It is widely accepted that old-aged forest can accumulate soil organic carbon (SOC). How microbial physiological traits respond to forest age and whether they drive SOC sequestration in old-aged forest remain elusive. Therefore, we compared the microbial C use efficiency (CUE), biomass turnover rate (rB), microbial biomass C (MBC) and necromass C (MNC) across soil profiles from middle and old-aged forest and evaluated how these microbial traits are related to SOC storage. The results revealed that both forests could accumulate SOC and old-aged forest supported higher SOC storage than middle-aged forest from 2005 to 2020. Moreover, SOC was concentrated on the surface soils of middle-aged forest, whereas it was more distributed across the deeper soil profile in old-aged forest. Compared with middle-aged forest, the O, A and B soil layers of old-aged forest presented increases in microbial CUE (17.8

Bauhinia faberi via.Microphylla(BFM)is an important tree species for vegetation restoration in the dry valley of southwestern China.However,there were few studies on the application of arbuscular mycorrhizal fungi(AMF)in improving the drought adaptation of BFM.In order to investigate the response of BFM to water stress(WS),we tested four inoculation treatments((no AMF,Control),Glomus mosseae(GM),Glomus intraradices(GI),Glomus mosseae+Glomus intraradices(GMI))in pots,experimented under three field water holding capacity(WHC)of 70％,50％and 30％.The changes of seedling survival rate(SR),AMF relative root length colonization rate(Col),growth,photosynthetic parameters,water status and leaf nutrients were examined.The results showed that under 30％WHC drought conditions,SR with dual inoculation of AMF was not higher than with single inoculation of GM,suggesting that increasing the diversity of AMF did not definitely improve plant SR,and that the species of inoculated AMF might have an important impact on SR.The sensitivity of dual inoculated Col to water stress was lower than that of single inoculation,which was more favorable for dual inoculated BFM seedlings adapting to drought environment.The overall drought resistance ability(D)also showed that dual inoculation of AMF improved plant drought adaptation compared with single inoculation,which was related to the higher Col of dual inoculated AMF.This study is of practical importance to promote vegetation restoration in arid areas in a cost-effective and environmentally friendly manner.

Soil microbial carbon use efficiency（CUE） is a critical physiological and ecological parameter in measuring soil C cycle and stock under the global change scenarios.It is defined usually as the ratio between carbon（C） allocated to growth and C taken up by microorganisms.It expresses the processes of C retention,turnover,soil mineralization,and greenhouse gas emission.CUE serves as a key regulator of microbial biomass turnover and soil C sequestration.Understanding the variation of soil microbial CUE and its influence mechanism in the context of global environmental change is critical for a better understanding of the partitioning of C between microbial biomass,and soil stock potential,and respiration,and the response of long-term C stock in soil to global changes.Soil microbial CUE and its response to environmental changes have received increasing attention from studies on soil carbon cycle,global change ecology,and terrestrial ecosystem models.In this review,it evaluated the advantages and adaptability of five microbial CUE measurement methods including 13 C(or 14 C) and 18 O isotope tracing approaches,calorespirometry,metabolic flux analysis,and stoichiometric modeling;it summarized the dynamic characteristics of soil microbial CUE with ecosystems,vegetation succession and different seasons;it analyzed the effects of the biological and abiotic factors including microbial community composition,substrate quality and nutrient availability,temperature,soil pH,soil moisture,soil aggregates and texture,soil layer depth,and anthropogenic disturbances on soil microbial CUE.According to the overview of CUE,the research prospect should be extended to:（1） Strengthen the soil microbial CUE research of forest ecosystems;（2） Explore the response process and mechanism of soil microbial CUE under the interaction of environmental and biological factors,especially for the effects of root exudates on soil microbial CUE and long-term carbon sequestration under the global changes;（3） Explore the dynamic of soil microbial CUE from microorganism’s ecosystem perspective;（4） Cross-compare CUE estimates by integrating different methods to capture different aspects of microbial metabolism and improve our understanding of processes controlling CUE variability;（5） Analyze dynamics of microbial CUE at the different soil layers and the influence of the CUE temperature sensitivity on long-term carbon stock in soil.

