Description: Large-scale application of biochar has been promoted as a strategy for improving soil quality in agricultural and contaminated lands, as biochar has the potential to alter the soil physical and biogeochemical properties. Biochar at different concentrations has been shown to have inconsistent effects on soil hydrological properties, yet the cause of the inconsistency is not well understood. To investigate the relative roles of biochar size and concentration, we mixed pure sand with a commercially available biochar varying its concentrations and particle sizes and measured saturated (K sat ) and unsaturated hydraulic conductivity, and water retention characteristics. An increase in the concentration of fine biochar (〈 2 mm) consistently decreased K sat and increased saturated moisture content. In contrast, an increase in the concentration of unsieved (mixture of coarse and fine) biochar up to 5% (by volume) increased K sat , whereas any further increases in unsieved biochar concentration decreased K sat . Increase in biochar concentration, irrespective of their particle size, consistently decreased the unsaturated hydraulic conductivity. Measuring the changes in the characteristics of water retention curves of biochar-sand mixture with biochar particle size, we showed that added biochar can either decrease (clog) or increase pore spaces in the mixture based on the quantity of fine biochar fraction, which in turn could decrease or increase the hydraulic conductivity of the mixture. Thus, biochar concentration and particle size must be taken into consideration to maximize the intended hydrological benefits of biochar amendment.

Description: Large-scale open cut mining has occurred within the Bowen Basin for over four decades, transitioning from shallow mining depths and limited spoil elevation to increased mining depths, pre-stripping and increasingly elevated mesa-like landforms. As a result of this evolution, the stabilization of modern constructed landforms is no longer assured through the establishment of vegetation alone. The selection of resilient fragmental spoil types for the construction of final landform surfaces, and as cladding for stabilizing steep erosive batters, is a practical methodology that has the potential to significantly improve rehabilitation outcomes, by increasing surface rock cover, roughness and infiltration and reducing erodibility. An understanding of the properties and behavior of individual spoil materials disturbed during mining is required. Relevant information from published literature on the geological origins, lithology and weathering characteristics of individual strata within the Bowen Basin Coal Measures (and younger overlying weathered strata) has been reviewed, related to natural landforms and applied to the surface stability of major strata types when disturbed by mining. A spoil classification derived from geological characteristics and weathering behavior of identifiable lithologic components has been reviewed and refined, demonstrating the application of use of geological information. This classification system is a tool for the allocation of spoil types and use of categories which have application in pre-mine feasibility investigations, landform design and material selection and placement. The logic of classifying materials based on their stability in the natural landscape has wider relevance to other mining areas where elevated landforms of sedimentary material are constructed.

Description: Riverine biological communities are highly resilient to extreme flood and/or drying disturbance regimes that would otherwise be destructive because these organisms can recolonise from upstream, floodplain or hyporheic refugia when suitable conditions return. Healthy rivers require a high degree of connectivity to support complex life cycles of many lotic organisms and associated ecosystem functioning. Similarly, connectivity is required for appropriate geophysical functioning; permitting flux of water and sediment that drives channel-forming and ecological processes. Ecological and geophysical processes have operated in this temporal and spatial patchwork of disturbance and recovery pre-Anthropocene. Human impacts are increasing constraints on river and floodplain connectivity, severing many natural pathways, and degrading river ecosystem functioning. River restoration seeks to re-establish some of those biological and physical connections to enhance some level of system health. However, increasing sediment connectivity may be detrimental to river health in some instances. Strongly connected catchments can transmit excessive quantities of sediment from inappropriate land management, detrimental invasive species can spread more widely, and many ecosystem processes can exceed positive feedback control. Simply restoring connectivity will not necessarily lead to healthy river ecosystems. River management requires a greater understanding of how and when connectivity can and should be restored. While current thinking is often that greater connectivity is better, we illustrate with examples from New Zealand rivers that this is not always the case. The benefits and costs of maintaining or restoring river connectivity need to be given as much attention as the restoration and maintenance of river systems per se.

