Intercropping is widely promoted for sustainable agroecosystems, but its effects on soil aggregate stability, aggregate-associated soil organic carbon (SOC) and the underlying microbial mechanisms remain unclear in Camellia oleifera plantations. This study investigated the impact of intercropping with legume (Trifolium repens, CT) or grass (Lolium perenne, CL) on soil aggregates and microbial communities across two phenological stages. Compared with monoculture (CK), CT and CL markedly increased the mass proportion of large macroaggregate (> 2 mm) by 33.48% and 17.11% during the growing stage, with attenuated increments during the wilting stage. Correspondingly, soil aggregate stability (geometric mean diameter, GMD) was improved by 60.22% and 48.66% in the growing stage, and 25.60% and 19.36% in the wilting stage, respectively. CT persistently increased SOC in large macroaggregate by 27.93%-36.45%, which was higher than that in CL (22.44%-26.44%). High-throughput sequencing revealed that intercropping enhanced bacterial and fungal richness by 27.5%-52.4% and 101.0%-126.6% (p < 0.05), particularly during the wilting stage. Concurrently, intercropping strengthened microbial network complexity and stability, especially for fungi, as evidenced by higher average clustering coefficients (176.51%-386.04%) and negative-to-positive cohesion ratios (5.66%-23.48%). Intercropping shifted bacterial assembly toward stochastic processes while fungal assembly became more deterministic. Pathway modeling demonstrated that assembly-induced shifts in microbial diversity and interactions enhanced aggregate-mediated SOC protection in intercropping systems (GoF = 0.6857), with fungal community contributing more than bacterial community. These findings indicate that legume intercropping better improves soil structure and aggregate-associated SOC by reshaping microbial assembly patterns and enhancing network stability. Notably, appropriate management during the wilting stage is critical for optimizing microbial-mediated aggregate stability and SOC retention in C. oleifera agroecosystems, particularly under legume intercropping.

ABSTRACT Optimized fertilization involving reduced mineral N input and organic substitution can alter resource stoichiometry, microbial carbon use efficiency (CUE) and nitrogen use efficiency (NUE). However, how fertilization‐induced resource imbalance reshapes microbial community to regulate CUE and NUE remains unclear. We conducted a field experiment in a Camellia oleifera plantation under conventional mineral nitrogen fertilizer (CK), organic manure (OM), and reduced mineral nitrogen combined with manure (RNM). Microbial CUE and NUE (via stoichiometric modeling), community structures and functions were determined at 30 and 120 days after fertilization. At 30 days, RNM and OM significantly increased NUE and alleviated resource limitations compared with CK. OM improved most microbial network properties relative to CK and RNM ( p < 0.05). At 120 days, C‐limitation disappeared while nutrient‐limitation persisted across all treatments. RNM and OM increased NUE by 1.13‐ and 4.26‐fold but decreased CUE by 7.5% and 61.3%, respectively. RNM showed the most balanced CUE‐NUE trade‐off. Notably, OM exhibited significantly lower microbial network metrics than CK and RNM except for the number of nodes ( p < 0.05), revealing a time‐dependent reversal effect. The laccase‐related microbial metabolic function was significantly associated with resource use efficiency ( p < 0.05), with a stronger association with NUE than CUE. Linear mixed‐effects models identified microbial network properties and resource limitation status were dominant predictors governing the CUE‐NUE balance ( > 0.3). Model explanatory power was substantially improved after fertilization type was included ( > 0.9). Our study provides novel evidence that fertilization‐induced stoichiometric imbalance reshapes microbial networks and further modulates microbial CUE and NUE. These findings highlight that microbial network attributes should be integrated into fertilization optimization strategies to balance soil carbon sequestration and nutrient retention.

