Displays

Land use change is a global issue with tremendous social, economic and environmental implications. Currently, many countries display high rates of deforestation and forest conversion from native forest to industrial tree plantations which have a direct impact on soil C and N stocks. Even though, there is a significant number of studies that highlighted the effects of forest substitution on C sequestration, the impact on ecological stoichiometry and biogeochemical cycling has not been well assessed. The soils considered in this study encompass the main forest soil types found in south central Chile representing a range of soil properties and mineralogy (crystalline to amorphous ash derived soils). To reduce confounding factors due to site history, we exclusively selected pair sampling sites (native versus plantation) that shared a similar land-use history and had close to identical soil and geomorphic conditions in which two independent 625m² plots were established at adjacent Native Forests (NF) and Pine Plantations (PL).To determine C:N:P inventories alongside N and P available pools, the plot was divided into four sub-quadrants where bulk soil samples were collected at 6 depth intervals in the central soil pit and in four augers at each quadrant up to a depth of 240 cm. The C and N total pools were significantly different between soil types but not between forest types (p=0.02). The highest average C stock across all soils was found in NF (202.22 ± 82.77 Mg ha^-1) compared to PL (172.55 ± 87.73 Mg ha^-1)^. When comparing each soil type individually, disregarding forest type, the Young Ash soil displayed significantly higher C and N than all the other studied soils. On the contrary, the Recent Ash soil displays changes in the C:N:P stoichiometry_. Available Phosphorus was significantly different among sites, but not for forest types across sites. Overall, native forest exhibits higher stocks of available NO₃^- and we did not find a significant effect of forest type in NH₄⁺ stocks. Our result indicates the differential capacity that contrasting soils have to resist this major soil biogeochemical pools alteration.

How to cite: Crovo, O., Aburto, F., Albornoz, M., and Southard, R.: Differential responses of soil Carbon,Nitrogen and Phosphorus stocks and available pools to conversion from native forest to exotic plant plantation in soils of contrasting origin., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20760, https://doi.org/10.5194/egusphere-egu2020-20760, 2020.

This multidisciplinary project investigates the implications of aridification induced by climate change and human-induced land-cover land-use change in semiarid landscapes of Turkey on erosion dynamics and landscapes patterns and morphology. Deviations from climate mean states will result in loss of vegetation productivity and soil fertility in these water-limited ecosystems and exacerbate the natural conditions in terms of natural land‑cover and soil protection for natural resources sustainability. Here, we offer a comprehensive modelling framework to explore the water-soil-vegetation interactions under climate change for the following decades.

Remotely‑sensed vegetation indices and maps will be used to identify the regions where are prone to land‑cover change under climate change. Hence, the climate projections for the 21^st century taken from CMIP6 model experiments will be used for anticipating the potential changes in ecosystem dynamics and boundaries in these water-limited ecosystems. Moreover, these climate projections will be used as forcing data in a vegetation-coupled landscape evolution model to understand how the landscape morphology and erosion dynamics interact with changing climate in Turkish arid lands. Besides erosion dynamics, the future of the unique geomorphic landscape feature of these regions, the Turkish badlands, will be investigated based on climate projections.

The outcomes of this project will enhance the comprehension of the effects of geomorphic, hydrological, and ecological processes on natural resources under climate change in semiarid Turkish landscapes.

How to cite: Yetemen, Ö., Avcıoğlu, A., Çağlar, F., Ekberzade, B., Çetiner, U., Şen, Ö. L., Görüm, T., Göğüş, O. H., Yeo, I.-Y., Han, S.-C., and Chun, K. P.: A co-evolutionary modelling framework for water-soil-vegetation interactions in Turkish semiarid landscapes for sustainable natural resources under climate change, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21689, https://doi.org/10.5194/egusphere-egu2020-21689, 2020.

Gully sidewall expansion is an essential process of gully development, and its trigger condition and dynamic process are subject to multifactor effects. This study consisted of 10 sets of experiments, and three factors were considered: three rainfalls (60 mm, 48mm and 24mm), two initial slope gradients (70° and 80°) and two slope heights (1 m and 1.5 m). Then the increase-rate-analysis method was used to evaluate the variations in the changes of slope gradients of sidewall and retreat rates of gully shoulder-line with respect to changes in other causal parameters of rainfall and topography. The results are shown as follows: (1) The area of land loss of the upper gentle slope was positively correlated with the volume of gravity erosion. The correlation coefficient between the volume of gravity erosion and the area of land loss of the upper gentle slope, r₁, is 0.91. The correlation coefficient between the volume of water erosion and the area of land loss of the upper gentle slope, r₂, is 0.59. This shows that mass failure was the main cause to induce the land loss of the upper gentle slope in the process of sidewall expansion. (2) The rainfall duration and initial slope gradient had significant influences on the change of slope gradient of landform in the experiments. The sensitivity coefficients of rainfall intensity, rainfall duration, initial slope gradient and slope height for the change of slope gradient of the sidewall were 0.3, 2.2, 1.3 and -0.2, respectively. The increased initial slope gradient and rainfall duration may have caused the increases of the volume and number of gravity erosion, ultimately resulting in a remarkable change of slope gradient of the sidewall. (3) The most significant factor affecting the retreat rate of gully shoulder-line were rainfall intensity and initial slope gradient. The sensitivity coefficients of the rainfall intensity, rainfall duration, initial slope gradient and slope height for the retreat rate of gully shoulder-line were 3.0, 1.5, 3.0 and -0.1. As a result, the retaining wall construction was preferable to control the gully sidewall erosion. The results of this study may be referred for analyzing the mechanism of sidewall expansion and controlling the loess sidewall expansion.

How to cite: Yulei, M. and Xiangzhou, X.: Sensitivity analysis of gully sidewall expansion to topography and rainfall factors, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2240, https://doi.org/10.5194/egusphere-egu2020-2240, 2020.

The Mediterranean region has been identified as one of the most affected global hot-spots for climate change. Recent climate change in the Mediterranean can be characterized by faster increasing temperatures than the global mean and significant decreases in annual precipitation. Besides, important land cover changes have occurred, such as reforestation, agricultural intensification, urban expansion and the construction of many reservoirs, mainly with the purpose to store water for irrigation. Here we study the impacts of these changes on several ecosystem services in the Segura River catchment, a typical large Mediterranean catchment where many of the before mentioned changes have occurred in the last half century. We applied a hydrological model, coupled with a soil erosion and sediment transport model, to study the impact of climate and land cover change and reservoir construction on ecosystem services for the period 1971-2010. Eight ecosystem services indicators were defined, which include runoff, plant water stress, hillslope erosion, reservoir sediment yield, sediment concentration, reservoir storage, flood discharge and low flow. To assess larger land use changes, we also applied the model for an extended period (1952-2018) to the Taibilla subcatchment, a typical Mediterranean mountainous subcatchment, which plays an important role in the provision of water within the Segura River catchment. As main results we observed that climate change in the evaluated period is characterized by a decrease in precipitation and an increase in temperature. Detected land use change over the past 50 years is typical for many Mediterranean catchments. Natural vegetation in the headwaters increased due to agricultural land abandonment. Agriculture expanded in the central part of the catchment, which most likely is related to the construction of reservoirs in the same area. The downstream part of the catchment is characterized by urban expansion. While land use changed in more than 30% of the catchment, most impact on ecosystem services can be attributed to climate change and reservoir construction. All these changes have had positive and negative impacts on ecosystem services. The positive impacts include a decrease in hillslope erosion, sediment yield, sediment concentration and flood discharge (-21%, -18%, -82% and -41%, respectively). The negative impacts include an increase in plant water stress (+5%) and a decrease in reservoir storage (-5%). The decrease in low flow caused by land use change was counteracted by an increase in low flow due to reservoir construction. The results of our study highlight how relatively small climate and land use changes compared to the changes foreseen for the coming decades, have had an important impact on ecosystem services over the past 50 years.

How to cite: Eekhout, J., Boix-Fayos, C., Pérez-Cutillas, P., and de Vente, J.: The impact of land use change, climate change and reservoir construction on ecosystem services in a Mediterranean catchment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7177, https://doi.org/10.5194/egusphere-egu2020-7177, 2020.

