Soil Nutrient Elements Research Articles

Soil nitrogen-hydrolyzing enzyme activities respond differently to the freeze-thaw temperature and number of cycles

Soil nitrogen-hydrolyzing enzymes catalyzes a key rate-limiting step in regulating the circulation of soil nutrient elements. The response of soil nitrogen (N)-hydrolyzing enzyme activities to environmental changes has been investigated in different geographic scales or ecosystems. Global warming has increased the frequency of soil freeze-thaw (FT) events, resulting in drastic changes in soil enzyme activities. Clarifying the changes in soil N-hydrolyzing enzymes under freeze-thaw conditions is essential for improving the N cycling and utilization efficiency in soil. However, how soil N-hydrolyzing enzymes respond to FT remains unclear. This study was aimed to analyze the influence of FT on soil N-hydrolyzing enzyme activity in Mollisols. The results showed that soil physicochemical properties and enzyme activities were changed after freeze-thaw events, and freeze-thaw temperature (FTF) had a greater impact on these properties than the number of freeze-thaw cycles (FTC). Correlation analysis showed that total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and pH were the major factors affecting enzyme activities in FT events. Soil N-hydrolyzing enzyme activity was mainly regulated by environmental factors, which can directly and indirectly affect the soil enzyme activity. In the soil ecosystem, pH, TOC, TN and TP were important factors in counteracting damage to enzyme activity from FT effects and a suitable environment and adequate nutrients can limit damage to enzymes from FT events. The findings will better predictions the changing patterns of climate change on soil N-hydrolyzing enzyme activity.

Using coupled soil nutrients as dummy variables can improve the predictive performance of stand basal area growth model for subtropical Chinese fir plantations

Abstract Soil nutrient contents in ecosystems play a crucial role in forest growth and site productivity. We evaluated stand basal area growth in response to soil organic matters (OMs) and potassium in the plantations of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.]. Soil samples were collected from the top layer (0–20 cm) and dendrometric measurements were made in 150 subtropical Chinese fir plantations in Hunan Province. We carried out data analysis applying one-way variance analysis, dummy variables modeling, and K-means clustering methods. The results showed the following: (i) Available potassium (AK) was the most affecting factor, followed by OM. (ii) The predictive accuracy of the stand basal area growth model was substantially improved with coupled AK and OM used as dummy variables (AIC decreased from 820.6025 to 785.0356). (iii) In addition, the optimal nutrient type of group (SNECTG1, soil nutrient element combination type group) and soil factors affecting basal area growth and their range (OM 10 ~ 20 g kg−1 and AK 30 ~ 50 mg kg−1) were effectively explained. SNECTG1 had the greatest effect on stand basal area growth, resulting in the maximum potential productivity of 3.622 m2 ha−1 year−1 at a stand density index of 2826 and site index of 12 m. (iv) The stand basal area increments of middle-aged forest was the highest, followed by nearly mature forest, and mature forest. In summary, our stand basal area growth model can be used to predict stand increments under different site indices or soil nutrient scenarios, which can provide theoretical and practical guidance for the cultivation of large-diameter timber forests.

Microecological mechanisms of mountainous forest cultivated ginseng growth vigor and saponin accumulation, and the characterization of bionic microbial fertilizer.

