Role Of Soil Properties Research Articles

Grain yield and nitrogen cycling under conservation agriculture and biochar amendment in agroecosystems of sub-Saharan Africa. A meta-analysis

Soil nitrogen (N) is one of the most limiting factors affecting crop production in sub-Saharan Africa (SSA). Here we conducted a meta-analysis on the effect of climate smart agricultural (CSA) practices (conservation agriculture (CA) and/or biochar (BC)) application on: (1) soil nitrate-N (NO3-N), nitrous oxide (N2O) emission, biological N2-fixation, percent of nitrogen derived from the atmosphere (%Ndfa), grain yield and nitrogen use efficiency (NUE), (2) the role of soil properties and regions on grain yield and N cycling under CA and/or BC biochar application; and (3) the relationship between inorganic N fertilizer and NO3-N, N2O emissions, NUE and grain yield. We synthesized 87 unique papers, from 15 countries in SSA with 1643 paired observations. On average across all studies, CA and/or BC significantly increased grain yield and NUE, compared to conventional practices. Residue retention resulted in a significant increase in soil NO3-N and N2O emission, compared to conventional practices. Our analysis further indicates that BC application significantly increased biological N2-fixation, grain yield and NUE. Auxiliary soil parameters also affected grain yield and N cycling. Grain yield was significantly influenced by total organic carbon classes (TOC), whereby highest grain yield was recorded under CSA in soils with 0.5–1 % TOC, compared to soils with < 0.5 % TOC and > 1 % TOC. In addition, total nitrogen (TN) significantly affected the response ratio of CSA and conventional agriculture on N2O emission and biological N2-fixation. N2O emission increased significantly in soils with < 0.05 % TN, while biological N2-fixation increased significantly in soils with > 0.2 % TN. Increasing N fertilizer use significantly increased the response ratio of CSA and conventional agriculture on N2O and NO3-N while significantly reducing the response ratio of yield and NUE. The gap in yield and NUE between CSA and conventional agriculture practises was more pronounced at lower N rates of 0 kg ha−1 and narrowed as N input increased to 120 kg ha−1; this implies that, CSA offers more benefits compared to conventional agricultural practices under low N rates.

Containing alien plants in coastal dunes: Evidence from a soil manipulation experiment

Biological invasion is recognised as one of the major threats to biodiversity, particularly in disturbance-prone ecosystems such as costal dunes. Many studies have associated alien plant invasion of dune ecosystem to human disturbances, but less is known about the role of soil properties in invasion after disturbance. Soil properties are crucial filters during plant succession and soil-related changes in the initial stage of species colonization might shape the final success of the invaders.We performed a manipulative experiment aimed at elucidating the effects of soil properties on plant colonization processes in highly invaded dune systems, as a proxy for plausible management actions to curb the success of exotic plant species over native ones, which was measured through species richness and abundance.In a barrier island of the Marano and Grado lagoon, Northern Adriatic Sea, we mechanically removed all the native and alien vegetation present in the back dune (also known as secondary dune), triggering a new ecological succession and further altered, for the following three months, soil properties by adding salt, nitrogen, and organic matter in a full factorial design with randomized blocks.The soil treatments reduced the overall species richness and abundance of alien plants. Further, soil treatment interactions strongly shaped community evenness and species richness. Soil salinity had a positive effect on native cover while decreasing the overall number of alien species, especially in soil with added organic matter.Our findings suggest that soil salinity, and its interplay with organic matter, might significantly reduce the initial success of alien species propagule pressure (i.e. alien plant germination), with likely implications for the trajectories of future plant communities. This study highlights that alien plant containment should be focused on early stages of succession, giving new perspective on future environmental management actions for dune restoration and conservation.

