Related Soil Properties Research Articles

Soil zinc surveillance frameworks can inform human nutrition studies: opportunities in India

Mineral micronutrient deficiencies are widespread in global food systems and can affect plant growth, crop quality, and human and livestock health. The mapping of soils and soil properties linked to micronutrient supply in food systems is now enabling us to better understand the linkages between soil health and function and its relationship with food quality and human health. Zinc (Zn) deficiencies in Indian soils are of particular concern in the context of crop yields and food quality. This current review aims to understand the data landscapes on soil Zn and related soil properties in India, with a particular focus on three states: Uttar Pradesh (UP), Bihar, and Odisha. The scope of the review is to identify and describe data sets from national and state-wide programmes and research experiments in which soil Zn has been reported, which could be used to provide a framework for integrated surveys and would combine wider agriculture, food systems, nutrition, and public health sectors. The largest data set on soil Zn was collected under a soil health management (SHM) programme, during which the Indian government analysed more than 30 million soil samples for Zn concentration (mg/kg) from 2015 to 2019. This study showed that 39% of Indian soils are considered Zn deficient for crop production (i.e., based on a threshold of <0.6 mg/kg); soil Zn deficiency varied from 2% to 67% across different Indian states. From this survey, soil Zn deficiency was 29%, 67%, and 48% in UP, Bihar, and Odisha, respectively. Individual data points are available for re-use at the Government of India soil health card website (https://www.soilhealth.dac.gov.in/). In addition, the All India Coordinated Research Project on Micro and Secondary Nutrients and Pollutant Elements in Soils and Plants (AICRP-MSPE) programme under the Indian Council of Agricultural Research (ICAR) analysed >240,000 soil samples from 2012 to 2018 from 28 states of India and reported ~38% soil Zn deficiency in the Indian soils. There is no programme in India that currently maps micronutrients in soil and crops together using “GeoNutrition” approaches recently reported in two countries in Africa, Ethiopia, and Malawi. Future co-ordinated soil and crop micronutrient mapping in India can help us to understand better the movement of Zn (and other micronutrients) in food systems and to inform strategies to improve the Zn status in the soil, e.g., the use of Zn fertilisers for yield and agronomic biofortification, and in the edible tissues of crops, e.g., through genetic biofortification.

Impacts of Biochar and Gypsum on Ammonia-Oxidizing Microorganisms in Coastal Saline Soil

Nitrification is the core step of the soil nitrogen cycle and directly affects the nitrogen use efficiency in agricultural systems. Biochar and gypsum are two important soil amendments widely used in coastal saline farmland. However, little is known about their effects on nitrification and ammonia-oxidizing microorganisms. A one-year pot experiment with three treatments including biochar application (BC), gypsum application (SG), and no amendment (CK) was conducted, and the responses of the nitrification rate, amoA gene copies, and the diversity and community structure of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to biochar and gypsum were evaluated. The results indicated that biochar and gypsum application both resulted in alterations to the soil properties. They both had inhibiting effects on nitrification and AOB amoA gene copies, whereas they had no significant effect on AOA amoA gene copies. Biochar had no significant effect on the diversity indexes of AOA, but it significantly reduced the Shannon index of AOB. Meanwhile, gypsum had no significant influence on the diversity indexes of both AOA and AOB. Biochar and gypsum did not significantly affect the community structure of AOA but did induce changes in that of AOB. In detail, biochar significantly enhanced the relative abundance of the dominant cluster Nitrosospira, whereas gypsum led to a notable increase in the relative abundance of unclassified_o_Nitrosomonadales. The Shannon index of AOB had a significant negative correlation with soil TOC, TN, and NH4+ content, and soil pH was the first primary environmental factor that affected the AOB community structure. In conclusion, biochar and gypsum inhibited nitrification by suppressing the activities of AOB and changed the diversities and community structure of AOB by altering related soil properties.

