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As an important means of near-natural management in secondary forests, thinning effectively enhances the growth status of forest trees, and increases the overall forest yield and carbon sequestration capacity of the forest floor through rational stand regulation. This study focused on subtropical secondary broadleaf forests in the mountainous regions of western Zhejiang, China, and involved three treatment groups: a high-intensity thinning group (HT) (retaining trees with a diameter greater than 8 cm and removing shrub-layer vegetation), a low-intensity thinning group (LT) (retaining trees with a diameter greater than 5 cm and removing shrub-layer vegetation), and a control plot (no thinning treatment) (CK). The study aimed to investigate the effects of different thinning intensities on forest carbon stocks, soil respiration, and soil environmental factors, as well as to assess how thinning modifications impact the carbon sequestration capacity of the forest floor. The results illustrate the following: (1) The biomass growth and carbon sequestration capacity of individual trees under HT were significantly greater compared to other treatment groups. Conversely, carbon stock growth in the arboreal layer was higher under LT than under other treatments. (2) Thinning operations increased soil carbon stocks and improved soil fertility. (3) High-intensity (HT) and low-intensity thinning (LT) increased the soil moisture in both the surface and subsurface layers, with HT showing the highest levels. (4) One year after thinning, the soil organic matter (SOM) increased significantly, rising by 30.86% in HT and 21.84% in LT compared to CK. (5) In comparison to LT and CK, HT showed a significant increase in soil respiration rates, which led to higher CO2 and N2O emissions from the soil while also suppressing CH4 uptake. The study concludes that LT can enhance carbon sequestration in both the tree and soil layers, improve soil fertility, and reduce greenhouse gas emissions. This supports the sustainable development of forest ecosystems and effective carbon management. [ABSTRACT FROM AUTHOR]

This study aimed to provide a theoretical basis for the scientific fertilization and soil improvement of Castanea mollissima plantation.High-throughput sequencing and bioinformatic analysis were employed in the rhizosphere soil microorganisms of Castanea mollissima plantations in Donglan County, Tiane County, the Institute of Forestry, Long’ an County, and Pingle County in Guangxi, to determine soil bacterial and fungal community structures, diversity, and relationships with soil environmental factors.The results showed that the soil environmental factors, microbial community structures, and diversity differ in different regions in Guangxi. Overall, the worst soil environmental quality performance was observed in the Donglan County Castanea mollissima plantation.The dominant bacterial phyla across the regions included Acidobacteriota and Proteobacteria with more than 50% of the relative abundance of the bacteria, whereas the dominant fungal phyla were Basidiomycota and Ascomycota which made up over 95% of the relative fungal abundance, and the dominant microbial genera varied significantly in different Castanea mollissima plantations.Pearson and redundancy analysis correlation analysis indicated that soil microbial community structure, species richness, and diversity were associated with soil environmental factors, whereas soil urease activity as the primary factor significantly and positively affected the microbial community Shannon, Chao1 and ACE indices (P ＜0.05). Meanwhile, soil urease activity showed a significant correlation with the relative abundance of the dominant groups of the bacterial communities including Acidobacteria and Rhizomicrobium, and the dominant groups of the fungal communities including Basidiomycota, Ascomycota, Russula, Gyroporus, Inocybe and Clavulina (P＜0.05). In addition, soil available phosphorus and potassium content were significantly and positively correlated with the bacterial community ACE index (P＜0.05). Soil available potassium content was also an important factor affecting the change of microbial community structure in the rhizosphere soil of Castanea mollissima.In summary, soil urease activity was a key driver influencing the changes in microbial community structure, diversity and relative abundance of dominant microflora in the rhizosphere soil of Castanea mollissima in Guangxi. [ABSTRACT FROM AUTHOR]

The soil NO3− concentration and N2O emissions plays a crucial role in mitigating greenhouse gas emissions and minimizing greenhouse soil degradation concurrently. However, it is essential to understand the extent to which management practices and environmental factors influence the reduction in NO3− concentration and N2O emissions in greenhouse soils. Here, we conducted a meta-analysis, compiling a database of NO3− concentration and N2O emissions in response to either nitrogen or irrigation management in greenhouse vegetable-based systems in China. In summary, controlling the amount of total nitrogen application and irrigation water within specific ranges can effectively reduce both the greenhouse NO3− concentration and N2O emissions. Compared to chemical nitrogen management, the application of slow-release fertilizer could concurrently reduce the soil NO3− concentration and N2O emissions by 0.20 and 0.36 times, respectively. Positive relationships were observed between soil NO3− concentration and N2O emissions under conditions of higher soil organic carbon (OC), total nitrogen (TN), alkali-hydrolyzed nitrogen (AN), and pH, as well as a lower soil temperature (ST) and bulk weight (BW). Under conditions with a higher OC and pH, an appropriate nitrogen application rate is more effective in reducing N2O emissions. While increasing irrigation can reduce soil NO3− concentrations, it also raises the risk of significant NO3− leaching. Overall, nitrogen and irrigation management should be tailored to local soil physicochemical properties to concurrently regulate soil NO3− concentrations and N2O emissions in greenhouse environments. [ABSTRACT FROM AUTHOR]

Heavy-metal contamination in agricultural soil, particularly of cadmium (Cd), poses serious threats to soil biodiversity, rice production, and food safety. Soil microbes improve soil fertility by regulating soil organic matter production, plant nutrient accumulation, and pollutant transformation. Addressing the impact of Cd toxicity on soil fungal community composition, soil health, and rice yield is urgently required for sustainable rice production. Vermicompost (VC) is an organic fertilizer that alleviates the toxic effects of Cd on soil microbial biodiversity and functionality and improves crop productivity sustainably. In the present study, we examined the effects of different doses of VC (i.e., 0, 3, and 6 tons ha−1) and levels of Cd stress (i.e., 0 and 25 mg Cd kg−1) on soil biochemical attributes, soil fungal community composition, and fragrant-rice grain yield. The results showed that the Cd toxicity significantly reduced soil fertility, eukaryotic microbial community composition and rice grain yield. However, the VC addition alleviated the Cd toxicity and significantly improved the soil fungal community; additionally, it enhanced the relative abundance of Ascomycota, Chlorophyta, Ciliophora, Basidiomycota, and Glomeromycta in Cd-contaminated soils. Moreover, the VC addition enhanced the soil's chemical attributes, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), and microbial biomass C and N, compared to non-VC treated soil under Cd toxicity conditions. Similarly, the VC application significantly increased rice grain yield and decreased the Cd uptake in rice. One possible explanation for the reduced Cd uptake in plants is that VC amendments influence the soil's biological properties, which ultimately reduces soil Cd bioavailability and subsequently influences the Cd uptake and accumulation in rice plants. RDA analysis determined that the leading fungal species were highly related to soil environmental attributes and microbial biomass C and N production. However, the relative abundance levels of Ascomycota, Basidiomycota, and Glomeromycta were strongly associated with soil environmental variables. Thus, the outcomes of this study reveal that the use of VC in Cd-contaminated soils could be useful for sustainable rice production and safe utilization of Cd-polluted soil. [ABSTRACT FROM AUTHOR]