Connecting forest soil properties with ecosystem services: Toward a better use of digital soil maps—A review

AbstractThe soil supports many ecosystem services (ES) essential to human well‐being. Rapid developments in digital soil mapping (DSM) allow the mapping of soil types and soil properties with improved resolution and accuracy. However, the potential of DSM to improve the assessment and mapping of ES is not fully exploited. To better understand this potential, we synthesized the peer‐reviewed literature. We examined what empirical studies reveal about the role of soil properties in the assessment of four major ES provided by the forest: (I) timber production, (II) soil carbon storage, (III) regulation of water flow and provision of clean water, and (IV) the soil as a habitat for organisms. Results revealed that soil properties are strongly related to the provision of ES. Therefore, using DSM could greatly improve the assessment of the ES provided by forests. Several variables were related to specific ES regardless of region or ecosystem types, but others were found to be situation‐specific (climate and soil type) and need to be considered at the proper scale or within a proper land classification framework. DSM products have the potential to greatly improve the assessment of ES by turning qualitative relationships between soil and ES to quantitative ones. This could also lead to the discovery of new soil–ES relationships. For this potential to be realized, progress should be made in mapping the most crucial soil parameters with greater precision and in promoting the use of soil parameters in ES assessment.

New insights into the role of soil properties in driving cadmium-induced hormesis in soil alkaline phosphatase under vegetation cover change

This study investigated the hormetic responses of soil alkaline phosphatase (ALP) to exogenous Cd under five different vegetation cover types in a typical coastal wetland, including mudflat (Mud), Phragmites australis (PA), Spartina alterniflora (SA), Metasequoia glyptostroboides (MG), and Cinnamomum camphora (CC). The results showed that the activity of soil ALP was significantly enhanced by exogenous 0.3–1.0, 0.2–0.8, 0.05–0.3, 0.05–0.6, and 0.05–0.60 mg Cd /kg in Mud, PA, SA, MG, and CC, respectively. Moreover, the Horzone (an integrated indicator of the stimulation phase) of Mud and PA was significantly higher than that of SA, MG, and CC. Multiple factor analysis revealed that soil chemical properties and soil bacteria community play an important role in the hormetic effect of soil ALP to Cd stress. Soil electric conductivity (EC) and the relative abundance of Gammaproteobacteria were also identified as key drivers of the hormetic effects of Cd on soil ALP under five vegetation cover types. These findings suggest that the soil ecosystem had better resistance to exogenous Cd stress under mudflat and native species (PA) than invasive species (SA), and artificial forests (MG and CC) when soil ALP activity was the test endpoint. Consequently, this study is beneficial for future ecological risk assessment of soil Cd contamination under divergent vegetation covers.

Dynamics of soil net nitrogen mineralization and controlled effect of microbial functional genes in the restoration of cold temperate forests

Soil nitrogen mineralization (Nmin) generally controls the availability and circulation of soil nitrogen (N). To better understand the mechanisms of soil Nmin and environmental protection, this study explored the dynamics of net Nmin in soils from restored forests and the effect of soil physicochemical properties (SPPs) and soil microbial mineralization genes (SMGs) on Nmin. Field studies were conducted from July 2019 to April 2020 in five representative restored forests in the mountainous region of northwestern Hebei, China (i.e., Larix principis-rupprechtii forest (LF), Betula platyphylla forest (BF), mixed forest of Larix principis-rupprechtii and Betula platyphylla (MF), Picea asperata forest (SF) and Pinus sylvestris var. mongolica forest (MPF)), and soil net nitrogen mineralization rate (Rmin), SPPs and SMGs were determined after collecting soil samples in five plots. The influence of restored forests and seasonality on Rmin was investigated to determine the characteristics of the dynamics of soil net Nmin. Principal component analysis (PCA) and variation partitioning analysis (VPA) revealed that soil properties and functional genes could explain approximately 80 % of the variation in Nmin. SMGs significantly contributed to the variation in the soil net ammonification rate (Ramm) and nitrification rate (Rnit) compared to soil properties. SMGs were strongly correlated with Ramm\\Rnit (except in LF), implying that the shifts in functional genes may control Rmin. Given the debate on the role of soil properties and N cycling genes in driving soil N transformation, this study provides new insights into the controlled effect of microbial functional genes during the early stage of forest restoration in the cold temperate zone.

