•Terrestrial isopods act as material recycling converters in the ecosystem.•Isopods can release nutrients from litter through direct and indirect effects.•Isopods may prefer litter with a low ...C/N.•Isopods can improve soil nutrient content and soil quality.
Soil fauna are important biological factors that affect litter decomposition and play an important role in the release of nutrients, such as carbon and nitrogen. This study focused on the role of soil fauna in litter decomposition. Field microcosm experiments were conducted to assess the influence of isopods (Porcellionidae and Armadillidiidae) on soil nutrients during the litter decomposition of Catalpa bungei (CL), Platanus acerifolia (PL), and Aesculus chinensis (AL). The litter mass loss and nutrients in different soil layers treated with various isopods were determined in three-month microcosm incubations. Results showed that the presence of isopods significantly increased (P < 0.05) the litter decomposition rates compared with the control treatment (CK). The average weight (2.56 g) and total weight ratio (85.47%) of the isopod-decomposed litter were much larger than those of the CK treatment (0.43 g and 14.31%, respectively). In the different litter types collected, CL showed the highest decomposition rate among the different isopod treatments. Isopods increased the contents of organic carbon (OC), total nitrogen (TN), total potassium (TP), Olsen phosphorus (OP), available potassium (AK), ammonia nitrogen (NH4+–N), and nitrate nitrogen (NO3––N) in the surface soil by 59.19%, 27.36%, 2.72%, 29.30%, 5.85%, 13.10%, and 14.60%, respectively, relative to CK. The profile distribution of soil nutrients and the soil quality index under different isopod treatments were significantly (P < 0.05) greater in the 0–1 cm soil layer than in the 1–2, 2–4, and 4–6 cm soil layers. Further analysis showed that this significance was affected by decomposition time, isopod species, soil depth, and the interactions of these factors. The findings demonstrate that the isopods could accelerate litter decomposition and improve soil nutrients. This work provides evidence demonstrating that soil fauna can improve surface soil quality by promoting litter decomposition.
•Progress of research on Benggang erosion was systematically analyzed.•Research deficiencies exist in understanding of erosion mechanism, prevention and evaluation.•Possible future research ...directions and priorities were identified.•Hydraulic-gravitational composite erosion mechanism and modelling is the main future research direction.
Benggangs are a special type of severely eroded landform in southern China. They cause severe damage to soil resources, which has had a large negative impact on local ecological environments and people’s lives. Benggang erosion has received abundant attention in the past few decades, but few studies have systematically summarized and analyzed the progress, deficiencies and future directions of research of Benggang erosion. The purpose of this paper is therefore to analyze the progress of research on Benggang erosion, summarize the research deficiencies and propose future research directions and priorities. Benggangs gained attention in the 1960s, and studies of Benggang erosion have achieved rich results, including the characteristics of parental materials, spatial variation of soil properties in Benggang areas, mechanisms of the occurrence and process of Benggang erosion, dynamic monitoring of Benggang erosion, estimation of erosion volume, measures for controlling Benggang erosion and evaluation of their effectiveness. These studies have improved our knowledge and understanding of the basic attributes, occurrence, development, and factors influencing Benggang erosion and have provided a scientific basis for the optimal arrangement of measures for conserving soil and water and the rational development and effective management of Benggangs. We nevertheless believe that deficiencies remain in the aspects of the optimization of monitoring methods, mechanism of composite erosion, control of erosion and evaluation of the effectiveness of controlling Benggang erosion under the current level of development of research on soil erosion and the high standard of ecological protection. Further studies are necessary in the following areas: space-air-ground integrated technology for optimizing the monitoring of Benggang erosion; mechanism of hydraulic-gravitational composite erosion and the construction of models; research, development and application of new material for the prevention and control of Benggang erosion and development of a system for evaluating the effectiveness of erosion control. These research topics can supplement and enrich the content of traditional research on Benggang erosion and are very important for the restoration of ecological environments and improving ecological services and functions in areas with Benggang erosion.
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•Macropore characteristics differ significantly among the four soil types.•The D1 increases from loessial, Lou, aeolian sandy to light dark loessial soil.•The ΔD is dominant ...predicting variable for the theoretical Ks and total porosity.•Macropore number plays an incomparable role in soil pore structure.
