IntroductionSoil physicochemical properties and nutrient composition play a significant role in shaping microbial communities, and facilitating soil phosphorus (P) transformation. However, studies on the mechanisms of interactions between P transformation characteristics and rhizosphere microbial diversity in P-deficient soils on longer time scales are still limited.MethodsIn this study, rhizosphere soils were collected from a pure plantation of Parashorea chinensis (P. chinensis) at six stand ages in the subtropical China, and the dynamic transformation characteristics of microbial diversity and P fractions were analyzed to reveal the variation of their interactions with age.ResultsOur findings revealed that the rhizosphere soils across stand ages were in a strongly acidic and P-deficient state, with pH values ranging from 3.4 to 4.6, and available P contents ranging from 2.6 to 7.9 mg·kg-1. The adsorption of P by Fe3+ and presence of high levels of steady-state organic P highly restricted the availability of P in soil. On long time scales, acid phosphatase activity and microbial biomass P were the main drivers of P activation. Moreover, pH, available P, and ammonium nitrogen were identified as key factors driving microbial community diversity. As stand age increased, most of the nutrient content indicators firstly increased and then decreased, the conversion of other forms of P to bio-available P became difficult, P availability and soil fertility began to decline. However, bacteria were still able to maintain stable species abundance and diversity. In contrast, stand age had a greater effect on the diversity of the fungal community than on the bacteria. The Shannon and Simpson indices varied by 4.81 and 0.70 for the fungi, respectively, compared to only 1.91 and 0.06 for the bacteria. Microorganisms play a dominant role in the development of their relationship with soil P.DiscussionIn conclusion, rhizosphere microorganisms in P. chinensis plantations gradually adapt to the acidic, low P environment over time. This adaptation is conducive to maintaining P bioeffectiveness and alleviating P limitation.

Given the challenges of slow growth and low survival rates in the early stages of Parashorea chinensis cultivation, identifying sustainable methods to enhance seedling performance is critical for successful reforestation and conservation efforts. This study aimed to address these by investigating the growth-promoting effects of phosphate-solubilizing bacteria (PSB). One-year-old seedlings of P. chinesis were inoculated with PSB strains isolated from the rhizosphere soil of Parashorea chinensis H. Wang plantations Y3, W5, H8, and a mixed strain (Mix), with inoculated seedling as a control (CK). The effects of inoculation on seedling growth, photosynthetic physiology, plant nutrient status, and physiological indicators were comprehensively evaluated. Results showed that PSB inoculation increased seedling height and basal diameter growth of P. chinensis, with an increase of 1.56 cm and 0.53 mm compared to CK, respectively, though the differences were not significant. The Mix treatment significantly improved photosynthesis, with increases in net photosynthetic rate (106.3%), transpiration rate (93.89%), and intercellular CO2 concentration (75.51%) compared to CK. Nutrient levels including total nitrogen, total phosphorus, and total potassium were significantly increased by 15.98%, 25.54%, and 32.12%, respectively, in the Mix treatments compared to CK. Moreover, stress resistance also improved, with higher proline content, soluble sugar, and soluble protein levels. Antioxidant enzyme activities (SOD, CAT, and POD) were increased by 9.83%, 23.66%, and 292.32%, respectively, while MDA content was significantly reduced by 69.01%. The mixed strain treatment also significantly increased acid phosphatase activity by 111.88%. In conclusion, PSB inoculation, particularly with the mixed strain, promoted growth and nutrient uptake photosynthetic efficiency and stress resistance in P. chinensis seedlings, offering a promising biotechnological solution for improving seedling performance.

