Purpose

Sulfonamides are widely used for the prevention and treatment of bacterial infections, hard-degraded contaminants distributed in the environment if they are discharged into the soil and water. Biochar could probably influence the geochemical behavior of ionized antibiotics in the soils.

Materials and methods

To determine the sorption/desorption of three representative sulfonamides (SAs) in soils amended with biochar, we investigated the effects of water pH, Cu²⁺, and dissolved humic acid on the sorption of sulfamethoxazole (SMX), sulfamethazine (SMZ), and sulfadiazine (SD) onto two different soil samples (S1 pH?=?5.13 and S2 pH?=?7.33) amended with wheat straw-derived biochar (size 0.5～0.6 mm).

Results and discussion

Batch experiments showed that the sorption/desorption isotherms of SAs on soil with/without biochar followed the Freundlich model. The biochar had a strong adsorption potential for SMX, SMZ, and SD both in S1 and S2 at low water pH. Except for SMX, the presence of Cu²⁺ inhibited the sorption of SMZ and SD through competing hydrophobic adsorption region in soils. HA suppressed the sorption of three sulfonamides in soil S2 by electrostatic repulsion under alkaline condition. The soil leaching column experiments showed the SA transport in soils, and S1 and S2 amended with biochar (0.5 and 1.0 wt%) brought about 12–20 % increase in SMX, SMZ, and SD retention compared to the untreated soil.

Conclusions

The results indicated that the presence of biochar effectively mitigated the mobility of ionized antibiotics such as SMX, SMZ, and SD in soils, which helps us reconsider the potential risk of antibiotics in the environment.

Purpose

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is an important native tree species in China. Consecutive cropping traditionally occurs in Chinese fir plantations (CFPs), but this practice has resulted in productivity declines in subsequent rotations. This study was designed to better understand the change of soil properties in the continuous cropping CFPs.

Materials and methods

We investigated soil pH, soil organic matter (SOM), and nutrient contents in different soil layers and in rhizosphere soil (RS) and non-rhizosphere soil (NRS) under CFPs of different ages and in different rotations.

Results and discussion

In the upper (0–20 cm) soil layer, soil pH decreased, while SOM increased, beneath mature CFPs with consecutive rotations. Total nitrogen (TN), available potassium, and available phosphorus contents in the upper soil layers did not differ significantly with consecutive rotations. Soil pH in RS was significantly lower than in NRS under mature plantations of the third rotation. Soil organic matter, TN, and available nitrogen did not differ between RS and NRS. Available phosphorus in RS was consistently lower than in NRS, and was highly deficient in the third rotation.

Conclusions

We conclude that no severe soil nutrient degradation occurred in the continuous cropping CFPs examined in this study, with soil acidification and phosphorus deficiency being two primary problems observed.

Purpose

The synthetic soil based bioremediation approach as reasonable and sustainable practice at the farming level where desired bioremediation could be established at lower cost.

Materials and methods

Metal-tolerant bacteria from different environmental field samples, (a) a municipal dump site, (b) an agricultural field and (c) sludge of electro-plating industries, were screened and characterized. Bioremediation of metal contaminants through isolated bacteria was compared under two different conditions, synthetic soil and basic minimal media containing copper, cobalt and nickel.

Results and discussion

The pollutants arising from industrial effluents are imparting a huge negative impact on agricultural land. Microbes are predominant in heavy metal-contaminated sites, which signifies as a potential opportunity for the researchers towards bioremediation. Three bacterial species showed high metal tolerance; 16S ribosomal DNA (rDNA) analysis revealed that the organisms were Proteus vulgaris strain, Stenotrophomonas sp. and Bacillus thuringiensis. Percentage removal of metals was also analysed under different concentrations and pH.

Conclusions

The current tested methods are helpful in streamlining the natural compliance of fragile elements and its uptake into the microbial system under in vitro and in situ conditions.

Purpose

Nanoparticles (NPs) have received increased attention in recent past due to their unique distinct properties. Metal-based NPs are widely used in chemical and allied sector. Most of the research is directed to study the efficiency of NPs in medicine and agriculture. The aim of this review is to explore the possible threats posed by toxicity of various NPs on plants and microbial diversity.

Materials and methods

First, major sources of NPs to the environment were analyzed. The effects of metal-based NPs on the microbiota and plants are presented in this review. The results obtained by the authors during last 12 years of research are used.