Description: Soil erosion is a major problem worldwide, affecting natural, agricultural and urban environments through its impact on flood risk, water quality, loss of topsoil, eutrophication of water bodies, sedimentation of waterways and damage to infrastructure such as roads, buildings and utility supply networks. Thus there is a need to identify risks to infrastructure associated with erosion and interventions needed to reduce those risks. Further, inclusive ways of communicating about mitigation strategies with stakeholders such as farmers, land managers and policy-makers are essential if interventions are to be implemented. Applying the Decision-Support Matrix approach, which combines hydrologic and geomorphic principles with Participatory Action Research, a tool for Communicating and Visualising Erosion-associated Risks to Infrastructure (CAVERTI) was developed in collaboration with a variety of stakeholders including farmers, private landowners, asset owners and environmental organisations, focusing on a case-study area in northern England. The CAVERTI tool synthesises process understanding gained from modelling with knowledge and experience of stakeholders to address the sediment transport problem. Tool development was collaborative, ensuring that the problems and solutions presented are easily recognised by practitioners and decision-makers. The tool helps to assess, manage and improve understanding of risk from a multi-stakeholder perspective and presents mitigation options. We argue that visualisation and communication tools co-developed by researchers and stakeholders are the best means of influencing decision-makers to invest in mitigation. The CAVERTI tool is designed to encourage farmers, land and asset owners to act to reduce erosion, providing multiple benefits from protecting local infrastructure to reducing pollution of waterways.

Description: Long-term cultivation of steppe soils in a non-sustainable way caused severe soil degradation and reduced agricultural productivity in Eastern Europe, one of the world´s most important areas for cereal production. In order to combat soil erosion and maintain yields, a widespread system of tree windbreaks was introduced in the 1950s, accompanied by improved agricultural practices in recent years. However, information on the effectiveness of such measures to rebuild soil organic carbon (SOC) is scarce. The objective of this study was to estimate the OC storage potential of the fine mineral fraction of degraded arable steppe soils in Moldova and to quantify SOC sequestration rates under (1) windbreaks, (2) cropland with improved crop rotation/manure application, (3) cropland with cover cropping. Natural grassland relicts served as a reference to estimate the SOC saturation potential. Our results revealed a low SOC saturation of 50% under conventional agricultural use due to high SOC losses, indicating a high potential for SOC sequestration. Relatively high SOC sequestration rates were determined for topsoils (0-30 cm) under windbreaks (0.9 t ha -1 yr -1 ), improved crop rotation/manure application (1.3 t ha -1 yr -1 ) and cover cropping (1.9 t ha -1 yr -1 ). In this regard, sequestration rates derived from OC changes of the fine fraction may be more reliable than total SOC-based rates, particularly for windbreaks with high proportions of labile SOC. We conclude that implementation of improved agricultural management together with the maintenance of windbreaks is a promising strategy to rebuild SOC, reduce widespread soil erosion and compaction and secure Moldova´s agricultural productivity.

Description: Tillage soil erosion is seen as a great problem in the Mediterranean region and is worsened by the climatic conditions. Previous studies have shown a decrease in biodiversity in arable lands across Europe. Weeds are a major component of biodiversity within agro-ecosystems, but few studies have aimed to associate weed species with soil tillage intensity. We performed an analysis to test the potential short-term effects of different tillage systems on weed species under our study conditions. The emerged weed data were measured, comparing a conventional tillage system with conservational tillage systems (minimum tillage and no tillage) in two cropping systems (monoculture wheat and a rotation scheme of barley-legume-wheat-fallow). Compared to the tilled soil, higher weed density and weed species richness were observed in the conservation tillage plots. The weed density and weed species richness in the monoculture system were higher compared to those in the crop rotation system. We used classification and regression trees to analyze the relationship between the soil tillage systems and the weed community, taking into account the climatic conditions. The results indicate that different soil tillage systems produced tree models: Silene vulgaris (L.) was associated with the MT system and high and irregularly distributed rainfall; Hypecoum imberbe Sm. and Hypecoum procumbens (L.) were linked to MT plots with low and well-distributed precipitation rates; and Cardaria draba (L.) was present all years independently of climatic conditions but was never found in the NT system, so its presence could be regarded as an indicator of tillage intensity.

Description: Biochar promotes the storage of organic carbon (OC) in soils. Organic carbon is unevenly distributed in soils among different particle-size fractions showing different structures, functions, and stability. The objective of this study was to investigate the biochar-soil interactions and the redistribution of soil C in different soil fractions based on a two-year field experiment. Fractionation was done by particle-sizes including coarse sand (250-2000 μm), fine sand (53-250 μm), and silt/clay (〈53 μm). Integrated spectroscopic techniques were employed to examine physical characteristics of biochar soil interactions in different soil fractions. Application of biochar increased OC by 37, 42, and 76% in soil particle-size fractions of 53-250, 〈53, and 250-2000 μm, respectively. This was supported by X-ray fluorescence spectroscopy (XRF) analysis which showed an increase of C contents by 5-56% with biochar addition. The highest increment in OC was found in coarse sand fraction and redistribution of OC was detected depending on various soil particle-sizes. Results of scanning electron microscopy combined with electron dispersive X-ray spectroscopy (SEM-EDX) analysis showed the interactions between soil and biochar, which could be attributed to oxidized functional groups (O-C=O, C=O, and C-O) captured by the X-ray photoelectron spectroscopy (XPS). The long-term aged biochar could be beneficial to enhance soil quality by promoting OC storage and facilitating positive biochar-soil interactions.

