Rhizosphere is the interface between roots and soils in forests,within which the micro-ecosystem is formed by the interaction of root metabolites,organisms and edaphic physicochemical factors.Due to root activities,rhizosphere has specific microbial community and function,with complex effects on forest growth and development and soil ecological processes.Development of high-throughput sequencing technology has advanced our understan-ding on the mechanism of rhizosphere microorganisms in plant growth promotion and stress resistance beyond the limitation of culture difficulties.Microbial community,function and interactions with forests were progressed well,but there are still gaps in the mechanism of rhizosphere microbial assembly regulated by plant metabolism and the development of synthetic microbial communities.We first summarized the functions of rhizosphere microorganisms in plant growth and stress resistance of forests,and addressed the application of synthetic microbial communities.Then,we discussed the effects of biotic and abiotic factors on rhizosphere microorganisms.Finally,we put forward the research on omics and community of forest rhizosphere microorganisms under the background of global climate changes,aiming to provide a theoretical support for the application of microbial resources in forest health mainte-nance and sustainable development of forestry.

Forests are highly productive ecosystems that contribute to biogeochemical cycles of carbon and nitrogen, through which it regulates climate and global change. Forests are also spatially highly heterogeneous ecosystems that comprise a multitude of microbial-mediated reactive interfaces. These are mainly the root–soil interface, litter–soil interface, root–root interface, and plant–atmosphere interface. Each of these interfaces has its own unique characteristics, e.g., specific drivers that affect the microbial abundance, nutrient availability, microbial community, and the dominance of certain microbial taxa. Here, we review the microbial-mediated reactive interfaces in forests, focusing on interrelation and dynamics of fungi and bacteria on a broad temporal scale with ecosystem processes ranging from short-term events (e.g., seasonal changes) to long-term stand development suffering a global climate change (e.g., global warming or nitrogen deposition). We argue that in-depth knowledge of forest microbiology can only be obtained by exploring the complex forest microbiome and its ecosystem functions. Underpinning the basis for individual forest variation would ultimately facilitate the formulation of microbiome-based strategies in the future.

连栽导致土壤退化是制约杉木初级生产力实现的重要障碍因素，而土壤对病原菌的抑制能力决定着植物能否有效抵御病原菌侵害，是人工林土壤地力状况的重要表现。以一代、二代、三代杉木人工林和天然次生林为对象，采用平板隔空、直接对峙的方法，分析了不同代际杉木林土壤细菌群落对尖孢镰刀菌和立枯丝核菌的抑制能力。进一步利用高通量测序技术，研究了杉木林土壤细菌群落影响土壤抑病能力的生态过程。结果表明：土壤磷元素随连栽呈显著积累趋势，而土壤pH和有机质（SOM）等含量随连栽代数的增加而下降，但这些下降指标在三代杉木林与天然林土壤间无显著差异。而杉木连栽导致土壤对病原菌的抑制能力逐代降低，天然林土壤较杉木人工林对病原菌具有显著的高抑制能力。同时杉木连栽显著改变了土壤细菌群落组成，而对群落整体α-多样性影响较小，说明土壤中一些关键类群对杉木连栽响应的敏感性高于整体细菌群落的变化。进一步利用随机森林模型预测与回归分析，揭示了杉木连栽引起的土壤一些关键细菌类群丰度的降低是土壤抑病能力下降的重要原因，这些类群主要受土壤pH、SOM、TP等土壤理化因子的调控。由此，杉木长期连栽会引起土壤微环境失衡，致使土壤抑制病原菌能力下降，从而增加病原菌危害杉木林健康，不利于人工林生产力的提升和可持续经营。

Background and Aims Free living, non-symbiotic nitrogen-fixing bacteria (diazotrophs) that inhabit plant rhizosphere substantially contribute to nitrogen input in forest ecosystems. Different plant species provide heterogeneous habitats for rhizosphere diazotrophs by releasing root exudates containing potential resources for microbial utilization, but the ecological processes of diazotrophic community assembly and association with plant species are not fully understood. Methods We investigated the diazotrophic abundance (as assessed by real-time quantitative PCR), diversity, and composition of rhizosphere diazotrophic communities (based on nifH -amplicon sequencing) for four non-leguminous broadleaf tree species and three conifer tree species in a forest ecosystem. Results The analysis revealed that the rhizosphere of four broadleaf tree species harbored higher diazotrophic abundance and diversity by 239% and 50.0% respectively, as compared to the conifer tree species. Further, phylogenetic distance between the seven tree species was positively correlated (Mantel r = 0.482, P < 0.001) with the dissimilarity of diazotrophic community assembly, thus determining rhizosphere potential nitrogen fixation indicated by nifH gene abundance. Of the top 20 genera (ranked by percentage increase in Mean Squared Error) that contribute to potential nitrogen fixation, 11 rare genera were at low relative abundances (< 1%). Network analysis further showed the central position of rare genera in the diazotrophic co-occurrence network of four broadleaf tree species, as the closeness centrality of rare genera was significantly higher than that of abundant genera. Conclusion Overall, the study suggested that the identity of tree species impresses the assembly of diazotrophic communities in its rhizosphere. Possible implication of our findings for forest management is discussed for maintaining nitrogen sustainability in forest ecosystems.