Phosphorus (P) is an essential limiting nutrient for plant growth in the red soils of southern China. Understanding how intercropping affects soil P fractions and availability is crucial for maintaining P demand in Camellia oleifera agroforestry systems. The effects of intercropping on the soil P fractions, availability and phoD-harbouring bacteria community were investigated in three plantation types: C. oleifera monoculture (CK), C. oleifera intercropped with Capsicum annuum L (CC), and C. oleifera intercropped with Arachis hypogaea L (CA). Intercropping significantly changed P fractions and availability. CA increased the NaHCO3-Po content but decreased the NaOH-Po content, while CC enhanced the NaOH-Pi content compared to CK. Additionally, CA increased the RAP content by 34.3

Lead (Pb) contamination threaten soil ecosystems, and the increased risk of flooding due to climate change may influence soil functions and metal bioavailability. However, the response of rhizosphere soil microbial communities to these combined stresses remains unclear. Here, fast-growing willow (Salix × jiangsuensis 'J172') was planted in soils with Pb contamination (control, 400 and 800 mg · kg-1) under non-flooded (NF) and flooded (IF: intermittent flooding and CF: continuous flooding) conditions for 60 d. At Pb800 contamination, IF and CF markedly decreased the soil available Pb by 17.7 % and 14.1 % (p < 0.05), respectively, compared to NF condition. Flooding (CF and IF) conditions increased bacterial phylogenetic diversity compared to NF, with IF exhibiting greater impact (10.6 %, p < 0.05). For assembly process, the bacterial community under CF condition exhibited a shift towards a more deterministic process compared to NF, although stochastic mechanisms were still dominant (normalized stochasticity ratio >0.5). Increased abundance of Pb tolerance genes and sulfate-reduction function under CF conditions promoted a decrease in soil Pb availability (R2 > 0.5, p < 0.05). Compared to NF, the bacterial functional redundancy index, which characterizes the stability of ecological functions, was reduced by 7.1-25.9 % under CF condition, regardless of Pb contaminations, while IF increased this index with Pb800. The findings provide valuable insight into the mechanisms underlying the response of soil bacterial communities for the studied Salix species to combined stresses of flooding and Pb, and enhance the comprehension of rhizosphere micro-ecological processes in remediation woody plants under complex multi-stress exposure scenarios.

INTRODUCTION:Soil nutrient supply drives the ecological functions of soil micro-food webs through bottom-up and top-down mechanisms in degraded agroecosystems. Nutrient limitation responds sensitively to variations in degraded agroecosystems through restoration practices, such as legume intercropping. OBJECTIVES:This study examined the effects of legume intercropping on trophic cascade dynamics through resource supply in degraded purple soil ecosystems. METHODS:A field experiment was conducted with three plantation types: Camellia oleifera monoculture (CK), C. oleifera-Arachis hypogaea (peanut) intercropping (CP), and C. oleifera-Senna tora intercropping (CS). Using soil nutrient limitation as a premise, modified by legume intercropping, we assessed the biodiversity of soil biotic taxa, analysed their community composition, and applied partial least squares path modelling (PLS-PM) to link trophic cascade with ecological functions. RESULTS:Legume intercropping altered the abundance of biotic taxa, leading to changes in biotic diversity and microbial life strategies. The PLS-PM results indicated that legume intercropping enhanced bacterial diversity by aggravating soil P limitation, which subsequently increased protist consumer diversity and omnivore-predator nematode abundance through a bottom-up effect. Omnivore-predator nematodes and protist consumers indirectly influenced soil P metabolism, down-regulated through bacteria in the top-down effect. We observed high consistency between the untargeted metabolomic analysis and soil nutrient limitations. These findings indicate that soil micro-food web structure and function responded sensitively to legume intercropping in degraded ecosystems. CONCLUSION:The results highlight the role of soil nutrient limitation in shaping micro-food webs and suggest that soil P limitation controls the down-regulation of soil P-related ecological functions through bottom-up and top-down effects.