As an important inherentcondition for an eroded landform and fragile ecosystem, the erodible loess in China’s Loess Plateau is a clastic and predominantly silt-sized sediment. Understanding the pore complexity of the loess may be crucial for exploring soil functional properties and improving knowledge on hydrological dynamic processes occurring in the soil plant atmosphere continuum. Twelve undisturbed columns of four typical soil types, namely, aeolian sandy, light dark loessial, loessial, and Lou soils, were collected for the multifractal analysis of X-ray computed tomography images. The heterogeneity of soil pore distribution and the measure of porosity dispersion relative to the pore size dispersion in the loessial and Lou soils were significantly lower than those of the aeolian sandy and light dark loessial soils. The loessial soil exhibited the highest symmetry of singularity spectra and presented the lowest variability for pore arrangement. Most correlations among parameters of soil properties, multifractal characteristics, as well as soil macropore morphology and connectivity characteristics, were significant (p < 0.05 or 0.01). The multiple regression models of the theoretical saturated hydraulic conductivity and total porosity incorporated all types of the parameters, and the multifractal parameter ΔD was the dominant variable. Macropore connectivity parameters were commonly superior to the morphology ones when the links between macropore characteristics and multifractal parameters were considered. Meantime, the number of macropores acted as a crucial parameter influencing the complexity of soil pore structures. Overall, it is of great significance to integrate the soil pore complexity into the comprehensive understanding of pore function. This study also provides an effective reference for optimizing soil structures, improving the soil water holding capacity, and balancing the relationship between water and ecosystems in the Loess Plateau.
As soil ecosystem engineers, ants considerably affect soil physical and chemical properties, and further accordingly affect soil erosion. However, few study was made on studying the effects of ...ant-burrowing activities on soil erosion previously. This study quantified the impacts of ant (Camponotus japonicus)-burrowing activities on runoff and soil erosion rates. Simulated laboratory rainfall experiments were undertaken on six soil tanks filled with clay-loam soil classified as a cumulic anthrosol, three of which introduced with ant colonies for two days and the other three were without ant colonies, under 40, 80, and 120 mm h−1 of rainfall intensities and a slope of 15°. Results showed that ants made mounds with a bulk density of 0.75 g cm−3, which was lower than that of the soil matrix, i.e. 1.34 g cm−3. Soil erosion rates for the tanks with ants were 6.78, 36.90, and 62.00 g m−2 min−1 under three rainfall intensities of 40, 80, and 120 mm h−1, which were much higher than those of 3.94, 23.49, and 44.48 g m−2 min−1 for the tanks without ants. Ant nests reduced the runoff rate by 31%, 20% and 13% compared with those without ants and enhanced the soil water storage within 90 cm depth. Ant nests played a positive role in soil water conservation due to the large nest entrance diameter and the continuous macropore network. However, the ant mounds provided a loose erodible material and changed micro-topography of the slope surface, thereby accelerating the rill formation and exacerbating soil erosion. This study can help understand the effects of burrowing insects on soil erosion, which is an important environmental problem on the Loess Plateau.
•Ant nests reduced the runoff rate and increased soil water storage.•Ant mounds changed the micro-topography and accelerated rill generation.•Ant mounds increased soil erosion rate on bare slopes.
•Mean K was 0.043 t ha h ha−1 MJ−1 mm−1 in the hilly southeastern China.•Three common pedotransfer functions were first built to estimate K in the area.•Pedotransfer functions of MLR-DFV and ANN-DFV ...had high prediction accuracy.•ANN-DFV estimated K was more similar in distribution and variability to the true K.
Soil erodibility (K) reflects the sensitivity of soil to detachment and transport and is a key factor for estimating the loss of soil. Most of the models for estimating K are complex and experiential, simple and local estimation model in the hilly and mountainous southeastern China is rare. This study aims to build local pedotransfer functions (PTFs) for soil erodibility estimation and evaluate the performance of the built PTFs, i.e. multiple linear regression (MLR), MLR with deformed forms of variables (MLR-DFV) and artificial neutral network with deformed forms of variables (ANN-DFV) to estimating K in southeastern China. The local true K values were obtained by a comprehensive method that considering the optimization prediction model and runoff-plot monitoring data. The best predictive variables were determined using correlation analysis, principal component analysis, importance evaluation and minimum variable-set determination. Mean K in the study area was 0.043 t ha h ha−1 MJ−1 mm−1, ranging from 0.019 to 0.060 t ha h ha−1 MJ−1 mm−1, showed a moderate spatial variability. Soil organic-matter content (SOM) was the most important factor influencing K and accounted for 17.5 % of the total importance. Soil sand content, geometric mean diameter of aggregates, SOM and synthetic curvature were identified as the best predictive variables representing soil physical properties, aggregate characteristics, nutrient and topographical conditions, respectively. The accuracies of MLR-DFV and ANN-DFV were high and similar but higher than the accuracy of MLR. K estimated using ANN-DFV was more similar in magnitude, distribution, and spatial variability to the true K data than K estimated using MLR-DFV. We developed the first local PTFs for estimating K in the hilly and mountainous southeastern China, which could provide empirical basis and method support for studying K in similar regions.