Efficiency of selenium biofortification of spring wheat: the role of soil properties and organic matter amendment

The effect of soil selenate application to two different soils (Phaeozem and Cambisol) on biomass yield and selenium (Se) uptake by spring wheat (Triticum aestivum L.) was investigated in a pot experiment. Additionally, organic amendment (fugate, i.e. liquid by-product from the biogas plant) was applied to assess (i) the effect of organic matter on the bioavailability of Se and (ii) the fugate (containing 2.3 mg/kg of Se) as a potential source of Se for plants. Selenium was applied at two levels: 6.4 µg/kg (Se1) and 32 µg/kg (Se2) of soil. The efficiency of biofortification and the distribution of selenium within individual plant compartments were assessed in this case. The highest Se contents in the grain were achieved in the treatments receiving NPK fertiliser together with selenate, 455 µg/kg (Se1) and 2 721 µg/kg (Se2) when wheat was planted in Phaeozem. Fugate in co-application with selenate significantly reduced Se content in wheat plants as compared to treatments enriched solely with selenate. The lower Se contents in the wheat plants growing in Phaeozem were due to the biodilution effect, whereas in Cambisol, the decrease in wheat Se uptake was not clearly driven by a particular factor.

A review on factors influencing fog formation, classification, forecasting, detection and impacts.

With the changing climate and environment, the nature of fog has also changed and because of its impact on humans and other systems, study of fog becomes essential. Hence, the study of its controlling factors such as the characteristics of condensation nuclei, microphysics, air–surface interaction, moisture, heat fluxes and synoptic conditions also become crucial, along with research in the field of prediction and detection. The current review expands for the period between 1976 to 2021, however, especially focused on the research articles published in the last two decades. It considers 250 research papers/research letters, 24 review papers, four book chapters/manuals, five news articles, 15 reports, six conference papers and five other online readings. This review is a compilation of the pros and cons of the techniques used to determine the factors influencing fog formation, its classification, tools and techniques available for its detection and forecast. Some recent advanced are also discussed in this review: role of soil properties on fogs, application of microwave communication links in the detection of fog, new class of smog, and how the cognitive abilities of humans are affected by fog. Recently India and China are facing an emergence and repetitions of fog haze/smog and thus their policies initiatives are also briefly discussed. It is concluded that the complexity in fog forecasting is high due to multiple factors playing a role at multiple levels. Most of the researchers have worked upon the role of humidity, temperature, wind, and boundary layer to predict fogs. However, the role of global wind circulations, soil properties, and anthropogenic heat requires further investigations. Literature shows that fog is being harnessed to address water insecurity in various countries, however, coastal areas of Angola, Namibia and South Africa, Kenya, Eastern Yemen, Oman, China, India, Sri Lanka, Mexico, along with the mountainous regions of Peru, Chile, and Ecuador, are some of the potential sites that can benefit from the installation of fog water harvesting systems.

Effects of Soil Properties and Plant Diversity on Soil Microbial Community Composition and Diversity during Secondary Succession

Soil microbial communities play an important role in maintaining the ecosystem during forest secondary succession. However, the underlying mechanisms that drive change in soil microbial community structures during secondary succession remain poorly defined in species-rich subtropical coniferous forests. In this study, Illumina high-throughput sequencing was used to analyze the variations in soil microbial community structures during forest secondary succession in subtropical coniferous forests in China. The role of soil properties and plant diversity in affecting soil bacterial and fungal communities was determined using random forest and structural equation models. Highly variable soil microbial diversity was observed in different stages of secondary succession. Bacterial community diversity rose from early to middle and late successional stages, whereas fungal community diversity increased from early to middle successional stages and then declined in the late stage. The relative abundance of Acidobacteria, Gemmatimonadetes, Eremiobacterota(WPS-2), Rokubacteria, and Mortierellomycota increased during succession, whereas the relative abundance of Ascomycota and Mucoromycota decreased. The community composition and diversity of the soil microbial community were remarkably influenced by plant diversity and soil properties. Notably, tree species richness (TSR) displayed a significant and direct correlation to the composition and diversity of both bacterial and fungal communities. The carbon-to-nitrogen (C:N) ratio had a direct impact on the bacterial community composition and diversity, and pH had a marked impact on the fungal community composition and diversity. Furthermore, succession stage and plant diversity indirectly impacted the composition and diversity of soil bacterial and fungal communities via soil properties. Overall, it can be concluded that soil intrinsic properties and plant diversity might jointly drive the changes in soil microbial community composition and diversity during secondary succession of subtropical coniferous forests.

