Family selection and evaluation of Larix gmelinii var.principis-rupprechtii(Mayr.)Pilger based on stem analysis data at multiple sites

Larix gmelinii var.principis-rupprechtii(Mayr.)Pilger is an important native tree species in North China with advantages of fast growth,straight trunk,and good wood properties.The multi-year and multi-site breeding research of families of the species has not been reported previously.Based on diameter at breast height(DBH),height and volume of 25 families on four experimental sites,we calculated variance components,genetic parameters,juvenile and mature trait correlations and made genotype main effect plus genotype×environment interaction effect(GGE)biplot based on the breeding values estimated using the method of best linear unbiased prediction(BLUP).Compared with height,DBH and volume had higher heritability and larger variation coefficients,making them the more suitable traits for family selection and evaluation.Based on these,GGE biplots containing 20 combinations of site×age were drawn using data at 13 to 17 years when the interactions between family and location were strong.Test sites classifications based on DBH,and volume were inconsistent,with two categories for DBH and one for volume.The Guyuan site was the most suitable with strong discriminating ability,high representativeness and stability among tree ages.Integrating the ranking results of DBH and volume,families 66,76,82 and 111 were high-yielding and stable,families 78 and96 were high-yielding with above average stability,families72 and 79 were high-yielding with below average stability,whereas stability of family 100 was inconsistent between DBH and volume.Early selection based on DBH was convenient and reliable,and can be made at seven years.This study provides support for the selection of Larix gmelinii var.principis-rupprechtii families in Hebei province and an example for the application of stem analysis data from multiple sites in tree breeding.

兴安落叶松(Larix gmelinii Rupr.)叶片养分的空间分布格局

对中国东北温带森林生态系统主要树种兴安落叶松(Larix gmelinii Rupr.)24个采样点72个叶片样品有机碳(C)、全氮(N)、全磷(P)和全钾(K)的化学组成、地理分布格局及其与气候因子的关系进行了研究。结果表明,叶片C、N、P和K含量的几何平均数分别为543.970、16.902、2.373mg/g和14.625mg/g,且叶片的C含量>N含量>K含量>P含量;叶片的C/N、C/P和N/P分别为32.183、229.226和7.123。随纬度的增加、年均温度和年均降雨量的降低,兴安落叶松叶片C、N含量和N/P显著降低,叶片C/N和K含量显著升高,叶片P含量和C/P的变化没有达到显著水平。叶片N含量随纬度与年均温度的变化与全球及其它大尺度的研究结果相反,而N/P与其一致,这与在该区域的其它物种的研究结果基本一致。这可能是由于在本研究区域北部寒温带越往高纬度地区年均温度和年均降雨量越低、生长季越短,因此成土作用弱导致植物可以吸收利用的养分越少,但是由于植物显著降低的N含量和变化不明显的P含量导致了叶片N/P随纬度的增加和年均温度和年均降雨量的降低而降低,这与全球尺度的研究结果一致。兴安落叶松叶片养分分布格局与全球尺度和中国区域研究结果的差异说明了加强区域叶片养分特征研究的重要性。叶片养分与气候因子的显著线性相关说明气候因子是影响叶片养分特征的一个主要因子。

