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As sustainable forest management gains increasing attention, comprehending the impact of stand density on soil properties and microbial communities is crucial for optimizing forest ecosystem functions. This study employed high-throughput sequencing in conjunction with soil physicochemical analysis to assess the effects of stand density on soil physicochemical properties and microbial community characteristics in Chinese fir plantations, aiming to elucidate the influence of density regulation on ecosystem services. Our results suggested that changes in soil physicochemical properties and microenvironmental conditions were key drivers of soil microbial diversity. Total carbon (TC), soluble nitrogen (SN), and light fraction organic matter decreased with increasing stand density, while total potassium (TK) and available phosphorus (AP) concentrations increased. The plot with a density of 900 trees ha−1 exhibited the highest bacterial diversity, in contrast to the plot with 1500 trees ha−1, which showed the lowest. The dominant microbial taxa were similar across different stand retention densities, with Acidobacteria, Proteobacteria, and Chloroflexi being the predominant bacterial phyla and Ascomycota and Basidiomycota being the main fungal groups. Significant positive correlations were observed between soil microbial community structures and environmental factors, particularly with respect to soil phosphorus and nitrogen content. The present study demonstrated that reduced stand densities modulated soil nutrient content and enhanced bacterial diversity, thereby contributing to a more complex and stable soil ecosystem structure. These insights provide a scientific foundation for optimizing the management of Chinese fir plantations, thereby supporting the sustainable development of forest ecosystems. [ABSTRACT FROM AUTHOR]

The interaction between forests and precipitation plays a crucial role in the material cycling of forest ecosystems. Atmospheric deposition and rainfall leaching promote the transfer of heavy metals to the forest floor, while canopy exchange may potentially slow this process. Therefore, studying heavy metal fluxes and their influencing factors, along with canopy rainfall partitioning, is essential for understanding forest material cycling. We conducted a year-long experiment to examine the dynamics of chromium (Cr), cadmium (Cd), and lead (Pb) concentrations and fluxes in four types of forests (Cunninghamia lanceolata plantations, Castanopsis carlesii plantations, Cas. carlesii natural forests, and Cas. carlesii secondary forests) located in the subtropical regions of southeast China. Results showed that (1) the annual mean concentrations of Cr, Cd, and Pb were 167.6, 13.8, and 6180.5 μg L−1 in the throughfall and 204.7, 28.4, and 2251.1 μg L−1 in the stemflow, respectively, and the annual fluxes of Cr, Cd, and Pb through throughfall were 29.3, 2.4, and 847.7 g ha−1, respectively, and were 1.7, 0.2, and 12.7 g ha−1 through stemflow, respectively; (2) the concentrations of these heavy metals associated with throughfall did not vary between forest types, but their fluxes were highest in Cas. carlesii natural forests; (3) Cr concentration and flux were higher during the rainy than dry seasons, while Cd and Pb concentrations and fluxes showed an opposite trend. Overall, our results indicate that the fluxes of heavy metals along with rainfall partitioning were highest in natural forests and are primarily controlled by meteorological factors, indicating that the conversion of natural forests to other forest types will substantially change the fluxes of heavy metals along with hydrological processes. These results will contribute to a better understanding of the natural fluxes of heavy metals in forest ecosystems and are valuable for sustainable forest management, particularly in the context of forest type transformation. [ABSTRACT FROM AUTHOR]

This study used triaxial tests to examine the impact of the root diameter of Cunninghamia lanceolata (Chinese fir) on the mechanical behavior of sand, including stress–strain development, strength, volumetric strain, and failure envelope. It also revealed the reinforcement mechanisms of roots with different diameters based on root–soil interactions. The results showed the following: (1) The addition of roots significantly enhanced sand strength and reduced volumetric deformation. The average peak strength increased by 31.8%, while the average peak volumetric strain decreased by 34.3%. (2) Roots provided additional cohesion and increased the friction angle of the sand, causing the failure envelope to shift upward and deflect. (3) Smaller-diameter roots improved the mechanical properties of sand more significantly, leading to higher peak strength, shear strength parameters, and smaller volumetric deformation. As the root diameter increased from 1 mm to 5 mm, the peak strength ratio decreased from 1.78 to 1.13, and the peak volumetric strain increased from 0.48 to 0.79. (4) Smaller-diameter roots, which form denser networks, allowing more roots to resist loads, and have a higher elastic modulus providing greater tensile stress, also possess higher tensile strength and critical sliding tensile stress, making them less likely to fail, thereby making the mechanical reinforcement of sand more significant. [ABSTRACT FROM AUTHOR]

Mixed plantation of Chinese fir (Cunninghamia lanceolata) is an effective artificial forest management for tree productivity. However, the mixing strategies, site conditions, and subsurface properties that affect tree productivity are not yet fully understood. In this study, we conducted a meta-analysis of 96 publications to consolidate insights on the effects of mixing strategies (e.g., planting density, mixing proportion, mixed species, and tree age), site conditions (e.g., mean annual precipitation (MAP), mean annual temperature (MAT), elevation, and total nitrogen (TN) or total phosphorus (TP) of sample sites), and subsurface properties (e.g., soil characteristics, microbial communities, and extracellular enzyme activity) on tree height, diameter at breast height, and individual volume of Chinese fir. We used the Web of Science and China National Knowledge Infrastructure for searching peer-reviewed papers, and the searching words were: ("Cunninghamia lanceolata" OR "Chinese fir") AND "mix*". Following the data screening process, the natural logarithm of the response ratio (lnRR) was computed for subsequent analysis. The results showed that introduced companion species generally increased the individual volume of Chinese fir by an average of 20%. Densities ranging from 1200 to 2000 trees per hectare and moderate mixing proportions (1:1 to 3:1) optimized individual tree growth and thereby boosted productivity. Broadleaf species may be beneficial companions, and trees aged 10 to 20 years grew fastest. At sites with low MAT and high MAP, mixed plantations enhanced the tree productivity of Chinese fir. The optimal elevation range for mixed plantations may be 200 to 600 m. Further, mixed plantations significantly changed soil properties by improving soil structure, increasing soil pH and soil water content, and soil total and available N and P, which were crucial for boosting the productivity of Chinese fir. Soil microbial biomass and enzyme activities were also significantly increased by mixed plantations. Overall, these findings highlight the importance of mixing strategies and site conditions in increasing tree productivity of Chinese fir by improving soil physicochemical characteristics, increasing resource availability, and reducing interspecific and intraspecific competition through niche separation. [ABSTRACT FROM AUTHOR]

The development of branches on the lower part of the trunk plays a decisive role in the early growth of trees and influences the wood quality of their most valuable sections. This study investigated the effects of planting density on the horizontal and vertical spatial distribution, branch morphology, and branch quantity characteristics of two elite clones of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.), Yang 061 and Yang 020. The results revealed the following distinct responses between the two clones: Yang 061 exhibited significant reductions in branch base diameter and length under a higher planting density, alongside an increased frequency of small branches (<15 mm), but there was no significant effect on branch angles. In contrast, Yang 020 was primarily influenced by genetic factors, with planting density exerting minimal impact. This clone optimized resource allocation by promoting the mortality of lower branches through angle adjustments, resulting in negligible changes to branch development across different planting densities. Pronounced differences in vertical and horizontal branch distributions were observed in areas with significant light disparities, such as the middle crown and northeast direction, for both clones, with increased planting density exacerbating these differences. In conclusion, increasing the planting density of Yang 061 from 2500 to 3333 trees·ha−1 can effectively reduce its branch size; whereas, increasing the planting density of Yang 020 from 3000 to 5100 trees·ha−1 can slightly decrease its branch size without affecting its early rapid growth, thereby achieving a synergistic improvement in both timber yield and quality. These findings highlight the importance of interactions between genetic traits and planting density in shaping branch development and spatial distribution patterns, providing insights to optimize planting density for improving the productivity and wood quality of Cunninghamia lanceolata plantations. [ABSTRACT FROM AUTHOR]

Exploring the components of soil organic carbon (SOC) and aggregate stability across different elevations is crucial to assessing the stability of SOC in subtropical forest ecosystems under climate change. In this study, we investigated the spatial variation of active carbon (C) compositions, aggregate distribution, and stability in Chinese fir (Cunninghamia lanceolata) plantations across an elevation gradient from 750 to 1150 m a.s.l. on the northern foothills of the Dabie Mountains, China. The results showed that macroaggregates accounted for more than 80% of all fractions at different elevations. In the 0–10 cm soil layer, the macroaggregates, mean weight diameter (MWD), geometric mean diameter (GMD), and SOC exhibited a U-shaped distribution trend with increasing elevation. Conversely, in the 10–50 cm soil layer, these indicators showed a consistent increasing trend. Similarly, the contents of easily oxidizable carbon (EOC) and particulate organic carbon (POC) gradually increased with increasing elevation. Microbial biomass carbon (MBC) and silt + clay C exhibited a unimodal distribution pattern along the elevational gradient, peaking at 850 m a.s.l., which is mainly related to soil pH and C/N ratio. Across all elevations, The silt + clay C was significantly higher than that of macro- and micro-aggregate C. Macro- and micro-aggregate C, and dissolved organic carbon (DOC) were significantly positively correlated with MWD. The results demonstrated that elevation and soil layer have significant effects on SOC and aggregate stability. The physical protection of silt + clay fractions and the active carbon pools may be the main mechanisms for organic carbon preservation in the Dabie Mountains. These results contribute to further deepening the impact of elevation on climate change and the C cycling of forest ecosystems. [ABSTRACT FROM AUTHOR]