Mercury vertical and horizontal concentrations in agricultural soils of a historically contaminated site: Role of soil properties, chemical loading, and cultivated plant species in driving its mobility

The long term vertical and horizontal mobility of mercury (Hg) in soils of agricultural areas of a historically contaminated Italian National Relevance Site (SIN Brescia-Caffaro) was investigated. The contamination resulted from the continuous discharge of Hg in irrigation waters by an industrial plant (Caffaro S.p.A), equipped with a mercury-cell chlor-alkali process. The contamination levels with depth ranged from about 20 mg/kg dry weight (d.w.) of soil in the top (plow) layer to less than 0.1 mg/kg d.w. at 1 m depth. The concentrations varied also spatially, up to one order of magnitude within the same field and showing a decreasing trend from the Hg source (i.e., irrigation ditches). The concentration profiles and gradients measured were explained considering Hg loading, soil properties, such as the texture, organic carbon content, pH and cation exchange capacity. A Selective Sequential Extraction (SSE) was also applied on soil samples from an ad hoc greenhouse experiment to investigate the role of different plant species in influencing Hg speciation in soils. Although most of the extracted Hg was included in scarcely mobile or immobile forms, some plant species (i.e., alfalfa) showed to importantly increase the soluble and exchangeable fractions with respect to the unplanted control soils, thus affecting mobility and potential bioavailability of Hg.

Evaluating the potential of soil management to reduce the effect of Fusarium oxysporum f. sp. cubense in banana (Musa AAA)

Fusarium oxysporum f. sp. cubense (Foc) causes Fusarium wilt in banana (Musa AAA). Foc Race 1 devastated the subgroup Gros Michel during the first half of the twentieth century. The Gros Michel was largely replaced by the resistant subgroup Cavendish in the 1950s. However, in the 1980s, Foc Tropical Race 4 started to spread affecting Cavendish bananas. No proper control measures have been found to deal with the disease. This paper re-takes an important research line from the 1950s to evaluate the potential of soil management for Fusarium wilt management. The role of soil properties on Fusarium wilt in bananas was studied in two greenhouse experiments. It was evaluated whether the influence of two main soil properties (pH and N) on Fusarium wilt is similar for Race 1 and Tropical Race 4. Two soil pH levels (lower than 5.2 and higher than 6.0) respectively ensured through acidification and liming; and three levels of N (ammonium nitrate, 33.5% N) weekly doses (low:0 N g, medium: 0.08 N g and high: 0.25 N g per plant) were achieved. The first experiment in Costa Rica confirmed the earlier results about the influence of soil pH and nitrogen on Fusarium wilt (Race 1) on Gros Michel bananas. The second experiment in The Netherlands evaluated the influence of pH and N on interactions between Foc (both Race 1 and Tropical Race 4) and Cavendish bananas. Results in both experiments showed that soil pH affected crop development and the disease. Besides, the interaction of the lower pH x the higher N accelerated the infection and reduced plant development. As such, the results showed that soil management has the potential to reduce the impacts of Fusarium wilt while dealing with Race 1 and Tropical Race 4 although it requires confirmation and further evaluation under field conditions.

Contrasting responses of native and alien plant species to soil properties shed new light on the invasion of dune systems

Abstract Aims Among terrestrial ecosystems, coastal sandy dunes are particularly prone to alien plant invasion. Many studies related the invasion of dune habitats to anthropic causes, but less is known about the role of soil properties and plant traits in plant invasion. In this study, we tested the relationships between soil features and alien plant invasion in dune systems, focusing on the interplay between soil nutrients, soil salinity and plant functional traits. Methods Study sites were sandy barrier islands of the Marano and Grado lagoon (northern Adriatic Sea). One hundred plots (4 m × 4 m) were selected within 10 areas according to the main habitats occurring along the ecological gradient of dune system (foredune, backdune and saltmarsh). In each plot, we recorded all plant species occurrence and abundance and we collected a soil core. For each soil sample, soil texture, conductivity (as proxy of soil salinity), organic carbon and nitrogen content were analyzed and related to the species number and cover of native and alien plants. Variation of main reproductive and vegetative functional traits among habitats was also analyzed for both alien and native species. Important Findings Soil properties were strongly related to overall plant diversity, by differently affecting alien and native species pools. In backdune, the most invaded habitat, a high soil conductivity limited the number of alien species, whereas the content of soil organic carbon increased along with alien plant abundance, suggesting also the occurrence of potential feedback processes between plant invasion and soil. We found a significant convergence between native and alien plant functional trait spectra only in backdune habitat, where environmental conditions ameliorate and plant competition increases. Our findings suggest that in harsh conditions only native specialized plants can thrive while at intermediate conditions, soil properties gradient acts in synergy with plant traits to curb/facilitate alien plant richness.

