Search Results (798)

Forest type strongly influences soil microbial community composition and associated carbon cycling, yet its influence on microbial functional traits remains poorly understood. In this study, metagenomics sequencing was used to investigate soil microbial communities and carbon metabolism genes across three forest types: deciduous broadleaf (DBF), mixed coniferous–broadleaf (CBMF), and coniferous forest (CF) at two soil depths (0–20 cm and 20–40 cm) on Lushan Mountain in subtropical China. The results showed that CF exhibited higher bacterial diversity and a distinct microbial composition, with an increase in Actinomycetota and Bacteroidota and a decrease in Acidobacteriota and Pseudomonadota. The Calvin cycle was the dominant carbon fixation pathway in all forests, while the relative abundance of secondary pathways (i.e., the 3-hydroxypropionate bi-cycle and reductive citrate cycle) varied significantly with forest type. Key carbon fixation genes (sucD, pckA) were more abundant in CF and CBMF, with higher levels of rpiA/B and ackA in DBF. Functional profiling further indicated that CF soils, especially in the surface layer, were enriched in glycoside hydrolases (GHs) and carbohydrate esterases (CEs), while CBMF showed a greater potential for starch and lignin degradation. Multivariate statistical analyses identified soil available phosphorus (AP) and pH as primary factors shaping microbial community variation, with AP emerging as being the dominant regulator of carbon-related functional gene abundance. Overall, the prevalence of these distinct genetic potentials across forest types underscores how vegetation composition may shape microbial functional traits, thereby influencing the stability and dynamics of the soil carbon pool in forest ecosystem. Full article

To reveal the driving mechanisms of oxidative carbon components in urban forest soils in highly urbanized areas, this study collected 126 soil samples from the 0–30 cm layer of typical urban forests in Shenzhen, China. Soil organic carbon (SOC) was classified into four fractions based on oxidation stability: highly oxidizable organic carbon (VAC), moderately oxidizable organic carbon (AC), poorly oxidizable organic carbon (PAC), and inert oxidizable organic carbon (IAC). Integrating multi-source data on climate, topography, vegetation, soil, and urbanization, we adopted a synergistic multi-model approach to screen key drivers, identify nonlinear thresholds, and quantify pathway contributions, thereby systematically exploring the dominant characteristics and driving mechanisms of soil carbon components under urbanization. The results showed that (1) urban forest soils in Shenzhen were dominated by reactive carbon, with VAC accounting for the highest proportion of SOC, and the proportion of reactive organic carbon was significantly higher than that of recalcitrant organic carbon; (2) SOC and total nitrogen (TN) were the core driving factors of carbon fractions, and the number of regulatory factors increased with the enhancement of carbon fraction oxidation stability; (3) soil factors directly affected carbon fractions, while urbanization indirectly acted on inert carbon by altering vegetation characteristics. Based on the research results, urban soil and forest managers can implement zonal management for carbon fractions with different oxidation stabilities, which is expected to effectively enhance the carbon sink capacity and stability of urban forest soil carbon pools, providing practical support for ecological sustainable development. Full article

Ecological stoichiometry provides a useful lens for linking nutrient status to ecosystem functioning, but cross-compartment (green leaves, surface litter, and topsoil) evidence for subtropical secondary forests is still limited. In particular, it remains unclear how forest type regulates coupled carbon (C), nitrogen (N), and phosphorus (P) patterns in leaves, litter, and soils on P-retentive Acrisols and how these patterns can be used to infer nutrient limitations. We measured C, N, and P concentrations and stoichiometric ratios in leaves, surface litter, and topsoil (0–10 cm) from 38 plots representing four dominant forest types (shrub, coniferous, mixed coniferous–broadleaf, and broadleaf) in subtropical public welfare forests of eastern China. We compared elemental concentrations and ratios among forest types and compartments and examined cross-compartment associations. Forest-type differences in stoichiometric patterns were most pronounced for leaf and soil concentrations/ratios, whereas litter metrics were comparatively conservative. Coniferous stands had the highest leaf C concentration and the highest litter C:N and C:P ratios, together with relatively low soil N and P concentrations. Broadleaf stands had the highest soil C and N concentrations and the highest litter and soil N:P, suggesting a tendency toward P limitation under comparatively N-rich conditions. Shrub and mixed forests were intermediate, with shrubs exhibiting the lowest litter N:P. Leaf N:P averaged 7.5 in coniferous stands and 12.5–14.9 in mixed and broadleaf stands. Coherent correlations of C:P from leaves to litter and soils and a negative relationship between leaf N:P and soil C:N suggested coordinated stoichiometric linkages along the leaf–litter–soil continuum. Overall, the results show that forest type organizes plot-scale C:N:P coupling on Acrisols and that leaf–litter–soil stoichiometry can be used as a practical framework for identifying whether N- versus P-related constraints are more likely to dominate different subtropical forest types and for informing nutrient-aware restoration and management. Full article