Improving the physical, mechanical, and creep properties of wood fiber-reinforced polymer composites is crucial for broadening their application prospect. In this research, seven types of high-density polyethylene (HDPE) composites reinforced with different mass ratios of Masson pine (Pinus massoniana Lamb.) and Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.] were prepared by a two-step extrusion molding method. The mass ratios of the two fibers were 60:0, 50:10, 40:20, 30:30, 20:40, 10:50, and 0:60, respectively. The surface color, density, dimension stability, bending, tensile, impact properties, dynamic mechanical properties, and 24 h creep properties at a 10% stress level of the seven composites were investigated. Additionally, the Rule of Mixtures (ROM), the Inverse Rule of Mixtures (IROM), the Hirsch models, and the improved model were employed to simulate the mechanical properties, while the Findley index model, the two-parameter index model, and the modified ExpAssoc model were employed to simulate the creep performance of the composites. This study revealed that as the proportion of Chinese fir wood flour increased, the mechanical properties of the composites gradually improved, the storage modulus showed an increasing trend, while the loss modulus decreased, and the overall creep strain of the composites increased. Among the various models, the modified model simulated the mechanical properties of the composites the best, while the modified ExpAssoc model simulated the creep behavior most effectively. [ABSTRACT FROM AUTHOR]

Knowledge of how different drivers affect tree responses to drought is unprecedentedly imperative in the context of increasing frequency and severity of climatic droughts. Here, to fully understand the drought response complexity of trees, we assessed drought resilience (resistance and recovery) for Chinese fir (Cunninghamia lanceolata) in Southeast China based on tree ring from 324 trees, and used mixed effects model and machine learning (ML) to examine the roles of tree size, predrought growth performances, multiple drought dimensions, and microtopography in affecting tree drought responses. ML were interpreted using a novel of SHapley Additive exPlanations (SHAP) method. Tree responses to drought were primarily driven by tree characteristics (tree size and predrought growth), rather than drought dimensions (intensity, duration and occurrence Timing) and microtopography (elevation and slope aspect). Resistance and resilience increased with tree size and pre-drought growth variability but decreased with drought intensity- quantified by negative climate water balance. Recovery increased with predrought growth rates but decreased with drought duration. The drought intensity threshold for trees fully recovery of tree growth was about -80 mm. Higher elevations and shady slopes favored resistance (resilience) and recovery respectively, which combined with a greater impact of drought in the dry season suggested that the trees suffered more from droughts that only occurred in the dry season, especially at low- and medium-elevation sunny slopes. This study provided a comprehensive insight into tree growth response to drought, and contributed to the understanding of the mechanisms underlying the complexity of drought response. Increasing size diversity in Chinese fir plantations at sunny lower-elevation slopes is a promising measure to cope with the negative effects of drought. [ABSTRACT FROM AUTHOR]

Aim: As an environment friendly regulating factor, acetic acid (AA) plays an important role in linking basic physiological progresses and hormone signaling. Methods: In this study, seedlings of Cunninghamia lanceolate collected from two different rainfall regions were used to explore the effects of exogenous AA. Results: The results indicated that exogenous AA (200 mM) could eliminate drought-induced damages. The application of AA to soils could induce needle abscisic acid accumulation to decrease stomatal conductance and transpiration rate and further lead to the maintenance of needle water content and water use efficiency. Meanwhile, AA promotes the photosynthetic activity and photo-protection by increasing the contents of chlorophyll pigments and the activity of PSII reaction center. The alleviation of electrolyte leakage and malondialdehyde induced by drought, accompanied by the enhancement of the ROS scavenging system and osmotic regulation indicated that AA could protect cell membrane and eliminate oxidative toxicity. Additionally, this work further showed the provenance-specific responses to exogenous AA and demonstrated the feasibility of exogenous AA in larger pot experiments for woody plants. Conclusion: Overall, our study provides evidence that exogenous AA can strengthen the ability of C. lanceolate seedlings against drought as a positive regulator. Therefore, the irrigation of appropriate doses of AA into soils can be an effective practice against drought for Chinese fir forests. [ABSTRACT FROM AUTHOR]

Long‐term pure forest (PF) management and successive planting has result resulted in "low‐efficiency artificial forests" in large areas. However, controversy persists over the promoting effect of introduction of broadleaf tree species on production efficiency of PF. This study hypothesised that introduced broadleaf tree species can significantly promote both water‐nutrient use efficiency and gross primary productivity (GPP)of PF. Tree ring chronologies, water source, water use efficiency and GPP were analysed in coniferous Cunninghamia lanceolata and broadleaved Phoebe zhennan growing over the past three decades. The introduction of P. zhennan into C. lanceolata plantations resulted in inter‐specific competition for water, probably because of the similarity of the main water source of these two tree species. However, C. lanceolata absorbed more water with a higher nutrient level from the 40–60‐cm soil layer in mixed forests (MF). Although the co‐existing tree species limited the basal area increment and growth rates of C. lanceolata in MF plots, the acquisition of dissolved nutrients from the fertile topsoil layer were enhanced; this increased the water use efficiency and GPP of MF plots. To achieve better ecological benefits and GPP, MFs should be constructed in southern China. Summary Statement: 1)The effects of introduced broadleaf tree species on benefits of pure forest (PF) was evaluated.2)Both species probably have competition for water at low levels in the mixed forests (MF).3)Although the co‐existing tree limited the Basal area increment of MF, the water use efficiency and gross primary productivity increased.4)The introduction of MFs enhances the water and nutrient acquisition resources. [ABSTRACT FROM AUTHOR]

Forest soils play a key role in the global carbon (C) pool and in mitigating climate change. The mechanisms by which understory and litter management affect soil organic C (SOC) concentrations are unclear in subtropical forests. We collected soils along a 60 cm profile in a Chinese fir (Cunninghamia lanceolata) plantation treated by only aboveground litter removal and understory vegetation preservation (Only-ALR), both aboveground litter and understory vegetation removal (ALR+UVR), and both aboveground litter and understory vegetation preservation (control) for 7 consecutive years. Five SOC fractions, physico-chemical properties, the biomass of microbial communities and the activities of C-acquiring enzymes were measured, and their correlations were analyzed for each of four soil layers (0–10, 10–20, 20–40 and 40–60 cm). Compared with control, Only-ALR decreased labile C pool I (LP-C I), labile C pool II (LP-C II) and dissolved organic C (DOC) in topsoil (0–20 cm) but had no effect on soil C fractions in subsoil (20–60 cm). A higher fungi and bacteria biomass in LP-C II and microbial biomass C (MBC) stock was observed in Only-ALR compared to ALR+UVR treatment. Soil pH and Gram-positive bacteria generally had impact on the variation of soil C fractions in topsoil and subsoil, respectively. Understory vegetation preservation offsets the declines of SOC and recalcitrant C but not the decreases in labile C caused by aboveground litter removal. Understory vegetation helps sustain SOC stock mainly via decreased C input and elevated soil pH which would change microbial biomass and activities when litter is removed. Our findings highlight the potential influence of long-term understory manipulation practices on C pool within a soil profile in subtropical plantation forests. [ABSTRACT FROM AUTHOR]

Ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) that can be absorbed and utilized by plants are heterogeneously distributed in soil, which affects plant growth and bacterial communities in the roots. To investigate the effects of single and mixed nitrogen (N) on bacterial communities in the rhizospheres and root surfaces of Cunninghamia lanceolata (CR, CRS) and Schima superba (SR, SRS), we subjected three different ratios of NH4+-N to NO3−-N 2:0, 1:1 (control, CK), 0:2 to cultivate the seedlings. Compared with the CK, the ratio of 0:2 increased the number, diversity, and composition of bacteria in CR, whereas the ratios of 2:0 and 0:2 both decreased in CRS, SR, and SRS. The bacterial diversities were both R > RS in two tree species, but there was no discernible trend between the two tree species in the rhizosphere and root surface. Proteobacteria and Bacteroidota were the dominant bacterial phyla in CR and CRS, whereas Proteobacteria and Acidobacteriota dominated in SR and SRS. Patescibacteria and Planctomycetota promoted the aboveground growth of C. lanceolata but negatively drove root growth. Patescibacteria and Cyanobacteria in SR were related to its root growth, whereas the Actinobacteriota in SR and SRS, and the Patescibacteria and Cyanobacteria in SRS, promoted its aboveground growth. Overall, the mixed N addition was more conducive to bacterial community proliferation than single N on rhizospheres compared to root surfaces. The opposite reactions were observed from the aboveground and underground growth, which were driven by a few dominant bacterial phyla. [ABSTRACT FROM AUTHOR]