Continuous cropping leads to the development of serious fungal diseases in tobacco plants and depleted yield of tobacco ( Nicotiana tabacum ), which can be mitigated by organic fertilization. Yet, we know little about how organic fertilizers affect the fungal community of continuous cropping tobacco soil. In this study, we investigated the soil fungal community after 11 years of tobacco planting with chemical fertilization (CF) or chemical fertilization combined with organic fertilizers obtained from plant or animal origin, including oil cake (CFO), straw (CFS), and farmyard fertilizer (CFM). The predominant phyla of Ascomycota (70%) and Mortierellomycota (15%) were identified in all the treatments. A significantly higher proportion of Pyrenochaetopsis and lower relative abundance of Sordariomycetes were observed in the CFM group compared to the controls. Compared to CF and non-fertilized control (CK), CFO and CFS led to higher species richness ( P < 0.05), while CFM led to a less uniform fungal community, indicated by lower Shannon and higher Simpson diversity indices ( P < 0.05). Pearson’s correlation and redundancy analysis suggested that fertilizations primarily influenced the fungal community by altering the soil nutrient conditions, among which soil organic carbon and total phosphorus significantly correlated with the fungal diversity and community composition ( P < 0.05). Notably, FUNGuild annotation suggested that while other treatments showed no significant effect on the fungal trophic modes, CFM strongly increased the abundance of saprotrophic fungi by more than 30% ( P < 0.05), thus preventing the prevalence of potential pathotypes and symbionts. The results suggest that the type of organic fertilizers is essential to the long-term effects of organic application on the fungal community, and the animal-origin manure seems to be a better choice than plant-origin materials in continuous cropping tobacco fields.

Despite many studies on the influence of cropping practices on soil microbial community structure, little is known about ecological patterns of rare and abundant microbial communities in response to different tobacco cropping systems. Here, using the high-throughput sequencing technique, we investigated the impacts of two different cropping systems on soil biochemical properties and the microbial community composition of abundant and rare taxa and its driving factors in continuous and rotational tobacco cropping systems in the mountain lands of Yunnan, China. Our results showed that distinct co-occurrence patterns and driving forces for abundant and rare taxa across the different cropping systems. The abundant taxa were mainly constrained by stochastic processes in both cropping systems. In contrast, rare taxa in continuous cropping fields were mainly influenced by environmental perturbation (cropping practice), while governed by deterministic processes under rotational cropping. The α-diversity indices of rare taxa tended to be higher than those of the abundant ones in the two cropping systems. Furthermore, the network topologies of rare taxa were more complex than those of the abundant taxa in the two cropping systems. These results highlight that rare taxa rather than abundant ones play important roles in maintaining ecosystem diversity and sustaining the stability of ecosystem functions, especially in continuous cropping systems.

Background and aimsThe ability of plants to cope with environmental pressure and the interaction between rhizosphere microorganisms and host trees play an important role in the stability and function of forest ecosystems. Beneficial microbes recruited to the plant rhizosphere and stably association with tree roots can potentially reduce biotic stress, but the biochemical processes involved in coping with pathogen attack are not fully understood. Here, we aimed to investigate the ecology process of rhizosphere microbiota from four broad-leaved and three coniferous tree varieties involving in the suppression of soil-borne fungal pathogens. MethodsWe used separation cultivation and in vitro antagonistic experiments to investigate the inhibitory effects of rhizosphere microbiome on pathogenic fungi. Rhizosphere microbiome was then sequenced using the Illumina MiSeq platform, and root exudates of trees were measured by gas chromatography-mass spectrometry (GC-MS).ResultsRhizosphere microbes from seven tree varieties had strong inhibitory effects on fungal pathogens, nevertheless, there were significant differences in their capacity. The dissimilarities in rhizosphere bacterial communities that were significantly correlated with phylogenetic distance of trees had a greater influence on suppression of pathogens compared with microbial abundance and diversity. Combined analysis of a random forest model and co-occurrence networks, revealed a cooperative relationship between key groups that were positively associated with inhibition of fungal pathogens in the tree rhizosphere. This process was further strengthened by specific metabolites secreted by tree roots. ConclusionsIn general, the rhizosphere microbiota of seven tree species had different inhibitory effects on fungal pathogens, and the cooperative relationship within the rhizosphere microbial community plays an important role in maintaining trees resistance to soil pathogens stress.

