A spatio-temporal multi-scale fusion algorithm for pine wood nematode disease tree detection

Pine wood nematode infection is a devastating disease.Unmanned aerial vehicle(UAV)remote sensing enables timely and precise monitoring.However,UAV aerial images are challenged by small target size and complex sur-face backgrounds which hinder their effectiveness in moni-toring.To address these challenges,based on the analysis and optimization of UAV remote sensing images,this study developed a spatio-temporal multi-scale fusion algorithm for disease detection.The multi-head,self-attention mechanism is incorporated to address the issue of excessive features generated by complex surface backgrounds in UAV images.This enables adaptive feature control to suppress redundant information and boost the model’s feature extraction capa-bilities.The SPD-Conv module was introduced to address the problem of loss of small target feature information dur-ing feature extraction,enhancing the preservation of key features.Additionally,the gather-and-distribute mechanism was implemented to augment the model’s multi-scale feature fusion capacity,preventing the loss of local details during fusion and enriching small target feature information.This study established a dataset of pine wood nematode disease in the Huangshan area using DJI(DJ-Innovations)UAVs.The results show that the accuracy of the proposed model with spatio-temporal multi-scale fusion reached 78.5%,6.6%higher than that of the benchmark model.Building upon the timeliness and flexibility of UAV remote sensing,the pro-posed model effectively addressed the challenges of detect-ing small and medium-size targets in complex backgrounds,thereby enhancing the detection efficiency for pine wood nematode disease.This facilitates early preemptive preser-vation of diseased trees,augments the overall monitoring proficiency of pine wood nematode diseases,and supplies technical aid for proficient monitoring.

Investigation of beetle species that carry the pine wood nematode,Bursaphelenchus xylophilus(Steiner and Buhrer)Nickle,in China

In order to found new carriers of pine wood nematode(PWN),Bursaphelenchus xylophilus,beetles were collected from pine wilt disease-affected areas in six provinces in China.A total of 8830 beetles of 29 species was collected and examined to determine whether they were PWN carriers.Eight species were identified as carriers.Results included the first worldwide report of Monochamus uigromaculatus,Semanotus siuoauster,and Uraecha angusta being carriers of PWN,and the first report from China of A rhopalus rusticus carrying PWN.Monochamus alternatus was commonly collected in all six provinces and was the dominant species in four inland affected areas and A.rusticus was dominant in two coastal affected areas.The species varied between different neighboring regions in the same province.The distribution of the same species varied considerably over different regions.

Emamectin benzoate 9.7%SL as a new formulation for a trunkinjections against pine wood nematode,Bursaphelenchus xylophilus

In this study,we investigated the preventive effects of emamectin benzoate 9.7%SL,which was newly developed to reduce the injection volume and number of injection holes required to protect against pine wood nematode.None of the Pinus thunbergii trees injected with emamectin benzoate 9.7%SL at 0.3 mL/cm diameter at breast height(DBH)died within 2 years of inoculation with pine wood nematodes.Emamectin benzoate 9.7%SL injected at 0.6 mL/cm DBH resulted in no tree mortality for 3 years.Mean residue of emamectin benzoate 9.7%SL in pine twigs injected with 0.3 mL/cm DBH was 0.490μg/g at 1 year after injection and 0.303μg/g after 2 years.These residues values are greater than 0.031μg/g,previously determined IC95 value for emamectin benzoate against the pine wood nematode.Our field experiment and residue analysis showed that emamectin benzoate 9.7%SL could be a substitute agent for emamectin benzoate 2.15%EC,which is widely used to prevent pine wood nematode in the field and that injection volume and number of injection holes can be greatly educed using this new formulation,which will reduce injury to the cambium,interruption of water movement,and infection of inoculation wounds by wood-decay or blue stain fungi.