Acacia melanoxylon R.Br. demonstrates strong biological nitrogen–fixation capacity and favourable economic returns, making it a promising candidate for the development of subtropical forestry in South Asia. It is a fast–growing leguminous tree species widely promoted for cultivation in China, and it is also one of the ideal tree species for improving soil fertility in forest lands. What are the synergistic mechanisms between A. melanoxylon-Eucalyptus stands and pure Eucalyptus spp.? Current theories regarding A. melanoxylon–Eucalyptus systems remain relatively fragmented due to the lack of effective silvicultural measures, resistance studies, and comprehensive ecological–economic benefit evaluations. The absence of an integrated analytical framework for holistic research on A. melanoxylon–Eucalyptus systems makes it difficult to summarise and comprehensively analyse their growth and development, thereby limiting the optimisation and widespread application of their models. This study employed CiteSpace bibliometric analysis and qualitative methods to explore ideal tree species combination patterns, elucidate their intrinsic eco–economic synergistic mechanisms, and reasonably reveal their collaborative potential. This study systematically reviewed silvicultural management, stress physiology, ecological security, and economic policy using the Chinese and English literature published from 2010 to 2025. The narrative synthesis results indicated that strip intercropping (7:3) is widely documented as an effective model for creating vertical niche complementarity, whereby canopy light and thermal utilisation by A. melanoxylon species improve subsoil nutrient cycling by enhancing stand structure. A conceptual full–cycle economic assessment framework was proposed to measure carbon sequestration and timber premiums. Correspondingly, this conversion of implicit ecological services into explicit market values acted as a critical tool for decision–making in assessing benefit. A three–dimensional “cultivation strategy–physiological ecology–value assessment” assessment framework was established. This framework demonstrated how to move from wanting to maximise the output of an individual component to maximising the value of the whole system. It theorised and provided guidance on resolving the complementary conflict between “ecology–economy” in the management of sustainable multifunctional plantations. Full article

Quinoa, in addition to its nutritional benefits, is adaptable to, and tolerant of, high-altitude and Mediterranean environmental conditions. However, its largely cross-compatible free-living ancestor, pitseed goosefoot, possesses expansive adaptive variation as its ecotypes are found on arid or well-drained soils throughout temperate and subtropical North America. In this context, the objective of this study was to characterize F7:10 lines from quinoa × pitseed goosefoot hybrids to identify promising lines with desirable agronomic traits and adaptation to hyper-arid production environments. The agro-morphological characterization of 14 interspecific experimental lines plus wild parents (5), checks (3, including one derived from a much earlier wide cross), and an F2 population was performed for 25 quantitative and 26 qualitative descriptors, along with calculation of the selection index. Among the morphological variables, the average number of primary branches per plant (NPB) was six (CV = 78%), the average plant height (PH) was 143.5 cm (CV = 40%), and the average panicle diameter (PDI) was 17.9 cm (CV = 62%). With regard to the yield component variables, the average harvest index (HI) was 39% (CV = 36%), the average weight of 1000 grains (W1000G) was 2.59 g (CV = 42%), and the average yield per hectare (HYP) was 4.68 t ha⁻¹ (CV = 65%). Regarding the correlations between variables, it was observed that all phenological phases showed positive correlations with plant height (PH) and negative correlations with yield components, specifically with DG, DT, HI, and W1000G. The highest-yielding lines were GR10 (8.16 t ha⁻¹), GR07 (7.53 t ha⁻¹), GR11 (7.27 t ha⁻¹), and GR01 (7.02 t ha⁻¹). Multivariate and cluster analyses identified four groups of lines, with groups II and IV standing out for their desirable agronomic traits. However, based on the selection index, lines RL08, RL07, ER06, GR03, and GR11 were identified as the most promising. In terms of quality, 18 out of the 23 lines were classified as sweet (<0.11% saponin) and 5 as bitter (>0.11 saponin). In conclusion, the selection index identified pitseed goosefoot cross-derived quinoa lines having superior yield potential, short plant height, large grain size, early maturity, and low saponin content. Full article