Soil microbial carbon use efficiency (CUE) is a vital physiological parameter in assessing carbon turnover. Yet, how the microbial assemblies with distinct trophic strategies regulate the soil microbial CUE remains elusive. Based on the oligotrophic-copiotrophic framework, we explored the role of microbial taxa with different trophic strategies in mediating microbial CUE (determined by a 13C-labeled approach) along the vegetation primary succession in Hailuogou glacier retreat area of the southeastern Tibetan Plateau. Results showed that soil microbial CUE ranged from 0.54 to 0.72 (averaging 0.62 ± 0.01 across all samples) and increased staggeringly along the vegetation succession. Microbial assemblies with distinct trophic strategies were crucial regulators of soil microbial CUE. Specifically, microbial CUE increased with microbial oligotroph: copiotroph ratios, oligotroph-dominated stage had a higher microbial CUE than copiotroph-dominated ones. The prevalence of oligotrophic members would be the underlying microbial mechanism for the high microbial CUE. Given that oligotrophs predominate in more recalcitrant carbon soils and their higher microbial CUE, we speculate that oligotrophs are likely to potentially enhance carbon sequestration in soils. In addition, the responses of the microbial CUE to fungal oligotroph: copiotroph ratios were higher than bacterial ones. Fungal taxa may play a dominant role in shaping microbial CUE relative to bacterial members. Overall, our results constructed close associations between microbial trophic strategies and CUE and provide direct evidence regarding how microbial trophic strategies regulate microbial CUE. This study is a significant step forward for elucidating the physiological mechanisms regulating microbial CUE and has significant implications for understanding microbial-mediated carbon cycling processes.

川西亚高山原始针叶林遭受大规模采伐后自然恢复形成的次生林已成为该区域的主要森林类型之一,具有重要的生态功能.现有森林生态功能评价大多为水源涵养等单一生态功能,尚缺乏针对多种生态功能的综合评价.采用空间代替时间的方法,以岷江冷杉原始林为参照,基于植物群落学与生物量调查,以及植物和土壤样品采集与测定,分析次生林植物多样性、碳储量、林地涵水能力三大生态功能恢复动态,探讨次生林生态功能恢复速率及其影响因素.结果显示:(1)随着次生林的恢复,林分综合生态功能显著提高,生态功能指数为原始暗针叶林(0.823 6)＞针阔叶混交林(0.5464)＞阔叶林(0.367 7).川西亚高山次生林生态功能恢复大约需要180年以上,不同生态功能恢复速率为植物多样性功能＞林地水源涵养功能＞固碳功能,不同演替阶段为阔叶林＞针阔叶混交林＞原始暗针叶林;(2)恢复到50-60年阔叶林具有较高的物种丰富度、Simpson和Shannon-Wiener指数,尤其是物种丰富度恢复速率较快,但恢复到老龄林相似的冠层物种组成需要较长的时间,可能与砍伐前为原始森林、残余森林呈镶嵌分布,以及桦木和岷江冷杉等建群种周转率低等有关;(3)林地持水能力以针阔混交林为最高,其中土壤蓄水量占绝对优势,针阔混交林具有较高的土壤毛管持水量,而针叶林土壤非毛管持水量较高.恢复速率为土壤毛管持水量(110年)＞枯落物持水量(118年)＞苔藓层持水量(135年);(4)随着林龄的增加,地上植被层和土壤碳储量显著增加,土壤层碳储量显著大于植被层,恢复速率为土壤(110年)＞地上部分(160年)＞枯落物层和苔藓层(＞200年),较快的土壤碳储存以及毛管持水量恢复速率与先前地上植被遭受严重破坏而地下土壤干扰较轻有关.本研究表明川西亚高山次生林生态功能恢复是一个漫长的过程,不同恢复阶段、不同生态功能恢复速率差异显著,应针对不同演替阶段采取不同的生态功能恢复策略,尤其要加强现有原始老龄林栖息地和残余老树的保护,注重构建针阔叶混交林结构,保护和促进次生林地被物层的恢复.

草地在大渡河干暖河谷植被恢复及植物群落演替中具有重要作用,而植被恢复的关键在于土壤质量。将大渡河干暖河谷泸定至汉源段,依据坡向划分为8个方位（北、东北、东、东南、南、西南、西、西北）,分析了不同坡向和植被盖度草地的土壤理化性质,采用主成分分析法（Principal component analysis, PCA）对河谷区草地土壤质量进行了评价。结果表明:（1）影响河谷草地土壤质量的最小数据集（Minimum data set, MDS）指标包括非毛管孔隙度、土壤容重、有机质和碳氮比;（2）河谷从东北坡过渡到西南坡土壤质量逐渐降低,与南坡热而干旱的微气候使土壤矿化作用剧烈,而北坡适宜的光热和水热条件更有利于土壤中钾和磷的释放有关;（3）植被盖度与土壤质量呈正相关关系,随着草地植被盖度减少土壤质量逐渐降低。高植被盖度（＞70%）土壤质量主要受非毛管空隙度影响,而低高盖度草地（＜30%）主要受土壤容重影响;（4）河谷区草地土壤质量指数中间值分布较多,土壤肥力属于2—4级中等水平。大渡河干暖河谷区草地土壤质量较好,潜在肥力水平较高,有利于植物生长和植物群落正向演替,是植被人工恢复的重点区域。