IntroductionParashorea chinensis Wang Hsie (Pc) is an endangered tree species endemic to tropical and subtropical China. However, the acidic red soil areas where it is distributed generally face nutrient limitation. The study of the effects of mixed planting on soil biogeochemical processes contributes to the sustainable management and conservation of Pc.MethodsWe selected pure and mixed stands of Pc and collected its rhizosphere and bulk soil samples to clarify the effect of mixed planting on the soil microbial community and the nutrient status.ResultsThe results showed that (1) All stands were strongly acidic phosphorus-deficient soils (pH < 4.0, available phosphorus <10.0 mg·kg−1). There was a significant rhizosphere aggregation effect for soil organic C, total and available N and K, microbial biomass, and inorganic P fraction. (2) The mixed planting significantly increased the soil water content, organic C, available nutrients, the activities of β-1,4-glucosidase and urease, and microbial biomass. The inorganic P fractions are more influenced by rhizosphere, while organic P fractions are more influenced by tree species composition. (3) Fungi and their ecological functions are more susceptible to tree species than bacteria are, and have higher community compositional complexity and α-diversity in mixed plantations. And mixed planting can improve network complexity among key microorganisms. (4) The correlation between soil microorganisms and environmental factors was significantly higher in mixed forests than in pure forests. Soil organic C, available N and P, microbial biomass C and N, β-1,4-glucosidase, and stable P fractions were the key environmental factors driving changes in fungal and bacterial communities.ConclusionIn conclusion, the mixed planting patterns are more advantageous than pure plantations in improving soil physicochemical properties, enhancing nutrient effectiveness, and promoting microbial activities and diversity, especially Pc mixed with Eucalyptus grandis × E. urophylla is more conducive to soil improvement and sustainable management, which provides practical references for relocation protection of endangered tree species and species selection and soil fertility management in mixed planting. In addition, the study highlighted the key role of rhizosphere microenvironment in soil nutrient cycling and microbial community structure, which provides new perspectives for a deeper understanding of soil-microbe-plant interaction mechanisms.

Converting forests from single-species to mixed-species planting affects soil chemical and biological properties, yet its impacts within medicinal plant-based agroforestry systems remain largely unexamined. This research assessed the soil nutrient spectrum and bacterial community composition in a monoculture Pinus massoniana (CK) and various agroforestry models: (M1) Pinus massoniana and Alpina oxyphylla, (M2) Pinus massoniana and Ficus simplicissima, (M3) Pinus massoniana and Amomum villosum, and (M4) Pinus massoniana and Curcuma longa, within both field soil and rhizosphere environments. Results showed significant (p < 0.05) improvements in soil pH and cation exchange capacity (CEC) in agroforestry systems. Agroforestry models exhibited greater variability in soil macronutrient distribution, including nitrogen, potassium, calcium, magnesium, and sulfur (N, K, Ca, Mg, S), compared to monocultures. Specifically, Curcuma longa (M4C.RS) had 46.12 % higher total N content than monoculture Pinus massoniana. Micronutrients were higher in agroforestry rhizospheres, except for total zinc, which was higher in monoculture Pinus massoniana. Bacterial community analysis revealed dominant phyla including Acidobacteriota, Proteobacteria, Actinobacteria, and Chloroflexi. Agroforestry models had higher abundance of Proteobacteria, while monoculture had higher Acidobacteriota. Alpha diversity metrics, including Chao1 and Shannon indices, indicated higher species richness and evenness in agroforestry models, particularly in the rhizosphere of Amomum villosum (M3A.RS) and Curcuma longa (M4C.RS). Phylogenetic analysis indicated greater genetic diversity in agroforestry models, in terms of species richness and phylogenetic variation especially for Proteobacteria. Cluster analysis and NMDS revealed close grouping of agroforestry models, with dbRDA showing significant associations between environmental variables (pH, CEC, and nutrient profile), emphasizing their critical role in shaping bacterial community composition, supported by Spearman correlation. Functional prediction (PICRUSt2) indicated metabolism as the predominant functional category. Therefore, transition from monoculture to agroforestry, especially with Curcuma longa (M4), significantly enhanced soil fertility and ecosystem sustainability.