A study on the soil microecological mechanisms influencing the growth vigor and saponin accumulation of mountainous forest cultivated ginseng (MFCG) under various forest types. Using MFCG from different forest types as experimental material, the correlation and functional analysis of MFCG growth vigor, ginseng saponin content, and soil nutrient elements in their rhizosphere were conducted to clarify the soil microecological mechanisms by which different forest types affect the growth vigor and saponin accumulation of understory ginseng. Based on these microecological mechanisms, a bionic microbial fertilizer was developed and characterized. The agronomic traits and saponin content (Re, Rc, Rb2, and Rb3) of MFCG in the Pinus sylvestris var. mongholica Litv. (PSV) group were significantly higher than those in the Quercus mongolica Fisch. ex Ledeb. (QMF) and Larix gmelinii (Rupr.) Kuzen (LGK) groups (p < 0.05). The total content of these four monomeric saponins in the PSV group was 35.1 and 45.56% higher than that in the QMF and LGK groups, respectively. Significant differences (p < 0.05) were observed between the PSV group and the QMF and LGK groups in terms of the rhizosphere soil microbial diversity and physicochemical indicators such as nutrient elements. The agronomic traits and saponin content of MFCG were positively correlated with chemical indicators in the rhizosphere soil, including Cu, Ca, Mg, Zn, B, Fe, Mo, Mn, Organic matter (OM), Available phosphorus (AP), Available nitrogen (AN), and Available potassium (AK). Based on the microbial diversity and nutrient elements positively correlated with MFCG in the rhizosphere soil, a bionic microbial fertilizer formula was optimized. The microecological mechanism behind the growth vigor and saponin accumulation of understory ginseng involves an increase in beneficial microorganisms and nutrient elements, along with a reduction in harmful microorganisms and detrimental elements. The bionic microbial fertilizer promoted MFCG growth and saponin accumulation while improving soil nutrient levels, bulk density, and water-holding capacity.

Nutrient and Trace Elements in Suburban Sugar Maple (Acer saccharum) Sap, Syrup, and Soils from Massachusetts, Connecticut, New Jersey, and Pennsylvania

Production of maple syrup from sugar maples (Acer saccharum) in suburban areas lies at the intersection of urban farming and forestry, providing an artisanal food as well as ecosystem services. However, urban areas can be enriched with trace elements due to industrial, agricultural, and municipal pollution, which can potentially affect sap and syrup chemistry. Here, we collected soils, sap, and maple syrup from four artisanal maple syrup producers in four suburban areas across the northeastern United States to assess nutrient and trace element concentrations. Soil As and Pb concentration approached or exceeded EPA limits while Cd, Cu, and Zn were far below EPA limits. Sap and syrup As, Cd, Ni, Pb, and Zn concentrations reached or exceeded FDA limits for food. However, Total Hazard Quotients suggest that urban maple syrup consumption poses low to no health risk to adults and children.

Ecological Stoichiometry Characteristics and Influencing Factors of Soil Carbon, Nitrogen, and Phosphorus in Green Spaces Along the Urban-to-Rural Gradient of Nanchang, China

Analyzing the soil carbon, nitrogen, and phosphorus content, along with their stoichiometric ratios across different urban-rural gradients, can offer essential insights into enhancing soil quality and the sustainable management of urban green space ecosystems. This study focused on Nanchang, China, examining two typical urban forest types (Pinus massoniana forests and Camphora officinarum forests), two typical urban wetlands types (river wetlands and pond wetlands), as well as urban natural and artificial grasslands. It analyzed the distribution characteristics of organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and their stoichiometric ratios along the “urban-suburban-rural” gradients in surface (0–20 cm) and deep (20–40 cm) soil. The results indicated that in the deep soil of Pinus massoniana forests, rural areas exhibited significantly higher SOC content compared to suburban areas. In the surface soil of Camphora officinarum forests, the TN content and N:P were significantly greater in urban areas compared to rural areas (p &lt; 0.05). Both soil layers in river wetlands showed significantly higher soil TN levels in urban areas compared to rural areas. Additionally, in the deep soil of pond wetlands, urban areas showed significantly greater TN content, C:P, and N:P, compared to rural areas (p &lt; 0.05). For natural grasslands, soil C:N was significantly more in suburban and rural areas than in urban areas for both soil layers. In artificial grasslands, the SOC content in deep soil was significantly greater in rural areas compared to urban areas (p &lt; 0.05). In the deep soil of suburban areas, soil TP content in Camphora officinarum forests was highly significantly greater than that in Pinus massoniana forests (p &lt; 0.01). The SOC, TN content, and C:P were considerably higher in pond wetlands compared to river wetlands (p &lt; 0.05). The SOC content of natural grasslands was significantly higher compared to artificial grasslands (p &lt; 0.05). Nitrate nitrogen was highly significantly and positively correlated with soil N:P in the deep soil of Pinus massoniana forests (p &lt; 0.01), and soil pH was highly significantly and negatively correlated with soil N:P in the surface soil of pond wetlands (p &lt; 0.01). The urbanization process has altered the SOC, TN, and TP nutrient status to some extent, exacerbating the imbalance of nutrient elements in green space soils along the “urban-suburban-rural” gradients.