剪叶损伤与昆虫取食对兴安落叶松(Larix gmelinii)针叶中缩合单宁诱导作用的差异

单宁是植物内与抗虫性相关的重要次生代谢物质。为了研究昆虫取食及剪叶诱导对兴安落叶松（Larix gmelinii）针叶内缩合单宁含量的影响，用剪叶法和落叶松毛虫（Dendrolimus superans）幼虫取食处理5年生兴安落叶松苗，以香草醛．盐酸法测定其剩余健康针叶内缩合单宁含量的变化。结果表明：（1）处理后1～10d，剪叶4枝75％，8枝50％、75％，12枝25％、50％、75％及虫伤4枝75％的兴安落叶松健康针叶内的缩合单宁含量均明显高于对照（P〈0．01），15d时，剪叶8枝75％，12枝50％的兴安落叶松针叶内的缩合单宁含量仍高于对照（P〈0．05），说明剪叶与虫伤处理均能诱导缩合单宁含量增加。（2）剪叶4枝75％，8枝50％，12枝25％、75％的处理之间，诱导的缩合单宁含量差异不显著（P〉0．05）。剪叶8枝75％，12枝50％诱导缩合单宁含量增加幅度比其它剪叶处理大，且诱导持续时间长。说明剪叶程度虽能影响缩合单宁含量，但二者并不呈线性关系。（3）剪叶4枝75％在5d时诱导缩合单宁含量最高，虫伤4枝75％在10d时诱导缩合单宁含量最高，说明剪叶诱导的缩合单宁含量高峰早于虫伤处理。但处理后1-10d，剪叶及虫伤4枝75％的落叶松针叶内缩合单宁含量均明显高于对照（P〈0．01或P〈0．05），之后与对照差异不显著（P〉0．05），说明在受到诱导处理后，兴安落叶松产生应激反应，使其针叶内缩合单宁含量在一定时间内先增加，后逐渐恢复到正常水平。由上可见，可以采取适当的损伤处理取得与昆虫取食相似的兴安落叶松抗性反应。

林床清理对落叶松(Larix gmelinii)人工林土壤呼吸和物理性质的影响

林下可再生生物质资源的利用是当今森林资源利用的热点,通过林床清理可以获得廉价可再生生物质资源,但其对林分土壤碳收支的影响尚不清楚。运用红外气体分析法(IRGA法)连续两年观测了林床清理对落叶松(Larix gmelinii)人工林土壤呼吸及物理性质的影响,并估算了林床清理生物质资源利用对落叶松人工林碳收支的影响。结果表明:林床清理能够降低落叶松人工林的土壤呼吸,2a的平均值由2.20μmol·m-2s-1降低到1.18μmol·m-2s-1,平均降低幅度1.02μmo·lm-2s-1,年呼吸总量由41.2mol·m-2a-1降至22.4mol·m-2a-1,而且,使土壤呼吸Q10值从2.33降低到2.22,R0值从0.61μmol·m-2s-1降至0.36μmo·lm-2s-1;林床清理能够使林床土壤温度冬季低于对照,而夏季则有相反趋势,清理使得林床土壤湿度变化幅度加大,而且秋季和春季较对照低,而夏季偏高;林床清理使得表层土壤容重要比对照未清理样地高53%(p<0.05),土壤非毛管孔隙度比未处理样地低49.5%(p<0.001),毛管孔隙度较对照未清理降低约15%(p<0.001)。林床清理导致林下生物质资源所储藏的碳非呼吸性释放约175.0mo·lm-2,当考虑到林床清理导致的土壤呼吸的降低作用时,所测定的2a内土壤净碳支出由175.0mol·m-2降低至137.4mol·m-2。林床清理措施增加生物质资源利用和其所导致的土壤呼吸释放减少,能够减少非再生资源利用导致的碳释放压力。但仍然需要注意到林床清理使得土壤物理结构发生改变,可能不利于落叶松的生长和落叶松林生态系统的稳定。

移栽自不同纬度的兴安落叶松(Larix gmelinii Rupr.)的树干液流特征

将4个纬度上（大兴安岭塔河、大兴安岭松岭、黑河孙吴、伊春带岭）8年生的兴安落叶松（Larix gmelinii Rupr．）幼树移栽到其分布区的南缘构成4个实验处理，以探索树木水分关系的时空变化格局及其影响因子。采用基于热平衡方法的包裹式茎流计和环境因子自动测定系统同步测定移栽自4个纬度的兴安落叶松的树干液流及其相应的环境因子。研究结果表明：兴安落叶松的树干液流密度基本上呈现单峰曲线日变化格局，而日最大液流出现的时间随生长季节和实验处理不同而略有变化。移栽自4个纬度的兴安落叶松的平均单位边材面积液流通量在展叶前、中和后期分别为26．24—54．45g·cm^-2·d^-1、114．33—355．39g·cm^-2·d^-1和58．32—304．03g·cm^-2·d^-1。展叶期间落叶松的日耗水量与距地面10cm处树干直径呈显著的正相关关系；单位边材面积液流通量与针叶长度呈显著的正相关关系。影响树干液流密度的环境因子随生长阶段和实验处理而变化，主要包括太阳辐射、水蒸气压亏缺、相对湿度、气温和风速，其中太阳辐射通常是影响树干液流密度的关键因子。

