.28%), soluble sugars (10.74%), and sugar: acid ratio (54.95). The OCWS treatment is an effective management practice for increasing apple yield, improving fruit quality, and reducing adverse environmental impacts on the Loess Plateau in northwest China.

How to cite: Zhang, B., Yan, S., Wu, S., Feng, H., Meng, Q., and Siddique, K. H. M.: Effect of combining organic and chemical fertilizer plus water-saving system on greenhouse gas emissions, runoff, apple yield and quality in a hilly rainfed apple orchard, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1037, https://doi.org/10.5194/egusphere-egu23-1037, 2023.

Soil erosion is a global environmental problem.  The rapid monitoring of the coverage changes in and spatial patterns of photosynthetic vegetation (PV) and non-photosynthetic vegetation (NPV) at regional scales can help improve the accuracy of soil erosion evaluations.  Three deep learning semantic segmentation models, DeepLabV3+, PSPNet, and U-Net, are often used to extract features from unmanned aerial vehicle (UAV) images;  however, their extraction processes are highly dependent on the assignment of massive data labels, which greatly limits their applicability.  At the same time, numerous shadows are present in UAV images.  It is not clear whether the shaded features can be further classified, nor how much accuracy can be achieved.  This study took the Mu Us Desert in northern China as an example with which to explore the feasibility and efficiency of shadow-sensitive PV/NPV classification using the three models.  Using the object-oriented classification technique alongside manual correction, 728 labels were produced for deep learning PV/NVP semantic segmentation.  ResNet 50 was selected as the backbone network with which to train the sample data.  Three models were used in the study;  the overall accuracy (OA), the kappa coefficient, and the orthogonal statistic were applied to evaluate their accuracy and efficiency.  The results showed that, for six characteristics, the three models achieved OAs of 88.3–91.9% and kappa coefficients of 0.81–0.87.  The DeepLabV3+ model was superior, and its accuracy for PV and bare soil (BS) under light conditions exceeded 95%;  for the three categories of PV/NPV/BS, it achieved an OA of 94.3% and a kappa coefficient of 0.90, performing slightly better (by ~2.6% (OA) and ~0.05 (kappa coefficient)) than the other two models.  The DeepLabV3+ model and corresponding labels were tested in other sites for the same types of features: it achieved OAs of 93.9–95.9% and kappa coefficients of 0.88–0.92.  Compared with traditional machine learning methods, such as random forest, the proposed method not only offers a marked improvement in classification accuracy but also realizes the semiautomatic extraction of PV/NPV areas.  The results will be useful for land-use planning and land resource management in the areas.

How to cite: He, J., Lyu, D., He, L., Zhang, Y., Xu, X., Yi, H., Tian, Q., Liu, B., Zhang, X., Gomez, J. A., Krasa, J., Dostal, T., and Laburda, T.: Combining Object-Oriented and Deep Learning Methods to Estimate Photosynthetic and Non-Photosynthetic Vegetation Cover in the Desert from Unmanned Aerial Vehicle Images with Consideration of Shadows, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2479, https://doi.org/10.5194/egusphere-egu23-2479, 2023.

Arid areas in the world are pressed to grow more crop per drop of water to meet food security. Soil salinity, an unavoidable challenges in arid areas is exacerbating the situations. Management practices such as use of salt tolerant crops including cotton and sugarbeet, plastic mulched drip irrigation, intercropping and application of biochar are often recommended and adopted in many arid areas including Xinjiang, one of the northwestern provinces in China with arid climate. Studying the effectiveness of these management practices, however, are often difficult, costly and time-consuming. For example. difficulty in obtaining information on the dynamics of soil water and salt restricts comprehensive understanding on the effectiveness of soil amendments such as biochar’s impact in increasing yield and optimizing irrigation schedules, while numerical simulations show promise. The objectives of this study were to simulate the dynamics of soil water, salt and root water update (RWU) of cotton and sugarbeet in monoculture and intercropping systems in an arid climatic condition to minimize soil water loss through optimal irrigation under plastic mulched drip irrigation systems. A 3-year field experimental results from a cotton and sugarbeet monoculture and intercropping systems from Xinjiang, China was used to calibrate and validate HYDRUS-2D model. Soil water and salt dynamics were measured at fields with biochar applied at 0 t ha-1 (CK), 10 t ha^-1 (B10) and 25 t ha^-1 (B25) and the soil hydraulic and solute transport parameters were optimized in HYDRUS-2D, that was calibrated and validated to satisfy the requirements of minimum simulation accuracy (R²>0.75, RRMSE<14.2% and NSE>0.73). Simulation showed that the application of biochar increased storage of soil water and salt. The RWU ranked as B10> B25> CK, which was consistent with soil water storage (SWS) and yield. Soil water balance components indicated that the application of biochar at 10 t ha^-1 increased RWU, reduced Ea and water drainage. to the results were helpful to understand the mechanisms of biochar and intercropping in increasing crop yield. The adjusted irrigation schedule can save up to 50 mm of irrigation water and 50 Yuan costs per hectare for farmers. The research provides a reference for agricultural production in arid and semi-arid areas.