Sclerotium rolfsii Sacc. is a soil-borne fungus that causes southern blight on many crops in the tropical and subtropical regions. In 2018, southern blight was reported as the most prevalent bean root rot in Uganda. Earlier studies ascertained the morphological and pathogenic diversity of S. rolfsii, but a limited understanding of its genetic diversity exists. Knowledge of S. rolfsii genetic diversity is a critical resource for pathogen surveillance and developing common bean varieties with durable resistance. A total of 188 S. rolfsii strains from infected common bean plants were collected from seven agro-ecological zones of Uganda in 2013, 2020 and 2021, and characterized morphologically and pathogenically. The genetic diversity of the strains was assessed using single-nucleotide polymorphisms (SNPs) obtained from whole-genome sequencing. The growth rate of the strains ranged between 1.1 and 3.6 cm per day, while the number of sclerotia produced ranged from 0 to 543 per strain. The strains had fluffy, fibrous, and compact colony texture. The strains were pathogenic on common bean and caused disease severity indices ranging from 10.1% to 93.3%. Average polymorphic information content across all chromosomes was 0.27. Population structure analysis identified five genetically distinct clusters. The results of analysis of molecular variance revealed that 54% of the variation was between clusters while 46% of variation was within clusters. Pairwise comparison of Wright’s fixation indices between genetic clusters ranged from 0.31 to 0.78. The findings of this study revealed moderate genetic diversity among S. rolfsii strains, which should be taken into consideration when selecting strains for germplasm screening. Full article

The long-term monoculture of Eucalyptus plantations in southern China has raised ecological concerns, prompting a shift towards mixed-species plantations as a sustainable alternative. This study investigates the mechanisms by which companion tree species enhance soil functionality in subtropical red soil regions. A field experiment compared a pure Eucalyptus (CK) plantation with three mixed-species plantations: Eucalyptus × Mytilaria laosensis (A × M), Eucalyptus × Magnolia hypolampra (A × H), and Eucalyptus × Michelia gioii (A × X). Comprehensive soil analyses were conducted at three soil depths (0–20 cm, 20–40 cm, and 40–60 cm) to assess chemical properties, enzyme activities, and humus components, and soil organic carbon (SOC) molecular structure was characterized by Fourier-Transform Infrared Spectroscopy (FTIR), with the relationships quantified using structural equation modeling (SEM) to test predefined causal hypotheses. The results showed that A × H significantly boosted topsoil fertility (e.g., OM: 46.61 g/kg), while A × M enhanced the recalcitrant organic carbon (ROC: 35.29 g/kg), indicating superior carbon sequestration potential. The FTIR analysis revealed species-specific alterations in SOC chemistry, such as increased aromatic compounds in A × H/A × X. The SEM analysis demonstrated that the latent variable “Humus” (reflected by LOC and ROC) directly and positively influenced the latent variable “Soil Fertility” (reflected by pH, OM, and AP; path coefficient: 0.62). In contrast, the latent variable “Organic Components” (reflected by specific FTIR functional groups) exhibited a significant direct negative effect on “Soil Fertility” (−0.41). The significant pathway from “Organic Components” to “Enzymatic Activity” (0.55*) underscored the role of microbial mediation. The study concludes that mixed plantations, particularly with Mytilaria laosensis (A × M), improve soil health through an “organic input–microbial enzyme response–humus formation” pathway, offering a scientific basis for sustainable forestry practices that balance productivity and ecological resilience. Full article