Thanks to their carbon uptake potential, which produces a negative radiative forcing, forests are considered a major natural mitigation strategy for global warming. Because of their relatively low albedo, however, previous assessments have shown that the effectiveness of afforestation rapidly decreases with latitude. Here, we revisit the problem by taking land-atmosphere feedbacks into account and especially the impact of vegetation on the timing of cloud formation and the probability of convective precipitation. Using a soil-plant-atmosphere continuum model coupled to a mixed layer model of the atmospheric boundary layer (ABL), we explore variations in the local surface energy balance and diurnal evolution as a function of biomes and latitude. We show that the increased evapotranspiration from forests causes an anticipation in the crossing between the ABL and the lifting condensation level a phenomenon that can lead to earlier cloud formation. This provides an extra cooling effect, which counterbalances the positive forcing of land-surface albedo. As a result, the negative effects of albedo changes appear less limiting, making afforestation a more viable strategy in a wider range of latitudes.  

How to cite: Cerasoli, S., Yin, J., and Porporato, A.: Land-atmosphere feedbacks reduce positive albedo forcing of afforestation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12705, https://doi.org/10.5194/egusphere-egu2020-12705, 2020.

Saltwater contamination seriously affects groundwater quality and land productivity of coastal farmland along the Venice lagoon, Italy. Characterizing seawater intrusion dynamics represents a fundamental step to better understand its effect on soil and groundwater quality and in turn, conceive mitigation strategies. To this end, a three-year study was conducted in an experimental field bounding the southern Venice Lagoon. Volumetric water content, soil matric potential and apparent electrical conductivity (ECa) were monitored by five automatic monitoring stations at four depths (0.1, 0.3, 0.5 and 0.7 m). Groundwater electrical conductivity (EC) and depth to the water table were measured at the five stations. In addition, soil pore water at the four depths and borehole groundwater samples were collected periodically and analyzed for chemical composition. Physical and chemical analyses of the soil profiles were also carried out. Relationships between Cl^-, Na⁺, Mg^2+, Ca²⁺, K⁺, SO₄^2-, Br^- ionic concentrations, EC and soil characteristics (e.g. texture, EC1:2, exchangeable cations) were calculated by Pearson and Spearman correlation. Kruskal Wallis test was performed to test the five monitoring stations. Moreover, specific molar ratios (Cl/Br, Br/Cl, Na/Cl and K/Cl) were calculated in order to identify the main drivers affecting salinity in the field. EC and ionic concentrations showed high variability across the monitoring stations and between the different sampling dates (e.g. groundwater EC ranged between 0.33 and 17.46 dS/m). Higher EC and ionic concentration values were observed during upward soil water movement, while values were lower during percolation events (e.g. maximum Cl^- concentrations were 9227.3 mg/l and 3436.1 mg/l, respectively). An high correlation resulted between Na⁺ and Cl^- ionic concentrations and EC data in four out of the five monitoring stations (r values between 0.82 and 0.92). In addition, Kruskal Wallis test showed a significant difference between EC and chemical data sampled at the five monitoring stations and different soil depths. These results allow to conclude that soil and water salinity originated from different processes such as seawater intrusion and deep brines upcoming. Understanding salinization sources would enable the definition of a mitigation strategy able to enhance land productivity and water quality.

How to cite: Zancanaro, E., Teatini, P., Scudiero, E., and Morari, F.: Hydrogeochemical evidence of seawater intrusion: a case study in Venice farmland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14674, https://doi.org/10.5194/egusphere-egu2020-14674, 2020.

The Greater Manchester Brownfield Ground Risk Calculator (BGR_calc) is a Geographical Information System (GIS) spatial decision support tool designed to provide an early indication of potentially abnormal ground conditions and the indicative costs of mitigating them. This is important because abnormal ground conditions can affect the viability of the constructing of new homes on post-industrial brownfield sites. Multi-criteria decision analysis methods were used process and utilise over 30 input dataets. BGR_calc comprises four primary outputs, each represents a different set of ground risk or cost mitigation characteristics that occur within the Greater Manchester area, presented alongside their associated input data. Each output comprises risk scores (scored between 0 to 1) or risk mitigation cost estimates (£) presented as 50 m grid cells and site based summaries for over 2000 individual sites. BGR_calc makes the assumption that all brownfield land evaluated will be used to develop two storey residential housing at a density of 30 houses per hectare. Ground risk scores reflect the nominal risk that soil and groundwater contamination and soil and rock hazards might pose to human health, controlled waters and the structural integrity of new homes. The scores are derived from data on sources of contamination or ground conditions resulting from previous land-uses and/or natural processes, the presence of exposure pathways and sensitive receptors (residents, water resources and homes). For there to be a risk, the source, pathway and receptor components must be linked. Risk mitigation cost estimates represent the amount that might need to be paid to develop a brownfield site over and above ‘normal’ development costs.  No allowance is made in BGR_calc for the financial benefits of pre-existing infrastructure, proximity to services and employment that brownfield land usually have but these ought to be considered within the overall economic evaluation of individual sites.

How to cite: Marchant, A. P., Beriro, D., Nathanail, C. P., Cornillon, S., Freeborough, K., Smith, D. G., Bricker, S. H., Carr, M., Hoad, M., and Kingdon, A.: The Brownfield Ground Risk Calculator: A new spatial decision support tool for estimating ground risk and remediation costs for site located in Greater Manchester, UK, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22443, https://doi.org/10.5194/egusphere-egu2020-22443, 2020.

Sediment management can represent a key point for the water resources conservation, as the land use control can limit soil erodibility, ensuring a reduction of the silting volume in the reservoir. This study is focused on the nexus between coal mining activity and the hydrological cycle at the catchment scale, analysing how environmental interventions can be an excellent strategy against the impacts of former mining areas. Lake San Cipriano represents an excellent case study to explore the effects of mining activity on water storage because it is downstream of a river basin in which one of the most important lignite mine in central Italy has worked for years. A hydrological model is implemented on the Soil Water Assessment Tool (SWAT) to choose which decommissioning strategies brings the best results in terms of water resource conservation. Since no flow data are available, the model is calibrated in the solid transport equations, pointing to the convergence of the silting volume in the lake, which has been estimated thanks to multiple bathymetric campaigns carried out over the years. Two environmental restoration scenarios have been analysed: the first is only focused in the land use change with the afforestation of native plants; the second is a wider landscape restoration project that include also river bodies rehabilitation. The results show the quantitative effects of the proposed decommissioning strategies, showing the strong reduction of solid transport and reservoir silting in the two proposed scenarios.

How to cite: Lompi, M., Pacetti, T., and Caporali, E.: Evaluation of mining decommissioning strategies on catchment hydrology, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17725, https://doi.org/10.5194/egusphere-egu2020-17725, 2020.

The Philippines is known for its rich marine biodiversity and is deemed as the apex of the world’s coral triangle. However, sediment yield studies and river discharge measurements in the country are sparse if not non-existent. High sediment rates have detrimental effects on water quality and consequently to coral reef health and marine biodiversity. Thus, modeling of runoff and sediment yield at a watershed level is important in assessing coral community environments.

In this study, a Soil and Water Assessment Tool (SWAT) based sediment yield simulation was done for Lanuza Bay-- a site with high productivity but increasing mining activity. Two simulations were conducted. The first utilized a land-use map before January 2011 and was made to run from January 1998 to August 2018 in order to simulate a scenario in which mining operations did not occur in the area. The second simulation utilized an updated land-use map that incorporated mining sites from January 2011 to August 2018.

SWAT model results indicate that slope class was the primary determinant of erosion rates (slope band > 20%). The study suggests that consecutive precipitation occurrences affected soil erodability and induced a time lag between precipitation and sediment yield peaks. The highest contributors to sediment yield at a sub-basin level were identified to be areas adjacent to or coinciding in mining or excavation sites. Comparing the scenarios with and without mining, mining contributed to 4% of the increase in the watershed’s total annual sediment yield.

Qualitative and historical validation shows reasonable agreement between simulated values and satellite images. The output of this study can be used as a science-based reference in crafting laws and policies for land-use management and Marine Protected Area (MPA) planning.

How to cite: Maloles, P. J., Gallentes, A., and Villanoy, C.: SWAT-based sediment yield simulation with mining land-use change scenario in Lanuza Bay, Philippines, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12569, https://doi.org/10.5194/egusphere-egu2020-12569, 2020.