Adaptation of pine wood nematode,Bursaphelenchus xylophilus,early in its interaction with two Pinus species that differ in resistance

Pine wilt disease(PWD)is one of the most devastating diseases of Pinu s spp.and is caused by the pine wood nematode(PWN),Bursaphelenchus xylophilus(Steiner&Buhrer)Nickle.To study adaptation of PWN to survive in hosts that differ in resistance,we examined the self-regulatory characteristics of PWN at the biological and molecular levels early in the interaction.Two-year-old susceptible Pinus thunbergii and resistant Pinus taeda were selected for this experiment,and changes in PWNs after inoculation were assessed.q RT-PCR was used to detect changes in genes related to PWN pathogenicity and detoxification.The results showed that the migration and reproductive abilities of PWNs in P.thunbergii were stronger than those of PWNs in P.taeda.After 7 d,the number of nematodes in P.thunbergii was approximately 3.2-fold higher than in P.taeda.After 15 d,the number of nematodes in P.thunbergii was approximately twofold higher than that in P.taeda.Because PWN can adjust its sex ratio after infection,we compared the sex ratio of uninoculated PWNs,to that in the two pine species.In P.thunbergii,the female to male ratio first decreased and then stabilized over time;in P.taeda first decreased and then increased.Relative fat accumulation in PWNs increased significantly after the PWNs entered the tree body;the accumulation rate in P.thunbergii was higher than in P.taeda at 7 d,but lower after 15 d.Scanning electron microscopy(SEM)showed significantly more bacteria on the surface of PWNs in P.taeda compared with PWNs in susceptible P.thunbergii.At 12 h after inoculation,the expression of genes related to cell-wall degradation(Bx Beta1-4 and Bxpel1),effectors(Bx CDP1,Bx Sap B1),and active oxygen metabolism(Bxy-ctl-1 and Bx GST3)was 2–6×higher in the resistant pine than in the susceptible one.In contrast,in PWNs,the expression of autophagy-related genes Bx ATG1 and Bx ATG16 was 1.5–2 times higher in P.thunbergii than in P.taeda.These results indicate that the interaction between PWNs and pine trees with different resistance levels elicits a series of physiological and molecular adaptations that affect nematode reproduction and virulence.This study will help elucidate the adaptive mechanisms of PWN in different pine trees.

Influence of Ammoniacal Copper Quaternary treatments on mechanical properties of blue-stained Lodgepole Pine wood

Three concentrations （2.8%, 2.0%, 1.2%） of Ammoniacal Copper Quaternary （ACQ） was selected to treat Lodgepole pine wood for evaluating ACQ treatment on mechanical properties of blue-stained wood. The bending modules of elasticity （MOE）, modules of rupture （MOR）, toughness and shearing strength parallel to grain on tangential surface, are tested according to the criteria GB1927-1943-91. Non-treated sample were also tested according to the same procedure. The results showed that the three groups specimen impregnated by different concentrations of ACQ solution met the AWPA standard 2003 of America （UC4A 6.4g/cm^3）. There were significant difference of toughness between treated wood and non-treated wood （p=0.01）, but there were no statistically significant differences among three concentrations in terms of toughness, and toughness of treated wood was approximately 20% lower than non-treated. MOR, MOE as well as sheafing strength parallel to grain were found to be not significantly different between treated wood and non-treated one, and there were no statistically significant difference among three concentrations of ACQ too. Toughness, MOR, MOE and sheafing strength parallel to grain increased with decrease of concentration of ACQ, but they were hardly affected by ACQ preservatives.

Analysis of Influencing Factors of Pine Wood Nematode Disease in Lu an City Based on GIS

[Objectives]The paper was to figure out the distribution of Monochamus alternatus in the stumps of pine wood nematode infected wood in Lu'an City and to provide a theoretical and practical basis for differentiated prevention and control of pine wood nematode disease in the future.[Methods]The factors influencing the number of epidemic small classes and infected plants in all counties and districts of Lu'an City were analyzed by GIS method,and the number of worms and wormholes of M.alternatus inside and outside the stumps of pine wood nematode infected wood in Lu'an City were investigated on the spot.[Results]There were 98,40,54,781,193,268 and 34 epidemic small classes of pine wood nematode disease,and 7241,6099,9532,39161,11079,49876 and 4853 infected plants in Yu'an District,Jin'an District,Yeji District,Shucheng County,Huoshan County,Jinzhai County and Huoqiu County,respectively.Pine wood nematode disease in Lu'an City mostly occurred in Huoshan County,Shucheng County and Jinzhai County,with relatively high altitude,paddy soil,the annual precipitation higher than 2062 mm,and the annual average temperature lower than 16.2℃.The number of diseased plants of pine wood nematode disease was positively correlated with altitude and annual precipitation,and was negatively correlated with annual average temperature.The number of worms and wormholes in pine wood nematode infected wood was very small at different altitudes,stump heights and stump diameters.[Conclusions]The pine wood nematode infected wood can be differentially processed after stump treatment,and stumps can be peeled.The results will provide a theoretical and practical basis for differentiated prevention and control of pine wood nematode disease in the future.