Background: To effectively understand and evaluate plant diversity in a specific area and make meaningful comparisons between regions, standardized methods that measure diversity irrespective of survey plot size are crucial. This study proposes a model equation for comparing plant species diversity using the modified Whittaker plots. Plant species diversity was measured in two Gotjawal areas on Jeju Island, where the coexistence of northern and southern limit species significantly impacts diversity. By analyzing the relationship between plant species diversity and environmental factors, the study clarified the characteristics of plant and habitat diversity in the Gotjawal ecosystem. Results: The species richness of vascular plants, herbaceous plants, and woody plants increased with area and was higher in Jeoji Gotjawal than in Seonheul Gotjawal. Similarly, the species turnover rate (slope value) was higher in Jeoji Gotjawal (4.37) than in Seonheul Gotjawal (3.85). This indicates that the species richness in Jeoji Gotjawal increases more with the expansion of the survey area (1-1,000 m2), reflecting a faster species turnover rate. Additionally, in Gotjawal areas, species richness increased with greater leaf litter depth, elevation, slope, and rock ratio. These results indicate that differences in plant species diversity were attributed to soil environmental factors. Conclusions: The plant species diversity of Gotjawal, surveyed using standardized methods, was lower than that of forested areas in the central region of South Korea where the same method was applied. Most previous studies on species diversity likely compared diversity without considering a consistent survey area. Therefore, when comparing plant species diversity domestically and globally, it emphasizes the need for the use of standardized survey methods.

Soil carbon and nitrogen pools are crucial for maintaining the balance of carbon and nitrogen cycling in ecosystems and also for reducing the impacts of global climate change. However, current research lacks an understanding of the effects of long-term vegetation restoration on soil carbon and nitrogen pools and their storage in vulnerable ecosystems. Therefore, we studied the characteristics of soil carbon (soil organic carbon, microbial biomass carbon, dissolved organic carbon) and nitrogen pools (total nitrogen, ammonium nitrogen, nitrate nitrogen) and their storage under four types of vegetation restoration (Stipa bungeana Trin., SB; Caragana korshinskii Kom., CK; Xanthoceras sorbifolia Bunge., XS; Picea asperata Mast., PA) in the Longzhong Loess Plateau area. We found that the carbon and nitrogen pools in the 0–40 cm soil layer under the XS and PA vegetation restoration types were higher compared to those under the SB and CK vegetation, and the values of soil ammonium–nitrogen ratios ranged from 0.72 to 0.83 under different vegetation types. Carbon and nitrogen interactions were stronger in the 0–40 cm soil under PA vegetation, which had significantly higher soil carbon (49.06 t·ha−1) and nitrogen (1.78 t·ha−1) storage than did the other vegetation types. We also found that soil carbon and nitrogen stores differed among different types of vegetation restoration. These elements were mainly distributed in soils from 0 to 20 cm depth, where the carbon and nitrogen pools in soils from 0 to 10 cm exceeded those in the lower layers. Furthermore, we discovered that redundancy analysis (RDA) supported by soil enzyme activity and physical properties significantly explained the variation in soil carbon and nitrogen triggered by vegetation restoration. According to this research, the stability and transformation of soil carbon and nitrogen pools in the region can be influenced by various forms of vegetation restoration. Additionally, the findings highlight that forest vegetation restoration can be a successful strategy for effectively sequestering soil carbon and nitrogen within the Longzhong Loess Plateau area. [ABSTRACT FROM AUTHOR]

Soil salinization is the main factor that threatens the growth and development of plants and limits the increase of yield. It is of great significance to study the key soil environmental factors affecting plant root traits to reveal the adaptation strategies of plants to saline-alkaline-stressed soil environments. In this study, the root biomass, root morphological parameters and root mineral nutrient content of two alfalfa cultivars with different sensitivities to alkaline stress were analyzed with black soil as the control group and the mixed saline-alkaline soil with a ratio of 7:3 between black soil and saline-alkaline soil as the saline-alkaline treatment group. At the same time, the correlation analysis of soil salinity indexes, soil nutrient indexes and the activities of key enzymes involved in soil carbon, nitrogen and phosphorus cycles was carried out. The results showed that compared with the control group, the pH, EC, and urease (URE) of the soil surrounding the roots of two alfalfa cultivars were significantly increased, while soil total nitrogen (TN), total phosphorus (TP), organic carbon (SOC), and α-glucosidase activity (AGC) were significantly decreased under saline-alkaline stress. There was no significant difference in root biomass and root morphological parameters of saline-alkaline tolerant cultivar GN under saline-alkaline stress. The number of root tips (RT), root surface area (RS) and root volume (RV) of AG were reduced by 61.16%, 44.54%, and 45.31%, respectively, compared with control group. The ratios of K+/Na+, Ca2+/Na+ and Mg2+/Na+ of GN were significantly higher than those of AG (p < 0.05). The root fresh weight (RFW) and dry weight (RDW), root length (RL), RV and RT of alfalfa were positively regulated by soil SOC and TN, but negatively regulated by soil pH, EC, and URE (p < 0.01). Root Ca2+/Na+ ratio was significantly positively correlated with soil TN, TP and SOC (p < 0.01). The absorption of Mg and Ca ions in roots is significantly negatively regulated by soil β-glucosidase activity (BGC) and acid phosphatase activity (APC) (p < 0.05). This study improved knowledge of the relationship between root traits and soil environmental factors and offered a theoretical framework for elucidating how plant roots adapt to saline-alkaline stressed soil environments. [ABSTRACT FROM AUTHOR]

Kadsura coccinea is a perennial vine medicinal plant, and its growth, development, and authentic medicinal qualities are affected by growing habitat, rhizosphere soil, and endophytic fungi. In order to explore the composition and diversity of fungal community in K. coccinea under different habitats, as well as their correlations with soil environmental factors, the rhizosphere and root endophytic fungi of K. coccinea from three different habitats in Guizhou were studied based on Illumina high-throughput sequencing method. The results were as follows: (1) Under three habitats, the number of OTU detected in rhizosphere soil (3 867) was much more than that in root endophyte (801). The common OTU of rhizosphere soil was 72, which were annotated to 5 phyla and 49 genera, most of which were ascomycetes. At the genus level, the proportions of Mortierella, Exophiala, and Cylindrocarpon were relatively high. The common OTU of root endophytic fungi was 14, which were annotated to 2 phylums and 11 genera. Ascomycetes (13, accounting for 92.9%) were overwhelmingly dominant. At the genus level, Mortierella, Exophiala, Cylindrocarpon and Nectria were dominant genra. There were only 6 OTU in total, annotated to 2 phylums and 5 genera, and the ascomycetes phylum (5, accounting for 83.3%) were the dominant phylum. At the genus level, Exophiala (2, 33.3%) accounted for the highest proportion and the rest were Mortierella, Cylindrocarpon and Nectria, respectively. Alpha diversity analysis showed that the diversity and richness of fungal communities in rhizosphere soil were significantly higher than those in root endophytic fungi, while the diversity of fungi under wild habits was higher than that under cultivated habits. (2) At the phylum level, the main endophytic fungal groups under three habitats were Ascomycota and Basidiomycota, accounting for 88.28% of the total flora. At the genus level, the community structures of endophytic fungi in rhizosphere and root were significantly different under different habitats. The endophytic fungi flora in the root had a certain preference under the cultivation habitat, while the evenness under the wild habitat was higher than that under cultivation habitat. The prediction functions of fungal community based on FUNGuild showed that pathotroph-saprotroph type in the root endophytic fungi was relatively high under the cultural habit, while the proportion of saprophytic type and symbiotroph type was relatively high under the wild habit. (3) Soil environmental factors had different effects on root endophytic fungi and rhizosphere fungi in K. coccinea. Total potassium (TK) and total phosphorus (TP) in soil were positively correlated with Shannon index and Simpson index of endophytic fungi in K. coccinea root; whereas, soil organic matter (SOM), total nitrogen (TN) and available nitrogen (AN) were positively correlated with Ace index and Chao1 index of rhizosphere soil fungi. In conclusion, SOM, TN and AN are the main soil environmental factors affecting the rhizosphere soil fungal community of the K. coccinea.