大兴安岭北部兴安落叶松(Larix gmelinii)林下穿透雨空间分布特征

森林冠层对降雨的水量和水质再分配是生态水文学研究的热点问题之一。为了研究兴安落叶松林下穿透雨的空间分布规律,探究森林冠层结构对穿透雨影响的生态机制,利用在兴安落叶松林下布设38个雨量筒,测定19场不同降雨事件的穿透雨数据(2013年7—8月),通过统计学方法分析冠层结构各因子与穿透雨的空间变异性规律,结果表明:观测期间,兴安落叶松林穿透雨量为148.3 mm,占同期大气降雨量的80.62%,穿透雨率随着降雨量的增加呈增加趋势;兴安落叶松林下穿透雨具有较大空间异质性,其变异程度随降雨量的增加而减小,以对数方程拟合较好(P<0.01);冠层结构特征是影响穿透雨空间变异的重要因素,冠层复杂程度与穿透雨量呈负相关关系(P<0.01);距树干距离、冠层厚度、叶面积指数等因素均可影响穿透雨的空间分布,以距树干距离影响最大,其与穿透雨率呈正相关关系(P<0.01),而冠层厚度、叶面积指数则均与穿透雨率呈负相关关系(P<0.01),但拟合效果不佳;从影响穿透雨的生态学机制来考虑,在冠层结构特征因子中,冠层厚度是决定穿透雨空间分布的最主要因素。

兴安落叶松(Larix gmelinii)光合能力及相关因子的种源差异

为认识我国北方森林的优势树种——兴安落叶松（Larix gmelinii Rupr．）光合作用对环境变化的响应和适应特征，在其自然分布区内选择地理和气候差异显著的6个种源，采集种子并播植于其分布区南界的均一立地条件下26a后，测定针叶的光合能力及其相关因子，比较种源间差异及其随月份和冠层位置的变化。结果表明：最大净光合速率（Pmax）、表观光量子效率（AQY）、比叶重（LMA）和单位叶面积氮含量（虬）的种源差异显著（P〈0．05），变化幅度分别为6．10～8．78μmolCO2·m^-2·s^-1、0．0325—0．0427μmolCO2·μmol^-1 photons、85．1～114．3g·m^-2和1．72～2．26g·m^-2。但是光补偿点（LCP）、光饱和点（LSP）、暗呼吸速率（Rd）和单位面积叶绿素含量（Chla）的种源差异不显著，平均值分别为61．2μmolphotons·m^-2·s^-1、1093txmolphotons·m^-2·s^-1、2．34txmolCO2·m^-2·s^-1和0．12g·m^-2。Pmax、Chla、No和LMA两两之间均呈极显著正相关（p〈0．001）。随树冠从下往上升高，Pmax、LCP、Na和LMA呈逐渐增高的趋势，这种垂直变化格局受种源的显著影响。除AQY之外，种源对光合能力及其相关因子的月份变化格局没有显著影响，多表现为7月低-8月高-9月低的变化格局。研究展示的兴安落叶松针叶的光合能力及其一些相关因子的种源间差异可能是其光合机构对种源地环境条件长期生理适应的结果。

大兴安岭兴安落叶松(Larix gmelinii)天然林分级木转换特征

通过调查样地,作树干解析,分析了不同结构兴安落叶松天然林分级木(优势木、平均木和被压木)转换特征。研究表明:(1)不同结构的兴安落叶松天然林分级木转换年龄、方向和转换率均不同。兴安落叶松分级木转换率29.4%。分级木中,优势木、平均木和被压木转换率分别35.3%、41.2%、11.8%。分级木转换中,优势木与平均木相互转换比例较高,优势木转平均木占83.3%,平均木转优势木占85.7%;优势木向被压木转换比例仅为16.7%;被压木不能转换成优势木,只能转换成平均木,被压木中无转换占88.2%,在森林经营和抚育采伐中应考虑伐除这些被压木。(2)在林分年龄36～65a范围内,随着林分年龄增大,其转换率呈增加趋势。林分年龄30～39a、50～59a和60～69a时,其转换率分别0、33.3%和46.7%。(3)随着林分密度增加,分级木转换率呈增高趋势。当林分密度小于2500株.hm-2时,主要于优势木与平均木间转换。当林分密度大于2500株.hm-2时,才出现其它分级木与被压木相互转换现象。(4)不同林型分级木转换率和转换方向不同。草类-落叶松和杜香-落叶松林分级木转换率分别50%和9.5%。(5)不同水平格局林分分级木转换率不同。聚集分布和随机分布时,其转换率分别61.1%和13.3%。