Soil and water loss represent a significant environmental challenge in purple soil cropland in China. However, the quantity and mechanism of nutrient loss from purple soil remain unclear. To understand water and soil conservation and address nitrogen (N) and phosphorus (P) mitigation in Camellia oleifera forest stands on purple soil slope farmland, this study aimed to explore the resistance control effect of forest stands on N and P loss in such agricultural landscapes. In the study, a runoff plot experiment was conducted in purple soil slope farmland. The experiment included three distinct treatments: intercropping of oil tea (Camellia oleifera) and ryegrass (Lolium perenne L.), Camellia oleifera monoculture, and barren land served as the control treatment (CK). Water samples were collected and analyzed from the soil surface runoff and the middle soil layer at a depth of 20 cm (interflow) in three treatment plots under natural rainfall conditions in 2023. Various nutrient components, including total nitrogen (TN), dissolved nitrogen (DN), nitrate nitrogen (NO3−-N), ammonium nitrogen (NH4+-N), particulate nitrogen (PN), total phosphorus (TP), dissolved phosphorus (DP), phosphate (PO4+-P), and particulate phosphorus (PP), were measured in the water samples. The results indicated that intercropping effectively mitigated the loss of various forms of N and P in both surface runoff and interflow within purple soil slope farmland. Compared to the CK, the ryegrass intercropping reduced TN and TP loss by 29.3%–37.3% and 25.7%–38.9%, respectively. The ryegrass intercropping led to a decrease in the average total loss of TN, DN, NO3—N, and NH4+-N by 63.0, 24.3, 4.5, and 6.8 g/ha, corresponding to reductions of 33.3%, 47.6%, 58.3%, and 49.1%, respectively, compared to the CK. The average total loss of TP, DP, and PP decreased by 4.4, 1.8, and 1.4 g/hm2 in the intercropping, reflecting reductions of 32.3%, 31.3%, and 31.1%, respectively. The most significant proportion was observed in PN and PP within the runoff water solution, accounting for 53.3%–74.8% and 56.9%–61.0% of the TN and TP, respectively. These findings establish a foundation for purple soil and water conservation. The research provides valuable insights for land management and policymakers in developing erosion prevention and control programs for sloping cultivated land with Camellia oleifera forests in purple soils. Additionally, it offers guidance for soil and water conservation and prevention of surface source pollution in purple soil regions.

Intercropping system influences the endophytic microbial abundance, hormone balance, nutrient metabolism and yield, but the molecular mechanism of yield advantage in Camellia oleifera intercropping with peanut is not clear. In this study, the C. oleifera monoculture (CK) and C. oleifera-peanut intercropping (CP) treatments in purple soil were conducted, and the physicochemical properties, gene expressions, signal pathways and crucial microbial abundances were investigated to reveal the molecular mechanism of the yield advantage of inter- cropped C. oleifera. The results showed that the intercropping system increased in contents of pigment, carbohydrate, available nitrogen and phosphorus in leaf and root, as well as the abundances of Burkholderia, Ralstonia, Delftia, Pseudoalteromonas and Caulobacter, enhanced the relative expression levels of CoSPS, CoGBE, CoGlgP, CoGBSS/GlgA genes to promote sugar metabolism, decreased the relative expression levels of CoASA, CoTSB, CoPAI, CoTDC and CoCYP71A13 genes for inhibiting IAA biosynthesis and signal transduction, as well as microbial diversity, Fusarium, Albifimbria and Coniosporium abundances in root, ultimately improved the fruit yield of C. oleifera. These findings indicate that intercropping system improves the fruit yield by enhancing the nutrient metabolism capability and crucial microbial abundances in root of C. oleifera in purple soil.

The general aim of the study is to provide insight into the importance of functioning maintenance of forest ecosystems. Specifically, the aim of the study is to assess the response of soil protist diversity, composition and co-occurrence network to varying degree of decomposition of fallen wood when compared to conventional soil. A total of 24 samples of soil and fallen wood were collected from subtropical broad-leaved forests in China. Here we use a correlative approach to link the community of soil protists with fallen wood at different decomposition stage and compare with fallen-wood-free soil. The indicators of protists community were assessed using DNA metabarcoding of the 18S rRNA (Illumina sequencing). The biodiversity of soil protists tended to increase as decomposition advanced and pronounced difference was found between severe and moderate decomposition stages (P < 0.05). The decomposition of fallen wood had a significant effect on the composition of the soil protist community (Adonis: R2 = 0.24, P < 0.01), and enhanced the complexity and stability of the co-occurrence network of soil protists. Soil protists exhibited a stronger association with fallen wood (11 significant linkages), compared to soil (7 significant linkages). Fallen wood decomposition indirectly affected the soil protist community through multiple ways. Retention of fallen wood helps maintain the richness and interaction of soil protists. Future research directions should focus on specific mechanisms for how fallen wood decomposition affects protists. Our work may contribute to better guide forest management policies in China.

