Soil Disturbance Research Articles

Soil disturbance induced by shield tunnelling in sensitive clay: In situ test and analyses

Shield tunnelling in sensitive soil causes disturbance to the surrounding soil, damages the soil structure, and results in soil strength reduction. It has a significant impact on the strength and deformation of the soil during shield tunnelling, and further affects the long-term post-construction settlement of the tunnel structure. This paper firstly obtained the soil disturbance and its distribution especially under the tunnel by the in-situ measurement, and the effect of tunneling advancing speed on soil disturbance degree was analyzed. In this paper, in situ tests were performed on an earth pressure balanced (EPB) shield tunnelling site of a subway in deep soft soil layers in Ningbo. Before and after the shield tunnelling, the cone penetration tests (CPTs) were carried out along the axis and profile of the tunnel, and the cross-hole shear wave velocity tests were conducted. Displacement of the surrounding soil and excess pore water pressure (EPWP) were also monitored during shield tunnelling. The results showed that after shield tunnelling the cone penetration resistance (CPR) and shear wave velocity of the surrounding soil decreased remarkably, further confirming that shield tunnelling caused disturbance to the sensitive soft soil. The soil disturbance degree (SDD) is defined based on the CPR, and the soil disturbance boundary caused by shield tunnelling is determined based on distributions of SDD and EPWP. Horizontally, the disturbance boundary of the surrounding soil is located about 0.8D (D represents the tunnel diameter) outside the tunnel, and vertically, the bottom and top of the disturbance boundary are located about 1.29D below and 0.58D above the tunnel. The maximum SDD at the bottom and top of the tunnel reached 80% and 90% respectively, and the average SDD of the disturbance range below the tunnel is about 60%. The testing results indicated that a higher advancing speed causes a greater disturbance to the surrounding soil, and all the analysis results provide helpful guidance for optimizing the EPB shield tunnelling and reducing soil disturbance.

Characteristic and Physicochemical Properties of Peat Soil Stabilized with Sodium Hydroxide (NaOH)

Peat in various phases of decomposition has poor shear strength and high compressive deformation. For this research study, it will focus on stabilizing peat soil using NaOH. There are two main tests that were conducted in this research study, which are index property testing and the compaction test. For index property testing, there were six (6) experiments conducted to study the index properties of disturbed peat soil, which are moisture content, fiber content, organic content, liquid limit, pH, and specific gravity. Then, for the compaction test, a 4.5kg rammer was used to determine the best mixture of stabilizer blended with different volumes of 5%, 7%, and 9% stabilizer. The desired outcome of this study is to stimulate further research into the use of the chemical NaOH as a peat soil stabilizer for improved soil usage. 7% and 9% of NaOH only have a slightly different percentage, and it can be concluded that this was the optimum percentage of NaOH as a chemical stabilizer for peat soil. It can be seen clearly that 5% is the higher dry density with a lesser moisture content of the peat. When the percentage of NaOH was increased, the graph pattern also changed. NaOH has been observed as an alteration agent for peat soil dry density. It can be seen clearly that 5% NaOH is the higher dry density of the peat with the lesser moisture content and is suitable as a peat soil stabilizer. The increment of oxygen content recorded changes from 13.3% to 23%, while the sodium (Na) content decreased significantly with the increment of oxygen (O). Sodium content decreased from 8.7% for untreated specimens to 4.5% and 5.5% when peat was treated with NaOH, with 5% of NaOH and 9% of NaOH. Doi: 10.28991/CEJ-2023-09-09-09 Full Text: PDF

