Qualitative Assessment of Postharvest Stomata and Chloroplast Degradation in Contrasting Abscission Resistant Balsam Fir (Abies balsamea (L.) Mill.)

Balsam fir is an important Christmas tree species, especially in eastern Canada. The natural Christmas tree industry faces a challenge in postharvest needle abscission. Though there have been many studies describing the physiological triggers and consequences in postharvest balsam fir, there have been no studies describing morphological or ultrastructural changes. Therefore, the objective of this study was to examine changes in stomata and chloroplast of postharvest needles. Branches were collected from low and high needle abscission resistance balsam fir genotypes, placed in water, and displayed in typical household conditions for 11 weeks. Needle abscission, chlorophyll fluorescence, and water uptake were monitored throughout. Needles stomata and chloroplasts were examined under a scanning and transmission electron microscope, respectively, each week. All branches had increased abscission, decreased chlorophyll fluorescence, and decreased water uptake over time. Needle surfaces accumulated fungal hyphae, especially in stomata. Chloroplasts demonstrated some dysfunction within two weeks, with notable decreases in chloroplast starch and increases in plastoglobulins. Within several weeks thylakoid membranes had been dismantled as chloroplasts transformed into gerontoplasts. All biophysical and structural changes were more pronounced in low needle abscission resistant genotypes. This research identifies a potential role for needle fungi in postharvest needle abscission and confirms the postharvest senescence of chloroplasts. Though it was previously speculated that chloroplasts must senesce postharvest, this study identifies how quickly this process occurs and that it occurs at different rates in contrasting genotypes.

中老年体检人群幽门螺杆菌感染与脉搏波传导速度及踝肱指数的相关性分析

了解大庆地区体检人群中动脉硬化检测开展情况,探究中老年体检人群幽门螺杆菌(Hp)感染与脉搏波传导速度(baPWV)及踝肱指数(ABI)之间的相关性。方法 选取2022年1月1日至2022年12月31日期间在大庆油田总医院健康管理中心进行体检的油田职工,需同时进行了动脉硬化检测及14C尿素呼气试验检测,并符合本项目纳排标准。基于大庆油田总医院健康管理中心体检数据库,清洗整理数据,分析传统动脉硬化危险因素与脉搏波传导速度之间的相关性,采用Logistic回归分析逐步校正各种影响动脉硬化的危险因素,分析幽门螺杆菌感染与baPWV是否存在相关性。结果 根据参与14C尿素呼气试验检测共466例,其中Hp感染弱阳性63例,阳性140例,阴性263例。设定Hp感染组203例(43.56%),非感染组263例(56.44%)。两组在颈动脉斑块检出率、hs-CRP上有差异(P<0.05)。与非感染组相比,Hp感染组双侧baPWV均升高,感染组的左侧baPWV(1732.54±362.57)cm/s、右侧(1721.36±379.45)cm/s(P<0.05),两组ABI差异不明显(P>0.05)。相关性分析,中老年体检人群Hp感染与baPWV间有正相关性(右侧r=0.483,P=0.002;左侧r=0.592,P=0.001),与ABI间无相关性(P>0.05)。结论 中老年体检人群幽门螺杆菌感染可能与baPWV的升高有相关性,及早发现及预防动脉粥样硬化,拓宽早期血管老化、动脉硬化、冠心病预防的新方向。