Soil organic carbon sequestration under Araucaria angustifolia plantations but not under exotic tree species on a mountain range

ABSTRACT Plantation forests can be efficient C sinks in biomass and soil organic carbon (SOC), but the latter depends on many factors, including climate. Tropical humid, mountain areas have cooler temperatures, slowing microbial decomposition, and thus can store considerable SOC. However, the effects of forest plantations on SOC of these montane areas are still poorly studied. Here, we aimed to assess changes in SOC, and related soil properties, after conversion of native rainforest to plantations of five tree species, with rotation cycles varying from 7 to 30 years, on the Mantiqueira Range, Minas Gerais, Brazil. We measured SOC contents and stocks (0.00-0.40 m layer) under a native montane rainforest (control) and plantations of Eucalyptus, Pinus, Cunninghamia, Cupressus and Araucaria, all planted in 3 × 3 m spacing, at an altitude of ca. 1,300 m, marked by humid and cool climate, where SOC contents are naturally high. Soil organic carbon varied from 55 g kg -1 under Eucalyptus to 105 g kg -1 under Araucaria (0.00-0.05 m layer), decreasing in depth (0.20-0.40 m) to the still high values of 20-40 g kg -1 . Soil organic carbon stocks for the top 0.20 m were also high, reaching ca. 140 Mg ha -1 under Araucaria, significantly higher value than the native forest (ca. 90 Mg ha -1 , p<0.05), which did not differ from the other species. Soil organic carbon stocks were not affected in the 0.20-0.40 m soil layer, whereas soil structure patterns changed under some species, without however resulting in bulk density changes, and pH decreased under Araucaria. Such data showed large SOC stocks under montane native forests can not only be preserved upon conversion to forest plantations, but considerable SOC sequestration can be achieved in 30-years rotation cycles plantations of indigenous Araucaria angustifolia, marked by more open canopies and greater understory biomass.

Investigating soil properties on the north and south slopes at different elevations in Al-Jabal Al-Akhdar, Libya

This scholarly study investigated the physicochemical characteristics of soil in the Al-Jabal Al-Akhdar forest, Libya, with a specific focus on the influence of elevation and slope aspects. Fifty-six sample plots were established across varying elevations, each subdivided into four subplots, totaling 224. Soil samples were collected from each subplot at 0-15 cm depth. Results demonstrate significant variations in clay, silt, and sand content with elevation, indicating lower clay and higher sand content at higher elevations. Available water capacity (AWC) increased with altitude on the northern slope, while consistently lower values were observed on the southern slope. Bulk density (BD) decreased with increasing altitude, suggesting less compacted soils at higher elevations. Available phosphorus (Pav), available potassium (Kav), and pH values decreased with increasing altitude on both slopes. Cation exchange capacity (CEC) values varied at altitudes on the northern slope, with higher values observed at mid to high altitudes. Calcium carbonate (CaCO3) decreased with increasing altitude on the northern slope while showing inconsistent trends on the southern slope. Soil organic matter (SOM) content increased with altitude on both slopes. Pearson's correlation and Principal Component Analysis (PCA) examined relationships among soil properties, elevations, and aspects. Elevation positively correlated with AWC and SOM and negatively correlated with clay content, Kav, BD, and pH. PCA identified elevation, aspect, silt content, CaCO3, and electrical conductivity (EC) as primary influencers. SOM exhibited positive correlations with AWC and negative correlations with BD. Soil pH showed a negative correlation with SOM and a positive correlation with CaCO3. Additionally, CaCO3 content was positively correlated with the cation exchange capacity (CEC). These findings contribute to understanding soil property relationships, elevation, and aspect, emphasizing their role in shaping soil ecosystems and nutrient dynamics. Further research is warranted to explore additional factors influencing soil properties and to develop effective nutrient management strategies.

Effect of vegetation restoration type and topography on soil water storage and infiltration capacity in the Loess Plateau, China