How to cite: Wang, X., Li, Y., Biswas, A., Sang, H., Feng, H., Yu, Q., and He, J.: Integration optimal irrigation schedule with biochar applications can economize water and maintain yield in cotton&sugarbeet monoculture and intercropping, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3756, https://doi.org/10.5194/egusphere-egu23-3756, 2023.

Coexistence between species within plant communities is a key issue in the practice of revegetation, forest management, and biodiversity conservation. Vegetation restoration is critical to control soil erosion and improve the ecological environment on the Loess Plateau. Here, we investigate the interspecific relationships of dominant plants during natural vegetation succession on the Loess Plateau. The results suggest that, under the ecological process of environmental filtering, species within communities can reduce interspecific competition and promote species coexistence via spatial heterogeneity and temporal asynchronous differences. The ecological niche overlap index (O_ik) significantly and positively correlated with the strength of interspecific associations. Most species pairs had weak competition and more stable interspecific relationships. The results of the χ² test showed that 317 species pairs were positively associated and 118 were negatively associated. The community is in a positive succession process, and the interaction relationship between species tends to be neutral. We should enhance the protection of positively associated species and pay attention to negatively associated species during forest management. Results revealed that Boott and Lespedeza bicolor Turcz coexisted easily with other species for mutual benefit, which could help build artificial forestland of native species to improve the ecological function.

How to cite: Tian, Q., Zhang, X., Xu, X., Yi, H., He, J., and He, L.: Knowledge about Plant Coexistence during Vegetation Succession for Forest Management on the Loess Plateau, China, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4033, https://doi.org/10.5194/egusphere-egu23-4033, 2023.

The Loess Plateau has been experiencing large-scale ecological construction over the past  40 years. The watershed of Zhou River (1334 km² ) in the core land of the Loess Plateau was chosen as a case study to understand the impact of land use and cover change on the relationship between rainstorm and flood. The land use of the watershed in 1985, 2000 and 2015 was extracted from corresponding Landsat images and the series of event data from 1980 to 2019 of rainfall and runoff were collected from seven rain measuring stations and one gauging station (774 km²) distributed in the watershed. he different magnitude of rainstorm-flood was classified to investigate its responses of ecological restoration by mathematical statistics method. The results showed that the land use conversions were mainly from cropland to forest and grassland, and from grassland to woodland in the time. The proportion of forest and grassland increased from 60.5% in 1985 to 72.1% in 2000 and reached as 85.3% in 2015. While in the meantime, the rainstorm frequency and magnitude of quantity had no obvious trend, however, the annual maximum flood peak discharge in the watershed showed a significantly downward trend, and a change point occurred in 2003. Also the flood magnitude and frequency decreased significantly. Under the same peak discharge, the flooding lag time and runoff coefficient showed an obviously increasing trend compared to that before 2003. And after 2003, most of the floods turned to be once every two years (peak discharge of 169 m³/s) after that year. For floods greater than 10 year-return period, the runoff coefficient is mainly affected by forest land increasing, and the contribution rate is 0~78%. For floods less than 10 year-return period, the runoff coefficient is mainly affected both by the increase of forest land and grassland area, and their contribution rates are 0~57% and 11%~65%, respectively. Outcomes from this study are helpful to understand the shifts of the hydrological process with ecological restoration and assist the sustainable catchment management and land use planning on the Loess Plateau.

How to cite: An, Z., Zhang, X., He, L., Yi, H., He, J., Sun, W., Geng, W., Wang, H., Wang, Y., Zhang, Y., and Yu, K.: Ecological Restoration Declined the Rainstorm—Flood Relationship for past 40 years on Chinese Loess Plateau, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4094, https://doi.org/10.5194/egusphere-egu23-4094, 2023.