Amidst urbanization and industrialization in China, abandoned farmland plays a crucial role in safeguarding plant diversity within agricultural landscapes. This study aimed to examine the patterns of seasonal variation in plant diversity within abandoned farmland habitats in the Huang–Huai Plain region. Nonparametric tests were employed to analyze plant species diversity and phylogenetic diversity across seasons. Redundancy analysis and linear regression were conducted to examine the associations between plant species composition, species diversity, phylogenetic diversity, and soil environmental factors. Our results showed that plant species diversity, richness, and phylogenetic diversity were highest in spring, followed by summer, and lowest in autumn. The phylogenetic structure of plant communities demonstrated a tendency to diverge in spring, become random in summer, and cluster in autumn. Soil available potassium and soil organic matter emerged as important factors influencing plant species composition. The content of soil organic matter and ammonium nitrogen level exhibited a significantly positive correlation with the species diversity and phylogenetic diversity of plants. This study underscores the significance of considering seasonal and temporal scales when investigating plant diversity and provides a theoretical basis for biodiversity conservation in agricultural landscapes. [ABSTRACT FROM AUTHOR]

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Copyright of Guihaia is the property of Guihaia Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The crop rotation periodicity has always been a concern of agricultural researchers. This study was the first investigation on the effects of long-term continuous cultivation with rice/cherry tomato rotation on soil microbial community diversity. The main objective was to analyze the optimal rotation years of rice/cherry tomato from a micro-ecology perspective so as to provide theoretical basis for effectively avoiding continuous cropping obstacles of cherry tomato. Soil samples were collected from the surface layers with rice/cherry tomato rotations for 1 year (1a), 3 years (3a), 5 years (5a), 7 years (7a) and 10 years (10a). The microbial community diversity was determined via high-throughput sequencing. The results showed that alpha diversity of soil microbial communities was the highest at 5a and then gradually decreased during 5a to 10a. Beta diversity results revealed that microbial community structure was significantly different among 1a, 3a to 7a and 10a, but there were no clear differences among 3a, 5a and 7a. The abundances of soil beneficial bacteria Gemmatimonadetes, Bacteroidetes, Chloroflexi, Nitrospirae and beneficial fungi Mortierella, Trichoderma, Penicillium were the highest at 5a or 7a. Those of soil pathogenic fungi Fusarium and Aspergillus were the lowest at 5a and 7a, respectively. However, the relative abundances of the above-mentioned beneficial microorganisms began to decline, while those of pathogenic fungi began to increase after 5a or 7a. Soil available phosphorus, available iron and available zinc were common important factors affecting the community structure of bacteria and fungi, as indicated by significant positive correlations between the environmental factors and microbial communities. In conclusion, the soil microbial diversity began to decline and the micro-ecological balance was broken after continuously planting 5a to 7a with rice/cherry tomato rotation, which would lead to new continuous cropping obstacles. [ABSTRACT FROM AUTHOR]

Heavy-metal contamination in agricultural soil, particularly of cadmium (Cd), poses serious threats to soil biodiversity, rice production, and food safety. Soil microbes improve soil fertility by regulating soil organic matter production, plant nutrient accumulation, and pollutant transformation. Addressing the impact of Cd toxicity on soil fungal community composition, soil health, and rice yield is urgently required for sustainable rice production. Vermicompost (VC) is an organic fertilizer that alleviates the toxic effects of Cd on soil microbial biodiversity and functionality and improves crop productivity sustainably. In the present study, we examined the effects of different doses of VC (i.e., 0, 3, and 6 tons ha−1) and levels of Cd stress (i.e., 0 and 25 mg Cd kg−1) on soil biochemical attributes, soil fungal community composition, and fragrant-rice grain yield. The results showed that the Cd toxicity significantly reduced soil fertility, eukaryotic microbial community composition and rice grain yield. However, the VC addition alleviated the Cd toxicity and significantly improved the soil fungal community; additionally, it enhanced the relative abundance of Ascomycota, Chlorophyta, Ciliophora, Basidiomycota, and Glomeromycta in Cd-contaminated soils. Moreover, the VC addition enhanced the soil’s chemical attributes, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), and microbial biomass C and N, compared to non-VC treated soil under Cd toxicity conditions. Similarly, the VC application significantly increased rice grain yield and decreased the Cd uptake in rice. One possible explanation for the reduced Cd uptake in plants is that VC amendments influence the soil’s biological properties, which ultimately reduces soil Cd bioavailability and subsequently influences the Cd uptake and accumulation in rice plants. RDA analysis determined that the leading fungal species were highly related to soil environmental attributes and microbial biomass C and N production. However, the relative abundance levels of Ascomycota, Basidiomycota, and Glomeromycta were strongly associated with soil environmental variables. Thus, the outcomes of this study reveal that the use of VC in Cd-contaminated soils could be useful for sustainable rice production and safe utilization of Cd-polluted soil.