The transition from monoculture to mixed-species agroforestry systems affects soil organic matter and microbial activity. However, the specific dynamics of these changes, particularly within medicinal plant-based agroforestry, remain underexplored. This study investigates the impact of monoculture Pine (Pinus massoniana) forests and four agroforestry models: (M1) Pinus massoniana and Alpina oxyphylla, (M2) Pinus massoniana and Ficus simplicissima, (M3) Pinus massoniana and Amomum villosum, and (M4) Pinus massoniana and Curcuma longa on soil properties and microbial activity in rhizosphere and non-rhizosphere environments. Our results showed significantly higher pH (4.80) and total nitrogen (N) content (1.77 g kg-1) in the rhizosphere of model (M4) compared to (CK). Total organic carbon (TOC) and carbon fractions (POC, DOC, and MBC) also differed significantly across monoculture and agroforestry models, with highest TOC concentrations (31.70 g kg⁻1) in rhizosphere of CK. Exchangeable cations, including Ca2⁺, and Mg2⁺ were significantly higher in the rhizosphere of agroforestry models compared to CK, particularly in M4, where Ca2⁺ was recorded at 12.03 cmol kg-1 with the highest percent base saturation (PBS) at 90.17%. Enzymes leucine aminopeptidase and polyphenol oxidase varied significantly, with higher activity in the rhizosphere of agroforestry models and greater activity in non-rhizosphere of monoculture. Soil microbial respiration (MRes) revealed substantial differences, with an average 17% decrease in rhizosphere soil for models M2 and M4 and a 20.83% reduction in non-rhizosphere soil for model M1 compared to CK. Generalized Linear Model (GLM) demonstrated a significant positive correlation between TOC and MRes (R2 = 0.885, p < 0.01), indicating that higher TOC levels are linked with increased MRes. In conclusion, model M4 most effectively enhanced soil fertility and nutrient availability followed by the other agroforestry models tested. This suggests that integrating medicinal plants into agroforestry systems is a viable strategy for improving ecosystem functioning compared to monoculture practices.

Purpose: This study explores the accumulation of phenolic acids in soil within monoculture plantations of Eucalyptus, Acacia mangium, contrasting with mixed species plantations containing both species, across various seasons. The research aims to provide insights into how different plantation types and species compositions influence the presence and levels of phenolic acids in soil. Methods: Soil phenolic acid concentrations were determined using HPLC, analyzing seven phenolic acids, including p-hydroxybenzoic, ferulic, coumaric, and benzoic acids. The kinetic adsorption experiments evaluated phenolic acid adsorption rates and quantities across various soil types. An adsorption kinetic model compared these concentrations between monoculture and mixed forest soils. Results: Our findings showed that plantation types, soil positions and seasons significantly impact phenolic acid accumulation. Non-rhizosphere soil in monoculture Eucalyptus plantations exhibited the highest phenolic acid concentration an average (32 µg g-1) across all seasons compared to mixed species plantations. Conversely, the rhizosphere soil of monoculture Acacia mangium displayed the highest content, reaching 71 µg g-1 in March. Notably, four phenolic acids (p-hydroxybenzoic, ferulic, coumaric, and benzoic acids) varied significantly between monoculture and mixed forests. Additionally, adsorption kinetic studies revealed that monoculture Eucalyptus and Acacia mangium soils had higher adsorption capacity compared to mixed species soils. The application of Elovich model yielded the best fit for ferulic and coumaric acids (R2 > 0.45). Conclusion: Mixed species plantations of Eucalyptus and Acacia mangium significantly influence soil phenolic acid levels compared to monoculture forests and induce alterations in soil adsorption characteristics for phenolic acids, potentially impacting soil fertility and productivity.