Vegetation restoration effectively mitigates soil erosion and improves soil properties, but in drylands, it can lead to soil water scarcity and disrupt ecological balance. Until now, limited research has examined the combined effects of vegetation restoration type and topography on soil water and infiltration in the Loess Plateau of China. Here, we investigated soil water content (SWC), soil water storage (SWS), soil infiltration rates and related soil properties in typical forestland, shrubland, and grassland across five slope positions on steep slopes, and compared them with cropland. The results indicated that vegetation restoration significantly decreased SWS compared to cropland. Across the entire 0–500 cm depth, reductions were observed at 30.9 %, 33.2 %, and 20.8 % for forestland, shrubland, and grassland, respectively, with forestland and shrubland demonstrating a more pronounced decrease, particularly in deeper soil layers. Shrubland had the lowest SWS on the upper, middle, and top slopes, while forestland showed the lowest SWS on the lower and foot slopes. In terms of infiltration, vegetation restoration generally increased steady infiltration rate but resulted in reduced initial and mean infiltration rates (except for shrubland). Shrubland had the highest infiltration rates, followed by forestland, while grassland had the lowest rates. Soil infiltration rates decreased gradually along the slope, indicating that the impact of vegetation restoration on soil infiltration improvement weakened with lower slope positions. Vegetation restoration type had a stronger direct and total effects on infiltration than slope position. Yet, the indirect influence of slope position through clay content and SWC outweighed that of vegetation restoration type. Our findings highlight the comprehensive assessment of the eco-hydrological effects of vegetation restoration is essential for identifying suitable species and designing optimal spatial distribution, ultimately maximizing the ecological benefits of the restoration. These insights can offer valuable guidance for ecological restoration and land management in fragile dryland ecosystems.

Experimental Data on Maximum Swelling Pressure of Clayey Soils and Related Soil Properties

Clayey soils exhibit significant volumetric changes in response to variations in water content. The swelling pressure of clayey soils is a critical parameter for evaluating the stability and performance of structures built on them, facilitating the development of appropriate design methodologies and mitigation strategies to ensure their long-term integrity and safety. We present a dataset comprising maximum swelling pressure values from 759 compacted soil samples, compiled from 16 articles published between 1994 and 2022. The dataset is classified into two main groups: 463 samples of natural clays and 296 samples of bentonite and bentonite mixtures, providing data on various types of soils and their properties. Different swelling test methods, including zero swelling, swell consolidation, restrained swell, double oedometer, free swelling, constant volume oedometer, UPC isochoric cell, isochoric oedometer and consolidometer, were employed to measure the maximum swelling pressure. The comprehensive nature of the dataset enhances its applicability for geotechnical projects. The dataset is a valuable resource for understanding the complex interactions between soil properties and swelling behavior, contributing to advancements in soil mechanics and geotechnical engineering.

Assessment of Selected Physical and Chemical Soil Properties and Organic Carbon Stock, Under Different Land-Uses in Melka Gura Subwatershed of North Shewa Zone, Oromia, Ethiopia

A study conducted in Melka Gura Subwatershed to assess soil properties across three types of land uses plantation forest, grazing land, and cultivated land from 2022 to 2023 found that all land uses had loam soil, except for the plantation forest, which had sandy loam. The mean soil BD in the study area ranged from 1.06 to 1.39 g/cm3. Conversely, plantation forest soil and grazing land had the highest mean AWC (194.8 mm/m) at 0–20 cm depth. The highest mean values of sand, silt, TP, pH, AP, exchangeable basic cations, CEC, SOC, TN, and SOC stock (68.62-ton ha-1) were registered in the soil of plantation forest land. The highest mean values of BD (1.39 g/cm3), clay content (19%), Ex. A, and Ex. Al were recorded in the soil of cultivated land. The average values of clay, BD, FC, PWP, pH, PBS, and exchangeable bases all indicated an increasing trend from the surface toward the subsurface. The highest mean value of SOCS (68.62 tons’ ha-1) was discovered in plantation forest land and the lowest in cultivated land. The differences in soil management practices could be the major reasons for variations in soil properties across land-use types. Further studies are needed on the effects of land-use change on fertility-related soil properties in relation to integrated soil and water conservation practices to reduce further land degradation.