The tree-associated microbiome is vital for both individual trees and the forest ecosystem. The microbiome is dynamic; however, it is influenced by the developmental stages and environmental stresses experienced by host trees. Chinese fir (Cunninghamia lanceolata) is an economically important tree species in the subtropical regions of China. This study investigated the diversity of microbial communities, including bacteria and fungi, in the roots and bulk soil of young (2 years old) and old (46 years old) Chinese fir. It specifically examined the functional characteristics of these microbial communities. Through a non-metric multidimensional scaling (NMDS) analysis, we examined differences in microbial community structures among root and soil samples of Chinese fir. Evaluations using α-diversity metrics (Chao1, Shannon, Pielou, etc.) confirmed significant differences in diversity and structure between soil and root samples but high similarity between young and old tree samples. A network analysis identified key bacterial and fungal genera, such as Burkholderia and Russula, which play pivotal roles in the microbiome structure. We also demonstrated significant variations in microbial metabolic functions, such as dioxin and benzoic acid degradation metabolic pathways, which might relate to stress alleviation for tree fitness. Additionally, for the detection of endophytic microorganisms in Chinese fir seeds, only small amounts (less than 10%) of fungal endophytes and bare bacterial endophytes were identified. In summary, this study revealed that the stable structure of the rhizosphere microbiome was established in the early stage of tree life in Chinese fir, which mostly originated from surrounding soil rather than seed endophytes. The associated microbial metabolic activity naturally decreased with tree aging, implicating the tree microbial dynamics and the need for the addition of an actively functional synthetic community for tree fitness. [ABSTRACT FROM AUTHOR]

With global warming, understanding the effect of elevated temperature on the decomposition of Chinese fir needle litter has significant implications for nutrient cycling, yield, and management of economically important Chinese fir plantations. We conducted simulated warming decomposition experiments in incubators at 25 °C, 30 °C, and 35 °C on Chinese fir needle litter from middle-aged, mature, and overmature stands. Changes in litter mass and concentrations of some metallic elements and recalcitrant components were measured in litter sampled at different decomposition time-steps up to 264 days (d). Warming to 35 °C significantly increased the mass loss rate of needle litter from overmature stands throughout the experiment (except at 72 d). The effect of warming on litter mass loss rate for middle-aged and mature stands was lower and is attributed to higher litter quality in these stands. Compared to 25 °C, warming to 30 °C and 35 °C increased the needle litter decomposition rate across all developmental stages by 17.3% and 48.3%, respectively. Potassium (K), calcium (Ca), and magnesium (Mg) were mostly released during needle litter decomposition in all Chinese fir developmental stages. Lignin, condensed tannins, total phenols, and cellulose were enriched in needle litter, while the release of hemicellulose from near the start of the decomposition experiment was attributed to its lower molecular weight compared with other carbohydrates in litter. Compared with 25 °C, warming to 35 °C increased the release rates from litter of K, Ca, and Mg by 14.7%, 24.6%, and 21.5%, and the release rates of lignin, total phenols, cellulose, and hemicellulose by 7.5%, 8.8%, 10.4%, and 13.7%. Needle litter iron (Fe), aluminum (Al), and sodium (Na) in different development stages and manganese (Mn) in the overmature stands were mostly enriched during the experiment. Warming significantly promoted the enrichment of Fe, Al (except for mature stands), and Na, and reduced the enrichment of Mn. In summary, the sensitivity of needle litter to temperature in overmature stands is higher than that in middle-aged and mature stands, suggesting that forest managers can extend the rotation length of Chinese fir plantations to increase the yield of large-diameter timber, litter decomposition, and ecosystem nutrient return. [ABSTRACT FROM AUTHOR]

Mixed broad-leaved trees are particularly effective in addressing ecological issues such as soil degradation and biodiversity loss caused by the dense planting of Chinese fir. Understanding the changes in soil bacterial communities in fir–broadleaf mixed forests as a function of fir retention density may offer new insights for optimizing management practices and enhancing the ecological functions of the underground components of forest ecosystems. In this study, the diversity and composition of soil bacterial communities in mixed Cunninghamia lanceolata and Betula luminifera forests (CFBFs) with diverse retention densities of Chinese fir (1250, 1560, and 1690 trees/hm2) were analyzed. The results suggested that the soil characteristics and microbial communities' diversity and structure are significantly influenced by the retention densities of Chinese fir in CFBFs. At the aggregate scale, the CFBFs with a retention density of 1560 trees/hm2 presented the greatest soil bacterial community diversity (based on the Chao 1 (3562.75) and Shannon indices (6.58)), and the diversity and richness of soil bacteria initially increase and then decrease as the retention density decreases. In CFBFs, regardless of the retention density, bacterial communities in soil were mainly composed of Acidobacteria, Proteobacteria, and Planctomycetes. The relative abundance of soil Acidobacteria first elevated and afterwards decreased as the retention density decreased, with the highest levels (47.15%) observed in the stand with 1560 trees/hm2 of Chinese fir. The Principal Coordinates Analysis (PCoA) showed that the soil microbial community structure in CFBEs with a retention density of 1560 trees/hm2 is significantly different from CFBEs with a retention density of 1260, and 1690 trees/hm2. Moreover, with different retention densities of Chinese fir, soil organic C, total N concentrations, and soil pH also significantly affected the diversity and composition of CFBF soil bacterial communities. Our results show that the choice of retention densities significantly influences soil microbial diversity and composition in CFBFs. Optimal retention densities (1560 trees/hm2) of Chinese fir in CFBFs can maximize bacterial diversity and stability, providing management guidance for thinning for sustainable management of the soil microenvironment of CFBFs. [ABSTRACT FROM AUTHOR]

Litter and soil C-N-P stoichiometry are of great significance for the sustainable development of Chinese fir plantations (Cunninghamia lanceolata). This research aims to explore the influence of stand types (including C. lanceolata × Mytilaria laocsensis, C. lanceolata × Michelia macclurei, and the pure stand type of C. lanceolata) on the C-N-P stoichiometric characteristics of litter and soil aggregates (including >2, 2-0.25, and <0.25 mm fractions) in Chinese fir plantations. Compared to the mixed stand types, the pure stand type had a higher level of litter C content and C/N ratio. However, litter C, N, and P stocks, together with soil organic C (Corg) and total N (Ntot) contents, stocks, and C/N/P ratios, were highest in the mixed stand types. Irrespective of the stand types, a decline in the size of soil aggregates was associated with an increase in the contents and ratios of soil Corg, Ntot, and total P (Ptot), and a converse trend was noted for their stock. Overall, this research helped to understand the C, N, and P dynamics of soil and litter among Chinese fir plantations, providing valuable insights for future Chinese fir cultivation practices. [ABSTRACT FROM AUTHOR]

Background and aims: "Astringent seed" is a type of abortive seed frequently observed in Chinese fir (Cunninghamia lanceolata). It is widely recognized but poorly understood for its underlying causes. This study investigates the potential of astringent seeds to alleviate the toxic effects of active aluminum ions. Methods: This study involved treating seeds and seedlings with two distinct concentrations of astringent seeds water extracts under the aluminum ion stress. Then the germination of seeds and growth of seedlings were evaluated and compared. Results: Under aluminum stress, both seed germination and seedling growth were notably inhibited. Treatment with a low-concentration of the extract significantly alleviated this inhibition. Root elongation in the seedlings increased by 36.95% compared to the control group, and the aluminum ion accumulation at the root tips was reduced by 38.89% relative to the aluminum-stressed group. This treatment also normalized the levels of malondialdehyde (MDA) in the roots and leaves, enhanced the activities of antioxidative enzymes such as superoxide dismutase (SOD) and catalase (CAT), and restored the levels of endogenous hormones including gibberellin (GA3), indole-3-acetic acid (IAA), methyl jasmonate (Ja-ME), and abscisic acid (ABA). Furthermore, the low-concentration of the extract positively impacted the disorganized chloroplast structures. In contrast, a high-concentration of the extract failed to revert most of these stress indicators. Conclusion: Low concentrations of astringent seed water extract effectively alleviate the inhibitory effects of aluminum ions on seed and seedling. This implies that in natural environments, the proximity of healthy seeds to astringent seeds could potentially enhance their growth. [ABSTRACT FROM AUTHOR]

The Chinese fir (Cunninghamia lanceolata) is a significant species utilized in afforestation efforts in southern China. It is distinguished by its rapid growth and adaptability to diverse environmental conditions. The GRAS gene family comprises a group of plant-specific transcription factors that play a pivotal role in plant growth and development, response to adversity, and hormone regulatory networks. However, the exploration of the GRAS family in gymnosperm Chinese fir has not yet begun. In this study, a total of 43 GRAS genes were identified in the whole genome of Chinese fir, and a phylogenetic analysis classified them into nine distinct subfamilies. Gene structure analysis revealed that the majority of ClGRAS genes lacked introns. It is notable that among these proteins, both ClGAI and ClGRA possess distinctive DELLA structural domains. Cis-acting element analysis revealed that nearly all ClGRAS genes contained light-responsive elements, while hormone-responsive elements, environmental-responsive elements (low-temperature- or defense-responsive elements), and meristem-organization-related elements were also identified. Based on transcriptome data and RT-qPCR expression patterns, we analyzed the expression of ClGAI and ClRGA genes across different developmental stages, hormones, and three abiotic stresses. Subcellular localization analysis demonstrated that ClGAI and ClRGA were localized to the nucleus. Transcriptional activation assays showed that both genes have self-activating activity. In conclusion, the results of this study indicate that the ClGRAS gene family is involved in the response of Chinese fir to environmental stress. Further research on the ClDELLA genes provides valuable information for exploring the potential regulatory network of DELLA proteins in Chinese fir. [ABSTRACT FROM AUTHOR]