Parashorea chinensis, an endemic tree species in China’s tropical rainforests, holds ecological and economic importance. Challenges like low resistance, poor quality, and low survival rates hinder its successful cultivation. This study explores the potential of autumn potassium fertilization on Parashorea seedlings from two provenances (Napo and Tianyang). The treatments included no fertilizer (CK-1), a single application of 160 mg K·plant−1 (CK-2), and various potassium levels K1, K2, K3, K4, K5, and K6 (corresponding to 0, 40, 80, 160, 320, and 640 mg·K·plant−1, respectively) combined with nitrogen (200 mg·plant−1) and phosphorus (80 mg·plant−1) fertilization. The findings indicate that autumn potassium application, in conjunction with nitrogen (N) and phosphorus (P) fertilization, significantly enhances seedling height and biomass in both provenances, resulting in an average increase of 101% and 89% under the K4 treatment compared to CK-1 and CK-2, comparatively. Both Napo and Tianyang provenances exhibited distinct responses in photosynthetic rate (2.70 μmol·m−2·s−1 and 1.97 μmol·m−2·s−1, respectively) and stomatal conductance (0.042 mol·m−2·s−1 and 0.029 mol·m−2·s−1, respectively) to the K4 treatment, which proved most effective. The chlorophyll content was significantly higher for Napo provenance with the K3 treatment (74.31%, 58.99%), while for Tianyang, it was higher with the K4 treatment (41.48%, 17.36%), compared to CK-1 and CK-2, respectively. Antioxidant enzymes activity, osmoregulatory capacity, and malondialdehyde content all exhibited variations with potassium application levels, with the K4 treatment offering significant benefits. In Napo provenance, lignin (199.82 mg·g−1) and cellulose (252.38 mg·g−1) peaked at K4, while Tianyang exhibited variation, higher lignin (184.25 mg·g−1) at K3, and cellulose (257.73 mg·g−1) at K4. Nutrient content analysis demonstrates that the K4 treatment enhances nutrient absorption and storage, increasing total N (21.56 mg·kg−1), P (4.69 mg·kg−1), and K (13.49 mg·kg−1) content. A comprehensive analysis reveals that the K4 treatment yields the highest quality scores (1.87, 1.85) and membership values (0.82, 0.68) for both Napo and Tianyang seedlings, with Napo seedlings outperforming their Tianyang provenance. Thus, treatment K4 underscores the effectiveness of autumn potassium applications for robust seedling cultivation and adaptation, offering valuable insights for sustainable cultivation practices.

[Objective]The Parashorea chinensis is an endemic and endangered species in China,and it is classified as a classⅠprotected wild plant.Plantation cultivation is an important means to expand its populations.Phosphorus （P） supply is a major influence on tree growth and development,and P dissolving bacteria plays an important role in P transformation.This research aimed to screen high-efficient phosphatesolubilizing bacteria （PSB） from the rhizosphere soil of P.chinensis plantations of different ages,and explore its P-solubilizing characteristics,so as to provide bacterial resources and culture conditions for the development of microbial fertilizer suitable of P.chinensis.[Method]（1） PSB was isolated and screened from the rhizosphere soil of P.chinensis in different ages by inorganic P solid medium.The physiologica and biochemical tests and 16S rDNA gene sequence were used to further identify 4 strains of PSB.（2） The relationship between the amount of P dissolved by PSB and the pH of the bacterial solution was studied by detecting the dynamics of P solubilization.（3） A single factor experiment was conducted to investigate the P-solubilizing characteristics of high efficiency PSB under different environmental and nutritional factors[Result]（1） A total of 18 strains of phosphorus solubilizing bacteria were isolated and screened,and the 4 strains with the strongest P-solubilizing capacity were P4,P8,P12 and P30 （P-solubilizing capacity was 552.87,559.78,548.53 and 598.89 mg/L,respectively）.（2） Strain P8 was identified as Burkholderia gladioli,P4 and P12 as Burkholderia cepacia,and P30 as Bacillus cereus by physiological,biochemica identification and combined with phylogenetic tree analysis.（3） There was a highly significant （P＜0.01）negative correlation between the pH of the cultures and the amount of phosphorus dissolved by the P4,P8P12 and P30 strains,with correlation coefficients of -0.995,-0.990,-0.985 and -0.997,respectively（4） The results of single factor test showed that the PSBs had the preferable P-solubilizing effects at a temperature of 30-35℃,the pH of 5.5-8.5,the NaCl mass fraction was 0-2.5%,the carbon （C） sources were sucrose,lactose and glucose,and the nitrogen （N） sources were ammonium oxalate and ammonium sulfate.The optimal C∶N of strain P30,P12 and P4 was 20∶1,and that of P8 was 40∶1.The optimal P source for strain P12 was FePO 4 ,and Ca 3 （PO 4 ） 2 for P30,P8 and P4.[Conclusion]The P-solubilizing ability of PSBs can be significantly affected under different culture conditions.The 4 strains of high efficiency PSB have preferable P-solubilizing ability,which can dissolve a variety of insoluble inorganic phosphates Therefore,it is expected to provide germplasm resources for the development of high-efficiency microbia phosphate fertilizers with a good application potential.