Physical Properties of Soil in Relation to Saturated Hydraulic Conductivity of Soils Under Selected Land Use Practices in Akwa Ibom State

This study assessed the effects of land use types on selected physical properties of soil in Akwa Ibom State, south-south Nigeria. Four land use types, intensive cultivated land (ICL), natural forest (NF), oil palm plantation (OPP) and gmelina plantation (GP), were considered. Each land use was represented by three profile pits which were sampled according to genetic horizons for laboratory analysis. Data generated were analyzed statistically using descriptive and regression analyses. The results showed that ICL had the highest bulk density (Bd) ( 1.7g/cm3) followed by NF and OPP (1.6g/cm3) while GP had the least (1.5g/cm3), OPP had the highest total porosity (Tp) (43.7%) followed by GP (42.6%), NF (41.1%) while ICL had the least (36.2%), ICL and NF had the highest water stable aggregates (WSA) (12.9%) followed by OPP (8.3%) while GP had the least (4.3%). However, OPP had the highest saturated hydraulic conductivity (Ksat) (8.4cm/h) followed by NF (8.2cm/h) while ICL and GP had the least (4.3cm/h). Result further showed that Ksat was significantly correlated with clay with r2 value of 0.53 (Ƿ˂ 0.01). Across the four land use types, Ksat was moderately rapid. Irrespective of land use type, soils were dominated by sand-sized fraction which generally decreased with depth, reflecting the influence of the parent material(coastal plain sands). This study shows that the land use types were similar in their effects on Ksat but there were no significant differences.

Soil water storage capacity and soil nutrients drive tree ring growth of six European tree species across a steep environmental gradient

Tree growth depends on tree-intrinsic attributes, synecological interactions, atmospheric conditions and soil properties. While the influence of tree factors and climate are analysed in detail in many studies, the effect of soil properties is less investigated and compensatory soil effects are often not quantified. In this study, we use a comprehensive dataset of 1659 tree increment cores from six common Central European tree species (Abies alba, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus spp.) sampled at 1562 locations across large environmental gradients in the Eastern Alps. Soil data was available from an extensive soil survey including soil pits, laboratory analysis and the application of pedotransfer-functions. Up to three main tree species per site were sampled and the tree ring widths were dendrochronologically measured and synchronized. Topographic information from a high-resolution Digital Terrain Model, high-resolution climate data and biometric measures were available at each site. To determine the influence of soil water storage capacity and soil nutrient status, we used generalized additive models to expand standard models of well-known drivers of tree growth, including age, climatic water balance and temperature. For the time span of 38 years from 1981 until 2018, we found species-specific impacts of soil properties on tree ring growth. Specifically, soil water storage acted as a buffer to overcome drought periods, in particular for deep rooting tree species like Quercus spp. and Abies alba. In addition, we found species-specific growth reactions to soil nutrient status for nutrient-demanding species likes Fagus sylvatica but no effects for less demanding tree species like Pinus sylvestris. Our results show the magnitude of the effects of soil properties in relation to other growth factors on radial growth of six Central European tree species. Therefore, we posit that, while age and climate do have a stronger influence on tree growth, it is important to consider soil as a growth factor, particularly at the distribution margins along climatic gradients.

Repeated Solid Digestate Amendment Increases Denitrifying Enzyme Activity in an Acid Clayey Soil

The use of organic fertilizers to replace chemically synthesized fertilizers has assumed an important role in managing plant nutrition and soil fertility. The various organic matrices currently available as organic byproducts and digestates are relatively abundant and have shown promising effects in terms of plant-available nutrients. However, like mineral fertilizers, organic fertilizers must be carefully managed to avoid negative effects on the environment, especially when they are repeatedly applied over time. The aim of the present study was to assess the effect of the single (DIG) and repeated application (DIGP) of solid anaerobic digestates compared to an unamended control (CTR) on the denitrifying enzymatic activity (DEA), which is responsible for nitrous oxide emissions into the atmosphere, and some related soil properties, such as total soluble nitrogen (TSN), nitrate (NO3−-N), extractable carbon (Cextr), microbial biomass carbon (MBC), and basal respiration (Rbas), for a period of ~3 months after application. The application of solid anaerobic digestates progressively boosts N and C concentrations in the soil, with the degree of enhancement directly correlated with the frequency of application over the sampling period. Depending on the textural properties of soils, there was a notable rise in denitrification enzyme activity (DEA), particularly during the DIGP treatment, suggesting that clay soils are highly susceptible to denitrification under suitable conditions. The results of this study recommend the careful management of soils subjected to repeated digestate amendment to prevent the occurrence of conditions conducive to denitrification and the promotion of N2O emissions.

