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Plant species play a crucial role in mediating the activity and community structure of soil microbiomes through differential inputs of litter and rhizosphere exudates, but we have a poor understanding of how plant species influence comammox Nitrospira, a newly discovered ammonia oxidizer with pivotal functionality. Here, we investigate the abundance, diversity, and community structure of comammox Nitrospira underneath five plant species and a bare tidal flat at three soil depths in a subtropical estuarine wetland. Plant species played a critical role in driving the distribution of individual clades of comammox Nitrospira, explaining 59.3% of the variation of community structure. Clade A.1 was widely detected in all samples, while clades A.2.1, A.2.2, A.3 and B showed plant species-dependent distribution patterns. Compared with the native species Cyperus malaccensis, the invasion of Spartina alterniflora increased the network complexity and changed the community structure of comammox Nitrospira, while the invasive effects from Kandelia obovata and Phragmites australis were relatively weak. Soil depths significantly influenced the community structure of comammox Nitrospira, but the effect was much weaker than that from plant species. Altogether, our results highlight the previously unrecognized critical role of plant species in driving the distribution of comammox Nitrospira in a subtropical estuarine wetland.

Initial assessment of landslide susceptible areas is important in designing landslide mitigation measures. This study, a part of our study on the developing a landslide spatial model, aims to identify landslide susceptible areas using hard soil depth. In here, hard soil depth, defined as the depth interpreted from cone penetration test where the tip resistance reaches up to 250 kg/cm2, was used to identify landslide susceptible areas in a relatively small mountainous region in the middle western Central Java where landslides frequently occur. To this end, hard soil depth was interpolated using two different methods: inverse distance weighting and ordinary kriging (OK). The method producing the least errors and the most similar data distribution was selected. The result shows that OK is the best fitting model and exhibits clear pattern related to the recorded landslide sites. From interpolated hard soil depth in the landslide sites, it can be surmised that landslide susceptible areas are places possessing hard soil depth of 2.6–13.4 m. This finding is advantageous for policy makers in planning and designing efforts for landslide mitigation in middle western Central Java and should be applicable for other regions.

Purpose Earthworms play a critical role in soil ecosystem functions through the cycling of organic matter and nutrients. However, some land uses or environmental conditions are more favorable habitats for them than others. Thus, the objectives of this study were to evaluate the prevalence of earthworm density and its relationship to land uses and soil properties. Methods The study was conducted in three districts (Wangdue Phodrang, Chhukha and Dagana) in Bhutan in three land uses (organic fields - OrgF, conventional fields - ConF and natural vegetation - NatV) under three altitudes (high-, mid- and low-altitudes) and three soil depths. Results Overall, earthworm density at high-altitude was significantly ( P  < 0.001) higher than that at mid- and low-altitude sites. Further, across altitudes and soil depths, OrgF sites had a significantly ( P  < 0.001) higher earthworm density (120 earthworms m − 2 ) compared to that in the NatV (56 earthworms m − 2 ) and ConF (43 earthworms m − 2 ) sites, and the density decreased significantly ( P  < 0.001) and successively with the increase in soil depth. The coefficient of determination ( R 2  ≥ 0.51; P  < 0.001) showed a positive and moderate relationship between the earthworm density with soil organic C and total N in OrgF sites, but the relationship was weak ( R 2  ≤ 0.22) in the ConF or none in the NatV sites. Conclusions Substituting chemical fertilizers with organic manures could increase earthworm density by enhancing soil health through the cycling of organic materials and nutrients in the soil. The findings demonstrate empirical evidence for earthworm prevalence in different land use types across altitudinal gradients and provide valuable decision-making insights to land users and policymakers alike.

The propagation of meteorological droughts to soil droughts poses a substantial threat to water resources, agricultural production, and social systems. Understanding drought propagation process is crucial for early warning and mitigation, but mechanisms of the propagation from meteorological drought to soil drought, particularly at varying soil depths, remain insufficiently understood. Here, we employ the maximum correlation coefficient method and the random forest (RF) model to investigate the spatiotemporal patterns and drivers of propagation time (PT) from meteorological drought to soil drought at four different depths across China from 1980 to 2018. Our findings reveal consistently higher PT in northern China and lower PT in southern China across varying soil depths, with more pronounced spatial heterogeneity with increasing soil depth. Furthermore, we identify temperature and precipitation as determinants of spatial patterns of PT in surface and deeper soil layers, respectively. Additionally, precipitation emerges as the dominant factor influencing changes in PT between different soil layers. Our study highlights a discernible shift in PT drivers from temperature to precipitation as soil depth increases and the significant impact of precipitation on exacerbating spatial heterogeneity in PT. This study contributes to an enhanced comprehension of the propagation process from meteorological drought to soil drought at different depths, which can aid in establishing practical drought mitigation measures and early warning systems.