Results and discussion

The exposure of soil to nanoparticles causes a decrease in soil microbial biomass and enzymatic activity, which impacts microbial community composition including yeasts, bacteria, fungi, and biological diversity. The effects of NPs on plants result in various types of abnormalities. Nanoparticles can also pose risks to human health.

Conclusions

Increased applications of NPs pose a threat to beneficial microbial communities as well as crops and soils. Thus, it is important to explore whether NPs could compromise crop yield, soil properties, soil organisms, and functional activities of soil.

Purpose

Fungi are essential components of soil microbial communities and have a crucial role in biogeochemical processes. Alpine regions are sensitive to climate change, and the importance of changes in fungal community composition along altitudinal gradients in alpine regions is hotly debated.

Materials and methods

We used 454 pyrosequencing approaches to investigate the fungal communities at 1600, 2300, 2800, 3000, and 3900 m above sea level along an altitudinal gradient on Mount Gongga.

Results and discussion

The results showed that Agaricomycetes, Sordariomycetes, and Tremellomycetes are the dominant classes at all sampling sites. Operational taxonomic unit richness decreased with increasing altitude, and the fungal communities were clustered into three groups that corresponded to altitudes of, i.e., 1600, 2300, and above 2800 m. The evenness of fungi was not significantly correlated with altitude, whereas beta diversities were significantly correlated with altitude. The distance-based redundancy analysis and Mantel test indicated that the composition of fungal assemblages was mostly driven by altitude and temperature.

Conclusions

Our results indicated that ecological processes possibly related to altitude and temperature play an important role in structuring fungal biodiversity along the elevational gradient. Our results highlight that different microbes may respond differently to environmental gradients.

Purpose

The concerns of the public on safe handling of nuclear energy power facilities have increased due to the recent nuclear plant accidents in Japan and others. Cesium, cobalt, and strontium are a few of the major radionuclides released from nuclear power plant accidents. The objectives of this study are to investigate binding, distribution, fractionation, and transformation of cesium (Cs), cobalt (Co), and strontium (Sr) in a US coastal soil under saturated paste (SP) and field capacity (FC) moisture regimes.

Materials and methods

There are four major nuclear power plants in the coast region around the northern Gulf of Mexico where coastal soil often undergoes soil moisture change. A coastal soil was taken from the middle region of these major nuclear power plants and spiked with different concentrations of cesium, cobalt, and strontium salts. The sequential selective dissolution technique was used to investigate the transformation and fractionations of these metals in the coastal soils affected by moisture regime, a key factor in the coastal environment.

Results and discussion

The adsorption kinetics showed that both Co and Sr reached the adsorption plateau even after 5 h of adsorption, indicating a fast initial adsorption process in the coastal soil. Cesium, cobalt, and strontium were dominantly presented in the soluble and exchangeable form (EXC) (Cs?>?Co and Sr), which linearly increased with the addition levels, possessing the high bioavailability, mobility, and ecotoxicity. Saturated regime significantly reduced the soluble and exchangeable form compared to field capacity moisture regime.

Conclusions

The current study provides the fundamental understanding for designing the cost-effective remediation technology to remediate these metals in coastal soil by targeting on the soluble and exchangeable forms and better prepare the USA for future potentially nuclear power plant accidents.

Purpose

The validity of soil erosion data is often questioned because of the variation between replicates. This paper aims to evaluate the relevance of interreplicate variability to soil and soil organic carbon (SOC) erosion over prolonged rainfall.

Materials and methods

Two silty loams were subjected to simulated rainfall of 30 mm h^?1 for 360 min. The entire rainfall event was repeated ten times to enable statistical analysis of the variability of the runoff and soil erosion rates.

Results and discussion

The results show that, as selective removal of depositional particles and crust formation progressively stabilized the soil surface, the interreplicate variability of runoff and soil erosion rates declined considerably over rainfall time. Yet, even after the maximum runoff and erosion rates were reached, the interreplicate variability still remained between 15 and 39 %, indicating the existence of significant inherent variability in soil erosion experiments.

Conclusions

Great caution must be paid when applying soil and SOC erosion data after averaging from a small number of replicates. While not readily applicable to other soil types or rainfall conditions, the great interreplicate variability observed in this study suggests that a large number of replicates is highly recommended to ensure the validity of average values, especially when extrapolating them to assess soil and SOC erosion risk in the field.

Purpose

Urban soils’ variability in the vertical direction presumably affects hydrological parameters at the timescale. Moreover, horizontal soil alterations at small spatial scales are common in urban areas. This spatio-temporal variability and heterogeneity of soil moisture and the possible influencing factors were to be described and quantified, using data of a soil monitoring network in the city of Hamburg, Germany.