Variation in the physical properties of soil in relation to natural and anthropogenic factors in the hilly loess region of China

Soil particle size distribution (PSD), bulk density (BD), saturated hydraulic conductivity (Ks), soil water content (SWC) and generalized soil structure index (GSSI) are key physical properties for vegetation growth and are easily affected by natural and anthropogenic factors. However, how these soil physical properties respond to land use, slope aspect, slope position, and their interactions are less clearly understood. Here, an experiment with three land uses (cropland, grassland, and black locust [Robinia pseudoacacia L.] forests after 4, 9, 15, and 19 years of restoration), two slope aspects (south and north slope) and two slope positions (up and down slope) were conducted in the hilly loess region of China. The results showed the following: (1) The variation in different physical properties were driven by different factors of land use, slope aspect, slope position and their interactions. (2) The 9, 15 and 19 year old locust forests significantly decreased the BD by 6.75 %–19.32 % and increased the Ks by 69.96 %–195.97 % compared with grassland, while the cropland had higher SWC and GSSI values than the grassland and locust forests. (3) Soil physical properties were higher on the north slope than on the south slope and were larger on the down slope than on the up slope. (4) The BD, Ks, SWC, and GSSI of locust forests displayed different changes with the restoration year. (5) The key factor affecting forest growth and soil quality improvement varied with forest ages. Overall, 19 year old locust was the most effective at improving the BD and Ks. Furthermore, slope aspect, slope position and restoration time should be considered when evaluating the response of physical properties to land uses.

Importance of soil fertility for climate-resilient cropping systems: The farmer's perspective

Healthy and productive agricultural soils are the basis for global food security as they are a prerequisite for yield-stable cropping systems under climate change. Despite the expansion of agricultural research activities in this area through field experiments, lab analyses, and modelling frameworks, current empirical insights from farming practice on a more national scale are still rare. For this reason, the agronomic importance of soil fertility for farming practice was the focus of this nationwide empirical study conducted in Germany (winter/spring 2022) with a total sample size of 585. The views and needs of 370 farmers and 215 agricultural institutionalists were evaluated, i.a., regarding the importance of soil fertility and related soil properties, as well as preferred agronomic management strategies and needs for the promotion of soil fertility. The results showed that most farmers and institutionalists consider soil fertility to be very important. Moreover, it was emphasized that the importance of this factor will increase in the future due to changing climatic conditions (e.g., heat/drought stress) and the need for more sustainable land use including the protection of biodiversity. The main motivations for agronomic investments in greater soil fertility were improving the climate resilience and yield stability of cropping systems. In this context, the top soil properties of interest were ranked by the respondents as follows: (1) water storage capacity, (2) rootability, (3) biological activity, and (4) water infiltration rate. To promote soil fertility, farmers mainly considered catch cropping, diversified crop rotations with a positive humus balance, and year-round ground plant cover/mulch as the most useful agronomic measures. In terms of methods for the assessment of soil fertility, soil structure analyses, biological indicators, yield/biomass production, soil nutrient analyses, and field methods were most important, whereas sensor systems and apps/digital tools were of minor importance. For the future improvement of soil fertility promotion in farming practice, simple indicators and reference values for assessing soil fertility as well as 'workshops, field days, and field schools' for training aspects were suggested by the participants. Overall, there were few differences between the perceptions of farmers and agricultural institutionalists. Both groups pointed out the need for improved communication between politics, science, and practice such that agriculture can respond more quickly to changing climatic conditions in the future.