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Summary: N-enriched biochar can increase the accumulation of carbon (C), nitrogen (N), phosphorus (P), and biomass in rice plants. On the other hand, the biomass and C, N, and P contents of plant organs are important indicators to reflect plant C, N, and P storages. We established control, 4 t ha−1, and 8 t ha−1 N-enriched biochar treatment plots in a subtropical paddy field in China to investigate the effect of these treatments on C, N, and P storages, ecological stoichiometry in various rice plant organs, and their relationships with edaphic factors. The application of N-enriched biochar increased the biomass and storages of C, N, and P in rice roots, stems, leaves, and grains, mainly at 4 t ha−1. The application of N-enriched biochar decreased the C/N and C/P ratios of rice organs, but increased their N/P ratio. Changes in C/N were mainly due to the changes in storage, while N/P was positively correlated with N storage of stems, leaves, and grains and negatively correlated with P storage in roots. Pearson's correlation analysis revealed that pH was negatively correlated, and soil N content was positively correlated with P storage in various organs of rice. In addition, soil P content and chlorophyll were positively correlated with N storage. In conclusion, we found that the application of N-enriched biochar improved plant N and P storage and stoichiometrical relations among rice organs. [ABSTRACT FROM AUTHOR]

This study employed Illumina MiSeq high-throughput sequencing to explore the composition of the bacterial community of Chagan Lake sediments and its response to soil physicochemical properties. Our findings indicated that bacterial abundance and diversity are significantly correlated with water depth. Particularly, the bacterial alpha diversity and phyla relative abundance increased with water depth. Furthermore, the five dominant bacterial phyla in the bacterial community according to all plots were Proteobacteria, Chloroflexi, Acidobacteriota, and Actinobacteriota. Moreover, our findings indicated that electrical conductivity (EC), pH, and total carbon (TC) in sediments are important factors that affect the bacterial community structure and diversity of sediments. In summary, the bacterial community structure and diversity varied significantly in different plot sediments of Chagan Lake, which were regulated by soil nutrients and physical properties. The results of this study can be used to further explore the potential relationship between bacterial communities and the environment, and provide a scientific basis for the prediction of ecosystem structure and function of alpine inland wetlands. [ABSTRACT FROM AUTHOR]

In order to explore the soil environmental quality and herbaceous plant characteristics of different land in Shanghai land consolidation area. In this paper, the soil environmental quality and distribution characteristics of herbaceous plants were investigated for four types land: farmland, garden, forest and construction land. Characteristics and their relationship to soil factors. The results showed that: (1) The comprehensive grade of soil quality geochemistry was forest > farm > garden > construction, and the soil nutrients in the garden were not balanced; (2) The herbaceous plants were mainly Compositae and Gramineae, and the degree of species differentiation was relatively high. (3) The species richness index of herbaceous plants is highest in forest and lowest in farm, but the biodiversity is highest in garden and lowest in forest, indicating that due to the influence of forest type and canopy closure, the quality of forest in the survey area is not uniform. (4) The correlation analysis between herb diversity and soil factors showed that: hydrolyzable nitrogen in soil was significantly positively correlated with Shannon-Wiener diversity index and Simpson index, but not significantly correlated with most heavy metals, indicating that hydrolyzable nitrogen was an important factor affecting the investigation, and heavy metals are not limiting factors for herbs. Abundance (S) was significantly positively correlated with available potassium in soil, Pielou index was significantly positively correlated with arsenic. Therefore, the soil should be properly improved with organic fertilizers, and invasive plants should be removed in time, which is conducive to the growth of herbaceous plant communities and the stability of biodiversity. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shenyang Agricultural University is the property of Journal of Shenyang Agricultural University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Graphene oxide (GO), a carbon nanomaterial that is widely used in the environment and other industries, may pose potential risks to ecosystems, especially the soil ecosystem. Some soils in Northeast China are frequently polluted with cadmium (Cd) metal. However, there is no study on the influence of GO on the Cd-contaminated soil microbial community and soil chemical properties. In this study, Cd (100 mg kg−1)-polluted soils were treated with different concentrations of GO (0, 25, 50, 150, 250, and 500 mg L−1, expressed as T1, T2, T3, T4, T5, and T6, respectively) for 40 days. The treatment without Cd pollution and GO served as the control (CK). Then, we investigated the influence of the GO concentrations on the bacterial community and chemical properties of Cd-polluted Haplic Cambisols, the zonal soil in Northeast China. After GO addition, the richness and diversity indexes of the bacterial community in Cd-contaminated Haplic Cambisols initially increased by 0.05–33.92% at 25 mg L−1, then decreased by 0.07–2.37% at 50 mg L−1, and then increased by 0.01–24.37% within 500 mg L−1 again. The species and abundance of bacteria varied with GO concentration, and GO significantly increased bacterial growth at 25 and 250 mg L−1. GO treatments influenced the bacterial community structure, and the order of similarity of the bacterial community structure was as follows: T4 = T5 > T1 = T6 > T2 > T3 > CK. Proteobacteria and Acidobacteria were the dominant bacteria, accounting for 36.0% and 26.2%, respectively, of soil bacteria. Different GO treatments also significantly affected the metabolic function of bacteria and further influenced the diversity of the bacterial community structure by affecting several key soil chemical properties: soil pH, organic matter and available potassium, phosphorus, and cadmium. Our results provide a theoretical basis for scientific and comprehensive evaluation of the environmental impacts of GO on the zonal forest soils of Northeast China. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination in soil-rice systems has become a global public concern. However, influencing factors and the contamination threshold of Cd in soils remain largely unknown owing to soil heterogeneity, which limits our ability to assess the risk to human health and to draft appropriate environmental policies. In this study, we selected the soil-rice system of Longtang and Shijiao town in southern China, which was characterized by multi-metal acidic soil contamination due to improper electronic waste recycling activities, as a case to analyze the influence of different soil properties on the Cd threshold in the soil and Cd accumulation in rice. The results showed that soil organic matter (SOM) was the main factor regulating Cd accumulation in the soil-rice system. Moreover, compared with the total Cd concentration, the DTPA-extractable Cd concentration in the soil was a better predictor of Cd transportation in the soil-rice system. According to the prediction model, when SOM was < 35 g kg−1, the CdDTPA threshold was 0.16 mg kg−1 with a 95% likelihood of Cdrice accumulation above the Chinese food standard limit (0.2 mg kg−1). Conversely, when SOM was ≥ 35 g kg−1, the CdDTPA threshold was only 0.03 mg kg−1. This study of the influence of SOM on Cd accumulation in a soil-rice system confirms that SOM is a crucial parameter for better and safer rice production, especially in multi-metal contaminated acidic soils.

Plant functional traits reflect the responses and adaptations of plants to their immediate environment. In this study, 10 different sources of the Houttuynia cordata population in Anhui Province, China, were examined in terms of their leaf responses and adaptive mechanisms towards soil characteristics. Our study observed the leaf weight ratio depicted a significant negative correlation with leaf potassium content (r=-0.652, P < 0.05) and an extremely significant negative correlation with leaf saturated water content (r=-0.720, P < 0.01) in different H. cordata populations. The leaf mass per area, leaf weight ratio, leaf nitrogen content, leaf potassium content, and leaf saturated water content in H. cordatas showed a significant correlation with soil available phosphorus, available potassium, soil total porosity, soil volume weight, and pH. Lastly, a significant relationship between leaf potassium content in plants and soil volume weight was observed (R2=0.448, P < 0.01).