大兴安岭次生林区不同龄级落叶松(Larix gmelinii)生态位特征和竞争关系

生态位能够反映物种在群落中的功能地位,通过生态位可以定量地研究种内、种间、生境三者之间的相互关系。以大兴安岭次生林区优势种群落叶松(Larix gmelinii)为研究对象,运用Levins公式、Pianka指数和Hegyi单木竞争指数模型分析了该优势种的生态位特征、生态位宽度与重叠度以及重叠程度与竞争作用之间的关系。研究结果表明:随落叶松个体的发育其生态位呈先增大后减小的规律性变化;生态位宽度较大的落叶松个体间重叠程度往往也较高,生态位宽度与重叠度呈显著的线性正相关;落叶松个体间的生态位重叠程度与彼此之间的竞争作用无明显相关性、种群内存在互利性生态位重叠现象;生物个体间的竞争作用与研究尺度有关。

Segmented taper equations with crown ratio and stand density for Dahurian Larch (Larix gmelinii) in Northeastern China

Segmented taper equation was selected to model stem profile of Dahurian larch （Larix gmelinii Rupr.）. The data were based on stem analysis of 74 trees from Dailing Forest Bureau in Heilongjiang Province, Northeastern China. Two taper equations with crown ratio and stand basal area were derived from the Max and Burkhart’s （1976） taper equation. Three taper equations were evaluated： （1） the original equation, （2） the original equation with crown ratio, and （3） the original equation with basal area. SAS NLIN and SYSNLIN procedures were used to fit taper equations. Fit statistics and cross-validation were used to evaluate the accuracy and precision of these models. Parameter estimates showed that the original equation with inclusion of crown ratio and basal area variables provided significantly different parameter estimates with lower standard errors. Overall fit statistics indicated that the root mean square error （RMSE） for diameter outside and inside bark decreased respectively by 10% and 7% in the original model with crown ratio and by 12% and 7.2% in the original model with basal area. Cross-validation further confirmed that the original equation with inclusion of crown ratio and basal area variables provided more accurate predictions at the lower section （relative heights, 10%） and upper section （relative heights, 50%） for both outside and inside bark diameters.

Dynamic feature of flavonoids content in different organs of larch （Larix gmelinii）

Flavonoids in plants is very important in its ecological role and economicvalue. The dynamic features of flavonoids content in different organs of larch (Larix gmelinii) atdifferent light and temperature conditions were investigated in this study. Results showed that theorder of flavonoids content in different organs from high to low was 7.78% (stem bark) > 2.79%(leaves) > 1.72% (branches) > 1.19% (stem xylem)and different organs had a great seasonal variationin flavonoids content, but the change of flavonoids content at different temperature was not obviousin different organs., The content of flavonoids in barck had, a positive correlation withtemperature (R^2=0.75), but that in other organs had slight variation with the change oftemperatures. For all the tested organs, the flavonoids content in summer and autumn wasapproximately 3-4 times higher than in spring and winter. This is attributed to the great stressfrom environmental physical variables such as UV radiation, high temperature that induce theaccumulation of flavonoids. The flavonoid content of sun leaves was evidently higher than that ofshade leaves, and leaves at upper part of canopy had a higher flavonoids content compared with thatat other parts. This result indicates that sun radiation could improve flavonoids production inleaves (R^2=0.76). The flavonoids may actively evolve in plant defenses to environmental stress,protecting larch from the damage of high temperature and radiation, and its main function isdifferent in different organs.