Description: Over the last two decades, geospatial technologies such as Geographic Information System (GIS) and spatial interpolation methods have facilitated the development of increasingly accurate spatially explicit assessments of soil erosion. Despite these advances, current modelling approaches rest on: a) an insufficient definition of the proportion of arable land that is exploited for crop production, and b) a neglect of the intra-annual variability of soil cover conditions in arable land. To overcome these inaccuracies, this study introduces a novel spatio-temporal approach to compute an enhanced cover-management factor (C) for RUSLE-based models. It combines highly accurate agricultural parcel information contained in the Land Parcel Identification System (LPIS) with an object-oriented Landsat imagery classification technique to assess spatial conditions and inter-annual variability of soil cover conditions at field-scale. With its strong link to LPIS and Earth observation satellite data, the approach documents an unprecedented representation of farming operations. This opens the door for the transition from the currently used potential soil erosion risk assessments towards the assessment of the actual soil erosion risk. Testing this method in a medium size catchment located in the Swiss Plateau (Upper Enziwigger River Catchment), this study lays an important foundation for the application of the very same methods for large-scale or even pan-European applications. Soil loss rates modelled in this study were compared to the insights gained from emerging techniques to differentiate sediment source contribution through compound-specific isotope analysis (CSIA) on river sediments. The presented technique is adaptable beyond RUSLE-type soil erosion models.

Description: In the Ethiopian Highlands, stone bunds are a common practice for soil and water conservation, influencing runoff and erosion processes from sloped agricultural areas. The objective of this study was to investigate how stone bunds affect spatio-temporal relationships of these processes to better understand their impacts on soil water development at the smallholder farmer's field level. Study area was the Gumara-Maksegnit Watershed in Northern Ethiopia, where two representative transects were investigated: One transect crossed a 71 m long field intersected by two stone bunds (SB) traced along the contour. The second transect crossed a similar hillslope without conservation structures at a length of 55 m representing baseline (untreated) conditions (NSB). During the rainy season 2012, bulk density, volumetric water content were monitored as well as tension disc infiltrometer experiments were performed to determine the saturated hydraulic conductivity and to derive soil water retention characteristics. Our observations show that SB decreased significantly soil bulk density in center and lower zones of SB transect compared to NSB. No temporal change was observed. Results targeting the surface soil moisture indicate that infiltration was higher with SB and happened earlier in the rainy season in the zones around the SB. Saturated hydraulic conductivity was positively affected by SB and increased significantly. Improved soil hydrology by SB fields may increase crop yields by higher soil water contents but also by extending the growing season after the rainy season. Therefore, stone bunds are a successful measure to establish climate-resilient agriculture in the Ethiopian highlands.

Description: Establishment of an appropriate vegetation system for reclamation of saline-sodic soils requires specific studies for specific salt-affected region(s). The phytoremediation of saline-sodic soils has not been well documented in the Songnen Plain of northeast China. Thus, in this study we aimed to investigate the effects of grass (G) and maize ( Zea mays L.) (M) vegetation systems, which were established for 5 years, on soil properties of ten typical saline-sodic sampling sites across the Songnen Plain, in comparison with respective non-vegetated areas that were used as controls (CK) for the evaluation of variability among the sampling sites. Physicochemical properties, such as soil moisture, bulk density, porosity, saturated hydraulic conductivity, aggregate stability, pH, electric conductivity, total salt, organic C, total N, and C/N ratio, were analyzed. G and M vegetation significantly produced a 108% and 153% improvement in soil quality, respectively. Additionally, metagenomic analysis of the soil bacterial community revealed that vegetation enhanced the ability of the bacteria to survive in saline-sodic soils, relative to the control. The composition of the bacterial community was highly correlated with all of the soil physicochemical properties. G vegetation had better effects than M vegetation in enhancing soil organic C, total N and aggregate stability, whereas M planting more favorably adjusted soil pH, physical structure and bacterial community than G vegetation did. Collectively, these findings demonstrate that M vegetation has a greater impact than G vegetation on repairing saline-sodic soils in the Songnen Plain of northeast China.