This study was to explore the diversity of rhizosphere and endophytic microbial communities and the correlation with soil environmental factors of Stipa purpurea on the Qinghai-Tibetan Plateau. The bacterial phylum of Proteobacteria, Firmicutes and Bacteroidota, and the fungal phylum of Ascomycota, Basidiomycota and Zygomycota were dominant in microbial communities of S. purpurea in all three sampling sites. Multiple comparison analysis showed that there were significant differences in the composition of microbial communities in the roots, leaves and rhizosphere soil. Whether it is fungi or bacteria, the OTU abundance of rhizosphere soils was higher than that of leaves and roots at the same location, while the difference among locations was not obvious. Moreover, RDA analysis showed that Zygomycota, Cercozoa, Glomeromycota, Chytridiomycota and Rozellomycota possessed strongly positive associations with altitude, dehydrogenase, alkaline phosphatase, neutral phosphatase, available kalium and available phosphate, while Ascomycota was strongly negatively associated. Changes in ammonium nitrate, alkaline phosphatase, polyphenol oxidase, total phosphorus, and altitude had a significant impact on the bacterial communities in different habitats and altitudes. Taken together, we provide evidence that S. purpurea has abundant microbial communities in the alpine grassland of the Qinghai-Tibetan Plateau, whose composition and diversity are affected by various soil environmental factors.

Plant functional traits reflect the responses and adaptations of plants to their immediate environment. In this study, 10 different sources of the Houttuynia cordata population in Anhui Province, China, were examined in terms of their leaf responses and adaptive mechanisms towards soil characteristics. Our study observed the leaf weight ratio depicted a significant negative correlation with leaf potassium content (r=-0.652, P < 0.05) and an extremely significant negative correlation with leaf saturated water content (r=-0.720, P < 0.01) in different H. cordata populations. The leaf mass per area, leaf weight ratio, leaf nitrogen content, leaf potassium content, and leaf saturated water content in H. cordatas showed a significant correlation with soil available phosphorus, available potassium, soil total porosity, soil volume weight, and pH. Lastly, a significant relationship between leaf potassium content in plants and soil volume weight was observed (R2=0.448, P < 0.01). [ABSTRACT FROM AUTHOR]

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In this study, we took the shrub plants of different slopes in Guilin karst hills as the research object. The relationship between species diversity(species richness index, Shannon-Wiener index and Pielou evenness index)of shrubs and soil environmental factors along with sloped(shady-sunny)gradients in the karst hills of Guilin were analyzed. Our results were as follows:(1)Soil water content, soil temperature, soil pH and soil total phosphorus have significant effects on plant community types and species distribution, and aspect has a very significant impact on plant communities and species distribution. Soil total nitrogen, soil available nitrogen and soil organic carbon had no significant effects on plant community types and species distribution.(2)Except for the Pielou evenness index, the difference between the shady slope and the sunny slope was not significant, species richness index and Shannon-Wiener index had significant differences in different slope microhabitats. Among them, the species richness index and the Shannon-Wiener index showed the same trend in different slopes, that is, the shady slope was larger than the sunny slope.(3)Except for the difference between soil pH and soil total phosphorus content was not significant, the slope aspect had a significant impact on soil water content, soil temperature, soil total nitrogen content, soil available nitrogen content, and soil organic carbon content. Among them, soil water content, soil available nitrogen and soil organic carbon content were shady slope greater than the sunny slope, while soil temperature and soil total nitrogen content were shady slope less than the sunny slope.(4)Multiple stepwise regression analysis showed that on the shady slope, effects of soil environmental factors on species richness index, Shannon-Wiener index and Pielou evenness index were not significant. On the sunny slope, there was a significantly negative correlation between species richness index and soil temperature, and a significantly positive correlation with soil organic carbon content; Shannon-Wiener index was significantly positively correlated with soil water content and soil organic carbon content; Pielou evenness index was significantly positively correlated with soil organic carbon content and negatively correlated with soil total phosphorus content. [ABSTRACT FROM AUTHOR]

Saline water has proven to be one of the alternative sources of freshwater for agricultural irrigation in water-scarce areas. However, the changes in farmland ecology caused by saline water irrigation remain unclear. In this study, six irrigation water salinities (CK: 1.3 dS m−1, S1: 3.4 dS m−1, S2: 7.1 dS m−1, S3: 10.6 dS m−1, S4: 14.1 dS m−1, S5: 17.7 dS m−1) were set in a three-year (2019, 2021–2022) experiment to investigate their effects on soil environment and greenhouse gas emissions in cotton fields under long-term saline water irrigation. Results show that soil salinity in the same layer increased as increasing water salinity. Soil moisture of S3–S5 increased significantly by 4.99–12.94%. There was no significant difference in soil organic matter content between CK and S1. Saline water irrigation increased soil ammonium nitrogen content by 0.57–49.26%, while decreasing nitrate nitrogen content by 1.43–32.03%. Soil CO 2 and N 2 O emissions and CH 4 uptake were lower in S1–S5 than in CK at different cotton growth stages. In addition, saline water irrigation reduced the global warming potential by 6.93–53.86%. A structural equation model was developed to show that soil salinity, moisture, and ammonium nitrogen content were negatively correlated with global warming potential, while organic matter and nitrate nitrogen had positive effects on global warming potential. Considering the comprehensive perspectives of gas emissions and cotton yield, irrigation water with salinity less than 10.6 dS m−1 could effectively reduce greenhouse gas emissions from cotton fields while maintaining stable cotton yields in the experimental area and similar region. [Display omitted] • SWI increased soil salinity, moisture, and NH+ 4 -N, but decreased SOM and NO− 3 -N. • SWI decreased soil CO 2 and N 2 O emissions, CH 4 uptake rates, GWP, and GHGI. • SWI with salinity less than 10.6 dS m−1 mitigated GHGs without reducing cotton yield. [ABSTRACT FROM AUTHOR]

• The growth of malus robusta Rehd. was better than that of M9T337. • The metabolic activity of soil microorganisms of malus robusta Rehd. is strong. • The number of soil fungi in malus robusta Rehd. was small, and the beneficial bacteria were enriched. • Malus robusta Rehd. has a good effect on the improvement of replanted soil environment. • Malus robusta Rehd. is more suitable than M9T337 as rootstock for ARD control. Apple replant disease (ARD) seriously restricts the development of the apple industry. It is of great significance for the sustainable development of the apple industry to alleviate ARD by using rootstock resistance. Taking M9T337 and Malus robusta Rehd. as test materials, the differences in biomass, soil physical and chemical properties, soil enzyme activity, soil microbial metabolic activity and carbon source utilization characteristics, soil microbial quantity, and soil fungal community of two apple rootstocks in replanted soil. The results showed that the biomass, related soil enzyme activities, and AWCD metabolic activity of apple saplings with Malus robusta Rehd. as rootstock were better, the number of soil fungi and the copy number of four Fusarium genes were lower, and more beneficial bacteria were enriched. In conclusion, the apple saplings with Malus robusta Rehd. as rootstock have a better improvement effect on the replanted soil environment and are more suitable as rootstocks to prevent and control ARD than M9T337. [ABSTRACT FROM AUTHOR]