English

Conservation agriculture (CA) aims to achieve productive and sustainable farming while preserving the natural resource base and environment. This article explores how CA aligns with Sustainable Development Goals (SDGs) of the United Nations and contributes to their achievement, particularly SDG 2: Zero Hunger, SDG 6: Clean Water and Sanitation, SDG 12: Responsible Consumption and Production, SDG 13: Climate Action, and SDG 15: Life on Land. CA has gained significant attention as a sustainable farming system on over 200 million hectares of global cropland, with an annual increase of 10 million hectares since 2008. The principles of minimum soil disturbance, diverse crop rotations and permanent soil cover help improve soil health, nutrients and water management, and contribute to biodiversity preservation. By encouraging sustainable agriculture and enhancing nutrition, SDG 2 seeks to end hunger. CA practices enhance soil health and nutrient availability, increasing crop productivity and reducing reliance on synthetic inputs like pesticides and fertilizers. The resilience of CA to climate change challenges further supports food production. For SDG 6, minimum tillage and soil cover components of CA help reduce soil erosion, resulting in cleaner water by preventing sedimentation in water bodies. Improved water management and conservation contribute to sustainable water use and sanitation. SDG 12 seeks responsible consumption and production patterns. CA promotes efficient resource use, reduces waste, and minimizes the negative environmental impact of agricultural inputs, leading to sustainable production systems with less reliance on external inputs. Regarding SDG 13, CA practices improve soil and water management, increase soil carbon absorption, and lower greenhouse gas emissions, all of which help agricultural systems become more resilient to climate change. Lastly, SDG 15 focuses on life on land preservation. CA's promotion of biodiversity through cover cropping and decreased chemical use provides habitats for organisms, supporting ecosystem services and sustainable land use. In conclusion, CA plays a significant role in achieving multiple SDGs by promoting sustainable agriculture, conserving resources, mitigating climate change, and preserving biodiversity. The adoption and expansion of CA practices are essential for a sustainable and resilient future

Perceptions and sociocultural factors underlying adoption of conservation agriculture in the Mediterranean

The Mediterranean region is facing major challenges for soil conservation and sustainable agriculture. Conservation agriculture (CA), including reduced soil disturbance, can help conserve soils and improve soil fertility, but its adoption in the Mediterranean region is limited. Examining farmers’ perceptions of soil and underlying sociocultural factors can help shed light on adoption of soil management practices. In this paper, we conducted a survey with 590 farmers across Morocco, Spain and Tunisia to explore concepts that are cognitively associated with soil and perceptions of tillage. We also evaluated differences in perceptions of innovation, community, adaptive capacity, and responsibility for soil. We found that farmers’ cognitive associations with soil show awareness of soil as a living resource, go beyond agriculture and livelihoods to reveal cultural ties, and link to multiple levels of human needs. Beliefs about the benefits of tillage for water availability and yield persist among the surveyed farmers. We found that openness towards innovation, perceived adaptive capacity and responsibility for soil were associated with minimum tillage, whereas community integration was not. Education, age and farm lifestyle were also associated with differences in these perceptions. CA promotion in the Mediterranean should emphasize the multiple values of soil, should demonstrate how sufficient yields may be achieved alongside resilience to drought, and be tailored to differing levels of environmental awareness and economic needs across north and south.

The Good, the Bad, and the Useable Microbes within the Common Alder (Alnus glutinosa) Microbiome-Potential Bio-Agents to Combat Alder Dieback.

Common Alder (Alnus glutinosa (L.) Gaertn.) is a tree species native to Ireland and Europe with high economic and ecological importance. The presence of Alder has many benefits including the ability to adapt to multiple climate types, as well as aiding in ecosystem restoration due to its colonization capabilities within disturbed soils. However, Alder is susceptible to infection of the root rot pathogen Phytophthora alni, amongst other pathogens associated with this tree species. P. alni has become an issue within the forestry sector as it continues to spread across Europe, infecting Alder plantations, thus affecting their growth and survival and altering ecosystem dynamics. Beneficial microbiota and biocontrol agents play a crucial role in maintaining the health and resilience of plants. Studies have shown that beneficial microbes promote plant growth as well as aid in the protection against pathogens and abiotic stress. Understanding the interactions between A. glutinosa and its microbiota, both beneficial and pathogenic, is essential for developing integrated management strategies to mitigate the impact of P. alni and maintain the health of Alder trees. This review is focused on collating the relevant literature associated with Alder, current threats to the species, what is known about its microbial composition, and Common Alder-microbe interactions that have been observed worldwide to date. It also summarizes the beneficial fungi, bacteria, and biocontrol agents, underpinning genetic mechanisms and secondary metabolites identified within the forestry sector in relation to the Alder tree species. In addition, biocontrol mechanisms and microbiome-assisted breeding as well as gaps within research that require further attention are discussed.