Background: Chinese Yellow Earth is a key subtropical agricultural resource in southwestern China; however, its productivity is limited by acidity and poor nutrient retention. This study examined how reduced nitrogen plus organic amendments affect its soil microbial structure and maize yield. Methods: A field experiment with four treatments evaluated reduced nitrogen fertilization amended with rice husk plus rapeseed cake (RS) or RS with biochar (BC). Soil properties (pH, nitrogen, organic matter) and maize yield were analyzed. Metagenomic analysis (NR database) characterized microbial communities, and correlation analysis with Mantel tests identified key relationships. Results: Combined organic amendments under reduced N significantly increased soil pH, nitrogen components, and organic matter, increasing maize yield by 4.41–8.97%. Metagenomics revealed enriched beneficial genera including Sphingomonas and Bradyrhizobium. Yield positively correlated with nitrate nitrogen and a beneficial microbial cluster containing Lysobacter and Reyranella, whereas Steroidobacter negatively correlated with key fertility indicators. Mantel tests revealed nitrate nitrogen as the primary correlate of functional gene community succession. Conclusions: This study reveals that reduced nitrogen with organic amendments promotes soil improvement and microbial modulation, demonstrating potential as a sustainable practice to maintain crop productivity in Chinese Yellow Earth. The observed trend toward yield improvement underscores its promise and warrants further validation through additional trials. Overall, the findings highlight the beneficial effects of these amendments on soil health and their role in supporting sustainable subtropical agriculture under reduced nitrogen input. Full article

Nitrogen (N) is essential for maize (Zea mays L.) productivity, yet its acquisition is limited by the low N uptake efficiency of current varieties. Root cortical aerenchyma (RCA) formation provides a carbon-saving strategy that enhances soil exploration and N acquisition by reducing the metabolic cost of root tissue. However, the genetic basis of RCA formation remains poorly characterized. This study employed an association panel of 295 maize inbred lines to dissect the genetic architecture of RCA formation under low nitrogen (LN) stress. Phenotypic analysis demonstrated that LN stress significantly induced RCA area (RCAA) and proportion (RCAP), with responses ranging from −0.31 to 1.16 mm² for RCAA and −11.34% to 40.18% for RCAP. The non-stiff stalk (NSS) subpopulation exhibited 29.19% higher RCAA under LN than the stiff stalk subgroup. Genome-wide association analysis detected a total of 560 significant SNPs and 810 candidate genes associated with RCA-related traits. Transcriptomic profiling further identified 537 differentially expressed genes between inbred lines with contrasting RCA phenotypes. Integrated GWAS and transcriptomic analysis pinpointed 12 co-localized candidates, subsequently refined to four core genes (GRMZM2G033570, GRMZM2G052422, GRMZM2G080603, and GRMZM2G472266), which were implicated in ethylene signaling and stress-responsive root development. Favorable haplotypes of three genes were predominantly distributed in the NSS (25.64–56.00%) and tropical/subtropical (20.51–46.67%) subpopulations. These findings elucidate the genetic basis of LN-responsive RCA formation and provide fundamental resources for marker-assisted breeding of N-efficient maize. Full article

Healthy soil serves as the fundamental basis for sustainable Panax notoginseng (Burkill) F.H. Chen ex C.Y. Wu & K.M. Feng cultivation in understory systems. Current management practices have raised concerns about potential soil degradation and ecological imbalance. To comprehensively assess the soil health status, this study investigated typical understory P. notoginseng plantations in the subtropical mountain monsoon region of western Yunnan. By analyzing 29 soil physical, chemical, and biological indicators, we constructed a Minimum Data Set (MDS) using Principal Component Analysis to evaluate soil health and identify major constraints. The results showed that the MDS for soil health assessment consisted of 11 key indicators: acid phosphatase, fungal ACE index, organic matter, total nitrogen, sucrase, fungal Simpson index, fine sand, non-capillary porosity, silt content, bulk density, and microbial biomass nitrogen. Using both linear and non-linear scoring functions, the Soil Health Index (SHI) calculated based on the MDS showed a significant positive correlation with the SHI derived from the Total Data Set (TDS) (linear scoring: R² = 0.43, p < 0.001; non-linear scoring: R² = 0.305, p < 0.001). This indicates that the MDS captures a substantial and significant portion of the variation explained by the TDS and can serve as a practical and simplified alternative for soil health evaluation in this cultivation system. Based on the MDS, the SHI values obtained using linear and non-linear scoring functions ranged from 0.53 to 0.72 and 0.48–0.59, with mean values of 0.62 and 0.51, respectively, indicating moderate soil health status in the study area. Significant differences in SHI were observed across planting durations and seasons (p < 0.05), with two-year-old plantations showing notably better soil health indices than three-year-old plantations, particularly during the rainy season. The main constraints identified in understory P. notoginseng plantations included microbial community degradation, nutrient imbalance, and physical structural deterioration. Implementing scientific soil management strategies such as optimized rotation cycles, organic amendment applications, and microbial community regulation can effectively mitigate these soil constraints, enhance soil health, and promote the sustainable development of understory P. notoginseng cultivation. Full article