Soil bacterial microbial communities are important in the ecosystem function and succession of forests. Using high-throughput 16S rRNA gene sequencing and relative importance for linear regression, we explored how the structures of soil bacterial community were influenced by the environmental factors and restoration succession of secondary forests in the Miyaluo Mountains of western Sichuan, China. Using a space-for-time approach, field measurements and sampling were conducted in four stands at different stages of natural restoration. Results of distance-based multivariate analysis showed that soil pH, organic carbon, available phosphorus, and C/N ratio were the predominant environmental factors that collectively explained a 46.9% variation in the bacterial community structures. The community compositions were jointly controlled by the direct and indirect effects of the rehabilitation stages. The changes in soil environmental factors coincided with restoration succession could lead to the shifts in the relative abundance of different soil bacterial taxa. We screened 13 successional discriminant taxa that could quantitatively indicate the secondary succession subalpine stage. Collectively, our findings show that soil bacteria in different taxa are governed by different local soil variables and rehabilitation ages, which can lead to shifts in the relative abundance of different taxa in successional stages, ultimately changing the entire soil bacterial community with the succession of secondary forest.

大渡河中游干暖河谷区滑坡和泥石流灾害频发,对该区域坡面植物群落的研究有助于揭示植被演替的方向,为坡面植被生态恢复提供基本依据。本研究沿大渡河中游河谷区每隔约5km设置典型样地,调查了植被的物种组成和分布以及样地的地形、土壤等10个生境因子,探讨河谷区植被的连续性变化,并通过多元回归树（multivariate regression trees, MRT）、多样性指数和典范对应分析（canonical correspondence analysis, CCA）等方法对植物群落进行分类、比较和排序。结果表明:大渡河中游干暖河谷植被以土壤碳含量、pH值和C:N等3个因子为节点,可划分为多花胡枝子（Lespedezafloribunda）–荩草（Arthraxonhispidus）–香薷（Elsholtziaciliate）（群落A）、地果（Ficustikoua）–车桑子（Dodonaeaviscosa）–川滇薹草（Carexschneideri）（群落B）、云南松（Pinusyunnanensis）–栓皮栎（Quercus variabilis）（群落C）和荩草–扭黄茅（Heteropogon contortus）（群落D）等4种群落。该区域以灌木和草本为主要植被类型（群落A、B、C）,间或有裸地分布,易成为泥石流灾害产生的物源区;以多花胡枝子为主的灌草群落A的物种丰富度、优势度与多样性表现一致,均高于以乔木和草本为主的群落C和D,但物种多样性优势并不显著,灌草群落分布广而结构单一,外来物种占比为8.33%,是生态系统脆弱和不稳定的表现。多元回归树和典范对应分析结果表明, pH值、C:N、坡向和土壤容重等4个因子对植物群落组成和分布影响最大,且土壤因子的影响大于地形因子。

Gut keystone taxa disproportionally affect the function and stability of their resident community and thus are candidate targets for improving host health. However, how disease progression alters the assembly of gut bacterial community remains unclear. To fill this knowledge gap, we conducted Illumina sequencing of the bacterial 16S rRNA gene to explore the co-occurrence network and dynamic in the predicted functions of Pacific white shrimp (Litopenaeus vannamei) gut microbiota on disease progression. Results showed that temporal changes in the gut bacterial communities are positively parallel with shrimp disease severity. The diseased shrimp harboured a more complex bacterial network, higher connectivity and more diverse keystone taxa compared with the healthy cohorts. Gut keystone taxa were affiliated with Verrucomicrobiales and Alteromonadales in healthy shrimp, which shifted to Rhodobacterales, Vibrionales and Flavobacteriales in diseased cohorts. Removal of keystone taxa from co-occurrence networks led to network fragmentation in diseased shrimp, suggesting their fundamental role in sustaining the stability of gut microbiota. The relative abundances of the predicted functional pathways facilitating immune system and metabolism significantly (P < .05) decreased in the diseased shrimp. Intriguingly, the potentials of immunity and infectious diseases were significantly and positively associated with the relative abundances of keystone taxa. This work aids our understanding of the compositional, functional and ecological dynamics of gut microbiota over a shrimp disease progression. Additionally, the identified keystone taxa might facilitate the development of diagnostic and therapeutic targets for shrimp disease.