Quantitative inversion of soil quality is a hot topic in soil science and environmental science research, but it is difficult to obtain high-precision soil spectrum information without attachment interference. Therefore, we carried out pot experiment after testing the soil. And then based on the synergistic changes between soil quality and plants, the entropy theory and spectral vegetation indices were used to construct a parameter model of soil environmental factors and plant spectrum at different growth stages with the aid of the spectral integration of hyperspectral imaging and visualization. Parameters of plant spectrum characteristics were used to achieve the goal of indirectly indicating soil quality. The research finds that the characteristic spectral bands of plants lie near 450, 500, 520, 550, 670, 730 and 800nm. As the plant growth progressed, its spectral reflectivity gradually decreased, the red edge slope and red edge position of plant also manifested a blue shift phenomenon. Inversion is better conducted during the jointing period and MCARI/OSAVI is the optimal vegetation index. The model based on the entropy theory (r = 0.917, sig < 0.01) has higher inversion accuracy than the average spectral vegetation index model (r = 0.829, sig < 0.05) which indicates that the dual judgment model based on entropy theory and spectral vegetation index better facilitates the remote sensing monitoring research on soil quality. This research is the preliminary application of indirect inversion soil quality and condition through hyperspectral imaging technique and a result from potting and monoculture. Thus, the model still need to be tested further in order to improve its universality. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the microbial diversity and community composition under saline soil and to screen the salt-tolerant microbial flora from salinization habitats. The soil from three different habitats(primary salinization, secondary salinization, and healthy soil) in Hebei Province were sampled. The convention method and high-throughput sequencing technology were used to examine the physicochemical properties and microorganism diversity. The soil chemical properties of the three habitats were significantly different. Compared with those of field soil, the soil OM, AP, AK, TS, and EC values of greenhouse soil and TS and EC values of coastal saline soil were significantly higher. However, other chemical indexes of coastal saline soil were significantly lower. The diversity index and abundance of soil bacteria in greenhouse soil were the highest, followed by those in field soil and coastal saline soil as the lowest. The diversity index and abundance of fungi in two saline habitats were significantly lower than that in field soil. The community structure of saline soil was analyzed at the phylum and genus levels. Chloroflexi and its genera and Ascomycota and its genera, such as Trichocladium and Fusarium, were the dominant microbial groups in saline soil. EC and TS were the main factors affecting microbial diversity and community composition. EC and TS were positively correlated with unclassified&#95; A4b , unclassified&#95; Chloroflexi , unclassified&#95; α -Proteobacteria, Trichocladium , unclassified&#95; Chaetomiaceae , Crassicarpon , Cephaliophora , and Sodiomyces . The results of this study lay the foundation for future research on screening microbial resources needed for saline soil remediation.

Soil biogeochemical cycles are largely mediated by microorganisms, while fire significantly modifies biogeochemical cycles mainly via altering microbial community and substrate availability. Majority of studies on fire effects have focused on the surface soil; therefore, our understanding of the vertical distribution of microbial communities and the impacts of fire on nitrogen (N) dynamics in the soil profile is limited. Here, we examined the changes of soil denitrification capacity (DNC) and denitrifying communities with depth under different burning regimes, and their interaction with environmental gradients along the soil profile. Results showed that soil depth had a more pronounced impact than the burning treatment on the bacterial community size. The abundance of 16S rRNA and denitrification genes ( narG, nirK, and nirS) declined exponentially with soil depth. Surprisingly, the nosZ-harboring denitrifiers were enriched in the deeper soil layers, which was likely to indicate that the nosZ-harboring denitrifiers could better adapt to the stress conditions (i.e., oxygen deficiency, nutrient limitation, etc.) than other denitrifiers. Soil nutrients, including dissolved organic carbon (DOC), total soluble N (TSN), ammonium (NH), and nitrate (NO), declined significantly with soil depth, which probably contributed to the vertical distribution of denitrifying communities. Soil DNC decreased significantly with soil depth, which was negligible in the depths below 20 cm. These findings have provided new insights into niche separation of the N-cycling functional guilds along the soil profile, under a varied fire disturbance regime. [ABSTRACT FROM AUTHOR]

Climate change is expected to cause the alteration of litter production in forests, which may result in substantial changes in soil CO efflux (FCO) process as litter represents a major pathway of carbon from vegetation to the soils. In this study, we conducted an aboveground litter manipulation experiment to examine the influence of litter addition and exclusion on soil FCO in Camphor tree, Masson pine, and mixed Camphor tree and Masson pine forests in central south China. Litter input manipulation included three treatments: non-litter input (litter exclusion), double litter input (litter addition), and natural litter input (control). On average, litter exclusion significantly reduced soil FCO rate by approximately 39%, 24% and 22% in Camphor tree forests, the Mixed forests, and Masson pine forests, respectively. On a yearly basis, double litter addition significantly increased soil CO by 12% in the Mixed forests ( P=0.02) but not in both Camphor tree and Masson pine forests ( P>0.05), when compared with their corresponding control treatments. However, litter addition increased soil FCO rates in the months of June-August in Camphor tree and Masson pine forests, coinciding with high soil temperature of summer conditions. Litter exclusion reduced soil FCO more than litter addition increased it in the study sites. Responses of soil respiration to litter input treatments varied with forest types. Litter input treatments did not alter the seasonal patterns of soil temperature and soil water content. Our results indicated that changes in aboveground litter as a result of global climate change and/or forest management have a great potential to alter soil respiration and soil carbon balance in forest ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Production of nitrous oxide (N2O) by anaerobic denitrification is one of the most important processes in the global nitrogen (N) cycle and has attracted recent attention due to its significant impacts on climatic change. Fire is a key driver of many ecosystem processes, however, how fire drives the shift in microbial community and thus alters nutrient cycling is still unclear. In this study, a 35-year-old repeated prescribed burning trial, with three treatments (no burning, 2 yearly burning and 4 yearly burning), was used to explore how the long-term repeated prescribed burning affects N2O flux, key soil properties (inorganic N, dissolved organic carbon (DOC) and N, pH, electrical conductivity (EC), moisture), denitrification gene abundance and their interactions. Soil samples were collected in January and April 2011. Quantitative real-time PCR was employed to quantify the gene copy number of target genes, including narG, nirK, nirS and nosZ. In situ N2O fluxes ranged from 0 to 8.8 g N2O–N ha−1 h−1 with an average of 1.47 g N2O–N ha−1 h−1. More frequent fire (2 yearly burning) significantly reduced soil N2O fluxes, availability of C and N substrates and moisture, but increased soil pH and EC compared with no burning and 4 yearly burning treatments. Fire treatments did not significantly affect the abundance of most denitrification genes. There were no significant differences in most parameters measured between the 4 yearly burning and no burning treatments, indicating microbial community function is not affected by less frequent (4 year interval) burning. Variation in the N2O fluxes among the treatments can largely be explained by soil substrate (, DOC and total soluble nitrogen (TSN)) availability and soil environmental factors (pH, EC, and moisture), while the abundance of most denitrification genes were not related to the N2O fluxes. It is concluded that soil environmental factors rather than denitrification gene abundance control N2O fluxes in this wet sclerophyll forest in response to long-term repeated fires. [Copyright &y& Elsevier]