•Vegetation restoration is beneficial to the protection of soil fauna diversity.•Soil fauna can be used as indicators to evaluate artificial vegetation restoration.•Soil fauna are remarkably affected ...by litter and soil properties.•Herbaceous plants are more worthy of consideration than that using shrubs and trees.
The relationship between soil fauna and vegetation diversity has been of continuous concern. The effects of the “Grain-for-Green” program on the Loess Plateau in maintaining the abundance and diversity of soil fauna are poorly understood. This study assessed the spatial influence of five common artificial restoration habitats, Populus simonii, Pinus tabulaeformis, Caragana korshinskii, Medicago sativa, and Stipa bungeana, and one farmland habitat on the characteristics of soil fauna communities. Results showed that six soil fauna groups (Araneae, Acarina, Collembola, Isoptera, Coleoptera larvae, and Coleoptera adults) were shared among these habitats, accounting for 37.5% of the total number of groups. Acarina was the dominant group in each habitat. The soil fauna abundance in the P. tabulaeformis habitat was the highest among the habitats, reaching 7656 ind m−2. S. bungeana had the highest diversity, richness, and evenness indices of soil fauna among the habitats. Furthermore, a remarkable correlation among main soil properties (water content, organic carbon, and available potassium), litter properties (vegetation coverage, vegetation density, and litter thickness), and soil fauna were observed. The differences in microenvironment among the six habitats had a strong influence on the composition of soil fauna communities. Compared with other habitats, the S. bungeana habitat is more conducive to the protection of biodiversity. Vegetation restoration increases the diversity of soil fauna by improving their living environment, and soil fauna communities can be used as assessment indicators for “vegetation restoration benefits.” These findings help reveal the developmental tendencies of soil fauna during vegetation restoration in the Loess Plateau, and provide important support for evaluating environmental quality by soil fauna.
Soft strain sensors based on conductive polymer composites (CPCs) provide a simple and feasible detection tool in wearable electronics, soft machines, electronic skin, etc. However, the CPCs-based ...soft strain sensors exhibit resistive viscoelasticity (or time-dependent properties) that hinder the intuitive reflection of the accurate strain and a simple calibration process. In this paper, CPCs with different carbon nanotubes (CNTs) and carbon black (CB) contents were prepared, and electro-mechanical experiments were conducted to study the effect of filler dimensionality and content on the resistive viscoelasticity of CPCs, aimed at guiding the fabrication of CPCs with low resistive viscoelasticity. Furthermore, resistive viscoelasticity and mechanical viscoelasticity were compared to study the origin of the resistive viscoelasticity of CPCs. We found that, at the vicinity of their percolation threshold, the CPCs exhibit high resistive viscoelasticity despite their high sensitivity. In addition, the secondary peaks for CB/SR composite were negligible when the CB concentration was low. Generally, compared with one-dimensional CNT-filled CPCs, the zero-dimensional CB-filled CPCs show higher sensitivity, lower resistive hysteresis, lower resistance relaxation ratio, and better cyclic performance, so they are more suitable for sensor usage. By comparing the resistive viscoelasticity and mechanical viscoelasticity of CPCs, it is indicated that, when the concentration of nanoparticles (NPs) approaches the percolation thresholds, the resistive viscoelasticity is mainly derived from the change of conductive network, while when the concentration of NPs is higher, it is primarily due to the unrecoverable deformations inside the material.
