Comparative study on the chloroplast genomes of five Larix species from the Qinghai-Tibet Plateau and the screening of candidate DNA markers

Five Larix species(L.griffithii,L.speciose,L.himalaica,L.kongboensis,and L.potaninii var.australis),have survived on the Qinghai-Tibet Plateau(QTP)under specific climate conditions for decades.The lack of genomic information seriously hinders research on the evolution,conservation and ecology of these Larix resources.In this study,complete chloroplast(cp)genomes of the 5 species were assembled and compared based on next generation sequencing technology combined with polymerase chain reaction validation.The results show that the 5 cp genomes are relatively conservative in size,gene content and arrangement,and border variation.Phylogenetic analysis showed that the species are closely related as well as to seven other species of the same genus.In addition,the 5 cp genomes contained few simple sequence repeats and relatively low nucleotide variability;thus,12 candidate polymorphic cp DNA markers will be helpful for further research on relevant population genetics.These results will provide valuable genetic information for the conservation,evolution and ecology of these species and their relatives.

Species richness patterns and the determinants of larch forests in China

Larch forests are important for species diversity,as well as soil and water conservation in mountain regions.In this study,we determined large-scale patterns of species richness in larch forests and identified the factors that drive these patterns.We found that larch forest species richness was high in southern China and low in northern China,and that patterns of species richness along an elevational gradient depend on larch forest type.In addition,we found that patterns of species richness in larch forests are best explained by contemporary climatic factors.Specifically,mean annual temperature and annual potential evapotranspiration were the most important factors for species richness of tree and shrub layers,while mean temperature of the coldest quarter and anomaly of annual precipitation from the Last Glacial Maximum to the present were the most important for that of herb layer and the whole community.Community structural factors,especially stand density,are also associated with the species richness of larch forests.Our findings that species richness in China's larch forests is mainly affected by energy availability and cold conditions support the ambient energy hypothesis and the freezing tolerance hypothesis.

Effects of deforestation on microbial diversity in a Siberian larch(Larix sibirica) stand in Mongolia

For evaluating microbial community changes in a Siberian larch stand disturbed by forest fire or clearcutting,357 clones were randomly selected and sequenced using a culture-independent approach and 16S rRNA sequencing to characterize the bacterial composition and diversity from the different disturbed Siberian larch stands.Interestingly,the burned larch stand had an increase in the relative amounts of b-proteobacteria and Firmicutes and a decrease in Acidobacteria,while Gemmatimonadetes increased Verrucomicrobia decreased in the harvested larch stand.Microbial diversity and richness were higher in the undisturbed larch stand than the disturbed(burned or clear-cut)larch stands,and the influence of clear-cutting was more negative than that of the forest fire.This study indicates that evaluating the microbial diversity of undisturbed,burned,and clear-cutting Siberian larch stands provides information about the impact of forest disturbances on soil microbial communities,which may be helpful for understanding and evaluating soil health and devising reafforestation strategies for larch.

Life forms affect beta-diversity patterns of larch forests in China

Beta-diversity reflects the spatial changes in community species composition which helps to understand how communities are assembled and biodiversity is formed and maintained. Larch(Larix) forests, which are coniferous forests widely distributed in the mountainous and plateau areas in North and Southwest China, are critical for maintaining the environmental conditions and species diversity. Few studies of larch forests have examined the beta-diversity and its constituent components(species turnover and nestedness-resultant components). Here, we used 483 larch forest plots to determine the total betadiversity and its components in different life forms(i.e., tree, shrub, and herb) of larch forests in China and to evaluate the main drivers that underlie this beta-diversity. We found that total betadiversity of larch forests was mainly dependent on the species turnover component. In all life forms,total beta-diversity and the species turnover component increased with increasing geographic, elevational, current climatic, and paleoclimatic distances. In contrast, the nestedness-resultant component decreased across these same distances. Geographic and environmental factors explained 20%-25% of total beta-diversity, 18%-27% of species turnover component, and 4%-16% of nestedness-resultant component. Larch forest types significantly affected total beta-diversity and species turnover component. Taken together, our results indicate that life forms affect beta-diversity patterns of larch forests in China, and that beta-diversity is driven by both niche differentiation and dispersal limitation. Our findings help to greatly understand the mechanisms of community assemblies of larch forests in China.