利用CRISPR/Cas9技术编辑MODD增强水稻休眠性

【目的】休眠是水稻重要的农艺性状。适当的休眠可以抑制水稻的穗发芽现象,是确保产量和品质的关键因素。然而,水稻休眠调控的基因及其调控网络仍需进一步研究。已知基因MODD编码未知功能的蛋白,负向调控水稻脱落酸信号和抗旱性,但其调控水稻休眠的功能未知。研究MODD在调控水稻休眠中的功能,有助于完善水稻休眠调控网络,同时为抗穗发芽遗传育种提供新的理论基础和种质资源。【方法】根据RGAP数据库公布的基因序列,构建MODD的CRISPR-Cas9敲除载体,通过农杆菌介导的遗传转化方法转化中花11(ZH11)愈伤组织,从而获得水稻转基因植株;利用PCR扩增、测序技术及qRT-PCR技术筛选并鉴定MODD敲除纯合系;根据2个突变系(KO-1和KO-2)的CDS得到突变系的氨基酸序列,然后,用DNAMAN对比ZH11和2个突变系(KO-1和KO-2)的蛋白序列;利用Linux系统筛选出MODD在水稻中的同源基因;取开花后35d的种子,调查ZH11和敲除系的发芽率;利用酵母单杂和LUC试验验证MODD的上游基因。【结果】查找到水稻中有6个MODD的同源基因,分别为LOC_Os07g41160、LOC_Os03g30570、LOC_Os03g53630、LOC_Os04g35430、LOC_Os03g17050和LOC_Os06g01170;成功构建了敲除载体,并转入ZH11中,获得2个纯合突变系(KO-1和KO-2);qRT-PCR结果表明,2个突变系(KO-1和KO-2)的MODD表达量显著降低;蛋白序列分析表明,KO-1和KO-2的移码突变造成了蛋白翻译的提前终止;发芽率结果显示,2个突变系(KO-1和KO-2)的发芽率在吸水第3天比ZH11分别显著降低了15%和15%;之后差异逐渐扩大,在第6天差异达到最大,比ZH11分别显著降低35%和35%;2个突变系(KO-1和KO-2)的穗发芽现象显著低于ZH11;酵母单杂试验结果表明,在酵母中,ABI5可以结合MODD的启动子区域,并且进一步把结合范围缩小至300 bp以内;LUC结果显示,加入ABI5的荧光值是单独加NONE空载荧光值的2.6倍,说明ABI5可以激活MODD的表达。【结论】敲除MODD可以增加种子的休眠,MODD可能通过ABA信号途径调控种子休眠。

不同中医证型2型糖尿病合并高血压患者血压节律类型与踝肱指数的相关性研究

目的:探讨不同中医证型的2型糖尿病合并高血压患者血压节律类型与踝肱指数(ABI)的关系,从而为糖尿病合并高血压患者临床综合治疗提供更好的方案及理论依据。方法:收集2型糖尿病合并高血压患者150例,其中痰热互结型39例、血瘀脉络型54例、气阴两虚型32例、阴阳两虚型25例,记录患者动态血压并确定血压节律类型,同时测定患者的ABI指数,比较不同中医证型患者血压节律类型与ABI指数之间的关系。结果:不同中医证型患者间ABI指数比较,差异有统计学意义(P<0.05),经两两比较,血瘀脉络型患者的ABI指数低于阴阳两虚型、痰热互结型、气阴两虚型患者的ABI指数(P<0.05或P<0.01);不同血压节律类型患者间ABI指数比较,差异有统计学意义(P<0.05),经两两比较,反杓型患者的ABI指数低于杓型、非杓型、超杓型患者的ABI指数(P<0.05);经Spearman秩相关分析,各证型患者夜间血压下降率与ABI值均呈显著正相关(P<0.01)。结论:2型糖尿病合并高血压患者中,血压节律类型为反杓型的患者及血瘀脉络型患者发生下肢病变及心血管事件的风险更高。

Early response of understory vegetation to the mass dieback of Norway spruce in the European lowland temperate forest