Gully is a typical geographical unit and a key component of the slope–gully system on the northern Loess Plateau. Understanding the distribution of soil moisture in gullies aids water resource ...regulation and ecological restoration. To investigate temporal–spatial variability of soil moisture, we measured values of soil water content (SWC) within 0–500 cm by using a neutron probe on 19 occasions from October 2014 to July 2017 in the gully and bank of a developed gully in Liudaogou catchment of Shenmu County. Results showed that the values of space–averaged soil water storage (SWS) in the gully were significantly (P < 0.01) higher than those in the bank. Soil clay content (SCC) and topography (including site elevation and distance from the gully head) were the most important factors affecting SWS of 0–500 cm in the gully. Topography can indirectly control SWS by redistribution of rainfall and soil properties. SWS and SCC rose with increasing distance from the gully head to the outlet. SWS in the gully exhibited strong temporal stability, and two time–stable sites around the middle section can be used to represent mean SWS within 500 cm depth in the gully. The gully sidewall significantly (P < 0.05) aggravated drought of soils in the bank between 150 and 250 cm from the gully edge. Gullies make the temporal–spatial patterns of soil moisture complex in slope–gully system. These results were expected to improve understanding of soil moisture distribution in the gully region and aid vegetative restoration of the northern Loess Plateau.
•Soil texture and topography predominantly influence the soil moisture from o to 500 cm in the gully.•Intense rainfall may contribute to the unique spatial pattern of SWS in the gully.•Plots around the middle can represent the mean SWS within 0–500 cm in the gully.•Gully sidewall aggravated the soil drought in the bank between 150 and 250 cm from the gully edge.
Afforestation is a common and effective approach used for the restoration of degraded ecosystems worldwide. In China, Robinia pseudoacacia (RP) is among the main non-native tree species and has been ...widely planted in revegetation of the Loess Plateau. However, owing to uncertainties regarding soil water consumption and carbon sequestration, it is necessary to assess the suitability and sustainability of R. pseudoacacia in restoration. In this study, we aimed to analyse the dynamic effects of R. pseudoacacia forest on soil carbon storage (SCS) and soil water storage (SWS). Specifically, we investigated the association between soil water content (SWC) and soil organic carbon (SOC) and underlying factors in the 0–500-cm profile of a 10- to 50-year-old chronosequence.
The results obtained indicated that the dynamics of SWS and SCS on this time scale could be divided into an initial reduction phase (the initial 20 years after afforestation) and subsequent recovery (20–50 years after afforestation). Compared with in the abandoned land (AL), the net accumulation of SCS in R. pseudoacacia forest was 2.51 Mg·ha−1 at 50 years after afforestation, whereas there was a 398.76-mm deficit in SWS. Additionally, the natural succession of R. pseudoacacia forest has contributed to the continuous change in stand structure (e.g. vegetation cover (VC), understory vegetation coverage (UVC), and litter biomass (LB)).
These findings indicate that vegetation restoration increases carbon sequestration while causing soil water deficit. Furthermore, stand density (SD) was established to make a predominant contribution to the dynamics of SWS and SCS via its effects in altering vegetation, soil, and litter characteristics. Therefore, high-density plantation forests in the Loess Plateau area should be appropriately thinned to reduce the density of forest stands on the basis of soil erosion control and wind and sand fixation, so as to increase carbon sink with lower water consumption, thus realizing the synergistic development of soil carbon sequestration and water connotation.
Earthworms exert a great impact on soil physical and chemical properties through feeding, burrowing, and casting activities. These activities can further affect soil erosion processes. However, we ...have insufficient knowledge on the effects of earthworm activities on soil erosion. In this study, we quantified the effects of earthworm activities on soil water distribution, runoff rate, and soil erosion rate under three slope gradients (5°, 10°, and 15°) through a laboratory‐simulated rainfall experiment. The uniform rainfall intensity (80 mm h−1) was set, and the rainfall duration after runoff generation was set to 60 min. Results showed that earthworm increased soil water infiltration and soil water storage (SWS). The increments in SWS were 41.2, 24.0, and 34.9 mm, respectively, in the tanks with earthworms at the slope gradients of 5°, 10°, and 15°, which were 93%, 51%, and 70% higher than the values of the control plots (21.3, 15.9, and 20.5 mm). Compared with the control plots, earthworm activities reduced the runoff rate at slope gradients of 5°, 10°, and 15° by 70%, 13%, and 39%, respectively; and increased soil erosion rate at slope gradients of 10° and 15° by 42% and 46%, respectively. Through their feeding, burrowing, and casting activities, earthworm increased soil water infiltration, reduced surface runoff, and increased soil erosion. This study provides insights into the effects of soil animals on soil erosion processes, and these data could then be incorporated into existing soil erosion simulation models or provide a basis for new models.
Earthworm eaten leaf litter and exposed soil surface to raindrops.
Earthworm casts changed the microtopography, and provided sediment source.
Earthworm tunnels promoted water infiltration and increased soil water storage.
Earthworm activities complicated the runoff and erosion processes.
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