Forest Fairy Ring Fungi <i>Clitocybe nebularis</i>, Soil <i>Bacillus</i>spp., and Plant Extracts Exhibit <i>in Vitro</i>Antagonism on Dieback <i>Phytophthora</i>Species

In vitro Kirby-Bauer disc-diffusion assays coupled with bio-imaging software techniques were used to assess native forest dwelling “fairy ring” forming fungi (Clitocybe nebularis) and co-habitant forest tree-root colonising non pathogenic, antibiotic producing bacteria (Bacillus licheniformis, Bacillus pumilis) for their antagonism towards Japanese larch dieback oomycetes phytopathogens which also affects ornamental alternative hosts. The aqueous extracts of C. nebularis exhibited the highest clearance (inhibitory) zone of 21.4 × 105 pixels = 573%) against Phytophthora ramorum than growth/clear zone Cartesian integrates recorded in untreated (control) disc (3.7 × 105 pixels = 100%) over 3-day incubation. The fairy ring fungal extracts also exhibited substantive antagonism against P. kernoviae (147%), P. lateralis (347%) and a solanaceous crop infecting P. infestans (86%). Quite encouragingly, the soil oomycete phytopathogen P. ramorum was inhibited strongly (mean ~ 177%) by both forest bacilli. Aqueous extracts of non-forest antifungal herbaceous plants (garlic and elderberry) expressed similar inhibitory effects (mean ~ 70%). A seaweed fungal elicitor component fucoidan showed moderate levels (mean ~ 85%) of antagonism against P. ramorum, P. kernoviae, P. lateralis and P. infestans. The results in this in vitro study highlight the intensity and vigor of antagonistic forest microflora and non-forest herbaceous antifungal agents such as garlic and other plant extracts as serious candidates for suppression of the oomycete Phytophthora pathogenic fungi in forest soils. This study calls for urgent scoping and impact assessment studies in pot experiments and mini-plot forest trials to gauge the fitness of these natural resources for field level potential biotechnological applications to combat the devastating dieback disease in the native woodlands and horticulture.

Changing regularity of plant and insect community characteristics due to pest outbreaks in Larix principis- rupprechtii plantations

Research has indicated that simple forest eco-system composition,structure and diversity have uncompli-cated community relationships and insufficient pest control capabilities.To investigate changing characteristics of plant and insect communities in under pest outbreaks in Larix principis-rupprechtii plantations,the research areas were defined as mature(48–50 years)and young(24–29 years)infested stands along with healthy stands.The results show a reduction in the complexity and diversity of plant communi-ties and herbaceous plant guilds(polycultures of beneficial plants)and the complexity and dominance of insect com-munities,especially natural insect enemies.The results also show the relative simplicity of the main factors of commu-nity change and development that represent the characteris-tics of pest outbreaks in L.principis-rupprechtii plantations.The complexity and diversity of plant communities,particu-larly herbaceous plant guilds play a fundamental role in the regulation and development in forest ecosystems.

Carbon fluxes and their response to environmental variables in a Dahurian larch forest ecosystem in northeast China