为了解国内外人工林土壤地力的研究进展和发展趋势,采用文献计量学方法,以中国知网(CNKI)和Web of Science核心合集数据库相关文献为数据源,利用VOSviewer、HistCite等工具,从国家、机构、作者、研究热点方面对2021年之前的有关文献进行了计量分析.结果表明:国内外该领域年发文量呈逐渐增长趋势,国际上发文量前3位的国家是中国、美国和巴西;中国最先在该领域进行研究且与国际的合作交流较多,文献总被引频次位居前列;国内该领域发文机构主要为涉林高校及中国科学院下属研究所,国际上美国俄亥俄州立大学发表的文献质量明显突出,引用频次较高;现阶段国内外在该领域的研究主要围绕土壤微生物群落组成、土壤养分含量以及与土壤地力维持的关系,但多处在定量描述阶段,很少涉及微生物功能代谢与人工林下有机物质周转以及对土壤地力维持的影响机制,研究深度亟待提升.总之,国内外同行合作交流、学科间交叉融合以及新生研究力量的补充是未来有效提升该研究领域的关键所在.

Picea likiangensis (Franch.) Pritz., an evergreen alpine conifer woody plant species is endemic to Yulong snow mountains, Northwest China. It plays a crucial role in maintaining the succession and stability of an ecosystem. In this study, a multitude of physiological indices, such as chlorophyll, malondialdehyde, soluble sugar, proline, soluble protein, antioxidant enzymes (ascorbate peroxidase, catalase, peroxidase and superoxide dismutase), nutrient content (carbon, nitrogen and phosphorus), C/N ratio, N/P ratio and δC, were measured in the needles of P. likiangensis current-year sunny branches grown at four different altitudes (ranging from 2900 to 3350 m). Our results revealed significant changes in the leaf physiological and ecological traits of P. likiangensis along altitudinal gradients. The contents of chlorophyll (chlorophyll a, chlorophyll b and total chlorophyll), total phosphorus and total nitrogen of P. likiangensis reached the maximum values at 3200 m altitude, indicating that P. likiangensis has the highest photosynthetic capacity at this zone. In addition, the concentrations of soluble sugar, proline and soluble protein were increased along altitudinal gradients, suggesting that P. likiangensis exhibits high tolerance to abiotic stress via osmotic adjustment. Furthermore, the activities of ascorbate peroxidase, catalase and peroxidase were remarkably increased from 3200 to 3350 m altitude, implying that P. likiangensis had suffered from heavy abiotic stress in high-altitude area. Altogether, our findings revealed that 3200 m altitude might be the optimum zone for the growth of P. likiangensis in Yulong Snow Mountain, Northwest China. Nevertheless, the expansion of P. likiangensis population was limited by harsh environment at altitudes above 3350 m.

The rhizospheric microbial community is one of the major environmental factors affecting the distribution and fitness of plants. Ancient wild tea plants are rare genetic resource distributed in Southwest China. In this study, we investigated that rhizospheric bacterial communities of ancient wild tea plants along the elevational gradients (2050, 2200, 2350 and 2500 m) in QianJiaZhai Reserve of Ailao Mountains. According to the Illumina MiSeq sequencing of 16 S rRNA gene amplicons, Proteobacteria, Acidobacteria and Actinobacteria were the dominant phyla with the relative abundance 43.12%, 21.61% and 14.84%, respectively. The Variibacter was the most dominant genus in rhizosphere of ancient wild tea plant. Phylogenetic null modeling analysis suggested that rhizospheric bacterial communities of ancient wild tea plants were more phylogenetically clustered than expected by chance. The bacterial community at 2050 m was unique with the highest alpha diversity, tend to cluster the nearest taxon and simple co-occurrence network structure. The unique bacterial community was correlated to multiple soil factors, and the content soil ammonium nitrogen (NH4+-N) was the key factor affecting the diversity and distribution of bacterial community along the elevational gradients. This study provided the necessary basic information for the protection of ancient tea trees and cultivation of tea plants.