An understanding of how irrigation regimes affect autotrophic microorganisms is essential, as this has direct implications for the soil organic carbon (SOC) content, rice yield and the sustainable agricultural practices. Here, the effects of three irrigation regimes on autotrophic microorganisms, soil active organic carbon fractions, and rice yield were explored. The irrigation regimes were: 1) rainfed (RF), 2) midseason drying (MD), and 3) continuous flooding (CF). The SOC, microbial biomass carbon (MBC), MBC/SOC ratio, dissolved organic carbon (DOC), DOC/SOC ratio, the cbbL (the cbbL gene encodes the large subunit of ribulose-1, 5-bisphosphate carboxylase) bacterial alpha diversity and community composition, and rice yield were assessed under each regime. The highest MBC content (646 mg kg-1 in the early season and 1007 mg kg-1 in the late season) and MBC/SOC ratio (3% in the early season and 5% in the late season) were observed under the RF regime. The soil DOC content and DOC/SOC ratio were the highest in the MD regime, followed by the CF regime. The lowest values were observed under the RF regime, with greater differences observed in the late season. Soil cbbL bacterial alpha diversity was the highest in the MD regime and the lowest in the CF regime. The irrigation regimes altered the composition of the cbbL microbial community, with Burkholderiales and Corynebacteriales exhibiting the highest relative abundances in the MD regime. In the late season, the rice yield in the MD regime was 53% and 14% greater than the RF and CF regimes, respectively. A partial-least-squares path model showed that the optimal regime (MD regime) increased the alpha diversity of the soil cbbL bacteria and the relative abundances of several probiotic microorganisms. This, in turn, increased soil DOC content and its contribution to SOC, eventually increasing the rice yield. These findings clarified the effects of different water management strategies on autotrophic microorganisms, organic carbon, and rice yield, providing guidance for implementing suitable water management practices to enhance soil fertility and rice yield.

As a major source of air pollution, particulate matter (PM) and associated toxic trace elements pose potentially serious threats to human health and environmental safety. As is known that plants can reduce air PM pollution. However, the relationship between PM of different sizes and toxic trace elements in foliar PM is still unclear. This study was performed to explore the association between PM of different sizes (PM2.5, PM10, PM>10) and toxic trace elements (As, Al, Cu, Zn, Cd, Fe, Pb) as well as the correlation among toxic trace elements of six roadside plant species (Cinnamomum camphora, Osmanthus fragrans, Magnolia grandiflora, Podocarpus macrophyllus, Loropetalum chinense var. rubrum and Pittosporum tobira) in Changsha, Hunan Province, China. Results showed that P. macrophyllus had the highest ability to retain PM, and C. camphora excelled in retaining PM2.5. The combination of P. macrophyllus and C. camphora was highly recommended to be planted in the subtropical city to effectively reduce PM. The toxic trace elements accumulated in foliar PM varied with plant species and PM size. Two-way ANOVA showed that most of the toxic trace elements were significantly influenced by plant species, PM size, and their interactions (P < 0.05). Additionally, linear regression and correlation analyses further demonstrated the homology of most toxic trace elements in foliar PM, i.e., confirming plants as predictors of PM sources as well as environmental monitoring. These findings contribute to urban air pollution control and landscape configuration optimization.

Agroforestry is a commonly applied restoration practice in nutrient-poor or degraded soils, and knowledge of soil nutrient limitations is critical for its successful implementation. Ecoenzymatic stoichiometric theory (EEST) models have been proposed as easy and fast methods to estimate soil nutrient limitations in terrestrial ecosystems; however, a comprehensive application of different models in agricultural studies is still lacking. To bridge these gaps, in this study, we analysed the nutrient limitation of three plantation types, Camellia oleifera monoculture (CK), C. oleifera–Arachis hypogaea (peanut) intercropping (CP), and C. oleifera–Senna tora intercropping (CS), within a fully controlled C. oleifera agroforestry system in nutrient-poor purple soils. We compared the estimates of the nutritional limitations of each plantation type using three different EEST models: vector, vector-threshold element ratio (V-T), and threshold. Estimates of nutrient limitation calculated using the threshold model recapitulated those calculated using the other models. Further, N and P limitations existed in all three plantation types, C limitation was not detected in any plantation type, and the CP plantation type alleviated N limitation and aggravated P limitation. These results were consistent with the actual nutrient characteristics of the purple soil, indicating that the microbial metabolic limitation profile estimated by the EEST model was reliable. The results of this study suggest that EEST models are valuable tools for estimating soil nutrient limitation in the context of agricultural ecosystem restoration, such as in agroforestry.