Spatial heterogeneity of soil respiration in a Larix gmelinii forest and the response to prescribed fire in the Greater Xing0an Mountains,China

This study was conducted in a fire-prone region in the Greater Xing＇an Mountains, the primary forested area of northeastern China. We measured soil respiration and the affecting soil factors, i.e., soil microbial biomass and soil moisture, within an experimental plot of Larix gmelinii Rupr. A low-intensity, prescribed fire was applied as the treatment. Traditional descriptive statistics and geostatistics were used to analyze the spatial heterogeneity of soil respiration and the response of respiration to fire disturbance. Coefficients of variation （CVs） for pre-fire and post-fire soil respiration were 23.4 and 32.0 %, respec- tively. CVs for post-fire soil respiration increased signifi- cantly, with a moderate variation of all CVs. Soil respiration pre-fire was significantly correlated with soil microbial biomass carbon, biomass nitrogen, and soil moisture （W）; post-fire soil respiration was not correlated with these factors. From the geostatistical analyses, the Co ＋ C （sill） for post-fire soil respiration increased sig- nificantly, indicating that the post-fire spatial heterogeneity of soil respiration increased significantly. The nugget effect （nc） of soil respiration and the affecting factors pre-fire and post-fire disturbance were in the range of 12.5-50 %, with strong spatial autocorrelation. Fire disturbance changed the components of spatial heterogeneity, and the proportion of functional heterogeneity increased significantly post-fire. The ranges （a） for pre-fire and post-fire soil respiration were 81.0 and 68.2 m, respectively. The homogeneity of the distribution of post-fire soil respiration decreased and the spatial heterogeneity increased, thus the range for post- fire soil respiration decreased significantly. The fractal dimension （D） for soil respiration increased post-fire, the spatial heterogeneity of soil respiration affected by random components increased, indicating that the change in spatial heterogeneity of post-fire soil respiration should be con- sidered within the scale of the forest stand. Following Kriging interpolation, the increase in the patchiness of post-fire soil respiration was illustrated using a contour map. Based on these preliminary results, the change in the spatial heterogeneity of post-fire soil respiration was likely caused by changes in the distribution of soil moisture and microbial activity within the experimental plot at the scale of the forest stand.

Separation and purification of Arabinogalactan obtained from Larix gmelinii by macroporous resin adsorption

Arabinogalactan （AG） obtained from Larix gmelinii R. waS purified with the method of macroporous resin adsorption. Effects of various parameters on the adsorption, including adsorption time and temperature, the concentration and the dosage of raw AG the reused numbers of resin, were investigated. The effect of purification was tested through the removal rate of impurity and the contents of AG and impurity. The optimal condition was determined as follows： adsorbed at 30℃ for 2 h with the concentration of raw AG 〈0.1 g·mL^-1 and its dosage 〈 7 mL, the dose of resin was 3 g and reused for 4 times. On the basis of these, macroporous resin column was used for AG purification. The result showed that the AG yield could reach 68.28% with sugar content of 95.02%. The analysis of IR and UV showed that the effect of macroporous resin characteristics on the purification of AG was significant. The obtained product had the same functional groups with standard sample.

Reflectance features of water stressed Larix gmelinii needles

In recent years, Xing＇an larch （Larix gmelinii） has been seriously infected by pests and drought. In order to improve the accuracy of monitoring the damage to larch by remote sensing （RS） and to predict the health of the larch, We studied fire reflectance features of larch needles under different water conditions at the needle level by using the LIBERTY （Leaf Incorporating Biochemistry Exhibiting Reflectance and Transmittance Yields） model. Before applying the LIBERTY model, we recalibrated it for the needles of L. gmelinii based on ten field-measured spectral curves. After recalibration, LIBERTY can accurately model the needle reflectance spectra of L. gmelinii. Based on the recalibrated LIBERTY model, we extracted and analyzed the sensitive bands to needle water content by simulating the needle reflectance spectra under different drought conditions. Then, we established mathematical equations between the spectral indices （MSI, NDWI, and GVMI） and needle water content. Results show that the variations of larch needle water content can significantly change the needle spectra at the near-infrared and short-wave infrared bands. The higher the water content is, the higher the absorption peak is. We believe that our study will provide the theoretical basis and an optional method to investigate the forest water stress using multi-spectral or hyper-spectral remote sensing data.