As phenolic acids accumulated in monocropping plantations, their allelopathic effects caused the soil’s fertility to decline and productivity to decrease. The effects of stand age and generational turnover of phenolic acids in soil remain unclear. Therefore, we conducted an experiment to examine the changes in phenolic acid content and accumulation characteristics in soils from Eucalyptus plantations in terms of planting years and generations. Soils were collected from three Eucalyptus plantations: a 6-year-old first-generation plantation (6a1g), 9-year-old first-generation plantation (9a1g) and 6-year-old second-generation plantation (6a2g). Seven phenolic acids were identified from different soil samples by high-performance liquid chromatography. In addition, exogenous phenolic acids were added to the soil samples to study the kinetics as well as the adsorption and desorption characteristics of soils. The total of seven phenolic compounds in 6a1g (38.451 μg g–1) was higher than that of the 9a1g and 6a2g soils, and the total of 6a2g (27.257 μg g–1) was higher than that of the 9a1g (15.536 μg g–1). In the tested soil, the p-hydroxybenzoic acid accounted for 51.6% (for 6a1g), 51.1% (for 9a1g) and 33.5% (for 6a2g) of the total amount of the seven phenolic acids, the p-hydroxybenzoic may have had a higher allelopathic capacity in these Eucalyptus plantation soils. Soil bulk density showed a strong positive correlation with vanillic and ferulic acids, and SOM also had an extremely positive correlation with p-hydroxybenzoic and coumalic acids. The findings demonstrated that the adsorption and desorption rates and amounts of each phenolic acid in the soil of 6a1g were higher than those in the soil of 9a2g and 6a2g using both a kinetic adsorption experiment and isothermal adsorption and desorption experiments. But among the three soils, 9a1g soil had the lowest adsorption rate, which resulted in the lowest accumulation capacity. It is noticed that the Pseudo-second-order kinetic model can be used to describe the kinetic adsorption better than the Pseudo-first-order kinetic model and the Elovich model, and the Freundlich model could fit the desorption isotherms better than the adsorption isotherms. However, more study of this phenomenon is essential to better understanding its mechanisms and how they function in order to address issues with soil degradation in future intergenerational Eucalyptus plantings.

通过分析6种林分密度和2种林分起源下1～7 a生巨尾桉(Eucalyptus grandis×E.urophylla)人工林的林分平均树高、胸径、单株材积和每hm2蓄积量的总生长量、平均生长量和连年生长量,探索一定密度范围内巨尾桉的最适林分密度和起源方式,揭示林分密度和起源对林木生长和生产力的交互影响特征,为提高巨尾桉人工林培养质量和可持续经营提供理论参考.结果表明:1)随着林龄的增加,平均树高、胸径和单株材积的增长幅度逐渐减小,而每hm2蓄积量增幅在造林后期有所提高,4 a时达到数量成熟;2)各林龄下,随着林分密度的增加,平均树高、胸径和单株材积总生长量减小,超过2 a时林分密度1050株/hm2的总生长量显著(P<0.05)高于其他林分密度,每hm2蓄积量则在1800株/hm2下显著高于其他林分密度;3)植苗林的生长和生产力显著高于萌芽林,1050和1650株/hm2适合植苗林的树高、胸径生长和单株材积积累,1800株/hm2适合萌芽林生长和生产量积累.低密度造林(1050株/hm2)有利于巨尾桉个体树高、胸径和材积积累,易于大径材培育;高密度造林(1800株/hm2)有利于获得最高的蓄积量,提高林分生产力.本地区巨尾桉人工林的最适轮伐年龄为4～6 a.