The sticky hemiparasitic plant Parentucellia viscosa catches hostplant seeds that may provision its descendants

In addition to physiological functions, sticky plant trichomes perform a variety of anti-herbivory functions, such as deterring invertebrate and mammalian herbivores, and attracting the natural predators of stuck arthropods by providing them with immobilized prey. However, since the adaptive value of sticky glands has only been studied in a small fraction of trichrome-bearing plant species, other functions of these structures may yet be discovered. Several hemiparasitic plants, which obtain nutrients by both photosynthesis and from the roots of other plants, bear dense glandular trichomes on their aboveground parts. Field observations of the alien hemiparasitic plant Parentucellia viscosa were conducted in central Japan. The plants colonized a sparsely vegetated riverbank and gradually increased in number over time. The glandular trichomes on the plants not only entrapped small insects, but also grass seeds. It is thus possible that various sticky hemiparasitic plants, including P. viscosa, may intercept and capture the dispersed seeds of other plants, ensuring that their own seeds germinate in the same vicinity as those of the dispersing hostplant seeds in the following season. In so doing, P. viscosa may provision future juvenile plants with potential hosts. This scenario may be restricted to the early colonizing phase on plantless areas of disturbed soil. The seed-intercepting function of the glandular trichomes may act in conjunction with direct and indirect anti-herbivore defenses, and lower the dispersal of seeds of wind-borne plants in the vicinity beyond the reach of this hemiparasite.

Managing the pore system: Regenerating the functional pore spaces of natural soils by soil-health oriented farming systems

Transition towards soil-health sustaining crop production is at the core of climate change mitigation and adaptation efforts in agriculture. Improving soil conditions for resilience to variable and extreme weather conditions are among the main expectations of farmers implementing sustainable management practices. In this study, we evaluate whether the transition from conventional arable towards soil-health oriented farming systems restores soil pore characteristics towards non-arable natural soils and identify factors predominantly shaping different pore domains. Pore size distributions (PSD) at 20 sites with diverse soil types from adjacent fields of (1) standard arable, (2) soil health-oriented pioneer farming and (3) non-arable natural reference soils were measured. Based on parametric PSD descriptors, management-responsive functional pore classes and the role of textural, biochemical and structural drivers in different pore domains were analysed by a novel data-driven evaluation method. Parametric descriptors indicate an evolution from non-disturbed natural to intensively disturbed standard arable soils towards larger structural pores within a less heterogeneous structural domain. These shifts go along with less medium-sized storage pores, which overall was the most management sensitive pore fraction. Our novel data-driven approach confirmed a partial regeneration of natural pore characteristics with soil-health oriented practices. The most responsive pore domain was found in the range of ∼0.3–0.5 µm. The SOC-to-clay ratio was the predominant driver for structural porosity in both pioneer arable and natural reference soils. On the contrary, soil texture exerted the main control on the PSD pattern over the entire range of pore classes for standard farming systems. Overall, our study demonstrated that soil-health oriented pioneer farmers could effectively advance in managing functionally relevant pore domains for climate change resilience by promoting biological agents of structure formation.

Deterministic Development of Soil Microbial Communities in Disturbed Soils Depends on Microbial Biomass of the Bioinoculum.

Despite its enormous importance for ecosystem services, factors driving microbial recolonization of soils after disturbance are still poorly understood. Here, we compared the microbial recolonization patterns of a disturbed, autoclaved soil using different amounts of the original non-disturbed soil as inoculum. By using this approach, we manipulated microbial biomass, but did not change microbial diversity of the inoculum. We followed the development of a new soil microbiome after reinoculation over a period of 4 weeks using a molecular barcoding approach as well as qPCR. Focus was given on the assessment of bacteria and archaea. We could show that 1 week after inoculation in all inoculated treatments bacterial biomass exceeded the values from the original soil as a consequence of high dissolved organic carbon (DOC) concentrations in the disturbed soil resulting from the disturbance. This high biomass was persistent over the complete experimental period. In line with the high DOC concentrations, in the first 2 weeks of incubation, copiotrophic bacteria dominated the community, which derived from the inoculum used. Only in the disturbed control soils which did not receive a microbial inoculum, recolonization pattern differed. In contrast, archaeal biomass did not recover over the experimental period and recolonization was strongly triggered by amount of inoculated original soil added. Interestingly, the variability between replicates of the same inoculation density decreased with increasing biomass in the inoculum, indicating a deterministic development of soil microbiomes if higher numbers of cells are used for reinoculation.