This study examines the spatial distribution of soil types and their susceptibility to erosion and accumulation processes in a study area in Slovakia. Field research involving 71 probes identified various soil types, with Regosols and Cutanic Luvisols being predominant. The study found that erosion-accumulation processes were detected in 69.97% of the probes, with changes observed in soil horizons. Soil analysis revealed different relations between soil depth, humus thickness, and terrain characteristics such as slope, slope length, and slope length and steepness factor (LS factor). Specifically, we confirmed a moderately strong positive correlation between soil depth and humus thickness ( = 0.597, = 71, < 0.001). Shallow soils (0–30 cm) exhibited a very strong positive correlation between soil depth and humus horizon thickness ( = 0.978, = 33, < 0.001). Conversely, no relationship was found in moderately deep soils (30–60 cm) ( = 0.018, = 14, < 0.948). For deep soils, we identified a moderately strong positive correlation ( = 0.345, = 24, = 0.098). While slope and slope length showed relationships with soil depth and humus thickness, the LS factor did not exhibit a clear correlation. These findings underscore the importance of understanding soil dynamics in informing land management practices, especially in areas susceptible to erosion. Recommendations include continued monitoring of eroded soils and implementing erosion control measures to maintain soil health and sustainability in agricultural production amidst climate change challenges.

Cropping systems comprising winter catch crops followed by spring wheat could reduce N leaching risks compared to traditional winter wheat systems in humid climates. We studied the soil mineral N (Ninorg) and root growth of winter- and spring wheat to 2.5 m depth during 3 years. The roots of the winter and spring wheat penetrated the soil at a similar rate (1.3 mm oC day⁻¹) and by virtue of its longer growing period, winter wheat reached depths of 2.2 m, twice that of spring wheat (1.1 m). The deeper rooting of winter wheat was related to much lower amounts of Ninorg left in the 1 to 2.5 m layer after winter wheat (81 kg Ninorg ha⁻¹ less). When growing winter catch crops before spring wheat, N content in the 1 to 2.5 m layer after spring wheat was not different from that after winter wheat. The results suggest that due to its deep rooting, winter wheat may not lead to as high levels of leaching as it is often assumed in humid climates. Deep soil and root measurements (below 1 m) in this experiment were essential to answer the questions we posed.

Soil freeze depth (SFD) is an important indicator of cryospheric and climate change. Changes in SFD have important effects on hydrology, the energy balance, carbon exchange, and ecosystem diversity. However, quantifying and predicting SFD at large scales remains a challenge due to sparse long-term observations. This study employs the Stefan solution combined with 16 of the coupled model inter-comparison project phase 5 (CMIP5) models over the historical period (1850–2005) and three representative concentration pathways (RCP 2.6, 4.5, and 8.5) for 2006–2100, the Climatic Research Unit dataset (1901–2013), and hundreds of soil temperature, air temperature, precipitation, and snow depth sites to analyze the spatiotemporal variability of SFD in Eurasia under historical and projected climate change. During 1850–2005, a statistically significant SFD decrease of 0.49 ± 0.04 cm/decade is observed. Spatially, the biggest decreases are generally in Siberia and on the Tibetan Plateau. There is a projected decrease in 2006–2100 SFD of 4.58 ± 0.26, 1.85 ± 0.21, and 0.45 ± 0.18 cm/decade for RCP 8.5, 4.5, 2.6, respectively. These variations in SFD provide key insights into spatiotemporal changes in climate, and facilitate improved understanding of variation in frozen ground across Eurasia.

