Background and aimsSoil microbes play crucial roles in regulating soil nutrient cycling and shaping plant community structure in forest ecosystems. Compared with our understanding of plant community succession and soil nutrient changes, the succession of soil microbial communities and functional guilds after deforestation remains unclear.MethodsWe used 16S rRNA gene and internal transcribed spacer amplicon sequencing to investigate the microbial diversity and community composition in surface (0-10 cm) and subsurface (10-20 cm) mineral soils along a secondary succession after logging in Korean pine forests. Topological structures of microbial co-occurrence networks were also assessed.ResultsFungal diversity, community composition, and network structure, rather than bacterial, significantly changed with successional stages. Specifically, the diversity of ectomycorrhizal fungi (EcMF) in subsurface and whole soil layers, and saprotroph diversity in the subsurface, increased monotonically with increasing time since logging, while the relative abundances of plant pathogenic fungi decreased significantly with successional stages in surface and whole soil layers. Fungal network complexity (i.e., average degree) increased monotonically with increasing time since logging. Successional stages were the strongest driver of fungal community composition. In the subsurface layer, successional stages affected fungal diversity strongly and positively by increasing fungal network complexity.ConclusionsThis study revealed distinct successional trajectories for soil fungal and bacterial communities following forest logging. Compared with bacteria, fungi and their functional guilds (i.e., EcMF, saprotrophs, and plant pathogens) exhibited stronger responses to successional stages, indicating a more important role for facilitating the restoration of broad-leaved Korean pine forests after disturbance.

东北地区的温带森林是我国重要的森林类型之一,受全球气候变化及人类活动的干扰,东北温带森林的可持续发展受到威胁。本研究通过对吉林蛟河阔叶红松林的调查和室内数据的处理分析,运用植物学和生态学的基本研究原理和方法,对吉林蛟河不同恢复时期（10年,20年,30年,40年,50年）及不同采伐强度（采伐对照,轻度采伐,中度采伐,重度采伐）的阔叶红松林群落的恢复动态及恢复特征进行探讨,旨在为吉林蛟河阔叶红松林的保护提供理论依据。研究结果表明:（1）吉林蛟河阔叶红松林群落中共发现46科74属109种植物,其中蕨类植物4科5属5种,裸子植物1科3属4种,被子植物41科66属100种,单科单属单种现象显著。随着恢复时间及采伐强度的增加,乔木层物种组成变化较小,主要树种的优势度增加,相比之下林下灌木层及草本层的物种组成变化较大,灌木层优势物种的重要值有所下降,草本层优势物种的重要值随着恢复时间的增加无明显变化趋势,但随着采伐强度的增加重要值有所下降。群落物种多样性随着恢复时间的增加而增大,采伐干扰促进了物种多样性的增加,采伐干扰群落中中度采伐群落的物种多样性最大。（2）恢复50a群落径级结构呈近似双峰型分布,其余各群落均呈倒“J”型分布,小径级组（1≤DBH＜10cm）个体群重要值随着恢复时间的增加先下降后上升,随着采伐强度的增加而增加;中大径级组（DBH≥35cm）个体群重要值随着恢复时间及采伐强度的增加先上升后下降。随着恢复时间的增加,群落结构更加稳定,采伐干扰对群落结构产生了影响,其中中度采伐改善效果较好。（3）群落结构与物种多样性之间存在一定的相关性,RDA分析与Monte Carlo检验显示,在不同恢复时期的群落中“树高香农指数”是影响物种多样性的主要结构指数,在不同采伐强度的群落中“胸径香农指数”对物种多样性的影响最大。（4）从恢复10年群落到恢复40年群落的过程中,随着恢复时间的增加群落地上部分生物量随之增加,采伐在短期内降低了群落地上生物量。群落结构是影响群落地上生物量的重要因子之一,RDA分析与Monte Carlo检验显示,平均胸径对不同恢复时期群落地上生物量的影响最大,“胸径香农指数”与“胸径均匀度指数”对不同采伐强度干扰群落地上生物量的影响最大。