Soil disturbance, amelioration and rehabilitation affect forest growth, health, soil carbon and chemistry on five long-term soil productivity (LTSP) sites in southeastern British Columbia

Soil disturbance amelioration affected tree survival, growth, health, mineral soil chemistry, and their covariation on five Long-Term Soil Productivity (LTSP) sites in southeastern British Columbia. The two most different LTSP treatments (baseline disturbance of no compaction / all organic matter left, versus most severe of heavy compaction / forest floor removed) were compared to five amelioration treatments: rehabilitation of most severe LTSP treatment (soil tillage with or without incorporation of removed forest floor [Rehab + FF]), root disease (Armillaria ostoyae (Romagn.) Herink) amelioration treatments (stump removal or biological with Hypholoma fasiculare), and enhancement of soil organic matter (tilling extra forest floor into mineral soil). Treatment significantly (p < 0.05) affected 10-year mineral soil carbon, nitrogen, sulfur, mineralizable nitrogen, and potassium, which were lower on forest floor removal treatments and higher on forest floor addition treatments (27 to 97% of baseline versus 78 to 183% of baseline, respectively). Western white pine (Pinus monticola Dougl. ex D.Don) 15-year productivity (m3/ha) was significantly affected by treatment (Rehab + FF yielding a 10 fold increase in productivity versus the poorly growing baseline treatment), with treatment also significant when total disease was a covariate and for average and total volume when mineral soil Ca:Al ratio was a marginally significant (p < 0.1) covariate, and for survival when the incidence of total disease or white pine blister rust (Cronartium ribicola) were significant covariates; or with mineral soil C:N ratio as a significant covariate. The incidence of blister rust and total disease were significantly influenced by treatment when C:N was a significant covariate. For 20-year lodgepole pine (Pinus contorta Dougl. Ex Loud) there were no direct relationships apparent, but western gall rust (Endocronartium harknessii) had treatment significant when total sulfur was a significant covariate. Fifteen- and twenty-year Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) had no significant relationships. Results demonstrate that restoring or adding extra organic matter (forest floor) into mineral soil increased soil carbon and related nutrients and can increase above ground carbon (forest productivity). Conversely, removing forest floor lowered mineral soil carbon and generally lowered tree volume. Varied effects due to growth limiting factors like frost and competing vegetation affected results on a few plots. Recommendations include leaving or enhancing organic matter onsite for soil carbon, nutrients, forest health and site productivity. Further analysis with the larger LTSP dataset and ongoing monitoring is encouraged to determine if the results persist in the long-term and to better understand the significant covariate relationships.

Recolonizing native wildlife facilitates exotic plant invasion into Singapore's rain forests

AbstractHalting biological invasions and rewilding extirpated native fauna are conservation interventions to bolster biodiversity, species interactions, and ecosystems. These actions are often considered separately and the potential for reintroduced wildlife to facilitate invasive plants has been largely overlooked. Here, we investigated the role of Singapore's recolonizing native wild pigs (Sus scrofa) in facilitating an invasive weed Miconia crenata into tropical rainforests, which are normally highly resistant to invasion. We conducted line‐transect surveys in 11 Singaporean rain forests and used generalized linear mixed models to consider the contribution of pigs' soil disturbances, human forest paths, and other environmental covariates, on the density of M. crenata. We found that M. crenata was more abundant at forest edges and invasion into forest interior was facilitated by pigs, paths, and canopy gaps, but that these effects were all additive, not synergistic (i.e., not multiplicative). These results highlight how modern invasions are driven by multiple disturbances as well as propagule pressure (e.g., urban birds dispersing seeds at forest edges where they establish in pig soil disturbances). Singapore's extensive native forest restoration efforts may have provided plentiful edge and secondary forests that are well suited to pigs and M. crenata, which in turn undermine the aims of fostering later‐successional native plant communities. To prevent negative externalities, we suggest that plant restoration and rewilding projects consider the potential role of wildlife in facilitating non‐native plants, and couple these actions with preliminary screening of unintended consequences and continued monitoring, as well as limiting human‐mediated weed invasion to minimize propagule sources.