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.

Spotting ignition of larch(Larix gmelinii)fuel bed by different firebrands

Spot fire increase the difficulty of fire-fighting and threaten public safety,and therefore it is important to study ignition probabilities of fuel bed by different firebrands,in order to understand ignition mechanisms and analyze the formation of spot fires.This will provide an important basis for further study to improve the fire-fighting efficiency and reduce casualties.In this study,the ignition probabilities of larch(Larix gmelinii)fuel beds with different moisture levels and packing ratios by diffreent firebrands,including cones and twigs of different sizes,was investigated.Ignition experiments were conducted at different wind speeds generated by fans.The results show that,regardless of moisture content and packing ratio,ignition probability is zero when there is no wind.Both moisture content and wind speed significantly infuence ignition probability,while packing ratio has almost no effect.The maximum moisture content at which firebrand ignition occurred was 50%,and ignition probability increased with wind speed and decreased with moisture content.Cones have the highest ignition probability,followed by large twigs and by small twigs.Ignition probability is also affected by firebrand shapes and sizes that determine their potential heat and contact area to the fuel bed.Two empirical models were established to link ignition probability with fuel properties and wind speed.This study will help clarify the mechanism of spot ignition and reduce corresponding losses.

移栽自不同纬度的落叶松(Larix gmelinii Rupr.)林的春季土壤呼吸

以往的土壤呼吸(RS)研究大多集中于生长季,而对非生长季RS的认知甚少。常见于中高纬度地区的春季土壤冻融交替是影响陆地生态系统碳循环的关键事件,是RS年内变化格局的转折期。但是春季冻融交替期间RS的动态规律及其机理过程尚缺乏了解。研究以我国北方森林的优势类型——兴安落叶松(Larix gmelinii Rupr.)林为对象,在其自然分布区内,将地处4个纬度(处理)的8年生兴安落叶松林生态系统整体移至其分布区的南缘,以模拟气候暖化对RS及其组分的影响。在春季土壤冻融交替时期,采用红外气体分析法和根系排除法测定了移栽自不同纬度的落叶松林的RS和异养呼吸(RH)及其相关的环境因子。研究结果表明:RS与温度的耦联关系随土壤解冻进程而变化。在解冻初期和中期,RS的日进程与温度解耦联,但在土壤完全解冻后却强烈地依赖于土壤温度。从整个土壤解冻过程看,4个处理的RS和RH与土壤温度和含水量相关极显著(R2=0.569～0.743,P<0.001)。解冻的初期和中期的RS基本上来自RH组分,土壤根际呼吸(RR)到4月底才出现。RS和RH均受到实验处理、解冻时期及其交互作用的显著影响。RS和RH的平均值随着解冻的进程而增大,而且RS与RH之间的差异也随之增大。RS波动在0.50～3.30μmolCO2m-2s-1之间;而RH则波动在0.52～3.04μmolCO2m-2s-1之间。在相同气候条件下,4个处理RS有随着纬度的增加而增加的趋势,而且RS对土壤温度的响应程度也随纬度增加而增加。研究结果意味着土壤解冻期间来自纬度较高的兴安落叶松林的R对气候变暖方案的响应可能更为强烈。

兴安落叶松(Larix gmelinii)火后种子萌发影响因子

林火干扰是影响兴安落叶松林结构和功能的主要因子之一。兴安落叶松种群火后更新受多种因子的影响,并决定着该群落演替轨迹。通过在大兴安岭呼中自然保护区的火烧迹地内设置原位控制实验,利用增强回归树分析方法,量化研究了落叶松火后恢复初期不同影响因子(温度、有机质层厚度、覆盖度等)对种子萌发的相对重要性。研究结果表明:落叶松火后种子萌发的最主要影响因子为温度,第二影响因子为种源,第三影响因子为草本覆盖度,分别解释了幼苗数量变异的28.51%、22.40%、20.66%;各影响因子的相对重要性在不同地形条件下有明显差异:温度在山坡顶部和阳坡底部占有重要影响,种源在阳坡中部和阴坡中部最为重要,土壤含水量在阴坡底部占有重要地位。同时,去除土壤表面有机质可以显著提高种子萌发数量,去除地面杂草则会使种子萌发数量降低。从研究结果可知,落叶松火后种子萌发在不同地形(环境条件)下的限制因子不同,人工辅助需因地制宜采取相应措施,才能更有效地促进种子萌发与森林恢复。