Spruce-dominated forests are commonly exposed to disturbances associated with mass occurrences of bark beetles.The dieback of trees triggers many physical and chemical processes in the ecosystem resulting in rapid changes in the vegetation of the lower forest layers.We aimed to determine the response of non-tree understory vegetation to the mass dieback of Norway spruce(Picea abies)in the first years after the disturbance caused by the European spruce bark beetle(Ips typographus)outbreak.Our study area was the Białowieża Biosphere Reserve covering the Polish part of the emblematic Białowieża Forest,in total 597km^(2).The main data source comprised 3,900 phytosociological relevés(combined spring and summer campaigns)collected from 1,300 systematically distributed forest sites in 2016–2018–the peak years of the bark beetle outbreak.We found that the understory responded immediately to mass spruce dieback,with the most pronounced changes observed in the year of the disturbance and the subsequent year.Shade-tolerant forest species declined in the initial years following the mass spruce dieback,while hemicryptophytes,therophytes,light-demanding species associated with non-forest seminatural communities,as well as water-demanding forest species,expanded.Oxalis acetosella,the most common understory species in the Białowieża Forest,showed a distinct fluctuation pattern,with strong short-term expansion right after spruce dieback,followed by a gradual decline over the next 3–4 years to a cover level 5 percentage points lower than before the disturbance.Thus,our study revealed that mass spruce dieback selectively affects individual herb species,and their responses can be directional and non-directional(fluctuation).Furthermore,we demonstrated that the mass dieback of spruce temporarily increases plant species diversity(α-diversity).

Assessment of Selenium Contamination in Sediments of the Aby and Tendo Lagoons in Côte d’Ivoire

Selenium is a trace element that can have both beneficial and harmful effects on aquatic life. The Aby Lagoon is a coastal environment in Côte d’Ivoire that receives selenium inputs from various natural and anthropogenic sources. The aim of this study was to assess the levels of selenium in the sediments of the Aby Lagoon and its tributaries, the Tanoe River and the Tendo Lagoon, and to examine the spatial and seasonal variations of selenium concentrations. Sediment samples were collected from different sites and seasons, and selenium concentrations were measured by atomic fluorescence spectrometry. The results showed that the average concentration of selenium in the sediments of the Aby Lagoon was 0.82 mg/kg, indicating moderate contamination. The concentration of selenium varied between sites and seasons, with higher values in the channel of the Tendo Lagoon and during the dry season. The study highlighted the complexity of selenium dynamics in aquatic ecosystems, and the need to take into account seasonal and spatial variability as well as interactions between environmental factors. The study also suggested potential ecotoxicological risks for some sensitive organisms in certain areas of the lagoon. This study contributes to the knowledge of the dynamics of selenium in lagoon ecosystems and to the assessment of the environmental risks associated with its presence.

Modeling effects of temperature and precipitation on carbon characteristics and GHGs emissions in Abies fabric forest of subalpine

Abies fabric forest in the eastern slope of Gongga mountain is one type of subalpine dark coniferous forests of southwestern China. It is located on the southeastern edge of the Qinghai-Tibet plateau and is sensitive to climatic changes. A process-oriented biogeochemical model, Forest-DNDC, was applied to simulate the effects of climatic factors, temperature and precipitation changes on carbon characteristics, and greenhouse gases （GHGs） emissions in A. fabric forest. Validation indicated that the Forest-DNDC could be used to predict carbon characteristics and GHGs emissions with reasonable accuracy. The model simulated carbon fluxes, soil carbon dynamics, soil CO2, N2O, and NO emissions with the changes of temperature and precipitation conditions. The results showed that with variation in the baseline temperature from -2℃ to ＋2℃, the gross primary production （GPP） and soil organic carbon （SOC） increased, and the net primary production （NPP） and net ecosystem production （NEP） decreased because of higher respiration rate. With increasing baseline precipitation the GPP and NPP increased slightly, and the NEP and SOC showed decreasing trend. Soil CO2 emissions increased with the increase of temperature, and CO2 emissions changed little with increased baseline precipitation. With increased temperature and decreased baseline temperature, the total annual soil N2O emissions increased. With the variation of baseline temperature from -2℃ to ＋2℃, the total annual soil NO emissions increased. The total annual N2O and NO emissions showed increasing trends with the increase of precipitation. The biogeochemical simulation of the typical forest indicated that temperature changes strongly affected carbon fluxes, soil carbon dynamics, and soil GHGs emissions. The precipitation was not a principal factor affecting carbon fluxes, soil carbon dynamics, and soil CO2 emissions, but changes in precipitation could exert strong effect on soil N2O and NO emissions.