This study addressed the effects of land use and slope position on soil inorganic nitrogen and was conducted in small watersheds. The study covered three land use types: tropical cloud forest, grassland, and coffee crop. To conduct this research, typical slope small watersheds were chosen in each land use type. Slopes were divided into three positions: shoulder, backslope, and footslope. At the center of each slope position, soil sampling was carried out. Soil inorganic nitrogen was measured monthly during a period of 14 months (July 2005–August 2006) with 11 observations. Significant differences in soil NH–N and NO–N content were detected for both land use and sampling date effects, as well as for interactions. A significant slope position-by-sampling date interaction was found only in coffee crop for NO–N content. In tropical cloud forest and grassland, high soil NH–N and low NO–N content were recorded, while soil NO–N content was high in coffee crop. Low NO–N contents could mean a substantial microbial assimilation of NO–N, constituting an important mechanism for nitrogen retention. Across the entire land use set, the relationship between soil temperature and soil inorganic N concentration was described by an exponential decay function ( N = 33 + 2459exp, R = 0.44, P < 0.0001). This study also showed that together, soil temperature and gravimetric soil water content explained more variation in soil inorganic N concentration than gravimetric soil water content alone. [ABSTRACT FROM AUTHOR]

This study was to explore the diversity of rhizosphere and endophytic microbial communities and the correlation with soil environmental factors of Stipa purpurea on the Qinghai-Tibetan Plateau. The bacterial phylum of Proteobacteria, Firmicutes and Bacteroidota, and the fungal phylum of Ascomycota, Basidiomycota and Zygomycota were dominant in microbial communities of S. purpurea in all three sampling sites. Multiple comparison analysis showed that there were significant differences in the composition of microbial communities in the roots, leaves and rhizosphere soil. Whether it is fungi or bacteria, the OTU abundance of rhizosphere soils was higher than that of leaves and roots at the same location, while the difference among locations was not obvious. Moreover, RDA analysis showed that Zygomycota, Cercozoa, Glomeromycota, Chytridiomycota and Rozellomycota possessed strongly positive associations with altitude, dehydrogenase, alkaline phosphatase, neutral phosphatase, available kalium and available phosphate, while Ascomycota was strongly negatively associated. Changes in ammonium nitrate, alkaline phosphatase, polyphenol oxidase, total phosphorus, and altitude had a significant impact on the bacterial communities in different habitats and altitudes. Taken together, we provide evidence that S. purpurea has abundant microbial communities in the alpine grassland of the Qinghai-Tibetan Plateau, whose composition and diversity are affected by various soil environmental factors. [ABSTRACT FROM AUTHOR]

Increased anthropogenic activities and global warming have accelerated the loss of wetlands worldwide. Given that a seed bank plays an important role in maintaining species diversity, understanding the regulatory mechanism of seed bank dynamics is crucial for using seed banks for restoration of species diversity in degraded wetlands. We collected data on biotic (i.e., aboveground vegetation, birds and rodents) and abiotic (i.e., soil environmental factors) ecosystem components as predictors along a degradation gradient in an alpine wetland and then to identify the relative importance of multiple sets of predictors in the regulating seed bank dynamics (i.e., species richness and composition). Seed bank dynamics were less responsive to environmental change than the aboveground vegetation during wetland degradation. Soil moisture and bird richness were more important than other predictors in regulating species richness and species composition of the seed bank, respectively. Our results suggest that seed banks can be used as potential resources for restoration of degraded wetlands. Birds play an important role in regulating the diversity of wetland ecosystems (seed bank is a potential diversity provider). Therefore, more attention should be paid to the protection of bird diversity in the process of conservation and restoration of degraded wetlands. • Seed banks can buffer the vegetation dynamic response to environmental change. • Seed bank dynamics are regulated by multiple ecosystem components. • Soil moisture and bird richness regulate seed bank diversity and composition. [ABSTRACT FROM AUTHOR]

• Clear-cut and forest regeneration increased soil N 2 O emission in a Chinese fir plantation. • Overall regeneration increased soil N 2 O emission compared to natural regeneration. • Clear-cut and forest regeneration increased soil N 2 O emission by increasing soil temperature, labile C and N concentrations. • Soil temperature was the most important factor on soil N 2 O emission. Forest regeneration after clear-cut has been practiced extensively to establish a new stand. However, the effects of forest regeneration on soil N 2 O emission and the related changes in soil environment factors have been rarely examined in managed plantation forests. A 21-month field trial was conducted to investigate the effects of two different regeneration practices following clear-cut on soil N 2 O emission and related environmental factors in a Cunninghamia lanceolata plantation. The trial included three treatments, clear-cut and natural regeneration (CN), clear-cut and artificial overall regeneration (CAO), and uncut control (UC). Compared with the control, CN, and CAO increased cumulative soil N 2 O emissions (P < 0.05) by 76%, and 170%, respectively. Soil N 2 O fluxes were positively (P < 0.05) correlated with soil temperature, moisture, microbial biomass C and N, NO 3 −-N, water-soluble organic C and N, and NH 4 +-N concentrations. We conclude that clear-cut and associated natural regeneration (CN) increased N 2 O fluxes due to the increased soil temperature, and the increased concentrations of NO 3 −-N, microbial biomass C and N, and water-soluble organic C and N; and artificial overall regeneration increased soil N 2 O fluxes due to the increased concentrations of soil NO 3 −-N, microbial biomass C and N. The results highlighted that artificial overall regeneration with higher soil disturbance intensity in clear-cut stands would exacerbate soil N 2 O emission. [ABSTRACT FROM AUTHOR]

Biochar is often applied to paddy soils as a soil improver, as it retains nutrients and increases C sequestration; as such, it is a tool in the move towards C-neutral agriculture. Nitrogen (N) fertilizers have been excessively applied to rice paddies, particularly in small farms in China, because N is the major limiting factor for rice production. In paddy soils, dynamic changes in iron (Fe) continuously affect soil emissions of methane (CH 4) and carbon dioxide (CO 2); however, the links between Fe dynamics and greenhouse gas emissions, dissolved organic carbon (DOC), and rice yields following application of biochar remain unclear. The aims of this study were to examine the effects of two rates of nitrogen (N)-enriched biochar (4 and 8 t ha−1 y−1) on paddy soil C emissions and storage, rice yields, and Fe dynamics in subtropical early and late rice growing seasons. Field application of N-enriched biochar at 4 and 8 t ha−1 increased C emissions in early and late rice, whereas application at 4 t ha−1 significantly increased rice yields. The results of a culture experiment and a field experiment showed that the application of N-enriched biochar increased soil Fe 2+ concentration. There were positive correlations between Fe 2+ concentrations and soil CO 2 , CH 4 , and total C emissions, and with soil DOC concentrations. On the other way around, these correlations were negative for soil Fe 3+ concentrations. In the soil culture experiment, under the exclusion of plant growth, N-enriched biochar reduced cumulative soil emissions of CH 4 and CO 2. We conclude that moderate inputs of N-rich biochar (4 t ha−1) increase rice crop yield and biomass, and soil DOC concentrations, while moderating soil cumulative C emissions, in part, by the impacts of biochar on soil Fe dynamics. We suggest that water management strategies, such as dry-wet cycles, should be employed in rice cultivation to increase Fe2+ oxidation for the inhibition of soil CH 4 and CO 2 production. Overall, we showed that application of 4 t ha−1 of N-enriched biochar may represent a potential tool to improve sustainable food production and security, while minimizing negative environmental impacts. [Display omitted] • Application of N-enriched biochar favors the soil conversion of Fe3+ to Fe2+. • Can be a tool to improve fertilization efficiency and yield in a C neutral scenario. • At 8 t ha−1 promoted gaseous C emissions in paddy soil without yield improvement. • At 4 t ha−1 increased yield and decreased the C gas emissions in culture experiments. • Fe2+ content was positively correlated with DOC content, CO 2 and CH 4 emissions. [ABSTRACT FROM AUTHOR]