Soil organic carbon contents and their major influencing factors in mangrove tidal flats: a comparison between estuarine and non-estuarine areas

BackgroundUnvegetated tidal flats of mangrove ecosystems in estuarine and non-estuarine areas play a crucial role in the coastal blue carbon sinks and biogeochemical cycle. However, there is still a lack of comprehensive understanding of the differences in soil organic carbon (SOC) contents in mangrove tidal flats between estuarine and non-estuarine areas, as well as their influencing factors.MethodsIn this study, soil samples were collected from estuarine and non-estuarine mangrove tidal flats in the Leizhou Peninsula. We compared the SOC and soil physicochemical properties between estuarine and non-estuarine mangrove tidal flats. The Random Forest algorithm was employed to identify the main influencing factors affecting SOC. The direct and indirect effects of the main influencing factors on SOC were studied using partial least squares structural equation modeling.ResultsSOC, total nitrogen (TN), total phosphorus (TP), available potassium (AK), clay, silt, aluminum (Al), lithium (Li), boron (B), molybdenum (Mo), and cadmium (Cd) contents in the estuarine areas were significantly higher than those in the non-estuarine areas of the mangrove tidal flats. The soil particle size (clay, silt, and sand), soil nutrient (TN and TP), and soil metal elements (Al, Mo, and Cd) were the main influencing factors of the SOC contents in the estuarine and non-estuarine mangrove tidal flat areas. Soil particle size (clay, silt, and sand) indirectly positively influenced SOC contents by positively influencing soil nutrient (TN and TP).ConclusionsOur findings indicate that estuarine tidal flats have higher capacity of SOC sequestration compared with non-estuarine tidal flats. The main cause is that soil particle size has the potential to significantly increase SOC content by increasing soil nutrients, while metal elements have a direct influence on SOC content. The findings of the present study highlight an important mechanism that influences SOC contents in estuarine and non-estuarine mangrove tidal flats.

Long-term intercropping shaped soil bacterial microbiome composition and structure of maize fields in a semiarid region

Long-term intercropping shaped soil bacterial microbiome composition and structure of maize fields in a semiarid region

Correlation Analysis of Soil Nutrients and Quality Index in Pepper Planting Areas

This study explores the correlation between soil nutrient elements and pepper fruit quality in Guizhou Province, highlighting regional variations in nutrient influence. Guizhou, with its unique mountainous and karst terrain, provides a distinct ecological environment for pepper cultivation. Our analysis of three major pepper-growing regions—Dafang, Guiyang, and Zunyi—demonstrates that the nitrogen, phosphorus, and potassium levels in the soil significantly impact pepper quality. Potassium plays a particularly vital role in fruit development, as deficiencies in potassium often result in flower and fruit drop and reduced yield. In Dafang, AP (available phosphorus) and TK (total potassium) were most closely linked to amino acids, reducing sugars, and capsaicinoid content, while in Bozhou, SAN (available nitrogen) was most influential, and in Qingzhen, TP (total phosphorus) and AK (available potassium) were predominant. The findings suggest that key soil elements, such as available phosphorus, available potassium, available nitrogen, and organic matter, influence the quality indicators—amino acids, reducing sugars, capsaicin, and dihydrocapsaicin—in pepper fruits. Further analysis indicates that Guizhou’s distinct soil composition significantly contributes to its peppers’ unique flavor profile. The combined effects of soil nutrients, pepper varieties, and cultivation practices underline the superior quality of Guizhou peppers. This study provides a foundation for understanding the soil–quality interaction and enhances the market recognition of Guizhou’s pepper varieties. Future research should investigate the integrated effects of environmental and soil factors to better assess Guizhou’s favorable growth conditions for peppers.