Summer rain and wet soil rather than management affect the distribution of a toxic plant in production grasslands

In the northern forelands of the Alps, farmers report an increase of Jacobaea aquatica in production grasslands. Due to its toxicity, the species affects grassland productivity and calls for costly control measures. We are investigating the extent to which management practices or climatic factors are responsible for the increase of the species and how the situation will change due to climate change. We tested for effects of management intensity, fertilization, agri-environmental measures, and soil disturbance, and modeled the occurrence of the species under rcp4.5 and rcp8.5 scenarios. The main determinants of the occurrence of the species are soil type and summer rainfall. A high risk is associated with wet soils and > 400 mm of rain between June and August; an influence of the management-related factors could not be detected. Under the climate-change scenarios, the overall distribution decreases and shifts to the wetter alpine regions. Thus, the current increase is rather a shift in the occurrence of the species due to the altered precipitation situation. Under future climatic conditions, the species will decline and retreat to higher regions in the Alps. This will decrease the risk of forage contamination for production grassland in the lowlands.

Assessing N2O Emissions from Tropical Crop Cultivation in Mineral and Peatland Soils: A Review

&lt;p&gt;Nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O) emissions from agricultural activities contribute significantly to global warming. Understanding the factors influencing N&lt;sub&gt;2&lt;/sub&gt;O emissions is crucial for developing effective mitigation strategies. This review assesses N&lt;sub&gt;2&lt;/sub&gt;O emissions from various crops cultivated in tropical mineral and peatland soils, providing insights into the impact of land use, fertilization practices and rainfall on N&lt;sub&gt;2&lt;/sub&gt;O fluxes. Field measurements of N&lt;sub&gt;2&lt;/sub&gt;O fluxes were conducted in agricultural fields growing corn, peanuts, and cassava in Bogor Regency, West Java Province, as well as in peatland areas with Acacia plantations and natural primary forests in Bengkalis Regency, Riau Province. The study assesses the total N&lt;sub&gt;2&lt;/sub&gt;O fluxes for each crop and land type, revealing significant variations in N&lt;sub&gt;2&lt;/sub&gt;O emissions among different crops and land uses. Peatland areas exhibit higher emissions compared to mineral soils, emphasizing the need for targeted mitigation measures in these ecosystems. The findings highlight the importance of considering the type and age of land use when evaluating N&lt;sub&gt;2&lt;/sub&gt;O emissions. Land management practices, such as fertilizer use and soil disturbance, emerge as critical factors affecting N&lt;sub&gt;2&lt;/sub&gt;O emissions. Improper fertilizer application and excessive soil disturbance can lead to increased N&lt;sub&gt;2&lt;/sub&gt;O emissions, underscoring the necessity for careful N fertilizer management and conservation tillage techniques.&lt;/p&gt;

Synergism between production and soil health through crop diversification, organic amendments and crop protection in wheat‐based systems

Abstract One of the critical challenges in agriculture is enhancing yield without compromising its foundation, a healthy environment and, particularly, soils. Hence, there is an urgent need to identify management practices that simultaneously support soil health and production and help achieve environmentally sound production systems. To investigate how management influences production and soil health under realistic agronomic conditions, we conducted an on‐farm study involving 60 wheat fields managed conventionally, under no‐till or organically. We assessed 68 variables defining management, production and soil health properties. We examined how management systems and individual practices describing crop diversification, fertiliser inputs, agrochemical use and soil disturbance influenced production—quantity and quality—and soil health focusing on aspects ranging from soil organic matter over soil structure to microbial abundance and diversity. Our on‐farm comparison showed marked differences between soil health and production in the current system: organic management resulted in the best overall soil health (+47%) but the most significant yield gap (−34%) compared to conventional management. No‐till systems were generally intermediate, exhibiting a smaller yield gap (−17%) and only a marginally improved level of soil health (+5%) compared to conventional management. Yet, the overlap between management systems in production and soil health properties was considerably large. Our results further highlight the importance of soil health for productivity by revealing positive associations between crop yield and soil health properties, particularly under conventional management, whereas factors such as weed pressure were more dominant in organic systems. None of the three systems showed advantages in supporting production‐soil health‐based multifunctionality. In contrast, a cross‐system analysis suggests that multifunctional agroecosystems could be achieved through a combination of crop diversification and organic amendments with effective crop protection. Synthesis and applications: Our on‐farm study implies that current trade‐offs in managing production and soil health could be overcome through more balanced systems incorporating conventional and alternative approaches. Such multifunctionality supporting systems could unlock synergies between vital ecosystem services and help achieve productive yet environmentally sound agriculture supported by healthy soils.