In order to study the propagation behavior of acoustic emission (AE) signals in wood, COMSOL 3D simulation models were established for four kinds of wood specimens, including Populus simonii, Castanopsis hystrix, Pinus sylvestris and Cunninghamia lanceolata. The elastic wave point source was simulated using a given displacement method, and then, the longitudinal propagation of the AE signal along the wood was analyzed with the help of the stress maps of the simulation process. The longitudinal wave velocity of the AE source was calculated by the time difference of arrival (TDOA) method with respect to the time difference between the two posi‐ tions of the AE source arriving at the surface of the model. The AE tests were carried out on the wood specimen under the same condi‐ tions and the longitudinal wave velocities were calculated. The final results were consistent with the simulation model. The results showed that the relative errors between the simulated and tested longitudinal wave velocities of Populus simonii, Castanopsis hystrix, Pinus sylvestris and Cunninghamia lanceolata were 1. 47%, 1. 04%, 0. 46% and 2. 33%, respectively. The simulation model can ob‐ jectively reflect the propagation behavior of the AE signals in wood, which provided a new way to visualize the propagation process of the AE signals in wood. However, the relative error of AE signal amplitude was large, and the model cannot objectively respond to the change rule of amplitude in wood. [ABSTRACT FROM AUTHOR]

Intensified atmospheric nitrogen (N) deposition, coupled with increased application of N fertilizers in forest plantations, has resulted in N and phosphorus (P) imbalance in the forest soil system. However, it is seldom investigated whether an addition of N counteracts the effects of low P stress on N and P nutrient absorption and utilization efficiencies. Thus, we conducted a greenhouse experiment on three clones of Chinese fir (clones 061, 020 and 2 C) with four levels of N addition (2, 5, 10, and 15 mmol·L− 1 sodium nitrate) under normal P supply (1.0 mmol·L− 1 KH2PO4), moderately P deficiency (0.5 mmol·L− 1 KH2PO4) and severely P deficiency (0.1 mmol·L− 1 KH2PO4) conditions. The results showed that addition of moderate concentration of N (10 mmol·L− 1 N) significantly promoted root elongation, root dry mass accumulation, root surface area and root APase activity of Chinese fir seedlings under P-deficient conditions, with distinct clonal variation. Seedlings of clone 061 showed the most root APase activity in response to addition of moderate concentration of N under P deficient condition while clones 061 and 020 had the longest roots and the largest root dry mass accumulation. Under severe P deficiency, the N and P absorption efficiencies (NAE and PAE) of Chinese fir seedlings increased with increasing N concentration, while the N and P utilization efficiencies (NUE and PUE) decreased. The findings demonstrate that addition of moderate level of N modulates the adaptive responses of Chinese fir to P deficiency and enhances the absorption efficiency of P. The variation among clones suggests that the responses are genetically controlled and there exists great potential for breeding highly phosphorus efficient genotypes under coupled conditions of P deficiency and increased atmospheric nitrogen deposition. [ABSTRACT FROM AUTHOR]

Significant market value discrepancies exist between clear and knotty Chinese fir (Cunninghamia lanceolata) wood, distinguished not only by their aesthetic variations but also by their distinct material properties. This study aimed to explore the differences in physical and mechanical properties between clear and knotty Chinese fir wood. Nine standard trees were chosen from a 26-year-old Chinese fir plantation for the experiment. Subsequent to felling, trunk segments below 7 m in length were transported to the laboratory. For each tree, detailed preparations were made to obtain clear and knotty wood specimens, and these distinct wood specimens were subjected to thorough physical and mechanical assessments. The results revealed significant variations in properties between clear and knotty Chinese fir wood. The shrinkage and swelling coefficients of knotty wood were generally lower than those of clear wood, except for higher radial and tangential air-dry shrinkage. Specifically, the swelling ratio of knotty wood was at least 0.40% lower, and the oven-dry shrinkage was at least 0.58% lower than that of clear wood. Knotty wood exhibited higher air-dry and oven-dry densities, with its density being at least 0.15 g cm−3 higher than that of clear wood. However, its mechanical properties, including tensile strength, compression strength, impact bending strength, bending strength, and modulus of elasticity, were lower than those of clear wood. For instance, the tensile strength parallel to the grain of clear wood was 40.63 MPa higher, the modulus of elasticity was 1595 MPa higher, and the impact bending strength was 27.12 kJ m−2 greater than that of knotty wood. Although the tangential and radial surface hardness of knotty wood increased significantly compared to clear wood, the end hardness remained relatively lower. Overall, knotty Chinese fir wood displayed enhanced physical properties, whereas clear wood showcased superior mechanical properties. Careful selection between clear and knotty wood is recommended based on the specific requirements of wooden structural elements to optimize timber resource utilization. [ABSTRACT FROM AUTHOR]

Mixed stands of tree species with complementary traits can modulate stand growth and timber quality. At the Fengshushan Forest Farm, mixtures of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) with Liquidambar formosana Hance, Schima superba Gardner & Champ., Elaeocarpus sylvestris (Lour.) Poir., Cinnamomum camphora (L.) Presl, and Chinese fir monoculture were established. Differences in stand growth and timber quality among these mixtures were assessed and a test was conducted to evaluate the factors influencing the mixture effects. The average diameter at breast height, tree height, stand volume, and individual tree annual increment of mixtures generally exceeded those of Chinese fir monocultures but not necessarily those of broad-leaved monocultures. When the net interaction between species was complementary, overyielding in mixtures occurred (RPfir,bl > 0), which was influenced significantly by stand density, soil properties, and timber quality. The timber quality and wood production of Chinese fir were enhanced by mixture with some broad-leaved species, with reduced slenderness and knottiness in mixtures, and notable increases in medium- (average outturn rates of 56.13%) and large-diameter (11.71%) timber in C. lanceolata/C. camphora mixture. The growth and timber quality of Chinese fir are largely promoted when grown mixed with broad-leaved species. Overyielding at the stand level occurs where Chinese fir compensates for the underperformance of broad-leaved trees. [ABSTRACT FROM AUTHOR]

Over the past three decades, China has implemented extensive reforestation programs, primarily utilizing Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) in southern China, to mitigate greenhouse gas emissions and counter extreme climate events. However, the effects of drought on the carbon sequestration capacity of these forests, particularly during the trunk wood stage, remain unclear. This study, conducted in Huitong, Hunan, China, from 2008 to 2013, employed the eddy covariance method to measure carbon dioxide (CO2) and water fluxes in Chinese fir forests, covering a severe drought year in 2011. The purpose was to elucidate the dynamics of carbon and water fluxes during a drought year and across multi-normal year averages. The results showed that changes in soil water content (−8.00%), precipitation (−18.45%), and relative humidity (−5.10%), decreases in air temperature (−0.09 °C) and soil temperature (−0.79 °C), and increases in vapor pressure deficit (19.18%) and net radiation (8.39%) were found in the drought year compared to the normal years. These changes in environmental factors led to considerable decreases in net ecosystem exchange (−40.00%), ecosystem respiration (−13.09%), and gross ecosystem productivity (−18.52%), evapotranspiration (−12.50%), and water use efficiency (−5.83%) in the studied forests in the drought year. In this study, the occurrence of seasonal drought due to uneven precipitation distribution led to a decrease in gross ecosystem productivity (GEP) and evapotranspiration (ET). However, the impact of drought on GEP was greater than its effect on ET, resulting in a reduced water use efficiency (WUE). This study emphasized the crucial role of water availability in determining forest productivity and suggested the need for adjusting vegetation management strategies under severe drought conditions. Our results contributed to improving management practices for Chinese fir plantations in response to changing climate conditions. [ABSTRACT FROM AUTHOR]

The relationship between tree radial growth and climate factors is intricate and affected by various factors related to global climate change. Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.)] is a crucial fast-growing timber species in subtropical China. Its productivity, primarily determined by radial growth, has been influenced by climate change. Our study aimed to explore growth patterns and elucidate the correlation between radial growth and climate factors in Chinese fir plantations across four distinct climatic regions. Through correlation analysis and structural equation model (SEM), we explained the relationship between radial growth trends and climate factors. The results showed that monthly radial growth differed among the four production areas, with an "unimodal curve" in Fujian and Jiangxi, a "bimodal curve" in Hunan, and a "trimodal curve" in Yunnan. Radial growth was positively correlated with temperature and precipitation. The dryness index had a weak correlation with radial growth in Fujian and Jiangxi but a significant positive correlation in Hunan and Yunnan. SEM analyses indicated path coefficients for biological factors influencing radial growth (0.352 in Fujian, 0.616 in Jiangxi, 0.595 in Hunan, and 0.528 in Yunnan) and climate factors (-0.003 in Fujian, 0.150 in Jiangxi, 0.265 in Hunan, and 0.005 in Yunnan). The factors affecting radial growth were the least in Fujian and the most in Yunnan, indicating greater climate sensitivity in the radial growth of Chinese fir from coastal to inland areas. These results enhance our understanding of climate impacts on forest productivity and offer a scientific basis for sustainably managing subtropical plantations under climate change. [ABSTRACT FROM AUTHOR]