PCB vertical and horizontal movement in agricultural soils of a highly contaminated site: Role of soil properties, cultivation history and PCB physico-chemical parameters

The agricultural areas of a historically contaminated National Relevance Site (SIN Brescia Caffaro) in Italy are an ideal case for studying the long term vertical and horizontal movement of polychlorinated biphenyls (PCBs) in soil. Here, a former large producer of PCBs (Caffaro S.p.A.) discharged its wastewaters, contaminated by PCBs and other chemicals, to a ditch used for about 80 years as source of irrigation waters for the adjacent agricultural areas. This caused a spread of contamination along both a vertical and a horizontal soil gradient. PCB concentrations of about 80 congeners, including PCB 209, peculiar of Caffaro production, were measured in three areas, selected for their different soil properties and cultivation history. The contamination levels with depth ranged from about 30 mg/kg dry weight (d.w.) of soil in the top (plow) layer to less than 0.1 mg/kg d.w. at the depth of 1 m. The concentrations varied also horizontally, since each field was surface irrigated from the short edge of each field, showing that PCBs could spread with length halving the initial concentrations in the topsoil only after about 30–35 m. The concentration gradients detected were explained considering the historic soil use and its change with time, the pedological properties as well as PCB physico-chemical parameters and halflives, developing equations which could be employed as guidance tools for evaluating PCBs (and similar chemicals) movement and direct further studies.

Streamflow Generation From Catchments of Contrasting Lithologies: The Role of Soil Properties, Topography, and Catchment Size

AbstractUnderstanding streamflow generation and its dependence on catchment characteristics requires large spatial data sets and is often limited by convoluted effects of multiple variables. Here we address this knowledge gap using data‐informed, physics‐based hydrologic modeling in two catchments with similar vegetation and climate but different lithology (Shale Hills [SH], shale, 0.08 km2, and Garner Run [GR], sandstone, 1.34 km2), which influences catchment topography and soil properties. The sandstone catchment, GR, is characterized by lower drainage density, extensive valley fill, and bouldery soils. We tested the hypothesis that the influence of topographic characteristics is more significant than that of soil properties and catchment size. Transferring calibration coefficients from the previously calibrated SH model to GR cannot reproduce monthly discharge until after incorporating measured boulder distribution at GR. Model calibration underscored the importance of soil properties (porosity, van Genuchten parameters, and boulder characteristics) in reproducing daily discharge. Virtual experiments were used to swap topography, soil properties, and catchment size one at a time to disentangle their influence. They showed that clayey SH soils led to high nonlinearity and threshold behavior. With the same soil and topography, changing from SH to GR size consistently increased dynamic water storage (Sd) from ~0.12 to ~0.17 m. All analyses accentuated the predominant control of soil properties, therefore rejecting the hypothesis. The results illustrate the use of physics‐based modeling for illuminating mechanisms and underscore the importance of subsurface characterization as we move toward hydrological prediction in ungauged basins.

Characterizing soils and the enduring nature of land uses around the Lake Chamo Basin in South-West Ethiopia

BackgroundCharacterizing and describing soils and land use and make a suggestion for sustainable utilization of land resources in the Ethiopian Rift valley flat plain areas of Lake Chamo Sub-Basin (CSB) are essential.ObjectivesTo (1) characterize soils of experimental area according to World Reference Base Legend and assess the nature and extent of salinity problems; (2) characterize land use systems and their role in soil properties; and (3) identify best land use practices used for both environmental management and improve agricultural productivity.MethodsTwelve randomly collected soil samples were prepared from the above land uses into 120 composites and analyzed.ResultsOrganic carbon (OC) and total nitrogen (TN) were varied along different land uses and depleted from the surface soils. The soil units include Chernozems (41.67%), Kastanozems (25%), Solonchaks (16.67%), and Cambisols (16.67%). The identified land uses are annual crops (AA), perennial crops (PA), and natural forest (NF). Generally, organic carbon, total nitrogen, percentage base saturation (PBS), exchangeable (potassium, calcium, and magnesium), available phosphorus (P2O5), manganese, copper, and iron contents were decreased in cultivated soils. Soil salinity problem was observed in annuals. Annuals have less nutrient content compared to perennials in irrigated agriculture while it is greater in annuals under rainfed. Clay, total nitrogen, available phosphorus, and available potassium (K2O) contents were correlated positively and highly significantly with organic carbon and electrical conductivity.ConclusionManagement practices that improve soil quality should be integrated with leguminous crops when the land is used for annual crops production.