    To increase vegetation coverage and improve ecosystem services, the government has promulgated and implemented the program of "Grain for Green" from 1999 to the present. How and where vegetation cover increases and how land use changes are the determinant factors in regional water resources and hydrological regimes. On Chinese Loess Plateau (LP), an arid and semiarid area with fragmented topography and the transitional vegetation nature, accurate prediction of land use and vegetation change is particularly important. We employed a simple habitat analogy approach, the "Matching Tree Species with Site" principle and the Soil and Water Assessment Tool (SWAT) to predict the potential vegetation restoration and land use/land cover (LULC) change and investigated its impact on the hydrological regime in a watershed of Liujiahe. Results showed that the maximum recoverable vegetation cover of the Liujiahe watershed was 71.1%, where still 9.2% potential for the vegetation cover and the vegetation of 36.4% of the area continued to improve in the future. Under the current status of vegetation restoration, the areas suitable for future afforestation in the watershed are limited in the area of only 46.06 km²; on this basis, cropland will decrease by 47.4%, and grassland and forestland will increase by 15.8% and 0.7%, respectively, in comparison with 2020. However, SWAT results showed that vegetation restoration has already reduced annual mean runoff and soil water content (SW) by 44.2% and 43.9%, respectively, while evapotranspiration (ET) has increased by 12.6%, and the land use changes in the next 20-30 years will further reduce the runoff and SW by 15.6% and 11.1% respectively, and increase ET by 1.2%. Overall, large-scale vegetation restoration has greatly affected amounts and spatial-temporal distribution of hydrological regimes on the Loess Plateau. After 20 years of vegetation restoration, there is still room for further restoration in the area, however, considering the limited rainfall and water carrying capacity, the vegetation restoration of this watershed should be based on natural restoration or low water consumption grasses and shrubs to avoid a water resources crisis. These results is expected to provide a perspective for modelling LULC changes in areas with fragmented terrain and highly influenced by human activities, and to provide an important for underpinning sustainable management of natural resources on the LP under long-term ecological restoration.

How to cite: Yi, H., Zhang, X., He, L., He, J., Tian, Q., Zou, Y., and An, Z.: Detecting the future impact of the "Grain for Green" program on land use/ land cover and hydrological regimes in a watershed of the Chinese Loess Plateau, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5366, https://doi.org/10.5194/egusphere-egu23-5366, 2023.

Sustainability cannot be achieved without improving soil conditions. However, it is estimated that between 60 and 70% of EU soils are unhealthy. Thoughtful use of exogenous organic matter can help restore soil functions and thus improve soil health. Animal manures are the most abundant organic matter in agriculture and, in addition to their high nutrient content, they contribute to improving soil health in many ways by increasing soil biological activity. For these reasons, their efficient and environmentally friendly use is of major importance.

The TUdi project will contribute to develop healthy and productive agricultural ecosystems, where the organic fertilizers play an important role in the nutrient supply of the plants. The ongoing development of the nutrient management tool has to consider the different behavior and characteristic of these materials. Our study gives an example of how the long term field trials results can be implemented in this process.

37 trials have been selected from the database of the Hungarian field trials which contain the effects of farmyard manure and mineral fertilizer application on the basis of NPK nutrient equivalence. Among the various treatments, the yields of the absolute control, the farmyard manure treatment and the one with equivalent amounts of NPK in the form of mineral fertilizer were evaluated. The experiments were grouped according to the soil texture.

Annual fertilization was more favourable in all cases than periodic manure application. Differences between yield surpluses declined with an increase of soil clay contents. The efficiency of fertilization in both farmyard manure and fertilizer treatments were higher on sandy soils, which have the poorest natural nutrient supplying capacity.

The correlation between the changes in the organic matter (OM) content of the control plots soils, and differences of the responses to nutrient applied can be described by hyperbolic functions. A similar correlation was established between the AL—(ammonium lactate) soluble K contents and differences of the responses to farmyard manure and fertilizer.

As the values of these two soil parameters increased, the advantage of the nutrients given in the form of fertilizer over farmyard manure declined.