Forests undergo a long-term development process from young to mature stages, yet the variations in soil nutrients, enzyme activities, microbial diversity, and community composition related to forest ages are still unclear. In this study, the characteristics of soil bacterial and fungal communities with their corresponding soil environmental factors in the young, middle, and mature stages (7, 15, and 25-year-old) of Chinese fir plantations (CFP) in the subtropical region of China were investigated in 2021. Results showed that the alpha diversity indices (Chao1 and Shannon) of soil bacteria and fungi were higher in 15 and 25-year-old stands than in 7-year-old stand of CFP, while the soil pH, soil water content, soil organic carbon, total nitrogen, total phosphorus, sucrase, urease, acid phosphatase, catalase, and microbial biomass carbon, nitrogen, and phosphorus showed higher in 7-year-old stand than other two stands of CFP. The nonmetric multidimensional scaling analysis revealed that the soil microbial species composition was significantly different in three stand ages of CFP. The redundancy and canonical correspondence analysis indicated that the soil urease and microbial biomass nitrogen were the main factors affecting soil bacterial and fungal species composition. Our findings suggested that soil microbial diversity and community structure were inconsistent with changes in soil nutrients and enzyme activities during CFP development, and enhancing stand nurturing and soil nutrient accumulation in the mid-development stage were beneficial to the sustainable management of CFP.

Ecological stoichiometry plays important roles in understanding the nutrient constraints on tree growth and development, as well in maintaining ecosystem services in forests, yet the characteristics of carbon:nitrogen:phosphorous (C:N:P) stoichiometry in forests under karst environment have not been sufficiently evaluated. In this study, concentration, distribution, stocks of Nitrogen (N) and Phosphorous (P), and ecological stoichiometry were studied in three common forest types: Masson pine natural forests (MPNF), Masson pine plantation forests (MPPF), and Slash pine plantation forests (SPPF) in a karst region of southwestern China. Results showed that N concentrations were higher in overstory than in understory and litter in the studied forests. However, P concentration was relatively low in overstory component of the forested ecosystems. Meanwhile, the N and P concentrations were higher in SPPF in the stem and litter, while these contents were higher in MPPF and MPNP in the overstory and understory. The N and P stocks ranged from 5.7–6.2 t ha−1, and 0.5–0.6 t ha−1 in the examined forests. The ecological stoichiometry of C:N:P in the three forest types was similar in litter (46–49:2:1), and relatively steady in soil (250–320:13–16:1) and tree leaf (100–200:14–20:1). Soil P status was the primary limiting factor in affecting tree growth in MPPF and SPPF (N:P ratio > 16), while both N and P conditions were the main restrictive factors in MPNP (N:P ratio = 15) in the study area. Our study provides scientific references and useful datasets of C:N:P stoichiometry for sustainable management of forest ecosystems in karst regions.

Fallen wood has a pivotal role in the forest ecosystem and acts as an important intermediary for material cycling and energy flow between vegetation and soil. A keystone of the forest ecosystem is the soil fungal community which performs a crucial role in regulating the internal functions of the system. Nonetheless, the characteristics of soil fungal community diversity and the process of community assembly beneath fallen wood remain unclear. Here We investigated two subtropical forests at different elevations, and selected three fallen wood of different decay classes and a control soil without fallen wood in each stand. The soil underneath the fallen wood was collected for analysis to explore the effects of decay on soil fungal diversity and community assembly processes. The 18S rRNA amplicon sequencing was used to determine fungal diversity and calculate normalized stochasticity ratios (NST), whilst the underlying soil ecological factors were measured to predict the possible drivers of fungal diversity along with the driving mechanisms. The results revealed that elevation and fallen wood decay had a significant interactive effect on soil fungal alpha diversity as well as beta diversity. Outcomes of tNST (taxonomic Normalized Stochasticity Ratio) suggested that fallen wood decay at high-elevation made stochastic processes progressively more important in the assembly of soil fungal communities, while the opposite occurred at low-elevation, yet the results calculated by the pNST (Phylogenetic Normalized Stochasticity) method tended to indicate a predominance of stochastic processes in both two elevations. Fungal diversity was strongly positively correlated with NST values, but soil ecological factors were only strongly associated with NST values. The partial least squares path model (PLS-PM) further indicated that elevation and fallen wood decay did not directly regulate changes in fungal community diversity, but indirectly controlled fungal community assembly processes by affecting soil ecological factors, anon varied fungal diversity as well as community structure. This work will generate fresh insight into the patterns of soil fungal diversity and community assembly processes in forest ecosystems.