Soil Texture Effects on Surface Resistance to Bare‐Soil Evaporation

AbstractModeling of surface energy balance and the separation of evapotranspiration to its component fluxes require quantification of evaporation from land surfaces. The nonlinear relationship between surface heat fluxes and the hydration state of soil surfaces present a challenge to remote estimation of surface evaporation rates. We study the often‐overlooked role of soil properties in determining surface evaporation resistance. We present a framework for quantifying how the ratio of actual to potential evaporation rates varies with changes in surface water content for different soil textures. The model uses the evaporative characteristic length (a soil‐dependent active depth of evaporation) and soil resistance to capillary flow across that region. Predictions were in good agreement with flux tower measurements of bare‐soil evaporation from 10 soil textural classes. The study offers a simple and physically based method for incorporating surface evaporation resistance into land‐surface models considering soil type and surface water content.

The role of soil volumetric liquid water content during snow gliding processes

In recent years, our understanding of snow gliding and glide-snow avalanches has improved; however, the contributing factors are still poorly understood and difficult to measure. In particular, the role of soil properties has not been considered as much as other environmental parameters (e.g. air temperature). Focusing on soil properties we established a monitoring site in the Italian Alps, in the release zone of a WSW-facing avalanche path. The area is typically characterized by intense snow gliding that results in the formation of large glide cracks, often leading to the release of a glide-snow avalanche. The site was equipped with four glide-snow shoes to measure snow gliding movement. Temperature and water content sensors were located at the snow-soil interface and at different depths within the soil. Meteorological data were recorded by a nearby automatic weather station, and snowpack properties were evaluated using manual snow profiles and SNOWPACK simulations; additionally, soils were characterized with special emphasis on the physical properties of the upper soil horizons. During two monitoring seasons, we registered a cold-temperature event characterized by gradual and continuous snow gliding and three warm-temperature events with glide-crack formation and evolution, in one case resulting in a glide-snow avalanche. Univariate (Mann-Witney U test) and multivariate (Classification Trees) analyses allowed us to find significant differences between gliding and non-gliding periods, and confirmed the importance of distinguishing between cold and warm-temperature events. In particular, for warm-temperature events we found that the most significant parameters were a large snow depth, strong settlement and high air temperature. For cold-temperature events we found that, together with a large snow depth, the volumetric liquid water content, both at the snow-soil interface and within the soil, played a fundamental role. Moreover, for the cold-temperature events we found a strong correlation between daily glide rates and the soil volumetric liquid water content, with an exponential relationship at the snow-soil interface and at 5cm depth within the soil. These results highlight the relationship between the snow gliding process and the soil conditions, which have been identified among the main environmental factors related to the development of snow gliding.

Role of soil properties in controlling the spatial variations of soil water content in varied fields

Role of soil properties in controlling the spatial variations of soil water content in varied fields

Finding partners in a habitat mosaic: Patch history and size mediate host colonization by arbuscular mycorrhizal fungi