Future of Abies pindrow in Swat district,northern Pakistan

Swat district is a biodiversity hub of Pakistan. The plant species, especially trees, in the Swat District are exposed to extinction threat from global climate change. Maximum entropy （MaxEnt） modelling of species distribution, using HADCM3 A2a global climate change scenario, pre-dicted a considerable change in the future distribution ofAbies pindrow （Royle ex D.Don） Royle. AUC （area under the curve）values of 0.972 and 0.983 were significant for the present and future distribution models of the species, respectively. It is clear that bioclimatic variables such as the mean temperature of the warmest quarter （bio_10） and the annual temperature range （bio_7） contribute significantly to the model and thus affect the predicted distribution and density of the species. The future model predicts that by the year 2080 population density will have decreased significantly. The highest density of the species is recorded in the eastern and western borders of the Valley in the areas of Sulatanr and Mankial. The changes in density and distribution of the species can have considerable impact, not only on the tree species itself, but on the associated subflora as well.

Dendroclimatic response of Abies spectabilis at treeline ecotone of Barun Valley, eastern Nepal Himalaya

A dendroclimatic study was conducted in the treeline ecotone of Barun Valley, eastern Nepal, to determine the tree-ring climate response and ring width trend of Abies spectabilis. A 160-year-old chronology, from 1850 to 2010, was developed from 38 tree-ring samples. No higher growth in recent decades was observed in tree-ring width in this area. The mean temperature of the current year in February and in the combined winter months of December, January, and February showed significant positive correlation with tree-ring width, although no significant correlation was found between tree-ring width and the precipitation pattern of the region. This tree-ring climate response result is different from that in other studies in Nepal, which could be attributed to location and elevation.

Growth response of Abies spectabilis to climate along an elevation gradient of the Manang valley in the central Himalayas

The Himalayas are characterized by a broad gradient of bioclimatic zones along their elevation.However,less is known how forest growth responds to climatic change along elevation.In this study,four standard treering width chronologies of Himalayan fir(Abies spectabilis)were developed,spanning 142–649 years along an elevation gradient of 3076–3900 m a.s.l.Principal component analysis classified the four chronologies into two groups;the ones at lower elevations(M1 and M2)and higher elevations(M3 and M4)show two distinct growth trends.Radial growth is limited by summer(June–August)precipitation at M3,and by precipitation during spring(March–May)and summer at M4.It is limited by spring temperatures and winter precipitation(December–February)at M1.Tree-ring width chronologies also significantly correlate with winter and spring Palmer Drought Severity Index(PDSI)at M1,and with summer PDSI at M3 and M4.Thus,Himalayan fir growth at high elevations is mainly limited by moisture stress rather than by low temperatures.Furthermore,the occurrence of missing rings coincides with dry periods,providing additional evidence for moisture limitation of Himalayan fir growth.

Plantlet regeneration through somatic embryogenesis in Nordmann's fir (Abies nordmanniana)

I studied the influence of various combinations of auxin and cytokinin concentrations, and the increased content of zinc and enzymatic casein hydrolizate in SH medium on initiation and proliferation of embryogenic callus of Abies nordmanniana （Steven） Spach. Addition- ally, the effect of ABA, PEG-4000 and different wave- lengths on the maturation of somatic embryos was tested. The use of optimum composition of modified SH medium with BA, KIN and 2.4-D while simultaneously ensuring appropriate external conditions resulted in 15.5 % embryogenesis. Finally, satisfactory results of microprop- agation of A. nordmanniana by somatic embryogenesis were obtained providing seven lines of embryogenic callus with high proliferation capacity. Those lines gave properly developed seedlings in white LED light with a wavelength of 400-700 nm, preceded by eight-week vernalization treatment of the callus. This paper may provide a protocol by which all stages of somatic embryogenesis of A. nord- manniana can be carded out, including the preceding 24-h seed disinfection with NaOCl and PVP, which resulted in 100 % frequency of uninfected zygotic embryos that were capable of starting embryogenesis.

