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PurposeSoil and water erosion from high rock fragment content disturbed soil accumulation severely threatens ecological security. Evaluation of the quantitative influence of rock fragment content on soil erosion processes was the basic research for soil and water conservation.Materials and methodsField simulation scouring experiments were conducted on the disturbed soil accumulation experimental plot. A 10 × 1-m2 plot with 28 gradients was established on Changwu Experimental Station in the Loess Plateau, China. Tap water was applied at the top of the plot with the four different flow discharge rates of 1.3 × 10−4, 1.7 × 10−4, 2.1 × 10−4 and 2.5 × 10−4 m3 s−1 to simulate surface runoff processes. The experimental plots underlying surfaces were filled with different rock fragment content of 20%, 40% and 0%. The soil used in these experimental plots was a silty loam from the disturbed soil accumulation formed by expressway construction in the loess plateau areas. The disturbed soil accumulation site was located near the G70 Fujian–Yinchuan expressway and the vegetation cover was very low. The mean diameter of rock fragments was 22 mm in these experiments, and the rock fragments were unsmooth, angular crushed stone taken from the quarry in the Changwu County.Results and discussionThe results showed that rock fragment content of 20% and 40% could significantly decreased runoff and sediment (P < 0.05), although there was no significantly different between 20 and 40%. The rock fragments decreased mean flow velocity by 43 to 55% in mean flow velocity compared to the pure soil. Furthermore, the flow was laminar flow in the rock fragments slope. The rock fragments significantly decreased flow shear stress (52–89%), stream power (63–89%), unit stream power (41–59%), runoff kinetic energy (67–88%) and unit energy of the water-carrying section (81–89%) compared with the pure soil. With increased rock fragment content, the rill erodibility decreased. The rill erodibility was estimated to be 1.4 × 10−3 s m−1, 0.7 × 10−3 s m−1 and 0.5 × 10−3 s m−1, under the condition of pure soil, rock fragment content of 20% and 40%, respectively.ConclusionsLow rock fragment content (< 40%) in disturbed soil accumulation significantly decreased runoff and sediment. With the rock fragment content increased, the rill erodibility was decreased. Appropriate rock fragment content could be used to control soil erosion on disturbed soil accumulation in practice. The important parameters from this study will be helpful for disturbed soil accumulation erosion prediction model establishment.

PurposeIn the pile-soil interaction system, the disturbed soil directly affects the safety of the laterally loaded pile. The soil displacement field helps to evaluate the range and degree of soil disturbance. This study presents a method of visualiziing the displacement field of the soil around the laterally loaded pile by using transparent soil technology, which overcomes the measurement obstacles caused by the non-transparency of the real soil.MethodsGlass sand and transparent pore solution were mixed to make a saturated transparent soil with two particle sizes (0.1 ~ 0.5 mm and 0.5 ~ 1 mm). Instead of real soil, transparent soil was used to observe the degree of disturbance in the process of interaction with laterally loaded piles. In addition, particle image velocimetry (PIV) was used to capture the displacement of transparent soil particles. The displacement of each particle was integrated into the displacement field by a MATLAB program.ResultsWhen a horizontal force was applied on the top of the pile, the particles in front of the pile were compressed, producing observable movement within a certain area. From the displacement vector diagram, it could be seen that the displacement area of the soil surface in front of the pile increases as the layer thickness of large particle soil increases. The vertical displacement of soil in front of the pile was compacted to form a wedge-shaped area under the horizontal load. The angle between the direction of soil motion and the horizontal plane was positively correlated with the thickness of the soil layer.ConclusionTransparent soil and particle image velocimetry can help reveal the displacement trends of the soil around a laterally loaded pile. Based on this, an early warning can be provided when the displacement value and displacement angle of the soil around the laterally loaded pile exceeds the normal range.