为探索适合格木(Erythrophleum fordii)人工林在幼龄阶段的种植密度,在不同林分密度(2 m×1 m、2 m×2 m、2 m×3 m、3 m×3 m)的6 a生格木人工林下设置标准样地,采用土壤质量评价和灰色关联度等方法,探究不同密度下格木幼林的土壤理化与林下植被特征.结果表明,密度2 m×3 m下的林木胸径、树高最优,较最低水平高16.7％、27.9％;土壤总孔隙度最大,全N、硝态N、铵态N含量最高,灌木草本多样性最高.相关性分析表明土壤化学性质对灌木草本的多样性影响最大.不同林分密度下格木幼林土壤理化性质及林下植物多样性有显著差异,因此,选择合适的林分密度对人工林土壤肥力的可持续利用及林分的经营培育至关重要.

以1株来源于广西南宁树木园望天树(Parashorea chinensis Wang Hsie.)根际土壤的高效解无机磷细菌P4[洋葱伯克霍尔德菌(Burkholderia cepacia)]为材料,研究了解磷细菌P4在培养168 h内解磷能力和菌液pH的动态变化情况,比较了菌株在不同温度、pH、碳源、氮源、碳氮比(C/N)和NaCl浓度条件下的解磷能力,以期为解磷微生物在微生物菌肥生产上的开发和应用提供理论依据.结果表明,在培养168 h内,菌株P4培养液中有效磷含量呈先升高后降低的趋势,pH则呈先降低后升高的趋势,在培养120 h时菌液中有效磷含量最高,为552.87 mg/L,此时菌液pH最低;相关性分析表明,菌株P4溶磷量与培养液pH间存在极显著的负相关;菌株P4在培养温度为30℃、pH为6.5、碳源为乳糖、氮源为草酸铵、C/N为20∶1、NaCl浓度为0.5%时解无机磷效果最好且生长状况良好,在后续微生物菌肥研制中具有较大潜力.

Parashorea chinensis is an endemic tree species in China and an endangered species of the Dipterocarpaceae family. This study contributes to the understanding of soil fertility management during the relocation and conservation of P. chinensis and the restoration of its natural communities by doing an ecological chemometric investigation of the factors limiting soil nutrients in P. chinensis plantations. To investigate the variation in rhizosphere and non-rhizosphere soil nutrients, microbial biomass, and extracellular enzyme activities, we chose pure plantation stands of 6 ages in the subtropics and calculated stoichiometric ratios. The results show that (1) soil pH is strongly acidic (pH < 4.6) and is less influenced by the stand age, and the soil carbon (C), nitrogen (N), and phosphorus (P) content limit soil microorganisms at all stand ages; (2) the availability of soil N, P, and K elements is an essential factor driving P limitation in the growth of P. chinensis and its soil microbes; (3) stand age has a significant effect on the soil C/N, C/P, N/P, C/K, N/K, and P/K, the stoichiometry of microbial biomass C, N, and P, and the stoichiometry of C, N, and P acquisition enzyme activity. Soil microbial biomass C, N, and P stoichiometry are more sensitive indicators of nutrient limitations than the stoichiometry of enzyme activity and nutrient content; and (4) there was a significant correlation between microbial biomass C, N, and P stoichiometry and soil C/P and N/P, as well as a highly significant (p < 0.01) correlation between the stoichiometry of the enzyme activity and Vector L and Vector A. In conclusion, the plantations of P. chinensis in this study area were established on acidic phosphorus-poor soil, and the ecological stoichiometry of the soil reveals nutrient limitations and its variation with the stand age. P availability plays a key role in the growth of P. chinensis and in improving the rhizosphere microbial community. Therefore, soil effectiveness should be dynamically assessed during the cultivation and relocation conservation of P. chinensis, and a soluble P fertilizer should be supplemental over time in the trees’ root distribution area.

选择了4种生根剂,各取3种浓度,设置清水为对照,共13个处理,并测定了各处理下的苗高、地径、各器官的干物质积累量、叶片和根系形态及根系活力等指标.结果显示,ZF型生根剂能显著增加根系体积、XS型生根剂对根长、根尖数和根系活力的促进效果最佳;B-1型生根剂下苗木叶长、叶宽和叶面积值最高;ABT1号生根剂下的苗高、地径和干物质积累量最高.结果表明,4种生根剂的促生效果排序为:ABT1>XS>B-1>ZF>CK;添加生根剂能显著提高望天树苗木质量,不同类型和浓度的生根剂效果差异显著,且存在明显的交叉作用;ABT1号生根剂的综合评价得分最高,是促进望天树苗木生长和根系形态建成的最佳生根剂,稀释50倍是其最佳浓度;根系形态因子是望天树苗木综合质量的关键驱动因素,也是评价苗木质量的重要指标.