COMPARATIVE STUDY OF WOOD PROPERTIES BETWEENWHITE WOOD OF DAHURIAN LARCH AND MONGOLIANSCOTCH PINE

The comparative result shows that the physical and mechanical properties of wood between white wood of Dahurian larch (Larix gmelini (Rupr.) Rupr.) and Mangolian scotch pine (Pinus cylvesthe var. mongolica) are different Some differences are very conspicuous,(e. g. compressivc strength parallel to grain, modulus of elasticity in static bending, toughness and bending strength etc. ),and others are slightly conSPicuous or not conspicuous,(e.g. shrinkage, differential shrinkage and shearing strength parallel to grain etc.). The properties of white wood of Dahurian larch are suitable weight and soft texture, median strength,median shrinkage and good in worability, while which of Mongolian scotch pine are light and soft nearly very soft,weak strength, median shrinkage are good in workability. However, the white wood of Dahuran larch is superior to the Mongolian scotch pine in Strength-to-weight ratio.It is a valuable timber tree.

Effects of Pulsed Magnetic Field on Biochemical and Physiological Characters and Ultrastructure of Pine Wood Nematode

In this paper,we employed the pulsed magnetic field(PMF) processing to investigate the effect of different pulse rise time and treatment time on the survival,reproduction,cellulase activity and surface characteristics of the pine wood nematode (PWN).The results showed that the wider pulse and the longer treatment time were able to reduce the survival,and inhibit the cellulase activity and reproduction of PWN.The 4th instar and females had a strong resistance to the pulsed magnetic field. With pulse rise time of 10 ms and the treatment of 60 min,the adjusted mortality of PWN was 100%. After the PMF treatment,the cellulase activity of PWN increased within a short time,and then declined with the treatment time.The observation with a scanning electron micrograph(SEM) revealed that there was no significant change in morphology of PWN,but the quantity of rod-shaped bacteria carried by PWN was reduced.

First record of Bursaphelenchus rainulfi on pine trees from eastern China and its phylogenetic relationship with intro-genus species

Bursaphelenchus rainulfi isolated from dead pine trees in Zbejiang, China, is described and illustrated. It also provided some molecular characters of the Chinese population, including the PCR-RFLP and sequences of ITS region and D2-D3 expansion region of the large subunit （LSU） rRNA gene. Both the morphological characters and ITS-RFLP patterns match with the original description. The phylogenetic trees based on the 13 sequences of D2-D3 expansion region of the LSU rRNA gene and ITS region of Bursaphelenchus species were constructed, respectively, with the results showing the similar clades. The phylogenetic relationship based on the molecular data is similar to that with morphological characters. This is the first report of the species on pine wood in eastern China.

Resistance genes mediate differential resistance to pine defensive substances α-Pinene and H_(2)O_(2) in Bursaphelenchus xylophilus with different levels of virulence

The pine wood nematode(PWN),Bursaphelenchus xylophilus(Steiner & Buhrer) Nickle,is the pathogen of pine wilt disease(PWD) which can devastate forests.PWN can be of hi gh or low severity and the mechanisms underlying the differences in virulence are unclear.Therefore,it is necessary to study the relationship between differentiation of PWN severity and its resistance to the main defensive substances of pine species(i.e.,α-pinene and H_(2)O_(2)).The feeding rate and fecundity of PWN was examined at different levels of virulence under conditions of a-pinene and H_(2)O_(2) stress.Moreover,the expression patterns of the main resistance genes of PWN with different virulence were determined under conditions of α-pinene and H_(2)O_(2) stress.The feeding rate and fecundity of the high virulence strain AMA3 were higher than those of the low virulence strain YW4.The expression levels of the autophagy gene BxATG5,cytochrome P450 gene BxCYP33 D3,and glutathione S-transferase genes BxGST1 and BxGST3 in AMA3 increased significantly upon exposure to α-pinene for 2 h,while these genes showed smaller degrees of upregulation in YW4.Under conditions of H_(2)O_(2) stress,the expression levels of BxATG5,catalase genes Bxy-ctl-1 and Bxy-ctl-2,and the 2-cysteine peroxiredoxin gene BxPrx in AMA3 were higher than those in YW4.These findings suggest that high virulence PWN has greater resistance to pine defensive substances α-pinene and H_(2)O_(2) than low virulence PWN,and resistance genes mediate the differential resistance of PWN strains.This study will contribute to the clarification of the mechanism underlying virulence differentiation of PWN and will advance understanding of the pathogenic mechanism of PWD.