不同主伐方式对兴安落叶松(Larix gmelinii)根际土壤理化性质及微生物群落的影响

对内蒙古根河大兴安岭林区1987年(恢复后期)、2013年(恢复前期)的皆伐与渐伐样地以及未采伐对照样地兴安落叶松的根际土壤理化性质、微生物群落结构和多样性进行了分析,旨在揭示不同主伐方式对兴安落叶松根际土壤理化性质以及微生物群落的影响。结果表明,主伐后兴安落叶松根际土壤的理化性质以及微生物群落的变化特征与非根际土壤存在区别,且不同主伐方式在不同恢复时期会对兴安落叶松根际土壤理化性质以及微生物群落产生不同的影响:(1)根际与非根际土壤微生物群落中真菌均比细菌更容易受到土壤理化性质的影响,但是单一种理化性质的改变对根际与非根际土壤微生物群落均不能造成显著影响。(2)相较于未采伐对照样地,皆伐样地恢复前期兴安落叶松根际土壤理化性质、微生物群落结构和多样性没有显著变化。皆伐样地恢复后期,兴安落叶松根际土壤理化性质(总碳、总氮、速效氮、pH)发生了显著变化,导致了微生物量碳氮、真菌磷脂脂肪酸(PLFA)含量显著降低、细菌/真菌显著升高,辛普森多样性指数显著降低。(3)渐伐样地恢复前期兴安落叶松根际土壤总碳、总氮、速效氮含量以及含水量均显著降低,总钾、速效磷含量显著上升,根际土壤微生物量碳含量显著降低。恢复后期,兴安落叶松根际土壤总磷含量显著升高,根际土壤微生物量碳的含量已恢复到渐伐前水平。渐伐干扰对根际土壤各微生物类群PLFA含量、微生物群落结构以及多样性没有显著影响。

重度火烧迹地兴安落叶松(Larix gmelinii)根际土壤真菌群落研究

为探究内蒙古根河大兴安岭林区重度火烧迹地不同生长状态的兴安落叶松根际土壤真菌群落特征,选取火烧枯立木(BDW)、火烧存活木(BSW)、未火烧对照木(CK),通过磷脂脂肪酸方法分析根际土壤真菌群落生物量变化,利用高通量测序技术对根际土壤真菌群落组成与功能进行分析,探讨影响根际土壤真菌群落的主要环境因子。结果表明:(1)相较于未火烧对照木,火烧枯立木与火烧存活木根际土壤真菌群落磷脂脂肪酸含量显著降低,真菌群落α多样性显著降低。β多样性分析与群落相似性分析结果显示,火烧枯立木、火烧存活木、未火烧对照木根际土壤真菌群落组成存在显著差异。(2)相较于未火烧对照木,火烧枯立木与火烧存活木根际土壤中担子菌门(Basidiomycota)真菌相对丰度显著下降,子囊菌门(Ascomycota)真菌相对丰度显著升高。子囊菌门(Ascomycota)内,火烧枯立木根际土壤中内生真菌相对丰度显著高于火烧存活木与未火烧对照木,而火烧存活木根际土壤中腐生⁃外生菌根复合型真菌相对丰度显著高于火烧枯立木与未火烧对照木。(3)根际土壤总磷、总钾含量是影响重度火烧迹地兴安落叶松根际土壤真菌群落优势菌门由担子菌门(Basidiomycota)转变为子囊菌门(Ascomycota)的主要环境因子,而根际土壤总碳、总氮、总磷含量则是造成火烧枯立木与火烧存活木根际土壤真菌群落组成与功能差异的主要环境因子。本研究有助于了解大兴安岭林区土壤真菌群落结构,对真菌群落多样性的维持与管理具有参考价值。