Taking 2-month-old seedlings of Tsoongiodendron odendron as experimental materials, the seedlings were treated with red and blue monochromatic LED(light emitting diode) lights and composite LED lights. The experiment lasted for 120 days with pure white light as control. The seedling height, ground diameter, biomass and the content of GA3, ABA, IAA, ZR were measured under different light quality. The findings indicated that the growth of seedling height and ground diameter was the highest under pure blue light treatment and the lowest under pure red light treatment, and the growth of seedling height and ground diameter increased significantly with the increase of blue light ratio in compound light; the dry matter accumulation of roots, stems and leaves and the total dry weight of seedlings reached the highest value under the pure blue light and the compound light with the highest proportion of blue light, and the lowest value under the compound light with the highest proportion of red light and pure red light; the content of GA3 and ZR were higher under pure blue light treatment, while the content of ABA was the highest under pure red light treatment. Adding the appropriate proportion of blue light to pure red light was conducive to reduce the synthesis of ABA, and promote the growth and development of seedlings; the best comprehensive quality of seedlings appeared under pure blue light treatment, and with the increase of the proportion of blue light, the quality of seedlings showed a better trend. In summary, pure blue light treatment had the best growth promoting effect, which could increase the dry matter accumulation, improve the seedling quality and growth rate; red light could promote the synthesis of ABA in leaves and inhibit the growth of seedlings. Although the H/D and SQI under pure blue light treatment were the highest, the appropriate proportion of red and blue light combined with irradiation of seedlings could better regulate the balance between endogenous hormones in seedlings, which was more conducive to improve the comprehensive quality of seedlings, shorten the cultivation period, and cultivate high-quality seedlings more efficiently.

Aluminized acidic soil can damage Eucalyptus roots and limit tree growth, hindering the productivity of Eucalyptus plantations. At present, the negative impacts of elevated aluminum (Al) on the cell morphology and cell wall properties of Eucalyptus root tip are still unclear. In order to investigate the responses of two different tolerant clones, Eucalyptus urophylla (G4) and Eucalyptus grandis × Eucalyptus urophylla (G9), to Al toxicity, seedling roots were treated hydroponically with an Al solution, and the polysaccharide content in the root tip cell wall and the characteristics of programmed cell death were studied. The results show that the distribution of Al was similar in both clones, although G9 was found to be more tolerant to Al toxicity than G4. The Al3+ uptake of pectin in root tip cell walls was significantly higher in G4 than in G9. The root tip in G4 was obviously damaged, enlarged, thickened, and shorter; the root crown cells were cracked and fluffy; and the cell elongation area was squeezed. The lower cell wall polysaccharide content and PME activity may result in fewer carboxylic groups in the root tip cell wall to serve as Al-binding sites, which may explain the stronger Al resistance of G9 than G4. The uptake of nitrogen and potassium in G4 was significantly reduced after aluminum application and was lower than in G9. Al-resistant Eucalyptus clones may have synergistic pleiotropic effects in resisting high aluminum–low phosphorus stress, and maintaining higher nitrogen and potassium levels in roots may be an important mechanism for effectively alleviating Al toxicity.