Gully erosion is recognised as a significant environmental issue. It affects grazing, croplands as well as rangelands. Of particular interest here are mining landscapes which are comprised of unconsolidated waste material that has little or no economic value. These landscapes are new systems with little nutrients and plant growth potential and the materials are often highly erodible and prone to gullying. Many empirical and physical models have been developed to understand gully initiation, growth and stabilisation. Here we demonstrate the use of computer based landscape evolution models to quantify the gully process. These models use a digital elevation model to represent the landform and allow the landform to evolve through time. The models can operate at sub-hourly through to millennial time scales. The landform (and resultant gully) can be visualised and rates of movement quantified and erosion rates calculated.  Different land surface properties such as vegetation cover, armour as well as climate variability can be investigated at the hillslope, catchment and landscape scale. These models offer a huge advance in visualisation and quantification of gully evolution. The models have been used across a wide range of materials and climates and will be demonstrated using several mining case studies. Of particular interest for the mining industry is how surface properties change through time as armouring and weathering occurs and vegetation establishes. Model strengths will be highlighted and areas where advances, particularly field data needs will be discussed.

How to cite: Hancock, G., Willgoose, G., and Welivitiya, D.: Gully erosion – the use of computer based landscape evolution models to predict initiation, growth and stabilisation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3734, https://doi.org/10.5194/egusphere-egu2020-3734, 2020.

In the course of brown coal mining, large amounts of soil, interseam and overburden material are moved and translocated. Ceasing mining activities, the disturbed landscape needs to be restored and a rapid development of functional soils is of utter importance for the rehabilitation of those areas. Simple backfilling of the overburden material is not sufficient, above all in areas with semi-arid or arid climate due to the lack of water driving the formation of structure and rebuilding of organic carbon (OC) and nutrient pool. In order to accelerate soil development and rehabilitation, new approaches using mixtures of different substrates and OC sources are tested. Testing such rehabilitation mixtures in field scale is time and resource consuming. We present a rapid and easy to perform laboratory approach to evaluate the performance of artificial soil mixtures for rehabilitation regarding the development of chemical, biological and structural features. We tested six different mixtures used for a rehabilitation program at a coal mine in southern Australia composed with increasing complexity using overburden material, fly ash, paper mulch and brown coal. In addition, we investigated the effect of a fresh plant litter addition.  

We performed a short-term laboratory incubation in microcosms for forty days at constant water tension. During the incubation, we monitored water content and microbial activity. After the incubation period, we evaluated soil structure formation by isolating water-stable aggregates and estimated pore sizes by calculating water-filled pore space. We investigated OC allocation in bulk soil, soil solution, aggregates and microbial biomass and calculated the microbial carbon use efficiency (CUE).

Our results showed that the more complex mixtures had a higher OC content and a wider CN ratio. Available nutrients in the soil solution were mainly provided by the additional components, because the overburden material alone showed very low element concentrations in the soil solution. The formation of water-stable aggregates was mainly driven by the addition of fresh plant litter and there was a predominant formation of large macroaggregates (0.63-30 mm), that stored >80% of the total OC. Microbial activity, as measured by CO₂ release, was high in all mixtures with fresh plant litter addition, but the highest microbial CUE was observed in the full rehabilitation mixture. Thus, the full rehabilitation mixture is considered to support sustainable microbial growth and has the potential for a rapid soil development. Also, we identified the OC input to be the main driver of early soil development in artificial soil mixtures influencing nutrient supply, microbial development and structure formation.

The study suggests that the presented experimental design is a functional and efficient test system for assessing the rehabilitation potential of different substrates and rehabilitation mixtures in a short-term lab approach.

How to cite: Bucka, F., Pihlap, E., Kaiser, J., Baumgartl, T., and Kögel-Knabner, I.: Testing the rehabilitation potential of post-mining soils: soil organic matter, microbial biomass and aggregate formation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3479, https://doi.org/10.5194/egusphere-egu2020-3479, 2020.

Soil organic matter (SOM) and extracellular polymeric substances (EPS) from biological processes are considered to be major contributors in aggregate formation. But there is limited knowledge on soil structural formation after reclamation – the step when SOM content is low and soil properties are mostly controlled by the parent material. In our study we used a chronosequence approach in the reclaimed open-cast mining area near Cologne, Germany to elucidate the development of soil structure and soil organic matter during initial soil formation in a loess material. We selected six plots with different ages of agricultural management after reclamation (0, 1, 3, 6, 12, and 24 years after first seeding). In each reclaimed field 12 spatially independent locations were sampled with stainless steel cylinders (100 cm³) at two depths in the topsoil (1-5 cm and 16-20 cm). Samples were wet sieved into four aggregate size classes of <63 µm, 63-200 µm, 200-630 µm and 630-2000 µm. Each aggregate size class was characterized by organic carbon (OC), total nitrogen (TN) and CaCO₃ concentration. The chemical composition of the SOM of selected samples was characterized using solid-state 13C NMR spectroscopy.

Wet sieving into aggregate size classes showed different trends along the chronosequence. Contradicting relation between CaCO₃ and OC contribution to aggregate size classes display two different mechanisms on soil aggregate formation in young loess derived soils. CaCO₃ influenced aggregation predominantly in finer aggregate size classes, where the highest concentration and contribution was measured. SOM, on the other hand, played an important role on formation of large macro-aggregates after organic manure application in year 4. Furthermore, the loss of total OC after year 12 was connected with the loss of OC contributing to the largest aggregate size class. Our findings reveal that SOM and CaCO₃ role on stabilizing aggregates is not equally distributed and is aggregate size class dependent.

How to cite: Pihlap, E., Steffens, M., and Kögel-Knabner, I.: The role of SOM and CaCO3 on soil aggregate development in reclaimed soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13644, https://doi.org/10.5194/egusphere-egu2020-13644, 2020.

Livestock production is the main source of livelihood in the arid and semi‐arid lands in Africa. However, desertification characterized by vegetation degradation and soil erosion is a major threat to the sustainability of land‐based production systems. Native rangeland forage species Cenchrus ciliaris L. (Buffel grass/African foxtail grass), Eragrostis superba Peyr. (Maasai love grass) and Enteropogon macrostachyus (Hochst. Ex A. Rich.) Monro ex Benth. (Bush rye grass) have been used to combat desertification. The objectives of the study were to identify the best‐suited native grass species to combat desertification in a semi‐arid environment in Kenya and to identify the preferred grass species among the agropastoralists in the area. Percentage basal cover, plant densities and frequencies of the three grasses in pure stands and mixtures were estimated. Grass species preferences were through household survey and focus group discussion. Results showed a significant difference (P < 0·05) in plant densities and cover estimates: E. macrostachyus was ranked first; C. ciliaris and E. superba were ranked second and third respectively. The agropastoral farmers, however, preferred E. superba followed by C. ciliaris and E. macrostachyus, a reverse trend. These results suggest that the choice of grass species to combat desertification is influenced more by its contribution as a source of forage for livestock than its contribution for rehabilitation purposes.

How to cite: Nyariki, D., Musimba, N., Nyangito, M., Mwang'ombe, A., and Mganga, K.: The choice of grass species to combat desertification in semi‐arid Kenyan rangelands is greatly influenced by their forage value for livestock, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20221, https://doi.org/10.5194/egusphere-egu2020-20221, 2020.

The global expansion of infrastructures is generating vast amounts of waste soil (soil excavated from construction sites that cannot be used on-site); the amount of waste soil accumulated in the European Union in 2014 was estimated at 463 x 10⁶ tons. The regulation and management of waste soil disposal are currently limited to: (1) local use for various engineering projects; (2) stockpiling on-site for future use; (3) transferal to landfills, which are currently overfilled, as padding material or for disposal. Despite a number of permitted actions for handling waste soil, a significant portion of it is disposed of in the area surrounding the construction site, thus raising the risk of pollution and landscape spoilage. Waste soils are commonly excavated from deep layers, and are therefore saline, sodic, and lack organic matter, preventing their use without pre-treatment. Moreover, due to the intensification of crop production, one-third of the global agricultural land area is susceptible to soil loss by erosion, constituting ~50% of total estimated soil erosion. Here we show a new approach for environmentally, agronomically and economically sustainable use of reclaimed waste soil to rehabilitate degraded agricultural land. In a 3-year field experiment under rain-fed conditions in a semi-arid region of Israel, we found that waste soil ploughed into agricultural soil had low erodibility, similar to that of the original agricultural soil, despite its high sodicity. Waste soil application tended to decrease the soil organic carbon concentration but had no detrimental effect on wheat hay yield or wheat grain yield or quality in the second and third year, respectively. The economic analysis suggested an average reduction of 8.7 million USD in waste soil disposal costs if 50% of the waste soil produced in Israel annually were to be utilized in agricultural fields. Thus, waste soil can be utilized successfully in degraded agricultural lands; this opens a new route to land reclamation and provides land managers and stakeholders with a sustainable way to reduce costs while transforming an environmental burden into a resource.