川西亚高山原始针叶林遭受大规模采伐后自然恢复形成的次生林已成为该区域的主要森林类型之一,也是我国西南林区水源涵养林的重要组成部分.现有亚高山森林水源涵养功能研究主要集中在暗针叶林,对天然次生林关注较少.选择川西米亚罗林区亚高山次生林自然恢复演替序列上高山柳灌丛、次生桦木阔叶林、岷江冷杉桦木针阔混交林,以相邻岷江冷杉成熟林为对照,采用空间代替时间的方法,基于土壤容重、孔隙度、持水性能等测定,分析了次生林恢复过程中土壤物理性质变化及土壤水源涵养效应动态,结果表明:(1)次生林恢复过程中,土壤容重总体呈下降趋势,除灌丛与阔叶林、针阔混交林、暗针叶林间具有显著差异外,其余植被类型间无显著差异,随着土层的加深,土壤容重呈增加趋势;(2)不同恢复阶段土壤孔隙度具有显著差异,以针阔混交林0—30 cm土层总孔隙度(64.39％)和毛管孔隙度(50.49％)为最高,灌丛总孔隙度(41.25％)和毛管孔隙度(33.70％)为最低;而土壤非毛管孔隙度以暗针叶林(14.27％)为最高;随着土层的加深,土壤孔隙度大致呈现出递减的趋势;(3)随着林龄增加,次生林土壤0—30 cm土层最大持水量呈波动性增加趋势,在针阔叶混交林阶段达到最大(1815.02 t/hm2),到暗针叶林阶段有所下降(1659.88 t/hm2);土壤毛管持水量以针阔混交林(1369.72 t/hm2)为最高,而非毛管持水量以暗针叶林(534.95 t/hm2)为最高,暗示针阔混交林树木生长所需有效水贮存量较大,亚高山暗针叶林具有较强的土壤水分调节能力和土壤渗透能力.从水源涵养功能角度,川西亚高山森林植被恢复应注重构建针阔叶混交林结构.

Increasing intensity and frequency of coastal pollutions are the trajectory to be expected due to anthropogenic pressures. However, it is still unclear how and to what extent bacterioplankton communities respond to the two factors, despite the functional importance of bacterioplankton in biogeochemical cycles. In this study, significant organic pollution index (OPI) and offshore distance gradients, as respective proxies of disturbance intensity and disturbance frequency, were detected in a regional scale across the East China Sea. A multiple regression on matrices (MRM) revealed that the biogeography of bacterioplankton community depended on spatial scale, which was governed by local characters. Bacterioplankton community compositions (BCCs) were primarily governed by the conjointly direct (-0.28) and indirect (-0.48) effects of OPI, while offshore distance contributed a large indirectly effect (0.52). A SEGMENTED analysis depicted non-linear responses of BCCs to increasing disturbance intensity and disturbance frequency, as evidenced by significant tipping points. This was also true for the dominant bacterial phyla. Notably, we screened 30 OPI-discriminatory taxa that could quantitatively diagnose coastal OPI levels, with an overall 79.3% accuracy. Collectively, the buffer capacity of bacterioplankton communities to increasing disturbance intensity and disturbance frequency is limited, of which the significant tipping points afford a warning line for coastal management. In addition, coastal pollution level can be accurately diagnosed by a few OPI-discriminatory taxa.

川西亚高山森林在20世纪下半叶遭受长时期连续砍伐,形成了采伐迹地上天然次生林恢复演替序列.该研究采用空间代替时间方法,以立地条件相似的暗针叶林作为对照,分析川西亚高山暗针叶林采伐迹地上次生林自然恢复过程中乔木层优势种组成及其影响因子.结果 表明:(1)研究区亚高山天然次生林恢复演替过程中,不同演替阶段土壤各养分差异显著,其中土壤总氮、土壤总磷、土壤有效磷、土壤有效氮均在针阔昆交林阶段最高,土壤pH值的变化在5.42～7.39范围波动,土壤有机碳随恢复的进行而增加,土壤C/N主要集中在15左右,只有针叶林达到18.62.(2)研究区次生林以16个乔木树种为主,针叶树种主要有粗枝云杉、岷江冷杉,阔叶树种主要有红桦、青榨槭等,且不同恢复阶段的群落乔木层优势种差异显著(RANOSINM=0.439,P＜0.001).(3)多元回归树分析发现,次生林乔木层优势种组成主要受林龄、土壤有机碳和总氮的影响,其中在次生林恢复演替后期(80a后),乔木层组成可能主要由于种间竞争导致,在次生林恢复演替前、中期(80a前),环境选择可能是影响乔木层组成差异的主导因素.(4)反向选择筛选结果显示,土壤总氮、海拔高度、土壤有效磷和土壤有机碳是影响乔木层优势种差异的主要因子.