Keywords: long term field trial, manure application, fertilization, nitrogen use efficiency, nutrient advisory system

How to cite: Pirkó, B., Bakacsi, Z., Tóth, E., Szabó, A., Arendás, T., and Csathó, P.: Comparison of nitrogen use efficiency of manure and inorganic fertilizer based on long term field trials in Hungary, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12545, https://doi.org/10.5194/egusphere-egu23-12545, 2023.

Once one of the most severe soil loss regions worldwide, the Chinese Loess Plateau has experienced large-scale land use changes and vegetation restoration in the past few decades. Understanding how land use change affects soil erosion is critical in the region's ecological construction and land management. In this study, the Beiluo River Basin covering 26,905 km² in the hinterland of the Loess Plateau was selected to investigate vegetation restoration and its impacts on soil loss rates over the last 50 years. Results show that land use in the basin has changed considerably, mainly reflected in the upper reaches. From 1970–2020, cropland in the upper reaches decreased by 54%, directly leading to a 9.1-fold increase in forested land. Landsat-NDVI shows vegetation coverage increased from 21.1% to 69.9% over time. Vegetation coverage changed from 48.1% to 78.7% for the entire basin. The Chinese Soil Loss Equation (CSLE) was used and confirmed to be satisfactory with a high coefficient of determination (R², 0.89) and a strong Nash–Sutcliffe efficiency coefficient (0.72), although an underestimation exists. With the change in land use, the specific soil loss simulated in the upper reaches maintained a high rate of around 8,000 t·km⁻²·yr⁻¹ from the 1970s to the 1990s, dramatically dropping to 3,058 t·km⁻²·yr⁻¹ in the 2000s, then attenuated to 1,321 t·km⁻²·yr⁻¹ in the 2020s. For the entire basin, soil loss rates dropped from 4,090 to 1,848 and 890 t·km⁻²·yr⁻¹ from the 1970s to the 2000s and 2020s, respectively. Attribution analysis showed that the dominant factor in the change in soil loss rates in the 1980s and 1990s relative to the 1970s was the change in rainfall erosivity for the entire watershed. However, with vegetation coverage increasing to 59.0% in the 2000s, vegetation restoration rapidly converted to the dominant factor contributing 78.3% to soil loss decrease in that period. With expanding vegetation cover, its contribution grew to 84.9% in the 2020s. The shift is evident in each reach of the basin except the terrain-plain area with the majority of farmland. The findings are helpful for sustainable land use planning and socio-economic development on the Loess Plateau and in similar areas.

How to cite: He, L., Zhang, X., Liu, B., Guzmán, G., and Gómeza, J. A.: Using CSLE to find the dominant factor in the change of soil erosion in the past 50 years on the Chinese Loess Plateau, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1519, https://doi.org/10.5194/egusphere-egu23-1519, 2023.

Climate change affects soil organic carbon (SOC) and contributes to the uncertainty of terrestrial carbon sinks in the global carbon budget. With changes in vegetation growth and the regulation of its carbon input, the feedback of topsoil SOC to climate change is likely to become more complex at broad geographical scales. China has experienced noticeable changes in climate and surface greening in recent decades, and these changes have effectively influenced the dynamics of topsoil SOC. However, the potential role of vegetation carbon inputs in regulating and buffering climate change impacts on SOC in the context of current ecological restoration is still poorly understood. Therefore, to solve these problems, on the basis of the long-term satellite remote sensing data from 2000 to 2019, multiple linear regression and pathway analyses to investigate the dominant role of different climate factors and vegetation net primary productivity (NPP) on topsoil SOC changes in China, and further reveal the potential role of vegetation carbon inputs in regulating and buffering the effects of climate change on topsoil SOC. The results show that the overall trend of increase in topsoil SOC in China from 2000 to 2019 is significant (P < 0.05), and most regions show a good development trend in the future, except for some areas in the Central South, East, and Northeast regions, where a risk of degradation exists. Relative to climate change, the dominant areas of NPP impact on topsoil SOC in China occupy a considerable proportion, especially in the North, Northwest, and Central South regions, with area proportions of 68.15%, 49.52%, and 47.99%, respectively. Importantly, the indirect positive impacts of climate change on changes in topsoil SOC in China through vegetation carbon input offset the direct negative impacts in most areas. That is, over the past 20 years, increases in temperature and precipitation have led to decreases in topsoil SOC in most of China, whereas the ultimate net effect has been to increase topsoil SOC by promoting vegetation carbon input, particularly in the Loess Plateau region. Our study demonstrates that considering only the effects of climate change on SOC, while ignoring possible changes in carbon transfer from plants to soils, largely reduces the reliability of assessments of SOC stocks and their changes. These results have important implications for enhanced prediction of future SOC changes and provide references for terrestrial carbon sinks management strategies in the context of response to climate change.