The Dahurian larch forest in northeast China is important due to its vastness and location within a transitional zone from boreal to temperate and at the southern distribution edge of the vast Siberian larch forest. The continuous carbon fluxes were measured from May 2004 to April 2005 in the Dahurian larch forest in Northeast China using an eddy covariance method. The results showed that the ecosystem released carbon in the dormant season from mid-October 2004 to April 2005, while it assimilated CO2 from the atmosphere in the growing season from May to September 2004. The net carbon sequestration reached its peak of 112 g.m^-2.month ^-1 in June 2004 （simplified expression of g （carbon）.m^-2.month^-1） and then gradually decreased. Annually, the larch forest was a carbon sink that sequestered carbon of 146 g-m^-2.a^-1 （simplified expression of g （carbon）.m^-2.a^-1） during the measurements. The photosynthetic process of the larch forest ecosystem was largely affected by the vapor pressure deficit （VPD） and temperature. Under humid conditions （VPD 〈 1.0 kPa）, the gross ecosystem production （GEP） increased with increasing temperature. But the net ecosystem production （NEP） showed almost no change with increasing temperature because the increment of GEP was counterbalanced by that of the ecosystem respiration. Under a dry environment （VPD 〉 1.0 kPa）, the GEP decreased with the increasing VPD at a rate of 3.0 μmol.m^-2.s^-1kPa -1 and the ecosystem respiration was also enhanced simultaneously due to the increase of air temperature, which was linearly correlated with the VPD. As a result, the net ecosystem carbon sequestration rapidly decreased with the increasing VPD at a rate of 5.2 μmol.m^-2.s-1.kPa^-1. Under humid conditions （VPD 〈 1.0 kPa）, both the GEP and NEP were obviously restricted by the low air temperature but were insensitive to the high temperature because the observed high temperature value comes within the category of the optimum range.

Effect of TMS(nanostructured silicon dioxide) on growth of Changbai larch seedlings

The roots of 200 one-year-old Changbai Larch (Larix olgensis) seedlings were soaked for 6 hours at the TMS concentrations of 2000, 1000, 500, 250, 125, and 62 μL·L?1. Mean seedling height, root collar diameter, main root length and number of lateral roots were measured every 15 days during growing season from May 30 to Oct. 20. Experimental results showed that TMS treatments greatly promoted seedling growth and improved seedling quality. The treatment by 500 μL·L?1 TMS produced the best result, for which the mean height, root collar diameter, main root length, and the number of lateral roots of seedlings were increased by 42.5%, 30.7%, 14.0%, and 31.6%, respectively, compared to that of the control seedlings. As to seedling quality, grade-I seedling and grade-II seedlings were fifty-fifty, and no grade-III seedlings was found. The treatment by 500 μL·L?1 TMS resulted in the highest chlorophyll concentration. Keywords Changbai Larch - Larix olgensis - Seedling production - Nanostructured silicon dioxide CLC number S143.8 Document code B Foundation item: This study is supported by Jilin Forestry Group Co.Biography: LIN Baoshan (1955-), male, Associate professor at the college of forestry, Beihua University, Jilin City 132011, Jilin Province, P.R China.Responsible editor: Chai Ruihai.

Spatial distribution of fine roots of larch and ash in the mixed plantation stand

The spatial distribution of standing fine roots in tree rows of different species in a 12-year-old mixed stand of ash (Fraxinus mandshurica Rupr.) and larch (Larix olgensis Henry) was studied by soil core sampling in early spring, 2001. It is found that ash and larch differ greatly in their belowground biomass distribution. Ash has much higher fine root biomass density in the soil than larch at stand level (with the max value of 4442.3 vs. 2234.9 gm-3). Both tree species deployed more fine roots in their neighboring zone, suggesting a less intensive competition between roots of the two species. Both fine root biomass density and root length density of ash in the zone between larch tree rows are greater than that of larch in zone between ash tree rows, indicating that ash is more powerful than larch in belowground competition. The spatial distribution feature of roots favors the growth of ash in the mixed stand.

Growth and yield models for Dahurian larch plantations

Several equations were selected using nonlinear regression analysis for setting up growth and yield modehe of Dahurian larch (Laris gmelinii Rupr.) plantations. Data of 405 stem analysis trees were collected from 336 temporary plots throughout the Daxing’an Mountains. Results showed that the Richards equation was the best model for estimating tree height, stand mean height and stand dominant height by age, the Power equation was the fdiest model for predicting tree volume by DBH and tree height, and the Logarithmic stand vofume equation was good for predicting stand volume from age, mean height. basal area and other stand variables. These models can be used to construct volume tabIes, site index table and other forestry tables for Dahurian ghantations.