Materials and methods

Soil moisture data from ten observation sites within the project HUSCO was evaluated for two different years. The sites were located within districts with different mean groundwater table depths and characteristic urban soil properties. Soil hydrological simulations with SWAP were calculated for a selected site.

Results and discussion

The temporal evolution of soil water content and tension for the sites was very distinct, related to soil substrate, organic matter content, and groundwater table depth. Impacts of different vegetation rooting depths, the soil substrates’ type, and to some extent the degree of disturbance on soil water dynamics could be identified. An impact of groundwater table depth on the water content of the topsoil during low-precipitation periods could be assumed. The comparison of the results of soil hydrological simulations with empirical data indicated an overestimation of infiltration and percolation for the given soil substrates.

Conclusions

While soil properties are mainly determinant for the long-term progression of soil hydrology, local site factors affect the short-term regime. A shallow groundwater table contributes to more constant water dynamics while the relative decrease of water during a dry phase is diminished.

Purpose

The objective of this review is to survey critically the results obtained by the application of laser-induced fluorescence spectroscopy (LIFS) and laser-induced breakdown spectroscopy (LIBS) to the evaluation of the humification degree (HD) of soil organic matter (SOM) directly in untreated, intact whole soils.

Materials and methods

A large number of soils of various origin and nature, either native or under various cultivations, land use, and management, at various depths, have been studied to evaluate the HD of their SOM directly in intact whole samples. The LIFS spectra were obtained by either a bench or a portable argon laser apparatus that emits UV-VIS light of high power, whereas the LIBS spectra were obtained using a Q-switched Nd:YAG laser at 1064 nm.

Results and discussion

The close correlations found by comparing H_LIF values of whole soil samples with values of earlier proposed humification indexes confirmed the applicability of LIFS to assess the HD of SOM in whole soils. The high correlation found between HD_LIBS values and H_LIF values showed the promising potential of LIBS for the evaluation HD of SOM.

Conclusions

The LIFS technique shows to be a valuable alternative to evaluate the HD of SOM by probing directly the whole solid soil sample, thus avoiding the use of any previous chemical and/or physical treatments or separation procedures of SOM from the mineral soil matrix. The emerging application of LIBS to evaluate the HD of SOM in whole soils appears promising and appealing due to its sensitivity, selectivity, accuracy, and precision.

Purpose

Soil washing with chelators is a viable treatment alternative for remediating multi-contaminated soils. The aim of this study was to investigate the removal efficiencies of Cd, Zn, Pb, and Cu in alkaline and acid multi-metal-contaminated soils by washing with the mixed chelators (MC).

Materials and methods

The batch experiments were carried out to evaluate the removal efficiencies of heavy metals in contaminated soils by the MC with different molar ratios of EDTA, GLDA, and citric acid, and evaluated the washing factors, including contact time, pH, MC concentration, and single and multiple washings at the same MC dose, on the removal efficiencies.

Results and discussion

Results showed that the removal efficiencies for Cd, Zn, Pb, and Cu by the MC (the molar ratio of EDTA, GLDA, and citric acid was 1:1:3) were as much as those of the only EDTA washing from both soil at the same application dose of total chelators; moreover, the application dose of EDTA decreased by 80%. For the alkaline-contaminated soil, the removal efficiencies of Cd, Zn, Pb, and Cu decreased with the increasing of the solution pH, which was opposite to acid-contaminated soil. This was attributed to that the metal-ligand complex could be obviously re-adsorbed on the soil surface sites, particularly in low pH values. The removal efficiencies of Cd, Zn, Pb, and Cu depended on MC concentration. A higher MC concentration led to a more effective removal of Cd, Zn, Pb, and Cu in alkaline-contaminated soil; however, their changes were slightly increased in acid-contaminated soil. At the same dose of MC, single washing with higher MC concentration might be favorable to remove heavy metals, moreover, with much less wastewater generation.

Conclusions

The MC (the molar ratio of EDTA, GLDA, and citric acid was 1:1:3) may be a useful, environmentally friendly, and cost-effective chelators to remediate heavily multi-metal-contaminated soil.

Purpose

Biochar, the by-product of thermal decomposition of organic materials in an oxygen-limited environment, is increasingly being investigated due to its potential benefits for soil health, crop yield, carbon (C) sequestration, and greenhouse gas (GHG) mitigation.