Conservation agriculture practices in a peanut cropping system: Effects on pod yield and soil penetration resistance

ABSTRACT Conservation agriculture principles applied to peanut can reduce soil erosion and production costs when cultivated in rotation with sugarcane. Still, the problem with soil compaction is the leading cause of skepticism about the efficacy of this practice. This research aimed to study the effect of three soil management strategies compared with conventional for peanut cv. IAC-OL3, cultivated in rotation with sugarcane using the MEIOSI (method of intercropping occurring simultaneously) system for agronomic practices with additional analysis on changes in soil physics properties. The trial was conducted in 2019-2020 in Planalto municipality (São Paulo, Brazil) under a green-harvested sugarcane field, using a randomized complete block experimental design. The trial consisted of four soil management treatments (conventional tillage, minimum tillage with chisel, strip-tillage, and no-tillage) with five replications. Although no differences were verified in soil bulk density and porosity among treatments, the highest values of soil penetration resistance were observed in no-tillage treatment for all evaluations (before planting, at the beginning of flowering, and before and after harvesting) in comparison with conventional tillage. The difference in soil penetration resistance among the treatments diminished from planting to the end of the cycle. Furthermore, low soil disturbance and maximum covering with straw significantly increased the available water capacity and reduced the incidence and severity of groundnut ringspot virus (GRSV) on peanut plants. Consequently, both minimum-tillage and no-tillage have increased the pod yield on average by 695 and 991 kg ha -1 more than strip-tillage and conventional tillage, respectively, without differences in terms of quality and pod losses.

Mound‐building behaviour of a keystone bioturbator alters rates of leaf litter decomposition and movement in urban reserves

AbstractBioturbation, the disturbance of soil and litter by digging animals plays an important role for a variety of species and ecological processes in many ecosystems. The majority of studies globally on the ecosystem engineering effects of digging vertebrates have focussed on mammals, with birds, reptiles and amphibians remaining comparatively understudied. The loss of ecosystem engineers is a key conservation challenge, and the return of these species is increasingly seen as a priority for habitat restoration; yet this concept is highly novel when we consider urban ecosystems. The Australian brush‐turkey (Alectura lathami), historically a rainforest bird and now common in urban ecosystems, displaces significant quantities of soil and leaf litter through its foraging and nest‐building behaviour and has previously been described as an ecosystem engineer. Here, we tested the effect of brush‐turkey nest building on the decomposition rate of leaf litter, an important ecosystem process. We placed mesh bags of dried Angophora costata and Lantana camara leaves at increasing distances from brush‐turkey incubation mounds. We predicted that leaf litter closer to the nest would break down faster during the brush‐turkey breeding season due to increased turnover associated with nest mound maintenance. We found slower leaf litter decomposition in the breeding than the non‐breeding season, but a relatively greater rate of decomposition closer to the mound in the breeding season. Our results show a seasonal difference in the spatial pattern of leaf litter decomposition and movement; we interpret that brush‐turkey mound‐building behaviour was the key driver. The ecosystem services provided by brush‐turkeys are of particular interest for future research as this species is naturally recolonizing areas where it has been absent for decades, including urban areas. The effect of this species on ecosystem processes including nutrient cycling, seedbank stimulation and reduced fuel loads warrants further investigation.