Theory and Practice of Controlling and Extinguishing Pine Wilt Disease

[Objective] This study was aimed to review the controlling experience of pine wilt disease in the past 25 years, explore the theories and methods of controlling pine wilt disease, and improve the scientific level of controlling techniques and the protection capacity of healthy pine trees. [Method] Eleven items of effects were used to refine the theory of clearing dead pine trees affected by pine wilt disease, namely, ＂1 priority＂, ＂2 objections＂, ＂3 principles＂, ＂4 measures＂, and ＂5 manage- ments＂. On the basis of comprehensive control and complete removal of the infect- ed pine trees, a variety of comprehensive and efficient controlling methods were developed to carry out targeted chemical ecology trapping, bionic pesticide killing and releasing natural enemies of Sclerodermus guani, Dastarcus helophoroides. High ef- ficient emamectin benzoate immune injection was developed to inject the healthy pine trees for prevention, so as to extinguish the pine wilt disease. [Result] The pine wilt disease dropped from the peak of 3.5 million dead trees with an infecting area of 28 273 hectares in 1999 to 0.068 million with an area of 4 333 hectares in 2012 gradually, reducing by 98.06% in number and 84.84% in area, respectively. On the basis of removal, Dastarcus helophoroides was also released, which could make the number of dead pines decrease more significantly than the control, and af- ter releasing for 5 consecutive years, the dead pine trees dropped to 0.511 plant/hm2 in 2012, with a mortality rate of 0.022 7%, which achieved the control effect, reaching extremely significant level. ＂Forest land removal＋infected trees isolation＋natural enemy release＂ could extinguish the pine wilt disease. The test of isolating 24 heaps of infected pine trees showed that there were 9 heaps of pine trees extinguished the pine wilt disease, which controlled the occurrence of pine wilt disease for 100%, accounting for 37.5% of the total, in which the number of those isolated using iron netting and nylon net were 4 for each, accounting for 88.9%, and there was one heap using polypropylene net, accounting for 11.1%. The invention of em- amectin benzoate immune injection laid the foundation for extinguishing pine wilt disease. The follow checking of the effects of emamectin benzoate immune injection on pine wilt disease found that the number of dead trees caused by pine wilt dis- ease decreased significantly after injecting, and became very small in October of the next year, and the disease was completely extinguished in the third year. [Conclusionl Pine wilt disease could be controlled and extinguished with positive control by using ＂comprehensive cleaning＋industrialized removal＂, ＂comprehensive cleaning＋ natural enemy release＂, ＂comprehensive cleaning＋infected trees isolation＋natural ene- my release＂ and ＂comprehensive cleaning＋emamectin benzoate immune＂.

Design and Experimental Analysis of NLT Trussed Rafter in Yellow Pine

The roof system of social housing in Brazil generally consists of components made out of native forest lumber of high market value. Taking into account the increasing number of planted forests and the need to develop new products and to add value to this timber, this work deals with the development and structural analysis of a roof system using yellow pine plantation wood （Pinus spp）, a sustainable material which however presents many defects. The NLT （laminated nailed timber） technology was chosen as it allows the use of shorter length and smaller cross section pieces, eliminating major defects. Seven samples of structural trussed rafters in NLT were tested; six made out of graded timber and one ungraded in order to verify the impact of the wood grading in the structural performance of the model. The results showed that the trussed rafter system in NLT meets the necessary structural performance requiring poor conditions of infrastructure for manufacture process, and that the graded wood samples showed better performance than the ungraded one.