Aims Current comprehensive meta-analysis study aims to explore how agroforestry practices influence soil quality across different climate zones. Since numerous studies proposed agroforestry as the promising agroecological farming systems over conventional monoculture systems to maintain soil quality and to regenerate disturbed soil to counteract the negative consequences of global extensive agricultural approaches. Methods By employing the comprehensive meta-analysis technique on data from 125 studies conducted in tropical, temperate, and Mediterranean environments, we quantitatively assessed the effects of agroforestry on physical, chemical, and biological soil quality indicators. Results Rates of soil erosion, the most important indication of land degradation, were improved in agroforestry systems compared to monocultures, especially in temperate (-138%) and Mediterranean soils (-40%), due to agroforestry-induced improved soil texture, aggregate stability, and soil water regulation. Soil acidification was decreased in tropical (-128%) and Mediterranean soils (-96%), but increased in temperate soils (+ 104%) due to agroforestry practices. Low temperate soil pH suggests high Ca 2+ leaching losses as evidenced by decreased Ca 2+ (-68%) and increased Fe 2+ (+ 129%) and Al 3+ (+ 235%) contents. Agroforestry systems increased organic matter accumulation in temperate (+ 86%) and Mediterranean soils (+ 65%), carbon sequestration in all climatic zones (+ 48%: 33–73%), and respiration rates in temperate (+ 119%) and tropical soils (+ 105%). Soil microbial communities, enzyme activities as well as nutrient cycling and availability were generally enhanced in agroforestry systems compared to monocultures. Conclusions Our results provide compelling evidence that agroforestry practices can contribute substantially to sustainable improvement of global soil quality.

Intensive agriculture causes land degradation and other environmental problems, such as pollution, soil erosion, fertility loss, biodiversity decline, and greenhouse gas (GHG) emissions, which exacerbate climate change. Sustainable agricultural practices, such as reduced tillage, growing cover crops, and implementing crop residue retention measures, have been proposed as cost-effective solutions that can address land degradation, food security, and climate change mitigation and adaptation by enhancing soil organic carbon (SOC) sequestration in soils and its associated co-benefits. In this regard, extensive research has demonstrated that conservation agriculture (CA) improves soil physical, chemical, and biological properties that are crucial for maintaining soil health and increasing agroecosystem resilience to global change. However, despite the research that has been undertaken to implement the three principles of CA (minimum mechanical soil disturbance, permanent soil organic cover with crop residues and/or cover crops, and crop diversification) worldwide, there are still many technical and socio-economic barriers that restrict their adoption. In this review, we gather current knowledge on the potential agronomic, environmental, and socio-economic benefits and drawbacks of implementing CA principles and present the current agro-environmental policy frameworks. Research needs are identified, and more stringent policy measures are urgently encouraged to achieve climate change mitigation targets.

While urban ecology is an expanding field of study, some natural areas within the urban environment remain under-examined. These include naturally regenerating forest communities adjacent to urban interstates. In addition, the status of interstate soils and their relationships with the community composition of forested interstate verges has received little ecological study. The purpose of this study was to examine variation in soil conditions along forested interstate corridors in Louisville, KY and to explore the extent to which soil characteristics (e.g., bulk density, pH) and heavy metals (e.g., Pb, Zn) vary with respect to three factors: interstate (e.g., traffic density), surrounding urban environment (e.g., industrial land use), and interstate construction legacies. Additionally, we explored the relationships between several edaphic factors and woody vegetation structure in these forested verges. We found that the degree and direction of the slope of land towards the interstate and the distance to the interstate pavement were strong determinants of soil characteristics and heavy metal concentrations, suggesting that the movement of de-icing salts, heavy metals, and other pollutants from the interstate was important in determining forest soil conditions along urban interstates. Since within our study area these highways did not extend into rural lands, variation in urban land uses and cover within 26 km of the city center was not large enough to explain variation in soil characteristics or heavy metals, except for a positive correlation between chromium and surrounding industrial land use. We did find that past physical soil disturbance caused by interstate construction (e.g., imported fill) left an important legacy on soil characteristics, heavy metal retention, and woody plant growth patterns in forests adjacent to urban interstates. The legacy of interstate construction on the current forest community structure (e.g., lower species richness) and the future forest (e.g., reduced tree regeneration) may further alter ecosystem productivity and ecosystem services provided by these forests and their soils.