GROWTH EFFECT OF DAHURIAN LARCH-MANCHURIAN ASH MIXED FORESTS

With the method of stem analyses by the microscope, the xylem’s accumulations atdifferent ages were quantitatively studied using the data of typical plant association for Dahurianlarch (Larix gmelini Rupr) and Manchurian ash (Fraxinus mandshurica Rupr) mixed forests. Thedeveloping process for this important mixed forest type in the study area was systematically established. The result showed that in the artificial stand of Dahurian larch mixed with naturalManchurian ash. only those which have the same origin as Dahurian larch can grow up before theclosing of stand and form the components of the main layers. After 24 years seif-thinning, when theywere 29 years old, Dahurian larch would be at the stage of no self-thinning. At last the stand woulddevelop to the broad-leaved forests dominating with the Manchurian ash.

Quantitative dynamics on stimulating regeneration and sowing seedlings of Larix gmelinii in Daxing'an Mountains

To understand the quantitative dynamics and death reason of stimulating regeneration seedlings is significant for stimulating the natural regeneration ofLarix gmelinii and implement of conservation project of natural forest. This paper summarized location observations and directly-seeding simulation experiments of six permanent sample plots that were set up after the seed bumper harvest year ofLarix gmelinii in 1989. The study showed that stimulating natural regeneration seedlings had a large mortality in the first three years, especially in the first year of seedling emergence. After three years seedlings died less and stepped into the stable regeneration stage. A large number of seedlings died of sunscald as the primary death reason. For those areas of good site conditions and rich soil, damping-off would cause seedlings to death in large quantities. The task of stimulating regeneration is mainly to get rid of the litter (forest floor) on burned areas. By means of promoting measures, emergence rate of sown seeds would be several times and dozens of times higher than that of seed shedding on the condition of retention of forest floor. Promoting the regeneration need to select the suitable site against great slope and low-lying lands; at the same time, be careful of the avoidance of frost heaving by depression water.

Scale correlation between vegetation and soil in larch forest, NE China

After the analysis on the linages of species, the fractal dimensions of vegetation and soil in a managed larch(Larix gmelini) forest in Daxingan Mountains, NE China were estimated separately, and their scale correlation was discussed. (1) The dominant species of the larch forest, larch and the important accompany species, birch (Betula platyphylla) were homogeneously distributed along the transect. The other species were heterogeneous, and can be divided into three groups located on the right, left and central parts of the transect respectively. The transect can be separated into two parts at the position for the 29th quadrat(580m). (2) The fractal dimension in the large scale range from 200 to 400m was lower than that in the small scale range from 0 to 200m in the forest, indicating the different variation regularities of spatial heterogeneity in different scale ranges. The inflection point at 200m was one of the key scales of spatial hierarchy of the larch forest. (3) The scale variation of the forest was correlated with that of soil pH on large scales, which reflected the indirect control of the dominant species to the spatial pattern and species distribution of understorey by changing soil acidity in the forest and the indirect effects of forest management.

COMPARISON OF FOUR COMMUNITY STRUCTURE TYPES FOR DAHURIAN LARCH PLANTATIONS

Community properties of dahurian larch (Larix gmelini) plantations at the Experimental Station of Laoshan were studied. Results show that under the different distributions of the combines of tree layer of dahurian larch plantations, stands have different community structure characteristics and biological productivities. From the result of the analysis of variance, it shows that there is the obvious difference among biomass of understory, herb layer and litter for four structure tpps.

STUDIES ON BIOMASS AND PRODUCTIVITY FOR DAHUIAN LARCH PLANTATIONS

The biornass and productivity for dahurian larch (Larix gmelini) plantations of four structure types were measured. The biomass of trees, understory' herb and litter was surveyed using methods of average standard tree and subsample yield respectively.The estimated total mean biomass for dahurian larch plantation communities of four structure types was 159. 445 t/hm2 and the net productivity was 12. 237 t/hm2. a.