为探究桉树人工纯林转换为其他阔叶树种纯林及其混交林后土壤微量元素含量的变化,以桉树纯林、灰木莲纯林、香梓楠纯林、灰木莲×尾巨桉混交林(灰×桉混交林)和香梓楠×尾巨桉混交林(香×桉混交林)为研究对象,分析土壤中有效态微量元素、有机质含量和土壤pH值的差异及其相关性.结果表明:混交林土壤pH值较纯林大,但仅香×桉混交林2个土层的土壤pH值较桉树纯林显著增大(P<0.05),且均随土层深度的加深而增大.0～20 cm土层中,混交林土壤有机质含量较纯林显著高113.09％～331.35％(P<0.05);而20～40 cm土层中,灰×桉和香×桉混交林的土壤有机质含量显著低于灰木莲和香梓楠纯林(P<0.05),但较桉树纯林显著高65.08％、56.01％(P<0.05).混交林土壤中有效铁、锰、锌和硼含量总体显著高于纯林(P<0.05).然而,20～40 cm土层的灰×桉混交林有效硼含量较灰木莲纯林显著低45.00％(P<0.05),但较桉树纯林高286.29％.土壤有效铜含量在0～20 cm土层中,表现为香梓楠纯林和灰木莲纯林分别较其混交林显著高149.76％、187.22％(P<0.05),而在20～40 cm土层中,桉树纯林的土壤有效铜含量最低,分别较灰木莲纯林、香梓楠纯林、灰×桉混交林、香×桉混交林显著低82.99％、54.27％、85.49％、61.83％(P<0.05).除香×桉混交林外,其他林分随土壤pH值的增大,土壤有机质和微量元素含量降低.土壤有机质含量与有效铁、锰、锌和硼的含量呈显著正相关关系(P<0.05),但与有效铜含量则为负相关关系;土壤有效铁、锰、锌和硼之间存在密切的正相关关系.混交林显著提高了土壤有机质和有效态铁、锰、锌和硼等微量元素的含量,提高了林地的土壤肥力.

AimsThis study aimed to study the effects of two young mixed plantations of Parashorea chinensis (an endangered native tree species) on the functional characteristics and carbon source utilization of the soil microbial community, so as to select the suitable afforestation mode of P. chinensis and maintain sustainable management of forests by changing pure Eucalyptus plantation into mixed plantations with heterogeneous structure. MethodsThe functional diversity of soil microbes and their utilization of six carbon sources in mixed and pure plantations of P. chinensis were compared and analyzed using the Biolog-ECO technique, and a correlation analysis was further carried out incorporating soil physicochemical properties.Important findings (1) The Shannon-Wiener, Simpson and McIntosh diversity index of the microbe community in mixed plantations of P. chinensis and E. grandis × E. urophylla were the highest, and their soil microbial functional diversity was significantly higher than that of pure plantations.(2) The carbon source utilization and microbial

为探究杉木纯林引入观光木转化为异龄复层林后土壤理化性质和土壤养分含量的变化特征,以及驱动土壤肥力变化的主要影响因子,以观光木纯林、杉木纯林和杉木林下套种观光木形成的杉木×观光木异龄复层林为对象,测定了3种林型下林分生长、林地土壤理化性质和养分含量及其化学计量比等指标,分析杉木×观光木异龄复层林林分结构、林木生长和土壤肥力质量特点.结果 表明:1)异龄复层林中观光木和杉木的树高、胸径分别为5.3m、2.52 cm和18.56 m、20.19 cm,显著高于纯林;2)3种林型间土壤物理性质差异显著.异龄复层林相比较纯林,土壤密度降低4.84％～11.94％,土壤孔隙度分别增加10.29％～22.27％,持水量增加8.62％～34.54％,有效改善了土壤孔隙结构和持水状况.3)各层土壤有机质、全N、全P、全K及速效养分与观光木、杉木纯林均差异显著,土壤养分含量随着土层加深而递减.各养分含量分别比杉木、观光木纯林高出7.87％～41.31％、14.32％～53.57％,各层土壤有机质和养分含量由大到小呈现为:异龄复层林、杉木纯林、观光木纯林.4)异龄复层林中C∶N、C∶P平均值分别为16.62、61.46,均低于杉木和观光木纯林,促进了土壤中N、P的有效释放.因此,在异龄复层林中观光木获得更适宜其生长的良好的遮阴环境,2个树种间形成生态位互补,提高了空间和自然资源的利用率,促进了树木生长.异龄复层林能显著提高土壤有机碳和养分含量,且明显高于纯林,在杉木林中套种观光木能加快土壤微生物的转化和矿化作用.