Background The loss of carbon (C) from agricultural soils has been, in part, attributed to tillage, a common practice providing a number of benefits to farmers. The promotion of less intensive tillage practices and no tillage (NT) (the absence of mechanical soil disturbance) aims to mitigate negative impacts on soil quality and to preserve soil organic carbon (SOC). Several reviews and meta-analyses have shown both beneficial and null effects on SOC due to no tillage relative to conventional tillage, hence there is a need for a comprehensive systematic review to answer the question: what is the impact of reduced tillage intensity on SOC? Methods We systematically reviewed relevant research in boreo-temperate regions using, as a basis, evidence identified within a recently completed systematic map on the impacts of farming on SOC. We performed an update of the original searches to include studies published since the map search. We screened all evidence for relevance according to predetermined inclusion criteria. Studies were appraised and subject to data extraction. Meta-analyses were performed to investigate the impact of reducing tillage [from high (HT) to intermediate intensity (IT), HT to NT, and from IT to NT] for SOC concentration and SOC stock in the upper soil and at lower depths. Results A total of 351 studies were included in the systematic review: 18% from an update of research published in the 2 years since the systematic map. SOC concentration was significantly higher in NT relative to both IT [1.18 g/kg ± 0.34 (SE)] and HT [2.09 g/kg ± 0.34 (SE)] in the upper soil layer (0–15 cm). IT was also found to be significant higher [1.30 g/kg ± 0.22 (SE)] in SOC concentration than HT for the upper soil layer (0–15 cm). At lower depths, only IT SOC compared with HT at 15–30 cm showed a significant difference; being 0.89 g/kg [± 0.20 (SE)] lower in intermediate intensity tillage. For stock data NT had significantly higher SOC stocks down to 30 cm than either HT [4.61 Mg/ha ± 1.95 (SE)] or IT [3.85 Mg/ha ± 1.64 (SE)]. No other comparisons were significant. Conclusions The transition of tilled croplands to NT and conservation tillage has been credited with substantial potential to mitigate climate change via C storage. Based on our results, C stock increase under NT compared to HT was in the upper soil (0–30 cm) around 4.6 Mg/ha (0.78–8.43 Mg/ha, 95% CI) over ≥ 10 years, while no effect was detected in the full soil profile. The results support those from several previous studies and reviews that NT and IT increase SOC in the topsoil. Higher SOC stocks or concentrations in the upper soil not only promote a more productive soil with higher biological activity but also provide resilience to extreme weather conditions. The effect of tillage practices on total SOC stocks will be further evaluated in a forthcoming project accounting for soil bulk densities and crop yields. Our findings can hopefully be used to guide policies for sustainable management of agricultural soils.

1. Reliance on ecosystem services instead of synthetic, non-renewable inputs is increasingly seen as key to achieving food security in an environmentally sustainable way. This process, known as ecological intensification, will depend in large part on enhancing below-ground biological interactions that facilitate resource use efficiency. Arbuscular mycorrhizas (AM), associations formed between the roots of most terrestrial plant species and a specialized group of soil fungi, provide valuable ecosystem services, but the full magnitude of these services may not be fully realized under conventional intensively managed annual agricultural systems. 2. Here, we use meta-analysis to assess how reducing soil disturbance and periods without roots in agricultural systems affect the formation of AM and the diversity and community composition of arbuscular mycorrhizal fungi (AMF). We compiled data from 54 field studies across five continents that measured effects of tillage and/or cover cropping on AMF colonization and/or communities and assessed effects of management and environmental factors on these responses. 3. Less intensive tillage and winter cover cropping similarly increased AMF colonization of summer annual cash crop roots by ~30%. The key variables influencing the change in AMF colonization were the type of cover crop or the type of alternative tillage, suggesting that farmers can optimize combinations of tillage and cover crops that most enhance AM formation, particularly with no-till systems and legume cover crops. 4. Richness of AMF taxa increased by 11% in low-intensity vs. conventional tillage regimes. Several studies showed changes in diversity and community composition of AMF with cover cropping, but these responses were not consistent. 5. Synthesis and applications. This meta-analysis indicates that less intensive tillage and cover cropping are both viable strategies for enhancing root colonization from indigenous arbuscular mycorrhizal fungi (AMF) across a wide range of soil types and cash crop species, and possibly also shifting AMF community structure, which could in turn increase biologically based resource use in agricultural systems.