Decomposition dynamics of coarse woody debris of three important central European tree species

Background： Coarse woody debris （CWD） is an important element of forest structure that needs to be considered when managing forests for biodiversity, carbon storage or bioenergy. To manage it effectively dynamics of CWD decomposition should be known. Methods： Using a chronosequence approach, we assessed the decomposition rates of downed CWD of Fagus sylvatica, Picea obies and Pinus sylvestfis, which was sampled from three different years of tree fall and three different initial diameter classes （〉10 - ≤20 cm, 〉20 - ≤40 cm, 〉40 cm）. Samples originating from wind throws in 1999 were collected along a temperature and precipitation gradient. Based on the decay class and associated wood densities, log volumes were converted into CWD mass and C content. Log fragmentation was assessed over one year for log segments of intermediate diameters （〉20 - 40 cm） after 8 and 18 years of decomposition. Results： Significantly higher decomposition constants （k） were found in logs of F. sylvotica （0.054 year^-1） than in P. abies （0.033 year^-1） and P. sylvestris （0.032 year^-1）. However, mass loss of P. sylvestris occurred mainly in sapwood and hence k for the whole wood may be overestimated. Decomposition rates generally decreased with increasing log diameter class except for smaller dimensions in P. obies. About 74 % of the variation in mass remaining could be explained by decomposition time （27 %）, tree species （11%）, diameter （17 %）, the interactive effects between tree species and diameter （4 %） as well as between decomposition time and tree species （3 %） and a random factor （site and tree; 9.5 %）, whereas temperature explained only 2 %. Wood fragmentation may play a more important role than previously thought. Here, between 14 % and 30 % of the decomposition rates （for the first 18 years） were attributable to this process. Carbon （C） density （mgC· cm ^-3）, which was initially highest for F. sylvatico, followed by P. sylvestris and P. obies, decreased with increasing decay stage to similar values for all species. Conclusions： The apparent lack of climate effects on decomposition of logs in the field indicates that regional decomposition models for CWD may be developed on the basis of information on decomposition time, tree species and dimension only. These can then be used to predict C dynamics in CWD as input for C accounting models and for habitat management.

Microwave vacuum drying characteristics of Pinus massoniana wood

Microwave-vacuum （MV） drying characteristics of plantation Masson pine （Pinus massoniana） were studied experimentally for various levels of microwave radiation time, initial moisture content 0VIC）, vacuum level and wood thickness. The results show that the process of MV drying for wood can be significantly divided into a short accelerating rate drying period, a long constant rate drying period and falling rate drying period, and the second drying period can extend to levels of mean MC below the fiber saturation point. With the increase of initial MC and microwave radiation time, the drying rate of wood increases significantly. The vacuum level affects the drying rate in a slightly positive way. Within the range of 2 to 6 cm, the effects of sample thickness on the drying rate can be negligible.

Relations Between Permeability and Structure of Wood

The permeability and the structure of heartwood and sapwood of the solvent-exchange dried and the air-dried greenwood of Chinese-fir (Cunninghamia lanceolata (Lamb.) Hook.) and masson pine (Pinus massoniana Lamb.) were measured in order to study the relations between the permeability and the structure. The results showed that the permeability of sapwood of both the air-dried and the solvent-exchange dried wood was higher than that of heartwood, and the permeability of the solvent-exchanged dried heartwood and sapwood was higher than that of the air-dried. A higher permeability of wood was attributed to, on the one hand, a bigger number of flow path per unit area of the wood perpendicular to the flow direction resulted from a bigger number of unaspirated pits per unit area and a bigger number of effective pit openings per membrane, and on the other hand, a smaller number of tracheid in series connection per unit length parallel to flow direction resulted from a longer tracheid length and an effective tracheid length for permeability.