Temperature can significantly (P < 0.05) affect plant growth by modifying water use strategies, which are determined by intrinsic water use efficiency (WUEi). Red Heart Chinese Fir (Cunninghamia lanceolata) is one of the most important ecological and economic plantation species in China. However, the C. lanceolata water use strategy in response to increased temperatures and uneven temporal distribution of precipitation during the growing season is rarely reported.In a 7‐year‐old C. lanceolata plantation, differences in WUEi and C and N concentrations in different organs were analysed by anova, and the δ13C stable isotope, C, and N concentrations in stems determined at different tree heights. Stepwise regression and variance inflation factor were used to remove autocorrelated factors, and structural equation modelling was then used to explore relationships between WUEi and climate and biological factors.WUEi differed significantly between leaf and branch at different standardized precipitation evapotranspiration indices (SPEI). WUEi and N concentration decreased with age. The highest WUEi in branches and leaves were 92.7 and 88.4 μmol·mol−1 in 2020 (SPEI = 0.00), respectively. δ13C increased with relative tree height but N concentration and C/N ratio were not affected. Air temperatures has increased in between 2014 and 2020.WUEi and N concentration decreased with increasing branch and leaf age, but C concentration increased. SPEI significantly positively affected WUEi (P < 0.05), and WUEi was significantly negatively related to C concentration, which is consistent with the trade‐off between C and water. [ABSTRACT FROM AUTHOR]

Summary: A comprehensive analysis was conducted using optical microscopy based on wood anatomy to enhance the preservation of wooden components in Tingbao Yang's former residence. This study identified wood samples, and statistical examination of wood species, variations in their configuration, physical and mechanical properties, and natural durability were examined. The principles for wood species selection were assessed. Findings indicate that Cunninghamia lanceolata , Pseudotsuga spp., Populus spp. and Ulmus spp. are the primary choices for these wooden components. However, certain portions incorporate Larix sect. Multiseriales , Picea brachytyla , Pinus bungeana , Pinus massoniana , Castanea sp. and Quercus subg. Lepidabalanus , sect. Prinus. Pseudotsuga spp., C. lanceolata , Ulmus spp. and Populus spp. are primarily utilized for wooden columns and melon columns. However, C. lanceolata , Ulmus spp. and Populus spp. possess inadequate parallel grain compressive strength for load-bearing compression wooden components. C. lanceolata and Ulmus spp. are widely utilized in beams, lintels, purlins, and rafters owing to their exceptional bending strength. It was noted that Castanea sp. and Quercus subg. Lepidabalanus , sect. Prinus wood varieties demonstrate superior resistance to rotting and insects compared with other types of wood. The selection of wood species for the ancient buildings of Tingbao Yang's former residence relies on crucial principles, such as the suitability of wood properties and local selection. This selection process involves analyzing the wood properties, assessing the natural durability of wooden components, and considering the distribution of forest resources in Henan Province. [ABSTRACT FROM AUTHOR]

Quantifying forest stand parameters is crucial in forestry research and environmental monitoring because it provides important factors for analyzing forest structure and comprehending forest resources. And the estimation of crown density and volume has always been a prominent topic in forestry remote sensing. Based on GF-2 remote sensing data, sample plot survey data and forest resource survey data, this study used the Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and Pinus massoniana Lamb. as research objects to tackle the key challenges in the use of remote sensing technology. The Boruta feature selection technique, together with multiple stepwise and Cubist regression models, was used to estimate crown density and volume in portions of the research area's stands, introducing novel technological methods for estimating stand parameters. The results show that: (i) the Boruta algorithm is effective at selecting the feature set with the strongest correlation with the dependent variable, which solves the problem of data and the loss of original feature data after dimensionality reduction; (ii) using the Cubist method to build the model yields better results than using multiple stepwise regression. The Cubist regression model's coefficient of determination (R 2) is all more than 0.67 in the Chinese fir plots and 0.63 in the P. massoniana plots. As a result, combining the two methods can increase the estimation accuracy of stand parameters, providing a theoretical foundation and technical support for future studies. [ABSTRACT FROM AUTHOR]

Cunninghamia lanceolata (Lamb.) Hook accounts for 12% of the total forest area in southern China, second only to Masson pine forests, and is an important part of the forest landscape in this region, which has a significant impact on the overall forest structure in southern China. In this study, we used kernel density analysis, landscape index calculation, variance test, and Markov prediction to analyze and forecast the evolution trend of landscape pattern in the central area of C. lanceolata in ten years. The objective is to investigate the change trend of the spatial pattern of C. lanceolata landscape in the long time series and its possible impact on zonal vegetation, as well as the macro-succession trend of C. lanceolata under the current social and economic background, and to make a scientific and reasonable prediction of its future succession trend. The current and future forecast results show that the landscape fragmentation degree of C. lanceolata is intensified, the erosion of bamboo forest is continuously intensified, and the landscape quality is continuously low. These results provide a reference for the future development direction of C. lanceolata and emphasize the need for targeted C. lanceolata management strategies in the future development of C. lanceolata, emphasizing the strengthening of monitoring, controlling harvesting, and managing bamboo competition in order to balance wood production with landscape quality and ecosystem stability. [ABSTRACT FROM AUTHOR]

Biochar and organic fertilizer can significantly increase soil organic carbon (SOC) and promote agricultural production, but it is still unclear how they affect forest SOC after. Here, low-quality plantation soil was subjected to four distinct fertilization treatments: (CK, without fertilization; BC, tea seed shell biochar alone; OF, tea meal organic fertilizer alone; BCF, tea seed shell biochar plus tea meal organic fertilizer). Cunninghamia lanceolata (Lamb.) Hook and Cyclobalanopsis glauca (Thunb.) Oersted seedlings were then planted in pots at the ratios of 2:0, 1:1, and 0:2 (SS, SQ, QQ) and grown for one year. The results showed that the BCF treatment had the best effect on promoting seedling growth and increasing SOC content. BCF changed soil pH and available nutrient content, resulting in the downregulation of certain oligotrophic groups (Acidobacteria and Basidiomycetes) and the upregulation of eutrophic groups (Ascomycota and Proteobacteria). Key bacterial groups, which were identified by Line Discriminant Analysis Effect Size analysis, were closely associated with microbial biomass carbon (MBC) and SOC. Pearson correlation analysis showed that bacterial community composition exhibited a positive correlation with SOC, MBC, available phosphorus, seedling biomass, and plant height, whereas fungal community composition was predominantly positively correlated with seedling underground biomass. It suggested that environmental differences arising from fertilization and planting patterns selectively promote microbial communities that contribute to organic carbon formation. In summary, the combination of biochar and organic fertilizers would enhance the improvement and adaptation of soil microbial communities, playing a crucial role in increasing forest soil organic carbon and promoting tree growth. [ABSTRACT FROM AUTHOR]

Premise: The impact of inbreeding on biological processes is well documented in individuals with severe inbreeding depression. However, the biological processes influencing the adaptive growth of normal selfed individuals are unknown. Here, we aimed to investigate how inbreeding affects gene expression for adaptive growth of normal selfed seedlings from a self‐fertilizing parent in Chinese fir (Cunninghamia lanceolata). Methods: Using RNA‐seq data from above‐ and underground tissues of abnormal and normal selfed seedlings, we analyzed GO biological processes network. We also sequenced small RNAs in the aboveground tissues and measured the copy number variations (CNV) of the hub genes. Results: Phenotypic fitness analysis revealed that the normal seedlings were better adapted than their abnormal counterparts. Upregulated differentially expressed genes (DEGs) were associated with development processes, and downregulated DEGs were mainly enriched in fundamental metabolism and stress response. Results of mRNA‐miRNA parallel sequencing revealed that upregulated target genes were predominantly associated with development, highlighting their crucial role in phosphorylation in signal transduction networks. We also discovered a moderate correlation (0.1328 < R2 < 0.6257) between CNV and gene expression levels for three hub genes (TMKL1, GT2, and RHY1A). Conclusions: We uncovered the key biological processes underpinning the growth of normal selfed seedlings and established the relationship between CNV and the expression levels of hub genes in selfed seedlings. Understanding the candidate genes involved in the growth of selfed seedlings will help us comprehend the genetic mechanisms behind inbreeding depression in the evolutionary biology of plants. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Guangxi Normal University - Natural Science Edition is the property of Gai Kan Bian Wei Hui 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.)