Materials and methods

In this review, we discuss the potential role of biochar for improving crop yields and decreasing the emission of greenhouse gases, along with the potential risks involved with biochar application and strategies to avoid these risks.

Results and discussion

Biochar soil amendment improves crop productivity mainly by increasing nutrient use efficiency and water holding capacity. However, improvements to crop production are often recorded in highly degraded and nutrient-poor soils, while its application to fertile and healthy soils does not always increase crop yield. Since biochars are produced from a variety of feedstocks, certain contaminants can be present. Heavy metals in biochar may affect plant growth as well as rhizosphere microbial and faunal communities and functions. Biochar manufacturers should get certification that their products meet International Biochar Initiative (IBI) quality standards (basic utility properties, toxicant assessment, advanced analysis, and soil enhancement properties).

Conclusions

The long-term effects of biochar on soil functions and its fate in different soil types require immediate attention. Biochar may change the soil biological community composition and abundance and retain the pesticides applied. As a consequence, weed control in biochar-amended soils may be difficult as preemergence herbicides may become less effective.

Purpose

Soil microbes control the bioelement cycles and energy transformation in forest ecosystems, and are sensitive to environmental change. As yet, the effects of altitude and season on soil microbes remain unknown. A 560 m vertical transitional zone was selected along an altitude gradient from 3023, 3298 and 3582 m, to determine the potential effects of seasonal freeze-thaw on soil microbial community.

Materials and methods

Soil samples were collected from the three elevations in the growing season (GS), onset of freezing period (FP), deeply frozen period (FPD), thawing period (TP), and later thawing period (TPL), respectively. Real-time qPCR and polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) were used to measure the abundance and structure of soil microbial community.

Results and discussion

The bacterial, archaeal, and fungal ribosomal DNA (rDNA) copy numbers decreased from GS to freezing stage (FP and FPD) and then increased in thawing stage (TP and TPL). Similarly, the diversity of microbial community varied with seasonal freeze-thaw processes. The diversity index (H) of the bacterial and archaeal communities decreased from GS to FP and then increased to TPL. The fungal community H index increased in the freezing process.

Conclusions

Our results suggested that abundance and structure of soil microbial community in the Tibetan coniferous forests varied by season and bacterial and archaeal communities respond more promptly to seasonal freeze-thaw processes relative to fungal community. This may have important implications for carbon and nutrient cycles in alpine forest ecosystems. Accordingly, future warming-induced changes in seasonal freeze-thaw patterns would affect soil nutrient cycles via altering soil microbial properties.

Purpose

Land preparation (e.g., leveled ditches, leveled benches, adversely graded tableland, and fish-scale pits) is one of the most effective ecological engineering practices to reduce water erosion in the Loess Plateau, China. Land preparation greatly affects soil physicochemical properties. This study investigated the influence of different land preparation techniques during vegetation restoration on soil conditions, which remained poorly understood to date.

Materials and methods

Soil samples were collected from depths of 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm, in the typical hilly watershed of Dingxi City, Loess Plateau. Soil bulk density (BD), soil organic matter (SOM), and total nitrogen (TN) were determined for different land preparations and vegetation type combinations. Fractal theory was used to analyze soil particle size distribution (PSD).

Results and discussion

(1) The effect of land preparation on soil properties and PSD varied with soil depth. For each land preparation category, SOM and TN values showed a significant difference between the top soil layer and the underlying soil depths. (2) The fractal dimension of PSD showed a significant positive correlation with clay and silt content, but a significant negative correlation with sand content. (3) The 20 cm soil layer was a boundary that distinguished the explanatory factors, with land preparation and vegetation type as the controlling factors in the 0–20- and 20–100-cm soil layers, respectively.

Conclusions

Land preparation and vegetation type significantly influenced soil properties, with 20 cm soil depth being the boundary for these two factors. This study provided a foundation for developing techniques for vegetation restoration in water-limited ecosystems.

Purpose

Field portable X-ray fluorescence (FPXRF) technology can offer a rapid and cost-effective determination of the total elemental concentrations in soils. The aims of this study were (i) to test the capability of FPXRF to predict the element concentrations of a very large soil sample set and (ii) to assess the influence of soil moisture, known to strongly affect the quality of FPXRF analyses.

Materials and methods

A large set of 215 soil samples were analysed for Ba, Ca, Cr, Cu, Fe, Mn, Pb, Rb, Sn, Sr and Zn by inductively coupled plasma atomic emission spectroscopy (ICPAES) after aqua regia digestion and with a FPXRF analyser using a short acquisition time. Soil samples were then saturated with ultrapure water to test the influence of soil water content on FPXRF signal.