兴安落叶松是我国重要的林区资源,对维持大兴安岭地区生态平衡具有重要作用。由于大兴安岭地区是林火高发区,本研究以不同恢复时期的兴安落叶松林作为研究对象,研究分析不同恢复期森林群落的物种组成和土壤生物化学性状,探讨了地上植被与土壤功能的演变规律,采用Pearson相关性分析分析了不同恢复时期土壤化学性质、微生物量和酶活性和地表植被物种多样性指数的相关性,采用冗余分析法分析不同恢复时期灌木草本物种土壤影响因子,为林火干扰后兴安落叶松林群落功能的重建提供了理论基础。研究结果表明:（1）火烧干扰后短期内土壤养分含量较低,灌草群落阶段短期内林火显著影响土层0～5cm酸碱度、碱解氮、易氧化碳、全氮、DOP、微生物量和酶活性。白桦林阶段至落叶松林阶段树种更替影响土层0～5cm有机碳、酸碱度和碱解氮。（2）不同恢复时期火烧迹地土壤微生物量影响因子不同,相关性分析表明土壤氮素是不同恢复时期土壤酶活性主要影响因子。灌草群落阶段土壤上下层微生物量受土壤碳、氮元素的限制。白桦林阶段土壤上下层微生物量受土壤碳、磷元素的限制。落叶松林阶段土壤上下层微生物量受土壤氮素的限制。（3）不同恢复时期火烧迹地物种多样性和生物量发生改变,灌草群落阶段林火短期内降低了灌木草本物种多样性,且对白桦、落叶松幼苗影响显著,白桦幼苗占据优势。白桦林阶段到落叶松林阶段,落叶松幼苗占据优势,但林火促进灌木生物量的增加,降低草本多样性和生物量。（4）不同恢复时期林下植被物种多样性土壤影响因子不同。灌草群落阶段火烧迹地土壤上下层灌木多样性影响因子为土壤碳氮含量。白桦林阶段火烧迹地土层0～5cm灌木多样性影响因子为TN、MBP。落叶松林阶段火烧迹地土壤上下层灌木多样性影响因子为土壤碳磷元素含量和土壤微生物量。白桦林和落叶松林阶段草本多样性主要受土壤酸碱度、LAP酶活性的影响。（5）不同恢复时期林下植被具有相同的土壤影响因子。土层0～5cm灌木物种主要影响因子为p H,土层5～20cm灌木物种主要影响因子是碱解氮。

The potential improvement of biological nitrogen fixation (BNF) in legumes and edaphic factors affecting BNF remain unclear following biochar application to Ultisols. In this study, the effects of biochars derived from different feedstocks on BNF in soybean and soil properties were examined in an Ultisol. Straw biochar and manure biochar were applied at different rates (0, 24, and 48 t ha(-1)). The percentage of soybean N derived from BNF was determined by the N-15 isotope dilution method. Manure biochar and straw biochar increased BNF by 130% and 79% over the control when pooled across two application rates, respectively. However, biochar's improvement in BNF showed a decreasing trend with the application rates. Only manure biochar application at 48 t ha(-1) significantly stimulated N uptake in soybean from soil by 89% over the control. Manure biochar increased soil pH, total nitrogen, and soil available nutrients (P, K, Ca, Mg, Cu, Zn, and Mo) and reduced soil available Al to a greater extent than straw biochar. Soil pH, total nitrogen, and available nutrients (P, K, Ca, Mg, Cu, and Mo) could explain 34.5%-54.6% of the BNF variations. Among these edaphic factors, the improvement in soil available Mo induced by biochar was the most crucial to promoting BNF based on the random forest model analysis. In conclusion, biochar prompted BNF in soybean in the Ultisol, which could be attributed to the increase in soil available nutrients and the liming effect of biochar.

The role of biophysical variables in constructing community structure changes with the time since fire. The major objective of this study is to verify the transition stage and its underlying variables for the postfire forest and soil microbial function in the boreal forested area of China. A 50-year fire chronosequence was presented, and biomass of forbs, shrubs and woody plants was separately weighted to assess their contribution to the whole community with the year since fire (YSF). Simultaneously, soil biophysical properties were measured for stands in different time periods after fire. Soil microbial functions, i.e. growth efficiency (GE) and carbon use efficiency (CUE), were calculated based on ecoenzymatic and soil nutrient stoichiometry. In terms of vegetative structure, forbs' proportion decreased from 75% to 1.5%, but the proportion of woody plants increased from 0.04% to 70% across this fire chronosequence. GE and CUE of soil microorganisms averaged 0.242 and 0.236 and were significantly higher in 9, 15 and 31 YSF than in 2 and 3 YSF. Soil metal content was significantly increased at the late stage of this fire chronosequence, and soil calcium content showed a positive correlation with woody plant biomass and a negative correlation with soil microbial function. Overall, the present work highlights that the time period of 15 and 31 YSF is a hallmark stage for aboveground vegetative structure and soil microbial function to change in different trends and that the calcium content may partly account for these two divergent trajectories.