Relating soil properties to soil losses by wind erosion in a cultivated organic soil in the southwest of Quebec, Canada

Cultivated organic soils are known to be highly susceptible to wind erosion. The aim of this research was to explore the relationships between organic soil properties and measured soil height variation (SHV) in a cultivated organic soil and to analyze field soil erodibility (wind erodibility index: WEI) from known models. In the fall, 81 georeferenced soil samples were collected at a depth of 0–10 cm and analyzed in the laboratory to determine different soil properties. At the same time, soil height variations were measured over a 35-day period. Simple and multiple linear regressions were used to explore relationships between soil properties and analyze SHV and WEI. The average SHV across the farm was −0.19 mm per day, equivalent to a loss of 0.665 cm during the measurement period. Simple linear regression showed weak relationships with SHV. Nevertheless, the analysis showed that soil loss areas had a larger fraction of macro-aggregates. Conversely, deposition areas with low bulk density (BD) contained more fine material (organic matter [OM] and erodible material [EM]), suggesting wind erosion effects, i.e., deposition of fine matter. Many soil properties were found to correlate significantly with one another. Applying multiple linear regression with SHV and WEI as dependent variables and soil properties as independent variables produced the following results: a) 24% of the SHV was significantly explained by 6 soil properties (α=5%,p=0.001), BD, EM, mean weight diameter (MWD), elevation (Z), geometric mean diameter (GMD), and volumetric water (VW); and b) 75% of the variation in WEI was explained by 5 variables (α=5%,p=0.001), BD, VW, OM, MWD and GMD. This result shows that BD, VW, OM, MWD, EM, GMD, elevation Z are key soil properties in sustainable management of organic soil with >80% OM and will be used in a wind erosion risk model adapted to organic soils.

Acidification suppresses the natural capacity of soil microbiome to fight pathogenic Fusarium infections

Soil-borne pathogens pose a major threat to food production worldwide, particularly under global change and with growing populations. Yet, we still know very little about how the soil microbiome regulates the abundance of soil pathogens and their impact on plant health. Here we combined field surveys with experiments to investigate the relationships of soil properties and the structure and function of the soil microbiome with contrasting plant health outcomes. We find that soil acidification largely impacts bacterial communities and reduces the capacity of soils to combat fungal pathogens. In vitro assays with microbiomes from acidified soils further highlight a declined ability to suppress Fusarium, a globally important plant pathogen. Similarly, when we inoculate healthy plants with an acidified soil microbiome, we show a greatly reduced capacity to prevent pathogen invasion. Finally, metagenome sequencing of the soil microbiome and untargeted metabolomics reveals a down regulation of genes associated with the synthesis of sulfur compounds and reduction of key traits related to sulfur metabolism in acidic soils. Our findings suggest that changes in the soil microbiome and disruption of specific microbial processes induced by soil acidification can play a critical role for plant health.

Carbon sequestration potential and fractionation in soils after conversion of cultivated land to hedgerows

Hedgerows supply multiple ecosystem services in agricultural landscapes and have been advocated to provide a relevant carbon sink for climate change mitigation. Using a space-for-time approach, we investigated carbon sequestration and fractionation in soils beneath hedgerows 1 to 70 yr after planting on cultivated land in the humid continental climate of Eastern Austria. We sampled 54 pairs of hedgerow and adjacent cultivated soil volumetrically to 40 cm depth and analysed them for bulk soil (< 2 mm) mass, SOC fractions of differential stability and related soil properties. Total SOC stocks to 40 cm depth increased significantly (p < 0.05) by 34.7 ± 4.70 Mg C ha−1 to 119 ± 6.77 Mg C ha−1 beneath 31–70 yr old hedgerows, and by 15.6 ± 5.94 Mg C ha−1 to 106 ± 8.98 Mg C ha−1 beneath 1–30 yr old hedgerows. Carbon sequestration was limited to the organic and mineral topsoil layer (0–20 cm), SOC changes (ΔSOC) at 20–40 cm depth were small and insignificant (p < 0.05). Linear regression of ΔSOC on hedgerow age (1–70 yr) yields a mean SOC sequestration rate of 0.65 ± 0.10 Mg ha−1 yr−1 down to 40 cm depth. Combining our data with published work we found hedgerow age explaining ∼65 % of the variation of ΔSOC in topsoils, and ∼68 % in shallow subsoils; ΔSOC increases with hedgerow age in topsoils, but declines in subsoils. Annual sequestration rates decline with hedgerow age in both soil layers. Up to 30 years after conversion, SOC is preferably sequestered in labile particulate organic matter (POM; > 20 µm), and stabilised in the mineral-associated organic matter (MAOM; < 20 µm fraction) thereafter. In the bulk soil and MAOM fraction, SOC strongly increases with oxalate-extractable Al (Alo). We conclude that SOC sequestration beneath hedgerows offers a relevant CO2 sequestration potential which is mainly limited to topsoils and primarily controlled by hedgerow age and Alo.