Organic matter accumulation encouraged K-strategy bacteria increase and metabolism variation in karst vegetation restoration

Organic matter accumulation encouraged K-strategy bacteria increase and metabolism variation in karst vegetation restoration

Ecological Stoichiometry of Multiple Nutrients in Leymus chinensis and Soils Subjected to Long-Term Saline-Sodic Stress in Western Jilin Province, China

Ecological Stoichiometry of Multiple Nutrients in Leymus chinensis and Soils Subjected to Long-Term Saline-Sodic Stress in Western Jilin Province, China

Rhizosphere microbial community construction during the latitudinal spread of the invader Chromolaena odorata

The colonization of alien plants in new habitats is typically facilitated by microorganisms present in the soil environment. However, the diversity and structure of the archaeal, bacterial, and fungal communities in the latitudinal spread of alien plants remain unclear. In this study, the rhizosphere and bulk soil of Chromolaena odorata were collected from five latitudes in Pu’ er city, Yunnan Province, followed by amplicon sequencing of the soil archaeal, bacterial, and fungal communities. Alpha and beta diversity results revealed that the richness indices and the structures of the archaeal, bacterial, and fungal communities significantly differed along the latitudinal gradient. Additionally, significant differences were observed in the bacterial Shannon index, as well as in the structures of the bacterial and fungal communities between the rhizosphere and bulk soils. Due to the small spatial scale, trends of latitudinal variation in the archaeal, bacterial, and fungal communities were not pronounced. Total potassium, total phosphorus, available nitrogen, available potassium and total nitrogen were the important driving factors affecting the soil microbial community structure. Compared with those in bulk soil, co-occurrence networks in rhizosphere microbial networks presented lower complexity but greater modularity and positive connections. Among the main functional fungi, arbuscular mycorrhizae and soil saprotrophs were more abundant in the bulk soil. The significant differences in the soil microbes between rhizosphere and bulk soils further underscore the impact of C. odorata invasion on soil environments. The significant differences in the soil microbiota along latitudinal gradients, along with specific driving factors, demonstrate distinct nutrient preferences among archaea, bacteria, and fungi and indicate complex microbial responses to soil nutrient elements following the invasion of C. odorata.

In the Qaidam Basin, Soil Nutrients Directly or Indirectly Affect Desert Ecosystem Stability under Drought Stress through Plant Nutrients.

The low nutrient content of soil in desert ecosystems results in unique physiological and ecological characteristics of plants under long-term water and nutrient stress, which is the basis for the productivity and stability maintenance of the desert ecosystem. However, the relationship between the soil and the plant nutrient elements in the desert ecosystem and its mechanism for maintaining ecosystem stability is still unclear. In this study, 35 sampling sites were established in an area with typical desert vegetation in the Qaidam Basin, based on a drought gradient. A total of 90 soil samples and 100 plant samples were collected, and the soil's physico-chemical properties, as well as the nutrient elements in the plant leaves, were measured. Regression analysis, redundancy analysis (RDA), the Theil-Sen Median and Mann-Kendall methods, the structural equation model (SEM), and other methods were employed to analyze the distribution characteristics of the soil and plant nutrient elements along the drought gradient and the relationship between the soil and leaf nutrient elements and its impact on ecosystem stability. The results provided the following conclusions: Compared with the nutrient elements in plant leaves, the soil's nutrient elements had a more obvious regularity of distribution along the drought gradient. A strong correlation was observed between the soil and leaf nutrient elements, with soil organic carbon and alkali-hydrolyzed nitrogen identified as important factors influencing the leaf nutrient content. The SEM showed that the soil's organic carbon had a positive effect on ecosystem stability by influencing the leaf carbon, while the soil's available phosphorus and the mean annual temperature had a direct positive effect on stability, and the soil's total nitrogen had a negative effect on stability. In general, the soil nutrient content was high in areas with a low mean annual temperature and high precipitation, and the ecosystem stability in the area distribution of typical desert vegetation in the Qaidam Basin was low. These findings reveal that soil nutrients affect the stability of desert ecosystems directly or indirectly through plant nutrients in the Qaidam Basin, which is crucial for maintaining the stability of desert ecosystems with the background of climate change.