灰葡萄孢寄生菌Clpse01的杀线活性研究

在用灰葡萄孢菌Botrytis cinerea培养松材线虫的过程中,发掘了一株具有杀线活性的灰葡萄孢寄生菌Clpse01。本文在光学显微镜下对菌株Clpse01的形态和其对灰葡萄孢菌的生长影响进行了观察;采用ITS4/ITS5、LR5/LR0R、Bt2a/Bt2b和EF1-688F/EF1-1251R引物进行了分子生物学鉴定;同时测试了菌株Clpse01对松材线虫的杀线活性及对松材线虫卵孵化能力和繁殖能力的影响;最后测试了菌株Clpse01的胞外蛋白浓度,胞外β-葡萄糖苷酶活性和胞外几丁质酶活性。根据形态学和分子生物学结果,将菌株Clpse01鉴定为假卡鲁卡枝惠霉Clonostachyspseudochroleuca。菌株Clpse01可以缠绕、侵入灰葡萄孢菌的菌丝以获得营养来源,使灰葡萄孢菌的菌丝生长受到抑制。将2000条松材线虫接种到长满菌株Clpse01的培养基上,8 d后仅分离出6条/皿活线虫,而对照灰葡萄孢菌培养基上分离的线虫数为33066条/皿活线虫;菌株Clpse01发酵液处理松材线虫48 h后的校正死亡率为88%,浓度为1×108孢子/mL的孢子悬液处理松材线虫24 h后的校正死亡率为88.33%;菌株Clpse01 2×稀释发酵液24 h对卵的孵化抑制率为100%。发酵培养6 h后,菌株Clpse01胞外蛋白浓度为1782.917μg/mL,胞外β-葡萄糖苷酶为9.99 U/mL,胞外几丁质酶含量为0.8792U/mL,并随发酵时间推移而升高。菌株Clpse01通过寄生松材线虫的食物来源灰葡萄孢菌和影响松材线虫的繁殖、存活和卵的孵化起作用,胞外β-葡萄糖苷酶、几丁质酶是毒杀松材线虫的两个重要生理因子。

2%甲维盐乳油对松材线虫病的防效测定

[目的]为测试2%甲维盐乳油(商品名:松高飞)对松材线虫病的防治效果。[方法]首先通过室内浸渍法比较了2%甲维盐乳油和2%甲维盐微乳剂(商品名:林源松韵)的杀线活性,然后在温室和林间通过树干注射测试了2%甲维盐乳油对松材线虫病的防治效果,最后通过高效液相色谱法测定了不同时间、不同松树体内甲维盐的含量变化。[结果]室内浸渍法结果显示,2%甲维盐乳油具有更强的杀线活性,LC_(50)为41.808 mg·L^(-1),显著低于2%甲维盐微乳剂的75.959 mg·L^(-1)(p<0.05)。温室预防组结果显示,2%甲维盐乳油的预防效果显著,2 a后松树无死亡。温室治疗组结果显示,2%甲维盐乳油治疗时间越早,治疗效果越好;2 a后,接种线虫后7 d注药治疗组,松树无死亡;而30 d后注药治疗组,白皮松、无死亡,油松死亡率为20%,华山松死亡率为40%。林间的试验显示2%甲维盐乳油在两块林地的防治效果显著,其试验组马尾松林2 a累计死亡率分别为2%和5%,远低于对照组马尾松死亡率20%和25%。随着时间变化,不同松树体内甲维盐变化有所差异,华山松体内平均甲维盐含量最高(36.59 mg·kg^(-1)),油松最低(27.11 mg·kg^(-1))。注射后15 d内,所有松树体内甲维盐含量均上升;15 d后,华山松树干中部甲维盐含量逐渐升高,60 d的含量最高;而油松、白皮松树干内甲维盐含量逐渐降低并趋平。[结论]2%甲维盐乳油对松材线虫具有显著的杀线活性,温室和林间防治效果显著,在不同松树体内传输和存留效果良好,无明显药害,可以进一步推广使用。

抗松材线虫病马尾松种质资源遗传多样性分析及核心种质构建

【目的】对来自安徽省林业科学研究院和异地保存在浙江省临海市林业技术推广和场圃旅游服务总站的114份抗松材线虫Bursaphelenchus xylophilus病马尾松Pinus massoniana种质进行遗传多样性与群体结构分析,构建抗性马尾松核心种质库。【方法】对114份抗性马尾松种质进行检测,使用分子生物学软件计算遗传多样性参数,并进行主坐标(PCoA)和群体结构分析。利用M策略和随机取样策略分别构建核心种质,分析不同核心种质的的遗传多样性参数,确定最适合的构建方法。【结果】114份抗性马尾松种质共检测到115个等位基因,平均有效等位基因数(N_(e))为5.54,平均Shannon’s多样性指数(I)为1.51,平均多态信息含量(P_(IC))为0.90,结果表明其具有较高的遗传多样性水平。群体结构分析将114份抗性马尾松种质分为4个亚群,主坐标分析结果与上述基本一致。根据遗传多样性参数和抽样数量综合考虑,M策略构建的核心种质能以最小的种质数保留原有种质最大的遗传多样性,为最佳的取样策略。利用该策略得到了72份核心种质,其保留了原有种质100%的等位基因数,N_(e)、I、期望杂合度(H_(e))、PIC等遗传参数的保留率分别为95.67%、94.96%、98.12%和100.00%,将构建的核心种质与原有种质进行t检验、PCoA分析和UPGMA聚类分析,结果表明两者间的遗传多样性无显著差异。【结论】114份抗性马尾松种质遗传多样性水平较高,构建的72份抗性马尾松核心种质,去除了遗传冗余,有利于抗性马尾松种质资源的有效保护和科学利用,可为优异基因发掘和新品种选育提供参考。