How to cite: Argaman, E., Becker, N., Tanner, S., Ben-Hur, M., Gruenzweig, J., Kimhi, A., Stavi, I., and Katra, I.: Using waste soil to rehabilitate degraded agricultural lands: environmental burden as resource, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4360, https://doi.org/10.5194/egusphere-egu2020-4360, 2020.

Abstract: Land use and climate change are recognized as two major drivers affecting surface streamflow. On the Chinese Loess Plateau, implementation of several land restoration projects has changed land cover in recent decades. The main objectives of this study were to understand how streamflow evolved on the Loess Plateau and how land use and climate change have contributed to this change. In this study, we selected 22 hydrological modelling studies covering 25 different watersheds in the Loess Plateau and we performed a meta-analysis by using the hydrological and metrological data collected from these studies. The results indicate a streamflow decrease in 41 of a total of 52 case studies whereas precipitation change was found to be non-significant in the majority of the cases. Streamflow reduction was estimated to be -0.46mm/year by meta-analysis across all case studies. Land use change was estimated to have 63.52% impact on the streamflow reduction whereas climate change accounted for 36.48% of the impact. Using meta-regression, an increasing soil and water conservation area was found to be positively correlated to streamflow reduction. We conclude that in the Chinese Loess Plateau, streamflow shows a decreasing trend and land restoration is the major cause of this reduction. To the knowledge of the authors, this is the first study that estimates streamflow dynamics across many watersheds on the entire Loess Plateau.

How to cite: Chen, H., Fleskens, L., Baartman, J., Wang, F., Moolenaar, S., and Ritsema, C.: Impacts of land use change and climatic effects on streamflow in the Chinese Loess Plateau: a meta-analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4586, https://doi.org/10.5194/egusphere-egu2020-4586, 2020.

Soil structure and soil organic matter (SOM) are closely linked characteristics describing the status of development of a soil. Their interactions affect various physical, chemical and biological soil properties and functions like water holding capacity, water infiltration, composition of the carbon pool and microbial activity. Rehabilitated soils from post mining fields are considered to have poor soil structure, low nutrient content and microbial activity. Besides disturbed soil properties, in Australia soil rehabilitation success is also influenced by climatic conditions like high evaporation rate which affects rebuilding of soil system functions. Although there are several studies looking into the development of soil properties post rehabilitation in temperate climates, the intertwined development of soil structure and quality and quantity of SOM during soil formation under water stressed environment is not clear until now.

In this study we used a space-for-time chronosequence approach in the rehabilitated open-cast mines at Yallourn Mine (Victoria, Australia) to elucidate the development of soil structure and soil organic matter after rehabilitation in a water limited environment. We selected five different fields with different rehabilitation ages (40, 22, 11, 4 and 3 years) and two mature soils that are used as grazing land. In each field we sampled 6 independent locations with stainless steel cylinders (100 cm³) at two depths of 0-4 cm and 10-14 cm.  All samples were analysed for bulk density, organic carbon (OC) and total nitrogen (TN) concentration. Selected samples were wet sieved into four aggregate size classes of <63 µm, 63-200 µm, 200-630 µm and >630 µm. For detecting OC contribution to aggregate formation, OC and TN was measured from each aggregate size fraction. This system is temporarily highly dynamic and shows different developments for bulk density and SOM stocks, which had an effect on the structure of the microbial communities. Along the space-for-time chronosequence we can observe soil structure formation with ageing and a build-up of a OM, which has a positive effect on recovering soil functionality.

How to cite: Pihlap, E., Bucka, F., Haberstok, T., Scholes, E., Klör, T., Baumgartl, T., and Kögel-Knabner, I.: Descriptors for soil development in a water limited environment of a rehabilitated open-cast mine site in south-east Australia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8114, https://doi.org/10.5194/egusphere-egu2020-8114, 2020.

The distribution of root system in the soil profile is an important factor for water and nutrient acquisition in planted forests. Harvest residue and litter layer management can alter nutrient availability to the plants, reflecting in shifts of root system distribution in the soil profile. In the present study, we aimed to evaluate the effect of litter layer management in root density and its correlation with depth, soil organic matter (SOM), and soil macro and micronutrients in fast-growing eucalypt plantations. We hypothesized that the presence of litter layer increases root density in the first soil layers while its absence results in higher root density in deeper soil layers. To this end we carried out an experiment in a eucalypt stand (Eucalyptus urophylla x Eucalyptus grandis; 3.3 x 1.82 m spacing; one-year-old trees) in the region of Telêmaco Borba, Paraná – Brazil. The Köppen climate classification is Cfb and the soil is classified as dystrophic Red Latosol. The treatments consisted of presence (+R) or absence (-R) of litter layer. The residue was composed by the previous rotation litter layer that remained in the forest after harvest. The experiment followed a randomized block design, with four replications. Root density (g dm^-3) was evaluated in one representative tree per plot at each treatment and replication. We used a 5.3 cm diameter auger to collect root samples from 0-10, 10-20, 20-40 and 40-60 cm depths in seven predefined points in the planting row and interrow. For each sampling point and depth, roots were manually separated, washed to remove soil and other impurities, and subsequently oven dried at 65 °C to determine total dry mass. Additionally, SOM, soil macro and micronutrient contents were analyzed in each soil layer. Pearson’s correlation (α=5%) was performed between root density, depth, SOM, soil macro and micronutrients. Contrary to our hypothesis, the results showed that the presence of litter layer did not impacted root density in the superficial layer (0-20 cm), but resulted in a substantial increase of this trait in deeper soil layers (20-40 cm and 40-60 cm). The increase in root density observed for deeper soil layers was possibly a consequence of the higher nutrient availability favored by the presence of litter layer. The increase of root density in subsurface is important not only to increase tree water and nutrient use efficiency, but also to promote C sequestration in deeper soil layers. Our results highlight the importance of maintaining the litter layer in the field as reasonable strategy for a more sustainable management of fast-growing eucalypt forests.

How to cite: Mendes Teixeira, A. P., Teixeira, P. P. D. C., Almeida, L. F. J., Silva, L. C. F., Silva, D. H. S., Stahl, J., Paiva, H. N. D., Vergütz, L., and Silva, I. R. D.: Root distribution as function of litter layer management in eucalypt stands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10951, https://doi.org/10.5194/egusphere-egu2020-10951, 2020.

Global environmental changes and other anthropogenic impacts are rapidly transforming the structure and functioning of ecosystems worldwide. These changes are leading to soil degradation with an estimated 25 % of the global land surface being affected. The need to develop cost-effective large-scale solutions to restore disturbed landscapes becomes imperative to preserve biodiversity and achieve ecosystem functionality and sustainability. As part of a large-scale industry-academia partnership, we have developed a soil research program that aims to build knowledge and design strategies to restore degraded landscapes in Western Australia and other dryland regions worldwide. Within this program, a series of laboratory experiments, glasshouse studies, and field trials, have been conducted over the past six years to advance our knowledge on soil limitations and to provide solutions to enhance soil carbon levels and restore above and belowground biodiversity in restoration programs. These studies include (i) the analysis of the influence of multi-species planting on soil organic carbon and microbial activity and diversity (ii) the evaluation of soil physicochemical and microbiological indicators to assess functionality of restored soils in degraded semiarid ecosystems and (ii) the development of nature-based strategies based on bio-tools (e.g. inoculation of soil biocrust cyanobacteria) to increase soil carbon and enhance overall soil function. In this presentation we will highlight some key findings of these studies that include the benefits of combining diverse plant species and using native microbes and organic amendments for increasing soil carbon and promote soil function in reconstructed soil substrates. We will also discuss the potential applicability of these bio-technological approaches in landscape-scale restoration programs.

How to cite: Muñoz-Rojas, M., Erickson, T. E., Bateman, A., Chilton, A. M., and Merritt, D. J.: Soil native microbes and multi-species planting for restoring soil function in dryland rehabilitation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11750, https://doi.org/10.5194/egusphere-egu2020-11750, 2020.