Time scale effect of magnetic ferric oxide modified biochar in-situ remediation of arsenic-contaminated paddy soil

Time scale effect of magnetic ferric oxide modified biochar in-situ remediation of arsenic-contaminated paddy soil

Rapid and High-Performance Analysis of Total Nitrogen in Coco-Peat Substrate by Coupling Laser-Induced Breakdown Spectroscopy with Multi-Chemometrics

Nitrogen is an important nutrient element for crop growth. Rapid and accurate acquisition of nitrogen content in cultivation substrate is the key to precise fertilization. In this study, laser-induced breakdown spectroscopy (LIBS) was used to detect the total nitrogen (TN) of coco-peat substrate. A LIBS spectrum acquisition system was established to collect the spectral line signal of samples with wavelengths ranging from 200 nm to 860 nm. Synergy interval partial least squares (Si-PLS) algorithm and elimination of uninformative variables (UVE) algorithm were used to select the spectral data of TN characteristic lines in coco-peat substrate. Univariate calibration curve and partial least squares regression (PLSR) were used to build mathematical models for the relationship between the spectral data of univariate characteristic spectral lines, full variables and screened multi-variable characteristic spectral lines of samples and reference measurement values of TN. By comparing the detection performance of calibration curves and multivariate spectral prediction models, it was concluded that UVE was used to simplify the number of spectral input variables for the model and PLSR was applied to construct the simplest multivariate model for the measurement of TN in the substrate samples. The model provided the best measurement performance, with the calibration set determination coefficient () and calibration set root mean square error (RMSEC) values of 0.9944 and 0.0382%, respectively; the prediction set determination coefficient () and prediction set root mean square error (RMSEP) had values of 0.9902 and 0.0513%, respectively. These results indicated that the combination of UVE and PLSR could make full use of the variable information related to TN detection in the LIBS spectrum and realize the rapid and high-performance measurement of TN in coco-peat substrate. It would provide a reference for the rapid and quantitative assessment of nutrient elements in other substrate and soil.

Chemical and Microbial Differences of Root and Rhizosphere Soil among Different Provenances of Fokienia hodginsii

Aims: Fokienia hodginsii is a threatened conifer tree species, known as the dominant nursery-grown species capable of colonizing the challenging woodland environments in southern China due to its strong root penetrating ability. The ecological phenotype of Fokienia hodginsii is not well documented during its breeding process, which limits the potential planting area and its ecological function. This study aims to understand how Fokienia hodginsii associates with microbes to conduct its key ecological function and provide a theoretical basis for further improving the forest nursery management of Fokienia hodginsii. Methods: This study explored the ecological traits of 11 main Fokienia hodginsii provenances in a homogeneous garden experiment by analyzing their nutrient utilization strategies and associated microbial features in the rhizosphere soil and roots. Results: The study found that the paramount difference in the rhizosphere soil among provenances is in Ca and Fe content. Some microbial communities, namely Crenarchaeota, Verrucomicrobiota, and Desulfobacterota, were positively correlated with the amounts of the soil nutrient elements, whereas Abditibacteriota and Dependentiae were negatively correlated. The abundance of N- and Fe-related bacteria in the Fu Jian Chang Ting (FJCT) provenance was significantly higher than that in other provenances, while the C-, P-, K-, and Mg-related fungal communities, respectively, had higher abundances in the FJCT, Fu Jian Long Yan (FJLY), Fu Jian Gu Tian (FJGT), and Fu Jian Xian You (FJXY) provenances than the others. The impacts of the Gui Zhou Li Ping (GZLP), Hu Nan Dao Xian (HNDX), Jiang Xi Shang Yao (JXSY), and Guang Dong Shi Xing (GDSX) provenances on the rhizosphere soil are similar, but the differences in nutrient utilization arise from the plant itself. Conversely, the root nutrient contents of the FJCT, Fu Jian You Xi (FJYX), Fu Jian An Xi (FJAX), FJLY, Fu Jian De Hua (FJDH), FJGT, and FJXY provenances are highly correlated with soil nutrient features. Conclusions: For the native provenances, their economic traits are better than the exotic provenances. The native provenances are more sensitive to local soil conditions, so they should benefit more from human interventions, rendering them more suitable for artificial cultivation. The growth of the exotic provenances is less affected by the soil environment, making them better suited for the ecological transformation of forest stands and soil improvement.