明确植被、土壤和微生物演替轨迹及其驱动机制，有助于揭示三者之间演替的非平衡规律，为退化天然森生态功能恢复提供理论依据。为此，在不同火烧年限的寒温带落叶松林和采伐不同演替阶段和不同强度的针阔混交林展开了相关研究。研究发现，随着火烧年限增加，植被群落由以草本和灌木为主逐渐向乔木为主的群落转化，而不同土壤指标并不存在一致性演变规律。火烧年限、有机层有效钙、矿质层pH值是驱动火烧迹地森林群落演替主控因子。土壤有机层外生菌根真菌群落随火烧恢复年限展现剧烈变化，火烧年限、土壤碳氮比和空间距离共同驱动真菌群落的演替。基于演替协同指数，我们发现土壤受到火烧干扰影响较小；土壤微生物在火烧14年左右得到恢复；植被群落演替表现为迟滞效应。采伐干扰后阔叶红松林群落演替依赖于红松种群的恢复，采伐强度对其群落结构具有重要的调控作用，中等强度采伐提高了植被物种多样性。适度采伐短期效应为凋落物数量不变，而凋落物质量提高，有利于土壤养分累积。采伐后不同演替阶段真菌群落随演替时期显著变化，而细菌群落无显著差别。alpha多样性和网络分析，表明土壤真菌和森林植被间更为同步化的演替轨迹。综上，植被—土壤—土壤微生物演替非平衡性以及植被和土壤微生物演替关键驱动因子的发现，为采取适当措施促进火烧迹地植被恢复提供了科学依据；而适度采伐经营有利于维持森林物种资源多样性和改善土壤养分供应。Clarifying the succession trajectories of forest community,soil properties and soil microbial community and their driving factors will help to reveal the non-equilibrium of their succession,which will provide a theoretical basis for the restoration of ecological functions of degraded natural forests.Therefore,some studies were carried out in distinct successional trajectories following wildfire in a cold-temperate forest and in the aspen boreal forest with different recovery stages and different logging intensities.With“time since fire”,the vegetation community gradually changed from herbaceous and shrub to arbore-dominated community.However,there was no consistent trend in the evolution of different soil properties.Time since fire,available calcium in the organic layer and pH in the mineral layer are the primary controlling factors of forest community succession.The ectomycorrhizal fungi community in the organic layer changed dramatically with the time since fire.Time since fire,soil C/N ratio and spatial distance were the primary drivers of fungal composition and succession.Based on the results of the succession synergy index,it showed that soil was less affected by wildfire and soil microorganisms recovered after 14 years following fire,while vegetation community succession showed a hysteresis phenomenon.The vegetation community successions after cutting depended on the recovery of Korean pine populations in the broad-leaved Korean pine forest.Logging intensity regulated the community succession and the moderate logging increased the diversity of vegetation species.The moderate logging in the short-term did not influenced the quantity of litters,but increased the quality of litters,which will be beneficial to the accumulation of soil mineral nutrients.The fungal community was influenced more greatly than the bacterial community in the successional trajectories following logging.Alpha diversity and network analysis showed a more synchronous succession trajectory between soil fungi and forest vegetation.In conclusions,the discovery of disequilibrium of succession among vegetation,soil and soil microbial succession and the primary driving factors for the vegetation and soil microorganism succession will provide some scientific basis to accelerate the vegetation restoration in burned forests.Moderate logging is beneficial to maintaining diversities of forest species and improving soil nutriment availabilities.

Aim There have been numerous studies of forest-soil microbial biogeography, but an integrated view of edaphic factors, plant, climatic factors, and geographic distance in determining the variation of bacterial community and assembly processes remains unclear at large spatial scales. Here, we analysed the factors affecting the biogeographic pattern and assembly processes of soil bacterial communities under 58 tree species in five natural mountain forests. Location Eastern China. Major taxa studied Bacterial communities. Methods Hierarchical partitioning analysis and distance decay models were performed to evaluate the relative contributions of plant phylogeny, environmental, and spatial variables to the composition of bacterial communities. We applied the nearest taxon index (NTI), beta-nearest taxon index (beta NTI), and the modified Raup-Crick metric to reveal the mechanisms of bacterial assembly processes. Results We found that plant phylogeny accounted for a significant, but minor, fraction (0.7%) of the variation in composition of bacterial communities. In contrast, soil pH was the primary determinant of bacterial diversity and community composition, independently explaining 68.6 and 69.9% of the variation, respectively. Based on the NTI analysis, bacterial community assembly was more phylogenetically clustered with increasing soil pH. Variable selection was the predominant process explaining bacterial community assembly when differences in soil pH were >= 0.83, whereas homogenizing dispersal dominated when differences in soil pH were <0.83. However, there was no significant relationship between plant phylogenetic distance and beta NTI. Main conclusions Our findings provide strong evidence that soil pH predominantly determines bacterial distribution and mediates the relative impact of stochasticity and determinism in soil bacterial community assembly. This suggests that climate-change associated forest soil acidification could have a dramatic impact on soil bacterial diversity, composition, and function.