Soil is an essential and non-renewable resource in natural and agricultural ecosystems with extremely slow formation and regeneration potential. In dryland areas, many ecosystems are being seriously affected by degradation processes because of an excessive use of agro-chemicals, deep tillage and intensive irrigation, among many other factors. The decline in soil organic matter is also becoming a major cause of soil degradation, particularly in dryland regions where low soil fertility cannot always maintain a sustainable production. The use of organic amendments in ecosystem restoration programs can be an effective technique for promoting soil restoration processes in degraded drylands and several studies have shown their benefits for improving soil physical, chemical and biological properties. This recovery is a result of the rapid increment of organic matter and clay contents in the soil in the short term. In the long-term, soil structure becomes more stable and water holding capacity, permeability and infiltration are improved, whereas surface runoff and erosion are reduced. Nevertheless, there are many research gaps in the knowledge of the effects of climatic conditions on their application, as well as the adequate types of amendment and doses and decomposition rates. In this presentation, we evaluate the role of organic amendments as an effective strategy in dryland restoration, highlighting the effects of different amendment types, doses and application rates. We will specifically address: (1) type of amendments and benefits arising from their use, (2) application methods and more appropriate doses and, (3) potential risk derivates for their application. We also showcase some recent case studies using organic amendments in degraded dryland areas from Spain and Australia.

How to cite: Hueso-Gonzalez, P. and Muñoz-Rojas, M.: Soil organic amendments for restoring degraded drylands: strategies, recommendations and challenges for large-scale application, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11867, https://doi.org/10.5194/egusphere-egu2020-11867, 2020.

Land degradation, as a result of increased soil erosion and loss of fertility among other factors, is currently one of the most serious environmental problems. In recent years, the role of cyanobacteria from soil biocrusts in re-establishing soil function of degraded areas is gaining interest due to the potential of these organisms for soil stabilization and increase of soil fertility. In order to fully exploit the use of cyanobacteria in large-scale restoration of degraded lands, new approaches that facilitate their application must be explored in order to face with the harsh abiotic conditions of these environments. In this presentation, we showcase two different methods for the inoculation of cyanobacteria from soil biocrust in degraded soils of Australian dryland ecosystems: i) direct inoculation of cyanobacteria cultures and ii) incorporation of cyanobacteria within extruded pellets. Three soil native cyanobacterial strains from two representative N-fixing genera (Nostoc and Scytonema) and a non-heterocystous filamentous genus (Leptolyngbya) previously collected from the Pilbara region (north-west Western Australia), were used as inoculum. Then, in a multifactorial microcosm experiment under laboratory conditions, we evaluated the survival and establishment of the cyanobacteria for both methods. For the direct inoculation, cultures of isolated cyanobacteria and a mixture of them were applied as a liquid inoculum directly into a degraded soil from the Pilbara. In the case of application using extruded pellets, fresh cultures of each strain alone and an equal mixed of them were added into a substrate composed of commercial bentonite powder and sand (1:10 weight ratio). The composed solution was extruded through a jerky gun with an extruder nozzle into pellets (1 cm diameter x 2 cm length) and dried at 30^oC for 24h. Pellets were then placed on the surface of three different degraded soils representative of Australian drylands: a mine waste from an active mine site in the Pilbara, a degraded soil from the Cobar Peneplain (New South Wales), and a soil from the Simpson Strzelecki Dunefields (South Australia). In both experiments, cyanobacteria growth and establishment were monitored. Our results showed that in both treatments cyanobacteria colonize almost the entire Petri dish surface in all treatments. Furthermore, the levels of chlorophyll a (a proxy for cyanobacterial biomass) remained constant on inoculated samples during the study period, suggesting that cyanobacteria survived the pelleting process. In the case of direct inoculation, a decrease of chlorophyll a was observed in the beginning but then it stabilized and started to increase at the final stage of the experiment. This process may be due to the adaptation period of the cyanobacteria in the new environment, which is most progressive in the case of pellets application. Overall, our results showed that cyanobacteria can be successfully applied as a liquid inoculum and incorporated into extruded pellets, quickly colonizing degraded soi substrates. These technologies are ready for further testing and refining through field trials, opening a wide range of opportunities to face with large scale restoration programs.

How to cite: Jiménez-González, M. A., Roman, J. R., Canton, Y., Almendros, G., Chilton, A. M., and Muñoz-Rojas, M.: Development of cyanobacterial application methods for soil protection and restoration: case studies in Australian drylands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11907, https://doi.org/10.5194/egusphere-egu2020-11907, 2020.

Over the past few decades, there has been over increasing pressure on land due to population growth, urbanization, agriculture expansion and industrialization. The change in land use and land cover (LULC) pattern are highly dependent on human intervention. Deforestation pattern has started due to growth of suburbs, cities, and industrial land. The alarming rate in change of LULC pattern was on a rising trend since 1990s and has been increasing over time. This study focuses on analyzing the changes in LULC pattern in Dublin, Ireland over the past two decades using remotely sensed LANDSAT satellite imagery data, and quantify the effect of LULC change in streamflow simulation in watershed at Dublin by using rainfall-runoff model. Benefit of using remotely sensed image to investigate LULC changes include availability of high-resolution spatial data at free of cost, images captured at high temporal resolution to monitor the changes in LULC during both seasonal and yearly timescale and readily availability of data. The potential classification of landforms has been done by performing both supervised as well as unsupervised classification. The results obtained from the classified images have been compared to google earth images to understand the accuracy of the image classification. The change in LULC can be characterized by changes in building density and urban/artificial area (build up areas increase due to population growth), changes in vegetation area as well as vegetation health, changes in waterbodies and barren land. Furthermore, a set of indices such as vegetation index, building index, water index and drought index were estimated, and their changes were monitored over time. Results of this analysis can be used to understand the driving factors affecting the changes in LULC and to develop mathematical models to predict future changes in landforms. Soil Water Assessment Tool (SWAT) based rainfall-runoff model were used to simulate the changes in runoff due to the LULC changes in watershed over two decades. The developed framework is highly replicable because of the used LANDSAT data and can be applied to generate essential information for conservation and management of green/forest lands, as well as changes in water availability and water stress in the assessed area.

How to cite: Basu, B., Sarkar Basu, A., Sannigrahi, S., and Pilla, F.: Investigating land use and land cover changes in Dublin, Ireland using Satellite Imagery: A comparative analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12132, https://doi.org/10.5194/egusphere-egu2020-12132, 2020.

The depletion and degradation of native plant communities is a major threat to the long-term health and functionality of many ecosystems worldwide. Some of the current challenges in mine rehabilitation programs are poor recruitment and establishment of native plants. Indigenous soil bacteria, including cyanobacteria from soil biocrusts, have shown promise as bio-fertilizers as they may promote germination and enhance seedling growth of native plants in reconstructed soil profiles. In this research, we assessed the potential of bioinoculants composed by locally sourced soil bacteria from the rhizosphere and cyanobacteria from biocrusts, to promote germination and growth of native arid plants from Western Australia and New South Wales (Australia). Individual cyanobacteria species (e.g. Leptolyngbya sp, Nostoc sp. and Microcoleus sp), a cyanobacteria mix of these three species, and enrichments of soil bacteria from the rhizosphere were considered as inoculum for seed bio-priming. Overall, our results showed that lower concentrations of cyanobacteria inoculants (1 g l^-1) are more effective for promoting seedling growth than highly concentrated inoculum (5 g l^-1). The effects of the cyanobacterial/bacterial inoculants were specific to each plant species. However, biopriming seeds with soil bacteria and the cyanobacteria mix resulted in three times larger roots in hummock grasses (e.g. Triodia epactia) compared to the control treatment. We also identified the bio-active components or metabolites produced by targeted cyanobacteria species through GC/MS analyses. Our results showed that some of the cyanobacterial inoculants produced substances chemically like plant hormones such as auxins, i.e. indole-3-acetic acid. The positive effects of the native soil bacteria and cyanobacteria inoculants on native plants could be related to their ability of promoting nutrient bioavailability, improving stress resistance, protection against other microbes, and production of substances that may act as hormones. The findings of this research can allow selecting the most effective bio-active inoculants for application in seed-based land rehabilitation programs.

How to cite: Mahado de Lima, N., Charlesworth, J., Stewart, J., and Muñoz-Rojas, M.: Indigenous soil bacteria as bioinoculants for promoting seedling growth of native plants in arid land rehabilitation , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13204, https://doi.org/10.5194/egusphere-egu2020-13204, 2020.

Freshwater ecosystems have higher proportions of extinct and threatened species than terrestrial and marine ecosystems, with populations of vertebrates declined by 83% between 1970 and 2018. The pressing question is: what are the main drivers for this decline? Here we investigate the reasons for the loss of freshwater biodiversity using globally available gridded datasets at 0.5° spatial resolution on precipitation and temperature, land cover and land use, water use and dams as well as daily hydrological streamflow simulations from the ISIMIP initiative.