Keywords: Topsoil organic carbon, Climate change, vegetation carbon input, Pathway analysis, China.

How to cite: Cen, Y., Gao, Z., Lou, Y., Liu, W., and Zhang, X.: Vegetation carbon input moderates the effects of climate change on topsoil organic carbon in China, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1132, https://doi.org/10.5194/egusphere-egu23-1132, 2023.

Soil moisture is the main factor limiting the revegetation and ecological restoration in the Loess Plateau region. Studying the change patterns of soil moisture across plantations is beneficial to the effective utilization of local soil moisture, meanwhile providing insights for scientific vegetation restoration. In this study, Robinia pseudoacacia (RP) plantations including 10, 15, 25, and 40 years (abbreviated as RP10, RP15, RP25, and RP40, respectively) were selected as the study objects, with the farmland (FL) and native grassland (NG) as controls. The variations of soil moisture and the intensity of soil desiccation at each site from 0–200 cm were analyzed in spring, summer and fall from 2015 to 2021. The results showed that the seasonal variation of precipitation had a strong influence on soil moisture, showing different degrees of lagging effect. The order of average soil moisture in seasons was fall > spring > summer and soil moisture in summer was significantly lower than that in fall and spring (p < 0.05). At depth, the vertical distribution characteristics of soil moisture were similar for RP plantations at the same season but varied within different seasons. The average soil moisture of RP plantations was significantly lower than that of FL and NG (p < 0.05) and showed a decreasing trend with the increase of stand age, which indicates that afforestation seriously increases soil moisture depletion. Furthermore, there were obvious soil drying layers in all RP plantations in different seasons, with the most severe intensity of soil drying in the 150–200 cm soil layer. This study highlights the long-term dynamics in soil moisture of RP plantations, providing insights for sustainable soil moisture use and rational land use management in the loess hilly areas of China.

How to cite: Han, F., Peng, W., Fei, H., and Li, Y.: Soil moisture dynamic and desiccation effect of Robinia pseudoacacia plantation sequences in the loess hilly area, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1827, https://doi.org/10.5194/egusphere-egu23-1827, 2023.

The nonstationarity exists in the drought indicator series, making drought monitoring and assessment more complex and accurate. Our study aimed to better identify and monitor meteorological, agricultural, and hydrological droughts in the Yellow River Basin (YRB) of China. We constructed the temporal-variate nonstationary standardized drought indices for precipitation (NSPI), evapotranspiration (NSPEI), soil moisture (NSSMI), and runoff (NSRI) based on nine Generalized Additive Models for Location, Scale, and Shape (GAMLSS). Further, we investigated the performance of NSPI/NSPEI/NSSMI/NSRI by comparing with the historical drought events in YRB. The results show that: (1) The probability distribution function (PDF), smoothing function (SF), and degree of freedom (DF) had a significant influence on the fitting goodness of the GAMLSS model. Additionally, PDF was the most important factor to determine the fitting goodness, while the appropriate SF and DF improved the fitting effects of the model. (2) The stationary GAMLSS model mainly was applied to lower-timescale series, and the nonstationary GAMLSS models were more suitable for the higher-timescale series. (3) The NSPI and NSPEI were more sensitive to identifying meteorological drought, but NSPEI was more accurate in identifying drought intensity and duration. The agricultural drought identified by NSSMI agreed well with the historical drought events but had a poor response to mild and moderate drought. (4) Form NSRI, hydrological drought in the tributaries of the YRB was affected by meteorological drought, and the intensity of hydrological drought was heavier than that in the mainstream of the YRB. In conclusion, the nonstationary drought indices could identify drought events more accurately and provide valuable information for drought-resistant work in the YRB.

How to cite: Niu, B., Li, Y., Liu, D. L., Wei, K., Jiang, X., Yao, N., Feng, H., Yu, Q., He, J., Yang, Z., Jiang, Y., Yang, G., and Lin, H.: Improved identification and monitoring of meteorological, agricultural, and hydrological droughts using the modified nonstationary drought indices in the Yellow River Basin of China, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2483, https://doi.org/10.5194/egusphere-egu23-2483, 2023.