Application of biostimulants for vegetative propagation of endangered Abies gracilis

Abies gracilis Kom.(Pinaceae)is one of the rarest and endangered conifers in the Russian flora,which must be cultivated ex situ to ensure its survival.Cuttings of A.gracilis do not take root without biostimulants.We used a selection of biostimulants,concentrations,and conditions of their use to significantly increase Abies gracilis rooting,and to accelerate the production of planting material,and to reduce rooting time to one season.We tested 4 rooting systems:IBA,IBA with glucose and glycine,and original biostimulants(S-try and S-5).The original S-5 biostimulating system had the most balanced ratio of components.The number of rooted samples increased 2.7 times and the length of roots increased 1.8 time when using S-5 as compared to IBA.S-try and S-5-original biostimulant systems were synthesized and collected in 2011 and 2014,respectively,and were tested in St.Petersburg Forest Technical University.

Variations in leaf functional traits and physiological characteristics of Abies georgei var.smithii along the altitude gradient in the Southeastern Tibetan Plateau

Variations in leaf functional traits of Abies georgei var. smithii at 3700, 3900, 4100, 4300, and 4390 m altitude were investigated in 15 typical plots in the Southeastern Tibetan Plateau. In each plot, three seedlings were selected, of which functional leaves in current-year sunny branches were chosen for the measurement of morphological, photosynthetic, and physiological and biochemical characteristics, and their variations were analyzed. Results showed that significant variations existed among the leaf functional traits of A. georgei var. smithii along the altitudinal gradient, as well as their physiological adaption indicators. Leaf area decreased, while the mass per area and thickness of leaf increased at an altitude above 4,100 m. The maxima of pigment, total nitrogen concentration, net photosynthesis rate during light-saturated, and when water use efficiency appeared at 4100 m altitude. In addition, A. georgei var. smithii seedlings regulated the activities of superoxide dismutase and ascorbate peroxidase to resist abiotic stress under 4100 m altitude. Meanwhile, malondialdehyde concentration and the dark respiration rate rapidly increased, which indicates that A. georgei var. smithii seedlingssuffered from heavy abiotic stress from 4100 m to 4390 m altitude. Basing on variations in leaf functional traits along the altitude gradient, we inferred that 4100 m altitude was the suitable region for A. georgei var. smithii growth in the Sygera Mountain. Moreover, the harsh environment was the main limiting factor for A. georgei var. smithii population expansion to high altitude.

Two new lanostane triterpenoids from Abies sachalinensis

The continuous chemical investigation on the ethyl acetate （EtOAc） soluble fraction of the MeOH extract afforded two new lanostane triterpenoid derivatives including one with a rearranged lanostane skeleton. They were identified as 3,4-seco-8-（14→13R）abeo-17,13-friedo-9β-lanosta-4（28）, 7,14（30）,24-tetraen-26,23-olide-23-hydroxy-3-oic acid （1） and 7,14-mariesa- dien-3oL-hydroxy-25-methoxy-26-oic acid （2）. Structural determination of these compounds were carried out by the spectral studies especially by the two digital （2D）-NMR and high-resolution MS experiences.

Streamwater chemistry and flow dynamics along vegetation-soil gradient in a subalpine Abies fabri forest watershed, China