In order to provide a theoretical basis for the selection and breeding of improved varieties of Taxodiaceae plants, the growth of Guangxi characteristic Cunninghamia lanceolata were investigated by using five dominant tree comparison methods. A total of 35 superior trees and 175 dominant trees were selected. Through statistical analysis, the range for the selection of superior trees was determined: DBH and volume were 207% and 569% of the average value of dominant trees, respectively, and tree height was greater than the average value of dominant trees. According to this range, 35 candidate superior trees were re-selected, and 19 superior trees of grade I and 6 superior trees of grade II were obtained. The selection rates were 54. 29% and 17. 14%, respectively, which could provide high-quality germplasm materials for the construction of clonal seed orchard of Cunninghamia lanceolata. [ABSTRACT FROM AUTHOR]

Determining an appropriate grain size is crucial in landscape pattern analysis and ecological research. In order gain deeper insights into the spatial diversity and dynamic characteristics of landscape pattern, based on the survey data of the 12 hm² large plot in Jiangxi Guanshan National Nature Reserve in 2015 and 2020, the grain size effect of landscape indices in eight different landscape types within the range of 5-50 meters were analyzed; the variation coefficients were used to reveal the changing characteristics of different landscape pattern indices as the grain size increased, and the optimal grain size was selected based on the inflection points of changes in various landscape indices. The results were as follows: (1) Based on the importance value analysis, eight different landscape types were identified in the arbor layer of the plot, including forest gap, bamboo forest, Cunninghamia lanceolata forest, Pinus massoniana forest, broad-leaved forest, bamboo and Cunninghamia lanceolata mixed forest, bamboo and Pinus massoniana mixed forest, Cunninghamia lanceolata and Pinus massoniana mixed forest. (2) The overall distribution of patches in the landscape was relatively balanced, and the distribution pattern remained relatively stable. At larger spatial grain size, the aggregation of each landscape type increased, leading to a higher probability of landscape merging. In contrast, at smaller granularity, there was a noticeable trend of fragmentation in landscape types, providing a more comprehensive display of the quantity, density, and shape of each landscape type. Patch density (PD), number of patches (NP), edge density (ED), landscape shape index (LSI), mean fractal dimension index (FRAC_MN), contagion index (CONTAG) exhibited significant negative correlations with increasing grain size, while mean patch area (AREA_MN), Shannon's diversity index (SHDI), Shannon's evenness index (SHEI) exhibited significant positive correlations with increasing grain size. (3) The coefficients of variation for landscape indices PD, NP, ED, LSI, and AREA_MN were the highest, combining landscape structural stability and diversity, the changes in different landscape indices were primarily concentrated around the inflection point at 5 meters. These results illustrate the diversity of landscape types, with the coefficient of variation reflecting the most sensitive characteristics of landscape pattern changes. This study suggests that a grain size of 5 meters is optimal for studying the landscape pattern of subtropical evergreen broad-leaved forests in Guanshan, Jiangxi. This study provides favorable evidence for the restoration of forest resources and stand stucture. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is one of the essential elements for plant growth and is a key factor in maintaining the productivity of subtropical forest ecosystems. Chinese fir (Cunninghamia lanceolata) is mainly distributed in subtropical areas of China, and its soil acidification and phosphorus utilization efficiency are low. It is of great significance to study the effects of Chinese fir plantation transformation on soil P for the stability of ecosystem and sustainable forest management. In this study, the rhizosphere and non-rhizosphere soils were collected from the replanted Chinese fir plantation, Castanopsis hystrix plantation, Mytilaria laosensis plantation and the mixed plantation of Castanopsis hystrix and Mytilaria laosensis on the cutting-blank of Chinese fir plantation in South Asia, and the effects of soil P component and transformation on the transformation of Chinese fir plantation into broad-leaved forest were studied. The results were as follows: (1) The content of microbial biomass phosphorus and the activity of acid phosphatase in rhizosphere and non- rhizosphere soil of the modified Castanopsis hystrix plantation, Mytilaria laosensis plantation and the mixed plantation of Castanopsis hystrix and Mytilaria laosensis were significantly higher than those of Chinese fir plantation. The contents soil total phosphorus of Castanopsis hystrix plantation and the mixed plantation of C. hystrix and Mytilaria laosensis were more easily converted to quick available phosphorus than those of Chinese fir plantation and M. laosensis plantation. (2) The contents of calcium chloride extraction phosphorus in rhizosphere and non-rhizosphere soils of Castanopsis hystrix plantation and the mixed plantation of C. hystrix and Mytilaria laosensis were significantly higher than those of Chinese fir plantation and M. laosensis plantation, and the contents of enzyme extraction phosphorus, hydrochloric acid extraction phosphorus and citric acid extraction phosphorus in rhizosphere and non-rhizosphere soils of M. laosensis plantation and Castanopsis hystrix/Mytilaria laosensis mixed plantation were significantly higher than those of Chinese fir plantation and Castanopsis hystrix plantation. (3) RDA results showed that soil water content and microbial biomass carbon were the key factors regulating P components in rhizosphere and non-rhizosphere soils, respectively. In summary, the transformation of Chinese fir plantation into broad-leaved forest is conducive to the storage and supply of forest soil P, and this study provides an important scientific reference for tree species selection and management strategies to improve soil P availability in south subtropical plantations. [ABSTRACT FROM AUTHOR]

Introduction: Soil microbial functional traits are key indicators of soil microbial ecological traits; however, how mixing patterns of Chinese fir and broadleaved trees drive soil microbial functional trait variation at the aggregate scale and how soil microbial functional traits are linked to soil fertility factors have largely not been determined. Methods: In this study, soil from the 0-20 cm depths in three Chinese fir plantations was collected, and the soil samples were separated into >2 mm (large macro-aggregate), 0.25-2 mm (macro-aggregate) and <0.25 mm (microaggregate) by complying with an optimal moisture sieving procedure. The metabolic activities, functional diversity and different carbon sources utilization characteristics of the soil microorganisms were determined by the Biolog Eco microplate method. Results: In all Chinese fir plantations, micro-aggregates (<0.25 mm) consistently exhibited the highest levels of microbial metabolic activity, a more uniform carbon source utilisation capacity, and the highest microbial diversity. Microaggregates also showed elevated levels of soil organic carbon (OC), total nitrogen (TN), total phosphorus (TP), and higher ratios of C/N and C/P compared to large macro-aggregates and macro-aggregates, indicating that micro-aggregates contain more resources available to soil microorganisms. Soil OC, TN, and TP content were enhanced by integration with Michelia macclurei, suggesting that this combination promotes relatively favourable soil conditions for microbial growth and multiplication. This, in turn, promotes microbial metabolic activity. Furthermore, redundancy and correlation analyses showed that soil OC, TN, and TP were identified as principal determinants of soil microbial functional properties in Chinese fir plantations. Discussion: In summary, mixed cultivation and aggregate size influenced microbial functional properties via soil nutrient alterations. Consequently, adopting a mixed cultivation approach of Chinese fir and broadleaved trees is advocated in the subtropical regions of Guangxi. Employing a diversity of tree species, including M. macclurei, is recommended for optimal soil quality preservation. [ABSTRACT FROM AUTHOR]

In order to study the effects of wildfires on soil carbon dioxide (CO2) emissions and microbial communities in planted forests, Pinus massoniana Lamb. and Cunninghamia lanceolata (Lamb.) Hook. forests were selected as the research subjects. Through a culture test with 60 days of indoor constant temperature, the soil physical and chemical properties, organic carbon mineralization, organic carbon components, enzyme activity, and microbial community structure changes of the two plantations after fire were analyzed. The results showed that wildfires significantly reduced soil CO2 emissions from the Pinus massoniana forests and Cunninghamia lanceolata forests by 270.67 mg·kg−1 and 470.40 mg·kg−1, respectively, with Cunninghamia lanceolata forests exhibiting the greatest reduction in soil CO2 emissions compared to unburned soils. Bioinformatics analysis revealed that the abundance of soil Proteobacteria in the Pinus massoniana and Cunninghamia lanceolata forests decreased by 6.00% and 4.55%, respectively, after wildfires. Additionally, redundancy analysis indicated a significant positive correlation between Proteobacteria and soil CO2 emissions, suggesting that the decrease in Proteobacteria may inhibit soil CO2 emissions. The Cunninghamia lanceolata forests exhibited a significant increase in soil available nutrients and inhibition of enzyme activities after the wildfire. Additionally, soil CO2 emissions decreased more, indicating a stronger adaptive capacity to environmental changes following the wildfire. In summary, wildfire in the Cunninghamia lanceolata forests led to the most pronounced reduction in soil CO2 emissions, thereby mitigating soil carbon emissions in the region. [ABSTRACT FROM AUTHOR]

Background: The bark of Chinese fir (Cunninghamia lanceolata), the largest afforestation tree species in the forest areas of southern China, is susceptible to injuries and bites from small animals. The population of small animals has recently increased owing to improvements in the ecological environment across various forested areas, thus increasing the incidence of injuries in the bark of Chinese fir. Following such injuries, the bark secretes light yellow or milky white secretions, the function of which remains unclear. The present study aimed to reveal the antibacterial effect of exudates of different Chinese fir cultivars on five bacterial species. Methods: The research involved three-year-old plantations of Taxus chinensis var. koraiensis and Yangkou3 and three-year-old container plantations of Taxus chinensis var. pendula, Yang 061, and Yang 020. The antibacterial effects of exudates were analyzed using the filter paper diffusion method. The minimum inhibitory concentration for each secretion and the bacterial inhibition zone were determined. Results: The exudates of the different Chinese fir bark exhibited notable antibacterial effects on Bacillus subtilis, Salmonella paratyphi B, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. However, the extent of these antibacterial effects varied among the different Chinese fir cultivars, as the minimum inhibitory concentrations (MICs) of the exudates against the five bacterial species varied. The mean MIC of Pseudomonas aeruginosa was lower potency, whereas that of Escherichia coli was the lowest. Notably, the antibacterial efficacy of the exudates was mainly influenced by the composition of the secretions rather than the number of secretions, with organic acid compounds and terpenoids potentially contributing to the antibacterial effects against E. coli and Bacillus subtilis, respectively. Conclusion: This study demonstrates the antibacterial effect of wound secretion of different Chinese fir cultivars, highlighting their varying efficacy on different bacterial species. Moreover, the antibacterial ability of the exudates of the strains was mainly determined by the composition of the wound secretions, and there was no noticeable relationship with the number of wound secretions. The results of this study offers a theoretical basis for screen Chinese fir cultivars with high-disease-resistant. [ABSTRACT FROM AUTHOR]