大兴安岭不同演替阶段天然林物种多度格局模拟

为实现大兴安岭地区落叶松天然林的全周期可持续经营,以新林林业局翠岗林场3块100m×100m不同演替阶段(白桦林、落叶松-白桦混交林和落叶松林)的天然林固定调查样地数据为基础,采用统计模型(对数正态模型)、生态位模型(断棍模型、生态位优先占领模型、Zipf模型、Zipf-Mandelbrot模型)和中性模型(群落零和多项式模型、Volkov模型)对不同演替阶段天然林的乔木层、幼苗层和由乔木层划分的不同林层的物种多度格局进行拟合,并用χ~2检验和Kolmogorov-Smirnov检验选择最佳模型。结果表明:(1)在大兴安岭地区不同演替阶段的落叶松天然林群落中,Zipf-Mandelbrot模型的拟合效果均最好。(2)对数正态模型对于稳定的演替阶段白桦林和落叶松林的群落相较于过渡阶段群落落叶松-白桦混交林的物种多度分布的拟合效果更好。(3)在大兴安岭地区落叶松天然林中,生境过滤主导群落构建,随着群落不断演替生境过滤和中性过程减弱。(4)天然林群落乔木层的群落构建过程与乔木层内不同生长阶段林层的构建过程不同,生境过滤过程在落叶松林乔木层中逐渐减弱,而在落叶松林不同生长阶段的林层和更新层中增强。

兴安落叶松天然林3个主要树种单木断面积生长模型

【目的】构建兴安落叶松Larix gmelinii天然林3个主要树种组的断面积生长混合效应模型,提高断面积生长模型的预估精度,为兴安落叶松天然林的林分生长动态研究提供理论参考。【方法】以大兴安岭林区兴安落叶松天然林的主要树种组(兴安落叶松、白桦、栎类)为研究对象,采用4期森林资源连续清查的626块复测样地数据,首先使用多元逐步回归方法建立单木断面积生长模型,其次在最优基础模型的基础上,引入样地随机效应,建立单木断面积生长混合效应模型,最后对模型进行检验。【结果】期初胸径(D)的倒数(1/D)、每公顷株数(N)、大于对象木的胸高断面积和(B_(L))、对象木胸径与林分算数平均胸径之比(B_(L)/D)、海拔(E)以及坡度和坡向的组合(T_(c))对兴安落叶松天然林单木断面积的生长有显著影响(P<0.05)。考虑样地随机效应的混合效应模型的赤池信息准则(AIC)、贝叶斯信息准则(BIC)明显降低,对数似然值(LogLik)明显增大。引入异方差函数和自相关结构后,提高了混合效应模型预估的精度;混合效应模型的平均绝对误差(Bias)和均方根误差(RMSE)均比基础模型的低,兴安落叶松、白桦、栎类最优混合效应模型的R^(2)分别由0.435提高到0.658、由0.354提高到0.489、由0.307提高到0.379。【结论】与基础模型相比,考虑层次结构的混合效应模型能显著地改善模型的拟合效果,为内蒙古大兴安岭地区兴安落叶松天然林的林分生长动态预测提供了具有生物学意义和统计学可靠性的断面积生长模型。

落叶松枯梢病生防菌的筛选、鉴定及其生物学特性

[目的]为获得落叶松枯梢病的生防菌。[方法]通过对峙实验和发酵液复筛,筛选获得对落叶松枯梢病菌(Neofusicoccum laricinum)具有较强抑制效果的菌株,对筛选得到的菌株进行鉴定,并对其生物学特性展开研究。[结果]筛选得到1株对落叶松枯梢病病原菌有显著拮抗作用的土壤真菌T2,结合形态学以及分子生物学鉴定为钩状木霉(Trichoderma hamatum)。其平板对峙抑菌率达到74.16%,发酵液的抑菌率达到91.29%。发酵液对多种植物病原真菌均具有较强的抑菌作用,对松球壳孢菌、金黄壳囊孢菌、杨灰星叶点霉和立枯丝核菌表现出强抑制作用,抑菌率均为92.00%,对拟枝孢镰刀菌和杨生褐盘二孢菌的抑菌效果较好,分别为79.67%和62.67%。T2能利用多种碳氮源、有广泛的酸碱度适应能力及较高的致死温度。[结论]通过筛选得到的钩状木霉T2对落叶松枯梢病病原菌的拮抗作用显著,抑菌谱广,环境适应力强。本研究可为落叶松枯梢病的防治提供理论研究和基础。