Soil organic matter (SOM) governs critical soil functions, including carbon storage, nutrient cycling, and microbial activity; yet the specific fractions responsible for its spectral predictability remain poorly understood. This study addresses a fundamental research gap by comparing visible–near-infrared (vis–NIR), mid-infrared (MIR), and fused spectroscopy for predicting SOM and its components: humic acid (HA), fulvic acid (FA), and Humin. Using 93 soil samples from subtropical croplands in southeastern China, we employed partial least squares regression with full spectra and LASSO-selected wavelengths to build predictive models. Results demonstrated that both vis–NIR and MIR individually provided moderately strong predictive performance for SOM and Humin (R² = 0.79–0.90, CCC = 0.85–0.93), while FA remained unpredictable (R² < 0.24) due to weak, overlapping spectral features. The strong predictability of SOM was primarily attributed to the Humin fraction, which comprises approximately 50 percent of total SOM and exhibits abundant spectrally active functional groups. Contrary to expectations, spectral fusion did not improve predictions because both spectral regions already contained complementary information, and fusion introduced redundancy and scale imbalance rather than increasing effective dimensionality. This study establishes that accurate SOM estimation depends fundamentally on the predictability and abundance of the Humin fraction, providing new mechanistic insights for spectroscopic soil carbon monitoring and highlighting the need for component-specific modeling approaches in soil organic matter research. Full article

Chinese fir (Cunninghamia lanceolata) is a cornerstone timber species in southern China. However, yet its plantation productivity frequently declines under successive rotations, threatening long-term sustainability. While belowground processes are suspected drivers, the mechanisms—particularly plant–soil–microbe interactions—remain poorly resolved. To address this, we examined a chronosequence of C. lanceolata plantations (5, 15, 20, and 30 years) in Jingdezhen, Jiangxi Province, integrating soil physicochemical assays, high-throughput sequencing, and extracellular enzyme activity profiling. We found that near-mature stands (20 years) exhibited a 60.7% decline in mean annual volume increment relative to mid-aged stands (15 years), despite continued increases in individual tree volume—suggesting a strategic shift from resource-acquisitive to nutrient-conservative growth. Peak values of soil organic carbon (32.87 g·kg⁻¹), total nitrogen (2.51 g·kg⁻¹), microbial biomass carbon (487.33 mg·kg⁻¹), and phosphorus (25.65 mg·kg⁻¹) coincided with this stage, reflecting accelerated nutrient turnover and intensified plant–microbe competition. Microbial communities shifted markedly over time: Basidiomycota and Acidobacteria became dominant in mature stands, replacing earlier Ascomycota and Proteobacteria. Random Forest and Partial Least Squares Path Modeling (PLS-SEM) identified total nitrogen, ammonium nitrogen, and total phosphorus as key predictors of productivity. PLS-SEM further revealed that stand age directly enhanced productivity (β = 0.869) via improved soil properties, but also indirectly suppressed it by stimulating microbial biomass (β = 0.845)—a “dual-effect” that intensified nutrient competition. Fungal and bacterial functional profiles were complementary: under phosphorus limitation, fungi upregulated acid phosphatase to enhance P acquisition, while bacteria predominately mediated nitrogen mineralization. Our results demonstrate a coordinated “soil–microbe–enzyme” feedback mechanism regulating productivity dynamics in C. lanceolata plantations. These insights advance a mechanistic understanding of rotation-associated decline and underscore the potential for targeted nutrient and microbial management to sustain long-term plantation yields. Full article