The tensile strength of roots and the friction characteristics of the root–soil interface of tree species are the indicators that play a crucial role in understanding the mechanism of soil reinforcement by roots. To calculate the effectiveness of the reinforcement of soil by tree roots based on essential influencing parameters, typical trees in the coastal region of southeastern China selected for this study were subjected to tests of the tensile mechanical properties of their roots, as well as studies on the friction characteristics of the root–soil interface and the microscopic interfaces. The results indicated that in the 1–7 diameter classes, the root tensile strength of both Pinus massoniana and Cunninghamia lanceolata was negatively correlated with the root diameter in accordance with the power function. The root tensile strength of these two trees, however, was positively correlated with the lignin content but negatively correlated with cellulose and hemicellulose contents. The shear strength at the root–soil interface and the vertical load exhibited a constitutive relationship, which followed the Mohr–Coulomb criterion. As the root diameter increased, both the cohesion and the friction coefficients at the root–soil interface gradually increased, but the growth rate stood at around 15%. The cohesion value of the root–soil interface of the two trees decreased linearly with the increase in soil moisture content within the range of 25 to 45%. At the microinterface, the root surface of C. lanceolata exhibited concave grooves and convex ridges that extended along the axial direction of roots, with their height differences increasing with the enlargement of the root diameter. The rough surface of P. massoniana roots had areas composed of polygonal meshes, with an increase observed in the mesh density with increasing root diameter. [ABSTRACT FROM AUTHOR]

Reforestation after forest clear‐cutting is an effective measure to increase soil organic carbon (SOC) sequestration; still, the soil C balance under reforestation and the role of microbial communities in that process remain to be determined. Samples of organic (0–2 cm) and mineral (2–10 cm) horizons were collected from the 7‐, 15‐, 20‐, 29‐, and 36‐year‐old forest stands of Chinese fir (Cunninghamia lanceolata) after plantation clear‐cutting in subtropical zone under the condition of phosphorus limitation. Particulate organic carbon (POC), mineral‐associated organic carbon (MAOC), microbial phospholipid fatty acids (PLFAs), and enzymatic activities for C, nitrogen (N), and phosphorus (P) acquisition were analyzed. The lowest contents of POC (10%) and MAOC (13%) in the organic horizon were found in 7‐year‐old stands due to the slow tree regrowth and extensive decomposition of SOC in the first years of forest regrowth. POC (2.0×) and MAOC (0.8×) increases in the organic horizon with forest age were attributed to the stand development and accumulation of above‐ and belowground litter. The organic horizon had a higher POC:MAOC ratio than the mineral (0.7–1.1 vs. 0.2–0.5), indicating lower SOC stability in the first one. The ratio of POC:MAOC increased with the Gram‐positive to Gram‐negative bacteria (G+:G‐) ratio, pointing out that microbial communities developed a specific community structure and substrate utilization strategies of organic matter under plantation restoration. The increase of total PLFAs and the G+:G‐ ratio was closely linked with the microbial C and P limitations, indicating that microorganisms shifted community structure to slow‐growing species and increased their content to cope with the C and P restrictions. In the soils of young plantations, microorganisms were limited by C and P; however, the C limitation was alleviated in the 36‐year‐old plots in the organic horizon due to increased litter input, whereas the P limitation was not. This discrepancy between C and P limitation suppressed the decomposition of litter entering the soil, which was seen in decreased specific activity of C degrading enzymes and led to the accumulation of POC in the organic horizon. Thus, soil C sequestration under reforestation of Chinese fir can be controlled by the amount of litter entering the soil and by metabolic C, N, and P limitations that force microorganisms to shift community structure and change their activity. [ABSTRACT FROM AUTHOR]

Background: Soil microbial community composition with stand development may be changed due to the variations in canopy structure, understory vegetation, root traits, edaphic conditions, and litter inputs. However, it is still uncertain to what extent these biotic and abiotic factors shape the soil microbial community composition in Chinese fir (Cunninghamia lanceolata) plantations, which are widely planted in southern China. Methods: Amplicon sequencing was used to analyze the diversity and composition of soil bacterial and fungal communities at two soil depths across four developmental stages of Chinese fir plantations. Results: Both the bacterial and fungal communities were significantly different between stand age groups. As stand aged, oligotrophic bacteria decreased in abundance while copiotrophic bacteria increased. Meanwhile, fungal functional groups connected to plants decreased in abundance while that of saprotrophic fungi significantly increased. The variance in bacterial community was mainly attributed to soil variables regarding carbon and nutrient availability, whereas the greatest fraction of fungal community dissimilarity was determined by plant-specific factors such as aboveground stand structure and tree root traits. The chemical composition of litter had a major effect on the soil fungal community, whereas the litter traits had no effect on the bacterial community. Conclusions: The potential drivers of soil fungi and bacteria differ in Chinese fir plantations. By accounting for the impacts of various environmental components, it is possible to anticipate the response of soil bacterial and fungal assemblages to forest management regime implemented in Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Decay levels of wooden components in the Yang former residence were classified using polarized light and fluorescence methods. Analysis of the decay cause was conducted based on external conditions and wood species characteristics. The polarization and fluorescence effects revealed that there were varying degrees of decay in larch (Larix potaninii var. australis), spruce (Picea brachytyla), lace-bark pine (Pinus bungeana), Masson pine (Pinus massoniana), Chinese Douglas fir (Pseudotsuga sinensis), Chinese fir (Cunninghamia lanceolata), poplar (Populus tomentosa), and elm (Ulmus pumila). The primary factors contributing to decay included the inherent low natural durability of the wood species and adverse external conditions, such as damaged roofs, missing dripping water and tiles causing water leakage, uneven indoor and outdoor ground levels, contemporary tile paving indoors, and inadequate ventilation. This study aims to establish a scientific basis for subsequent conservation strategies. [ABSTRACT FROM AUTHOR]

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Recent studies on the intra-annual dynamics of trees were mainly focused on mature trees in natural forests; however, less is known about how topography (e.g., slope's position and aspect) shape the intra-annual xylem formation dynamics of young trees in plantation forests. We monitored intra-annual xylem formation dynamics of 6-year-old Chinese fir (Cunninghamia lanceolata (Lamb.)) trees across two different aspects (northeast and southwest) and three different positions (upper, middle, and lower) of the slope in a planted forest in subtropical China. We found that the intra-annual xylem formation of trees on the northeast slope aspect (176.98 ± 34.52 cells) was significantly higher than that on the southwest slope aspect (140.19 ± 36.07 cells) due to the higher growth rate (0.67 ± 0.11 cells/day vs. 0.53 ± 0.10 cells/day). In the middle slope position, xylem formation (187.89 ± 19.81 cells) was also significantly higher than that of the upper (147.35 ± 29.08 cells) and lower slope positions (140.51 ± 48.36 cells), resulting from higher growth rate rather than longer growing season length. Our study demonstrated that intra-annual xylem formation dynamics of Chinese fir were altered by different topographic features and therefore encourage the implementation of management strategies that consider different slope aspects and positions to maximize forest productivity. [ABSTRACT FROM AUTHOR]

Thinning is a crucial approach to the near-natural conversion of plantations, contributing to the sustainability of forest management. However, over a rotation, the effects of thinning on tree growth, structure, and species diversity, as well as their scale-dependent outcomes, remain unclear. Ten years after conducting individual tree thinning in a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) monoculture in southwest China, we analyzed the thinning effects within the influence zone (r = 0–2.5 m) centered around stumps and center trees. The results indicate that (1) individual tree thinning did not significantly promote the increment of diameter at breast height, volume, and biomass of Chinese fir. The four nearest Chinese fir around stumps and center trees were in a state of random distribution, high mixing, and dominance; (2) individual tree thinning significantly promoted the formation of species abundance and richness at r = 2–2.5 m. With increased scale, more species were found, leading to increased stability in diameter and species distribution. Linear and nonlinear relationships between diameter classes, mingling, and dominance became more stable; (3) later-coming populations within both modes exhibited a common characteristic of random distribution, high mixing, and disadvantage at each scale, but with significant differences in species composition (kj = 0.22–0.61). These results suggest that individual tree thinning has limited impacts on the growth and structure of retained trees in Chinese fir plantations but significantly enhances the formation of species diversity, demonstrating scale effects. This underscores the feasibility of individual tree thinning in the near-natural conversion of plantations. [ABSTRACT FROM AUTHOR]