The influence of microtopography on soil carbon accumulation and nutrient release from a rewetted coastal peatland

Coastal peatlands have been frequently blocked from the sea and artificially drained for agriculture. With an increasing awareness of ecosystem functions, several of these coastal peatlands have been rewetted through dike removal, allowing seawater flooding. In this study, we investigated a recently rewetted peatland on the Baltic Sea coast with the aim to characterize the prevailing soils/sediments with respect to organic matter accumulation and the potential release of nutrients upon seawater flooding. Eighty disturbed soil samples were collected from two depths at different elevations (–0.90 to 0.97 m compared to sea level) and analyzed for soil organic matter (SOM) content and carbon:nitrogen (C:N) ratio. Additionally, nine undisturbed soil cores were collected from three distinct elevation groups and used in leaching experiments with alternating freshwater and Baltic Sea water. The results demonstrated a moderate to strong spatial dependence of surface elevation, SOM content, and C:N ratio. SOM content and C:N ratio were strongly negatively correlated with elevation, indicating that organic matter mineralization was restricted in low-lying areas. The results also showed that the soils at low elevations release more dissolved organic carbon (DOC) and ammonium (NH4+) than soils at high elevations. For soils at low elevations, higher DOC concentrations were observed when flushing with freshwater, whereas higher NH4+ concentrations were found when flushing with brackish water. Recorded NH4+ concentrations in organic-rich peat reached 14.82 ± 9.25 mg L–1, exceeding Baltic seawater (e.g., 0.03 mg L–1) by two orders of magnitude. A potential sea level rise may increase the export of NH4+ from low-lying and rewetted peat soils to the sea, impacting adjacent marine ecosystems. Overall, in coastal peatlands, geochemical processes (e.g., C and N cycling and release) are closely linked to microtopography and related patterns of organic matter content of the soil and sediments.

Various no-tillage years with previous residual plastic film mulching improved soil properties and agricultural benefits in an arid region

No-tillage (NT) with residual plastic film from an earlier year (NTR) is adopted in arid regions to reduce plastic film residue, decrease soil disturbances, and increase water use efficiency (WUE) and agricultural benefits. However, the effects of NTR on soil crop systems are more complex because of the high disintegrated fraction (DF) of residual plastic film and stronger soil compaction under NT. Additionally, the optimum number of years for NTR is still not elucidated. Therefore, we studied the effects of conventional tillage and NT with a new plastic film mulching (CTN and NTN, respectively) and those of 1, 2, and 3 years of NTR on soil physical properties, soil water content (SWC), maize root and shoot growth, yield, and economic benefits. The experiment was conducted for 3 years in Hetao Irrigation District, China, from 2019 to 2021. The results revealed that the longer the duration of NT (including NTN and NTR), the higher the soil bulk density and lower the total soil porosity than those under CTN in 0–30 cm soil layer. SWC decreased due to the increase in the DF of residual plastic film from NTR. In the third year (2021), SWC under NTR reduced by 5.1 % compared with that under NTN. Additionally, with the increase of NTR years, the maize root and shoot dry biomass and root to shoot ratio clearly decreased under NTR compared with those under CTN and NTN. However, the root volume density of very fine roots under NTR increased significantly in the first 2 years (2019 and 2020) of NT. The yield and WUE decreased slightly under NTR compared with those under CTN in 2019 and 2020; but the net revenue increased by 15.7 % and 9.6 %, respectively. Conversely, the significant decrease in the yield and WUE was observed under NTR compared with those under CTN in 2021 led to a 15.6 % decrease in net revenue. Moreover, a higher sustainability index was observed in the first 2 years. Therefore, NTR with 2 years can be recommended as the optimal local tillage measure with the decrease in the amount of residual plastic film and increased farm economic benefits.