Spatial variations in ectomycorrhizal fungi and host tree reciprocal relations are associated with the local distribution patterns of Minjiang fir

Ectomycorrhizal fungi (ECMF) can help maintain the natural range of host trees by assisting their occupancy in the boundary of distribution. However, it is unclear whether the boundary-dependent variations in ECMF communities and their relationships with hosts are associated with the patterns of local-scale host tree distributions. In this study, we investigated the community structure of ECMF in the root tips of the Minjiang fir (Abies fargesii var. faxoniana) saplings, and examined the variations in root-associated ECMF communities and their relationships with the fir saplings along environmental gradients from the centric suitable habitats (SH) on shady slopes to range boundaries (RB) at the upper and lower elevations of the SH and on sunny slopes. We found that both the SH and the upper RB were enriched by the ECMF taxa in the genus Cortinarius, which were positively correlated with the basal diameter (BD) of the firs. In contrast, the lower RB of the shady slopes and the sunny slopes harbored a higher abundance of the ECMF taxa in the genus Tylospora, which were negatively correlated with the BD of the firs. The relationships between the firs and some of the same ECMF species, such as Cortinarius balaustinus and Cortinarius casimiri, shifted from positive at the SH to negative at the lower RB of the shady slopes and on sunny slopes. Soil properties differed between habitat types, so do the relationships of soil properties with ECMF communities. These marginal alterations in ECMF communities and their relationships with the fir saplings were not explainable by changes in soils. Our study highlighted habitat-dependent shifts in root-associated ECMF communities and their correlations with Minjiang fir saplings from suitable habitats to range boundaries. The results suggest that these marginal patterns may be associated with variations in habitats rather than current soil properties for Minjiang firs. The spatial variations in ECMF communities and their relationships with fir saplings could be useful indicators for identification of the site suitability for Minjiang fir regeneration and conservation.

Soil reconstruction and heavy metal pollution risk in reclaimed cultivated land with coal gangue filling in mining areas

Coal gangue filling reclamation is an important means to restore coal mining subsided cultivated land. However, coal gangue can release heavy metals, threatening the overlying soil environment. During the reconstruction of reclaimed mine soils (RMSs), soil properties evolve in a complex manner and influence the distribution of heavy metals, forming complex network relationships that differ from those of non-subsided cultivated soils (NCSs). It is difficult to determine the mechanism of RMS reconstruction and heavy metal accumulation and distribution by studying the trends of only a few variables. Complex network theory (CNT), however, can reveal the original internal characteristics and mechanisms of the system in a comprehensive and effective way. This study aimed at revealing the characteristics and mechanisms of soil reconstruction and heavy metal distribution in RMSs from a holistic perspective. Reclaimed cultivated land with coal gangue filling in high-groundwater-level mining areas in Jining City, Shandong Province, China, was selected for the study. First, soil samples were collected from depths of 0–20, 20–40, and 40–60 cm, and a total of 21 soil indicators were determined. Then, CNT was applied to explore the special soil property relationships and key factors in the RMS reconstruction process. Finally, the intrinsic mechanism of RMS reconstruction and heavy metal distribution was revealed by comparison with NCSs. The results showed that coal gangue filling reclamation and reconstruction activities led to increases in bulk density (BD), decreases in nutrients, and the accumulation of heavy metals. These activities also changed the relationship strength and cooperation efficiency among soil properties. BD reduction due to soil aggregate recovery increased microbial activity and accumulated organic carbon and nutrients, which became essential for RMS recovery. The filled coal gangue became a new source of heavy metals for the RMSs, with water-dissolved colloids acting as carriers of the heavy metals.

Analysis of Selected Soil Properties in Relation to Soil and Water Conservation Practices in Sibiya Arera, Soro District, South Central Ethiopia.