Archaeal communities change responding to anthropogenic and natural treatments of freeze-thawed soils

Archaeal communities change responding to anthropogenic and natural treatments of freeze-thawed soils

Potassium and Magnesium in American Ginseng Roots as Key Factors in Monitoring Soil Quality, Yield, and Quality: Screening, Prediction, and Validation

Understanding the key roles of nutrient elements in soil–plant systems are essential for herbal medicine production and sustainable development. However, the ecological relationships between soil quality and nutrient elements, yield, saponins, or other active compounds in American ginseng remain unclear. In this study, 20 soil indicators, 10 root nutrient indicators, 9 quality indicators, and yields were investigated. The minimum dataset was constructed by principal component analysis, key factors were screened by correlation analysis and PLS-PM analysis, and the prediction model was constructed using linear fitting and tested by a validation test. The minimum dataset, constructed based on principal component analysis, comprised five indicators: SOM, TP, AK, AMg, and ACa. Correlation analysis, PLS-PM analysis, and linear fitting showed that K and Mg were the key factors relating soil quality to the yield and quality of American ginseng and that when AMg was 0.21 g/kg and AK was 0.30 g/kg, soil organic matter was 27%, total phosphorus was 1.19 g/kg in soil, K content in roots was 15.63 g/kg, Mg content was 1.91 g/kg, and the K/Mg of 8.85 could balance American ginseng yield and quality. In predicting and validating the model, predicting the DW, total ginsenoside, Rb1, Rb2, Rc, and Rd of American ginseng using K/Mg were reliable. This study provides a scientific basis for nutrient regulation, selecting planting sites, assessing soil quality, and predicting and evaluating American ginseng quality.

Influence of Decomposed Stubble Return on the Soil Microbial Community Under Perennial Crop Rotation

The aim of this study was to understand how the application of decomposed stubble return (DSR), a type of bio-organic fertilization, affects soil microbial communities under crop rotation. The changes in microbial composition and diversity related to DSR were investigated based on metagenomic sequencing and comparative analysis of two groups of soil samples after a 3-year tomato-pepper-papaya rotation: the DSR and no-DSR (i.e., without DSR) groups, with the soils before crop rotation as the control group. Inter-group comparisons of the crop performance (growth and yield) and physicochemical soil properties (pH value, nutrient elements, and heavy metals) were also conducted to reveal the effects of DSR application on the soil. The relative abundance of bacteria was higher than 90% in all soil samples. Proteobacteria and Actinobacteria in the DSR group and Proteobacteria and Firmicutes in the no-DSR group, whereas Acidobacteria and Proteobacteria in the control, were the two most abundant phyla. The abundance of Proteobacteria decreased, whereas that of Actinobacteria increased, in the DSR-amended soil compared to the no-DSR soil. At genus level, Acidobacterium dominated in the control and genera Pseudomonas, Burkholderia, and Bacillus in the no-DSR group, while Burkholderia, Pseudomonas, and Bacillus in the DSR-amended soil comprised the majority of their microbiomes. The DSR soil had higher microbial diversity and relative abundance of Ascomycota fungi than the no-DSR group after the crop rotation. Along with higher diversity of microbial community, more favorable soil pH, better crop growth, higher crop yields, higher abundance of soil nutrient elements, and lower accumulation of heavy metals in the soil were found in the DSR group compared to the no-DSR one. Furthermore, the DSR soil had more similarities with the control than with the No-DSR soil, in aspects of microbial composition and microbe-derived potential gene functions. It was indicated that decomposed stubble return may improve soil conditions or prevent them from degradation incurred by long-term crop cultivation. It was suggested that the application of the compost derived from fermented post-harvest plant residue may be a general strategy for developing more sustainable agricultural systems.