Soil Health Assessment to Evaluate Conservation Practices in SemiArid Cotton Systems at Producer Site Scale

Maintaining soil health and sustainable crop production has been challenged by climate variability and wind erosion in semi-arid regions. To understand the initial effects of the transition of tilled cotton systems to no-tillage with winter wheat as a cover crop, we sampled 18 commercial grower sites from 2019 to 2022 in the Southern High Plains (SHP). We evaluated the soil biological component, which often responds rapidly to changes in residue additions or minimized soil disturbance providing an early indication of changes in soil health, especially in the low organic matter soils in this region. After two years, compared to tilled systems, no-till systems had significant increases in ester-linked fatty acid methyl ester (EL-FAME) bacterial and saprophytic and AMF fungal markers, enzyme activities of nutrient cycling, and various SOM pools, under both center-pivot irrigation and dryland. Similar increases were also observed in two dryland sites sampled before and up to two years after transition to no-till. Our study demonstrates the potential of no-tillage and cover crops to improve soil health in cotton production in semiarid regions, and a framework for a soil health assessment that links different soil health indicators with functions related to soil organic matter, soil water, and biogeochemical cycling.

Megapode mound-builders (malleefowl, Leipoa ocellata) enhance soil function through altered bacterial community composition

Many ecosystem engineers disturb and turn over soil, enhancing soil function and productivity by increasing enzyme activity and altering microbial community composition. In semi-arid mallee woodlands, soil-disturbing malleefowl (Leipoa ocellata: Megapodiidae) create a novel microsite with unique soil chemistry and cover characteristics when they build incubation mounds. Malleefowl mounds likely enhance soil functioning, providing habitat for decomposer organisms and facilitating organic material decomposition, however this has yet to be empirically measured.We sampled soil bacterial communities and soil enzymes at five microsites: malleefowl mounds (1), high-resource patches underneath trees near malleefowl mounds (2) and far from mounds (3), and in the low-resource interpatch matrix near mounds (4) and far from mounds (5). Samples were taken from mounds of different ages. Bacterial DNA was extracted and sequenced, and we performed functional profiling to predict metabolic pathways.We found that mound-building by malleefowl significantly enhanced soil processes: microsites had distinct bacterial communities, including impacts on the relative abundance of the most common bacterial phyla. Microbial functional profiling revealed that mounds had an increase in pathways involved in degradation, and enzyme activity at the mound was comparable to the high-resource patches underneath trees, and significantly higher than the low-resource interpatch matrix. SynthesisMalleefowl soil disturbance could promote nutrient cycling via enriching bacterial communities and their activities involved in organic material degradation. The mound provides a stable environment, which combines many optimal features for decomposer microbes. These results strengthen our understanding of the impact that avian soil disturbance can have on soil function by enhancing multifunctionality in a depauperate arid ecosystem.

A Bayesian machine learning method to explain the error characteristics of global-scale soil moisture products

Estimating accurate surface soil moisture (SM) dynamics from space, and knowing the error characteristics of these estimates, is of great importance for the application of satellite-based SM data throughout many Earth Science/Environmental Engineering disciplines. Here, we introduce the Bayesian inference approach to analyze the error characteristics of widely used passive and active microwave satellite-derived SM data sets, at different overpass times, acquired from the Soil Moisture Active Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), and Advanced Scatterometer (ASCAT) missions. In particular, we apply Bayesian hierarchical modeling (BHM) and triple collocation analysis (TCA) to investigate the relative importance of different environmental factors and human activities on the accuracy of satellite-based data.To start, we compare the BHM-based sensitivity analysis method to the classic multiple regression models using a frequentist approach, which includes complete pooling and no-pooling models that have been widely used for sensitivity analysis in the field of remote sensing and demonstrate the BHM's adaptability and great potential for providing insight into sensitivity analysis that can be used by various remote sensing research communities.Next, we conduct an uncertainty analysis on BHM's model parameters using a full range of uncertainties to assess the association of various environmental factors with the accuracy of satellite-derived SM data. We focus on investigating human-induced error sources such as disturbed surface soil layers caused by irrigation activities on microwave satellite systems, naturally introduced error sources such as vegetation and soil organic matter, and errors related to the disregard of SM retrieval algorithmic assumptions - such as the thermal equilibrium passive microwave systems. Based on the BHM-based sensitivity analysis, we find that assessments of SM data quality with a single variable should be avoided, since numerous other factors simultaneously influence their quality. As such, this provides a useful framework for applying Bayesian theory to the investigation of the error characteristics of satellite-based SM data and other time-varying geophysical variables.