Across the past 50 years, we constructed annual change maps of the environmental variables along the global river networks and calculated time-variant indicators of hydrologic alteration (IHA) to depict hydrological change. We then calculated normalized indicators (e.g. proportion of threatened species) describing the current freshwater biodiversity status through species data aggregation of the International Union for Conservation of Nature's Red List of Threatened Species (IUCN Red List) categories.

By applying classification and regression trees (CART), we highlight the importance of environmental- and hydrological change on the freshwater biodiversity status based on IUCN Red List assessments on each grid cell globally. Our results reveal a large-scale spatial classification of the environmental variables and their potential impact on the ongoing freshwater biodiversity crisis.

How to cite: Kiesel, J., Vu, T., Kakouei, K., Sami, D., He, F., Guse, B., Fohrer, N., and Jähnig, S.: Disentangling the impact of global change on freshwater biodiversity decline, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18962, https://doi.org/10.5194/egusphere-egu2020-18962, 2020.

Climate variability, drought, and deforestation are increasing in the Horn of Africa (HOA). Evaluating land use/land cover (LULC) changes and their impacts on water availability and variation are vital actions for regional land-use planning and water resources management. LULC changes during 2000-2015 were estimated using high resolution Landsat images and Google Earth Engine cloud platform, and land-use dynamics index (K). The impact of LULC change on water yield was evaluated using the InVEST model. The results at regional scale show that there were rapid decreases in the area of forests and barren lands (-K) while there was a drastic increase in built-up area (+K values). The transition was found to decrease from forested land to low biomass with highest and lowest values of 51.13% and 16.7%, respectively. There were similar LULC changes in the Mereb-Gash river basin. The total annual water yield increased for all the catchments during 2000-2015, and reached the peak in 2010. The highest annual water yield decreased in the forested lands from 43.18 million m³ in 2000 to 4.1 million m³ in 2015. There was a strong positive correlation between areal changes (%) and the annual water yield variations (%) in all the LULC types except for the water body, and the correlation was significantly positive for the forested areas (p<0.01). The study demonstrates that the decrease in forested areas and expansion in the built-up areas had large impact on water yield. The impacts may further increase pressure on the ecosystem services, exacerbate water scarcity, and food insecurity unless basic measures are planned and implemented.

Key words: LULC; climate variability; InVEST; annual water yield; K-index

How to cite: Measho, S., Chen, B., Pellikka, P., Guo, L., and Zhang, H.: Land use/Land cover Changes and Associated Impacts on Water Yield Availability and Variation, Mereb-Gash River Basin in Horn of Africa , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1479, https://doi.org/10.5194/egusphere-egu2020-1479, 2020.

The toxicity and persistence of chromium in soils challenge the ecosystem and human health. Various remediation strategies have been developed to eliminate soil Cr contamination, and the most popular one is chemical stabilization. However, chemical stabilization only changes the form of Cr and does not change the concentration of Cr, so the long-term stability of Cr has been controversial. On the other hand, some researches found that the concentration of Cr(VI) in the stabilized soil after remediation has increased. We collected Cr-contaminated soils and one-year-stabilized soils from four research sites in northern, central, and southwestern China, trying to understand the difference of Cr species and structure in soils with various soil properties. Results showed despite the different clay content and mineral composition, all contaminated and stabilized soils are alkaline (pH 7.36 ~ 10.5). In addition, there are differences in the pollution levels of Cr and Cr (VI) in soils. In northern China, Cr(VI) was the main state of Cr-contaminated soils; however, Cr is mainly present in Cr-contaminated soil in the form of Cr(III) in southern China. For chemical stabilized soils, Cr concentrations remained similar to Cr-contaminated soils (1500~9000 mg/kg), but the concentration of Cr(VI) (5~55 mg/kg) was reduced through commercial remediation materials. The speciation of Cr in Cr-contaminated soils transformed from exchangeable Cr and Cr bound to carbonates into Cr bound to Fe-oxides and residuals in stabilized soils. SEM-EDS, XAFS and μ-XRF results revealed the main forms and structure of Cr, and showed Cr unevenly distributed on the surface or edge of the mineral. The acid leaching test revealed that Cr(VI) could be released from Cr-contaminated soils by acid, and soils can release Cr(VI) under different acidity conditions. Cr(VI) from soils collected from northern and southern China was released from acidity of [H⁺]=0.1M and [H⁺]=0.5M, respectively. This was due to erosion of coating minerals or Cr(VI)-bearing minerals. Our study suggested that stabilization technology not only reduces the toxicity of chromium, improves the stability of chromium, but also partially recovers the physical and chemical properties of soil. Meanwhile, in future remediation projects, it is necessary to consider the existing forms of chromium in different soils to develop remediation strategies.

How to cite: Li, D., Li, G., and Zhang, D.: The key forms of Chromium influencing the long-term stability of Cr in Cr-contaminated soils and chemical stabilized soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4007, https://doi.org/10.5194/egusphere-egu2020-4007, 2020.

Ecological restoration (ER) has strong consequences on hydrological responses. The China’s Loess Plateau (LP) contributed nearly 90% of sediment load in the Yellow River, which was once the world’s largest carrier of fluvial sediment. ER efforts including the soil and water conservation measures (SWCMs, especially terracing and construction of check dams) since 1950s and large-scale ecological restoration campaigns such as Grain-for-Green project (i.e., returning sloping cropland to afforestation and pasture reestablishment) in 1999, has resulted in extensive land use/cover change, leading to considerable decreases of streamflow (Q), suspended sediment yield (SSY) and sediment concentration (C) in the LP over the past 60 years. However, it remains challenging to quantify the impacts of ER and climate variability on declines of Q and especially SSY. In this study, we formulate the notion of elasticity of sediment discharge, by associating SSY change to climate variability and ER over the period 1950s to 2014. Our results strongly support the hypothesis that changes to both streamflow volumes and to the suspended sediment concentration versus water discharge (C-Q) relationships result in reduced SSY, so that streamflow is reduced but runs clearer. We find that two of the ER strategies resulted in weaker relative impacts of climate variability, largely by reducing streamflow (by 55% to 75%). Meanwhile, ER predominantly decreased SSY (by 63% to 81%). Regarding ER practices, (i) the predominant measure acting to reduce SSY changed, over time, from engineering to reforestation; (ii) check-dams preferentially act to regulate the C-Q relationships whereas reforestation preferentially acts to moderate streamflow. Overall, our results suggest that a combination of engineering and vegetation measures is critical to achieving high-efficiency ER. While change to the ER strategy increased the efficiency of streamflow for SSY control, the lost water discharge per unit SSY reduction increased from 5.2 to 6.4 m³·t^-1. Conflicting demands for water necessitate that further ER should target precision management by revegetation of targeted areas in the Loess Plateau.

How to cite: Gao, G.: Formulating an elasticity approach to quantify the effects of ecological restoration and climate variability on streamflow and sediment discharge changes in the Loess Plateau of China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4482, https://doi.org/10.5194/egusphere-egu2020-4482, 2020.

Forests and artificial forest lines at the climax stage are the source of greenhouse gases. Artificial forests, forest lines, recreational forest plantations can help to reduce the greenhouse emission, increase oxygen production, enlarge the soil carbon biological capacity, and improve silviculture land protective and recreational function. 

Artificial forest systems on the Chernozem and Kastanozem have the obvious signs of the climatic suppression. The adverse influence of climate on artificial forests via summer droughts is aggravated by poor soil conditions for silviculture. The lifespan of artificial forests reduces from typical for most tree species of 200-800 years to short 30-60 years. In dry steppe, the habitus and dimensions of trees are worse in comparison to natural analogue in good conditions of development. Now the artificial forests in semiarid and arid areas do not suit the task of carbon sequestration, oxygen producing and climate correction. It aggravates the current uncertainty of biosphere. Standard outdated agronomy and soil reclamation technologies fail to prepare the soil for the long-term successful forest growth. The known silviculture technology fails to provide the forest soil watering, because standard irrigation is linked to enormous water consumption, soil and landscape degradation.