AbstractRestoration of glades over the past 30 years, involving removal of woody cover and re‐establishment of herbaceous plant communities, has created an archipelago of habitat patches varying in age, size, and isolation. Within these glades, habitat varies in quality from edge to core. We investigated impacts of within‐ and among‐glade variation on the frequency of root colonization by arbuscular mycorrhizal fungi (AMF) for two host species, Schizachyrium scoparium and Rudbeckia missouriensis, and the plant community at large. We also conducted a soil analysis to explore the role of nutrient resources in mediating putative habitat effects. We used Akaike's information criterion (AIC) to evaluate a set of a priori models that assessed effects of glade size, isolation, age, and edge effects on AMF colonization. In community samples, AMF colonization increased while variation in AMF colonization decreased with restoration age. Edge effects also reduced plant community AMF colonization. AMF colonization was higher in R. missouriensis than in S. scoparium, but increased for both species in core habitat. Glade size had no direct effect on AMF at the plant scale, but indirectly affected overall AMF occupancy at the landscape scale via its geometric relationship to glade edge:core ratio. Hosts in small glades that are dominated by edge exhibit lower occupancy rates. The first two axes in a principal components analysis (PCA) combining soil nutrient variables explained 74% of sample variance: PC1 correlated positively with organic matter (OM), total nitrogen (N), calcium (Ca), magnesium (Mg), and potassium (K) and decreased from the edge to the core of older glades. PC2, which correlated positively with pH and negatively with available P, increased with time since restoration. While results are consistent with a role of soil properties in explaining edge and age effects, the two PCA dimensions themselves are weakly correlated with AMF colonization. Overall, our findings suggest that environmental filters associated with woody encroachment limit the colonization of otherwise suitable herbaceous hosts and create a landscape mosaic with larger, older glades serving as hotspots or reservoirs of AMF root colonization and smaller, newly restored glades as cold spots or potential sinks.

Role of Soil Properties and Precipitation Concentration in Enhancing Floods in Northern Ghana

Rainfall and soil inherent properties are natural factors that influence flood occurrence. The study assessed water infiltration rates and storage capacities of soils in the Northern and Upper East Regions of Ghana and their contribution floods. The objective was to assess the ability of the soil to absorb hydrological shock from floods and explore ecological tools that could be used to manipulate the soils of the regions to play flood reduction and mitigation roles. A field infiltration test was carried out and precipitation concentration index (PCI) was estimated for over a 30 year period. Soil bulk density was determined and porosity inferred. The PCI indicated that 100% of rainfall in Northern Region for 1977 - 2012 has been uniform in distribution and should not pose flood threat assuming rainfall is the only determinant. For the same period in the Upper East Region, 46% – 54 % of the rainfall distribution is indicative that could be succeptible to flash flood. Soil infiltration rates ranged between very slow and extremely infiltration classes (0.5 – 7 mm hr -1 ) and slow class (7.75 – 8.18 mm hr -1 ) for the Northern and Upper East regions respectively.. Soil bulk density ranged from 1.54 – 3.13 g cm -3 with porosity from 19 – 41% for Northern Region and 1.81 – 2.17 g cm‑ and 18 – 31 % for the Upper East Region. These accounts for the inability of the soil to carry the hydrological load during floods. Introduction of trees in combination of vetiver grass as an ecological tool could break and open-up the soil profile to allow more water intake and mitigate flood damage. Keywords: Ghana, soil hydrological load, ecological tool, flood mitigation, soil water intake.

Soil pipe collapses in a loess pasture of Goodwin Creek watershed, Mississippi: role of soil properties and past land use

AbstractLittle is known about the association of soil pipe collapse features with soil properties or land use history. Three loess covered catchments in northern Mississippi, USA were characterized to investigate these relationships. Soil pipe collapses were characterized for their size, type feature and spatial location along with soil properties across the three catchments. Although mapped as the same soil, one of the catchments did not contain pipe collapse features while the other two had 29.4 and 15.4 pipe collapses per hectare. These loess soils contained fragipan layers that are suspected of perching water, thereby initiating the piping processes. Pipe collapses associated with subsurface flow paths were not always consistent with surface topography. The surface layer tended to be non‐erodible while layers below, even the upper fragipan layers, were susceptible to erosion by pipeflow. Soil properties of the lowest fragipan layer were highly variable but tended to prevent further downward erosion of soil pipes and thus formed a lower boundary for gullies. Middle to lower landscape positions in one of the piped catchments contained anthropic soils that were highly erodible. These anthropic soils were previously gullies that were filled‐in in the 1950s when forested areas, assumed to have been established when land was previously converted from crop to forest land, were converted to pasture. Three decades after this land use change from forest to pasture, pipe collapses became evident. In contrast, the adjacent catchment that does not exhibit pipe collapse features experienced severe sheet and rill erosion prior to the 1930s while in cotton production. The surface horizons above the lower fragipan layer were completely removed during this period, thus the top‐soil layer that tends to form a bridge above soil pipes in the more erodible subsoil layers was removed. This study showed that knowledge of soil characteristics or topography alone do not explain the distribution of soil pipe collapses as past land use can play a definitive role. Copyright © 2015 John Wiley &amp; Sons, Ltd.