Results and discussion

For all of the elements, the total concentrations obtained with ICPAES and FPXRF showed a very high degree of linearity, indicating that FPXRF can effectively predict element concentrations in soils. A Lambert-Beer law was successfully used to describe the decrease in the FPXRF concentrations with increasing soil moisture. The attenuation coefficient obtained for each element allowed us to satisfactorily predict the FPXRF concentrations of samples for water contents as high as 136.8 %.

Conclusions

These results show that the effect of water on signal attenuation can be corrected and that FPXRF may gradually replace chemical methods for the analysis of environmental samples.

Purpose

The use of composted sewage sludge and limestone outcrop residue in land rehabilitation, soil improvement, and technosol making can influence the mobility of nitrogen compounds in groundwater.

Materials and methods

This experiment analyzed this source of possible pollution under an experimental design based on the use of columns (0–30 cm) formed by both wastes and a heavy irrigation regime. Two waters of different quality (saline and non-saline) were used for irrigation. The presence of nitrate, nitrite, and ammonium in the leachates was checked.

Results and discussion

The environmental risk due to the presence of nitrogen species associated with the use of these materials was very low in general, although nitrate was the most important compound affected by the use of sewage sludge compost and saline water.

Conclusions

The combination of saline water for irrigation with the compost has to be seriously considered as a source of pollution for surface and ground waters, and the use of both resources may be a key factor to be studied (low-quality water and sewage sludge compost).

Purpose

The purpose of this study is to examine the effects of combined application of biomass ash (BA), bone meal (BM), and alkaline slag (AS) on soil acidity, nutrient contents, uptake of the nutrients by wheat, and wheat growth.

Materials and methods

A pot experiment with an Ultisol collected from Anhui province, China, was conducted to compare the effects of BA, BM, and AS applied alone and combined on soil acidity; soil nutrient contents; uptake of N, P, K, Ca, and Mg by wheat, and wheat growth.

Results and discussion

Application of BA, BM, and AS alone and combined increased soil pH and decreased soil exchangeable Al³⁺. BA + BM + AS showed the greatest ameliorating effect on soil acidity, and soil pH of the treatment increased by 1.24 units compared with control. Application of BA + BM + AS reduced soil exchangeable Al³⁺ and increased soil exchangeable calcium and magnesium to a greater extent than BA + BM and single application of the amendments. The BM-containing amendments substantially increased soil available phosphorous by 66–93% compared with control. Application of the amendments alone and combined enhanced the uptake of N, P, K, Ca, and Mg by wheat and thus promoted wheat growth and increased yield of wheat grains. Application of BA + BM + AS and BA + BM showed greater effects on nutrient uptake and wheat growth than single application of the amendments. Wheat straw weights of the two treatments were 11.1 and 10.1 times greater than that of control. The data were 2.7, 4.8, and 5.6 times for the treatments of BA, AS, and BM. The contents of Cd, Cr, Zn, and Cu in wheat grains were lower than standard limits, except for the single BA treatment.

Conclusions

BA + BM + AS is the best choice for amelioration of acid soils and promotion of crop production.

Purpose

This study was aimed to investigate the potential of biochar (BC), a waste byproduct of a bioenegy industry, Sri Lanka, as a soil amendment to immobilize and reduce the phytotoxicity of Cr in tannery waste-polluted soil (TWS).

Materials and methods

The TWS and bioenergy waste BC were characterized for physio-chemical parameters. A pot experiment was conducted by adding three BC application rates, 1, 2.5, and 5 % (w/w) to investigate the immobilizing capacity and bioaccumulation of chromium (Cr) in tomato plants (Lycopersicon esculentum L.). Soils and plants were digested via microwave digestion and analyzed for total Cr. Further, sequential extraction was conducted to assess the fractionation of Cr before and after the application of bioenergy waste BC on TWS.

Results and discussion

The total Cr concentration in TWS was 12,285 mg/kg. The biomass of tomato plants grown in the 5 % BC amendment doubled compared to the biomass in BC-unamended soil. Bioaccumulation of Cr in plants grown in 5 % BC-amended TWS showed a decrease by 97 % compared to that of the BC-unamended soil. The CaCl₂ extractability of Cr indicated that the bioavailability of Cr in the 5 % BC amendment has decreased by 68 % compared to the control. Sequentially extracted Cr in the exchangeable fraction decreased by 98 % in the 5 % BC amendment.