Streamwater chemistry and spatial flow dynamics from a subalpine Abies fabri forest in an experimental watershed located in the east slope of Gongga Mountain were analyzed to gain insights into the gradient effect of primary community succession on the stream biogeochemical process. Results showed that high sand content(exceeding 80%) and porosity in the soil(exceeding 20% in A horizon and 35% in B horizon), as well as a thick humus layer on the soil surface, made the water exchange quickly in the Huangbengliu(HBL) watershed. Consequently, no surface runoff was observed, and the stream discharge changed rapidly with the daily precipitation. The flow trends of base ions in the stream water were influenced by the Abies fabri succession gradient. Ca 2+ , HCO - 3 and SO 2- 4 were the dominant anions in the streamwater in this region. A significant difference of Ca 2+ , HCO - 3 and SO 2- 4 concentration exported between the succession stages in the watershed can be found. But they had the similar temporal change in the stream flow. Ca 2+ , HCO - 3 and SO 2- 4 showed significantly negative correlations with the daily precipitation and the stream discharge. \;Concentrations of Cl -, Na +, K +, and Mg 2+ were low in all streamwaters monitored and we observed no differences along the Abies fabri succession gradient. Low ratios of Na:(Na+Ca) (range from 0.1 to 0.2) implied cations were from bedrock weathering(internal source process in the soil system) in this region. But, a variance analysis showed there were almost no differences between rainwater and streamwaters for Mg 2+ , Na +, K +, and Cl - concentrations. This indicated that they might be come from rainfall inputs(external source). The highly mobile capacity, rapid water exchange between precipitation and discharge, and long-term export lead to this observed pattern were suggested.

A weeding-duration model for Abies sachalinensis plantations in Hok-kaido, northern Japan

I developed a weeding-duration model for Sakhalin fir （Abies sachalinensis （Fr. Schmidt） Masters） plantations that employs a generalized linear model. The number of years following planting that weeding is necessary is the response variable, and elevation, slope steepness, maximum snow depth, annual precipitation, geology, soil, site index, slope aspect, and vegetation type are explanatory variables. Among the explanatory variables, geology, soil, slope aspect, and vegetation type are categorical data. A Poisson distribution is assumed for the response variable, with a log-link function. Elevation, slope steepness, maximum snow depth, annual precipitation, site index, and vegetation type had a significant effect on weeding duration. Among the eight models with the smallest Akaike information criterion （AIC）, I chose the model with no multicollinearity among the explanatory variables. The weeding-duration model includes site index, maximum snow depth, slope steepness （angle） and vegetation type as explanatory variables; elevation and annual precipitation were not included in the selected model because of multicollinearity with maximum snow depth. This model is useful for cost-benefit analyses of afforestation or reforestation with Abies sachalinensis.

Transcriptome analysis shows nicotinamide seed treatment alters expression of genes involved in defense and epigenetic processes in roots of seedlings of Picea abies

Nicotinamide treatment of plants and plant cell cultures has been shown to promote defense and decrease levels of DNA methylation.In the present study,we used RNA-seq technology to study overall changes in gene expression induced in roots of 3-month-old spruce(Picea abies)seedlings grown from nicotinamide-treated seeds to examine the molecular mechanisms underlying the defense promotion.Approximately 350 genes were identified as differentially expressed in roots after the seed treatment.Stress response genes,including transcription factors MYB77 and LHY and two chitinase enzymes,were generally upregulated,whereas genes thought to be involved in epigenetic regulation such as DDM1,known to promote DNA methylation,were present at high frequency among the downregulated genes.Across all samples,the expression of downregulated epigenetic-related genes was highly correlated with the nicotinamide treatment,indicating a common regulation.Our results support an earlier hypothesis regarding a potential role of nicotinamide as a defense-signal mediator.

Influence of topography,soil properties and plant community on the biomass of Abies georgei var.smithii seedlings in Southeast Tibet