We propose the Biogeosystem Technique (BGT*) for the semiarid and arid forestry improvement. The BGT* is a transcendental (non-imitating natural processes) approach to improve soil management including pre-planting soil processing, soil watering and fertigation (chemisation) for proper long-term artificial forestry. The BGT* provide regulation of the fluxes of energy, matter (including organic carbon), water and higher biological productivity of artificial forestry: intra-soil machining provides productive fine aggregate system of the 20-50 cm soil layer for root development; waste intra-soil dispersed recycling while intra-soil machining of the 20-50 cm soil layer provides better soil reclamation, remediation, plant nutrition, macro- and micro elements (including heavy metals), matter organic matter  transfer and turnover in the soil continuum; intra-soil pulse continuous-discrete plant watering reduces the transpiration rate, water consumption of trees is less for 5-20 times, and at the same time provides increased biological productivity of forest plantation, reversible biological sequestration of carbon. The BGT* methods reduce the loss of organic matter from soil into vadoze zone and atmosphere; reduce greenhouse emission from soil and forest, and improve the agro-ecological environment. Apply of the BGT* methods to the dry steppe Chernozem and Kastanozem artificial forest systems will increase the artificial forests oxygen and biomas production, prolong forest lifespan, improve the silviculture land protection function, and mitigate climate change.

BGT* robotic systems will be of low energy and material consumption, will improve forestry, agriculture, reduce the biosphere and climate uncertainty, insure the recreational appearance of forest, make the life attractive.

Objectives of the study: to show the long-term results of Russian steppe terrain silviculture system on Chernozem and Kastanozem; using BGT* methodology, to justify intra-soil 20-50 cm milling, waste intra-soil dispersed recycling while intra-soil 20-50 cm machining, intra-soil pulse continuous-discrete plant watering to provide higher artificial forest biological productivity, reversible carbon biological sequestration, soil fertility, the human and soil health.

How to cite: Kalinichenko, V., Glinushkin, A., Mukovoz, P., Batukaev, A., Minkina, T., Sushkova, S., Mandzieva, S., Zinchenko, V., Iljina, L., Larin, G., and Bauer, T.: Biogeosystem Technique as a methodology for overcoming the outdated theory and management principles of semiarid silviculture, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8021, https://doi.org/10.5194/egusphere-egu2020-8021, 2020.

The knowledge of spatial heterogeneity and environmental controllers of soil organic carbon (SOC) stocks is essential for upscaling and predicting SOC dynamics under changing land use and climatic conditions.  This study investigated the spatial variability and intrinsic and extrinsic controllers of SOC stocks in a boreal forest catchment (320 ha) at the International Institute for Sustainable Development Experimental Lakes Area in Ontario, Canada. Forty-seven surface soil (0-30 cm) samples, representative of the spatial variability of topography, surface water flow patterns and vegetation distribution, were obtained within the catchment. Air dried soil samples were sieved to separate gravel (>2 mm) and fine-earth (<2 mm) fractions and were analyzed for SOC concentration using the loss-on-ignition method. Core sample method was used to determine the soil bulk density. SOC concentrations in surface soils showed a large spatial variability (1.2% to 50.4%, CV= 111.3%). Thick organic soil layers in the wetlands of the sub-catchment showed the highest SOC concentrations. The surface soil SOC stocks ranged between 14.5 to 240.5 Mg ha-1 with an average stock of 101.5 Mg ha-1. Spatial autocorrelations of SOC stocks were modelled by calculating relevant variograms. The variability of SOC stocks (sill = 834) was dominated by the random variability (nugget=275) whereas the variability of SOC concentration (sill = 2.5) was dominated by the spatially structured variability (nugget = 0). We found a strong spatial autocorrelation of the SOC concentrations within the catchment, but the SOC stocks were less spatially correlated. This was largely due to the heterogeneity in the thickness of the surface soil layer (10 cm - 30 cm) and in the gravel content (0-28.9%). We found that a large over-estimation of SOC stocks (52.5%) could result if these intrinsic factors are not considered. Extrinsic controllers were generally not significantly related to the SOC stock; Spearman’s rank correlation analysis on the entire dataset showed non-significant relationships between the SOC stock and extrinsic controllers, namely NDVI (r = 0.04) elevation (r = 0.2), slope (r = -0.1) and topographic indices, stream power index (r = -0.1), relative position index (r=-0.2) and plan curvature (r = -0.1). However, regression tree analysis revealed local-scale effects of aspect, NDVI, elevation, and distance to ridge on the SOC stocks. Many forest soil databases lack information of gravel content and soil depth. Thus, upscaling boreal forest SOC stocks without these two key intrinsic controllers can lead to higher uncertainties in  SOC stock estimates. Further, the impacts of extrinsic controllers may vary across heterogenous landscapes. Machine learning-based digital soil mapping techniques such as Random Forest models are more appropriate for incorporating local-scale impacts of extrinsic controllers when upscaling SOC stocks of boreal forest soils. 

How to cite: Vitharana, U., Casson, N., Kumaragamage, D., Gunn, G., Higgins, S., and Mishra, U.: Spatial heterogeneity and environmental controllers of soil organic carbon stocks in a boreal forest, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9359, https://doi.org/10.5194/egusphere-egu2020-9359, 2020.

Introduction. Natural reforestation is the widespread trend in the modern land-use changes in the southern taiga zone at the European territory of Russia after 1990s. Its total area is more than 10 million ha. At the same time forest natural regeneration is mutual usual process in the long-term land-use changes in this part of Russia with complex history of its development during millennium. It plays crucial role in soil successions, their fertility and environmental function dynamics including bio productivity support and carbon sequestration, which is given special attention against the background of global climate change challenges in the twenty-first century. This paper presents the results of a round-the-year monitoring of soil CO₂ emission in comparable sites of the fallow lands chrono sequences in conditions of a representative area of the Central Forest Reserve with background wood-sorrel spruce forests which are typical for the southern taiga zone of Central Russia.

Objects and methods. The dominant soil type is sandy-loam Albeluvisols (by WRB, or Orthopodzolic soil by Russia Taxonomy, or Alfisols by Soil Taxonomy, or Podzoluvisols by FAO). The studies have been done in the representative 5 sites at different age of natural reforestation: (1) Fallow meadow grassland – “0-moment”; (2) Forest-fallow birch domination stage of 10-15 year; (3) Birch domination stage of 20-30 year with young spruce participation; (4) Birch-forest stage of 50-60 year with spruce participation; (5) Spruce-forest after fallow stage of more than 100 year with birch participation. CO₂ fluxes seasonal and diurnal dynamics measuring were carried out in situ using a mobile gas analyzer Li-820 and soil exposure chambers with parallel measurements of air temperature, soil temperature and moisture. Also, biomass, soil organic carbon and bulk density were analyzed in their topsoil and subsoil horizons with C stock calculation.

Results and discussion. Analysis of the successional dynamics of the topsoil organic carbon stock showed the maximum rate of their increasing in the first stages of natural reforestation by a thick undergrowth of birch (more than 30 g m^-2∙year^-1) that agrees well with the maximum intensity of the woody biomass growth in case of dominant birch forest up to 50-60 years (more than 100 g m^-2∙year^-1). Research revealed the maximum intensity of soil CO₂ emission (up to 11-12 g C-CO₂ m^-2∙day^-1) in the meadow fallow land and its gradual decreasing in process of reforestation down to values close to background ecosystems in 4-5 g C-CO₂ m^-2∙day^-1 in the last investigated succession study with wood-sorrel spruce older than 100 years, which is in good correlation with the gradual humus accumulation in topsoil due to reduced mineralization of organic compounds from dying vegetation. The seasonal and daily dynamics of soil CO₂ emissions are determined by soil temperature (K_TS 0.77 - 0.99), air temperature (K_TA 0.42 - 0.99), and soil moisture in spring and fall (K_WS -0.55 - -0.98).

Conclusions. Investigation of forest natural regeneration impacts on the level of soil organic carbon accumulation and CO₂ fluxes in the representative southern taiga ecosystems is important element of their soil environmental monitoring and management.

How to cite: Vasenev, I., Komarova, T., and Melese, S.: Natural reforestation effect on soil organic carbon and СО2 flux dynamics in southern taiga ecosystems with Albeluvisols, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13507, https://doi.org/10.5194/egusphere-egu2020-13507, 2020.