北美黄杉和云杉-松木-冷杉平行弦木桁架承载性能比较

【目的】对比不同腹杆角度下北美黄杉和云杉-松木-冷杉(SPF)华伦式平行弦木桁架的承载性能,探究腹杆角度和结构用材对华伦式平行弦木桁架承载性能的影响规律,为平行弦木桁架结构设计提供理论依据。【方法】以承载力和稳定性为验算指标,利用Smsolver结构力学求解器对平行弦木桁架各杆件的内力变化及其变形情况进行定量分析,得到平行弦木桁架腹杆角度的上、下临界角度和最优腹杆角度;采用ABAQUS有限元软件对3种腹杆角度的北美黄杉和SPF平行弦木桁架进行有限元模型分析与验证,获得不同基材平行弦木桁架在不同腹杆角度情况下的内力变化规律,判断其可能的破坏形式和受力机理;以SPF和北美黄杉为基材分别制作3种腹杆角度的平行弦木桁架,进行抗弯承载性能静力试验,探究平行弦木桁架的极限荷载、应力分布及主要破坏形式,并与有限元模拟结果进行对比,验证平行弦木桁架有限元模型分析的准确性和适用性。【结果】1)华伦式平行弦木桁架的最优腹杆角度为47°,下临界角度为34°,上临界角度为60°;2)北美黄杉平行弦木桁架的极限荷载范围为26.53~40.83 kN,跨中挠度范围为30.57~31.01 mm,SPF平行弦木桁架的极限荷载范围为23.48~34.16 kN,跨中挠度范围为31.85~32.05 mm;3)腹杆角度34°、47°、60°的北美黄杉和SPF平行弦木桁架极限荷载分别为26.53和23.48 kN、35.10和30.06 kN、40.83和34.16 kN,对应跨中挠度分别为31.85和31.01 mm、30.72和32.05 mm、30.57和31.97 mm;4)北美黄杉平行弦木桁架的破坏形式主要表现为靠近桁架支座处的腹杆出现裂纹以及桁架端部或荷载施加点处齿板拔出,SPF平行弦木桁架的破坏形式主要表现为桁架端部和荷载施加点处齿板拔出;5)ABAQUS有限元模拟和试验验证发现,2种平行弦木桁架跨中处弦杆轴力最大,往两边逐次递减,桁架跨中处腹杆轴力最小,往两边逐次递增,且弦杆轴力大于腹杆。【结论】北美黄杉平行弦木桁架承载性能优于SPF平行弦木桁架;平行弦木桁架的承载性能随腹杆角度增加而增加;2种平行弦木桁架的薄弱点均为桁架端部和荷载施加点处的齿板连接节点;ABAQUS有限元模型能有效反映出平行弦木桁架受力分布和整体结构变形趋势。

木醋液对4种蔬菜种子萌发的影响

目的:探究松木屑木醋液对蔬菜作物的化感效应,以期为松木屑木醋液合理种植蔬菜作物提供理论依据。方法:研究不同浓度木醋液对萝卜、韭菜、小白菜和芥菜种子萌发和幼苗生长的化感效应。结果:木醋液对4种蔬菜种子萌发和幼苗生长的最佳浓度及化感促进作用不同,2 000倍稀释木醋液处理下,与对照组相比萝卜种子的发芽率、发芽指数和根长及小白菜种子的根长分别提高了20.00%、22.60%、5.90%、19.50%(P <0.05);500倍稀释木醋液处理下,与对照组相比韭菜种子的发芽率和茎长分别提高了8.89%、30.60%(P <0.05);1 000倍稀释木醋液处理下,与对照组相比芥菜种子的发芽率、活力指数和茎长分别提高了8.00%、31.33%、46.70%(P <0.05)。结论:低浓度松木屑木醋液具有促进4种蔬菜作物种子生长的化感作用。