A field experiment was conducted in northeast China to examine the response of nitrogen cycling enzymes, that is, protease, N‐acetyl‐β‐D‐glucosaminidase (NAG), amidase, urease, and peptidase, as well soil organic nitrogen (SON) fractions and their relationships to RT (no maize residue application), NT (no tillage with maize residues placed on the surface), TT (plow maize residues into the soil at 0–35 cm depth in the first year, 0–20 cm in the second year, and 0–15 cm in the third year), and PT (plow maize residues into soil at 0–35 cm depth). The results have shown that NT significantly enhanced the activities of protease and NAG at 0–10 cm soil depth in comparison with other treatments. NT and TT significantly enhanced the activities of protease compared to RT and PT at 10–20 cm soil depth. TT significantly enhanced the activities of NAG in comparison with RT at 10–20 cm soil depth. TT and PT significantly enhanced the activities of NAG and peptidase compared to RT and NT at 20–35 cm soil depth. PT significantly increased the activities of protease in comparison with RT at 20–35 cm soil depth. NT, TT, and PT significantly enhanced the activities of peptidase compared to RT at 10–20 cm soil depth. NT significantly increased the concentration of hydrolyzable NH4+‐N$$ {\\mathrm{NH}}_4^{+}\\hbox{-} \\mathrm{N} $$ in comparison with other treatments at 0–10 cm soil depth. PT significantly enhanced the concentration of hydrolyzable NH4+‐N$$ {\\mathrm{NH}}_4^{+}\\hbox{-} \\mathrm{N} $$ and amino acid N compared to other treatments at 20–35 cm soil depth. Redundancy analysis showed that protease played a crucial role in the cycling of SON under RT and NT, whereas peptidase and NAG played a significant role in the cycling of SON under TT and PT, respectively. This study provided a comprehensive understanding of crop residue return methods for regulating soil N cycling. To deepen our understanding of soil nitrogen cycling under different crop residue managements in northeast China, we conducted a field experiment with different maize residue incorporation methods and examined nitrogen cycling enzymes and organic nitrogen fractions, besides, the correlations between nitrogen cycling enzymes and organic nitrogen fractions were also explored. The results indicates that soil nitrogen cycling under different crop residue managements were regulated by different nitrogen cycling enzymes.

The stoichiometry of carbon, nitrogen, and phosphorus (C:N:P) among leaves, stems, and roots reflects trade-offs in plants for acquiring resources and their growth strategy. The widely distributed plant Alhagi sparsifolia is an ideal species to study the ecological stoichiometry in different organs in response to the availability of nutrients and water in the desert ecosystem. However, which response of organs is most sensitive to environmental conditions is still unclear. To answer this question, we collected samples of plants and soils including not only aboveground leaves and stems, but also underground roots and soils from a wide range of arid areas during the growing season. The C, N, P, C:N, C:P, and N:P ratios in leaves, thorns, stems, and roots were derived to explore their relationship as well as their response mechanisms to nutrients and water spanning 1 m deep in the soil. The results showed that the order of N concentration was leaves > thorns > stems > roots, that the concentration of P in the leaves, thorns, and stems was similar, and that their values were higher than those in the roots. First, the C:N ratios in the leaves and stems were significantly positively correlated with the ratio in roots. The C:N ratios in each organ showed a significant relationship with the soil alkali hydrolyzable nitrogen (SAN) above a depth of 60 cm. In addition to SAN, soil available phosphorus (SAP) and soil organic carbon (SOC) affect the C:N ratio in the roots. Second, the C:P and N:P ratios in aboveground organs showed no correlations with the ratios in roots. The C:P and N:P ratios in the leaves and thorns have no relationship with soil nutrients, while the C:P ratio in roots was influenced by SAN and SOC in all soil layers. Finally, the N:P ratios in roots were also affected by nutrients in different soil depths at 0–20 and 60–80 cm. These results illustrate that the roots were more sensitive to soil nutrients than the aboveground parts. Our study of ecological stoichiometry also suggests a novel systematic approach for analyzing the sensitivity of responses of an organ to environmental conditions.

Forests can prevent and/or mitigate hydrogeomorphic hazards in mountainous landscapes. Their effect is particularly relevant in the case of shallow landslides phenomena, where plants decrease the water content of the soil and increase its mechanical strength. Although such an effect is well known, its quantification is a relatively new challenge. The present work estimates the effect of some forest species on hillslope stability in terms of additional root cohesion by means of a model based on the classical Wu and Waldron approach (Wu in Alaska Geotech Rpt No 5 Dpt Civ Eng Ohio State Univ Columbus, USA, 1976; Waldron in Soil Sci Soc Am J 41:843–849, 1977). The model is able to account for root distribution with depth and nonsimultaneous root breaking. Samples of European beech (Fagus sylvatica L.), Norway spruce (Picea abies (L.) Karst.), European larch (Larix decidua Mill.), sweet chestnut (Castanea sativa Mill.) and European hop-hombeam (Ostrya carpinifolia Scop.), were taken from different locations of Lombardy (Northern Italy) to estimate root tensile strength, the Root Area Ratio and the root cohesion distribution in the soil. The results show that, in spite of its dramatic variability within the same species at the same location and among different locations, root cohesion can be coherently interpreted using the proposed method. The values herein obtained are significant for slope stabilisation, are consistent with the results of direct shear tests and back-analysis data, and can be used for the estimation of the stability of forested hillslopes in the Alps.