The conversion of cropland to plantation is important ecological engineering in the Loess Plateau, China. Moreover, the extent of cropland abandonment and fallow is gradually increasing in this area, which probably affects the soil bacterial composition. Therefore, we applied Illumina MiSeq sequencing targeting the V3–V4 region of the 16S rRNA gene to analyze the bacterial community from different land-use types (cropland, plantation, cropland fallow and abandonment). The results showed that the plantation soil had the highest bacterial diversity. Biomarkers that strongly differentiated land-use types were found. The plantation, cropland fallow and abandonment were primarily associated with Proteobacteria , Nitrospirae , Acidobacteria , Firmicutes and Verrucomicrobia. The dominant populations from different land-use types had high similarity at the genus level, but there were still significant differences on the relative abundance of bacteria among some populations. Moreover, Pearson's correlations indicated that soil available phosphorus (SAP), soil available K (SAK) and vegetation biomass were the important factors affecting the bacterial community. These results suggested that bacterial community structure differed among different land-use types, which was closely related to soil environmental factors, such as SAP and SAK. • The soil bacterial community with land-use change was investigated. • Biomarkers that strongly differentiated land-use change were found. • SAP, SAK and vegetation biomass had important effects on soil bacterial community. [ABSTRACT FROM AUTHOR]

Changes in soil environmental factors and microbial communities of a precious tree species (Ormosia hosiei) plantation with different forest ages are still unclear. Obtaining this information can provide a theoretical basis for scientific forest management. Ormosia hosiei plantations of varying ages (7, 20, and 45 years old) were targeted in Zhejiang Province, China. We collected surface soil (0–20 cm) and analysed the diversity and structural characteristics of soil microbial communities by high-throughput sequencing. Redundancy analysis (RDA) and Spearman correlation analysis revealed soil environmental factors that cause differences in the microbial communities. The soil bacterial community diversity was not significantly affected by stand age, while the Chao and Ace indexes of the fungal community at 20 and 45 years were markedly higher than those at 7 years. The abundance of Proteobacteria in the 45 years was lower than those at 7 and 20 years, while the abundance of Actinobacteria at 7 years was lower than those at 20 and 45 years, and the abundance of Basidiomycota gradually increased with increasing stand age. The RDA and correlation analysis indicated that the soil microbial biomass carbon (MBC), bulk density (SBD), total porosity (STP), and total potassium (TK) were key factors that affected the bacterial communities and had a significant correlation with Actinobacteria. Soil temperature (T), available phosphorus (AP) and forest litter (FL) affected the fungal communities and had a significant correlation with Basidiomycota. In conclusion, forest age did not affect bacterial diversity, but the soil fungal community of the O. hosiei plantation in the middle-aged forest (20 years old) had the highest diversity; there were obvious differences in the composition and structure of soil microorganisms between different forest ages, which may be attributed to the phyla present (e.g., Proteobacteria , Actinobacteria , and Basidiomycota), which may be caused by differences in T, SBD, STP, AP, TK, MBC, and FL. • Forest age obviously changed the soil fungal community diversity. • The differences of soil microorganisms between different forest ages may be attributed to the phyla present. • Soil copiotrophic bacteria had the highest value at the middle-age forest. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination in soil-rice systems has become a global public concern. However, influencing factors and the contamination threshold of Cd in soils remain largely unknown owing to soil heterogeneity, which limits our ability to assess the risk to human health and to draft appropriate environmental policies. In this study, we selected the soil-rice system of Longtang and Shijiao town in southern China, which was characterized by multi-metal acidic soil contamination due to improper electronic waste recycling activities, as a case to analyze the influence of different soil properties on the Cd threshold in the soil and Cd accumulation in rice. The results showed that soil organic matter (SOM) was the main factor regulating Cd accumulation in the soil-rice system. Moreover, compared with the total Cd concentration, the DTPA-extractable Cd concentration in the soil was a better predictor of Cd transportation in the soil-rice system. According to the prediction model, when SOM was < 35 g kg−1, the Cd DTPA threshold was 0.16 mg kg−1 with a 95% likelihood of Cd rice accumulation above the Chinese food standard limit (0.2 mg kg−1). Conversely, when SOM was ≥ 35 g kg−1, the Cd DTPA threshold was only 0.03 mg kg−1. This study of the influence of SOM on Cd accumulation in a soil-rice system confirms that SOM is a crucial parameter for better and safer rice production, especially in multi-metal contaminated acidic soils. ga1 • Path analysis showed better identification of factors regulating Cd transportation. • SOM was the main factor regulating Cd accumulation in soil-rice systems. • Soil DTPA-extractable Cd concentration was predictive of Cd transportation. • The regional Cd DTPA threshold was 0.16 mg kg−1 with SOM <35 g kg−1. • The regional Cd DTPA threshold was 0.03 mg kg−1 with SOM ≥35 g kg−1. [ABSTRACT FROM AUTHOR]

Polygonum hydropiper is a phosphorus (P)-accumulating herb used for P-phytoextraction, with higher P-accumulating capability in the mining ecotype (ME) than the non-mining ecotype (NME). This difference might result from the variation in root-associated soil (rhizoplane, rhizosphere) bacterial characteristics. Thus, characteristics and influence factors of bacterial community were investigated in root-associated soils and bulk soils of both ecotypes of P. hydropiper in situ using high-throughput sequencing technique. Bacterial community diversity and richness were independent with ecotypes; rather it positively correlated with soil organic matter concentration. Forty-nine phyla were identified, with Proteobacteria being the most dominated phylum. Soil bacterial community compositions were primarily separated into clusters by ecotypes, simultaneously with great influence by soil groups and chemical properties. Rhizoplane and rhizosphere bacterial communities showed more similarity compared with those in bulk soil. Soil pH, available P, available nitrogen and available potassium played major roles in shaping the bacterial community compositions. The genera Halomonas , Flavisolibacter , Blastocatella , Thiobacillus , Sphingomonas and Bacillus in ME root-associated soils showed higher abundance than in NME root-associated soils, positively with soil available P concentration, suggesting these genera might be important in mobilizing soil mineral-P and facilitating P uptake for the ME of P. hydropiper. • Bacterial community in root-associated soil of P. hydropiper was tested in situ. • Bacterial composition rather than diversity was affected by ecotype and soil group. • Proteobacteria was the dominant phylum in root-associated soil of P. hydropiper. • Soil pH, AN, AP, and AK played major roles in shaping bacterial community structure. • Higher P-accumulating ability in ME might be related to its six abundant genera. [ABSTRACT FROM AUTHOR]