The various post-translational modifications (PTMs) of plant proteins have important regulatory roles in development. We therefore examined various modified proteins from strawberry stigmata and found that succinylation of lysine residues was the most abundant type of modification. We then subjected proteins from strawberry stigmata to an efficient enrichment method for succinylated peptides and identified 200 uniquely succinylated lysines (Suks) in 116 proteins. A bioinformatics analysis revealed that these proteins are involved in important biological processes, including stress responses, vesicular transport, and energy metabolism. Proteomics, combined with immunoprecipitation and immunoblotting, revealed an obvious increase in succinylation of the assembly polypeptide 2 (AP2) and clathrin from 0.5 to 2 h after pollination, suggesting that succinylation is involved in the recognition of pollen-stigma signaling substances and vesicular transport. These results suggest that AP2/clathrin-mediated vesicular transport processes are regulated by lysine succinylation during pollen recognition.

Old-growth forests are carbon sinks as supported by increasing evidence in recent years. However, finding a resolution of the contradiction between the carbon sink function and neutral hypothesis at the community and individual scales is still a challenge. Tree size heterogeneity may offer an alternative answer. To determine this point, we studied subalpine (above an altitude of 3000 m) primeval Abies fabri forests located in the western part of China by comparing theoretical predictions and actual results. In theory, we first derived a model of the general carbon use efficiency (CUE) based on an individual scale, which allowed us to obtain the stand CUE by incorporating the carbon budget of all individuals. Afterwards, we quantified the effects of the gradual disturbance on the mortality of individuals with different sizes and predicted that the size of most individuals will trend to be medium (relative to the largest with the state of carbon neutral), meaning that the CUE of old stands has a high probability of tending to be a certain value (e.g. 0.4). In practice, the CUEs of old and middle-aged communities (0.405 and 0.602) calculated by the model were exceedingly close to the actual (0.401 and 0.597), indicating the effectiveness of the model. Further model-based analyses were performed, showing that the CUE of two old communities at different altitudes during the period from 2005 to 2015 were around 0.40, which are different from the reduced CUE from 0.64 to 0.60 in the middle-aged community. Meanwhile, in old forests, heterogeneous individuals dominated by medium-sized individual trend to be stable. Our findings indicated that with the increases in gradual disturbance events, a stable distribution of medium-sized individuals is an important cause for the carbon sink of old stands, and most of the carbon uptake by trees may further be stored in the soil. In addition, our model implied that environmental factors may change the forest carbon sink capacity by affecting the individual's potential maximum biomass.

Thioredoxin (Trx) can regulate disulfide bond reduction of target proteins to maintain the reduced intracellular state in various organisms. Here, we cloned a cDNA sequence of thioredoxin from Neobenedenia melleni , which is a kind of platyhelminth parasite infecting many fishes of great economic value. The deduced N. melleni Trx (NmTrx) contained 170 amino acid residues with an active site consisting of four amino acid motif CPGC. Sequence comparison and phylogenetic tree analysis confirmed NmTrx as a distinct member of thioredoxin. Real-time quantitative polymerase chain reaction (PCR) revealed a significantly higher expression of NmTrx transcript in the adult stage compared with the egg and oncomiracidium stages. In the egg and adult stages, the NmTrx transcript level in the 32°C group was higher than those in the 18 and 25°C groups. NmTrx was expressed and purified from Escherichia coli , and antiserum against NmTrx was prepared. Western blot confirmed the higher NmTrx expression of the egg and adult stages in the 32°C group with respect to the other temperature groups. Recombinant NmTrx was able to reduce the disulfide bond in insulin, and its antioxidant capacity was determined to be 5.12 U/mg protein, similar to the classic thioredoxins. Trx activity was lower in the oncomiracidium stage and higher in the adult stage compared with the egg stage. These results indicate that NmTrx could function as an important antioxidant molecule under physiological conditions. Keywords: Thioredoxin, Neobenedenia melleni , redox regulation, mRNA expression, prokaryotic expression