Biomass of seedlings at different developing stages of growth is important information for studying the response of species to site conditions.The objectives of this study was to explore the distribution characteristics of AGB(above-ground biomass)and BGB(below-ground biomass)of Abies georgei var.smithii seedlings of different ages,and investigate the effects of topography(slope aspect,altitude),plant community characteristics(crown density,species diversity,etc.),and soil properties(soil physical and chemical properties)on the biomass and its allocation.Seedlings in five age classes(1–2,3–4,5–6,7–8,and 9–10 years old)were collected by full excavation from 6 elevations(3800 m,3900 m,4000 m,4100 m,4200 m,4300 m)on the north and south slopes of Sejila Mountain in Tibet.15seedlings of each age class were investigated at one altitude.The individual effects of seedling age(SA)and the interaction effects of SA,slope aspect(SL),and elevation(EG),namely,SL×EG,SL×SA,EG×SA,and SL×EG×SA,had significant effects on the AGB of the seedlings(p<0.05),whereas BGB was only significantly affected by SA(p<0.001).The AGB and BGB of the seedlings showed a binomial growth trend with the increase in seedling age,and had an allometric relationship at different elevations,α(allometric exponential)varied from 0.913 to 1.046 in the northern slope,and from 1.004 to 1.268 in the southern slope.The biomass of seedlings on the northern slope was remarkably affected by stand factors,with a contribution rate of 47.8%,whereas that on the southern slope was considerably affected by soil factors with a contribution rate of 53.2%.The results showed that age was the most important factor affecting seedling biomass.The allometric pattern of seedling biomass was relatively stable,but in a highaltitude habitat,A.georgei var.smithii seedlings increased the input of BGB.Understanding seedling biomass allocation and its influencing factors is useful for evaluating plants’ability to acquire resources and survival strategies for adaptation to the environment in Tibet Plateau.

Ecological environment analysis of Abies holophylla plantations under different cutting systems

Different types of plantations were observed in Baishilazi National Nature Reserve, Liaoning Province, for 34 a. The environmental quality ofAbies holophylla plantations was analyzed under different cutting systems. Analysis factors included soil erosion rate, humification degree of litters, and water hold capacity. The surface soil loss of clear cutting area was 19000t·km?2·a?1 more than that of selective cutting area. The content of soil organic matter in board-leaved—Abies holophylla forest was 4.62% more than that in pure stand, and the water hold capacity of the mixed forest was 1.43 time of that of pure stand. The mixed forest of board-leaved—Abies holophylla by selective cutting can upgrade the ecological environment quality.

Seasonal Changes in Soil Respiration with An Elevation Gradient in Abies nephrolepis(Trautv.)Maxim.Forests in North China

Soil respiration(Rs)plays an important role in regulating carbon cycle of terrestrial ecosystems and presents temporal and spatial heterogeneity.Abies nephrolepis is a tree species that prefers the cold and wet environment and is mainly distributed in Northeast Asia and East Asia.The Rs variations of Abies nephrolepis forests communities are generally environmental-sensitive and can effectively reflect the adaptive responses of forest ecosystems to climate change.In this study,the growing-seasonal variations of Rs,soil temperature,soil water content and soil properties of Abies nephrolepis forests were analyzed along an altitude gradient(2000,2100,2200 and 2300 m)over two years on Wutai Mountain in North China.As the main results showed,soil respiration keeps the same change trend as soil temperature and reached peaks in July at 2000 m in 2019 and 2020.During 26th July to 25th October in 2019 and 27th May to 23rd October in 2020,on the whole,the soil temperature independently explained 76.2%of Rs variations while the soil water content independently explained 26.8%.Soil temperature and soil water content jointly explained 81.8%of Rs variations.Soil properties explained 61.8%and 69.6%of Rs variation in 2019 and 2020,respectively.Soil organic carbon content and soil enzyme activity had the signifi-cant(P<0.01)negative and positive relationships,respectively,with Rs variation.With altitudes evaluated from 2000 to 2300 m,soil respiration temperature sensitivity(Q10)and the soil organic carbon content increased by 12.4%and 10.4%,respectively,while invertase activity,cellulase activity and urease activity dropped by 41.2%,29.45%and 38.19%,respectively.The results demonstrate that(1)soil temperature is the major factor affecting Rs variations in Abies nephrolepis forests;(2)weakened microbial carbon metabolism in high-altitude areas results in the accumulation of soil organic carbon;(3)with a higher Q10,forest ecosystems in high-altitude areas might be more easily affected by climate change;(4)climate warming might accelerate the consumption of soil organic carbon sink in forest ecosystems,especially in high-altitude areas.