Conclusions

Pore diffusion, and adsorption via π-π electron donor-acceptor interactions were the primary mechanisms to be involved in the Cr retention in BC. Results suggested that the addition of BC to TWS reduces the mobility, bioavailability, and phytotoxicity of Cr in tomato plants.

Purpose

Long-term tea plantation (Camellia sinensis L.) could markedly change the pools of total fluoride (T-F) in soil extractable fractions. However, the effects of different chronosequence phases on the changes of fluoride fractions in these plantations are poorly understood.

Materials and methods

In this study, we have investigated the distribution of extractable fluoride fractions in four differently aged tea plantations (16, 23, 31, and 53 years old, respectively), in Zhongfeng Township of Ming-shan County, Sichuan, Southwest China. This study aimed to determine the effects of the age of various tea plantations with respect the contents of T-F, also considering the water-soluble fluoride (Ws-F), the exchangeable fluoride (Ex-F), the Fe/Mn oxide-bound fluoride (Fe/Mn-F), the organic matter-bound fluoride (Or-F), and the residual fluoride (Res-F) within soil aggregates.

Results and discussion

The T-F, Ws-F, Ex-F, and Res-F contents increased with the decreasing of particle size except for Fe/Mn-F and Or-F. Along with the increase of tea plant life, the contents of Ws-F and Ex-F within soil aggregates gradually increased. In addition, the trends of extractable Fe/Mn-F and Or-F were opposite to that of highly available fluoride after 23 years.

Conclusions

The results of this study show that fluoride is easily transformed into highly available phases in long-term tea plantations, improving the absorption of fluoride for tea plants.

Purpose

The relationship between soil properties and plant communities was investigated in a saltmarsh of the Grado and Marano lagoon (northern Italy), where hydrology and micromorphology strongly influence the features of the ecosystem. A multidisciplinary approach was used to assess the change of soil properties and plant communities in relation to the submergence of soil.

Materials and methods

The plant community and soil profile surveys were both carried out along a transect in six sampling sites of the Gran Chiusa saltmarsh (Grado and Marano lagoon). The morphological and physicochemical parameters of soil profiles were investigated, and soils were classified according to Soil Taxonomy. The concentration of macronutrients in both soils and plants was analysed by inductively coupled plasma-optical emission spectrometry. Cluster and linear discriminant analysis were used to assist the interpretation of the data of plant communities and soil properties, respectively. The bioconcentration factor explored the macronutrient relationship between plant community and soil.

Results and discussion

A high, middle and low zone were identified by clustering the different plant communities along the studied transect. Discriminant analysis showed how the increase in soil submergence supported the accumulation of S and Ca content and depletion of Fe and Na. The development of different plant communities was linked to both soil water saturation and to the capacity of halophytes to tolerate anoxic conditions or salinity, by extrusion or bioconcentration strategies.

Conclusions

This study demonstrates that tide level plays an important role in the pedological development and chemical transformations along a soil hydrosequence. The micromosaic vegetation pattern may therefore represent a useful index of the hydrological and nutritional status of the underlying soils and could be used to predict changes in coastal ecosystems.

Purpose

Grassland exclosure is a widely-used option to prevent from grazing in degraded grasslands for restoration. However, the influence of exclosure on soil macropore of grassland remain scarce. The objective of this study was to quantify the pore architecture of grassland soils under exclosure.

Materials and methods

Two treatments, 9E (grassland enclosed for 9 years) and 5E (grassland enclosed for 5 years), were designed, with grazing as a control in the experiment. Nine soil columns (0–50 cm deep) were taken at the three sites with three replicates. At each site, three soil columns were from the grassland, and cores were scanned with a Philips Brilliance ICT Medical Scanner. Numbers of macropores, macroporosity, network density, length density, and node density within the 50-cm soil profile were interpreted from X-ray computed tomography to analyze soil pore architecture.

Results and discussion

The results indicated that exclosure significantly influenced CT-measured soil macroporosity in the Inner Mongolia grassland of northern China. Soils under enclosed grassland had greater macroporosity, length density, total volume, and node density than that of under freely grazed grassland. Macroporosity increased as the enclosure age increased. For soils under enclosed grassland, macropores were concentrated at 0–300-mm soil layers, and macropores were mainly present at 0–100-mm soil depth under freely grazed grassland. The large number of macropores found in soil under enclosed grassland can be attributed to greater root development.

Conclusions

Exclosure increases soil macroporosity and improve soil structure.