Soil erosion by water is a severe and continuous ecological problem in the south central highlands of Ethiopia. Limited use of soil and water conservation technologies by farmers is one of the major causes that have resulted in accelerated soil erosion. Within this context, significant attention has been given to soil and water conservation practices. This study was conducted to investigate the effects of soil and water conservation practices on soil physicochemical properties after being practiced continuously for up to 10 years. The physicochemical properties of soil of landscape with physical soil and water conservation structures without biological conservation measures and physical soil and water conservation structures combined with biological conservation measures were compared with soil of landscape without soil and water conservation practices. The result of analysis disclosed that soil and water conservation interventions (both with biological and without biological measures) significantly increased the soil pH, soil organic carbon, total nitrogen, and available phosphorus content than the soil of landscape without soil and water conservation practices. The results of the analysis also showed that the mean value of cation exchange capacity and exchangeable bases (K+, Na+, Ca2 +, and Mg2 +) of the soil under nonconserved farm field was significantly lower as compared to the soil of adequately managed farm fields. The findings of this study clarified that there was significant variation in soil properties. This variation could be due to uneven transport of soil particles by runoff. Therefore, soil conservation structures supported with biological measures improves the soil's physicochemical properties.

Environmental heterogeneity increases the conservation value of small natural features in karst landscapes

Local biodiversity hotspots are often located within regions where extreme and variable environmental – e.g., climatic and soil – conditions occur. These areas are conservation priorities. Although environmental heterogeneity is recognised as an important determinant of biodiversity, studies focusing on the effects of multiple environmental heterogeneity components in the same ecosystem are scarce. Here we investigate how topography and related microclimatic variables and soil properties may influence the biodiversity and conservation value of karst landscapes. Karst landscapes of the world contain millions of dolines (i.e. bowl- or funnel-shaped depressions) that may function as ‘small natural features’ with a disproportionately large role in maintaining biodiversity relative to their size. We assessed the diversity of microclimates, soils and vegetation and their relationships in six microhabitats (south-facing slopes, east-facing slopes, west-facing slopes, north-facing slopes and bottoms of dolines, and the adjacent plateau) for nine large dolines in a grassland ecosystem. Although there were remarkable differences among the conservation value of these microhabitats (e.g., representation of different species groups, presence of ‘climate relicts’), each microhabitat had an important role in maintaining species that are rare or absent in other microhabitats in the landscape. We found that the studied dolines exhibited highly variable environmental conditions and promoted a high diversity of vegetation types with unique species composition, contributing to the topographic, climatic, soil, vegetation and land cover heterogeneity of karst landscapes. Therefore, our findings highlight that dolines may function as local biodiversity hotspots and have a crucial conservation importance. As dolines are widespread topographic features in many karst landscapes throughout the world, our results could be directly applied to other regions as well. An integrated approach is urgently needed to provide guidelines for landscape management, promoting the retention of the microhabitat diversity of small natural features for species vulnerable to climate change and/or various disturbances.

Variation in Soil Aggregate Stability Due to Land Use Changes from Alpine Grassland in a High-Altitude Watershed

Land use change affects soil aggregate composition and stability, which impacts soil structure and health. To reveal how land use change impacted soil aggregates of alpine grassland in a high-altitude watershed, soil samples from 161 sites including alpine grassland, cropland and abandoned land were selected to measure and analyze the distribution of aggregate fractions (macro-aggregates, micro-aggregates, silt+clay), soil aggregate stability (mean weight diameter, geometric mean diameter, fractal dimension, etc.) and related soil properties (soil organic carbon content, soil particle composition, etc.) in the Huangshui River watershed of the Qinghai–Tibet Plateau. The results showed: (1) As alpine grasslands were converted to croplands and croplands to abandoned lands, the proportion of macro-aggregates and the aggregate stability index showed a trend of first decreasing and then increasing (p &lt; 0.05), indicating that tillage and abandonment have significant influences on soil aggregate structure. (2) Compared with temperate grassland, alpine grassland had richer soil organic carbon, and a higher ratio of macro-aggregates and aggregate stability. (3) Soil organic carbon and sand content had distinct influences on the fractions and stability of aggregates during land use change. These results suggested that cultivation can substantially reduce the soil aggregate stability in alpine grassland, whereas abandonment can effectively improve soil aggregate structure.