The cultivation of Cunninghamia lanceolata (Lamb.) Hook. (Chinese fir) plays a crucial role in enhancing ecological security through water resource preservation and carbon sequestration in China. The biotic and abiotic environmental conditions vary across different stages of plantation, thereby influencing soil nutrient levels and microbial dynamics. However, the interconnection between the soil nutrient cycle and microbial communities within Chinese fir plantations throughout their entire life cycle remains inadequately understood. In this study, conducted across various management stages of Chinese fir plantations in China (including the juvenile stage, first thinning stage, second thinning stage, mature stage, and over-mature stage), we examined the associations among soil organic carbon, soil physicochemical properties, soil enzyme activities, and soil microbial dynamics. Our results revealed that forest management practices significantly modify soil physicochemical properties and enzyme activities across all management stages. Specifically, the concentrations of total soil carbon, soil organic carbon, and soil microbial biomass carbon were notably higher in the over-mature stage compared to other management stages. At the genus level, the five highest contributors belonged to Subgroup2, AD3, Xanthobacteraceae, Elsterales, and Acidobacteriales for the bacterial community. For the fungal community at the genus level, the five highest contributors belonged to Ascomycota, Serendipita, Saitozyma, Mortieralla, and Venturiales. Moreover, anthropogenic thinning activities during the management phase substantially altered both stand and soil environments, as well as the structural characteristics of soil microbial communities. Soil cellulase, soil electrical conductivity (EC), and soil available phosphorus (AP) emerged as key factors influencing the relative abundance of major fungal communities, whereas soil total nitrogen, EC, and AP were identified as critical factors affecting the relative abundance of major bacterial phyla. More microbiological groups increased significantly in the juvenile stage and over-mature stage. Our findings elucidate the intricate relationships between the soil nutrient cycle and soil microbiological dynamics across various forest management stages within Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Fine root traits and their relationships reflect the ecological trade-off strategies of plants in resource investment and are important for understanding the life strategies and growth of plants in response to changes in the environment. We used 16-year-old Chinese fir (Cunninghamia lanceolata Lamb. Hook.) plantations with different slope positions as the research object to explore the morphological, anatomical, and chemical properties of fine roots and their relationships. With increasing root order levels, the morphological, anatomical, and chemical traits of the fine roots of Chinese fir at different slope positions showed similar change trends; however, at the same order level, the differences were large. Under the upper slope site conditions, the average diameter of the second- and third-order roots and the thickness of the third-order root cortex were the highest. However, specific surface area, vascular bundle diameter, and the ratio of third-order roots were higher under the middle-slope site conditions. Under the lower slope site conditions, the specific surface area and specific root length of first-order roots and the root ratio of second-order roots were the highest. The biomasses of the first- and third-order roots on the middle and lower slopes were higher than those on the upper slope. The contents of N and P in fine roots of grades 1–3 Chinese fir showed the order of lower slope > middle slope > upper slope; however, the changes in C/N and C/P ratios showed the opposite trend, indicating differences in the morphological, anatomical, and chemical properties as well as resource acquisition strategies of fine roots of grades 1–3 Chinese fir under different slope positions. There were negative correlations between fine root diameter, N and P contents, and specific root length, indicating an acquisition and conservative resource trade-off relationships between fine root morphological, anatomical, and chemical traits. There were also differences in the relationships between the morphological, anatomical, and chemical traits of Chinese fir fine roots at different slope positions, indicating that the relationships between these traits were affected by slope position change. Chinese fir varieties with root-foraging characteristics ranging from resource conservation to resource acquisition can be selected for planting to improve the productivity of C. lanceolata plantations. [ABSTRACT FROM AUTHOR]

[Objectives] This study was conducted to provide good basic research data for Cunninghamia lanceolata plantations in southern Anhui, so a to improve local ecological, economic and social benefits. [Methods] A22-year-old near-mature C. lanceolata plantation in Lingnan Forest Farm, Xiuning County, Huangshan City, Anhui Province was investigated and analyzed by sample plot survey. [Results] The average DBH value of the C. lanceolata plantation at the lower slope was the largest, 24.7% and 19.2% higher than those at the upper and middle slopes, respectively. The average single plant wood volume at the lower slope was 47.6% and 49.1% higher than those in the upper and middle slopes, respectively. However, the average tree heights at various slope positions showed little difference. Meanwhile, all the indexes showed the phenomenon of semi-shady slope > sunny slope > shady slope under different slope directions. Among them, the effect of slope position on DBH was extremely significant, but the effect of slope direction on DBH was not significant, and slope position, slope direction and the interaction of slope direction and slope position had no significant effects on the tree height of the C. lanceolata plantation. In addition, slope direction and slope position had extremely significant effects on single plant wood volume. From the overall growth situation of the C. lanceolata plantation in Lingnan Forest Farm, the slope position factor had greater effects on various indexes of forest growth than the slope direction factor, mainly manifested in that the lower slope was better than the middle slope, and the middle slope position was better than the upper slope, while although slope direction had some effect on the growth of the C. lanceolata plantation, the influence degree was not a significant as that of slope position. [Conclusions] This study provides some reference for the adjustment and optimization, development and renew of C. lanceolata plantation structure in the later period in this area, a well as some data support for other theoretical research on economic forests. [ABSTRACT FROM AUTHOR]

Species of Cylindrocladiella are saprobic or plant pathogenic, and widely distributed in soil in tropical and sub-tropical regions of the world. Limited information is available about the species diversity and distribution of Cylindrocladiella in China. The aim of this study was to identify the Cylindrocladiella isolates from soils collected in a Cunninghamia lanceolata plantation in the Yunnan Province of southwestern China. Species identification was based on DNA phylogeny of his3, ITS, tef1 and tub2 regions, combined with morphological characteristics. Isolates obtained were identified as Cylindrocladiella longistipitata and a novel species, described here as C. yunnanensis sp. nov. Further studies are required, however, to elucidate the lifestyles of these taxa. [ABSTRACT FROM AUTHOR]

Natural regeneration is deemed essential for maintaining biodiversity and ecosystem stability. Previous studies, however, have primarily concentrated on regions exhibiting limited environmental and climatic variability, overlooking the classification of natural regeneration based on age and source. Research conducted at the mesoscale, characterized by increased environmental variability and the incorporation of neighborhood competition and understory-associated vegetation, enhances our comprehension of the multifaceted influences on natural regeneration. To comprehend this issue, this study implemented 60 plots, each measuring 20 m × 20 m, across five distinct areas of Chongqing, China. Twenty explanatory variables were chosen from five diverse categories: understory vegetation, neighborhood competition, stand structure, climatic factors, and environmental factors. And the naturally regenerated species were classified into seedlings and saplings, as well as endogenous and exogenous species, based on their age and origin. We examined the response of the different categories of natural regeneration to various factors and constructed a structural equation model (SEM) for significant factors to investigate their direct and indirect effects on natural regeneration. A total of 61 regenerated tree species belonging to 29 families and 42 genera were found in the study area, and the naturally regenerating species with high importance values were Quercus fabri, Robinia pseudoacacia, Alangium chinense, Cunninghamia lanceolata, and Ligustrum lucidum. It was found that neighborhood competition and understory-associated vegetation explained the largest proportion (more than 50%) of the variation in the different categories of natural regeneration, and forests with clumped distribution (W), a high mingling index (M) and strong competition (H) had a reduced natural regeneration capacity. Understory-associated herbs significantly reduced natural regeneration and the crowdedness index (C) significantly inhibited the understory-associated herbs, thus indirectly promoting natural regeneration. The shrub cover is significantly and positively correlated with the number of naturally regenerated plants and can be used as an indicator of a forest community's regeneration potential. Understanding the differences in the importance of various factors at the mesoscale, as well as their direct and indirect impacts, can help us further comprehend the mechanisms of natural regeneration and provide a foundation for the sustainable development of forests. [ABSTRACT FROM AUTHOR]

This study aimed to streamline the determination of chlorophyll content in Cunninghamia lanceolate while achieving precise measurements of canopy chlorophyll content. Relative chlorophyll content (SPAD) in the Cunninghamia lanceolate canopy were assessed in the study area using the SPAD-502 portable chlorophyll meter, alongside spectral data collected via onboard multispectral imaging. And based on the unmanned aerial vehicle (UAV) multispectral collection of spectral values in the study area, 21 vegetation indices with significant correlation with Cunninghamia lanceolata canopy SPAD (CCS) were constructed as independent variables of the model's various regression techniques, including partial least squares regression (PLSR), random forests (RF), and backpropagation neural networks (BPNN), which were employed to develop a SPAD inversion model. The BPNN-based model emerged as the best choice, exhibiting test dataset coefficients of determination (R2) at 0.812, root mean square error (RSME) at 2.607, and relative percent difference (RPD) at 1.942. While the model demonstrated consistent accuracy across different slope locations, generalization was lower for varying slope directions. By creating separate models for different slope directions, R2 went up to about 0.8, showcasing favorable terrain applicability. Therefore, constructing inverse models with different slope directions samples separately can estimate CCS more accurately. [ABSTRACT FROM AUTHOR]