华北落叶松混交林林下植物群落特征对间伐的响应

为探究提高华北落叶松混交林生物多样性的抚育措施,通过对北京市京西林场对照区(Ⅰ)、弱度间伐(Ⅱ)、中度间伐(Ⅲ)和强度间伐(Ⅳ)4种间伐强度下的华北落叶松混交林林下植物群落调查和监测,分析其林下植被变化特征。结果表明,4种间伐强度下,林下灌木种类分别为5、7、7、6种,草本种类分别为11、11、10、12种,共有物种包括山楂叶悬钩子、榛、绣线菊、溲疏、野青茅、苔草和假还阳参;随着林分郁闭度减小,灌木和草本数量增加,中度抚育强度样地(Ⅲ)中灌木数量最多,强度间伐样地(Ⅳ)中草本数量最多;随着间伐强度增加,喜光灌木如六道木、接骨木、连翘增多,凸显阳光对植被影响;不同抚育强度下灌木和草本植被重要值排序不同;灌木层中,绣线菊、牛叠肚在4种间伐强度样地中重要值均排前三,荆条仅在对照区(Ⅰ)中重要值排前三,连翘仅在强度间伐样地(Ⅳ)中重要值排前三,草本层中,野青茅在弱度、中度间伐强度均重要值排前三,尤其在强度间伐样地(Ⅳ)中,重要值达到37.16;物种多样性、群落相似性和林下物种多样性评估表明,不同抚育强度影响物种组成和多样性,高强度间伐有助于提高多样性,尤其是在草本层。研究结果为优化华北落叶松混交林抚育策略以提升生物多样性的保护效果提供重要参考。

不同经营方法对秦岭华北落叶松林分生长和林下植被的影响

【目的】探讨不同经营方法对秦岭华北落叶松林分生长和林下植被的影响,以期提高生态系统生产力,优化该地区华北落叶松人工林经营技术,为实现森林可持续经营提供理论和实践依据。【方法】以西北农林科技大学教学实验林场平河梁华北落叶松人工林为研究对象,根据近自然经营指导下的抚育间伐技术措施,设置间伐处理(T1,间伐强度20%)和林窗处理(T2,只留下少许保留木,伐出其他乔木,形成32 m×32 m的方形林窗),以未经营样地为对照(CK),间伐和林窗经营7年后,调查不同经营方法对人工林林分生长及林下植被更新和生长的影响。【结果】间伐后的林木平均胸径、单株材积、总蓄积量均显著高于对照组,但树高变化较小;间伐和林窗处理下的林下幼苗生长发育与对照组均存在显著差异(P<0.05);间伐处理中,华山松和云杉幼苗的成活率较高,但人工补植的红桦幼苗全部死亡;间伐和林窗处理既促进了人工补植幼苗生长,又促进了幼苗天然更新;间伐和林窗处理后林下灌草的物种多样性显著提高;间伐和林窗处理后林下灌草的种类和盖度提高,物种丰富度也显著增加,以间伐处理效果最佳;对照样地和经营后样地之间共有植物种少,而间伐处理和林窗处理之间共有种较多,相似性系数高。【结论】间伐和林窗2种经营方法对华北落叶松人工林生长均有促进作用,间伐经营对华北落叶松人工林生长和幼苗更新的促进效果更为明显,灌草的物种多样性也在间伐后显著提高,在秦岭其他区域的华北落叶松人工林中采用间伐经营更加合理。