Variations in soil carbon, nitrogen, and phosphorus concentrations and stoichiometry with stand age in Acacia hybrid plantations in Southern Vietnam

Abstract. Chau M, Quy N, Xu X, Hung B, Cuong LV, Ngoan T, Nguyen T. 2024. Variations in soil carbon, nitrogen, and phosphorus concentrations and stoichiometry with stand age in Acacia hybrid plantations in Southern Vietnam. Biodiversitas 25: 565-573. Soil Carbon (C), Nitrogen (N), and Phosphorus (P) contents are the three most critical soil nutrient elements required for plant growth and development, and their ecological stoichiometric ratios are significant indicators for understanding soil nutrient balance and cycling. This study was conducted to probe variations in the soil organic C (SC), total N (SN), and total P (SP) contents and stoichiometry at five soil depths (0-20, 20-40, 40-60, 60-80, and 80-100 cm) in Acacia hybrid plantations of five different ages (2-, 4-, 6-, 8-, and 10-year-old plantations) in Langa-Dongnai Forestry Company, Southern Vietnam. The results showed that forest age and soil depth substantially impacted soil nutrient contents and their stoichiometric characteristics. The concentrations of SC, SN, and SP as well as C/N, C/P, and N/P ratios increased as the forest stand age increased. The contents of SC, SN, and SP reduced with soil depth, indicating an obvious soil “surface-aggregation” phenomenon. The nutrient restriction varied based on forest stand development, shifting from restricted nitrogen in the earlier growth periods of trees to restricted phosphorus in the later growth periods. The findings demonstrate that to resolve the issue of restricted availability of these nutrient indexes, additional nitrogen should be supplied during earlier growth periods and additional phosphorus during later growth periods. The results further emphasize the importance of understanding SC, SN, and SP interactions and nutritional limitations and provide relevant theoretical support for sustainable Acacia hybrid plantation management in the Southern region.

Biochar and organic fertilizer applications enhance soil functional microbial abundance and agroecosystem multifunctionality

Biochar and organic fertilizer are widely supported to maintain crop production and sustainable development of agroecosystems. However, it is unclear how biochar and organic fertilizer alone or in combination regulate soil functional microbiomes and their relationships to ecosystem multifunctionality (EMF). Herein, a long-term (started in 2013) field experiment, containing five fertilization treatments, was employed to explore the effects of biochar and organic fertilizer applications on the EMF (based on 18 functional indicators of crop productivity, soil nutrient supply, element cycling, and microbial biomass) and the functional microbiomes of bulk soil and rhizosphere soil [normalizing the abundances of 64 genes related to carbon (C), nitrogen (N), phosphorus (P), and sulphur (S) cycles]. Compared with single-chemical fertilization, biochar and organic fertilizer inputs significantly enhanced most ecosystem-single functions and, in particular, the EMF significantly increased by 18.7–30.1%; biochar and organic fertilizer applications significantly increased the abundances of soil microbial functional taxa related to C-N-P-S cycles to varying degree. The combined application of biochar and organic fertilizer showed a better improvement in these indicators compared to using them individually. Most functional microbial populations in the soil, especially the taxa involved in C degradation, nitrification, nitrate-reduction, organic P mineralization, and S cycling showed significantly positive associations with the EMF at different threshold levels, which ultimately was regulated by soil pH and nutrient availability. These results highlight the strong links between soil microbiomes and agroecosystem functions, as well as providing scientific support for inclusion of biochar in agricultural production and services with organic amendments.Graphical