Soil labile organic carbon fractions (SLOCFs) mainly include microbial biomass carbon (MBC), dissolved organic carbon (DOC), easily oxidized organic carbon (EOC) and light fraction organic carbon (LFOC). The link between bedrock exposure rates with SLOCFs and the carbon pool management index under karst rocky desertification has not been well understood. We selected the bedrock exposure rate and vegetation coverage of 30–50% (light bedrock exposure, LBE), 50–70% (moderate bedrock exposure, MBE) and >70% (intense bedrock exposure, IBE) as the experimental sample plots according to the classification standard of karst rocky desertification, and then selected a sample plot of 0–30% (secondary forest, SF) as the control. This study compared the concentrations and stocks of soil organic carbon (SOC) and SLOCFs and analyzed the relevant carbon pool management index on karst landforms at Anshun, S.W. China. The aims were to determine the relationship between bedrock exposure rates and SLOCFs and to identify the most limiting factors for SLOCFs in karst rocky desertification areas. We found that (1) the concentrations and stocks of SLOCFs declined with increasing soil depth. SOC, DOC and MBC showed IBE > LBE > MBE > SF; LFOC decreased with increasing bedrock exposure rate, and EOC did not show obvious regularity. (2) The carbon pool management index and sensitivity index had significant differences under different bedrock exposure rates. Redundancy analysis and linear regression showed that the increase in bedrock exposure rate had a great impact on MBC, DOC, EOC and SOC. In conclusion, the increase of bedrock exposure rate has no side impact on the DOC, EOC and MBC of the soil, but side effects are exhibited by LFOC. Secondary forest improves the integrity of karst landscapes, and does not change the soil properties as well as the concentrations and stocks of SLOCFs in karst rocky desertification areas.

[目的]探讨不同间作模式对油茶幼苗氮素的影响特征,为增加油茶农林复合生态系统经济效益,促进生态系统多样性提供科学依据,以提高后期油茶果实产量.[方法]以2年生油茶幼苗为研究对象,采用15N示踪法,于N0(0 mg/kg)、N1(50 mg/kg)和N2(250 mg/kg)3种氮素水平下,分别设置油茶单作(D)、油茶-辣椒(L)和油茶-花生间作(H)3种模式,对油茶生物量及土壤中氮素的吸收、利用和分配进行探究.[结果]油茶生物量在N0、N1、N2下分别表现为H>L>D、L>H>D和L>D>H;不同器官在不同模式下氮素贡献率(Ndff)差异性显著(P<0.05),前后期茎Ndff均为D>L>H,叶Ndff前期最高和最低分别为N2(0.39％)和N1(0.11％)下H;后期为N1(0.42％)和N0(0.26％)下L;各器官氮素分配率前期均为根>叶>茎,后期叶、茎、根最高分别为N1下H(50.55％)、N2下H(42.50％)和N0下L(50.59％);氮素利用率随氮素水平的增加而降低,在不同间作模式下分配率表现为H(20.33％)>L(16.23％)>D(8.89％).[结论]1年生经济作物辣椒和花生在适度氮素水平(N1)与油茶幼苗间作对氮素吸收、利用和分配以及生物量有一定的促进作用,高氮素(N2)下间作有一定的抑制作用.因此,在农林复合生态系统中应采用不同生长周期的1年生经济作物与油茶进行短周期、不同作物轮番间作的模式可能具有更好的效果.

The authors wish to make the following corrections to this paper [...]