Understanding the effects of thinning on forest productivity under climate change is vital to adaptive forest management. In the present study, the 3-PG m i x model was applied to simulate the thinning effects on productivity of Lartx olgensis plantations under climate change using 164 sample plots collected from the 6th, 7th and 8th National Forest Inventories in Jilin Province, northeast China. Climate scenarios of RCP 4.5 and RCP 8.5 were adopted from 2011 to 2100 with corresponding reference years (1981-2010). We simulated four cutting intensities: no-thinning, NT; low intensity thinning with 10% stem removal, LT; moderate thinning with 20% stem removal, MT and heavy thinning with 30% stem removal, HT for three times with 5- and 10-year thinning intervals. The results indicated that the mean net primary productivity (NPP) during the simulated 90 years was increased under RCP 4.5 and RCP 8.5. The LT and MT had positive but HT had negative effects on the mean NPP for the same climate scenario. Increased thinning intensity facilitated the positive effects of climate change on NPP but without a significant interaction effect. During the simulation, LT had the highest NPP value and HT had the biggest NPP increase under future climate change. We also discussed the management of larch plantations under climate change and advocated low intensity thinning with 10-year thinning interval to gain maximum NPP for mitigating climate change.

Soil fungi represent a major component of below-ground biodiversity that determines the succession and recovery of forests after disturbance. However, their successional trajectories and driving mechanisms following wildfire remain unclear.We examined fungal biomass, richness, composition and enzymes across three soil horizons (Oe, A1 and A2) along a near-complete fire chronosequence (1, 2, 8, 14, 30, 49 and c. 260 yr) in cold-temperate forests of the Great Khingan Mountains, China. The importance of soil properties, spatial distance and tree composition were also tested.Ectomycorrhizal fungal richness and beta-glucosidase activity were strongly reduced by burning and significantly increased with 'time since fire' in the Oe horizon but not in the mineral horizons. Time since fire and soil C : N ratio were the primary drivers of fungal composition in the Oe and A1/A2 horizons, respectively. Ectomycorrhizal fungal composition was remarkably sensitive to fire history in the Oe horizon, while saprotroph community was strongly affected by time since fire in the deeper soil horizon and this effect emerged 18 years after fire in the A2 horizon.Our study demonstrates pronounced horizon-dependent successional trajectories following wildfire and indicates interactive effects of time since fire, soil stoichiometry and spatial distance in the reassembly of below-ground fungal communities in a cold and fire-prone region.

Litter is essential to promote nutrient cycling and maintain the sustainability of forest resources. However, its variability has not been sufficiently studied at the local scale. The prediction of litter amount using ordinary cokriging with Pearson correlation analysis (COKP) and ordinary cokriging with principal component analysis (COKPCA) was compared with that using ordinary kriging (OK) based on cross-validation at the local scale of a 1-ha plot over natural spruce-fir mixed forest in Jilin Province, China. Litter samples in semidecomposed (F) and complete decomposed (H) horizons were collected using an equidistant grid point sampling of 10 m x 10 m. Pearson correlation analysis and principal component analysis (PCA) were used to confirm auxiliary variables. The results showed that the amount of litter was 19.65 t/ha in the F horizon and 10.37 t/ha in the H horizon. The spatial structure variance ratio in the H horizon was smaller than that in the F horizon, indicative of its stronger spatial autocorrelation. Spatial distributions of litter amount in both horizons exhibited a patchy and heterogeneous pattern. Of the selected stand characteristics and litter properties, litter moisture content indicated the strongest relationship with litter amount. Cross-validation revealed that COKPCA using the comprehensive score as an auxiliary variable produced the most accurate map. The average standard error and root-mean-square error between the predicted and measured values were always smaller, the mean error and mean standardized error were much closer to 0, and the root-mean-square standardized error was closer to 1 than COKP using litter moisture and OK. Therefore, a clear advantage of cokriging based on principal component analysis was observed and COKPCA was found to be a very useful approach for further interpolation prediction.