ABSTRACT Understanding the successional dynamics governing soil microbial community assembly following disturbance can aid in developing remediation strategies for disturbed land. However, the influences shaping microbial communities during succession following soil disturbance remain only partially understood. One example of a severe disturbance to soil is surface mining for natural resources, which displaces communities and changes the physical and chemical soil environment. These changes may alter community composition through selective pressure on microbial taxa (i.e. deterministic processes). Dispersal and ecological drift may also shape communities following disturbance (i.e. stochastic processes). Here, the relative influence of stochastic and deterministic processes on microbial community succession was investigated using a chronosequence of reclaimed surface mines ranging from 2–32 years post-reclamation. Sequencing of bacterial and fungal ribosomal gene amplicons coupled with a linear modeling approach revealed that following mine reclamation, while bacterial communities are modestly influenced by stochastic factors, the influence of deterministic factors was ∼7 × greater. Fungal communities were influenced only by deterministic factors. Soil organic matter, texture, and pH emerged as the most influential environmental factors on both bacterial and fungal communities. Our results suggest that management of deterministic soil characteristics over a sufficient time period could increase the microbial diversity and productivity of mine soils. Soil microbial communities were influenced more by environmental factors than by time following surface mining disturbance.

Improving soil water holding capacity (WHC) through conservation agriculture (CA)-practices, i.e., minimum mechanical soil disturbance, crop diversification, and soil mulch cover/crop residue retention, could buffer soil resilience against climate change. CA-practices could increase soil organic carbon (SOC) and alter pore size distribution (PSD); thus, they could improve soil WHC. This paper aims to review to what extent CA-practices can influence soil WHC and water-availability through SOC build-up and the change of the PSD. In general, the sequestered SOC due to the adoption of CA does not translate into a significant increase in soil WHC, because the increase in SOC is limited to the top 5–10 cm, which limits the capacity of SOC to increase the WHC of the whole soil profile. The effect of CA-practices on PSD had a slight effect on soil WHC, because long-term adoption of CA-practices increases macro- and bio-porosity at the expense of the water-holding pores. However, a positive effect of CA-practices on water-saving and availability has been widely reported. Researchers attributed this positive effect to the increase in water infiltration and reduction in evaporation from the soil surface (due to mulching crop residue). In conclusion, the benefits of CA in the SOC and soil WHC requires considering the whole soil profile, not only the top soil layer. The positive effect of CA on water-saving is attributed to increasing water infiltration and reducing evaporation from the soil surface. CA-practices’ effects are more evident in arid and semi-arid regions; therefore, arable-lands in Sub-Sahara Africa, Australia, and South-Asia are expected to benefit more. This review enhances our understanding of the role of SOC and its quantitative effect in increasing water availability and soil resilience to climate change.

One of the primary challenges of our time is to feed a growing and more demanding world population with reduced external inputs and minimal environmental impacts, all under more variable and extreme climate conditions of the future. Conservation agriculture (CA) represents a set of three crop management principles (direct planting of crops with minimum soil disturbance (i.e. no-till), permanent soil cover by crop residues or cover crops, and crop rotation) that has received strong international support to help address this challenge, with recent CA efforts focusing on smallholder farming systems in Sub-Saharan Africa and South Asia. However, CA is highly debated, both with respect to its effects on crop yields and its applicability in different farming contexts. Here, we conducted a global meta-analysis of 5551 paired yield observations from 613 studies comparing no-till, the original and central concept of CA, to conventional tillage practices across 33 crops and 60 countries. Overall, our results show that no-till reduces yields on average by 4.7% (95% CI: -5.7 to -3.7%) . Importantly, we found that when the other two CA principles are implemented, the negative impacts of no-till are minimized and it takes less time for no-till to match conventional yields following no-till adoption. Moreover, in rainfed agroecosystems under dry climates, no-till in combination with the other two principles significantly increases productivity. While farming systems are multifunctional and both environmental and socio-economic factors need to be considered, our meta-analysis indicates that no-till is an effective longer-term climate change adaptation strategy in ever-becoming-drier regions of the world, but only when it is integrated with residue retention and crop rotation.