Abstract As a vital component of the forest ecosystem, dead wood plays an important role in forest regeneration, species variety, water conservation, soil erosion avoidance, and the carbon cycle. At the moment, dead wood research is mostly concerned with the storage of dead wood in forests and the change of nutritional components throughout the decomposition process. There have been few investigations on the changes in soil active organic carbon components and bacterial community structure during the breakdown of dead wood. To investigate the impact of dead wood on soil active organic carbon components and the structure of microbial communities. we selected the soil under three different decay grades of Castanopsis eyrei dead wood and the forest soil without dead wood as the control. The basic physical and chemical indexes of soil, the composition of soil active organic carbon and the structure of microbial community were measured. Compared with the control group, dead wood mulching significantly increased the content of soil organic carbon and total nitrogen (P < 0.05), and dead wood significantly affected the content of soil active organic carbon (P < 0.05). The easily oxidized organic carbon, microbial biomass carbon and organic carbon under the severe decay dead wood were significantly higher than those in the control (P < 0.05), and the content of activated carbon increased with the increase of decay grade. The relative abundance of Actinobacteria, Chloroflexi, WPS-2, Patescibacteria and Bacteroidetes increased with the increase of decay grade of dead wood, and the relative abundance of soil bacteria under dead wood was higher than that of the control. Through the redundancy analysis of environmental factors and soil microbial community, we found soil total nitrogen and pH are the key factors driving microbial community. The distribution of soil bacterial community under light rotten dead wood is similar to that soil without dead wood, which is significantly different from that under moderate and severe rotten dead wood. The abundance of soil bacterial community and soil active organic carbon components are most affected by heavy rotten dead wood. Soil active organic carbon was significantly negatively correlated with Acidobacteria(P < 0.01), and positively correlated with Ktedonobacteria, Bacteroidia, Saccharimonadia and TK10(P < 0.05). The above research results show that dead wood has a great impact on soil physical and chemical properties and microbial community structure. Our study improves the impact of dead wood on soil activated carbon components and microbial community, and provides a theoretical basis for sustainable forest management.

[目的]研究道路绿化带不同植物PM2.5滞留量并比较不同配置模式PM2.5的滞留能力,为城市绿化树种的筛选和城市生态规划提供科学依据.[方法]选取长沙市韶山路道路绿化带13种常见道路绿化植物,通过微孔滤膜称重法等研究长沙市道路绿化带单位叶面积、单株、单位绿地面积滞留PM2.5能力,比较乔灌、灌木纯林、乔灌草、灌草、乔乔灌、乔木纯林配置模式下的滞尘能力,并在R 4.0.2软件中使用Ward.D方法按欧式距离对13种植物在单位叶面积滞留PM2.5能力、单株滞留PM2.5能力、单位绿地面积滞留PM2.5能力3个尺度综合进行层次聚类分析.[结果]不同植物单位叶面积PM2.5滞留量的变化范围为10.39～427.12 mg·m-2,沿阶草对PM2.5的滞留能力最强,罗汉松次之;在单株尺度上,滞留能力的变化范围较大为0.03～16000 mg·株-1,石楠和罗汉松对PM2.5的滞留能力最强,酢浆草PM2.5滞留量最低;从单位绿地面积植物对PM2.5的滞留能力来看,PM2.5滞留量的变化范围为10.00～500.00 mg·m-2,罗汉松对PM2.5的滞留能力最强,酢浆草和荷花玉兰滞留PM2.5能力较差(10～40 mg·m-2);不同配置模式下,植物滞留PM2.5能力依次为:乔灌>灌木纯林>乔灌草>灌草>乔乔灌>乔木纯林;聚类分析发现石楠、罗汉松滞留PM2.5能力较强,其中罗汉松滞留PM2.5的综合能力最强.[结论]道路绿化带同一植物不同尺度、不同植物、不同配置模式滞留PM2.5能力存在差异,优化植物配置可以增强城市道路绿化带的滞尘效应.

利用2017-2018年长沙市空气质量监测数据,分析了长沙市大气颗粒物PM2.5和PM10的时空分布特征.结果表明:长沙市大气颗粒物PM2.5和PM10均表现为冬季>秋季>春季>夏季,冬季浓度最高,PM2.5和PM10分别为62.87和89.22μg·m-3;空间变化特征:PM2.5浓度为长沙城区>长沙县>宁乡县>望城区>浏阳市,PM10浓度为长沙城区>宁乡县>长沙县>望城区>浏阳市;颗粒污染物PM2.5与PM10浓度有极显著的线性相关性,r=0.853,P=0.000(P<0.01);降水对大气颗粒物有显著消减作用,使PM2.5、PM10的浓度分别下降了17.93％ 和27.67％.通过调整能源结构、提倡绿色出行、增加绿量、人工降水等可有效控制长沙市大气颗粒物污染.