Understory vegetation (shrubs and herbs) mediates belowground biogeochemical processes in forests through litter inputs, root exudation, and microenvironmental regulation; however, the magnitude of these regulatory effects remains poorly quantified. Here, we conducted a 10-year small-scale understory vegetation manipulation experiment in a coniferous–broadleaf mixed forest in central China, aiming to systematically assess the impacts of understory vegetation on soil carbon (C), nitrogen (N), and phosphorus (P) dynamics. Two experimental treatments were established: (1) the “None” treatment (removal of both understory vegetation and litter) and (2) the “Understory” treatment (litter removal while retaining understory vegetation). Results indicated that compared with the “None” treatment, the “Understory” treatment did not significantly alter the concentrations or stocks of soil organic C (SOC) and total N (p > 0.05), suggesting a weak responsiveness of SOC and total N to understory vegetation presence. In contrast, understory vegetation exerted a significant positive effect on soil P fractions: total P concentration and stock increased by 3.97% and 2.68%, organic P by 6.65% and 5.32%, and available P by 46.38% and 43.96%, respectively (p < 0.05). These results demonstrate that understory vegetation exerts a more pronounced regulatory effect on soil P dynamics than on C and N dynamics. In conclusion, understory vegetation plays a pivotal role in promoting soil P sequestration and improving P availability in coniferous–broadleaf mixed forest ecosystems. We recommend retaining understory vegetation in forest management practices to sustain soil P availability and mitigate widespread P limitation in such ecosystems. Full article

Savanna ecosystems of the Sahel are heavily affected by climate change, leading to drier subtropical regions. These ecosystems play a fundamental role in food security of the region, so that an improved understanding of how these ecosystems are affected by these weather events is thereby critical. Several studies have assessed the herbaceous production level, dynamics during the rainy season, and biotic and abiotic factors that could impact this production. Some authors argue that rain is the main factor positively influencing the biomass production in semi-arid areas where the rainfall ranges between 200 and 750 mm. This study aims to assess the contribution of some meteorological variables to biomass production in a Sahelian semiarid savannah. From 2008 to 2018, rainfall (mm), soil moisture (%), soil temperature (°C) at 5 cm depth, number of times there was no rain (NTNR), number of rainy days, and the herbaceous biomass were monitored. The contributions of meteorological variables to biomass production were calculated using the XGBoost regression model. The most influential meteorological parameters on herbaceous biomass production are soil temperature, amount, and distribution of rainfall. Full article

Subtropical deciduous broad-leaved forests in eastern China form a key ecotone between temperate and subtropical biomes, yet their vegetation–environment relationships remain insufficiently understood. This study examined community structure, species diversity, and their associations with topographic and soil variables in a 25 ha forest dynamics plot in the Lushan Mountains. All woody plants with a diameter at breast height (DBH) ≥ 1 cm were surveyed, and detailed topographic attributes and soil physicochemical properties were measured. Community structure showed strong linkages with species diversity: tree-layer structural characteristics were generally negatively correlated with diversity, whereas in the shrub layer, density was negatively but height and DBH were positively correlated with diversity. Species diversity in the two layers was positively associated, while tree-layer structure was negatively related to shrub-layer diversity. Among topographic factors, altitude and the topographic solar radiation aspect index (TRASP) exerted the strongest influences on soil properties, with altitude negatively correlated with soil pH and available nutrients but positively correlated with C:N, C:P, and total carbon, and TRASP showing negative correlations with most nutrients except total phosphorus. Redundancy analysis revealed that topographic heterogeneity and soil conditions jointly shaped community structure and species diversity, with soil C:N ratio, altitude, pH, total phosphorus, and total carbon emerging as key drivers. These findings demonstrate that areas with high plant diversity do not always correspond to high soil nutrient content and underscore the importance of integrating both topographic and edaphic factors into biodiversity conservation and forest management in subtropical deciduous broad-leaved forests. Full article