Soil and groundwater salinization due to seawater intrusion is among the most important problems in coastal farmlands. Inverse estimation of unsaturated soil hydraulic and solute transport properties represents a fundamental step to understand saltwater intrusion dynamics. A three-year study was conducted in a maize field bounding the southern Venice Lagoon. Volumetric water content θ, soil matric potential ψ, and apparent electrical conductivity (ECa) were monitored hourly by five automatic monitoring stations at four depths (0.1, 0.3, 0.5 and 0.7 m). Groundwater electrical conductivity (EC) and depth to the water table were measured in five wells. In addition, soil water and groundwater samples were collected and analyzed to determine the chemical composition. Soil hydraulic parameters for the van Genuchten-Mualen equations were determined using the inverse method in Hydrus-1D. The water flow was modelled based on the daily averages of θ at the four depths and the θ values measured in the lab at selected ψ on undisturbed soil cores extracted from the five monitoring stations. Precipitation, crop transpiration, soil evaporation and depth to the water table were used as time-variable boundary conditions. Root water uptake was estimated by using Feddes model. Finally, the major ion chemistry module of HYDRUS-1D was used to model solute transport and root water uptake reduction due to osmotic stress. The use of HYDRUS-1D to understand saltwater dynamics would enable the developing of mitigation strategies to limit its detrimental effect on farmland productivity and groundwater quality.

How to cite: Finco, G., Zancanaro, E., Teatini, P., and Morari, F.: Seawater intrusion dynamic at the Casetta farmland (Venice). Characterization using HYDRUS-1D, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13844, https://doi.org/10.5194/egusphere-egu2020-13844, 2020.

One of the main consequences of digging works for the Grand Paris Express (GPE) project will be the excavation of a huge amount of earths, representing a 20% increase of the total wastes produced in the area over ten years. These earths are known to be naturally contaminated in Trace Elements (TE) such as Molybdenum (Mo) or Selenium (Se). Even though only small levels of TE are involved, earths leaching behavior often prevent public works companies from storing them in Inert Wastes Landfill. Indeed, results obtained according to the standardized leaching test NF EN 12457-2 with a liquid/solid ratio of 10 L.kg^-1 are likely to overpass acceptation criteria fixed by European regulations (Council Decision 2003/33/EC).

To avoid extra charges linked with earth’s evacuation, a chemical stabilization process may be efficient and industrially applicable (Geng et al., 2013 ; Manning and Burau, 1995), even for TE like Mo and Se known to be highly mobile in alkaline matrices such as GPE excavated earths (Rashid et al., 2002). However, the current French regulation does not allow stabilized materials to be considered as inert wastes, mainly because of the lack of guarantee on the long-term efficiency of such treatments (Coussy et al, 2014).

We present here the long-term impact of minerals amendments (3%wt maximum) on the leaching behavior of a calcareous sample coming from a GPE construction site. Standardized leaching tests (NF EN 12457-2) have been carried out before, after stabilization, and after specific ageing experiments. Leachate concentrations have also been followed during ageing experiments carried out on raw and stabilized samples. The ageing protocol was based on soxhlet extraction principle (Benzaazoua et al., 2004) consisting in multiplying humectation/desiccation cycles at approximatively 70°C for 10 days in a closed environment. Standardized leaching tests have shown that Mo and Se concentrations sharply decrease after stabilization in every case, showing concentrations below Inert Wastes landfill criteria (0.1 ppm and 0.5 ppm for Se and Mo respectively). On the other hand, variable impacts of ageing have been observed depending on the TE considered. For Mo, the best results have been obtained with a zero-valent iron amendment, leading to the retention of almost 90% of the total Mo in a calcareous sample after ageing. For Se, all scenarii studied have permitted a retention of at least 90% of total Se or more. The promising results presented here will have to be confirm by attesting the nature of bonding between stabilizing agent and TE.

How to cite: Brandely, M., Coussy, S., Blanc-Biscarat, D., Gourdon, R., and Le Borgne, T.: Impact of ageing on the leaching behavior of a calcareous sample excavated from Grand Paris Express construction sites and naturally contaminated in Molybdenum and Selenium, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17973, https://doi.org/10.5194/egusphere-egu2020-17973, 2020.

Forests face considerable pressure from climate change, while demand of provided ecosystem services is high. Managing and planting forests need well informed decisions by practitioners, to fulfill the goal of sustainability. In Germany, informed decisions are derived from forest site evaluation maps, integrating biogeoecolocigal conditions (climate, soil water, nutrients). Here, we focus on mapping of nutrients in the federal state Hesse, Germany. For Hesse, a forest site map exists, which indicates a soil nutrient regime (SNR) index (classes very poor, poor, medium, rich, very rich). Site mapping was done in the field by experts, considering ground vegetation and soil morphology. Guidelines exist for choosing management options (i.e. suitable species composition, harvest restrictions, etc.), but if spatial information is not accurate, management decisions will be misguided.

Three major challenges regarding the currently available site information exist: (1) the spatial proportion of “medium” sites is exceptionally high (65% of mapped forest area) and while there is differentiation between parent materials, topography is neglected. (2) Whereas 80% of Hesse’s forests were mapped, there is need to fill the gaps. (3) The existing SNR index does not take analytical measurements of soil nutrients into account. Objectives were (1) to refine and expand the existing map of SNR by (2) including soil chemical properties from the second National Forest Soil Inventory (NFSI), (3) which have to be regionalised beforehand.

Stocks of Ca, Mg and K, base saturation, effective cation exchange capacity (90cm depth and organic layer), and C/N ratio (organic layer or 0-5 cm) of 380 profiles from the NFSI were chosen to characterise the SNR. Regionalisation was performed with generalised additive models (GAM) by using environmental relationships of the target variables with variables of climate, vegetation, parent material and soil properties (soil map 1:50,000). Ten-fold cross validation revealed R² values from 0.54 to 0.79, with low relative root mean square deviation (5 to 17%) and slopes not significantly different from 1. From the six successfully modelled target variables, we inferred a single SNR for each soil map polygon. This was challenging, because variables provided contrasting information regarding the SNR. We addressed this by using the Soil Inference Engine (SIE), which bases on fuzzy logic. Each variable received an optimality value for each SNR class. Using an expert-driven weighting system a SNR membership was inferred, whereas highest membership defined the SNR class. The result was highly sensitive towards parent material and topography. For instance, acidic parent material had lower SNR classes compared to base rich parent material. Within a given parent material, ridges where judged less nutrient rich compared to planes and topographic positions, where material is accumulated.

The results provide a much more differentiated and complete map for SNR, which mirror actual expectations of nutrient distribution across Hesse’s landscape units. The approach is transparent and inter-subjectively reproducible. The new map will be used to guide reforestation activities in Hesse after the severe forest disturbances by recent climatic extremes (e.g. drought, storms) and the approach can be transferred to other regions.

How to cite: Heitkamp, F., Ahrends, B., Evers, J., and Meesenburg, H.: A soil nutrient regime index for forest practitioner decisions in Hesse, Germany: spatial explicit modelling of soil chemistry and integration by fuzzy-logic, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21641, https://doi.org/10.5194/egusphere-egu2020-21641, 2020.

Land degradation – the reduction or loss of the productive potential of land – is a global challenge. More than 20% of the Earth’s vegetated surface is estimated to be degraded, affecting over 1.3 billion people, with an economic impact of up to US$10.6 trillion. Land degradation reduces agricultural productivity and increases the vulnerability of those areas already at risk of impacts from climate variability and change. Addressing land degradation, Sustainable Development Goal (SDG) target 15.3, is essential to improve the livelihoods of those most affected, and to build resilience to safeguard against the most extreme effects of climate change. Drivers of land degradation include natural processes and human activities, and understanding such drivers is key for deploying effective interventions for addressing it. The parties to the United Nations Convention to Combat Desertification (UNCCD) have adopted a framework for assessing and monitoring land degradation at national scale, by measuring three sub-indicators: Changes in land cover, changes in soil organic carbon, and changes in primary productivity. In this study, we use the framework developed by the UNCCD and Trends.Earth, the most widely tool used for producing such indicators, to assess land condition globally for the period 2001-2015, the SDG 15.3.1 baseline period. Using a Bayesian hierarchical model, we then assessed the contribution of 12 drivers of land degradation, including key biophysical and anthropogenic variables, to the observed patterns to provide insight into the main drivers of land degradation at global, regional, and national scales. These results are critical for designing locally relevant plans for assessing land degradation contributing to the global goal of achieving a land degradation neutral world by 2030. The results of this analysis allow identification of not only the significant drivers in a given region, but also of those areas where unexpected trends (either improvement or degradation) are indicative of potential policy successes or failures.

How to cite: Zvoleff, A., Noon, M., Daldegan, G., and Gonzalez-Roglich, M.: Forging the path to achieving land degradation neutrality: Global patterns and drivers of land degradation at global scales, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11497, https://doi.org/10.5194/egusphere-egu2020-11497, 2020.