野生古茶树是亟需保护的珍稀种质资源.为了解野生古茶树根际土壤碳氮磷生态化学计量、微生物量碳氮和胞外酶活性的垂直分布格局,以千家寨野生古茶树群落为对象,采集千家寨4个海拔2 050 m(E1)、2 200 m(E2)、2 350m (E3)、2 500 m(E4)的野生古茶树群落的根际土壤,测定并分析其碳氮磷(C、N、P)生态化学计量、微生物量碳和氮(MBC和MBN)和胞外酶活性[磷素获取酶碱性磷酸酶(AKP)、碳素获取酶β-1,4-葡萄糖苷酶(βG)、氮素获取酶β-1,4-N-乙酰基氨基葡萄糖苷酶(NAG)和水解酶亮氨酸氨基肽酶(LAP)、多酚氧化酶(PPO)、过氧化物酶(PER)]的变化及其影响因素.结果显示,千家寨野生古茶树根际土壤C∶N较高(11.27-13.35),并随海拔升高而增加;C∶P和N∶P均随海拔升高呈先升高后降低的变化规律.根际土壤MBC和MBN随海拔升高呈先上升后下降的规律,分别受根际土壤含水量和铵态氮(NH4+)的影响.根际土壤AKP、βG和NAG活性随海拔升高均显著增加并与总磷含量(TP)密切相关,LAP活性在海拔上无显著变化,PPO活性随海拔升高而显著下降(P＜0.05).根际土壤胞外酶活性生态化学计量大小顺序是,βG∶(NAG+LAP)＞ ,βG∶AKP＞(NAG+ LAP)∶AKP,其中βG∶AKP和(NAG+LAP)∶AKP值均小于1.综上所述,不同海拔梯度上土壤碳氮磷生态化学计量、微生物量碳氮和胞外酶活性及其计量学差异显著,而TP是影响海拔梯度上野生古茶树根际土壤胞外酶活性大小的关键因子;千家寨野生古茶树根际土壤微生物受磷限制和碳限制相对于氮限制程度更高,在不同海拔中受碳氮磷限制的程度有差异;本研究结果对了解野生古茶树的养分循环和生态适应机制有重要意义.

以八角金盘(Fatsia japonica)幼苗为试材,设置CK(0 g/L NaCl)、S6(6 g/L NaCl)、S12(12 g/L NaCl)和S24(24 g/L NaCl)4种盐浓度进行盆栽处理,探讨盐胁迫对八角金盘幼苗光合特性及相关生理指标的影响.结果表明:(1)低浓度(S6)盐胁迫下,八角金盘的净光合速率及气孔导度显著降低(P<0.05),但光系统Ⅱ(PSⅡ)最大光化学效率(Fv/Fm)、叶绿素含量、抗氧化酶活性、丙二醛(MDA)含量和可溶性蛋白含量等均无显著变化;(2)中浓度(S12)盐胁迫下,八角金盘的净光合速率、叶绿素含量、光合电子传递速率(ETR)、过氧化物酶(POD)和PSⅡ光化学效率(YⅡ)显著降低(P<0.05),MDA含量显著增加(P<0.05),其通过调节非光化学淬灭系数(QN)及提高过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)3种抗氧酶活性来积极主动响应中浓度盐胁迫;(3)高浓度(S24)盐胁迫下,MDA含量显著上升(P<0.05),而POD和CAT酶活性降低,过氧化胁迫加重,Fv/Fm及YⅡ值降至最低,净光合速率亦较其他处理组更低.因此:低浓度盐胁迫对八角金盘幼苗的光合系统有一定抑制作用,但其可以通过调节自身的PSⅡ和抗氧化系统来积极应对;高浓度盐胁迫对八角金盘幼苗的光合生理具有较强的毒害作用,导致PSⅡ受损严重,抗氧化系统调节失效,生长受到严重抑制.

以洋常春藤扦插苗作为实验对象,分别对其进行不同浓度的CdCl2溶液水培处理,测定并分析镉胁迫对其叶绿素含量及荧光参数的影响。结果表明:在镉胁迫下,洋常春藤叶片的叶绿素a、叶绿素b以及总叶绿素含量均显著降低,叶绿素a/b比值显著升高,且变化程度随着镉胁迫浓度的增大而增大。在浓度20、80μmol/L的镉胁迫下,洋常春藤的叶绿素荧光参数光系统Ⅱ潜在最大光化学效率、光系统Ⅱ实际光化学效率、非光化学淬灭、光化学淬灭、电子传递速率无显著变化,说明在浓度小于80μmol/L的镉胁迫下洋常春藤叶绿素荧光参数光系统Ⅱ光合机构功能状态良好。而在浓度200、400μmol/L的镉胁迫下,尤其是400μmol/L时,可导致其光合机构受损,表现为潜在最大光化学效率、光系统Ⅱ实际光化学效率、非光化学淬灭和电子传递速率的显著降低,叶片初始荧光显著升高,说明此浓度的镉胁迫对洋常春藤的叶绿素荧光参数光系统Ⅱ光合机构功能有抑制作用。